GLSL Specification 4.10.6

8/12/2019 GLSL Specification 4.10.6

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The OpenGLShading Language

Language Version: 4.10

Document Revision: 6

24-Jul-2010

Editor: John Kessenich, Intel

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


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Copyright (c) 2008-2010 The Khronos Group Inc. All Rights Reserve.

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Table of Contents

1 Introduction.................................................................................................................................1

1.1 Acknowledgents................................................................................................................!1.! "hanges................................................................................................................................ !

1.!.1 "hanges #ro revision $...............................................................................................!1.!.! "hanges #ro revision %...............................................................................................&1.!.& "hanges #ro revision &...............................................................................................&1.!.% "hanges #ro revision !...............................................................................................&1.!.$ "hanges #ro revision 1...............................................................................................&1.!.' (uar) o# "hanges #ro Version %.**..................................................................... &

1.& +verview.............................................................................................................................. %1.% Error andling......................................................................................................................%1.$ -)ograhical "onventions................................................................................................. %

1.' Derecation.......................................................................................................................... %! +verview o# +en/0 (hading....................................................................................................$

!.1 Verte 2rocessor.................................................................................................................. $!.! -essellation "ontrol 2rocessor.............................................................................................$!.& -essellation Evaluation 2rocessor........................................................................................'!.% /eoetr) 2rocessor............................................................................................................. '!.$ 3ragent 2rocessor.............................................................................................................. '

& Basics.......................................................................................................................................... 4&.1 "haracter (et........................................................................................................................ 4&.! (ource (trings...................................................................................................................... 4&.& 2rerocessor......................................................................................................................... 5

&.% "oents.......................................................................................................................... 1&&.$ -okens................................................................................................................................ 1&&.' Ke)words............................................................................................................................1&&.4 Identi#iers........................................................................................................................... 1$&.5 De#initions..........................................................................................................................1'

&.5.1 (tatic 6se....................................................................................................................1'&.5.! 6ni#or and 7on86ni#or "ontrol 3low.................................................................. 1'&.5.& D)naicall) 6ni#or Eressions.............................................................................14

% Varia9les and -)es..................................................................................................................15%.1 Basic -)es........................................................................................................................ 15

%.1.1 Void............................................................................................................................ !1

%.1.! Booleans..................................................................................................................... !1%.1.& Integers....................................................................................................................... !!%.1.% 3loats.......................................................................................................................... !%%.1.$ Vectors........................................................................................................................!$%.1.' atrices...................................................................................................................... !$%.1.4 (alers..................................................................................................................... !$

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%.1.5 (tructures....................................................................................................................!'%.1.; Arra)s......................................................................................................................... !4%.1.1* Ilicit "onversions................................................................................................ !;

%.! (coing...............................................................................................................................&*%.& (torage


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$.; Eressions........................................................................................................................ 4*$.1* Vector and atri +erations..........................................................................................4&

' (tateents and (tructure...........................................................................................................4$

'.1 3unction De#initions...........................................................................................................4''.1.1 3unction "alling "onventions....................................................................................45'.1.! (u9routines.................................................................................................................5*

'.! (election.............................................................................................................................51'.& Iteration.............................................................................................................................. 5!'.% Jus..................................................................................................................................5&

4 Built8in Varia9les......................................................................................................................5%4.1 Built8In 0anguage Varia9les.............................................................................................. 5%

4.1.1 "oati9ilit) 2ro#ile Built8In 0anguage Varia9les....................................................;!4.! "oati9ilit) 2ro#ile Verte (hader Built8In Inuts......................................................... ;$4.& Built8In "onstants.............................................................................................................. ;$

4.&.1 "oati9ilit) 2ro#ile Built8In "onstants....................................................................;'4.% Built8In 6ni#or (tate....................................................................................................... ;'

4.%.1 "oati9ilit) 2ro#ile (tate......................................................................................... ;45 Built8in 3unctions................................................................................................................... 1*1

5.1 Angle and -rigonoetr) 3unctions..................................................................................1*!5.! Eonential 3unctions......................................................................................................1*%5.& "oon 3unctions.......................................................................................................... 1*$5.% 3loating82oint 2ack and 6nack 3unctions..................................................................... 1115.$ /eoetric 3unctions........................................................................................................ 11&5.' atri 3unctions.............................................................................................................. 11$5.4 Vector Relational 3unctions.............................................................................................114

5.5 Integer 3unctions..............................................................................................................11;5.; -eture 3unctions.............................................................................................................1!1

5.;.1 -eture


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1 Introduction

-his docuent seci#ies onl) version %.1* o# the +en/0 (hading 0anguage. It re=uires >>VER(I+7>>

to su9stitute %1*, and re=uires #versionto accet onl) %1*. I# #version is declared with a saller

nu9er, the language acceted is a revious version o# the shading language, which will 9e suorted

deending on the version and t)e o# contet in the +en/0 A2I. (ee the +en/0 /rahics ()ste

(eci#ication, Version %.1, #or details on what language versions are suorted.

2revious versions o# the +en/0 (hading 0anguage, as well as the +en/0 E( (hading 0anguage, are

not strict su9sets o# the version seci#ied here, articularl) with resect to recision, nae8hiding rules,

and treatent o# inter#ace varia9les. (ee the seci#ication corresonding to a articular language version

#or details seci#ic to that version o# the language.

All +en/0 /rahics ()ste (eci#ication re#erences in this seci#ication are to version %.1.

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1 Introduction

1.1 Acknowledgments

-his seci#ication is 9ased on the work o# those who contri9uted to ast versions o# the +en/0

0anguage (eci#ication, the +en/0 E( !.* 0anguage (eci#ication, and the #ollowing contri9utors tothis version:

2at Brown, 7vidia

Je## Bol?, 7vidia

3rank "hen

2ierre Boudier, AD

2iers Daniell, 7vidia

"hris Dodd, 7vidia

Eric @erness, 7vidia

7ick aeel, AD

Jason /reen, -rans/aing

Brent Insko, Intel

Jon 0eechBill 0icea8Kane, AD

Daniel Koch, -ransgaing

Barthold 0ichten9elt, 7vidia

Bruce err), AR

Ro9ert +hannessian

Acorn 2oole), 7vidia

Kevin Rogovin

Ian Roanick, Intel

/reg Roth, 7vidia

/raha (ellers, AD

Dave (hreiner, AR

Jere) (andel, Ale

Ro9ert (ison,


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1 Introduction

1.2.2 Changes from revision

Added the changes section #or revision &.

inor udates #or linking o# ultile rogras, s)ncing with the latest etension seci#ication #orsearate shader o9ects /0>ARB>searate>shader>o9ectsF and incororating other editorial

#eed9ack.

1.2.! Changes from revision !

Relaed recision re=uireents #or exp F and srt F.

3or esta9lishing inter#aces 9etween rogras, no longer allow general glo9al redeclaration o# 9uilt8in

9lock e9ers outside o# 9lock redeclarations.

1.2. Changes from revision 2

Add the inter#ace 9lockgl!er"ragment and redeclaration o# inter#ace 9locks to esta9lish inter#aces

9etween rogras #or 9uilt8in varia9les.

6dated soe recisions with range8seci#ic 9ehavior.

1.2.5 Changes from revision 1

Added suort #or ultile rogras.

Edited all use o# GrograG #or consistenc) with suort o# 9oth a single rogra or ultile

rogras to esta9lish a colete ieline.

inor graatical #ies.

1.2." Summar# of Changes from $ersion .%%

7ote: 7o #eatures were reoved or derecated 9etween versions %.** and %.1*.

(uort #or artitioning shaders into ultile rogras to rovide light8weight iing o# di##erent

shader stages.

Iroved coati9ilit) with the +en/0 E( (hading 0anguage.

E licitl) state the re=uired recision o# ost oerations.

Add '%89it #loating8oint attri9utes #or verte shader inuts.

(uort v iewort arra)s so where t he geoetr) shader selects which viewort arra) will trans#or its

outut.

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1 Introduction

1.! Overvie&

-his docuent descri9es #he $%en&L 'ha(ing Language) version %.1*.

Indeendent coilation units written in this language are calledsha(ers. A%rogramis a colete set o#shaders that are coiled and linked together, coletel) creating one or ore o# the rograa9le

stages o# the +en/0 ieline. All the shaders #or a single rograa9le stage ust 9e within the sae

rogra. A colete set o# rograa9le stages can 9e ut into a single rogra or the stages can 9e

artitioned across ultile rogras. -he ai o# this docuent is to thoroughl) seci#) the rograing

language. -he +en/0 /rahics ()ste (eci#ication will seci#) the +en/0 entr) oints used to

aniulate and counicate with rogras and shaders.

1. 'rror (andling

"oilers, in general, accet rogras that are ill8#ored, due to the iossi9ilit) o# detecting all ill8

#ored rogras. 2orta9ilit) is onl) ensured #or well8#ored rogras, which this seci#ication

descri9es. "oilers are encouraged to detect ill8#ored rogras and issue diagnostic essages, 9ut are

not re=uired to do so #or all cases. "oilers are re=uired to return essages regarding leicall),

graaticall), or seanticall) incorrect shaders.

