GLSL Specification 1.50.11

8/12/2019 GLSL Specification 1.50.11

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The OpenGLShading Language

Language Version: 1.50

Document Revision: 11

04-Dec-2009

John Kessenich

Version 1.1 Authors: John Kessenich, Dave Baldwin, Randi Rost


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Copyright (c) 2008-2009 The Khronos Group Inc. All Rights Reserve.

This speci!ic"tion is protecte #y copyright l"$s "n cont"ins %"teri"l propriet"ry to the Khronos Group&Inc. It or "ny co%ponents %"y not #e reprouce& repu#lishe& istri#ute& tr"ns%itte& ispl"yero"c"st or other$ise e'ploite in "ny %"nner $ithout the e'press prior $ritten per%ission o! KhronosGroup. ou %"y use this speci!ic"tion !or i%ple%enting the !unction"lity therein& $ithout "ltering orre%oving "ny tr"e%"r& copyright or other notice !ro% the speci!ic"tion& #ut the receipt or possession o!this speci!ic"tion oes not convey "ny rights to reprouce& isclose& or istri#ute its contents& or to%"nu!"cture& use& or sell "nything th"t it %"y escri#e& in $hole or in p"rt.

Khronos Group gr"nts e'press per%ission to "ny current *ro%oter& Contri#utor or Aopter %e%#er o!Khronos to copy "n reistri#ute +,/II1/ versions o! this speci!ic"tion in "ny !"shion& provie th"t, CARG1 is %"e !or the speci!ic"tion "n the l"test "v"il"#le up"te o! the speci!ic"tion !or "nyversion o! the A*I is use $henever possi#le. 3uch istri#ute speci!ic"tion %"y #e re-!or%"tte A34,G A3 the contents o! the speci!ic"tion "re not ch"nge in "ny $"y. The speci!ic"tion %"y #eincorpor"te into " prouct th"t is sol "s long "s such prouct inclues signi!ic"nt inepenent $orevelope #y the seller. A lin to the current version o! this speci!ic"tion on the Khronos Group $e#-siteshoul #e inclue $henever possi#le $ith speci!ic"tion istri#utions.

Khronos Group %"es no& "n e'pressly iscl"i%s "ny& represent"tions or $"rr"nties& e'press ori%plie& reg"ring this speci!ic"tion& incluing& $ithout li%it"tion& "ny i%plie $"rr"nties o! %erch"nt"#ilityor !itness !or " p"rticul"r purpose or non-in!ringe%ent o! "ny intellectu"l property. Khronos Group %"es

no& "n e'pressly iscl"i%s "ny& $"rr"nties& e'press or i%plie& reg"ring the correctness& "ccur"cy&co%pleteness& ti%eliness& "n reli"#ility o! the speci!ic"tion. +ner no circu%st"nces $ill the KhronosGroup& or "ny o! its *ro%oters& Contri#utors or e%#ers or their respective p"rtners& o!!icers& irectors&e%ployees& "gents or represent"tives #e li"#le !or "ny "%"ges& $hether irect& inirect& speci"l orconse5uenti"l "%"ges !or lost revenues& lost pro!its& or other$ise& "rising !ro% or in connection $iththese %"teri"ls.

Khronos& penK/1& penKG3& pen6G& penA7& pen34 13 "n pen "re tr"e%"rs o!the Khronos Group Inc. C44A/A is " tr"e%"r o! 3ony Co%puter 1ntert"in%ent Inc. use #yper%ission #y Khronos. penG4 "n pen4 "re registere tr"e%"rs "n the penG4 13 logo is "tr"e%"r o! 3ilicon Gr"phics Inc. use #y per%ission #y Khronos. All other prouct n"%es& tr"e%"rs&"nor co%p"ny n"%es "re use solely !or ienti!ic"tion "n #elong to their respective o$ners.

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3 Built;in Varia6les......................................................................................................................#93.1 Verte and /eometr( 'hader 'ecial Varia6les................................................................ #9

3.1.1 !omati6ilit( 2ro"ile Verte and /eometr( 'hader 'ecial Varia6les..................... 31

3. )ragment 'hader 'ecial Varia6les................................................................................... 33.% !omati6ilit( 2ro"ile Verte 'hader Built;In Inuts......................................................... 3&3.& Built;In !onstants.............................................................................................................. 3&

3.&.1 !omati6ilit( 2ro"ile Built;In !onstants....................................................................3$3.$ Built;In 5ni"orm 'tate....................................................................................................... 3$

3.$.1 !omati6ilit( 2ro"ile 'tate......................................................................................... 3$3.# !omati6ilit( 2ro"ile Verte and )ragment Inter"ace........................................................34

4 Built;in )unctions..................................................................................................................... 414.1 Angle and -rigonometr( )unctions....................................................................................44. +onential )unctions........................................................................................................4%4.% !ommon )unctions............................................................................................................ 4&

4.& /eometric )unctions.......................................................................................................... 434.$ 8atri )unctions................................................................................................................ 494.# Vector Relational )unctions...............................................................................................974.3 -eture 0ooku )unctions................................................................................................. 914.4 )ragment 2rocessing )unctions........................................................................................1714.9


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1 Introduction

1.2 Changes

1.2.1 Changes from revision 9 of version 1.

!lari"( that discard control "low eits the shader.

+lain how to redeclaregl_Texoor!"#.

Remove accidental inclusion o" textureGradOffset on samplerCubeSadow.

!lari"( it is generall( an error to redeclare varia6les, including 6uilt;ins.

1.2.2 Changes from revision ! of version 1.

2ut gl>8a-eture5nits and gl>8a-eture!oords into the comati6ilit( ro"ile. It was an

oversight to not have them there in the revious release.

!hange ARB>comati6ilit( etension to comati6ilit( ro"ile.

'mall clari"(ing comments o" eisting seci"ication.

Add new minimum maimums "or gl>8aVerte*utut!omonents,

gl>8a/eometr(Inut!omonents, gl>8a/eometr(*utut!omonents, and

gl>8a)ragmentInut!omonents, rather than rel(ing on gl>8aVar(ing!omonents. Also,

corrected gl>8aVar(ing!omonents to 6e #7 instead o" #&.

1.2." Changes from revision of version 1.

!omleted "ull udate to grammar section. -ested sec eamles against it:

add multi;samler samler t(es

add unsi@ed arra(s "or 6lock mem6ers

allow artial =uali"ication o" 6lock mem6ers

add assignments within the la(out =uali"ier id list

allow instances names on 6locks, no arra(, unsi@ed arra(, and arra(

Brought ARB>comati6ilit( u to "ull 1.$ "unctionalit(.

!orrected A2I trans"orm"eed6ack eamle in section &.%.3.

!lari"( that when redeclaring 6uilt;ins invariant, "lat, etc.C that 6lock instance names are not used

!lari"( that invariant can 6e used on outut varia6les that are then inut into a su6se=uent shader

stage and 6oth the inut and outut declarations o" that varia6le must 6e declared invariant or it is a

link error.

1.2.# Changes from revision # of version 1.

gl>2rimitiveID comes "rom the rovoking verte, while gl>0a(er comes "rom some verte.

Re=uire etension E/0>ARB>comati6ilit( : ena6leF to use ARB>comati6ilit( "eatures.

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1 Introduction

5dated grammar "or assignments in la(out =uali"iers and new teture ke(words.

0ots o" editorial changes.

1.2. Summar$ of %unctionalit$ differences from version 1.#

!reated ro"iles. -urned the comati6ilit( etension into the comati6ilit( ro"ile.

5date geometr( shader la(outs: the( must 6e declared, telling the s(stem the rimitive inut and

outut t(es and maimum num6er o" vertices.

Added geometr( shader constants.

!hangedgl_$ragoor! =uali"iers to use the la!out" mechanism instead.

8ade version 6e 1$7, 1.$7, etc.

Added geometr( shaders. -his includes targeting la(ers in )B* rendering.

Addedgl_%rimitive&D as an inut to "ragment shaders.

Added determinantC 6uilt;in.

Broaden arra( usage to include verte shader inuts verte inC.

Broaden structure usage to include "ragment and geometr( inuts and verte and geometr( oututs.

Broadened inter"ace 6locks "rom ?ust uni"orms to in and out inter"aces as well.

Addedgl_$ragoor!=uali"iers origin$upper$left, and pixel$center$integer to modi"( the values

returned 6(gl_$ragoor! and have no a""ect on an( other asect o" the ieline or languageC.

Removed the a6ilit( to have statements 6e"ore the "irst case in a switch.

Added suort "or multi;samle tetures through sampler%&'S andsampler%&'SArra! suort

in texel(etcC and textureSi)eC.

Derecated gl>8aVar(ing!omonentsG

1." Overvie&

-his document descri6es T'e ()en*L +'a!ing Language, version 1.50.

Indeendent comilation units written in this language are calleds'a!ers. A)rogramis a comlete set o"

shaders that are comiled and linked together. -he aim o" this document is to thoroughl( seci"( the

rogramming language. -he *en/0 /rahics '(stem 'eci"ication will seci"( the *en/0 entr(

oints used to maniulate and communicate with rograms and shaders.

1.# 'rror (andling

!omilers, in general, accet rograms that are ill;"ormed, due to the imossi6ilit( o" detecting all ill;

"ormed rograms. 2orta6ilit( is onl( ensured "or well;"ormed rograms, which this seci"ication

descri6es. !omilers are encouraged to detect ill;"ormed rograms and issue diagnostic messages, 6ut are

not re=uired to do so "or all cases. !omilers are re=uired to return messages regarding leicall(,

grammaticall(, or semanticall( incorrect shaders.

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1 Introduction

1. T$pographical Conventions

Italic, 6old, and "ont choices have 6een used in this seci"ication rimaril( to imrove reada6ilit(. !ode

"ragments use a "ied width "ont. Identi"iers em6edded in tet are italici@ed. Ke(words em6edded in tetare 6old. *erators are called 6( their name, "ollowed 6( their s(m6ol in 6old in arentheses. -he

clari"(ing grammar "ragments in the tet use 6old "or literals and italics "or non;terminals. -he o""icial

grammar in 'ection 9 E'hading 0anguage /rammarF uses all caitals "or terminals and lower case "or

non;terminals.

