Review 1 ====opengl I

8/20/2019 Review 1 ====opengl I

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OpenGL

Comp 575 - Fall 2008


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Input in OpenGL

• You tell OpenGL which user-defined function to callwhen certain events occur.

• OpenGL monitors the input devices. When

something happens (mouse down, e! press, etc. "

OpenGL calls !our code.• #an provide functions for

• window resi$ing

• mouse %utton presses

• mouse %utton releases

• mouse motion

• e!%oard presses


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&

Window Resizing

void glutReshapeFunc(void (*func)(int w, int h))• func is a pointer to a function that takes two arguments,

the new width w and new height h of the window.OpenGL calls this function whenever the window is

resized.• func typically makes a call to glViewport() so that

the display is clipped to the new size, and redefines the

projection matrix so that the aspect ratio of the projected

image matches the viewport.


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Mouse !ents

void glutMouseFunc(void (*func)(int button, int state,

int x, int y));

•

func is a pointer to a function that takes 4 integerparameters. func is called by OpenGL whenever a mousebutton is pressed or released.

• button specifies which mouse button was pressed, and iseither:

GLUT_LEFT_BUTTON,

GLUT_RG!T_BUTTON, or

GLUT_#$$LE_BUTTON


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Mouse !ents

• %t&te specifies the state of the mouse button, andis either:

GLUT_U', or

GLUT_$ON

• and* specify the location (in window-

relative coordinates) of the mouse when theevent occurred.


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)

Mouse Motion

glutMotionFunc( void (*func)(int x, int y));

• func is called by OpenGL when the mouse pointer moves

within the window while one or more mouse buttons are

pressed.• and* specify the location of the mouse when theevent occurred.


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*

"e#$oa%d !ents

void glutKeyboardFunc(void (*func)(unsigned char ey,

int x, int y));

• func is a pointer to a function that takes 3 parameters.func is called by OpenGL whenever a key is pressed.

• +e* is the ASCII value of the key that was pressed

• and* specify the location of the mouse when thekey was pressed.


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Idle Fun&tion

glut!dleFunc( void (*func)());

• func is called by OpenGL when no other events are

pending, when it would otherwise be idle.

• Pass in Null (0) to disable the function.


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Example Code using OpenGL Input

int &in( int &rgc, ch&r-- &rg.)/

glutnit(0&rgc, &rg.)1

glutnit$i%pl&*#o2e( GLUT_RGB 33 GLUT_4NGLE )1

glutnitin2ow4i5e ( 678, 678 )1

glutnitin2ow'o%ition ( 988, 988 )1

glut:re&tein2ow (&rg.;8


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'ample Code (sing OpenGLInput.oi2 2i%pl&* ( .oi2 )/

gl:le&r ( GL_:OLOR_BUFFER_BT )1

gl:olor?f (9@8, 9@8, 9@8)1

glBegin (GL_'ONT4)1glVerte?f (8@7, 8@67, 8@8)1

glVerte?f (8@A7, 8@7, 8@8)1

glVerte?f (8@A7, 8@A7, 8@8)1

glVerte?f (8@67, 8@A7, 8@8)1glEn2()1

glFlu%h()1

>


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'ample Code (sing OpenGLInput.oi2 re%h&pe ()/

c&lle2 when win2ow i% re%i5e2@

t*pic&ll* %et .iewport,

%et proCection &tri, etc@>


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2

'ample Code (sing OpenGLInput.oi2 ou%e (int button, int %t&te, int , int *)/

%witch (button)

c&%e GLUT_LEFT_BUTTOND

if (%t&te GLUT_$ON) 2o %oething

c&%e GLUT_RG!T_BUTTOND

etc@, etc@

>


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&

'ample Code (sing OpenGLInput.oi2 otion (int , int *)/

2o wh&te.er i% &ppropri&te,

e@g@, o.e obCect to point (, *)

>


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'ample Code (sing OpenGLInput.oi2 +e*bo&r2(un%igne2 ch&r +e*, int , int *)

/

%witch (+e*) /

c&%e %D

2o %oething

bre&+1

c&%e 4D

2o %oething here too

bre&+1c&%e tD

c&%e TD f *ou 2ont w&nt to be c&%e %en%iti.e@

2o %oething here too

bre&+1

@

@

@

>>


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Matrix Operations

•OpenGL has 4 matrices it uses:•GL_MODELVIEW

•contains the composite modeling and viewing matrices•GL_PROJECTION

•contains a matrix for the projection transformation

•GL_TEXTURE•used for performing operations on the texture (stretching,moving, rotating, etc.)