1.5 T#pographical Conventions

Italic, 9old, and #ont choices have 9een used in this seci#ication riaril) to irove reada9ilit). "ode

#ragents use a #ied width #ont. Identi#iers e9edded in tet are italici?ed. Ke)words e9edded in tet

are 9old. +erators are called 9) their nae, #ollowed 9) their s)9ol in 9old in arentheses. -he

clari#)ing graar #ragents in the tet use 9old #or literals and italics #or non8terinals. -he o##icial

graar in section ; (hading 0anguage /raarC uses all caitals #or terinals and lower case #or

non8terinals.

1." )eprecation2revious versions o# the +en/0 (hading 0anguage derecated soe #eatures. -hese are clearl) called

out in this seci#ication as derecatedC. -he) are still resent in this version o# the language, 9ut are

targeted #or otential reoval in a #uture version o# the shading language. -he +en/0 A2I has a

#orward coati9ilit) ode that will disallow use o# derecated #eatures. I# coiling in a ode where

use o# derecated #eatures is disallowed, their use causes coile tie errors. (ee the +en/0 /rahics

()ste (eci#ication #or details on what causes derecated language #eatures to 9e acceted or to return

an 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 rograa9le rocessors contained in the +en/0 rocessing ieline.

"urrentl), these rocessors are the verte, tessellation control, tessellation evaluation, geoetr), and

#ragent rocessors.

6nless otherwise noted in this aer, a language #eature alies to all languages, and coon usage will

re#er to these languages as a single language. -he seci#ic languages will 9e re#erred to 9) the nae o#

the rocessor the) target: verte, tessellation control, tessellation evaluation, geoetr), or #ragent.

ost +en/0 state is not tracked or ade availa9le to shaders. -)icall), user8de#ined varia9les will 9e

used #or counicating 9etween di##erent stages o# the +en/0 ieline. owever, a sall aount o#state is still tracked and autoaticall) ade availa9le to shaders, and there are a #ew 9uilt8in varia9les #or

inter#aces 9etween di##erent stages o# the +en/0 ieline.

2.1 $erte* +rocessor

-he verte* %rocessoris a rograa9le unit that oerates on incoing vertices and their associated data.

"oilation units written in the +en/0 (hading 0anguage to run on this rocessor are called verte*

sha(ers. @hen a colete set o# verte shaders are coiled and linked, the) result in a verte* sha(er

e*ecuta+lethat runs on the verte rocessor.

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

knowledge o# several vertices at a tie.

2.2 Tessellation Control +rocessor

-he tessellation control rocessor is a rograa9le unit that oerates on a atch o# incoing vertices

and their associated data, eitting a new outut atch. "oilation units written in the +en/0 (hading

0anguage to run on this rocessor are called tessellation control shaders. @hen a colete set o#

tessellation control shaders are coiled and linked, the) result in a tessellation control shader eecuta9le

that runs on the tessellation control rocessor.

-he tessellation control shader is invoked #or each verte o# the outut atch. Each invocation can read

the attri9utes o# an) verte in the inut or outut atches, 9ut can onl) write er8verte attri9utes #or the

corresonding outut atch verte. -he shader invocations collectivel) roduce a set o# er8atch

attri9utes #or the outut atch. A#ter all tessellation control shader invocations have coleted, the outut

vertices and er8atch attri9utes are asse9led to #or a atch to 9e used 9) su9se=uent ieline stages.

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2 Overview of OpenGL Shading

-essellation control shader invocation run ostl) indeendentl), with unde#ined relative eecution order.

owever, the 9uilt8in #unction 9arrierF can 9e used to control eecution order 9) s)nchroni?ing

invocations, e##ectivel) dividing tessellation control shader eecution into a set o# hases. -essellation

control shaders will get unde#ined results i# one invocation reads a er8verte or er8atch attri9utewritten 9) another invocation at an) oint during the sae hase, or i# two invocations attet to write

di##erent values to the sae er8atch outut in a single hase.

2.! Tessellation 'valuation +rocessor

-he tessellation evaluation rocessor is a rograa9le unit that evaluates the osition and other

attri9utes o# a verte generated 9) the tessellation riitive generator, using a atch o# incoing vertices

and their associated data. "oilation units written in the +en/0 (hading 0anguage to run on this

rocessor are called tessellation evaluation shaders. @hen a colete set o# tessellation evaluation

shaders are coiled and linked, the) result in a tessellation evaluation shader eecuta9le that runs on the

tessellation evaluation rocessor.

Each invocation o# the tessellation evaluation eecuta9le coutes the osition and attri9utes o# a singleverte generated 9) the tessellation riitive generator. -he eecuta9le can read the attri9utes o# an)

verte in the inut atch, lus the tessellation coordinate, which is the relative location o# the verte in the

riitive 9eing tessellated. -he eecuta9le writes the osition and other attri9utes o# the verte.

2. Geometr# +rocessor

-hegeometr, %rocessor is a rograa9le unit that oerates on data #or incoing vertices #or a riitive

asse9led a#ter verte rocessing and oututs a se=uence o# vertices #oring outut riitives.

"oilation units written in the +en/0 (hading 0anguage to run on this rocessor are calledgeometr,

sha(ers. @hen a colete set o# geoetr) shaders are coiled and linked, the) result in ageometr,

sha(er e*ecuta+le that runs on the geoetr) rocessor.

A single invocation o# the geoetr) shader eecuta9le on the geoetr) rocessor will oerate on a

declared inut riitive with a #ied nu9er o# vertices. -his single invocation can eit a varia9le

nu9er o# vertices that are asse9led into riitives o# a declared outut riitive t)e and assed to

su9se=uent ieline stages.

2.5 ,ragment +rocessor

-hefragment %rocessoris a rograa9le unit that oerates on #ragent values and their associated

data. "oilation units written in the +en/0 (hading 0anguage to run on this rocessor are called

fragment sha(ers. @hen a colete set o# #ragent shaders are coiled and linked, the) result in a

fragment sha(er e*ecuta+lethat runs on the #ragent rocessor.

A #ragent shader cannot change a #ragentGs *,,F osition. Access to neigh9oring #ragents is not

allowed. -he values couted 9) the #ragent shader are ultiatel) used to udate #rae9u##er eor)

or teture eor), deending on the current +en/0 state and the +en/0 coand that caused the

#ragents to 9e generated.

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! -asics

!.1 Character Set

-he source character set used #or the +en/0 shading languages is a su9set o# A("II. It includes the

#ollowing characters:

-he letters a!", A!$ and the underscore >F.

-he nu9ers%!&.

-he s)9ols eriod .F, lus 'F, dash !F, slash (F, asterisk )F, ercent *F, angled 9rackets +and

,F, s=uare 9rackets -and F, arentheses /and 0F, 9races and 2F, caret 3F, vertical 9ar 4F,

aersand 5F, tilde 6F, e=uals 7F, eclaation oint 8F, colon 9F, seicolon :F, coa $F, and=uestion ark ;F.

-he nu9er sign #F #or rerocessor use.

@hite sace: the sace character, hori?ontal ta9, vertical ta9, #or #eed, carriage8return, and line8

#eed.

0ines are relevant #or coiler diagnostic essages and the rerocessor. -he) are terinated 9)

carriage8return or line8#eed. I# 9oth are used together, it will count as onl) a single line terination. 3or

the reainder o# this docuent, an) o# these co9inations is sil) re#erred to as a new8line. -here is no

line continuation character.

In general, the languageHs 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 end8o#8#ile character.

!.2 Source Strings

-he source #or a single shader is an arra) o# strings o# characters #ro the character set. A single shader

is ade #ro the concatenation o# these strings. Each string can contain ultile lines, searated 9) new8

lines. 7o new8lines need 9e resent in a string a single line can 9e #ored #ro ultile strings. 7o

new8lines or other characters are inserted 9) the ileentation when it concatenates the strings to #or a

single shader. ultile shaders can 9e linked together to #or a single rogra.

Diagnostic essages returned #ro coiling a shader ust identi#) 9oth the line nu9er within a string

and which source string the essage alies to. (ource strings are counted se=uentiall) with the #irst

string 9eing string *. 0ine nu9ers are one ore than the nu9er o# new8lines that have 9een rocessed.

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3 Basics

!.! +reprocessor

-here is a rerocessor that rocesses the source strings as art o# the coilation rocess.

-he colete 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 availa9le

defined

##

Each nu9er sign #F can 9e receded in its line onl) 9) saces or hori?ontal ta9s. It a) also 9e

#ollowed 9) saces and hori?ontal ta9s, receding the directive. Each directive is terinated 9) a new8

line. 2rerocessing does not change the nu9er or relative location o# new8lines in a source string.

-he nu9er sign #F on a line 9) itsel# is ignored. An) directive not listed a9ove will cause a diagnostic

essage and ake the ileentation treat the shader as ill8#ored.

#defineand #undef#unctionalit) are de#ined as is standard #or " rerocessors #or acro de#initions

9oth with and without acro araeters.

-he #ollowing rede#ined acros are availa9le

__LINE__

__FILE__

__VERSION__

L/will su9stitute a decial integer constant that is one ore than the nu9er o# receding new8lines in the current source string.

"L/will su9stitute a decial integer constant that sa)s which source string nu9er is currentl)

9eing rocessed.


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3 Basics

V/R'$will su9stitute a decial integer re#lecting the version nu9er o# the +en/0 shading

language. -he version o# the shading language descri9ed in this docuent will haveV/R'$

su9stitute the decial integer %1*.