1.! )eprecation

2revious versions o" the *en/0 'hading 0anguage derecated some "eatures. -hese are clearl( called

out in this seci"ication as EderecatedF. -he( are still resent in this version o" the language, 6ut are

targeted "or otential removal in a "uture version o" the shading language. -he *en/0 A2I has a

"orward comati6ilit( mode that will disallow use o" derecated "eatures. I" comiling in a mode where

use o" derecated "eatures is disallowed, their use causes comile time errors. 'ee the *en/0 /rahics

'(stem 'eci"ication "or details on what causes derecated language "eatures to 6e acceted or to returnan error.

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2 Overvie& of OpenGL Shading

-he *en/0 'hading 0anguage is actuall( several closel( related languages. -hese languages are used

to create shaders "or each o" the rogramma6le rocessors contained in the *en/0 rocessing ieline.

!urrentl(, these rocessors are the verte, geometr(, and "ragment rocessors.

5nless otherwise noted in this aer, a language "eature alies to all languages, and common usage will

re"er to these languages as a single language. -he seci"ic languages will 6e re"erred to 6( the name o"

the rocessor the( target: verte, geometr(, or "ragment.

8ost *en/0 state is not tracked or made availa6le to shaders. -(icall(, user;de"ined varia6les will 6e

used "or communicating 6etween di""erent stages o" the *en/0 ieline. owever, a small amount o"

state is still tracked and automaticall( made availa6le to shaders, and there are a "ew 6uilt;in varia6les "orinter"aces 6etween di""erent stages o" the *en/0 ieline.

2.1 *erte+ ,rocessor

-he vertex )rocessoris a rogramma6le unit that oerates on incoming vertices and their associated data.

!omilation units written in the *en/0 'hading 0anguage to run on this rocessor are called vertex

s'a!ers. Hhen a comlete set o" verte shaders are comiled and linked, the( result in a vertex s'a!er

executalethat runs on the verte rocessor.

-he verte rocessor oerates on one verte at a time. It does not relace grahics oerations that re=uire

knowledge o" several vertices at a time.

2.2 Geometr$ ,rocessor-hegeometr )rocessor is a rogramma6le unit that oerates on data "or incoming vertices "or a rimitive

assem6led a"ter verte rocessing and oututs a se=uence o" vertices "orming outut rimitives.

!omilation units written in the *en/0 'hading 0anguage to run on this rocessor are calledgeometr

s'a!ers. Hhen a comlete set o" geometr( shaders are comiled and linked, the( result in ageometr

s'a!er executale that runs on the geometr( rocessor.

A single invocation o" the geometr( shader eecuta6le on the geometr( rocessor will oerate on a

declared inut rimitive with a "ied num6er o" vertices. -his single invocation can emit a varia6le

num6er o" vertices that are assem6led into rimitives o" a declared outut rimitive t(e and assed to

su6se=uent ieline stages.

2." %ragment ,rocessor-he/ragment )rocessoris a rogramma6le unit that oerates on "ragment values and their associated

data. !omilation units written in the *en/0 'hading 0anguage to run on this rocessor are called

/ragment s'a!ers. Hhen a comlete set o" "ragment shaders are comiled and linked, the( result in a

/ragment s'a!er executalethat runs on the "ragment rocessor.

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2 Overview of OpenGL Shading

A "ragment shader cannot change a "ragments x,C osition. Access to neigh6oring "ragments is not

allowed. -he values comuted 6( the "ragment shader are ultimatel( used to udate "rame6u""er memor(

or teture memor(, deending on the current *en/0 state and the *en/0 command that caused the

"ragments to 6e generated.

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" -asics

".1 Character Set

-he source character set used "or the *en/0 shading languages is a su6set o" A'!II. It includes the

"ollowing characters:

-he letters a*), A*+, and the underscore >C.

-he num6ers-*.

-he s(m6ols eriod .C, lus /C, dash *C, slash 0C, asterisk C, ercent 2C, angled 6rackets 3and

4C, s=uare 6rackets 5and 6 C, arentheses "and C, 6races 7and 8C, caret 9C, vertical 6ar :C,

amersand ;C, tilde C, colon ?C, semicolon @C, comma ,C, and=uestion mark C.

-he num6er sign #C "or rerocessor use.

Hhite sace: the sace character, hori@ontal ta6, vertical ta6, "orm "eed, carriage;return, and line;

"eed.

0ines are relevant "or comiler diagnostic messages and the rerocessor. -he( are terminated 6(

carriage;return or line;"eed. I" 6oth are used together, it will count as onl( a single line termination. )or

the remainder o" this document, an( o" these com6inations is siml( re"erred to as a new;line. -here is no

line continuation character.

In general, the languages use o" this character set is case sensitive.

-here are no character or string data t(es, so no =uoting characters are included.

-here is no end;o";"ile character.

".2 Source Strings

-he source "or a single shader is an arra( o" strings o" characters "rom the character set. A single shader

is made "rom the concatenation o" these strings. +ach string can contain multile lines, searated 6( new;

lines.


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3 Basics

"." ,reprocessor

-here is a rerocessor that rocesses the source strings as art o" the comilation rocess.

-he comlete list o" rerocessor directives is as "ollows.

#

#define

#undef

#if

#ifdef

#ifndef

#else

#elif

#endif

#error

#pragma

#extension

#version

#line

-he "ollowing oerators are also availa6le

defined

##

+ach num6er sign #C can 6e receded in its line onl( 6( saces or hori@ontal ta6s. It ma( also 6e

"ollowed 6( saces and hori@ontal ta6s, receding the directive. +ach directive is terminated 6( a new;

line. 2rerocessing does not change the num6er or relative location o" new;lines in a source string.

-he num6er sign #C on a line 6( itsel" is ignored. An( directive not listed a6ove will cause a diagnostic

message and make the imlementation treat the shader as ill;"ormed.

#defineand #undef"unctionalit( are de"ined as is standard "or ! rerocessors "or macro de"initions

6oth with and without macro arameters.

-he "ollowing rede"ined macros are availa6le

__LINE__

__FILE__

__VERSION__

__L&__will su6stitute a decimal integer constant that is one more than the num6er o" receding new;lines in the current source string.

__$&L__will su6stitute a decimal integer constant that sa(s which source string num6er is currentl(

6eing rocessed.


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3 Basics

__VR+&(__will su6stitute a decimal integer re"lecting the version num6er o" the *en/0 shading

language. -he version o" the shading language descri6ed in this document will have__VR+&(__

su6stitute the decimal integer 1$7.

All macro names containing two consecutive underscores $$ C are reserved "or "uture use as rede"ined

macro names. All macro names re"ied with E/0>F E/0F "ollowed 6( a single underscoreC are also

reserved.

#if, #ifdef, #ifndef, #else, #elif, and#endifare de"ined to oerate as is standard "or ! rerocessors.

+ressions "ollowing #ifand #elifare "urther restricted to eressions oerating on literal integer

constants, lus identi"iers consumed 6( the definedoerator. It is an error to use #if or #elif on

eressions containing unde"ined macro names, other than as arguments to the defined oerator.

!haracter constants are not suorted. -he oerators availa6le are as "ollows.

,recedence Operator class Operators ssociativit$

1 highestC arenthetical grouing C


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3 Basics

2rerocessor eressions will 6e evaluated according to the 6ehavior o" the host rocessor, not the

rocessor targeted 6( the shader.

#error will cause the imlementation to ut a diagnostic message into the shader o6?ects in"ormation log

see section #.1.17 'hader and 2rogram ueries in the *en/0 /rahics '(stem 'eci"ication "or how to

access a shader o6?ects in"ormation logC. -he message will 6e the tokens "ollowing the #errordirective,

u to the "irst new;line. -he imlementation must then consider the shader to 6e ill;"ormed.

#pragmaallows imlementation deendent comiler control. -okens "ollowing #pragmaare not su6?ect

to rerocessor macro eansion. I" an imlementation does not recogni@e the tokens "ollowing

#pragma, then it will ignore that ragma. -he "ollowing ragmas are de"ined as art o" the language.

#pragma ST!L

-he S&GDragma is used to reserve ragmas "or use 6( "uture revisions o" this language.


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3 Basics

I" the otional)ro/ile argument is rovided, it must 6e the name o" an *en/0 ro"ile. !urrentl(, there

are two choices:

%ore

%ompati$ilit&

I" no)ro/ile argument is rovided, the de"ault is core. 5nless otherwise seci"ied, this seci"ication is

documenting the core ro"ile, and ever(thing seci"ied "or the core ro"ile is also availa6le in the

comati6ilit( ro"ile. )eatures seci"ied as 6elonging seci"icall( to the comati6ilit( ro"ile are not

availa6le in the core ro"ile.

-here is a 6uilt;in macro de"inition "or each ro"ile the imlementation suorts. All imlementations

rovide the "ollowing macro:

#define !L_%ore_profile '

Imlementations roviding the comati6ilit( ro"ile rovide the "ollowing macro:

#define !L_%ompati$ilit&_profile '

-he #versiondirective must occur in a shader 6e"ore an(thing else, ecet "or comments and white sace.

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3 Basics

B( de"ault, comilers o" this language must issue comile time s(ntactic, grammatical, and semantic

errors "or shaders that do not con"orm to this seci"ication. An( etended 6ehavior must "irst 6e ena6led.

Directives to control the 6ehavior o" the comiler with resect to etensions are declared with the

#extensiondirective

#extension extension_name:behavior

#extension all :behavior

where extension_nameis the name o" an etension. +tension names are not documented in this

seci"ication. -he token allmeans the 6ehavior alies to all etensions suorted 6( the comiler. -he

e'avior can 6e one o" the "ollowing

behavior 'ffect

re/uire Behave as seci"ied 6( the etension extension_name.

/ive an error on the #extension i" the etension extension_name is notsuorted, or i" allis seci"ied.

enable Behave as seci"ied 6( the etension extension_name.

Harn on the #extensioni" the etension extension_nameis not suorted.

/ive an error on the #extension i" allis seci"ied.

&arn Behave as seci"ied 6( the etension extension_name, ecet issue warningson an( detecta6le use o" that etension, unless such use is suorted 6( otherena6led or re=uired etensions.

I" all is seci"ied, then warn on all detecta6le uses o" an( etension used.