•GL_COLOR•used for color space conversions

• /ae sure the appropriate matri0 is current when !ou domodeling, viewing, or pro1ections


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)

Setting the Current Matrix

.oi2 gl#&tri#o2e(Glenu o2e)1

• sets the current matri0 to %e o2e

•

o2e is GL_#O$ELVE, GL_'ROHE:TON,GL_TEITURE, or GL_:OLOR


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Loading the Current Matrix

.oi2 glLo&2#&tri/f2>( TJ'E -)

• loads the arra! of TJ'E GLflo&t or GL2ouble to

the current matri0


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Multiplying the Current Matrix

.oi2 gl#ult#&tri/f2>(TJ'E -)

• ostmultiplies the current matri0 %! , which is of

TJ'E GLflo&t or GL2ouble


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Transformations

•Translation:

.oi2 glTr&n%l&te/f2>( TJ'E 2, TJ'E 2*,TJ'E 25)

• TJ'E is GLflo&t or GL2ouble

• 3he translation is applied to the current matri0 4 maesure the appropriate matri0 is current, e.g.,

gl#&tri#o2e(GL_#O$ELVE)1 glTr&n%l&te(8@?, 8@6, 9@7)1

• 5istances are in world coordinates


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Transformations

•Rotation:

.oi2 glRot&te/f2>(TJ'E &ngle, TJ'E 2,

TJ'E 2*, TJ'E 25)

• rotates &ngle a%out the a0is given %! (2, 2*,

25) and the origin



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Transformations

•Scale:

.oi2 gl4c&le/f2>( TJ'E %, TJ'E %*, TJ'E

%5)

• scales a%out the origin %! (%, %*, %5)



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Viewing - Parallel

•

Setting an orthographic view gl"rtho(#$double left, #$double right,

#$double botto%, #$double top,

#$double &'ear, #$double &Far) • produces a parallel projection with the clipping volume being

• ;left, right


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Viewing - Perspective

• Setting a perspective view gluerspective (#$double fovy, #$double aspect

#$double near, #$double far)

• fo.* is the angle of the field of view in thexz plane,and must bebetween 0 and 180.

• &%pect is the aspect ratio (width / height)• ne&r is the distance from the viewpoint to the nearclipping plane (always positive).

• f&r is the distance from the viewpoint to the farclipping plane (always positive).


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Camera Set-Up

•Used to specify camera position and parametersvoid glu$oo.t( #$double eyex, #$double eyey,#$double eye&, #$double atx, #$double aty, #$doubleat&, #$double upx, #$double upy, #$double up&)

3he e*e point (e*e, e*e*, e*e5) is the loo6rom point3he &t point (&t, &t*, &t5) is the loo7t point3he up point (up, up*, up5) is the 8iew 9p 8ector3his call creates the appropriate matri0 and applies it to the current

matri0. :ence, we need to set the current matri0 mode;

glMatrixMode(#$M"/+$0!+1); gl$oad!dentity(); glu$oo.t(232, 232, 432, 232, 232,

232, 232, 432, 232);


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Creating a Normal Vector

gl'or%al56dfi7(-8+ nx, -8+ ny, -8+ n& )

• TJ'E i% GL2ouble, GLflo&t, or GLint• (n0, n!, n$" are the coordinates of the normal vector

• ?@#7L?=AO>/7L is ena%led, normals do nothave to %e unit si$e. 3he s!stem will normali$e them for!ou.