All acro naes containing two consecutive underscores C /0C #ollowed 9) a single underscoreF are also

reserved.

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

Eressions #ollowing #ifand #elifare #urther restricted to eressions oerating on literal integer

constants, lus identi#iers consued 9) the definedoerator. It is an error to use #if or #elif on

eressions containing unde#ined acro naes, other than as arguents to the defined oerator.

"haracter constants are not suorted. -he oerators availa9le are as #ollows.

+recedence Operator class Operators ssociativit#

1 highestF arenthetical grouing F 7A

! unar) de#ined 8 L

Right to 0e#t

& ultilicative M N O 0e#t to Right

% additive 8 0e#t to Right

$ 9it8wise shi#t PP QQ 0e#t to Right

' relational P Q P Q 0e#t to Right

4 e=ualit) L 0e#t to Right

5 9it8wise and S 0e#t to Right

; 9it8wise eclusive or T 0e#t to Right

1* 9it8wise inclusive or U 0e#t to Right

11 logical and SS 0e#t to Right

1! lowestF logical inclusive or U U 0e#t to Right

-he definedoerator can 9e used in either o# the #ollowing wa)s:

defined identifier

defined( identifier )

-wo tokens in a acro can 9e concatenated into one token using the token asting ##Foerator, as is

standard #or " rerocessors. -he result ust 9e a valid single token, which will then 9e su9ect to

acro eansion. -hat is, acro eansion haens onl) a#ter token asting. -here are no other nu9ersign 9ased oerators e.g., no # or#=F, nor is there a si"eofoerator.

-he seantics o# al)ing oerators to integer literals in the rerocessor atch those standard in the

" rerocessor, not those in the +en/0 (hading 0anguage.

!


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3 Basics

2rerocessor eressions will 9e evaluated according to the 9ehavior o# the host rocessor, not the

rocessor targeted 9) the shader.

#error will cause the ileentation to ut a diagnostic essage into the shader o9ectHs in#oration log

section '.1.1! (hader and 2rogra ?@raga is used to reserve ragas #or use 9) #uture revisions o# this language. 7o

ileentation a) use a raga whose #irst token is S>?@.

#pragma optimi"eon)

#pragma optimi"eoff)

can 9e used to turn o## otii?ations as an aid in develoing and de9ugging shaders. It can onl) 9e used

outside #unction de#initions. B) de#ault, otii?ation is turned on #or all shaders. -he de9ug raga

#pragma de$ugon)

#pragma de$ugoff)

can 9e used to ena9le coiling and annotating a shader with de9ug in#oration, so that it can 9e used

with a de9ugger. It can onl) 9e used outside #unction de#initions. B) de#ault, de9ug is turned o##.

(haders should declare the version o# the language the) are written to. -he language version a shader is

written to is seci#ied 9)

#version number profileopt

where num+erust 9e a version o# the language, #ollowing the sae convention asV/R'$a9ove.

-he directive #version B1%C is re=uired in an) shader that uses version %.1* o# the language. An)

num+erreresenting a version o# the language a coiler does not suort will cause an error to 9e

generated. Version 1.1* o# the language does not re=uire shaders to include this directive, and shaders that

do not include a #versiondirective will 9e treated as targeting version 1.1*. (haders that seci#)

#version1** will 9e treated as targeting version 1.** o# the +en/0 E( (hading 0anguage.

(haders declaring version 1.%*, 1.$*, &.&*, or %.* o# the shading language can 9e linked with shaders

declaring version %.1* in the sae rogra. (haders targeting earlier versions 1.&* or earlierF o# the

shading language cannot 9e linked with version %.1* shaders.

1"


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3 Basics

I# the otional%rofile arguent is rovided, it ust 9e the nae o# an +en/0 ro#ile. "urrentl), there

are two choices:

%ore

%ompati$ilit&

I# no%rofile arguent is rovided, the de#ault is core. 6nless otherwise seci#ied, this seci#ication is

docuenting the core ro#ile, and ever)thing seci#ied #or the core ro#ile is also availa9le in the

coati9ilit) ro#ile. 3eatures seci#ied as 9elonging seci#icall) to the coati9ilit) ro#ile are not

availa9le in the core ro#ile.

-here is a 9uilt8in acro de#inition #or each ro#ile the ileentation suorts. All ileentations

rovide the #ollowing acro:

#define !L_%ore_profile '

Ileentations roviding the coati9ilit) ro#ile rovide the #ollowing acro:

#define !L_%ompati$ilit&_profile '

-he #versiondirective ust occur in a shader 9e#ore an)thing else, ecet #or coents and white sace.

11


18/162

3 Basics

B) de#ault, coilers o# this language ust issue coile tie s)ntactic, graatical, and seantic

errors #or shaders that do not con#or to this seci#ication. An) etended 9ehavior ust #irst 9e ena9led.

Directives to control the 9ehavior o# the coiler with resect to etensions are declared with the

#extensiondirective

#extension extension_name:behavior

#extension all :behavior

where e*tensionnameis the nae o# an etension. Etension naes are not docuented in this

seci#ication. -he token alleans the 9ehavior alies to all etensions suorted 9) the coiler. -he

+ehavior can 9e one o# the #ollowing

behavior 'ffect

re/uire Behave as seci#ied 9) the etension e*tensionname.

/ive an error on the #extension i# the etension e*tensionname is notsuorted, or i# allis seci#ied.

enable Behave as seci#ied 9) the etension e*tensionname.

@arn on the #extensioni# the etension e*tensionnameis not suorted.

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

&arn Behave as seci#ied 9) the etension e*tensionname, ecet issue warningson an) detecta9le use o# that etension, unless such use is suorted 9) otherena9led or re=uired etensions.

I# all is seci#ied, then warn on all detecta9le uses o# an) etension used.

@arn on the #extensioni# the etension e*tensionnameis not suorted.

disable Behave including issuing errors and warningsF as i# the etensione*tensionnameis not art o# the language de#inition.

I# all is seci#ied, then 9ehavior ust revert 9ack to that o# the non8etendedcore version o# the language 9eing coiled to.

@arn on the #extension i# the etension e*tensionnameis not suorted.

-he extensiondirective is a sile, low8level echanis to set the 9ehavior #or each etension. It does

not de#ine olicies such as which co9inations are aroriate, those ust 9e de#ined elsewhere. +rder

o# directives atters in setting the 9ehavior #or each etension: Directives that occur later override those

seen earlier. -he allvariant sets the 9ehavior #or all etensions, overriding all reviousl) issued

extension directives, 9ut onl) #or the +ehaviorswarnand disable.

12


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3 Basics

-he initial state o# the coiler is as i# the directive

#extension all ( disa$le

was issued, telling the coiler that all error and warning reorting ust 9e done according to thisseci#ication, ignoring an) etensions.

Each etension can de#ine its allowed granularit) o# scoe. I# nothing is said, the granularit) is a shader

that is, a single coilation unitF, and the etension directives ust occur 9e#ore an) non8rerocessor

tokens. I# necessar), the linker can en#orce granularities larger than a single coilation unit, in which

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

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

#lineust have, a#ter acro su9stitution, one o# the #ollowing #ors:

#line line

#line line source-string-number

where line andsource-string-num+er are constant integer eressions. A#ter rocessing this directiveincluding its new8lineF, the ileentation will 9ehave as i# it is coiling at line nu9er lineand

source string nu9ersource-string-num+er. (u9se=uent source strings will 9e nu9ered se=uentiall),

until another #linedirective overrides that nu9ering.

!. Comments

"oents are deliited 9) NM and MN, or 9) NN and a new8line. -he 9egin coent deliiters NM or NNF are

not recogni?ed as coent deliiters inside o# a coent, hence coents cannot 9e nested. I# a

coent resides entirel) within a single line, it is treated s)ntacticall) as a single sace. 7ew8lines are

not eliinated 9) coents.

!.5 To0ens-he language is a se=uence o# tokens. A token can 9e

toen:

e,wor(

i(entifier

integer-constant

floating-constant

o%erator

: 2

!." e#&ords

-he #ollowing are the ke)words in the language, and cannot 9e used #or an) other urose than that

de#ined 9) this docuent:

attribute const uniform varing

laout

13


20/162

3 Basics

centroid flat smooth noperspective

patch sample

break continue do for while switch case defaultif else

subroutine

in out inout

float double int void bool true false

invariant

discard return

matD matE matB dmatD dmatE dmatB

matDxD matDxE matDxB dmatDxD dmatDxE dmatDxB

matExD matExE matExB dmatExD dmatExE dmatExB matBxD matBxE matBxB dmatBxD dmatBxE dmatBxB

vecD vecE vecB ivecD ivecE ivecB bvecD bvecE bvecB dvecD dvecE dvecB

uint uvecD uvecE uvecB

lowp mediump highp precision

sampler1? samplerD? samplerE? samplerCube

sampler1?Shadow samplerD?Shadow samplerCubeShadow

sampler1?Arra samplerD?Arra

sampler1?ArraShadow samplerD?ArraShadow

isampler1? isamplerD? isamplerE? isamplerCube

isampler1?Arra isamplerD?Arra

usampler1? usamplerD? usamplerE? usamplerCube

usampler1?Arra usamplerD?Arra

samplerD?Fect samplerD?FectShadow isamplerD?Fect usamplerD?Fect

samplerGuffer isamplerGuffer usamplerGuffer

samplerD?HS isamplerD?HS usamplerD?HS

samplerD?HSArra isamplerD?HSArra usamplerD?HSArra

samplerCubeArra samplerCubeArraShadow isamplerCubeArra usamplerCubeArra

struct

14


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3 Basics

-he #ollowing are the ke)words reserved #or #uture use. 6sing the will result in an error:

common partition active

asm class union enum tpedef template this packed

goto

inline noinline volatile public static extern external interface

long short half fixed unsigned superp

input output

hvecD hvecE hvecB fvecD fvecE fvecB

samplerE?Fect

filter

image1? imageD? imageE? imageCube

iimage1? iimageD? iimageE? iimageCube

uimage1? uimageD? uimageE? uimageCube

image1?Arra imageD?Arra

iimage1?Arra iimageD?Arra uimage1?Arra uimageD?Arra

image1?Shadow imageD?Shadow

image1?ArraShadow imageD?ArraShadow

imageGuffer iimageGuffer uimageGuffer

si"eof cast

namespace using

row


22/162

3 Basics

non(igit: one o#

< a b c d e f g h i I k l m n o p r s t u v w x "