Harn on the #extensioni" the etension extension_nameis not suorted.

disable Behave including issuing errors and warningsC as i" the etensionextension_nameis not art o" the language de"inition.

I" all is seci"ied, then 6ehavior must revert 6ack to that o" the non;etendedcore version o" the language 6eing comiled to.

Harn on the #extension i" the etension extension_nameis not suorted.

-he extensiondirective is a simle, low;level mechanism to set the 6ehavior "or each etension. It does

not de"ine olicies such as which com6inations are aroriate, those must 6e de"ined elsewhere. *rder

o" directives matters in setting the 6ehavior "or each etension: Directives that occur later override those

seen earlier. -he allvariant sets the 6ehavior "or all etensions, overriding all reviousl( issued

extension directives, 6ut onl( "or the e'aviorswarnand disable.

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3 Basics

-he initial state o" the comiler is as i" the directive

#extension all ( disa$le

was issued, telling the comiler that all error and warning reorting must 6e done according to thisseci"ication, ignoring an( etensions.

+ach etension can de"ine its allowed granularit( o" scoe. I" nothing is said, the granularit( is a shader

that is, a single comilation unitC, and the etension directives must occur 6e"ore an( non;rerocessor

tokens. I" necessar(, the linker can en"orce granularities larger than a single comilation unit, in which

case each involved shader will have to contain the necessar( etension directive.

8acro eansion is not done on lines containing #extensionand #versiondirectives.

#linemust have, a"ter macro su6stitution, one o" the "ollowing "orms:

#line line

#line line source-string-number

where line andsource-string-numer are constant integer eressions. A"ter rocessing this directiveincluding its new;lineC, the imlementation will 6ehave as i" it is comiling at line num6er line1and

source string num6ersource-string-numer. 'u6se=uent source strings will 6e num6ered se=uentiall(,

until another #linedirective overrides that num6ering.

".# Comments

!omments are delimited 6( N and N, or 6( and a new;line. -he 6egin comment delimiters N or C are

not recogni@ed as comment delimiters inside o" a comment, hence comments cannot 6e nested. I" a

comment resides entirel( within a single line, it is treated s(ntacticall( as a single sace.


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3 Basics

". To0ens

-he language is a se=uence o" tokens. A token can 6e

to3en:

3eor!

i!enti/ier

integer-constant

/loating-constant

o)erator

@ 7 8

".! e$&ords

-he "ollowing are the ke(words in the language, and cannot 6e used "or an( other urose than that

de"ined 6( this document:

attribute const uniform var!ing

la!out

centroid flat smoot noperspective

break continue do for wile switc case default

if else

in out inout

float int void bool true false

invariant

discard return

mat% matF mat

mat%x% mat%xF mat%x

matFx% matFxF matFx

matx% matxF matx

vec% vecF vec ivec% ivecF ivec bvec% bvecF bvec

uint uvec% uvecF uvec

lowp mediump igp precision

sampler1& sampler%& samplerF& samplerCube

sampler1&Sadow sampler%&Sadow samplerCubeSadow sampler1&Arra! sampler%&Arra!

sampler1&Arra!Sadow sampler%&Arra!Sadow

isampler1& isampler%& isamplerF& isamplerCube

isampler1&Arra! isampler%&Arra!

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3 Basics

usampler1& usampler%& usamplerF& usamplerCube

usampler1&Arra! usampler%&Arra!

sampler%&Hect sampler%&HectSadow isampler%&Hect usampler%&Hect samplerIuffer isamplerIuffer usamplerIuffer

sampler%&'S isampler%&'S usampler%&'S

sampler%&'SArra! isampler%&'SArra! usampler%&'SArra!

struct

-he "ollowing are the ke(words reserved "or "uture use. 5sing them will result in an error:

common partition active

asm

class union enum t!pedef template tis packed

goto

inline noinline volatile public static extern external interface

long sort double alf fixed unsigned superp

input output

vec% vecF vec dvec% dvecF dvec fvec% fvecF fvec

samplerF&Hect

filter

image1& image%& imageF& imageCube

iimage1& iimage%& iimageF& iimageCube

uimage1& uimage%& uimageF& uimageCube

image1&Arra! image%&Arra!

iimage1&Arra! iimage%&Arra! uimage1&Arra! uimage%&Arra!

image1&Sadow image%&Sadow

image1&Arra!Sadow image%&Arra!Sadow

imageIuffer iimageIuffer uimageIuffer

si)eof cast

namespace using

row$maJor

In addition, all identi"iers containing two consecutive underscores $$C are reserved as ossi6le "uture

ke(words.

15


22/125

3 Basics

". Identifiers

Identi"iers are used "or varia6le names, "unction names, structure names, and "ield selectors "ield

selectors select comonents o" vectors and matrices similar to structure "ields, as discussed in 'ection $.$EVector !omonentsF and 'ection $.# E8atri !omonentsF C. Identi"iers have the "orm

i!enti/ier

non!igit

i!enti/ier non!igit

i!enti/ier !igit

non!igit: one o"

$ a b c d e f g i J k l m n o p K r s t u v w x ! )

A I C & L ( G M N P D ' Q O R H S T U V W X +

!igit: one o"

- 1 % F E Y Z [

Identi"iers starting with Egl>F are reserved "or use 6( *en/0, and ma( not 6e declared in a shader as

either a varia6le or a "unction. owever, as noted in the seci"ication, there are some cases where

reviousl( declared varia6les can 6e redeclared to change or add some roert(, and redeclared gl>

names are allowed to 6e redeclared in a shader.onl( "or these seci"ic uroses. 8ore generall(, it is an

error to redeclare a varia6le, including those starting Egl>F.

".3 Static 4se

'ome language rules descri6ed 6elow deend on whether something isstaticall written or used.

A shader contains astatic useo" orstatic assignmenttoC a varia6lexi", a"ter rerocessing, the shader

contains a statement that would read or writeCx, whether or not run;time "low o" control will cause that

statement to 6e eecuted.

16


23/125

# *ariables and T$pes

All varia6les and "unctions must 6e declared 6e"ore 6eing used. Varia6le and "unction names are

identi"iers.

-here are no de"ault t(es. All varia6le and "unction declarations must have a declared t(e, and

otionall( =uali"iers. A varia6le is declared 6( seci"(ing its t(e "ollowed 6( one or more names

searated 6( commas. In man( cases, a varia6le can 6e initiali@ed as art o" its declaration 6( using the

assignment oerator =C. -he grammar near the end o" this document rovides a "ull re"erence "or the

s(nta o" declaring varia6les.

5ser;de"ined t(es ma( 6e de"ined using structto aggregate a list o" eisting t(es into a single name.

-he *en/0 'hading 0anguage is t(e sa"e. -here are no imlicit conversions 6etween t(es, with theecetion that an integer value ma( aear where a "loating;oint t(e is eected, and 6e converted to a

"loating;oint value. +actl( how and when this can occur is descri6ed in 'ection &.1.17EImlicit

!onversionsF and as re"erenced 6( other sections in this seci"ication.

#.1 -asic T$pes

-he *en/0 'hading 0anguage suorts the "ollowing 6asic data t(es, groued as "ollows.

-ransarent t(es

T$pe 5eaning

void "or "unctions that do not return a value

bool a conditional t(e, taking on values o" true or "alse

int a signed integer

uint an unsigned integer

float a single "loating;oint scalar

vec% a two;comonent "loating;oint vector

vecF a three;comonent "loating;oint vector

vec a "our;comonent "loating;oint vector

bvec% a two;comonent Boolean vector

bvecF a three;comonent Boolean vector

bvec a "our;comonent Boolean vector

ivec% a two;comonent signed integer vector

ivecF a three;comonent signed integer vector

ivec a "our;comonent signed integer vector

17


24/125

4 #aria$%es and &'pes

T$pe 5eaning

uvec% a two;comonent unsigned integer vector

uvecF a three;comonent unsigned integer vectoruvec a "our;comonent unsigned integer vector

mat% a W "loating;oint matri

matF a %W% "loating;oint matri

mat a &W& "loating;oint matri

mat%x% same as a mat%

mat%xF a "loating;oint matri with columns and % rows

mat%x a "loating;oint matri with columns and & rows

matFx% a "loating;oint matri with % columns and rows

matFxF same as a matFmatFx a "loating;oint matri with % columns and & rows

matx% a "loating;oint matri with & columns and rows

matxF a "loating;oint matri with & columns and % rows

matx same as a mat

)loating 2oint 'amler -(es oa=ueC

T$pe 5eaning

sampler1& a handle "or accessing a 1D teture

sampler%& a handle "or accessing a D teture

samplerF& a handle "or accessing a %D teture

samplerCube a handle "or accessing a cu6e maed teture

sampler%&Hect a handle "or accessing a rectangular teture

sampler1&Sadow a handle "or accessing a 1D deth teture with comarison

sampler%&Sadow a handle "or accessing a D deth teture with comarison

sampler%&HectSadow a handle "or accessing a rectangular teture with comarison

sampler1&Arra! a handle "or accessing a 1D arra( teture

sampler%&Arra! a handle "or accessing a D arra( teture

sampler1&Arra!Sadow a handle "or accessing a 1D arra( deth teture with comarisonsampler%&Arra!Sadow a handle "or accessing a D arra( deth teture with comarison

samplerIuffer a handle "or accessing a 6u""er teture

sampler%&'S a handle "or accessing a D multi;samle teture

1


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T$pe 5eaning

sampler%&'SArra! a handle "or accessing a D multi;samle arra( teture

'igned Integer 'amler -(es oa=ueC

T$pe 5eaning

isampler1& a handle "or accessing an integer 1D teture

isampler%& a handle "or accessing an integer D teture

isamplerF& a handle "or accessing an integer %D teture

isamplerCube a handle "or accessing an integer cu6e maed teture

isampler%&Hect a handle "or accessing an integer D rectangular teture

isampler1&Arra! a handle "or accessing an integer 1D arra( teture

isampler%&Arra! a handle "or accessing an integer D arra( teture

isamplerIuffer a handle "or accessing an integer 6u""er teture

isampler%&'S a handle "or accessing an integer D multi;samle teture

isampler%&'SArra! a handle "or accessing an integer D multi;samle arra( teture

5nsigned Integer 'amler -(es oa=ueC

T$pe 5eaning

usampler1& a handle "or accessing an unsigned integer 1D teture

usampler%& a handle "or accessing an unsigned integer D teture

usamplerF& a handle "or accessing an unsigned integer %D teture

usamplerCube a handle "or accessing an unsigned integer cu6e maed teture

usampler%&Hect a handle "or accessing an unsigned integer rectangular teture

usampler1&Arra! a handle "or accessing an unsigned integer 1D arra( teture

usampler%&Arra! a handle "or accessing an unsigned integer D arra( teture

usamplerIuffer a handle "or accessing an unsigned integer 6u""er teture

usampler%&'S a handle "or accessing an unsigned integer D multi;samle teture

usampler%&'SArra! a handle "or accessing an unsigned integer D multi;samle teturearra(

In addition, a shader can aggregate these using arra(s and structures to 6uild more comle t(es.

