1. OpenGL Shading Language (GLSL)

2. OpenGL Fixed Pipeline Vertex pipeline Transformation & Lighting
Viewport culling
&
clipping
Primitive
assembly
Rasterizer
setup
Pixel pipeline
Texture
blending
Per Fragment
operations
Buffer
operations
Framebuffer

3. Vertex Shader Vertex transformation
Normal transformation & normalization
Texture coordinate generation & transformation
Per-vertex lighting
Transformation
& Lighting
Primitive
assembly
Viewport culling
& clipping
Vertex
processor
Rasterizer
setup

4. Geometry Shader Add/remove primitives Add/remove vertices
Edit vertex position
Supported by OpenGL Extension (Glew 1.4+) or DX10
Stream
output
Vertex
processor
Primitive
assembly
Viewport culling
& clipping
Geometry
processor
Rasterizer
setup

5. Fragment (pixel) Shader
Operations on interpolated values
Texture access
Texture application
Fog
Color sum
Rasterizer
setup
Texture
blending
Per Fragment
operations
Buffer
operations
Fragment
processor

6. Programmable Pipeline
Vertex pipeline
Viewport culling
&
clipping
Vertex
Shader
Geometry
Shader
Rasterizer
setup
Pixel pipeline
Pixel
Shader
Per Fragment
operations
Buffer
operations
Framebuffer

7. Qualifiers Used to management the input and output of shaders.
attribute
Communicate frequently changing variables from the application to a vertex shader.
uniform
Communicate infrequently changing variables from the application to any shader.
varying
Communicate interpolated variables from a vertex shader to a fragment shader

8. Qualifiers in Pipeline
(x,y,z)
(x’,y’,z’)
Vertex
Shader
Fragment Shader
attribute
rasterizer
Buffer Op…
varying
varying
uniform

9. Qualifiers in Pipeline
(x,y,z)
Vertex
Shader
Geometry
Shader
Fragment Shader
attribute
rasterizer
varying in
varying out
uniform

10. Vertex Shader Vertex processer Build-in Uniform: gl_ModelviewMatrix
Build-in Attributes:
gl_Color
gl_Normal
gl_Vertex
gl_MultiTexCoord0
gl_MultiTexCoord1 …
User-defined Attributes:
Tangent
Bitangent …
Build-in Uniform:
gl_ModelviewMatrix
gl_ProjectionMatrix
gl_LightSource[0~n]
gl_FrontMaterial …
User-defined Uniform:
Texture
EyePosition
Time
ScaleValue …
Vertex
processer
Build-in Varying:
gl_FrontColor
gl_TexCoord[0~n] …
Special Output:
gl_Position
gl_PointSize …
User-defined Varying:
normal
tangent …

11. Fragment Shader Fragment processer Build-in Varying: gl_TexCoord[0~n]
gl_FragCoord
gl_FrontColor …
User-defined Varying:
normal
tangent …
Build-in Uniform:
gl_ModelviewMatrix
gl_ProjectionMatrix
gl_LightSource[0~n]
gl_FrontMaterial …
User-defined Uniform:
Texture
EyePosition
Time
ScaleValue …
Fragment
processer
Special Output:
gl_FragColor / gl_FragData[]
gl_FragDepth

12. Geometry Shader Geometry processor Coord. gl_Position gl_TexCoord[];
Vertex Color
gl_FrontColorIn[gl_VerticesIn];
gl_BackColorIn[gl_VerticesIn];
gl_FrontSecondaryColorIn[gl_VerticesIn];
gl_BackSecondaryColorIn[gl_VerticesIn];
gl_FogFragCoordIn[gl_VerticesIn];
Vertex Coord.
gl_TexCoordIn[gl_VerticesIn][];
gl_PositionIn[gl_VerticesIn];
Resterization Info.
gl_PointSizeIn[gl_VerticesIn];
gl_ClipVertexIn[gl_VerticesIn];
Geometry
processor
Number of Vertices
gl_VerticesIn
Color
gl_FrontColor;
gl_BackColor;
gl_FrontSecondaryColor;
gl_BackSecondaryColor;
gl_FogFragCoord;
Coord.
gl_Position
gl_TexCoord[];

13. GLSL Language Definition
Data Type Description
int Integer
float Floating-point
bool Boolean (true or false).
vec2 Vector with two floats.
vec3 Vector with three floats.
vec4 Vector with four floats.
mat2 2x2 floating-point matrix.
mat3 3x3 floating-point matrix.
mat4 4x4 floating-point matrix.

14. Vector Vector is like a class You can use following to access Example:
.r .g .b .a
.x .y .z .w
.s .t .p .q
Example:
vec4 color;
color.rgb = vec3(1.0 , 1.0 , 0.0 ); color.a = 0.5
or color = vec4(1.0 , 1.0 , 0.0 , 0.5);
or color.xy = vec2(1.0 , 1.0); color.zw =vec2(0.0 , 0.5);

15. Texture Sampler sampler*DShadow sampler{1,2,3}D sampler{1,2}DShadow
samplerCube
Texture unit to access the content of texture.
sampler*DShadow
The depth texture for shadow map.
The cube map.