A G C ? J K @ L M N H P O Q R F S > T U V W

(igit: one o#

% 1 D E B X Y Z [ &

Identi#iers starting with gl>C are reserved #or use 9) +en/0, and a) not 9e declared in a shader as

either a varia9le or a #unction. owever, as noted in the seci#ication, there are soe cases where

reviousl) declared varia9les can 9e redeclared to change or add soe roert), and redeclared gl>

naes are allowed to 9e redeclared in a shader onl) #or these seci#ic uroses. ore generall), it is an

error to redeclare a varia9le, including those starting gl>C.

!.3 )efinitions

(oe language rules descri9ed 9elow deend on the #ollowing de#initions.

!.3.1 Static 4se

A shader contains astatic useo# orstatic assignmenttoF a varia9le*i#, a#ter rerocessing, the shader

contains a stateent that would read or writeF*, whether or not run8tie #low o# control will cause that

stateent to 9e eecuted.

!.3.2 4niform and on64niform Control ,lo&

@hen eecuting stateents in a #ragent shader, control #low starts as uniform control flow all #ragents

enter the sae control ath into mainF. "ontrol #low 9ecoes non-uniform when di##erent #ragents

take di##erent aths through control8#low stateents selection, iteration, and usF. "ontrol #low

su9se=uentl) returns to 9eing uni#or a#ter such divergent su98stateents or skied code coletes,until the net tie di##erent control aths are taken.

3or eale:

main)

float a * +++,-- t.is is uniform flo/ %ontrol

if a 0 $) -- t.is expression is true for some fragments1 not all

++++, -- non2uniform flo/ %ontrol

3 else

++++, -- non2uniform flo/ %ontrol

3

++++, -- uniform flo/ %ontrol again

3

+ther eales o# non8uni#or #low control can occur within switch stateents and a#ter conditional

9reaks, continues, earl) returns, and a#ter #ragent discards, when the condition is true #or soe

#ragents 9ut not others. 0oo iterations that onl) soe #ragents eecute are also non8uni#or #low

control.

16


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3 Basics

-his is siilarl) de#ined #or other shader stages, 9ased on the er8instance data ites the) rocess.

!.3.! )#namicall# 4niform '*pressions

A #ragent8shader eression is (,namicall, uniform i# all #ragents evaluating it get the sae resulting

value. @hen loos are involved, this re#ers to the eressionGs value #or the sae loo iteration. @hen

#unctions are involved, this re#ers to calls #ro the sae call oint.

-his is siilarl) de#ined #or other shader stages, 9ased on the er8instance data the) rocess.

7ote that constant eressions are triviall) d)naicall) uni#or. It #ollows that t)ical loo counters

9ased on these are also d)naicall) uni#or.

17


24/162

$ariables and T#pes

All varia9les and #unctions ust 9e declared 9e#ore 9eing used. Varia9le and #unction naes are

identi#iers.

-here are no de#ault t)es. All varia9le and #unction declarations ust have a declared t)e, and

otionall) =uali#iers. A varia9le is declared 9) seci#)ing its t)e #ollowed 9) one or ore naes

searated 9) coas. In an) cases, a varia9le can 9e initiali?ed as art o# its declaration 9) using the

assignent oerator 7F. -he graar near the end o# this docuent rovides a #ull re#erence #or the

s)nta o# declaring varia9les.

6ser8de#ined t)es a) 9e de#ined using structto aggregate a list o# eisting t)es into a single nae.

-he +en/0 (hading 0anguage is t)e sa#e. -here are no ilicit conversions 9etween t)es, with theecetion that an integer value a) aear where a #loating8oint t)e is eected, and 9e converted to a

#loating8oint value. Eactl) how and when this can occur is descri9ed in section %.1.1*Ilicit

"onversionsC and as re#erenced 9) other sections in this seci#ication.

.1 -asic T#pes

-he +en/0 (hading 0anguage suorts the #ollowing 9asic data t)es, groued as #ollows.

-ransarent t)es

T#pe 7eaning

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 #loating8oint scalar

double a single dou9le8recision #loating oint scalar

vecD a two8coonent #loating8oint vector

vecE a three8coonent #loating8oint vector

vecB a #our8coonent #loating8oint vector

dvecD a two8coonent dou9le8recision #loating8oint vector

dvecE a three8coonent dou9le8recision #loating8oint vector

dvecB a #our8coonent dou9le8recision #loating8oint vector

bvecD a two8coonent Boolean vector

bvecE a three8coonent Boolean vector

1


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4 #aria$%es and &'pes

T#pe 7eaning

bvecB a #our8coonent Boolean vector

ivecD a two8coonent signed integer vectorivecE a three8coonent signed integer vector

ivecB a #our8coonent signed integer vector

uvecD a two8coonent unsigned integer vector

uvecE a three8coonent unsigned integer vector

uvecB a #our8coonent unsigned integer vector

matD a !W! #loating8oint atri

matE a &W& #loating8oint atri

matB a %W% #loating8oint atri

matDxD sae as a matDmatDxE a #loating8oint atri with ! coluns and & rows

matDxB a #loating8oint atri with ! coluns and % rows

matExD a #loating8oint atri with & coluns and ! rows

matExE sae as a matE

matExB a #loating8oint atri with & coluns and % rows

matBxD a #loating8oint atri with % coluns and ! rows

matBxE a #loating8oint atri with % coluns and & rows

matBxB sae as a matB

dmatD a !W! dou9le8recision #loating8oint atridmatE a &W& dou9le8recision #loating8oint atri

dmatB a %W% dou9le8recision #loating8oint atri

dmatDxD sae as a dmatD

dmatDxE a dou9le8recision #loating8oint atri with ! coluns and & rows

dmatDxB a dou9le8recision #loating8oint atri with ! coluns and % rows

dmatExD a dou9le8recision #loating8oint atri with & coluns and ! rows

dmatExE sae as a dmatE

dmatExB a dou9le8recision #loating8oint atri with & coluns and % rows

dmatBxD a dou9le8recision #loating8oint atri with % coluns and ! rowsdmatBxE a dou9le8recision #loating8oint atri with % coluns and & rows

dmatBxB sae as a dmatB

1!


26/162


3loating 2oint (aler -)es oa=ueF

T#pe 7eaning

sampler1? a handle #or accessing a 1D teture

samplerD? a handle #or accessing a !D teture

samplerE? a handle #or accessing a &D teture

samplerCube a handle #or accessing a cu9e aed teture

samplerD?Fect a handle #or accessing a rectangular teture

sampler1?Shadow a handle #or accessing a 1D deth teture with coarison

samplerD?Shadow a handle #or accessing a !D deth teture with coarison

samplerD?FectShadow a handle #or accessing a rectangular teture with coarison

sampler1?Arra a handle #or accessing a 1D arra) teture

samplerD?Arra a handle #or accessing a !D arra) teturesampler1?ArraShadow a handle #or accessing a 1D arra) deth teture with coarison

samplerD?ArraShadow a handle #or accessing a !D arra) deth teture with coarison

samplerGuffer a handle #or accessing a 9u##er teture

samplerD?HS a handle #or accessing a !D ulti8sale teture

samplerD?HSArra a handle #or accessing a !D ulti8sale arra) teture

samplerCubeShadow a handle #or accessing a cu9e a deth teture with coarison

samplerCubeArra a handle #or accessing a cu9e a arra) teture

samplerCubeArraShadow a handle #or accessing a cu9e a arra) deth teture withcoarison

(igned Integer (aler -)es oa=ueF

T#pe 7eaning

isampler1? a handle #or accessing an integer 1D teture

isamplerD? a handle #or accessing an integer !D teture

isamplerE? a handle #or accessing an integer &D teture

isamplerCube a handle #or accessing an integer cu9e aed teture

isamplerD?Fect a handle #or accessing an integer !D rectangular teture

isampler1?Arra a handle #or accessing an integer 1D arra) teture

isamplerD?Arra a handle #or accessing an integer !D arra) teture

isamplerGuffer a handle #or accessing an integer 9u##er teture

isamplerD?HS a handle #or accessing an integer !D ulti8sale teture

isamplerD?HSArra a handle #or accessing an integer !D ulti8sale arra) teture

2"


27/162


T#pe 7eaning

isamplerCubeArra a handle #or accessing an integer cu9e a arra) teture

6nsigned Integer (aler -)es oa=ueF

T#pe 7eaning

usampler1? a handle #or accessing an unsigned integer 1D teture

usamplerD? a handle #or accessing an unsigned integer !D teture

usamplerE? a handle #or accessing an unsigned integer &D teture

usamplerCube a handle #or accessing an unsigned integer cu9e aed teture

usamplerD?Fect a handle #or accessing an unsigned integer rectangular teture

usampler1?Arra a handle #or accessing an unsigned integer 1D arra) teture

usamplerD?Arra a handle #or accessing an unsigned integer !D arra) teture

usamplerGuffer a handle #or accessing an unsigned integer 9u##er teture

usamplerD?HS a handle #or accessing an unsigned integer !D ulti8sale teture

usamplerD?HSArra a handle #or accessing an unsigned integer !D ulti8sale teturearra)

usamplerCubeArra a handle #or accessing an unsigned integer cu9e a arra) teture

In addition, a shader can aggregate these using arra)s and structures to 9uild ore cole t)es.