-here are no ointer t(es.

1!


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#.1.1 *oid

)unctions that do not return a value must 6e declared as void. -here is no de"ault "unction return t(e.

-he ke(word voidcannot 6e used in an( other declarations ecet "or emt( "ormal or actual arameter

listsC.

#.1.2 -ooleans

-o make conditional eecution o" code easier to eress, the t(e boolis suorted. -here is no

eectation that hardware directl( suorts varia6les o" this t(e. It is a genuine Boolean t(e, holding

onl( one o" two values meaning either true or "alse. -wo ke(words trueand falsecan 6e used as literal

Boolean constants. Booleans are declared and otionall( initiali@ed as in the "ollow eamle:

$ool su%%ess ** de%lare +su%%ess, to $e a -oolean

$ool done . false ** de%lare and initiali"e +done,

-he right side o" the assignment oerator = C must 6e an eression whose t(e is bool.

+ressions used "or conditional ?ums if, for, ?, wile, do*wileC must evaluate to the t(e bool.

#.1." Integers

'igned and unsigned integer varia6les are "ull( suorted. In this document, the term integer is meant to

generall( include 6oth signed and unsigned integers. 5nsigned integers have eactl( % 6its o" recision.

'igned integers use % 6its, including a sign 6it, in twos comlement "orm. *erations resulting in

over"low or under"low will not cause an( ecetion, nor will the( saturate, rather the( will EwraF to (ield

the low;order % 6its o" the result.

Integers are declared and otionall( initiali@ed with integer eressions, as in the "ollowing eamle:

int i/ 0 . 12 ** default integer literal t&pe is int

uint 3 . 4u ** +u, esta$lis5es t5e t&pe as uint

2"


27/125


0iteral integer constants can 6e eressed in decimal 6ase 17C, octal 6ase 4C, or headecimal 6ase 1#C

as "ollows.

integer-constant :

!ecimal-constant integer-su//ixo)t

octal-constant integer-su//ixo)t

'exa!ecimal-constant integer-su//ixo)t

integer-su//ix: one o"

u T

!ecimal-constant :

nonero-!igit

!ecimal-constant !igit

octal-constant :

-

octal-constant octal-!igit

'exa!ecimal-constant :

7'exa!ecimal-!igit

7X'exa!ecimal-!igit

'exa!ecimal-constant 'exa!ecimal-!igit

!igit :

-

nonero-!igit

nonero-!igit : one o"

1 % F E Y Z [

octal-!igit? one o"

- 1 % F E Y Z

'exa!ecimal-!igit?one o"

- 1 % F E Y Z [

a b c d e f

A I C & L (


28/125


29/125


#.1. *ectors

-he *en/0 'hading 0anguage includes data t(es "or generic ;, %;, and &;comonent vectors o"

"loating;oint values, integers, or Booleans. )loating;oint vector varia6les can 6e used to store colors,

normals, ositions, teture coordinates, teture looku results and the like. Boolean vectors can 6e used

"or comonent;wise comarisons o" numeric vectors. 'ome eamles o" vector declaration are:

ve%2 tex%oord'/ tex%oord2

ve%4 position

ve%1 m&R!-8

ive%2 textureLoo3up

$ve%4 less

Initiali@ation o" vectors can 6e done with constructors, which are discussed shortl(.

#.1.! 5atrices

-he *en/0 'hading 0anguage has 6uilt;in t(es "or W, W%, W&, %W, %W%, %W&, &W, &W%, and &W&matrices o" "loating;oint num6ers. -he "irst num6er in the t(e is the num6er o" columns, the second is

the num6er o" rows. +amle matri declarations:

mat2 mat2

mat4 opt9atrix

mat1 vie:/ pro0e%tion

mat1x1 vie: ** an alternate :a& of de%laring a mat1

mat4x2 m ** a matrix :it5 4 %olumns and 2 ro:s

Initiali@ation o" matri values is done with constructors descri6ed in 'ection $.& E!onstructorsF C in

column;ma?or order.

#.1. Samplers

'amler t(es e.g., sampler%&C are e""ectivel( oa=ue handles to tetures and their "ilters. -he( are

used with the 6uilt;in teture "unctions descri6ed in 'ection 4.3 E-eture 0ooku )unctionsF C to seci"(

which teture to access and how it is to 6e "iltered. -he( can onl( 6e declared as "unction arameters or

uniformvaria6les see 'ection &.%.$ E5ni"ormF C. +cet "or arra( indeing, structure "ield selection,

and arentheses, samlers are not allowed to 6e oerands in eressions. 'amlers aggregated into arra(s

within a shader using s=uare 6rackets 5 6C can onl( 6e indeed with integral constant eressions see

'ection &.%.% E!onstant +ressionsFC. 'amlers cannot 6e treated as l;valuesG hence cannot 6e used as

out or inout "unction arameters, nor can the( 6e assigned into. As uni"orms, the( are initiali@ed onl(

with the *en/0 A2IG the( cannot 6e declared with an initiali@er in a shader. As "unction arameters,

onl( samlers ma( 6e assed to samlers o" matching t(e. -his ena6les consistenc( checking 6etween

shader teture accesses and *en/0 teture state 6e"ore a shader is run.

23


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#.1.3 Structures

5ser;de"ined t(es can 6e created 6( aggregating other alread( de"ined t(es into a structure using the

structke(word. )or eamle,

stru%t lig5t ;

float intensit&

ve%4 position

< lig5tVar

In this eamle, lig't6ecomes the name o" the new t(e, and lig'tVar6ecomes a varia6le o" t(e lig't.

-o declare varia6les o" the new t(e, use its name without the ke(word structC.

lig5t lig5tVar2

8ore "ormall(, structures are declared as "ollows. owever, the comlete correct grammar is as given in

'ection 9 E'hading 0anguage /rammarF .

struct-!e/inition :6uali/ier

o)t structname

o)t7memer-list 8!eclarators

o)t7

memer-list :

memer-!eclaration7

memer-!eclaration memer-list7

memer-!eclaration :

asic-t)e !eclarators7

where name6ecomes the user;de"ined t(e, and can 6e used to declare varia6les to 6e o" this new t(e.

-he nameshares the same name sace as other varia6les, t(es, and "unctions. All reviousl( visi6le

varia6les, t(es, constructors, or "unctions with that name are hidden. -he otional 6uali/ieronl( alies

to an( !eclarators, and is not art o" the t(e 6eing de"ined "or name.

'tructures must have at least one mem6er declaration. 8em6er declarators ma( contain recision

=uali"iers, 6ut ma( not contain an( other =uali"iers. Bit "ields are not suorted. 8em6er t(es must 6e

alread( de"ined there are no "orward re"erencesC. 8em6er declarations cannot contain initiali@ers.

8em6er declarators can contain arra(s. 'uch arra(s must have a si@e seci"ied, and the si@e must 6e an

integral constant eression thats greater than @ero see 'ection &.%.% E!onstant +ressionsFC. +ach

level o" structure has its own name sace "or names given in mem6er declaratorsG such names need onl(

6e uni=ue within that name sace.

24


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Anon(mous structures are not suorted. +m6edded structure de"initions are not suorted.

stru%t S ; float f


32/125


and as an alternate wa( o" declaring a varia6le or "unction arameter.

float>7? a

It is an error to declare arra(s o" arra(s:

float a>7?>4? ** illegal

float>7? a>4? ** illegal

Arra(s can have initiali@ers "ormed "rom arra( constructors:

float a>7? . float>7?461/ 162/ 76A/ 762/ '6')

float a>7? . float>?461/ 162/ 76A/ 762/ '6') ** same t5ing

5nsi@ed arra(s can 6e elicitl( si@ed 6( an initiali@er at declaration time:

float a>7?

666

float $>? . a ** $ is expli%itl& si"e 7

float $>7? . a ** means t5e same t5ing

owever, imlicitl( si@ed arra(s cannot 6e assigned to.


33/125


#.1.16 Implicit Conversions

In some situations, an eression and its t(e will 6e imlicitl( converted to a di""erent t(e. -he

"ollowing ta6le shows all allowed imlicit conversions:

T$pe of e+pression Can be implicitl$ converted to

int

uint

float

ivec%uvec%

vec%

ivecFuvecF

vecF

ivecuvec

vec

-here are no imlicit arra( or structure conversions. )or eamle, an arra( o" intcannot 6e imlicitl(converted to an arra( o" float. -here are no imlicit conversions 6etween signed and unsigned integers.

Hhen an imlicit conversion is done, it is not a re;interretation o" the eressions 6it attern, 6ut a

conversion o" its value to an e=uivalent value in the new t(e. )or eamle, the integer value ;Ewill 6e

converted to the "loating;oint value ;E.-. Integer values having more 6its o" recision than a "loating

oint mantissa will lose recision when converted to float.

-he conversions in the ta6le a6ove are done onl( as indicated 6( other sections o" this seci"ication.

#.2 Scoping

-he scoe o" a varia6le is determined 6( where it is declared. I" it is declared outside all "unction

de"initions, it has glo6al scoe, which starts "rom where it is declared and ersists to the end o" the shader

it is declared in. I" it is declared in a wiletest or a for statement, then it is scoed to the end o" the

"ollowing su6;statement. *therwise, i" it is declared as a statement within a comound statement, it is

scoed to the end o" that comound statement. I" it is declared as a arameter in a "unction de"inition, it is

scoed until the end o" that "unction de"inition. A "unction 6od( has a scoe nested inside the "unctions

de"inition. -he ifstatements eression does not allow new varia6les to 6e declared, hence does not

"orm a new scoe.

