GL2 Shading Language

GL2 Shading Language 

Bill Licea-Kane 

Licea Kane 

ATI Research, Inc. 

bill@ati bill@ati.com 

.com

GL2 GL2 Shading Shading Language 

Language 

Back Back to to the the future 

future 

“As As far as generating pictures from data is concerned, we 

feel the display processor should be a specialized device, 

capable only of generating pictures from read-only read only 

representations in core.” 

Myer and Sutherland, On the Design of Display Processors. 

Communications of the ACM, Volume 11 Number 6, June, 1968




future 

• June June 30, 30, 1992 

1992 

– OpenGL OpenGL 1.0 1.0 Final Final Draft Draft published 

published




future 

“OpenGL OpenGL does not provide a programming language. Its 

function may be controlled by turning operations on or off or 

specifying parameters to operations, but the rendering 

algorithms are essentially fixed. One reason for this decision 

is that, for performance reasons, graphics hardware is usually 

designed to apply certain operations in a specific order; 

replacing these operations with arbitrary algorithms is 

usually infeasible. Programmability would conflict with 

keeping the API close to the hardware and thus with the goal 

of maximum performance.” 

Segal and Akeley, Akeley, 

The The Design Design of of the the OpenGL OpenGL Graphics Graphics 

Interface, Interface, 

1994




future 

• August August 23, 23, 1993 

1993 

– First First OpenGL OpenGL 1.0 1.0 implementation implementation ships 

ships




future 

billa@entropy. 

billa@entropy.sps 

sps.mot.com .mot.com (William C. Archibald) writes: 

|> 1)Quite a few modern rendering techniques and renderers 

|> support shader function calls at arbitrary points 

|> across a surface being rendered. ... What I would 

|> _like_ to do is call the shader at visible 

|> (front-facing) (front facing) points. Is there _any_ way to do 

|> this kind of thing in OpenGL? 

Not with the current API. One could extend OpenGL in this 

manner... 

Akeley, Akeley, 

comp.graphics.opengl 

comp.graphics. opengl posting, 13 Oct 1993



Back Back to to the the present 

present 

• February February 27, 27, 2003 

2003 

– arb-gl2 arb gl2 workgroup publishes 

Draft Draft OpenGL Shading Language 

– End End construction construction zone 

zone



Today 

Today 

• How How we we replace replace Fixed Fixed Function 

Function 

• Review Review Shading Shading Language 


• Shading Shading Language Language examples 

examples 

• Procedural Procedural Shader Shader demo 

demo

Vertex (object) 

Normal 

Color 

SecondaryColor 

TexCoord TexCoordnn 

EdgeFlag 

OpenGL 

Fixed Function Vertex 

Transform 

[MVP],[MV],[MV] -T 

[MVP],[MV],[MV] 

Lighting 

Texgen Texture 

Matrix Matrixnn 

[0,1] 

[0,1] 

Vertex (clip) 

Vertex (eye) 

Front&Back 

Color 

Front&Back 



EdgeFlag

Vertex (object) 

Normal 

Color 



EdgeFlag 

GL2 Vertex Processor 

Uniform 

Vertex 

Shader 

Temporaries 

Vertex (clip) 

Vertex (eye) 

Front&Back 

Color 

Front&Back 



EdgeFlag

Vertex 

Normal 

Color 


MultiTexCoord 

MultiTexCoordnn 

EdgeFlag 


Names 

Uniform 

Vertex 

Shader 

Temporaries 

Position 

ClipVertex 

Front&Back 

Color 

Front&Back 


TexCoord[nn] 

TexCoord 

EdgeFlag

Vertex 

Normal 

Color 


MultiTexCoord 

MultiTexCoordnn 

EdgeFlag 


Add Fog Coordinate 

Uniform 

Vertex 

Shader 

Temporaries 

Position 

ClipVertex 

Front&Back 

Color 

Front&Back 


FogCoord FogFragCoord 

TexCoord[nn] 

TexCoord 

EdgeFlag

Attribute0 

Attribute1 

Attribute2 

… 

Attribute Attributenn 


Generalize Input 

Uniform 

Vertex 

Shader 

Temporaries 

Position 

ClipVertex 

Front&Back 

Color 

Front&Back 


FogFragCoord 

TexCoord[nn] 

TexCoord 

EdgeFlag EdgeFlag

Attribute0 

Attribute1 

Attribute2 

… 


EdgeFlag 


Generalize Output 

Uniform 

Vertex 

Shader 

Temporaries 

Position 

ClipVertex 

Varying0 

Varying1 

Varying2 

… 

Varying Varyingnn 

EdgeFlag

Attribute0 

Attribute1 

Attribute2 

… 


EdgeFlag 


Additional Output 

Uniform 

Vertex 

Shader 

Temporaries 

Position 

ClipVertex 

PointSize 

Varying0 

Varying1 

Varying2 

… 


EdgeFlag

GL2 Vertex Limits 

Active Attributes (16 vec4) 

