For example:
var VertexShaderText = [
'attribute vec2 vertPosition;',
'void main()',
'{',
' gl_Position = vec4(vertPosition, 0.0, 1.0);',
'}'
].join('\n');
Is there a list online somewhere of all the WebGL shader variables you can code with other than gl_Position?
You can find it in both the spec and the WebGL reference card
The reference card lists all of these
Built-In Inputs, Outputs, and Constants [7]
Shader programs use Special Variables to communicate with fixed-function parts of the pipeline. Output Special Variables may be read back after writing. Input Special Variables are read-only. All Special Variables have global scope.
Vertex Shader Special Variables [7.1]
Outputs: Variable Description Units or coordinate system -------------------------------------------------------------------------------------- highp vec4 gl_Position; transformed vertex position clip coordinates mediump float gl_PointSize; transformed point size pixels (point rasterization only)Fragment Shader Special Variables [7.2]
Fragment shaders may write to gl_FragColor or to one or more elements of gl_FragData[], but not both. The size of the gl_FragData array is given by the built-in constant gl_MaxDrawBuffers.
Inputs: Variable Description Units or coordinate system ----------------------------------------------------------------------------------------------- mediump vec4 gl_FragCoord; fragment position within window coordinates frame buffer bool gl_FrontFacing; fragment belongs to a Boolean front-facing primitive mediump vec2 gl_PointCoord; fragment position within a 0.0 to 1.0 point (point rasterization for each only) component Outputs: Variable Description Units or coordinate system ----------------------------------------------------------------------------------------------- mediump vec4 gl_FragColor; fragment color RGBA color mediump vec4 gl_FragData[n] fragment color for RGBA color color attachment nBuilt-In Constants With Minimum Values [7.4]
Built-in Constant Minimum value ---------------------------------------------------------------- const mediump int gl_MaxVertexAttribs 8 const mediump int gl_MaxVertexUniformVectors 128 const mediump int gl_MaxVaryingVectors 8 const mediump int gl_MaxVertexTextureImageUnits 0 const mediump int gl_MaxCombinedTextureImageUnits 8 const mediump int gl_MaxTextureImageUnits 8 const mediump int gl_MaxFragmentUniformVectors 16 const mediump int gl_MaxDrawBuffers 1Built-In Uniform State [7.5]
Specifies depth range in window coordinates. If an implementation does not support highp precision in the fragment language, and state is listed as highp, then that state will only be available as mediump in the fragment language.
struct gl_DepthRangeParameters { highp float near; // n highp float far; // f highp float diff; // f - n }; uniform gl_DepthRangeParameters gl_DepthRange;