27


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Hithin a declaration, the scoe o" a name starts immediatel( a"ter the initiali@er i" resent or immediatel(

a"ter the name 6eing declared i" not. 'everal eamles:

int x . '

;

int x . 2/ & . x ** & is initiali"ed to 2

? ** si"e un3no:n

666Color'6lengt5)666** illegal/ lengt5) un3no:n

in ve%1 Color2>2? ** si"e is 2666Color'6lengt5)666** illegal/ Color' still 5as no si"e

in ve%1 Color4>4? ** illegal/ input si"es are in%onsistent

la&outlines) in ** legal/ input si"e is 2/ mat%5ing

in ve%1 Color1>4? ** illegal/ %ontradi%ts la&out

666Color'6lengt5)666** legal/ lengt5) is 2/ Color' si"ed $& la&out)

la&outlines) in ** legal/ mat%5es ot5er la&out) de%laration

la&outtriangles) in** illegal/ does not mat%5 earlier la&out) de%laration

It is a link;time error i" not all rovided si@es si@ed inut arra(s and la(out si@eC match across all

geometr( shaders in the rogram.

)ragment shaders can have an inut la(out onl( "or redeclaring the 6uilt;in varia6legl_$ragoor! see

section 3.)ragment 'hader 'ecial Varia6lesC. -he la(out =uali"ier identi"iers "orgl_$ragoor!are

laout-6uali/ier-i!

origin$upper$left

pixel$center$integer

B( de"ault,gl_$ragoor! assumes a lower;le"t origin "or window coordinates and assumes iel centers

are located at hal";iel coordinates. )or eamle, the x, C location 7.$, 7.$C is returned "or the lower;

le"t;most iel in a window. -he origin can 6e changed 6( redeclaringgl_$ragoor! with the

origin$upper$left identi"ier, moving the origin o"gl_$ragoor! to the uer le"t o" the window, with

increasing in value toward the 6ottom o" the window. -he values returned can also 6e shi"ted 6( hal" a

iel in 6othx and6( pixel$center$integer so it aears the iels are centered at whole num6er iel

o""sets. -his moves the x,C valuereturned 6(gl_$ragoor! o" 7.$, 7.$C 6( de"ault, to 7.7, 7.7C with

pixel$center$integer. Redeclarations are done as "ollows

in ve%1 gl_FragCoord ** rede%laration t5at %5anges not5ing is allo:ed

** 8ll t5e follo:ing are allo:ed rede%laration t5at %5ange $e5avior

la&outorigin_upper_left) in ve%1 gl_FragCoord

la&outpixel_%enter_integer) in ve%1 gl_FragCoord

la&outorigin_upper_left/ pixel_%enter_integer) in ve%1 gl_FragCoord

I"gl_$ragoor! is redeclared in an( "ragment shader in a rogram, it must 6e redeclared in all the

"ragment shaders in that rogram that have a static use gl_$ragoor!. All redeclarations o"

gl_$ragoor! in all "ragment shaders in a single rogram must have the same set o" =uali"iers. Hithin

an( shader, the "irst redeclarations o"gl_$ragoor! must aear 6e"ore an( use o"gl_$ragoor!. -he

6uilt;ingl_$ragoor!is onl( redeclared in "ragment shaders, so redeclaring it in an( other shader

language will 6e illegal.

Redeclaringgl_$ragoor! with origin$upper$left andor pixel$center$integer=uali"iers onl( a""ects

gl_$ragoor!.x and gl_$ragoor!.. It has no a""ect on rasteri@ation, trans"ormation, or an( other art

o" the *en/0 ieline or language "eatures.

3!


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#.".3.2 Output La$out 7ualifiers

Verte and "ragment shaders cannot have outut la(out =uali"iers.

/eometr( shaders can have outut la(out =uali"iers onl( on the inter"ace =uali"ier out, not on an outut6lock or varia6le declaration.

-he la(out =uali"ier identi"iers "or geometr( shader oututs are

laout-6uali/ier-i!

points

line$strip

triangle$strip

max$vertices=integer-constant

*ne declaration can declare either a rimitive t(e points,line$strip, ortriangle$stripC, or

max$vertices, or 6oth. 5se max$vertices to declare the maimum num6er o" vertices this shader will

ever emit in a single eecution. )or eamle,

la&outtriangle_strip/ max_verti%es . A) out ** order does not matter

la&outmax_verti%es . A) out ** rede%laration o3a&

la&outtriangle_strip) out ** rede%laration o3a&

la&outpoints) out ** error/ %ontradi%ts triangle_strip

la&outmax_verti%es . 4A) out ** error/ %ontradi%ts A

these will esta6lish that all oututs "rom the geometr( shader are triangles and at most #7 vertices will 6e

emitted 6( the shader. It is an error "or the maimum num6er o" vertices to 6e greater than

gl$'axGeometr!OutputUertices.

All geometr( shader outut la(out declarations in a rogram must declare the same la(out and same value

"or max$vertices. -here must 6e at least one geometr( outut la(out declaration somewhere in a

rogram, 6ut not all geometr( shaders comilation unitsC are re=uired to declare it.

#.".3." 4niform -loc0 La$out 7ualifiers

0a(out =uali"iers can 6e used "or uni"orm 6locks, 6ut not "or non;6lock uni"orm declarations. -he la(out

=uali"ier identi"iers "or uni"orm 6locks are

laout-6uali/ier-i!

sared

packed

std1-

row$maJor

column$maJor


47/125


De"ault la(outs are esta6lished at glo6al scoe "or uni"orm 6locks as

la&outlaout-6uali/ier-i!-list) uniform

Hhen this is done, the revious de"ault =uali"ication is "irst inherited and then overridden as er the

override rules listed 6elow "or each =uali"ier listed in the declaration. -he result 6ecomes the new de"ault

=uali"ication scoed to su6se=uent uni"orm 6lock de"initions.

-he initial state o" comilation is as i" the "ollowing were declared:

la&outs5ared/ %olumn_ma0or) uniform

+licitl( declaring this in a shader will return de"aults 6ack to their initial state.

5ni"orm 6locks can 6e declared with otional la(out =uali"iers, and so can their individual mem6er

declarations. 'uch 6lock la(out =uali"ication is scoed onl( to the content o" the 6lock. As with glo6al

la(out declarations, 6lock la(out =uali"ication "irst inherits "rom the current de"ault =uali"ication and then

overrides it. 'imilarl(, individual mem6er la(out =uali"ication is scoed ?ust to the mem6er declaration,

and inherits "rom and overrides the 6locks =uali"ication.

-hes'are! =uali"ier overrides onl( thest!140 and)ac3e! =uali"iersG other =uali"iers are inherited. -he

comilerlinker will ensure that multile rograms and rogramma6le stages containing this de"inition

will share the same memor( la(out "or this 6lock, as long as the( also matched in their ro_ma;or andor

column_ma;or =uali"ications. -his allows use o" the same 6u""er to 6ack the same 6lock de"inition across

di""erent rograms.

-he)ac3e! =uali"ier overrides onl(st!140 ands'are!G other =uali"iers are inherited. Hhen)ac3e! is

used, no sharea6le la(out is guaranteed. -he comiler and linker can otimi@e memor( use 6ased on what

varia6les activel( get used and on other criteria. *""sets must 6e =ueried, as there is no other wa( o"

guaranteeing where and whichC varia6les reside within the 6lock. Attemts to share a acked uni"orm

6lock across rograms or stages will generall( "ail. owever, imlementations ma( aid alication

management o" acked 6locks 6( using canonical la(outs "or acked 6locks.-hest!140 =uali"ier overrides onl( the)ac3e! ands'are! =uali"iersG other =uali"iers are inherited. -he

la(out is elicitl( determined 6( this, as descri6ed in section .11.& under 'tandard 5ni"orm Block

0a(out o" the *en/0 /rahics '(stem 'eci"ication. ence, as ins'are! a6ove, the resulting la(out is

sharea6le across rograms.

0a(out =uali"iers on mem6er declarations cannot use thes'are!,)ac3e!,orst!140 =uali"iers. -hese can

onl( 6e used at glo6al scoe or on a 6lock declaration.

-he ro_ma;or =uali"ier overrides onl( the column_ma;or=uali"ierG other =uali"iers are inherited. It onl(

a""ects the la(out o" matrices. +lements within a matri row will 6e contiguous in memor(.

-he column_ma;or =uali"ier overrides onl( the ro_ma;or=uali"ierG other =uali"iers are inherited. It onl(

a""ects the la(out o" matrices. +lements within a matri column will 6e contiguous in memor(.

Hhen multile arguments are listed in a la!out declaration, the a""ect will 6e the same as i" the( were

declared one at a time, in order "rom le"t to right, each in turn inheriting "rom and overriding the result

"rom the revious =uali"ication.

41


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)or eamle

la&outro:_ma0or/ %olumn_ma0or)

results in the =uali"ication 6eing column_ma;or. *ther eamles:

la&outs5ared/ ro:_ma0or) uniform ** default is no: s5ared and ro:_ma0or

la&outstd'1A) uniform Transform ; ** la&out of t5is $lo%3 is std'1A

mat1 9' ** ro:_ma0or

la&out%olumn_ma0or) mat1 92 ** %olumn ma0or

mat4 N' ** ro:_ma0or


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-he t(e and resence o" the interolation =uali"iers and storage =uali"iers and invariant =uali"iers o"

varia6les with the same name declared in all linked shaders must match, otherwise the link command will

"ail.

#.".9.1 8edeclaring -uiltin Interpolation *ariables in the Compatibilit$ ,rofile

-he "ollowing redeclared varia6les can 6e redeclared with an interolation =uali"ier when using the

comati6ilit( ro"ile:

Verte and geometr( languages:

gl_FrontColor

gl_-a%3Color

gl_FrontSe%ondar&Color

gl_-a%3Se%ondar&Color

)ragment language:

gl_Colorgl_Se%ondar&Color

)or eamle,

in ve%1 gl_Color ** prede%lared $& t5e fragment language

flat in ve%1 gl_Color ** rede%lared $& user to $e flat

flat in ve%1 gl_FrontColor ** input to geometr& s5ader/ no +gl_in>?,

flat out ve%1 gl_FrontColor ** output from geometr& s5ader

Inut or outut instance names on 6locks are not used when redeclaring 6uilt;in varia6les.

