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 Floating-point bool Boolean (true or false). vec2 Vector with two floats. vec3 Vector with three floats. vec4 Vector with four floats. mat22x2 floating-point matrix. mat33x3 floating-point matrix. mat44x4 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 = 0.5or 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

Vertex Shader

Fragment Shader

OpenGL Application

uniform

attribute

varying

Vertex Shader

Fragment Shader

Vertex Shader Code Examplevoid 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 objectglEnable(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);

LoadTexturevoid 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_MI

PMAP_LINEAR);

}

TextureVertex shadervoid main(){

gl_TexCoord[0].xy = gl_MultiTexCoord0.xy;gl_Position = ftransform();

}Fragment shaderuniform 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 ivec4 i_color = texture2D(colorTexture,i);// 將 i 座標點的顏色存入 i_colorgl_FrontMaterial.ambient gl_LightSource[0].ambientgl_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

Phong ShadingGouraud Shading

Bump Mapping