Attribute0 

Attribute1 

Attribute2 

… 


EdgeFlag 

Uniform 

Vertex 

Shader 

Temporaries 

Position 

ClipVertex 

PointSize 

Varying0 

Varying1 

Varying2 

… 


EdgeFlag

Attribute0 

Attribute1 

Attribute2 

… 


EdgeFlag 


Uniform (512 words) 

Uniform 

Vertex 

Shader 

Temporaries 

Position 

ClipVertex 

PointSize 

Varying0 

Varying1 

Varying2 

… 


EdgeFlag

Attribute0 

Attribute1 

Attribute2 

… 


EdgeFlag 


Varying (32 floats) 

Uniform 

Vertex 

Shader 

Temporaries 

Position 

ClipVertex 

PointSize 

Varying0 

Varying1 

Varying2 

… 


EdgeFlag

Attribute0 

Attribute1 

Attribute2 

… 


EdgeFlag 


Instructions (Virtual) 

Uniform 

Vertex 

Shader 

Temporaries 

Position 

ClipVertex 

PointSize 

Varying0 

Varying1 

Varying2 

… 


EdgeFlag

Attribute0 

Attribute1 

Attribute2 

… 


EdgeFlag 


Temporaries (Virtual) 

Uniform 

Vertex 

Shader 

Temporaries 

Position 

ClipVertex 

PointSize 

Varying0 

Varying1 

Varying2 

… 


EdgeFlag

Attribute0 

Attribute1 

Attribute2 

… 


EdgeFlag 


Texture Units (1) 

Uniform 

Vertex 

Shader 

Temporaries 

Texture 

Position 

ClipVertex 

PointSize 

Varying0 

Varying1 

Varying2 

… 


EdgeFlag

Position 

Position 

Position 

ClipVertex 

ClipVertex 

ClipVertex 




EdgeFlag 

EdgeFlag 

EdgeFlag 

OpenGL 

Fixed Function Rasterization 

RasterPos 


Primitive 

Assembly 

Flatshade 

Culling or 

Clipping 

Face 

Processing 

Point 

Line 

Polygon 

Rasterization 

Pixel Rectangle 

Bitmap 

Rasterization 


Coord

Color 

OpenGL 

Fixed Function Fragment 


TexCoord[nn] 

TexCoord 

z(|ze |,f ) 

Depth 

Coord 

FrontFacing 

Tex 

nn 

TE 

nn 

Sum Fog 

[0,1] 

Color 

Depth 

Coord 

FrontFacing

Color 

TexCoord[nn] 

TexCoord 

z(|ze |,f ) 

Coord 

FrontFacing 

GL2 Fragment Processor 


Uniform Texture 

Fragment 

Shader 

Color 

Depth Depth 

Temporaries 

Coord 

FrontFacing

Color0 

Color1 

TexCoord[nn] 

TexCoord 

FogFragCoord 

FragCoord 

FrontFacing 


Names 


Fragment 

Shader 

FragColor 

FragDepth FragDepth 

Temporaries 

FragCoord 

FrontFacing

Varying0 

Varying1 

Varying2 

FragCoord 

FrontFacing 


… 


Generalize Input 


Fragment 

Shader 

FragColor 


Temporaries 

FragCoord 

FrontFacing

Varying0 

Varying1 

Varying2 

… 


FragCoord 

FrontFacing 

GL2 Fragment Limits 

Uniforms (64 words) 


Fragment 

Shader 

FragColor 


Temporaries 

FragCoord 

FrontFacing

Varying0 

Varying1 

Varying2 

… 


FragCoord 

FrontFacing 


Varying (32 floats) 


Fragment 

Shader 

FragColor 


Temporaries 

FragCoord 

FrontFacing

Varying0 

Varying1 

Varying2 

… 


FragCoord 

FrontFacing 


Instructions (virtual) 


Fragment 

Shader 

FragColor 


Temporaries 

FragCoord 

FrontFacing

Varying0 

Varying1 

Varying2 

… 


FragCoord 

FrontFacing 


Temporaries (virtual) 


Fragment 

Shader 

FragColor 


Temporaries 

FragCoord 

FrontFacing

Varying0 

Varying1 

Varying2 

… 


FragCoord 

FrontFacing 


Texture Units (2) 


Fragment 

Shader 

FragColor 


Temporaries 

FragCoord 

FrontFacing

Varying0 

Varying1 

Varying2 

FragCoord 

FrontFacing 


Fragment Output (fixed) 

… 



Fragment 

Shader 

FragColor 


Temporaries 

FragCoord 

FrontFacing



Today 

Today 


Function 




examples 


demo

# 

#define 

#undef 

undef 

#if 

#ifdef 

ifdef 

#ifndef 

ifndef 

#else 

#elif 

elif 

#endif 

endif 



Preprocessor Preprocessor directives 

directives 

#error 

#pragma 

pragma optimize(on|off) 