16. Addition Information Array Static cast by function Similar to C.
No union, enum, class
Static cast by function
float()
int()

17. Phong Shading
Use varying variable to save the vertex normal or other information.
Compute the Phong lighting in pixel shader with the information.

18. Vertex Shader Code Example
varying vec3 normal, lightDir, eyeDir;
void main() {
normal = gl_NormalMatrix * gl_Normal;
vec3 vVertex = vec3(gl_ModelViewMatrix * gl_Vertex);
lightDir = vec3(gl_LightSource[0].position.xyz - vVertex);
eyeDir = -vVertex;
gl_Position = ftransform();
//gl_Position = gl_ProjectionMatrix*gl_ModelViewMatrix*gl_Vertex; }

19. Fragment Shader Code Example
varying vec3 normal, lightDir, eyeDir;
void main (void) {
vec4 final_color =
(gl_FrontLightModelProduct.sceneColor * gl_FrontMaterial.ambient) +
(gl_LightSource[0].ambient * gl_FrontMaterial.ambient);
vec3 N = normalize(normal);
vec3 L = normalize(lightDir);
float lambertTerm = dot(N,L);
if(lambertTerm > 0.0){
final_color += gl_LightSource[0].diffuse * gl_FrontMaterial.diffuse * lambertTerm;
vec3 E = normalize(eyeDir);
vec3 R = reflect(-L, N);
float specular = pow( max(dot(R, E), 0.0), gl_FrontMaterial.shininess );
final_color += gl_LightSource[0].specular * gl_FrontMaterial.specular * specular; }
gl_FragColor = final_color;

20. OpenGL Gouraud Shading
Result
OpenGL Gouraud Shading
GLSL Phong Shading

21. Geometry Shader It can change the primitive. Application
Add/remove primitives
Add/remove vertices
Edit vertex position
Application

22. Geometry Shader Example Code
void main(void) { vec2 lineDir = gl_PositionIn[1].xy - gl_PositionIn[0].xy; vec2 normal = vec2(-lineDir.y, lineDir.x); //CCW 90 degree vec4 v[4]; v[0] = gl_PositionIn[1]; v[1] = gl_PositionIn[1]; v[2] = gl_PositionIn[0]; v[3] = gl_PositionIn[0]; v[0].xy -= normal*0.125; v[1].xy += normal*0.125; v[2].xy += normal*0.125; v[3].xy -= normal*0.125;

23. gl_Position = v[0]; EmitVertex(); gl_Position = v[1]; gl_Position = v[2]; gl_Position = v[3]; EndPrimitive(); // GL_LINE_STRIP }

24. Original input primitive
Result
Original input primitive
Output primitive

25. New Input Primitives GL_LINES_ADJACENCY GL_LINE_STRIP_ADJACENCY
GL_TRIANGLES_ADJACENCY
GL_TRIANGLE_STRIP_ADJECENCY

26. Applications

27. Applications

28. Use GLSL in OpenGL glew.h glew32.lib glew32.dll
You need those head and library files
glew.h
glew32.lib
glew32.dll

29. Use the Shader Code in C/C++
Initialize the shader.
Use the shader you made.
Draw what you want.

30. Shader Initialization
Vertex Shader
glCreateShade
Vertex
Shader Code
glShaderSource
glCreateProgram
glCompileShader
glAttachShader
Fragment Shader
glAttachShader
glCreateShade
glLinkProgram
Fragment
Shader Code
glShaderSource
glUseProgram
glCompileShader

31. Part of Example Code (C++)
int main(int argc, char **argv) { glutInit(&argc, argv); glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGBA); glutInitWindowPosition(100,100); glutInitWindowSize(320,320); glutCreateWindow("GPU"); . glewInit(); setShaders(); glutMainLoop(); return 0; }

32. void setShaders() { //a few strings // will hold onto the file read in
void setShaders() { //a few strings // will hold onto the file read in! char *vs = NULL, *fs = NULL, *gs = NULL; //First, create our shaders v = glCreateShader(GL_VERTEX_SHADER); f = glCreateShader(GL_FRAGMENT_SHADER); g = glCreateShader(GL_GEOMETRY_SHADER_EXT); //Read in the programs vs = textFileRead("../GeometryShader/ShaderCode/shader.vert"); fs = textFileRead("../GeometryShader/ShaderCode/shader.frag"); gs = textFileRead("../GeometryShader/ShaderCode/shader.geom");

33. //Setup a few constant pointers for below const char
//Setup a few constant pointers for below const char * ff = fs; const char * vv = vs; const char * gg = gs; glShaderSource(v, 1, &vv, NULL); glShaderSource(f, 1, &ff, NULL); glShaderSource(g, 1, &gg, NULL); free(vs);free(fs);free(gs); glCompileShader(v); glCompileShader(f); glCompileShader(g); p = glCreateProgram();

