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_ModelViewMatrix uniform 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;