#pragma 

pragma debug(on|off) 

#line line file 

__LINE__ 

__FILE__ 

__VERSION__ 

// comment 

/* comment */

• void 



Types 

Types 

• float vec2 vec3 vec4 

• mat2 mat3 mat4 

• int ivec2 ivec2 ivec3 ivec3 ivec4 

• bool bvec2 bvec2 bvec3 bvec3 bvec4 

bvec4 

• samplernnD sampler samplernD D samplerCube samplerCube samplerShadownnD 

samplerShadownD 

samplerShadow



Types 

Types 

• struct struct (with (with some some minor minor restrictions) 

restrictions) 

– No No qualifiers 

qualifiers 

– No No bit bit fields 

fields 

– No No forward forward references 

references 

– No No in-place in-place in place definitions 

definitions 

– No anonymous structures



Types 

Types 

• arrays arrays ( ( with with some some minor minor restrictions) 

restrictions) 

– one one dimensional 

dimensional 

– size size is is integral integral constant constant expression 

expression 

– can can declare unsized unsized array, array, but… 

– specify size and type of array ONCE 

– any basic basic type type and and struct 

struct 

– NO initialization at declaration



Reserved Reserved Types 

Types 

• half half hvec2 hvec2 hvec3 hvec3 hvec4 

hvec4 

• fixed fixed fvec2 fvec2 fvec3 fvec3 fvec4 

fvec4 

• double double dvec2 dvec2 dvec3 dvec3 dvec4 

dvec4 

• sampler2DRect sampler2DRect sampler3DRect 

sampler3DRect

• global 

global 



– outside outside function 

function 

Scope 

Scope 

– shared shared globals globals must must be same type 

• local local (nested) 

(nested) 

– within within function function definition 

definition 

– within within function 

function 

– within within compound compound statement 

statement



• const 

const 

• attribute 

attribute 

• uniform 

uniform 

• varying 

varying 

• (default) 

(default) 

Type Type Qualifiers 

Qualifiers



• grouping: grouping: () 

() 

• array array subscript: subscript: [] 

[] 

Operators 

Operators 

• function function call call and and constructor: constructor: () 

() 

• field field selector selector and and swizzle: swizzle: . 

. 

• postfix: postfix: ++ -- 

-- 

• prefix: prefix: ++ ++ -- -- + + - !



Operators 

Operators 

• binary: binary: * * / / + + - 

• relational: relational: < < >= 

>= 

• equality: equality: == == != 

!= 

• logical: logical: && && ^^ ^^ || 

|| 

• selection: selection: ?: 

?: 

• assignment: assignment: = *= /= += -=



• prefix: prefix: ~ 

~ 

• binary: binary: % 

% 

Reserved Reserved Operators 

Operators 

• bitwise: bitwise: 

& & ^ ^ | 

| 

• assignment: assignment: %= %= = &= &= ^= ^= |= 

|=

• float() 

float() 

• int() 

int() 

• bool() 

bool() 



• vec2() vec2() vec3() vec3() vec4() 

vec4() 

Constructors 

Constructors 

• mat2() mat2() mat3() mat3() mat4() 

mat4()



Scalar Scalar Constructors 

Constructors 

float f; int i; bool b; 

float( b) // b=true?1.0:0.0; 

int( int( 

b) // b=true?1:0; 

bool( bool( 

b) // identity 

float( i) // int to float 

int( int( 

i) // identity 

bool( bool( 

i) // i!=0?true:false; 

float( f) // identity 

int( int( 

f) // float to int 

bool( bool( 

f) // f!=0.0?true:false;



Vector Vector Constructors 

Constructors 

vec2 v2; vec3 v3; vec4 v4; 

vec2( 1.0 ,2.0) 

vec3( 0.0 ,0.0 ,1.0) 

vec4( 1.0 ,0.5 ,0.0 ,1.0) 

vec4( 1.0) // all 1.0 

vec4( v2 ,v2) // different... 

vec4( v3 ,1.0) // ...types 

vec2( v4) 

float( v4)



Matrix Matrix Constructors 

Constructors 

vec4 v4; mat4 m4; 

mat4( 1.0, 2.0, 3.0, 4.0, 

5.0, 6.0, 7.0, 8.0, 

9.0, 10., 11., 12., 

13., 14., 15., 16.) // row major 

mat4( v4, v4, v4, v4) 

mat4( 1.0) // identity matrix 

mat3( m4) // upper 3x3 

vec4( m4) // 1st column 

float( m4) // upper 1x1



Structure Structure Constructors 

Constructors 

struct light { 

float intensity; 

vec3 position; 

} 

light headLight = light( 0.2 

,vec3( 0.0 ,0.0, 1.0)); 

// same as 

light headLight; 

headLight 

headLight.intensity headLight.intensity 

= 0.2; 

headLight.position headLight.position 

= vec3( 0.0 ,0.0, 1.0);