-here are no ointer t)es.

.1.1 $oid3unctions that do not return a value ust 9e declared as void. -here is no de#ault #unction return t)e.

-he ke)word voidcannot 9e used in an) other declarations ecet #or et) #oral or actual araeter

listsF.

.1.2 -ooleans

-o ake conditional eecution o# code easier to eress, the t)e boolis suorted. -here is no

eectation that hardware directl) suorts varia9les o# this t)e. It is a genuine Boolean t)e, holding

onl) one o# two values eaning either true or #alse. -wo ke)words trueand falsecan 9e used as literal

Boolean constants. Booleans are declared and otionall) initiali?ed as in the #ollow eale:

$ool su%%ess, -- de%lare 4su%%ess5 to $e a 6oolean

$ool done * false, -- de%lare and initiali"e 4done5

-he right side o# the assignent oerator 7 F ust 9e an eression whose t)e is bool.

Eressions used #or conditional us if$ for$ ;9$ while$ do!whileF ust evaluate to the t)e bool.

21


28/162


.1.! Integers

(igned and unsigned integer varia9les are #ull) suorted. In this docuent, the ter integer is eant to

generall) include 9oth signed and unsigned integers. 6nsigned integers have eactl) &! 9its o# recision.

(igned integers use &! 9its, including a sign 9it, in twoGs coleent #or. +erations resulting in

over#low or under#low will not cause an) ecetion, nor will the) saturate, rather the) will wraC to )ield

the low8order &! 9its o# the result.

Integers are declared and otionall) initiali?ed with integer eressions, as in the #ollowing eale:

int i1 7 * 89, -- default integer literal t&pe is int

uint : * ;u, -- 4u5 esta$lis.es t.e t&pe as uint

22


29/162


0iteral integer constants can 9e eressed in decial 9ase 1*F, octal 9ase 5F, or headecial 9ase 1'F

as #ollows.

integer-constant :

(ecimal-constant integer-suffi*o%t

octal-constant integer-suffi*o%t

he*a(ecimal-constant integer-suffi*o%t

integer-suffi*: one o#

u

(ecimal-constant :

nonero-(igit

(ecimal-constant (igit

octal-constant :

%

octal-constant octal-(igit

he*a(ecimal-constant :

*he*a(ecimal-(igit

*Xhe*a(ecimal-(igit

he*a(ecimal-constant he*a(ecimal-(igit

(igit :

%

nonero-(igit

nonero-(igit : one o#

1 D E B X Y Z [ &

octal-(igit9 one o#

% 1 D E B X Y Z

he*a(ecimal-(igit9one o#

% 1 D E B X Y Z [ &

a b c d e f

A G C ? J K

7o white sace is allowed 9etween the digits o# an integer constant, including a#ter the leading %or a#ter

the leading %xor %Vo# a constant, or 9e#ore the su##iuor. @hen the su##i u or is resent, the

literal has t)e uint,otherwise the t)e is int. A leading unar) inus sign 8F is interreted as an

arithetic unar) negation, not as art o# the constant.

It is an error to rovide a literal integer whose agnitude is too large to store in a varia9le o# atchingsigned or unsigned t)e.

23


30/162


.1. ,loats

(ingle8recision and dou9le8recision #loating oint varia9les are availa9le #or use in a variet) o# scalar

calculations. 3loating8oint varia9les are de#ined as in the #ollowing eale:

float a1 $ * '+


31/162


.1.5 $ectors

-he +en/0 (hading 0anguage includes data t)es #or generic !8, &8, and %8coonent vectors o#

#loating8oint values, integers, or Booleans. 3loating8oint vector varia9les can 9e used to store colors,

norals, ositions, teture coordinates, teture looku results and the like. Boolean vectors can 9e used

#or coonent8wise coarisons o# nueric vectors. (oe eales o# vector declaration are:

ve%9 tex%oord'1 tex%oord9,

ve%; position,

ve%8 m&R!6>,

ive%9 textureLoo:up,

$ve%; less,

Initiali?ation o# vectors can 9e done with constructors, which are discussed shortl).

.1." 7atrices

-he +en/0 (hading 0anguage has 9uilt8in t)es #or !W!, !W&, !W%, &W!, &W&, &W%, %W!, %W&, and %W%atrices o# #loating8oint nu9ers. atri t)es 9eginning with at have single8recision coonents

while atri t)es 9eginning with dat have dou9le8recision coonents. -he #irst nu9er in the

t)e is the nu9er o# coluns, the second is the nu9er o# rows. I# there is onl) one nu9er, the atri

is s=uare. Eale atri declarations:

mat9 mat9,

mat; opt?atrix,

mat8 vie/1 pro7e%tion,

mat8x8 vie/, -- an alternate /a& of de%laring a mat8

mat;x9 m, -- a matrix /it. ; %olumns and 9 ro/s

dmat8 .ig.@re%ision?V@,

dmat9x8 dm,

Initiali?ation o# atri values is done with constructors descri9ed in section $.% "onstructorsC F incolun8aor order.

.1. Samplers

(aler t)es e.g., samplerD?F are e##ectivel) oa=ue handles to tetures and their #ilters. -he) are

used with the 9uilt8in teture #unctions descri9ed in section 5.4 -eture 0ooku 3unctionsC F to seci#)

which teture to access and how it is to 9e #iltered. -he) can onl) 9e declared as #unction araeters or

uniformvaria9les see section %.&.$ 6ni#orC F. Ecet #or arra) indeing, structure #ield selection, and

arentheses, salers are not allowed to 9e oerands in eressions. (alers aggregated into arra)s

within a shader using s=uare 9rackets - F can onl) 9e indeed with a d)naicall) uni#or integral

eression, otherwise results are unde#ined. (alers cannot 9e treated as l8values hence cannot 9e used

as out or inout #unction araeters, nor can the) 9e assigned into. As uni#ors, the) are initiali?ed onl)

with the +en/0 A2I the) cannot 9e declared with an initiali?er in a shader. As #unction araeters,onl) salers a) 9e assed to salers o# atching t)e. -his ena9les consistenc) checking 9etween

shader teture accesses and +en/0 teture state 9e#ore a shader is run.

25


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.1.3 Structures

6ser8de#ined t)es can 9e created 9) aggregating other alread) de#ined t)es into a structure using the

structke)word. 3or eale,

stru%t lig.t

float intensit&,

ve%; position,

3 lig.tVar,

In this eale, light9ecoes the nae o# the new t)e, and lightVar9ecoes a varia9le o# t)e light.

-o declare varia9les o# the new t)e, use its nae without the ke)word structF.

lig.t lig.tVar9,

ore #orall), structures are declared as #ollows. owever, the colete correct graar is as given in

section ; (hading 0anguage /raarC .

struct-(efinition :ualifier

o%t structname

o%tmem+er-list 2(eclarators

o%t3

mem+er-list :

mem+er-(eclaration3

mem+er-(eclaration mem+er-list3

mem+er-(eclaration :

+asic-t,%e (eclarators3

where name9ecoes the user8de#ined t)e, and can 9e used to declare varia9les to 9e o# this new t)e.

-he nameshares the sae nae sace as other varia9les, t)es, and #unctions. All reviousl) visi9le

varia9les, t)es, constructors, or #unctions with that nae are hidden. -he otional ualifieronl) alies

to an) (eclarators, and is not art o# the t)e 9eing de#ined #or name.

(tructures ust have at least one e9er declaration. e9er declarators a) contain recision

=uali#iers, 9ut a) not contain an) other =uali#iers. Bit #ields are not suorted. e9er t)es ust 9e

alread) de#ined there are no #orward re#erencesF. e9er declarations cannot contain initiali?ers.

e9er declarators can contain arra)s. (uch arra)s ust have a si?e seci#ied, and the si?e ust 9e an

integral constant eression thatGs greater than ?ero see section %.&.& "onstant EressionsCF. Each

level o# structure has its own nae sace #or naes given in e9er declarators such naes need onl)

9e uni=ue within that nae sace.

26


33/162


Anon)ous structures are not suorted. E9edded structure de#initions are not suorted.

stru%t S float f, 3,

stru%t T

S, -- Error( anon&mous stru%tures disallo/ed

stru%t +++ 3, -- Error( em$edded stru%tures disallo/ed

S s, -- O:a&( nested stru%tures /it. name are allo/ed

3,

(tructures can 9e initiali?ed at declaration tie using constructors, as discussed in section $.%.& (tructure

"onstructorsC .

