Shader

Original Rendering Pipeline

Vertex Shader

    Vertex transformation Normal transformation & normalization Texture coordinate generation & transformation Per-vertex processing

Fragment (pixel) Shader

    Operations on interpolated values Texture access Texture application Color sum

Shading languages

    DirectX ’ s High Level Shading Language NVidia ’ s Cg ATI ’ s RenderMonkey OpenGL Shading Language (GLSL)

Introduction of GLSL

   Data Type Vertex Shader Fragment Shader

GLSL Language Definition

 Data Type Description 

int

Integer        

float bool vec2 vec3

Floating-point Boolean ( true or false ).

Vector with two floats.

Vector with three floats.

vec4

Vector with four floats.

mat2 2x2 floating-point matrix.

mat3 3x3 floating-point matrix.

mat4 4x4 floating-point matrix.

Vector

   Vector is like a structure You can use following to access   .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);

Addition data type : Texture

    Sampler   

sampler{1,2,3}D sampler{1,2}DShadow samplerCube sampler{1,2,3}D

 Texture unit to access the content of texture.

sampler*DShadow

 The depth texture for shadow map.

samplerCube

 The cube map.

Addition data type



struct, array

  Similar to C.

No union, enum, class

Qualifiers

 Used to management the input and output of shaders.

  attribute  Communicate changing variables from the application to a vertex shader.

uniform  Communicate changing variables from the application to any shader.

 varying  Communicate interpolated variables from a vertex shader to a fragment shader

Qualifiers

OpenGL Application uniform attribute Vertex Shader varying Fragment Shader

Vertex Shader

Fragment Shader

Vertex Shader Code Example

void main(void) { vec3 v3Normal; float fAngle; float fShininessFactor; v3Normal = gl_NormalMatrix * gl_Normal; v3Normal = normalize(v3Normal); fAngle = max(0.0, dot(v3Normal, vec3(gl_LightSource[0].halfVector))); fShininessFactor = pow(fAngle, gl_FrontMaterial.shininess); gl_FrontColor = gl_LightSource[0].ambient * gl_FrontMaterial.ambient + gl_LightSource[0].diffuse * gl_FrontMaterial.diffuse * fAngle + gl_LightSource[0].specular * gl_FrontMaterial.specular * fShininessFactor; gl_Position = ftransform(); }

Fragment Shader Code Example

void main(void) { gl_FragColor = gl_Color; }

Result

OpenGL Gouraud Shading GLSL Phong Shading

Use GLSL in OpenGL

  You need those head and library files   glew.h

wglew.h

  glew32.lib

glew32s.lib

 glew32.dll

texture   glaux.h

glaux.lib glaux.dll

Texture

#define TEX_NUM 1 //the number of textures you use.

Gluint texObject[TEX_NUM]; //texture object glEnable(GL_TEXTURE_2D); glBindTexture(GL_TEXTURE_2D, texObject[0]); GLint location = glGetUniformLocationARB( MyShader, "colorTexture"); glMultiTexCoord2fv(GL_TEXTURE0_ARB,object->tList[object->faceList[i][j].t].ptr);

LoadTexture

void LoadTexture(int textureIndex,char* filename) { AUX_RGBImageRec* img; img = auxDIBImageLoadA(filename); glBindTexture(GL_TEXTURE_2D, texobject[textureIndex]); gluBuild2DMipmaps(GL_TEXTURE_2D, 4, img->sizeX, img->sizeY,GL_RGB, GL_UNSIGNED_BYTE, img->data); glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE,GL_MODULATE); glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_LINEAR_MIPMAP _LINEAR); glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_LINEAR_MIPMAP _LINEAR); }

Texture

Vertex shader

void main() { gl_TexCoord[0].xy = gl_MultiTexCoord0.xy; gl_Position = ftransform(); }

Fragment shader

uniform sampler2D colorTexture; void main (void) { gl_FragColor = texture2D(colorTexture, gl_TexCoord[0].xy).rgba; }

Texture

    vec3 v3Normal = gl_NormalMatrix * gl_Normal; vec3 vVertex = vec3(gl_ModelViewMatrix * gl_Vertex); lightDir = vec3(gl_LightSource[0].position.xyz - vVertex); eyeDir = -vVertex;   gl_ModelViewMatrix : 4x4 Matrix representing the m-v matrix.

gl_NormalMatrix : 3x3 Matrix representing the inverse transpose m-v matrix.This matrix is used for normal transformation .

uniform sampler2D colorTexture; vec2 i = vec2 ( gl_TexCoord[1].x,gl_TexCoord[1].y ); // 將 texture 座標點存入 i vec4 i_color = texture2D(colorTexture,i); // 將 i 座標點的顏色存入 i_color gl_FrontMaterial.ambient gl_LightSource[0].ambient

gl_FrontMaterial.diffuse gl_LightSource[0].diffuse gl_FrontMaterial.specular gl_LightSource[0].specular // 對應程式中的各種 light 參數

HW2 : Shader Programming

    Write a shader program with Phong Shading. (50%) Write a shader program with Bump Mapping. (50%) Due day : 5/21( 四 ) 5/25 HW3

Gouraud Shading Phong Shading Bump Mapping