Components 

Components 

• component component accessor for vectors 

– xyzw xyzw rgba rgba stpq stpq [i] 

[i] 

• component component accessor for matrices 

– [i] [i] [i][j] 

[i][j]

vec2 v2; 

vec3 v3; 

vec4 v4; 



Vector Vector components 

components 

v2.x // is a float 

v2.z // wrong: component undefined for type 

v4.rgba v4. rgba // is a vec4 

v4.stp v4. stp // is a vec3 

v4.b // is a float 

v4.xy v4. xy // is a vec2 

v4.xgp v4. xgp // wrong: mismatched component sets



Vector Vector components components (r-value) 

(r value) 

vec2 v2; 

vec3 v3; 

vec4 v4; 

v4.wzyx v4. wzyx // swizzles, is a vec4 

v4.bgra v4. bgra // swizzles, is a vec4 

v4.xxxx v4. xxxx // smears x, is a vec4 

v4.xxx v4. xxx // smears x, is a vec3 

v4.yyxx v4. yyxx // duplicates x and y, is a vec4 

v2.yyyy v2. yyyy // wrong: too many components for type



Vector Vector components components (l-value) 

(l value) 

vec4 v4 = vec4( 1.0, 2.0, 3.0, 4.0); 

v4.xw v4. xw = vec2( 5.0, 6.0); // (5.0, 2.0, 3.0, 6.0) 

v4.wx v4. wx = vec2( 7.0, 8.0); // (8.0, 2.0, 3.0, 7.0) 

v4.xx v4. xx = vec2( 9.0,10.0); // wrong: x used twice 

v4.yz v4. yz = 11.0; // wrong: type mismatch 

v4.yz v4. yz = vec2( 12.0 ); // (8.0,12.0,12.0, 7.0)



Vector Vector components components (array) 

(array) 

vec4 v4 = vec4( 1.0, 2.0, 3.0, 4.0); 

float f; 

int i; 

f = v4[0]; // 1.0 

f = v4[3]; // 4.0 

f = v4[4]; // undefined 

// ... 

f = v4[i+1]; // defined for -1



Matrix Matrix components components (array) 

(array) 

mat4 m4; 

m4[1] = vec4(2.0); // 2nd column = 2.0 

m4[0][0] = 1.0; // upper 1x1 = 1.0 

m4[4][4] = 3.0; // undefined



vec3 v3[2]; 

mat3 m3[2]; 

Components Components (arrays) 

(arrays) 

v3[0] // is a vec3 

v3[0][0] // is a float 

V3[0].x // is a float 

m3[0] // is a mat3 

m3[0][0] // is a vec3, 1st column 

m3[0][0][0] // is a float, upper 1x1 

// :-(



Vector Vector and and Matrix Matrix Operations 

Operations 

mat4 m4,n4; 

vec4 v4 

v4 * m4 // is a vec4 

m4 * n4 // is a mat4



Flow-control Flow control (scalar) 

(scalar) 

• expression expression ? trueExpression : falseExpression 

• if, if-else if if-else else 

• for, for, while, while, do-while 

do while 

• return, break, continue 

continue 

• discard (fragment only)



User-defined User defined functions 

functions 

• Call Call by by value-return 

value return 

• in in out inout keywords 

• Function Function overloading 

overloading 

• One One return return value value (can (can be be any any type) 

type) 

• Scope Scope rules rules same same as as C 

C



Built-in Built in Vertex Vertex Special 

Special 

vec4 gl_Position; 

gl_Position; 

// must be written 

vec4 gl_ClipPosition 

gl ClipPosition; ; // may be written 

float gl_PointSize 

gl PointSize; ; // may be written



Built-in Built in Fragment Fragment Special 

Special 

bool gl_FrontFacing 

gl FrontFacing; ; // may be read 

float gl_FragColor 

gl FragColor; ; // may be written 

float gl_FragDepth 

gl FragDepth; ; // may be read/written 

float gl_FragStencil 

gl FragStencil; ; // may be read/written 

vec4 gl_FragData 

gl FragDatan; ; // may be written 

vec4 gl_FragCoord 

gl FragCoord; ; // may be read 

vec4 gl_FBColor 

gl FBColor; ; // may be read 

float gl_FBDepth 

gl FBDepth; ; // may be read 

float gl_FBStencil 

gl FBStencil; ; // may be read 

vec4 gl_FBData 

gl FBDatan; ; // may be read



Built-in Built in Attributes 

Attributes 

// Vertex Attributes, p. 19 

attribute vec4 gl_Vertex; 

gl_Vertex; 

attribute vec3 gl_Normal; 

gl_Normal; 

attribute vec4 gl_Color; 

gl_Color; 

attribute vec4 gl_SecondaryColor 

gl SecondaryColor; 

attribute vec4 gl_MultiTexCoord 

gl MultiTexCoordn; 

attribute float gl_FogCoord 

gl FogCoord;



User-defined User defined Attributes 

Attributes 

attribute vec3 myTangent; 

myTangent 

attribute vec3 myBinormal; 

myBinormal 

attribute float myTemperature; 

myTemperature 

attribute float myPressure; 

myPressure 

attribute float myRainfall; 

myRainfall 

attribute float myTime; myTime 

// etc...



