GLSL语言摘要(一)

一、流水线

二、顶点处理器

     1. 顶点属性

       // Vertex Attributes
      attribute vec4 gl_Color;
      attribute vec4 gl_SecondaryColor;
      attribute vec3 gl_Normal;
      attribute vec4 gl_Vertex;
      attribute vec4 gl_MultiTexCoord0;
      attribute vec4 gl_MultiTexCoord1;
      attribute vec4 gl_MultiTexCoord2;
      // . . . up to gl_MultiTexCoordN-1 where N = gl_MaxTextureCoords
      attribute float gl_FogCoord;

      2. 特殊的输出变量

      vec4  gl_Position;      // must be written to
      float   gl_PointSize;    // may be written to
      vec4  gl_ClipVertex;  // may be written to

      3. 内置易变变量

   varying vec4  gl_FrontColor;   varying vec4  gl_BackColor;   varying vec4  gl_FrontSecondaryColor;   varying vec4  gl_BackSecondaryColor;   varying vec4  gl_TexCoord[]; // at most will be gl_MaxTextureCoords   varying float gl_FogFragCoord;

三、片元处理器

      1. 内置易变变量

   varying vec4  gl_Color;   varying vec4  gl_SecondaryColor;   varying vec4  gl_TexCoord[]; // at most will be gl_MaxTextureCoords   varying float gl_FogFragCoord;

      2.特殊输入变量

      vec4 gl_FragCoord;
      bool gl_FrontFacing;

      3. 特殊输出变量

   vec4  gl_FragColor;   vec4  gl_FragData[gl_MaxDrawbuffers];   float gl_FragDepth;

四、内置一致性变量

//// Matrix state//uniform mat4  gl_ModelViewMatrix;uniform mat4  gl_ProjectionMatrix;uniform mat4  gl_ModelViewProjectionMatrix;uniform mat4  gl_TextureMatrix[gl_MaxTextureCoords];//// Derived matrix state that provides inverse and transposed versions// of the matrices above. Poorly conditioned matrices may result// in unpredictable values in their inverse forms.//uniform mat3  gl_NormalMatrix; // transpose of the inverse of the upper                               // leftmost 3x3 of gl_ModelViewMatrixuniform mat4  gl_ModelViewMatrixInverse;uniform mat4  gl_ProjectionMatrixInverse;uniform mat4  gl_ModelViewProjectionMatrixInverse;uniform mat4  gl_TextureMatrixInverse[gl_MaxTextureCoords];uniform mat4  gl_ModelViewMatrixTranspose;uniform mat4  gl_ProjectionMatrixTranspose;uniform mat4  gl_ModelViewProjectionMatrixTranspose;uniform mat4  gl_TextureMatrixTranspose[gl_MaxTextureCoords]uniform mat4  gl_ModelViewMatrixInverseTranspose;uniform mat4  gl_ProjectionMatrixInverseTranspose;uniform mat4  gl_ModelViewProjectionMatrixInverseTranspose;uniform mat4  gl_TextureMatrixInverseTranspose[gl_MaxTextureCoords]//// Normal scaling//uniform float gl_NormalScale;//// Depth range in window coordinates//struct gl_DepthRangeParameters{    float near;        // n    float far;         // f    float diff;        // f - n};uniform gl_DepthRangeParameters gl_DepthRange;//// Clip planes//uniform vec4  gl_ClipPlane[gl_MaxClipPlanes];//// Point Size//struct gl_PointParameters{    float size;    float sizeMin;    float sizeMax;    float fadeThresholdSize;    float distanceConstantAttenuation;    float distanceLinearAttenuation;    float distanceQuadraticAttenuation;};uniform gl_PointParameters gl_Point;//// Material State//struct gl_MaterialParameters{    vec4 emission;     // Ecm    vec4 ambient;      // Acm    vec4 diffuse;      // Dcm    vec4 specular;     // Scm    float shininess;   // Srm};uniform gl_MaterialParameters  gl_FrontMaterial;uniform gl_MaterialParameters  gl_BackMaterial;//// Light State//struct gl_LightSourceParameters{    vec4  ambient;              // Acli    vec4  diffuse;              // Dcli    vec4  specular;             // Scli    vec4  position;             // Ppli    vec4  halfVector;           // Derived: Hi    vec3  spotDirection;        // Sdli    float spotExponent;         // Srli    float spotCutoff;           // Crli                                // (range: [0.0,90.0], 180.0)    float spotCosCutoff;        // Derived: cos(Crli)                                // (range: [1.0,0.0],-1.0)    float constantAttenuation;  // K0    float linearAttenuation;    // K1    float quadraticAttenuation; // K2};uniform gl_LightSourceParameters   gl_LightSource[gl_MaxLights];struct gl_LightModelParameters{    vec4 ambient;        // Acs};uniform gl_LightModelParameters gl_LightModel;//// Derived state from products of light and material.//struct gl_LightModelProducts{    vec4 sceneColor;      // Derived. Ecm + Acm * Acs};uniform gl_LightModelProducts gl_FrontLightModelProduct;uniform gl_LightModelProducts gl_BackLightModelProduct;struct gl_LightProducts{    vec4 ambient;         // Acm * Acli    vec4 diffuse;         // Dcm * Dcli    vec4 specular;        // Scm * Scli};uniform gl_LightProducts gl_FrontLightProduct[gl_MaxLights];uniform gl_LightProducts gl_BackLightProduct[gl_MaxLights];//// Texture Environment and Generation//uniform vec4  gl_TextureEnvColor[gl_MaxTextureUnits];uniform vec4  gl_EyePlaneS[gl_MaxTextureCoords];uniform vec4  gl_EyePlaneT[gl_MaxTextureCoords];uniform vec4  gl_EyePlaneR[gl_MaxTextureCoords];uniform vec4  gl_EyePlaneQ[gl_MaxTextureCoords];uniform vec4  gl_ObjectPlaneS[gl_MaxTextureCoords];uniform vec4  gl_ObjectPlaneT[gl_MaxTextureCoords];uniform vec4  gl_ObjectPlaneR[gl_MaxTextureCoords];uniform vec4  gl_ObjectPlaneQ[gl_MaxTextureCoords];//// Fog//struct gl_FogParameters{    vec4 color;    float density;    float start;    float end;    float scale;   // 1.0 / (gl_Fog.end - gl_Fog.start)};uniform gl_FogParameters gl_Fog;

五、内置常量

//// Implementation dependent constants.  The values below// are the minimum values allowed for these constants.//const int  gl_MaxLights = 8;const int  gl_MaxClipPlanes = 6;const int  gl_MaxTextureUnits = 2;const int  gl_MaxTextureCoords = 2;const int  gl_MaxVertexAttribs = 16;const int  gl_MaxVertexUniformComponents = 512;const int  gl_MaxVaryingFloats = 32;const int  gl_MaxVertexTextureImageUnits = 0;const int  gl_MaxTextureImageUnits = 2;const int  gl_MaxFragmentUniformComponents = 64;const int  gl_MaxCombinedTextureImageUnits = 2;const int  gl_MaxDrawBuffers = 1;