.1.8 rra#s

Varia9les o# the sae t)e can 9e aggregated into arra)s 9) declaring a nae #ollowed 9) 9rackets - F

enclosing an otional si?e. @hen an arra) si?e is seci#ied in a declaration, it ust 9e an integral constant

eression see section %.&.& "onstant EressionsC F greater than ?ero. I# an arra) is indeed with aneression that is not an integral constant eression, or i# an arra) is assed as an arguent to a #unction,

then its si?e ust 9e declared 9e#ore an) such use. It is legal to declare an arra) without a si?e and then

later re8declare the sae nae as an arra) o# the sae t)e and seci#) a si?e. It is illegal to declare an

arra) with a si?e, and then later in the sae shaderF inde the sae arra) with an integral constant

eression greater than or e=ual to the declared si?e. It is also illegal to inde an arra) with a negative

constant eression. Arra)s declared as #oral araeters in a #unction declaration ust seci#) a si?e.

6nde#ined 9ehavior results #ro indeing an arra) with a non8constant eression thatHs greater than or

e=ual to the arra)Hs si?e or less than *. +nl) one8diensional arra)s a) 9e declared. All 9asic t)es and

structures can 9e #ored into arra)s. (oe eales are:

float freAuen%iesB;C,

uniform ve%8 lig.t@ositionB8C,

lig.t lig.tsBC,%onst int numLig.ts * 9,

lig.t lig.tsBnumLig.tsC,

An arra) t)e can 9e #ored 9) seci#)ing a t)e #ollowed 9) s=uare 9rackets Y ZF and including a si?e:

floatB


34/162


and as an alternate wa) o# declaring a varia9le or #unction araeter.

floatB


35/162


.1.1% Implicit Conversions

In soe situations, an eression and its t)e will 9e ilicitl) converted to a di##erent t)e. -he

#ollowing ta9le shows all allowed ilicit conversions:

T#pe of e*pression Can be implicitl# converted to

int uint

int

uint

float

intuintfloat

double

ivecD uvecD

ivecE uvecE

ivecB uvecBivecDuvecD

vecD

ivecE

uvecE

vecE

ivecBuvecB

vecB

ivecDuvecDvecD

dvecD

ivecE

uvecEvecE

dvecE

ivecBuvecBvecB

dvecB

matD dmatD

matE dmatE

matB dmatB

matDxE dmatDxE

matDxB dmatDxB

matExD dmatExD

matExB dmatExB

matBxD dmatBxD

matBxE dmatBxE

2!


36/162


-here are no ilicit arra) or structure conversions. 3or eale, an arra) o# intcannot 9e ilicitl)

converted to an arra) o# float.

@hen an ilicit conversion is done, it is not a re8interretation o# the eressionGs 9it attern, 9ut a

conversion o# its value to an e=uivalent value in the new t)e. 3or eale, the integer value 8Xwill 9e

converted to the #loating8oint value 8X.%. Integer values having ore 9its o# recision than a #loating

oint antissa will lose recision when converted to float.

@hen er#oring ilicit conversion #or 9inar) oerators, there a) 9e ultile data t)es to which the

two oerands can 9e converted. 3or eale, when adding an int value to a uint value, 9oth values can

9e ilicitl) converted to uint, float, and double. In such cases, a #loating8oint t)e is chosen i# either

oerand has a #loating8oint t)e. +therwise, an unsigned integer t)e is chosen i# either oerand has an

unsigned integer t)e. +therwise, a signed integer t)e is chosen. I# oerands can 9e ilicitl) converted

to ultile data t)es deriving #ro the sae 9ase data t)e, the t)e with the sallest coonent si?e is

used.

-he conversions in the ta9le a9ove are done onl) as indicated 9) other sections o# this seci#ication.

.2 Scoping

-he scoe o# a varia9le is deterined 9) where it is declared. I# it is declared outside all #unction

de#initions, it has glo9al scoe, which starts #ro where it is declared and ersists to the end o# the shader

it is declared in. I# it is declared in a whiletest or a for stateent, then it is scoed to the end o# the

#ollowing su98stateent. +therwise, i# it is declared as a stateent within a coound stateent, it is

scoed to the end o# that coound stateent. I# it is declared as a araeter in a #unction de#inition, it is

scoed until the end o# that #unction de#inition. A #unction 9od) has a scoe nested inside the #unctionHs

de#inition. -he ifstateentHs eression does not allow new varia9les to 9e declared, hence does not

#or a new scoe.

3"


37/162


@ithin a declaration, the scoe o# a nae starts iediatel) a#ter the initiali?er i# resent or iediatel)

a#ter the nae 9eing declared i# not. (everal eales:

int x * ',

int x * 91 & * x, -- & is initiali"ed to 9

3

stru%t S

int x,

3,

S S * S=), -- DSD is onl& visi$le as a stru%t and %onstru%tor

S, -- DSD is no/ visi$le as a varia$le

3

int x * x, -- Error if x .as not $een previousl& defined+

All varia9le naes, structure t)e naes, and #unction naes in a given scoe share the sae nae sace.

3unction naes can 9e redeclared in the sae scoe, with the sae or di##erent araeters, without error.

An ilicitl) si?ed arra) can 9e re8declared in the sae scoe as an arra) o# the sae 9ase t)e.

+therwise, within one coilation unit, a declared nae cannot 9e redeclared in the sae scoe doing so

results in a redeclaration error. I# a nested scoe redeclares a nae used in an outer scoe, it hides all

eisting uses o# that nae. -here is no wa) to access the hidden nae or ake it unhidden, without

eiting the scoe that hid it.

-he 9uilt8in #unctions are scoed in a scoe outside the glo9al scoe users declare glo9al varia9les in.

-hat is, a shaderGs glo9al scoe, availa9le #or user8de#ined #unctions and glo9al varia9les, is nested inside

the scoe containing the 9uilt8in #unctions. @hen a #unction nae is redeclared in a nested scoe, it hidesall #unctions declared with that nae in the outer scoe. 3unction declarations rotot)esF cannot occur

inside o# #unctions the) ust 9e at glo9al scoe, or #or the 9uilt8in #unctions, outside the glo9al scoe.

(hared glo9als are glo9al varia9les declared with the sae nae in indeendentl) coiled units

shadersF within the sae language e.g., verteF that are linked together when aking a single rogra.

/lo9als #oring the inter#ace 9etween two di##erent shader languages are discussed in other sections.F

(hared glo9als share the sae nae sace, and ust 9e declared with the sae t)e. -he) will share the

sae storage. (hared glo9al arra)s ust have the sae 9ase t)e and the sae elicit si?e. An arra)

ilicitl) si?ed in one shader can 9e elicitl) si?ed 9) another shader. I# no shader has an elicit si?e

#or the arra), the largest ilicit si?e is used. (calars ust have eactl) the sae t)e nae and t)e

de#inition. (tructures ust have the sae nae, se=uence o# t)e naes, and t)e de#initions, and #ield

naes to 9e considered the sae t)e. -his rule alies recursivel) #or nested or e9edded t)es. All

initiali?ers #or a shared glo9al ust have the sae value, or a link error will result.

31


38/162


.! Storage 9ualifiers

Varia9le declarations a) have one storage =uali#ier seci#ied in #ront o# the t)e. -hese are suari?ed

as

9ualifier 7eaning

P none: de#ault Q local readNwrite eor), or an inut araeter to a #unction

const a coile8tie constant, or a #unction araeter that is read8onl)

incentroid in

sample in

linkage into a shader #ro a revious stage, varia9le is coied inlinkage with centroid 9ased interolationinut linkage with er8sale interolation

outcentroid outsample out

linkage out o# a shader to a su9se=uent stage, varia9le is coied outlinkage with centroid 9ased interolationoutut linkage with er8sale interolation

attribute derecatedlinkage 9etween a verte shader and +en/0 #or er8vertedata

uniform value does not change across the riitive 9eing rocessed, uni#ors#or the linkage 9etween a shader, +en/0, and the alication

varingcentroid varing

derecated linkage 9etween a verte shader and a #ragent shader #orinterolated data

patch in tessellation evaluation shader inut #or er8atch attri9utes

patch out tessellation control shader outut #or er8atch attri9utes

+ututs #ro shader outF and inuts to a shader inF can 9e #urther =uali#ied with one o# these

interolation =uali#iers

9ualifier 7eaning

smooth ersective correct interolation

flat no interolation

noperspective linear interolation

-hese interolation =uali#iers a) onl) recede the =uali#iers in, centroid in, sample in, out, centroid

out,or sample out in a declaration. -he) do not al) to the derecated storage =uali#iers varing or

centroid varing. -he) also do not al) to inuts into a verte shader or oututs #ro a #ragent

shader.

0ocal varia9les can onl) use the const storage =uali#ier.

3unction araeters can use const,in, andout =uali#iers, 9ut as%arameter ualifiers. 2araeter

=uali#iers are discussed in section '.1.1 3unction "alling "onventionsC.

3unction return t)es and structure #ields do not use storage =uali#iers.

32


39/162


Data t)es #or counication #ro one run o# a shader eecuta9le to its net run to counicate

9etween #ragents or 9etween verticesF do not eist. -his would revent arallel eecution o# the sae

shader eecuta9le on ultile vertices or #ragents.