Built-in Built in Constants 

Constants 

// Implementation dependent constants 

// Minimum Maximums 

const int gl_MaxLights 

gl MaxLights = 8; 

const int gl_MaxClipPlanes 

gl MaxClipPlanes = 6; 

const int gl_MaxTextureUnits 

gl MaxTextureUnits = 2; 

const int gl_MaxTextureCoordsARB 

gl MaxTextureCoordsARB = 2; 

// GL2 Minimum Maximums 

const int gl_MaxVertexAttributesGL2 gl_MaxVertexAttributesGL2 

= 16; 

const int gl_MaxVertexUniformWordsGL2 gl_MaxVertexUniformWordsGL2 

= 512; 

const int gl_MaxVaryingFloatsGL2 gl_MaxVaryingFloatsGL2 

= 32; 

const int gl_MaxVertexTextureUnitsGL2 gl_MaxVertexTextureUnitsGL2 

= 1; 

const int gl_MaxFragmentTextureUnitsGL2 gl_MaxFragmentTextureUnitsGL2 

= 2; 

const int gl_MaxFragmentUniformWordsGL2 gl_MaxFragmentUniformWordsGL2 

= 64;



Built-in Built in uniforms 

uniforms 

// Matrix state, p. 31, 32, 37, 39, 40 

uniform mat4 gl_ModelViewMatrix 

gl ModelViewMatrix; 

uniform mat4 gl_ProjectionMatrix 

gl ProjectionMatrix; 

uniform mat4 gl_ModelViewProjectionMatrix 

gl ModelViewProjectionMatrix; 

uniform mat3 gl_NormalMatrix 

gl NormalMatrix; 

uniform mat4 gl_TextureMatrix 

gl TextureMatrix[n]; ]; 

// Normal scaling, p. 33 

uniform float gl_NormalScale 

gl NormalScale; 

// Depth range in window coordinates, p. 33 

struct gl_DepthRangeParameters 

gl DepthRangeParameters { 

float near; // n 

float far; // f 

float diff; // f – n 

}; 

uniform gl_DepthRangeParameters gl DepthRangeParameters gl_DepthRange 

gl DepthRange;




uniforms 

// Clip planes, p. 32 

uniform vec4 gl_ClipPlanes 

gl ClipPlanes[gl gl_MaxClipPlanes 

MaxClipPlanes] 

// Point Size, p. 66, 67 

struct gl_PointParameters 

gl PointParameters { 

float size; 

float sizeMin; sizeMin 

float sizeMax; sizeMax 

float fadeThreshold; 

fadeThreshold 

float distanceConstantAttenuation; 

distanceConstantAttenuation 

float distanceLinearAttenuation; 

distanceLinearAttenuation 

float distanceQuadraticAttenuation; 

distanceQuadraticAttenuation 

}; 

uniform gl_PointParameters gl PointParameters gl_Point; 

gl_Point;




uniforms 

// Material State, p. 50, 55 

struct gl_MaterialParameters 

gl MaterialParameters { 

vec4 emission; 

vec4 ambient; 

vec4 diffuse; 

vec4 specular; 

specular 

float shininess; 

}; 

uniform gl_MaterialParameters gl MaterialParameters gl_FrontMaterial 

gl FrontMaterial; 

uniform gl_MaterialParameters gl MaterialParameters gl_BackMaterial 

gl BackMaterial;




uniforms 

// Light State, p. 50, 53, 55 

struct gl_LightSourceParameters 

gl LightSourceParameters { 

vec4 ambient; // Acli 

vec4 diffuse; // Dcli 

vec4 specular; 

specular; 

// Scli 

vec4 position; // Ppli 

vec4 halfVector; 

halfVector; 

// Derived: Hi 

vec3 spotDirection; 

spotDirection; 

// Sdli 

float spotExponent; 

spotExponent; 

// Srli 

float spotCutoff; 

spotCutoff; 

// Crli ([0.0,90.0],180.0) 

float spotCosCutoff; 

spotCosCutoff; 

// Derived: cos(Crli cos Crli) ) ([1.0, 0.0],-1.0) 

0.0], 1.0) 

float constantAttenuation // K0 

float linearAttenuation // K1 

float quadraticAttenuation // K2 

}; 

uniform gl_LightSourceParameters gl LightSourceParameters gl_LightSource 

gl LightSource[gl gl_MaxLights 

MaxLights]; ];




uniforms 

struct gl_LightModelParameters 

gl LightModelParameters { 

vec4 ambient; // Acs 

}; 

uniform gl_LightModelParameters gl LightModelParameters gl_LightModel 

gl LightModel; 

struct gl_LightModelProducts 

gl LightModelProducts { 

vec4 }; 

sceneColor; 

sceneColor; 