• Aormali$ation is disa%led %! default• #an ena%le %! calling either glEn&ble(GL_NOR#KLE)

or glEn&ble(GL_RE4:KLE_NOR#KL)


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Setting the Normals

glBegin (GL_'OLJGON)1glNor&l?f.(n8)1

glVerte?f.(.8)1

glNor&l?f.(n9)1glVerte?f.(.9)1

glNor&l?f.(n6)1

glVerte?f.(.6)1glEn2()1


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Lighting

3o set the value of a light source parameter;

gl$ight6if7v(#$enu% light, #$enu% pna%e,-8+ para%s )

• light is the light num%er of the form #$$!#9-i,

where B i C GL=/7D=LGE7"GL_$FFU4E (>GE7"GL_4'E:ULKR (>GE7" GL_'O4TON (0, !, $, w" 4 if w F , it is a directional light

GL_4'OT_$RE:TON (0, !, $"

• para%s is a pointer to an arra! that contains the data


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Lighting

3o set the am%ient lighting in the scene;

gl$ightModel6if76v7(

#$enu% #$$!#9-M"/+$.M:!+'-,

-8+ para%s )

• para%s contains a pointer to ' int or float values that

specif! the am%ient >GE7 intensit! of the entire scene.


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Shading

3o set the shading t!pe for the scene;glhadeModel (#$enu% %ode )

• o2e specifies the t!pe of shading to %edone, and is either

GL_FLKT

GL_4#OOT! (Gouraud shading"

3he default is GL_4#OOT!


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Setting Material Properties

3o set the material properties for the current material;

gl#&teri&l/fi>/.>(GLenu f&ce, GLenu

pn&e, TJ'E p&r&% "

•

f&cespecifies which face the properties should %e

applied to and is;

GL_FRONT

GL_BK:=

GL_FRONT_KN$_BK:=

GL_BK:= is used for shading %ac-facing

pol!gons when two-sided lighting is ena%led


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Setting Material Properties• pna%e specifies which parameter is to %e set and is;

GL_K#BENT• 3he am%ient reflectance of the material. (>GE7"

GL_$FFU4E• 3he diffuse reflectance of the material. (>GE7"

GL_4'E:ULKR• 3he specular reflectance of the material. (>GE7"

GL_E#44ON• 3he emitted light intensit! of the material. (>GE7"

GL_4!NNE44• 3he specular e0ponent of the material. (int or float"


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&&

Texture Mapping

• Steps in using textures in OpenGL;

1. Create a texture.

2. Indicate how the texture is to be applied to eachpixel@

3. Enable texture mapping@

4. Draw the scene, specifying both texture and

geometric coordinates.


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Creating a Texture

gl-ex!%age


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Naming a Texture Object


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)etting t*e +e'tu%en!i%onment.oi2 glTeEn.i (GLenu t&rget, GLenupn&e, GLint p&r&)1

•This call sets the current texturing environment

parameters • t&rget should beGL_TEITURE_ENV • pn&e should beGL_TEITURE_ENV_#O$E • p&r& should beGL_$E:KL • Other texturing functions are available - look at an

OpenGL book for details

• These are probably the parameters you want.


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)etting t*e +e'tu%e,a%amete%s.oi2 glTe'&r&eteri (GLenu t&rget,GLenu pn&e, GLint p&r&)1

•This call sets the current texturing parameters

• t&rget should beGL_TEITURE_6$ • pn&e should beGL_TEITURE_RK'_4 orGL_TEITURE_RK'_T

•

p&r& should be GL_RE'EKT • Other texturing functions are available, but these are

probably the parameters you want.


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+e'tu%e Coo%dinates

When !oudraw an object, you need to specify bothgeometriccoordinates and texture coordinates for eachvertex.

Textures are interpolated between vertices.