34. glAttachShader(p,f); glAttachShader(p,v); glAttachShader(p,g); glProgramParameteri(p,GL_GEOMETRY_INPUT_TYPE,GL_LINES); glProgramParameteri(p,GL_GEOMETRY_OUTPUT_TYPE,GL_LINE_STRIP); int temp; glGetIntegerv(GL_MAX_GEOMETRY_OUTPUT_VERTICES,&temp); glProgramParameteri(p,GL_GEOMETRY_VERTICES_OUT,temp); glLinkProgram(p); glUseProgram(p); }

35. Multi-texture Pixel Color Op 0 Op 1 Op 2 Op n final color
glActiveTexture( GL_TEXTURE0 );
glEnable(GL_TEXTURE_2D);
glBindTexture(GL_TEXTURE_2D, …);
Op 1
glActiveTexture( GL_TEXTURE1 );
glEnable(GL_TEXTURE_2D);
glBindTexture(GL_TEXTURE_2D, …);
Op 2
glActiveTexture( GL_TEXTURE2 );
glEnable(GL_TEXTURE_2D);
glBindTexture(GL_TEXTURE_2D, …);
Op n
final color
glActiveTexture( GL_TEXTUREn );
glEnable(GL_TEXTURE_2D);
glBindTexture(GL_TEXTURE_2D, …);

36. Shader Get location by name Assign layer number final color
glActiveTexture( GL_TEXTURE0 );
glBindTexture(GL_TEXTURE_2D, …);
glActiveTexture( GL_TEXTURE1 );
glBindTexture(GL_TEXTURE_2D, …);
final color
glActiveTexture( GL_TEXTURE2 );
glBindTexture(GL_TEXTURE_2D, …);
glActiveTexture( GL_TEXTURE3 );
glBindTexture(GL_TEXTURE_2D, …);

37. The Setting of Texture Operative Ignored
glActiveTexture / glBindTexture
MAG and MIN Filter
GL_NEAREST, GL_LINEAR, GL_LINEAR_MIPMAP_LINEAR, …
WRAP S, T
GL_CLAMP, GL_REPEAT, GL_CLAMP_TO_EDGE, GL_CLAMP_TO_BORDER
Ignored
glEnable(GL_TEXTURE_nD) / glDisable
GL_TEXTURE_ENV_MODE
GL_REPLACE, GL_MODULATE, GL_ADD
Pixel Color
Op 0
glActiveTexture( GL_TEXTURE0 );
glEnable(GL_TEXTURE_2D);
glBindTexture(GL_TEXTURE_2D, …);

38. Send Texture to Shader Active texture channel Bind the texture
Get location of the variable in shader
Set the value

39. Get Location
Glint glGetUniformLocation(GLhandleprogram, const GLchar *name)
– Return an integer to represent the location of a specific uniform variable.
– name is the name of the uniform variable in the shader.
– The location of a variable is assigned in link time, so this function should be called after the link stage.

40. Set Value
Following functions are used to assign values for uniform variables
– Void glUniform{1,2,3,4}{f,i}(Glint location, TYPE v)
– Void glUniform{1,2,3,4}{f,i}v(Glint location, Gluint count, TYPE v)
– Void glUniformMatrix{2,3,4}fv(Glint location,GLuint count, GLboolean transpose, const GLfloat *v)
location is the value obtained using glGetUniformLocation().
v is the value to be assigned.
glUniform1i can be used to assign texture slot of glActiveTexture.

41. Texture Mapping C++ Code
glUseProgramObject(MyShader); glActiveTexture( GL_TEXTURE0 ); glBindTexture(GL_TEXTURE_2D, texObject[0]); GLint location = glGetUniformLocation(MyShader, "colorTexture"); if(location == -1) printf("Cant find texture name: colorTexture\n"); else glUniform1i(location, 0); int i,j; for (i=0;i < object->fTotal;i++){ glBegin(GL_POLYGON); for (j=0;j<3;j++){ glMultiTexCoord2fv(GL_TEXTURE0, object->tList[object->faceList[i][j].t].ptr); glNormal3fv(object->nList[object->faceList[i][j].n].ptr); glVertex3fv(object->vList[object->faceList[i][j].v].ptr); } glEnd(); glutSwapBuffers(); glutPostRedisplay();

42. Texture Mapping Vertex Shader Code
void main() { gl_TexCoord[0].xy = gl_MultiTexCoord0.xy; gl_Position = ftransform(); }

43. Texture Mapping Pixel Shader Code
uniform sampler2D colorTexture; void main (void) { gl_FragColor = texture2D(colorTexture,gl_TexCoord[0].xy).rgba; }

44. gl_TexCoord[0]
Vertex
Shader
Fragment Shader
(colorTexture)
gl_MultiTexCoord0
rasterizer
glGetUniformLocation
glActiveTexture
glBindTexture(..)
GL_TEXTURE0
location
glUniform1i(location, 0); id
GL_TEXTURE1
Texture
Content …
GL_TEXTUREn

45. Result 2

46. Send Attribute Data You can use glMultiTexCoord instead.
It is similar to uniform data.
Get location
glGetAttribLocation(program id, variable name)
Set Values Per Vertex
Set by glVertexAttrib{234}{fd}{v}
Call glVertex{34}{fd}{v}
You can use glMultiTexCoord instead.