// Ecm + Acm * Acs 

uniform gl_LightModelProducts gl LightModelProducts gl_FrontLightModelProduct 

gl FrontLightModelProduct; 

uniform gl_LightModelProducts gl LightModelProducts gl_BackLightModelProduct 

gl BackLightModelProduct; 

struct gl_LightProducts 

gl LightProducts { 

vec4 ambient; // Acm * Acl 

vec4 diffuse; // Dcm * Dcl 

vec4 }; 

specular; 

specular; 

// Scm * Scl 

uniform gl_LightProducts gl LightProducts gl_FrontLightProduct 

gl FrontLightProduct[gl gl_MaxLights 

MaxLights]; ]; 

uniform gl_LightProducts gl LightProducts gl_BackLightProduct 

gl BackLightProduct[gl gl_MaxLights 

MaxLights]; ];




uniforms 

// Texture Environment and Generation, p. 152, p. 40-42 40 42 

uniform vec4 gl_TextureEnvColor 

gl TextureEnvColor[gl gl_MaxFragmentTextureUnitsGL2]; 

_MaxFragmentTextureUnitsGL2]; 

uniform vec4 gl_EyePlaneS 

gl EyePlaneS[gl gl_MaxTextureCoordsARB 

MaxTextureCoordsARB] 

,gl gl_EyePlaneT 

EyePlaneT[gl gl_MaxTextureCoordsARB 


,gl gl_EyePlaneR 

EyePlaneR[gl gl_MaxTextureCoordsARB 


,gl gl_EyePlaneQ 

EyePlaneQ[gl gl_MaxTextureCoordsARB 

MaxTextureCoordsARB]; ]; 

uniform vec4 gl_ObjectPlaneS 

gl ObjectPlaneS[gl gl_MaxTextureCoordsARB 


,gl gl_ObjectPlaneT 

ObjectPlaneT[gl gl_MaxTextureCoordsARB 


,gl gl_ObjectPlaneR 

ObjectPlaneR[gl gl_MaxTextureCoordsARB 


,gl gl_ObjectPlaneQ 

ObjectPlaneQ[gl gl_MaxTextureCoordsARB 

MaxTextureCoordsARB]; ];




uniforms 

// Fog, p. 161 

struct gl_FogParameters 

gl FogParameters { 

vec4 color; 

float density; 

float start; 

float end; 

float scale; // 1.0/(end-start) 

1.0/(end start) 

}; 

uniform gl_FogParameters gl FogParameters gl_Fog; gl_Fog;



User-defined User defined uniforms 

uniforms 

uniform mat4 myGlobalMatrix; 

myGlobalMatrix 

uniform vec4 myAmbient; 

myAmbient 

uniform vec4 myDiffuseMatLight; 

myDiffuseMatLight 

uniform vec4 mySpecularMatLight; 

mySpecularMatLight 

uniform float myGlow; myGlow 

uniform vec4 myWarm; myWarm 

uniform vec4 myCool; myCool 

uniform float myCurrentTime; 

myCurrentTime 

// etc...

GL2 Shading Language 

gl_ModelViewMatrix 

gl ModelViewMatrix 

gl_NormalMatrix 

gl NormalMatrix; ; 

myWarm; myWarm 

myCurrentTime; 

myCurrentTime 

// etc... 

Uniforms 

Program Object 

Uniform Values 

Vertex 

Shader 

Fragment 

Shader



Built-in Built in varying 

varying 

varying vec4 gl_FrontColor 

gl FrontColor // vertex 

varying vec4 gl_BackColor 

gl BackColor; // vertex 

varying vec4 gl_FrontSecColor 

gl FrontSecColor; // vertex 

varying vec4 gl_BackSecColor 

gl BackSecColor; // vertex 

varying vec4 gl_Color; 

gl_Color; 

// fragment 

varying vec4 gl_SecondaryColor 

gl SecondaryColor; // fragment 

varying vec4 gl_TexCoord 

gl TexCoord[]; []; // both 

varying float gl_FogFragCoord 

gl FogFragCoord; // both



User-defined User defined varying 

varying 

varying vec3 myNormalPrime; 

myNormalPrime 

varying vec3 myTangentPrime; 

myTangentPrime 

varying vec3 myBinormalPrime; 

myBinormalPrime 

varying float myPressurePrime; 

myPressurePrime 

// etc...