void gl-exoord


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'ample o (sing +e'tu%es

.oi2 init (.oi2)/

glGenTeture%(9, 0teN&e)1

glBin2Teture(GL_TEITURE_6$, teN&e)1

glTe'&r&eteri(GL_TEITURE_6$,GL_TEITURE_RK'_4, GL_RE'EKT)1

glTe'&r&eteri(GL_TEITURE_6$,

GL_TEITURE_RK'_T, GL_RE'EKT)1

glTe&ge6$(GL_TEITURE_6$, GL_RGB,wi2th,height, 8, GL_RGB, GL_NT,te&ge)1

>


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.oi2 2i%pl&* (.oi2)/

glEn&ble(GL_TEITURE_6$)1

glTeEn.i(GL_TEITURE_ENV,

GL_TEITURE_ENV_#O$E, GL_$E:KL)1glBin2Teture(GL_TEITURE_6$, teN&e)1

$r&wMu&2()1

glFlu%h()1

gl$i%&ble (GL_TEITURE_6$)1

>


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.oi2 $r&wMu&2(.oi2) /

glBegin(GL_MUK$4)1glTe:oor26f (8@8, 8@8)1glVerte?f (6@8, 9@8, 8@8)1glTe:oor26f (8@8, 9@8)1glVerte?f (6@8, 9@8, 8@8)1glTe:oor26f (9@8, 9@8)1glVerte?f (8@8, 9@8, 8@8)1glTe:oor26f (9@8, 8@8)1glVerte?f (8@8, 9@8, 8@8)1glTe:oor26f (8@8, 8@8)1glVerte?f (9@8, 9@8, 8@8)1glTe:oor26f (8@8, 9@8)1glVerte?f (9@8, 9@8, 8@8)1glTe:oor26f (9@8, 9@8)1glVerte?f (6@9, 9@8, 9@@9)1glTe:oor26f (9@8, 8@8)1glVerte?f (6@9, 9@8, 9@9)1glEn2()1

>


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.e%te' /%%a#s

• /ost vertices appear in multiple pol!gons.• @i0 t!pes of arra!s !ou can activate;

• GL_VERTEI_KRRKJ• GL_:OLOR_KRRKJ• GL_N$EI_KRRKJ• GL_NOR#KL_KRRKJ• GL_TEITURE_:OOR$_KRRKJ•

GL_E$GE_:OOR$_KRRKJ• 7ctivate %! calling

• glEn&ble:lient4t&te(GL_VERTEI_KRRKJ)


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'&

)pe&i#ing t*e ata

%t&tic Glint .ertice%;1

4t&tic GLflo&t color%;1

gl:olor'ointer(?, GL_FLOKT, 8, color%)1

glVerte'ointer(6, GL_NT, 8, .ertice%)1

.oi2 glVerte'ointer(Glint size, GLenu type, GL%i5ei stride,

con%t GL.oi2 -pointer)1

size is t*e num$e% o &oo%dinates1 t#pe spe&ies t*e data t#pe1

st%ide is t*e $#te o3set $etween !e%ti&es1 pointe% is t*e a%%a# wit* t*edata4


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''

(sing t*e /%%a#

glBegin(GL_TRKNGLE4)1

glKrr&*Eleent(8)1

glKrr&*Eleent(9)1

glKrr&*Eleent(?)1

glEn2()1

+*is does t*e same t*ing as

glBegin(GL_TRKNGLE4)1

gl:olor?f. (color% (8-?-%i5eof(GLflo&t)))1

glVerte?f.(.ertice%(8-?-%i5eof(GLint)))1

gl:olor?f. (color% (9-?-%i5eof(GLflo&t)))1

glVerte?f.(.ertice%(9-?-%i5eof(GLint)))1

gl:olor?f. (color% (?-?-%i5eof(GLflo&t)))1

glVerte?f.(.ertice%(?-?-%i5eof(GLint)))1

glEn2()1


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(sing t*e /%%a#

%t&tic GLub*te in2ice% /8,9,?,8,9,6>1

gl$r&wEleent%(GL_TRKNGLE4,S,GL_UN4GNE$_BJTE,in2ice%)1

.oi2 gl$r&wEleent%(GLenu o2e, GL%i5ei count,GLenu t*pe, .oi2 - in2ice%)1

mode is the wa! !ou are drawing the elements.

count is the num%er of elements in the arra! of indices.

t!pe is the data t!pe of the indices arra!.indices is the arra! of indices.

5o not put gl5raw?lements in %etween a glEegin gl?nd pair.


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/nimation

•

Use double-buffer mode.•Render to one buffer, then to the other, swapping each time.

.oi2 2i%pl&* ( .oi2 )/gl:le&r (GL_:OLOR_BUFFER_BT)1

2r&w obCect% here

glut4w&pBuffer%()1>

int &in ()

/glutnit$i%pl&*#o2e (GLUT_$OUBLE 3 GLUT_RGB)1

>

Review 1 ====opengl I

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