Initiali?ers a) onl) 9e used in declarations o# glo9als with no storage =uali#ier, with a const=uali#ier or

with a uniform=uali#ier. /lo9al varia9les without storage =uali#iers that are not initiali?ed in their

declaration or 9) the alication will not 9e initiali?ed 9) +en/0, 9ut rather will enter main5with

unde#ined values.

.!.1 )efault Storage 9ualifier

I# no =uali#ier is resent on a glo9al varia9le, then the varia9le has no linkage to the alication or shaders

running on other ieline stages. 3or either glo9al or local un=uali#ied varia9les, the declaration will

aear to allocate eor) associated with the rocessor it targets. -his varia9le will rovide readNwrite

access to this allocated eor).

.!.2 Constant 9ualifier7aed coile8tie constants can 9e declared using the const=uali#ier. An) varia9les =uali#ied as

constant are read8onl) varia9les #or that shader. Declaring varia9les as constant allows ore descritive

shaders than using hard8wired nuerical constants. -he const=uali#ier can 9e used with an) o# the 9asic

data t)es. It is an error to write to a constvaria9le outside o# its declaration, so the) ust 9e initiali?ed

when declared. 3or eale,

%onst ve%; ">xis * ve%; =+=1 =+=1 '+=),

(tructure #ields a) not 9e =uali#ied with const. (tructure varia9les can 9e declared as const, and

initiali?ed with a structure constructor.

Initiali?ers #or const declarations ust 9e constant eressions, as de#ined in section %.&.& "onstant

Eressions.C

.!.! Constant '*pressions

A constant e*%ressionis one o#

a literal value e.g., Xor trueF

a glo9al or local varia9le =uali#ied as consti.e., not including #unction araetersF

an eression #ored 9) an oerator on oerands that are all constant eressions, including getting an

eleent or length o# a constant arra), or a #ield o# a constant structure, or coonents o# a constant

vector.

a constructor whose arguents are all constant eressions

a 9uilt8in #unction call whose arguents are all constant eressions, with the ecetion o# the teturelooku #unctions and the noise #unctions. -he 9uilt8in #unctions dKdx, dKd, and fwidthust return

* when evaluated inside an initiali?er with an arguent that is a constant eression.

3unction calls to user8de#ined #unctions non89uilt8in #unctionsF cannot 9e used to #or constant

eressions.

33


40/162


An integral constant e*%ressionis a constant eression that evaluates to a scalar signed or unsigned

integer.

"onstant eressions will 9e evaluated in an invariant wa) so as to create the sae value in ultile

shaders when the sae constant eressions aear in those shaders. (ee section %.'.1-he Invariant


41/162


-essellation control, evaluation, and geoetr) shader inut varia9les get the er8verte values written out

9) outut varia9les o# the sae naes in the revious active shader stage. 3or these inuts, centroid in

and interolation =uali#iers are allowed, 9ut have no e##ect. (ince tessellation control, tessellation

evaluation, and geoetr) shaders oerate on a set o# vertices, each inut var)ing varia9le or inut 9lock,see inter#ace 9locks 9elowF needs to 9e declared as an arra). 3or eale,

in float fooBC, -- geometr& s.ader input for vertex 4out float foo5

Each eleent o# such an arra) corresonds to one verte o# the riitive 9eing rocessed. Each arra) can

otionall) have a si?e declared. -he arra) si?e will 9e set 9), or i# rovided ust 9e consistent withF the

inut laoutdeclarationsF esta9lishing the t)e o# inut riitive, as descri9ed later in section %.&.5.1

Inut 0a)out


42/162


3ragent inuts are declared as in the #ollowing eales:

in ve%; normal,

%entroid in ve%9 Texoord,

invariant %entroid in ve%8 olor,

noperspe%tive in float temperature,

flat in ve%; m&olor,

noperspe%tive %entroid in ve%9 m&Texoord,

-he #ragent shader inuts #or an inter#ace with the last active shader in the verte rocessing ieline.

3or this inter#ace, the last active shader stage outut varia9les and #ragent shader inut varia9les o# the

sae nae ust atch in t)e and =uali#ication other than out atching to inF.

@hen an inter#ace 9etween shader stages is #ored using shaders #ro two searate rogra o9ects, it is

not ossi9le to detect isatches 9etween inuts and oututs when the rogras are linked. @hen there

are isatches 9etween inuts and oututs on such inter#aces, the values assed across the inter#ace will

9e artiall) or coletel) unde#ined. (haders can ensure atches across such inter#aces either 9) using

inut and outut la)out =uali#iers sections %.&.5.1 Inut 0a)out


43/162


.!." Outputs

(hader outut varia9les are declared with a storage =uali#ier using the ke)word out. -he) #or the outut

inter#ace 9etween the declaring shader and the su9se=uent stages o# the +en/0 ieline. +utut

varia9les ust 9e declared at glo9al scoe. During shader eecution the) will 9ehave as noral

un=uali#ied glo9al varia9les. -heir values are coied out to the su9se=uent ieline stage on shader eit.

+nl) outut varia9les that are read 9) the su9se=uent ieline stage need to 9e written it is allowed to

have suer#luous declarations o# outut varia9les.

-here is notan inoutstorage =uali#ier at glo9al scoe #or declaring a single varia9le nae as 9oth inut

and outut to a shader. +utut varia9les ust 9e declared with di##erent naes than inut varia9les.

owever, nesting an inut or outut inside an inter#ace 9lock with an instance nae allows the sae

naes with one re#erenced through a 9lock instance nae.

Verte, tessellation evaluation, and geoetr) outut varia9les outut er8verte data and are declared

using the out, centroid out, or sample out storage =uali#iers, or the derecated varingstorage =uali#ier.

It is an error to use patch out in a verte, tessellation evaluation, or geoetr) shader. +utut varia9les

can onl) 9e #loating8oint scalars, #loating8oint vectors, atrices, signed or unsigned integers or integervectors, or arra)s or structures o# an) these.

Individual verte, tessellation evaluation, and geoetr) oututs are declared as in the #ollowing eales:

out ve%; normal,

%entroid out ve%9 Texoord,

invariant %entroid out ve%8 olor,

noperspe%tive out float temperature, -- var&ing is depre%ated

flat out ve%; m&olor,

noperspe%tive %entroid out ve%9 m&Texoord,

sample out ve%8 perSampleolor,

-hese can also aear in inter#ace 9locks, as descri9ed in section %.&.4 Inter#ace BlocksC. Inter#ace

9locks allow siler addition o# arra)s to the inter#ace #ro verte to geoetr) shader. -he) also allow a#ragent shader to have the sae inut inter#ace as a geoetr) shader #or a given verte shader.

-essellation control shader outut varia9les are a) 9e used to outut er8verte and er8atch data. 2er8

verte outut varia9les are arra)ed see arra,e( under %.&.% InutsF and declared using outor centroid

out storage =uali#iers. 2er8atch outut varia9les are declared using the patch outstorage =uali#ier. 2er8

verte and er8atch outut varia9les can onl) 9e #loating8oint scalars, #loating8oint vectors, atrices,

signed or unsigned integers or integer vectors, or arra)s or structures o# an) these. (ince tessellation

control shaders roduce an arra)ed riitive corising ultile vertices, each er8verte outut varia9le

or outut 9lock, see inter#ace 9locks 9elowF needs to 9e declared as an arra). 3or eale,

out float fooBC, -- feeds next stage input 4in float fooBC5

Each eleent o# such an arra) corresonds to one verte o# the riitive 9eing roduced. Each arra) can

otionall) have a si?e declared. -he arra) si?e will 9e set 9) or i# rovided ust 9e consistent withF the

outut la)out declarationsF esta9lishing the nu9er o# vertices in the outut atch, as descri9ed later in

section %.&.5.! +utut 0a)out


44/162


As descri9ed under the section %.&.% InutsC a9ove, i# a er8verte outut o# the tessellation control

shader is itsel# an arra) with ultile values er verte, it ust aear in an outut 9lock see inter#ace

9locks 9elowF in the tessellation control shader with a 9lock instance nae declared as an arra).

Each tessellation control shader invocation has a corresonding outut atch verte, and a) assign

values to er8verte oututs onl) i# the) 9elong to that corresonding verte. I# a er8verte outut

varia9le is used as an l8value, it is an error i# the eression indicating the verte inde is not the identi#ier

glnvocationD.

-he order o# eecution o# a tessellation control shader invocation relative to the other invocations #or the

sae inut atch is unde#ined unless the 9uilt8in #unction barrierFis used. -his rovides soe control

over relative eecution order. @hen a shader invocation calls barrierF, its eecution auses until all

other invocations have reached the sae oint o# eecution. +utut varia9le assignents er#ored 9)

an) invocation eecuted rior to calling barrierF will 9e visi9le to an) other invocation a#ter the call to

barrierF returns.

Because tessellation control shader invocations eecute in unde#ined order 9etween 9arriers, the values o#

er8verte or er8atch outut varia9les will soeties 9e unde#ined. "onsider the 9eginning and end o#shader eecution and each call to barrierF as s)nchroni?ation oints. -he value o# an outut varia9le

will 9e unde#ined in an) o# the three #ollowing cases:

1. At the 9eginning o# eecution.

!. At each s)nchroni?ation oint, unless

the value was well8de#ined a#ter the revious s)nchroni?ation oint and was not written 9) an)

invocation since, or the value was written 9) eactl) one shader invocation since the revious s)nchroni?ation

oint, or the value was written 9) ultile shader invocations since the revious s)nchroni?ation oint,

and the last write er#ored 9) all such invocations wrote the sae value.