GL2 GL2 Built-in Built in Functions 

Functions 

Angles Angles and and Trigonometry 

Trigonometry 

genType radians( genType degrees) 

genType degrees( genType radians) 

genType sin( genType angle) // radians 

genType cos( cos( 

genType angle) 

genType tan( genType angle) 

genType asin( asin( 


genType acos( acos( 


genType atan( atan( 

genType y ,genType , genType x) 

genType atan( atan( 

genType y_over_x)


Functions 

Exponentials, Exponentials, etc. 

etc. 

genType pow( pow( 

genType x ,genType , genType y) 

genType exp2( genType x) 

genType log2( genType x) 

genType sqrt( sqrt( 

genType x) 

genType inversesqrt( 

inversesqrt( 

genType x)


Functions 

Common 

Common 

genType abs( genType x) 

genType sign( genType x) 

genType floor( genType x) 

genType ceil( genType x) 

genType fract( fract( 

genType x)


Functions 

Common 

Common 

genType mod( genType x ,float y) 

genType mod( genType x ,genType , genType y) 

genType min( genType x ,genType , genType y) 

genType max( genType x ,genType , genType y) 

genType clamp( genType x 

,float v0, float v1) 

genType clamp( genType x 

,genType genType v0, genType v1)


Functions 

Interpolations 


// return x*( 1.0-a) 1.0 a) + y*a 

genType mix( genType x ,genType , genType y ,float a) 

genType mix( genType x ,genType , genType y ,genType , genType a) 

// x


Functions 



// genType t; 

// t = (x-edge0)/(edge1 

(x edge0)/(edge1-edge0); edge0); 

// t = clamp( t, 0.0, 1.0); 

// return t*t*(3.0-2.0*t); 

t*t*(3.0 2.0*t); 

genType smoothstep( smoothstep( 

float edge0 

,float edge1 

,genType genType x) 

genType smoothstep( smoothstep genType edge0 

,genType genType edge1 

,genType genType x)


Functions 

Geometric 

Geometric 

float length( genType x) 

float distance( genType p0 ,genType , genType p1) 

float dot( genType x ,genType , genType y) 

vec3 cross( vec3 x ,vec3 y) 

genType normalize( genType x) 

genType faceforward( 

faceforward( 

genType N 

,genType genType I 

,genType genType Nref) Nref 

genType reflect( genType I 

,genType genType N)


Functions 

Matrix 

Matrix 

mat matrixCompMult( matrixCompMult( 

mat x ,mat y)


Functions 

Vector Vector Relational 

Relational 

bGenType lessThan( 

lessThan( 


bGenType lessThanEqual( 

lessThanEqual( 

genType x 

,genType genType y) 

bGenType greaterThan( 

greaterThan( 


bGenType greaterThanEqual( 

greaterThanEqual( 

genType x 

,genType genType y) 

bGenType equal( genType x ,genType , genType y) 

bGenType notEqual( 

notEqual( 

genType x , genType y) 

bGenType not( genType x) 

bool any( bGenType x) 

bool all( bGenType x)


Functions 

Texture 

Texture 

vec4 texture1D( sampler1D sampler 

,float coord ,float bias) bias 


,vec2 coord ,float bias) bias 



vec4 textureCube( 

textureCube( 

samplerCube sampler 

,vec3 coord ,float bias) 

bias


Functions 

Texture 

Texture 

vec4 texture1DProj( sampler1D sampler 






vec4 textureCubeProj( 

textureCubeProj( 

samplerCube sampler 


bias


Functions 

Texture 

Texture 





bias


Functions 

Shadow 

Shadow 

vec4 shadow1D( samplerShadow1D sampler 


vec4 shadow2D( samplerShadow2D sampler 


vec4 shadow1DProj( samplerShadow1D sampler 


vec4 shadow2DProj( samplerShadow2D sampler 


bias


Functions 

vec4 ftransform() 

ftransform() 

Vertex 

Vertex 

// Example usage: 

gl_Position gl_Position 

= ftransform(); 

ftransform();


Functions 

Fragment 

Fragment 

genType dFdx( dFdx genType p) 

genType dFdy( dFdy( 

genType p) 

genType fwidth( fwidth( 

genType p)


Functions 

Noise 

Noise 

float noise1( genType coord) coord 

vec2 noise2( genType coord) coord 

vec3 noise3( genType coord) coord 

vec4 noise4( genType coord) 

coord



Today 

Today 


Function 




examples 


demo

GL2 GL2 Trivial Trivial Example 

Example 

Vertex Vertex Shader 

Shader 

varying vec3 Normal; // output 

#define MVP gl_ModelViewProjectionMatrix 

gl ModelViewProjectionMatrix 

#define MV gl_ModelViewMatrix 

gl ModelViewMatrix 

#define MV_IT gl_NormalMatrix 

gl NormalMatrix 

void main( void) // Vertex Shader 

{ 


= MVP * gl_Vertex; 

gl_Vertex; 

//gl // gl_ClipVertex 

ClipVertex = MV * gl_Vertex; 

gl_Vertex; 

Normal = normalize( MV_IT * gl_Normal); 

gl_Normal); 

}

GL2 GL2 Trivial Trivial Example 

Example 

Fragment Fragment Shader 

Shader 

varying vec3 Normal; // input 

uniform vec3 LightColor; LightColor // Light Color 

uniform vec3 LightPos; LightPos // Light Position 

void main( void) // Fragment Shader 

{ 

vec3 color = LightColor; 