I"gl_olor is redeclared with an interolation =uali"ier, thengl_$rontolor andgl_


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2arameter =uali"iers are discussed in more detail in 'ection #.1.1 E)unction !alling !onventionsF.

#. ,recision and ,recision 7ualifiers

2recision =uali"iers are added "or code orta6ilit( with *en/0 +', not "or "unctionalit(. -he( have the

same s(nta as in *en/0 +', as descri6ed 6elow, 6ut the( have no semantic meaning, which includes no

e""ect on the recision used to store or oerate on varia6les.

I" an etension adds in the same semantics and "unctionalit( in the *en/0 +' .7 seci"ication "or

recision =uali"iers, then the etension is allowed to reuse the ke(words 6elow "or that urose.

#..1 8ange and ,recision

'ection num6er reserved "or "uture use.

#..2 ,recision 7ualifiersAn( "loating oint or an( integer declaration can have the t(e receded 6( one o" these recision

=uali"iers:

7ualifier 5eaning

igp


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pre%ision pre%ision=ualifier t&pe

can 6e used to esta6lish a de"ault recision =uali"ier. -he t!pe"ield can 6e eitherintor float, and the

)recision-6uali/ier can 6e lowp, mediump, or igp. An( other t(es or =uali"iers will result in an error.I" t)eis float, the directive alies to non;recision;=uali"ied "loating oint t(e scalar, vector, and

matriC declarations. I" t)eis int, the directive alies to all non;recision;=uali"ied integer t(e scalar,

vector, signed, and unsignedC declarations. -his includes glo6al varia6le declarations, "unction return

declarations, "unction arameter declarations, and local varia6le declarations.


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#.!.1 The Invariant 7ualifier

-o ensure that a articular outut varia6le is invariant, it is necessar( to use the invariant=uali"ier. It can

either 6e used to =uali"( a reviousl( declared varia6le as 6eing invariant

invariant gl_@osition ** ma3e existing gl_@osition $e invariant

out ve%4 Color

invariant Color ** ma3e existing Color $e invariant

or as art o" a declaration when a varia6le is declared

invariant %entroid out ve%4 Color

-he invariant =uali"ier must aear 6e"ore an( interolation =uali"iers or storage =uali"iers when

com6ined with a declaration. *nl( varia6les outut "rom a shader including those that are then inut to a

su6se=uent shaderC can 6e candidates "or invariance. -his includes user;de"ined outut varia6les and the

6uilt;in outut varia6les. )or varia6les leaving one shader and coming into another shader, the invariantke(word has to 6e used in 6oth shaders, or a link error will result.

Inut or outut instance names on 6locks are not used when redeclaring 6uilt;in varia6les.

-he invariantke(word can 6e "ollowed 6( a comma searated list o" reviousl( declared identi"iers. All

uses o" invariantmust 6e at the glo6al scoe, and 6e"ore an( use o" the varia6les 6eing declared as

invariant.

-o guarantee invariance o" a articular outut varia6le across two rograms, the "ollowing must also 6e

true:

-he outut varia6le is declared as invariant in 6oth rograms.

-he same values must 6e inut to all shader inut varia6les consumed 6( eressions and "low control

contri6uting to the value assigned to the outut varia6le.

-he teture "ormats, teel values, and teture "iltering are set the same wa( "or an( teture "unction

calls contri6uting to the value o" the outut varia6le.

All inut values are all oerated on in the same wa(. All oerations in the consuming eressions and

an( intermediate eressions must 6e the same, with the same order o" oerands and same

associativit(, to give the same order o" evaluation. Intermediate varia6les and "unctions must 6e

declared as the same t(e with the same elicit or imlicit recision =uali"iers. An( control "low

a""ecting the outut value must 6e the same, and an( eressions consumed to determine this control

"low must also "ollow these invariance rules.

All the data "low and control "low leading to setting the invariant outut varia6le reside in a single

comilation unit.

+ssentiall(, all the data "low and control "low leading to an invariant outut must match.

Initiall(, 6( de"ault, all outut varia6les are allowed to 6e variant. -o "orce all outut varia6les to 6e

invariant, use the ragma

46


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#pragma ST!L invariantall)

6e"ore all declarations in a shader. I" this ragma is used a"ter the declaration o" an( varia6les or

"unctions, then the set o" oututs that 6ehave as invariant is unde"ined. It is an error to use this ragma ina "ragment shader.

/enerall(, invariance is ensured at the cost o" "lei6ilit( in otimi@ation, so er"ormance can 6e degraded

6( use o" invariance. ence, use o" this ragma is intended as a de6ug aid, to avoid individuall( declaring

all outut varia6les as invariant.

#.!.2 Invariance of Constant '+pressions

Invariance must 6e guaranteed "or constant eressions. A articular constant eression must evaluate to

the same result i" it aears again in the same shader or a di""erent shader. -his includes the same

eression aearing two shaders o" the same language or shaders o" two di""erent languages.

!onstant eressions must evaluate to the same result when oerated on as alread( descri6ed a6ove "or

invariant varia6les.

#. Order of 7ualification

Hhen multile =uali"ications are resent, the( must "ollow a strict order. -his order is as "ollows.

invariant-6uali/ier inter)olation-6uali/ier storage-6uali/ier )recision-6uali/ier

storage-6uali/ier )arameter-6uali/ier )recision-6uali/ier

47


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Operators and '+pressions

.1 Operators

-he *en/0 'hading 0anguage has the "ollowing oerators.

,recedence Operator Class Operators ssociativit$

1 highestC arenthetical grouing "

Right to 0e"t

& multilicative 0 2 0e"t to Right

$ additive / * 0e"t to Right

# 6it;wise shi"t 33 44 0e"t to Right

3 relational 3 4 3= 4= 0e"t to Right

4 e=ualit( == >= 0e"t to Right

9 6it;wise and ; 0e"t to Right

17 6it;wise eclusive or 9 0e"t to Right

11 6it;wise inclusive or : 0e"t to Right

1 logical and ;; 0e"t to Right

1% logical eclusive or 99 0e"t to Right

1& logical inclusive or : : 0e"t to Right

1$ selection ? Right to 0e"t

1#

Assignmentarithmetic assignments

=

/= *== 0=

2= 33= 44=;= 9= :=

Right to 0e"t

13 lowestC se=uence , 0e"t to Right

-here is no address;o" oerator nor a dere"erence oerator. -here is no t(ecast oeratorG constructors

are used instead.

4


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5 Operators and ()pressions

.2 rra$ Operations

-hese are now descri6ed in 'ection $.3 E'tructure and Arra( *erationsF.

." %unction Calls

I" a "unction returns a value, then a call to that "unction ma( 6e used as an eression, whose t(e will 6e

the t(e that was used to declare or de"ine the "unction.

)unction de"initions and calling conventions are discussed in 'ection #.1 E)unction De"initionsF .

.# Constructors

!onstructors use the "unction call s(nta, where the "unction name is a t(e, and the call makes an o6?ect

o" that t(e. !onstructors are used the same wa( in 6oth initiali@ers and eressions. 'ee 'ection 9

E'hading 0anguage /rammarF "or details.C -he arameters are used to initiali@e the constructed value.

!onstructors can 6e used to re=uest a data t(e conversion to change "rom one scalar t(e to another

scalar t(e, or to 6uild larger t(es out o" smaller t(es, or to reduce a larger t(e to a smaller t(e.

In general, constructors are not 6uilt;in "unctions with redetermined rotot(es. )or arra(s and

structures, there must 6e eactl( one argument in the constructor "or each element or "ield. )or the other

t(es, the arguments must rovide a su""icient num6er o" comonents to er"orm the initiali@ation, and it

is an error to include so man( arguments that the( cannot all 6e used. Detailed rules "ollow. -he

rotot(es actuall( listed 6elow are merel( a su6set o" eamles.

.#.1 Conversion and Scalar Constructors

!onverting 6etween scalar t(es is done as the "ollowing rotot(es indicate:

int$ool) ** %onverts a -oolean value to an int

intfloat) ** %onverts a float value to an int

float$ool) ** %onverts a -oolean value to a float

floatint) ** %onverts a signed integer value to a float

$oolfloat) ** %onverts a float value to a -oolean

$oolint) ** %onverts a signed integer value to a -oolean

uint$ool) ** %onverts a -oolean value to an unsigned integer

uintfloat) ** %onverts a float value to an unsigned integer

uintint) ** %onverts a signed integer value to an unsigned integer

intuint) ** %onverts an unsigned integer to a signed integer

$ooluint) ** %onverts an unsigned integer value to a -oolean value

floatuint) ** %onverts an unsigned integer value to a float value

Hhen constructors are used to convert a floatto an int or uint, the "ractional art o" the "loating;oint

value is droed. It is unde"ined to convert a negative "loating oint value to an uint.

Hhen a constructor is used to convert an int, uint, or a floatto a bool, 7 and 7.7 are converted to false,

and non;@ero values are converted to true. Hhen a constructor is used to convert a boolto an int, uint,

or float, falseis converted to 7 or 7.7, and trueis converted to 1 or 1.7.

4!


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-he constructor int"uintreserves the 6it attern in the argument, which will change the arguments

value i" its sign 6it is set. -he constructor uint"intreserves the 6it attern in the argument, which will

change its value i" it is negative.

Identit( constructors, like floatfloatC are also legal, 6ut o" little use.

'calar constructors with non;scalar arameters can 6e used to take the "irst element "rom a non;scalar.

)or eamle, the constructor floatvecFC will select the "irst comonent o" the vecFarameter.

.#.2 *ector and 5atri+ Constructors

!onstructors can 6e used to create vectors or matrices "rom a set o" scalars, vectors, or matrices. -his

includes the a6ilit( to shorten vectors.

I" there is a single scalar arameter to a vector constructor, it is used to initiali@e all comonents o" the

constructed vector to that scalars value. I" there is a single scalar arameter to a matri constructor, it is

used to initiali@e all the comonents on the matris diagonal, with the remaining comonents initiali@ed

to 7.7.