&. @hen read 9) a shader invocation, i#

the value was unde#ined at the revious s)nchroni?ation oint and has not 9een writen 9) the

sae shader invocation since, or the outut varia9le is written to 9) an) other shader invocation 9etween the revious and net

s)nchroni?ation oints, even i# that assignent occurs in code #ollowing the read.

3ragent oututs outut er8#ragent data and are declared using the out storage =uali#ier. It is an error

to use centroid out,sample out, or patch out in a #ragent shader. 3ragent oututs can onl) 9e float,

#loating8oint vectors, signed or unsigned integers or integer vectors, or arra)s o# an) these. atrices and

structures cannot 9e outut. 3ragent oututs are declared as in the #ollowing eales:

out ve%8 Fragmentolor,

out uint Luminosit&,

3


45/162


.!. Interface -loc0s

Inut, outut, and uni#or varia9le declarations can 9e groued into naed inter#ace 9locks to rovide

coarser granularit) 9acking than is achieva9le with individual declarations. -he) can have an otional

instance nae, used in the shader to re#erence their e9ers. An outut 9lock o# one rograa9le

stage is 9acked 9) a corresonding inut 9lock in the su9se=uent rograa9le stage. A uni#or 9lock is

9acked 9) the alication with a 9u##er o9ect. It is illegal to have an inut 9lock in a verte shader or an

outut 9lock in a #ragent shader these uses are reserved #or #uture use.

An inter#ace 9lock is started 9) an in, out, or uniform ke)word, #ollowed 9) a 9lock nae, #ollowed 9)

an oen curl) 9race F as #ollows:

interface-+loc :

la,out-ualifieropt interface-ualifier +loc-name mem+er-list 2instance-nameopt:

la,out-ualifier :

laout / la,out-ualifier-i(-list0

interface-ualifier :in

out

uniform

la,out-ualifier-i(-list

coa searated list o# la,out-ualifier-i(

mem+er-list :

mem+er-(eclaration

mem+er-(eclaration mem+er-list

mem+er-(eclaration :

la,out-ualifieropt ualifiersopt t,%e (eclarators :

instance-name :

i(entifier

i(entifier 7

i(entifier integral-constant-e*%ression 7

Each o# the a9ove eleents is discussed 9elow, with the ecetion o# la)out =uali#iers la,out-ualifier5,

which are de#ined in the net section.

3irst, an eale,

uniform Transform

mat8 ?odelVie/?atrix,

mat8 ?odelVie/@ro7e%tion?atrix,

uniform mat; Normal?atrix, -- allo/ed restatement of Aualifier

float eformation,3,

-he a9ove esta9lishes a uni#or 9lock naed -rans#orC with #our uni#ors groued inside it.

3!


46/162


-)es and declarators are the sae as #or other inut, outut, and uni#or varia9le declarations outside

9locks, with these ecetions:

initiali?ers are not allowed

saler t)es are not allowed

structure de#initions cannot 9e nested inside a 9lock

+therwise, 9uilt8in t)es, reviousl) declared structures, and arra)s o# these are allowed as the t)e o# a

declarator in the sae anner the) are allowed outside a 9lock.

I# no otional =uali#ier is used in a e9er8declaration, the =uali#ication o# the varia9le is ust in, out, or

uniformas deterined 9) interface-ualifier. I# otional =uali#iers are used, the) can include

interolation and storage =uali#iers and the) ust declare an inut, outut, or uni#or varia9le consistent

with the inter#ace =uali#ier o# the 9lock: Inut varia9les, outut varia9les, and uni#or varia9les can onl)

9e in in9locks, out9locks, and uniform9locks, resectivel). Reeating the in, out, or uniform

inter#ace =uali#ier #or a e9erGs storage =uali#ier is otional. Declarations using the derecated

attribute and varing=uali#iers are not allowed. 3or eale,

in ?aterial

smoot. in ve%8 olor', -- legal1 input inside in $lo%:

smoot. ve%8 olor9, -- legal1 DinD in.erited from Din ?aterialD

ve%9 Texoord, -- legal1 Texoord is an input

uniform float >tten, -- illegal1 mismat%.ed interfa%es

var&ing ve%9 Texoord9,--illegal1 depre%ated :e&/ords donDt get ne/ uses

3,

3or this section, de#ine an interface to 9e one o# these

All the uni#ors o# a rogra. -his sans all coilation units linked together within one rogra.

-he 9oundar) 9etween adacent rograa9le ieline stages: -his sans all the oututs in all

coilation units o# the #irst stage and all the inuts in all coilation units o# the second stage.

-he 9lock nae +loc-nameFis used to atch inter#aces: an outut 9lock o# one ieline stage will 9e

atched to an inut 9lock with the sae nae in the su9se=uent ieline stage. 3or uni#or 9locks, the

alication uses the 9lock nae to identi#) the 9lock. Block naes have no other use within a shader

9e)ond inter#ace atching it is an error to use a 9lock nae at glo9al scoe #or an)thing other than as a

9lock nae e.g., use o# a 9lock nae #or a glo9al varia9le nae or #unction nae is currentl) reservedF.

atched 9lock naes within an inter#ace as de#ined a9oveF ust atch in ters o# having the sae

nu9er o# declarations with the sae se=uence o# t)es and the sae se=uence o# e9er naes, as well

as having the sae e9er8wise la)out =uali#ication see net sectionF. 3urtherore, i# a atching 9lock

is declared as an arra), then the arra) si?es ust also atch or #ollow arra) atching rules #or the

inter#ace 9etween a verte and a geoetr) shaderF. An) isatch will generate a link error. A 9lock

nae is allowed to have di##erent de#initions in di##erent inter#aces within the sae shader, allowing, #or

eale, an inut 9lock and outut 9lock to have the sae nae.

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I# an instance nae instance-nameFis not used, the naes declared inside the 9lock are scoed at the

glo9al level and accessed as i# the) were declared outside the 9lock. I# an instance nae instance-nameF

is used, then it uts all the e9ers inside a scoe within its own nae sace, accessed with the #ield

selector . F oerator analogousl) to structuresF. 3or eale,

in Lig.t

ve%8 Lig.t@os,

ve%; Lig.tolor,

3,

in oloredTexture

ve%8 olor,

ve%9 Texoord,

3 ?aterial, -- instan%e name

ve%; olor, -- different olor t.an ?aterial+olor

ve%8 Lig.t@os, -- illegal1 alread& defined

+++

+++ * Lig.t@os, -- a%%essing Lig.t@os

+++ * ?aterial+olor, -- a%%essing olor in oloredTexture $lo%:

+utside the shading language i.e., in the A2IF, e9ers are siilarl) identi#ied ecet the 9lock nae is

alwa)s used in lace o# the instance nae A2I accesses are to inter#aces, not to shadersF. I# there is no

instance nae, then the A2I does not use the 9lock nae to access a e9er, ust the e9er nae.

out Vertex

ve%8 @osition, -- >@I transform-feed$a%: /ill use 4Vertex+@osition5

ve%9 Texture,

3 oords, -- s.ader /ill use 4oords+@osition5

out Vertex9

ve%8 olor, -- >@I /ill use 4olor5

3,

3or 9locks declared as arra)s, the arra) inde ust also 9e included when accessing e9ers, as in this

eale

uniform Transform -- >@I uses 4TransformB9C5 to refer to instan%e 9

mat8 ?odelVie/?atrix,

mat8 ?odelVie/@ro7e%tion?atrix,

float eformation,

3 transformsB8C,

+++

+++ * transformsB9C+?odelVie/?atrix, -- s.ader a%%ess of instan%e 9

-- >@I uses 4Transform+?odelVie/?atrix5 to Auer& an offset or ot.er Auer&

3or uni#or 9locks declared as an arra), each individual arra) eleent corresonds to a searate 9u##ero9ect 9acking one instance o# the 9lock. As the arra) si?e indicates the nu9er o# 9u##er o9ects needed,

uni#or 9lock arra) declarations ust seci#) an arra) si?e. An) integral eression can 9e used to inde

a uni#or 9lock arra), as er section %.1.; Arra)s.

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@hen using +en/0 A2I entr) oints to identi#) the nae o# an individual 9lock in an arra) o# 9locks,

the nae string ust include an arra) inde e.g., #ransform27F. @hen using +en/0 A2I entr) oints

to re#er to o##sets or other characteristics o# a 9lock e9er, an arra) inde ust not 9e seci#ied e.g.,

#ransform.8o(elView8atri*F.

/eoetr) shader inut 9locks ust 9e declared as arra)s and #ollow the arra) declaration and linking

rules #or all geoetr) shader inuts. All other inut and outut 9lock arra)s ust seci#) an arra) si?e.

-here is an ileentation deendent liit on the nu9er o# uni#or 9locks that can 9e used er stage.

I# this liit is eceeded, it will cause a link error.

.!.3 La#out 9ualifiers

0a)out =uali#iers can aear in several #ors o# declar

GLSL Specification 4.10.6

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Transcript of GLSL Specification 4.10.6