LightColor 

color *= 

max(0.0,dot(normalize(Normal),LightPos 

max(0.0,dot(normalize(Normal), LightPos)); )); 

gl_FragColor 

gl FragColor = vec4( color,1.0); 

}

GL2 GL2 ToyBall ToyBall Example 

Example 

varying vec4 v_ObjPos v_ObjPos; 

varying vec4 v_EyePos v_EyePos; 

Vertex Vertex Shader 

Shader 

void main( void) // Vertex Shader 

{ 

vec4 ObjPos; ObjPos 

vec4 EyePos 

} 

ObjPos = gl_Vertex; 

gl_Vertex; 


= gl_ModelViewProjectionMatrix 

gl ModelViewProjectionMatrix * ObjPos; ObjPos 

v_ObjPos v_ObjPos 

= ObjPos; ObjPos 

EyePos = gl_ModelViewMatrix 

gl ModelViewMatrix * ObjPos; ObjPos 

v_EyePos v_EyePos 

= EyePos; EyePos


Example 

varying vec4 v_EyePos v_EyePos; 

varying vec4 v_ObjPos v_ObjPos; 


Shader 

uniform vec4 myLightDir; 

myLightDir; 

// NOTA BENE: please normalize 

uniform vec4 myEyeDir; 

myEyeDir; 

// (0.0, 0.0, 1.0, 0.0) 

uniform vec4 myHVector; 

myHVector 

uniform vec4 myEyeCenter; 

myEyeCenter


Example 


Shader 

uniform vec4 mySpecularColor; 

mySpecularColor 

uniform vec4 myRed, myRed, 

myYellow, myYellow myBlue; myBlue 

uniform vec4 myHalfSpace0; 





uniform vec4 toyBallConst; 

toyBallConst; 

// (-3.0, ( 3.0, 0.4, 0.0, 0.0) 

uniform vec4 one; 

uniform float myFWidth; 

myFWidth


Example 


Shader 

void main( void) // Fragment Shader 

{ 

vec4 NNormal; NNormal 

vec4 P; // The point in shader space 

vec4 SurfColor; 

SurfColor 

float Intensity; 

vec4 PDistance; 

PDistance 

float InOrOut; InOrOut 

P = v_ObjPos v_ObjPos; 

; // Analytically calculate P 

P.w = 0.0; 

P = normalize( P); 

P.w = 1.0;


Example 


Shader 

InOrOut = toyBallConst.x; 

toyBallConst.x; 

PDistance.x PDistance.x 

= dot( P, myHalfSpace0); // Fig 1 

PDistance.y PDistance.y 


PDistance.z PDistance.z 


PDistance.w PDistance.w 


PDistance = smoothstep( 

smoothstep( 

-myFWidth myFWidth, myFWidth, 

myFWidth, 

PDistance); 

PDistance); 

InOrOut += dot( PDistance, PDistance, 

one); 

PDistance.x PDistance.x 



= toyBallConst.y 

toyBallConst.y 

- abs( P.z); 

PDistance = smoothstep( 

smoothstep( 

-myFWidth myFWidth, myFWidth, 

myFWidth, 

PDistance); 

PDistance);


Example 


Shader 

InOrOut += PDistance.x; 

PDistance.x; 

// Fig 1 

InOrOut = clamp( InOrOut, InOrOut, 

0.0, 1.0); // Fig 2 

SurfColor = mix( myYellow, myYellow myRed, myRed, 

InOrOut); 

InOrOut); 

// Fig 3 

SurfColor = mix( SurfColor, SurfColor myBlue, myBlue, 


); // Fig 4


Example 


Shader 

// 

// Analytically calculate the sphere NNormal in eye coordinates 

NNormal = v_EyePos v_EyePos 

– myEyeCenter; 

myEyeCenter 

NNormal = normalize( NNormal); 

NNormal); 

// 

// Per fragment diffuse lighting 

Intensity = 0.2; // ambient 

Intensity += clamp( dot( myLightDir, 

myLightDir, 

NNormal), NNormal), 

0.0, 1.0) * 0.8; 

SurfColor *= Intensity; // Fig 1


Example 


Shader 

// 

// Per fragment specular lighting 

Intensity = clamp( dot( myHVector, 

myHVector, 

NNormal), NNormal), 

0.0, 1.0); 

Intensity = pow ( Intensity, mySpecularColor.a); 

mySpecularColor.a); 

} 

SurfColor += mySpecularColor * Intensity; // Fig 1 

SurfColor.a SurfColor.a 

= 1.0; 

gl_FragColor 

gl FragColor = SurfColor; 

SurfColor

GL2 GL2 ToyBall ToyBall Demo 

Demo



Questions? 

Questions? 


Function 



• Trivial Trivial Shading Shading Language Language example 

example 


demo 

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GL2 Shading Language

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