I" a vector is constructed "rom multile scalars, one or more vectors, or one or more matrices, or a miture

o" these, the vectors comonents will 6e constructed in order "rom the comonents o" the arguments. -he

arguments will 6e consumed le"t to right, and each argument will have all its comonents consumed, in

order, 6e"ore an( comonents "rom the net argument are consumed. 'imilarl( "or constructing a matri

"rom multile scalars or vectors, or a miture o" these. 8atri comonents will 6e constructed and

consumed in column ma?or order. In these cases, there must 6e enough comonents rovided in the

arguments to rovide an initiali@er "or ever( comonent in the constructed value. It is an error to rovide

etra arguments 6e(ond this last used argument.

I" a matri is constructed "rom a matri, then each comonent column i,row;C in the result that has a

corresonding comonent column i,row;C in the argument will 6e initiali@ed "rom there. All other

comonents will 6e initiali@ed to the identit( matri. I" a matri argument is given to a matri constructor,

it is an error to have an( other arguments.

I" the 6asic t(e bool, int, or floatC o" a arameter to a constructor does not match the 6asic t(e o" the

o6?ect 6eing constructed, the scalar construction rules a6oveC are used to convert the arameters.

5"


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'ome use"ul vector constructors are as "ollows:

ve%4float) ** initiali"es ea%5 %omponent of t5e ve%4 :it5 t5e float

ve%1ive%1) ** ma3es a ve%1 :it5 %omponent:ise %onversion

ve%1mat2) ** t5e ve%1 is %olumn A follo:ed $& %olumn '

ve%2float/ float) ** initiali"es a ve%2 :it5 2 floats

ive%4int/ int/ int) ** initiali"es an ive%4 :it5 4 ints

$ve%1int/ int/ float/ float) ** uses 1 -oolean %onversions

ve%2ve%4) ** drops t5e t5ird %omponent of a ve%4

ve%4ve%1) ** drops t5e fourt5 %omponent of a ve%1

ve%4ve%2/ float) ** ve%46x . ve%26x/ ve%46& . ve%26&/ ve%46" . float

ve%4float/ ve%2) ** ve%46x . float/ ve%46& . ve%26x/ ve%46" . ve%26&

ve%1ve%4/ float)

ve%1float/ ve%4)

ve%1ve%2/ ve%2)

'ome eamles o" these are:

ve%1 %olor . ve%1A6A/ '6A/ A6A/ '6A)

ve%1 rg$a . ve%1'6A) ** sets ea%5 %omponent to '6A

ve%4 rg$ . ve%4%olor) ** drop t5e 1t5 %omponent

-o initiali@e the diagonal o" a matri with all other elements set to @ero:

mat2float)

mat4float)

mat1float)

-hat is, result"i#";#is set to the "loat argument "or all i = ; and set to 7 "or all i;.

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-o initiali@e a matri 6( seci"(ing vectors or scalars, the comonents are assigned to the matri elements

in column;ma?or order.

mat2ve%2/ ve%2) ** one %olumn per argument

mat4ve%4/ ve%4/ ve%4) ** one %olumn per argument

mat1ve%1/ ve%1/ ve%1/ ve%1) ** one %olumn per argument

mat4x2ve%2/ ve%2/ ve%2) ** one %olumn per argument

mat2float/ float/ ** first %olumn

float/ float) ** se%ond %olumn

mat4float/ float/ float/ ** first %olumn

float/ float/ float/ ** se%ond %olumn

float/ float/ float) ** t5ird %olumn

mat1float/ float/ float/ float/ ** first %olumn

float/ float/ float/ float/ ** se%ond %olumn

float/ float/ float/ float/ ** t5ird %olumn float/ float/ float/ float) ** fourt5 %olumn

mat2x4ve%2/ float/ ** first %olumn

ve%2/ float) ** se%ond %olumn

A wide range o" other ossi6ilities eist, to construct a matri "rom vectors and scalars, as long as enough

comonents are resent to initiali@e the matri. -o construct a matri "rom a matri:

mat4x4mat1x1) ** ta3es t5e upperleft 4x4 of t5e mat1x1

mat2x4mat1x2) ** ta3es t5e upperleft 2x2 of t5e mat1x1/ last ro: is A/A

mat1x1mat4x4) ** puts t5e mat4x4 in t5e upperleft/ sets t5e lo:er rig5t

** %omponent to '/ and t5e rest to A

.#." Structure Constructors

*nce a structure is de"ined, and its t(e is given a name, a constructor is availa6le with the same name to

construct instances o" that structure. )or eamle:

stru%t lig5t ;

float intensit&

ve%4 position


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.#.# rra$ Constructors

Arra( t(es can also 6e used as constructor names, which can then 6e used in eressions or initiali@ers.

)or eamle,

%onst float %>4? . float>4?76A/ D62/ '6')

%onst float d>4? . float>?76A/ D62/ '6')

float g

666

float a>7? . float>7?g/ '/ g/ 264/ g)

float $>4?

$ . float>4?g/ g H '6A/ g H 26A)

-here must 6e eactl( the same num6er o" arguments as the si@e o" the arra( 6eing constructed. I" no si@e

is resent in the constructor, then the arra( is elicitl( si@ed to the num6er o" arguments rovided. -hearguments are assigned in order, starting at element 7, to the elements o" the constructed arra(. +ach

argument must 6e the same t(e as the element t(e o" the arra(, or 6e a t(e that can 6e converted to the

element t(e o" the arra( according to 'ection &.1.17EImlicit !onversions.F

. *ector Components

-he names o" the comonents o" a vector are denoted 6( a single letter. As a notational convenience,

several letters are associated with each comonent 6ased on common usage o" osition, color or teture

coordinate vectors. -he individual comonents o" a vector can 6e selected 6( "ollowing the varia6le

name with eriod .C and then the comonent name.

-he comonent names suorted are:

>x, , , ? 5se"ul when accessing vectors that reresent oints or normals

>r, g, , a? 5se"ul when accessing vectors that reresent colors

>s, t, ), 6? 5se"ul when accessing vectors that reresent teture coordinates

-he comonent namesx, r, andsare, "or eamle, s(non(ms "or the same "irstC comonent in a vector.


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.! 5atri+ Components

-he comonents o" a matri can 6e accessed using arra( su6scriting s(nta. Al(ing a single su6scrit

to a matri treats the matri as an arra( o" column vectors, and selects a single column, whose t(e is avector o" the same si@e as the matri. -he le"tmost column is column 7. A second su6scrit would then

oerate on the resulting vector, as de"ined earlier "or vectors. ence, two su6scrits select a column and

then a row.

mat1 m

m>'? . ve%126A) ** sets t5e se%ond %olumn to all 26A

m>A?>A? . '6A ** sets t5e upper left element to '6A

m>2?>4? . 26A ** sets t5e 1t5 element of t5e t5ird %olumn to 26A

Behavior is unde"ined when accessing a comonent outside the 6ounds o" a matri with a non;constant

eression. It is an error to access a matri with a constant eression that is outside the 6ounds o" the

matri.

. Structure and rra$ Operations

-he "ields o" a structure and the lengtmethod o" an arra( are selected using the eriod . C.

In total, onl( the "ollowing oerators are allowed to oerate on arra(s and structures as whole entities:

"ield or method selector .

e=ualit( == >=

assignment =

indeing arra(s onl(C Y Z

-he e=ualit( oerators and assignment oerator are onl( allowed i" the two oerands are same si@e andt(e. 'tructure t(es must 6e o" the same declared structure. Both arra( oerands must 6e elicitl(

si@ed. Hhen using the e=ualit( oerators, two structures are e=ual i" and onl( i" all the "ields are

comonent;wise e=ual, and two arra(s are e=ual i" and onl( i" all the elements are element;wise e=ual.

Arra( elements are accessed using the arra( su6scrit oerator 5 6C. An eamle o" accessing an arra(

element is

diffuseColor H. lig5tIntensit&>4? J NdotL

Arra( indices start at @ero. Arra( elements are accessed using an eression whose t(e is int or uint.

Behavior is unde"ined i" a shader su6scrits an arra( with an inde less than 7 or greater than or e=ual to

the si@e the arra( was declared with.

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Arra(s can also 6e accessed with the method oerator . C and the lengt method to =uer( the si@e o" the

arra(:

lig5tIntensit&6lengt5) ** return t5e si"e of t5e arra&

.3 ssignments

Assignments o" values to varia6le names are done with the assignment oerator = C:

lvalueexpression . rvalueexpression

-he lvalue-ex)ression evaluates to an l;value. -he assignment oerator stores the value o" rvalue-

ex)ressionintothel;value and returns an r;value with the t(e and recision o" lvalue-ex)ression. -he

lvalue-ex)ressionand rvalue-ex)ressionmust have the same t(e, or the eression must have a t(e in

the ta6le in 'ection &.1.17EImlicit !onversionsF that converts to the t(e o" lvalue-ex)ression, in which

case an imlicit conversion will 6e done on the rvalue-ex)ression6e"ore the assignment is done. An(

other desired t(e;conversions must 6e seci"ied elicitl( via a constructor. 0;values must 6e writa6le.Varia6les that are 6uilt;in t(es, entire structures or arra(s, structure "ields, l;values with the "ield selector

. C alied to select comonents or swi@@les without reeated "ields, l;values within arentheses, and l;

values dere"erenced with the arra( su6scrit oerator 5 6 C are all l;values. *ther 6inar( or unar(

eressions, "unction names, swi@@les with reeated "ields, and constants cannot 6e l;values. -he ternar(

oerator ?C is also not allowed as an l;value.

+ressions on the le"t o" an assignment are evaluated 6e"ore eressions on the right o" the assignment.

-he other assignment oerators are

add into /=C

su6tract "rom *=C

multil( into =C divide into 0=C

modulus into 2=C

le"t shi"t 6( 33=C

right shi"t 6( 44=C

and into ;=C

inclusive;or into :=C

eclusive;or into 9=C

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where the general eression

lvalue op. expression

is e=uivalent to

lvalue . lvalue opexpression

where o) is as descri6ed 6elow, and the l;value and eression must satis"( the semantic re=uirements o"

6oth o)and e=uals =C.

Reading a varia6le 6e"ore writing or initiali@ingC it is legal, however the value is unde"ined.

.9 '+pressions

+ressions in the shading language are 6uilt "rom the "ollowing:

!onstants o" t(e bool, int, uint, float, all vector t(es, and all matri t(es.

!onstructors o" all t(es.

Varia6le names o" all t(es.

An arra( name with the length method alied.

'u6scrited arra( names.

)unction calls that return values.

!omonent "ield selectors and arra( su6scrit results.

2arenthesi@ed eression. An( eression can 6e arenthesi@ed. 2arentheses can 6e used to grou

oerations. *erations within arentheses are done 6e"ore oerations across arentheses.

-he arithmetic 6inar( oerators add /C, su6tract *C, multil( C, and divide 0C oerate on integer and

"loating;oint scalars, vectors, and matrices. I" one oerand is "loating;oint 6ased and the other is

not, then the conversions "rom 'ection &.1.17EImlicit !onversionsF are alied to the non;"loating;

oint;6ased oerand. I" the oerands are integer t(es, the( must 6oth 6e signed or 6oth 6e unsigned.

All arithmetic 6inar( oerators result in the same "undamental t(e signed integer, unsigned integer,

or "loating;ointC as the oerands the( oerate on, a"ter oerand t(e conversion. A"ter conversion,

the "ollowing cases are valid

-he two oerands are scalars. In this case the oeration is alied, resulting in a scalar.

*ne oerand is a scalar, and the other is a vector or matri. In this case, the scalar oeration is

alied indeendentl( to each comonent o" the vector or matri, resulting in the same si@e vector

or matri.

-he two oerands are vectors o" the same si@e. In this case, the oeration is done comonent;wise

resulting in the same si@e vector.

-he oerator is add /C, su6tract *C, or divide 0C, and the oerands are matrices with the same

num6er o" rows and the same num6er o" columns. In this case, the oeration is done comonent;

wise resulting in the same si@e matri.

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-he logical 6inar( oerators and ;;C, or : : C, and eclusive or 99C oerate onl( on two Boolean

eressions and result in a Boolean eression. And ;;C will onl( evaluate the right hand oerand

i" the le"t hand oerand evaluated to true. *r : :C will onl( evaluate the right hand oerand i" the le"t

hand oerand evaluated to false. +clusive or 99C will alwa(s evaluate 6oth oerands.

-he logical unar( oerator not >C. It oerates onl( on a Boolean eression and results in a Boolean

eression. -o oerate on a vector, use the 6uilt;in "unction not.

-he se=uence ,C oerator that oerates on eressions 6( returning the t(e and value o" the right;

most eression in a comma searated list o" eressions. All eressions are evaluated, in order,

"rom le"t to right.

-he ternar( selection oerator ?C. It oerates on three eressions ex)1ex)2?ex)@C. -his

oerator evaluates the "irst eression, which must result in a scalar Boolean. I" the result is true, it

selects to evaluate the second eression, otherwise it selects to evaluate the third eression. *nl(

one o" the second and third eressions is evaluated. -he second and third eressions can 6e an(

t(e, as long their t(es match, or there is a conversion in 'ection &.1.17EImlicit !onversionsF that

can 6e alied to one o" the eressions to make their t(es match. -his resulting matching t(e is thet(e o" the entire eression.

-he ones comlement oerator


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.16 *ector and 5atri+ Operations

Hith a "ew ecetions, oerations are comonent;wise. 5suall(, when an oerator oerates on a vector or

matri, it is oerating indeendentl( on each comonent o" the vector or matri, in a comonent;wise"ashion. )or eamle,

ve%4 v/ u

float f

v . u H f

will 6e e=uivalent to

v6x . u6x H f

v6& . u6& H f

v6" . u6" H f

And

ve%4 v/ u/ :

: . v H u

will 6e e=uivalent to

:6x . v6x H u6x

:6& . v6& H u6&

:6" . v6" H u6"

and likewise "or most oerators and all integer and "loating oint vector and matri t(es. -he ecetions

are matri multilied 6( vector, vector multilied 6( matri, and matri multilied 6( matri. -hese do

not oerate comonent;wise, 6ut rather er"orm the correct linear alge6raic multil(.

ve%4 v/ u

mat4 m

u . v J m

is e=uivalent to

u6x . dotv/ m>A?) ** m>A? is t5e left %olumn of m

u6& . dotv/ m>'?) ** dota/$) is t5e inner dot) produ%t of a and $

u6" . dotv/ m>2?)

And

u . m J v

is e=uivalent to

u6x . m>A?6x J v6x H m>'?6x J v6& H m>2?6x J v6"

u6& . m>A?6& J v6x H m>'?6& J v6& H m>2?6& J v6"

u6" . m>A?6" J v6x H m>'?6" J v6& H m>2?6" J v6"

6"


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And

mat4 m/ n/ r

r . m J n

is e=uivalent to

r>A?6x . m>A?6x J n>A?6x H m>'?6x J n>A?6& H m>2?6x J n>A?6"

r>'?6x . m>A?6x J n>'?6x H m>'?6x J n>'?6& H m>2?6x J n>'?6"

r>2?6x . m>A?6x J n>2?6x H m>'?6x J n>2?6& H m>2?6x J n>2?6"

r>A?6& . m>A?6& J n>A?6x H m>'?6& J n>A?6& H m>2?6& J n>A?6"

r>'?6& . m>A?6& J n>'?6x H m>'?6& J n>'?6& H m>2?6& J n>'?6"

r>2?6& . m>A?6& J n>2?6x H m>'?6& J n>2?6& H m>2?6& J n>2?6"

r>A?6" . m>A?6" J n>A?6x H m>'?6" J n>A?6& H m>2?6" J n>A?6"

r>'?6" . m>A?6" J n>'?6x H m>'?6" J n>'?6& H m>2?6" J n>'?6"

r>2?6" . m>A?6" J n>2?6x H m>'?6" J n>2?6& H m>2?6" J n>2?6"

and similarl( "or other si@es o" vectors and matrices.

61


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! Statements and Structure

-he "undamental 6uilding 6locks o" the *en/0 'hading 0anguage are:

statements and declarations

"unction de"initions

selection if*else and switc*case*default

iteration"for, wile, and do*wile

?ums"discard, return, break, and continueC

-he overall structure o" a shader is as "ollows

translation-unit:

gloal-!eclaration

translation-unit gloal-!eclaration

gloal-!eclaration:

/unction-!e/inition

!eclaration

-hat is, a shader is a se=uence o" declarations and "unction 6odies. )unction 6odies are de"ined as

/unction-!e/inition:

/unction-)rotot)e > statement-list ?

statement-list:

statement

statement-list statement

statement:

com)oun!-statement

sim)le-statement

!url( 6races are used to grou se=uences o" statements into comound statements.

com)oun!-statement:

> statement-list ?sim)le-statement:

!eclaration-statement

ex)ression-statement

selection-statement

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6 State*ents and Structure

iteration-statement

;um)-statement

'imle declaration, eression, and ?um statements end in a semi;colon.

-his a6ove is slightl( simli"ied, and the comlete grammar seci"ied in 'ection 9 E'hading 0anguage

/rammarF should 6e used as the de"initive seci"ication.

Declarations and eressions have alread( 6een discussed.

!.1 %unction )efinitions

As indicated 6( the grammar a6ove, a valid shader is a se=uence o" glo6al declarations and "unction

de"initions. A "unction is declared as the "ollowing eamle shows:

** protot&pe

returnT&pe fun%tionName t&peA argA/ t&pe' arg'/ 666/ t&pen argn)

and a "unction is de"ined like

** definition

returnT&pe fun%tionName t&peA argA/ t&pe' arg'/ 666/ t&pen argn)

;

** do some %omputation

return returnValue

gl_9axTextureCoords?

**

** %ompati$ilit& profile onl&

**

uniform float gl_NormalS%ale

**


**

uniform ve%1 gl_Clip@lane>gl_9axClip@lanes?

**


**

stru%t gl_@oint@arameters ;

float si"e

float si"e9in

float si"e9ax

float fadeT5res5oldSi"e

float distan%eConstant8ttenuation

float distan%eLinear8ttenuation

float distan%eMuadrati%8ttenuation


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7 Bui%t+in #aria$%es

**


**

stru%t gl_Lig5tSour%e@arameters ;

ve%1 am$ient ** 8%li

ve%1 diffuse ** %li

ve%1 spe%ular ** S%li

ve%1 position ** @pli

ve%1 5alfVe%tor ** erived( Gi

ve%4 spotire%tion ** Sdli

float spotExponent ** Srli

float spotCutoff ** Crli

** range( >A6A/A6A?/ 'A6A)

float spotCosCutoff ** erived( %osCrli)

** range( >'6A/A6A?/'6A)

float %onstant8ttenuation ** A

float linear8ttenuation ** '

float =uadrati%8ttenuation** 2

gl_9axLig5ts?

stru%t gl_Lig5t9odel@arameters ;

ve%1 am$ient ** 8%s


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**

** %ompati$ilit& profile onl&**

uniform ve%1 gl_TextureEnvColor>gl_9axTexturenits?

uniform ve%1 gl_E&e@laneS>gl_9axTextureCoords?

uniform ve%1 gl_E&e@laneT>gl_9axTextureCoords?

uniform ve%1 gl_E&e@laneR>gl_9axTextureCoords?

uniform ve%1 gl_E&e@laneM>gl_9axTextureCoords?

uniform ve%1 gl_O$0e%t@laneS>gl_9axTextureCoords?

uniform ve%1 gl_O$0e%t@laneT>gl_9axTextureCoords?

uniform ve%1 gl_O$0e%t@laneR>gl_9axTextureCoords?

uniform ve%1 gl_O$0e%t@laneM>gl_9axTextureCoords?

**


**

stru%t gl_Fog@arameters ;

ve%1 %olor

float densit&

float start

float end

float s%ale ** erived( '6A * end start)


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in float gl_FogFragCoord

in ve%1 gl_TexCoord>?

in ve%1 gl_Color

in ve%1 gl_Se%ondar&Color

-he values ingl_olorandgl_+econ!arolorwill 6e derived automaticall( 6( the s(stem "rom

gl_$rontolor, gl_


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3 -uiltin %unctions

-he *en/0 'hading 0anguage de"ines an assortment o" 6uilt;in convenience "unctions "or

GLSL Specification 1.50.11

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