in OpenGL vertex shaders, what is w, and why do I divide by it?

Posted by anon on Stack Overflow See other posts from Stack Overflow or by anon
Published on 2010-03-11T05:29:23Z Indexed on 2010/03/11 5:33 UTC
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opengl

|

vertex-shader

void main(void)
{
  vec4 clipCoord = glModelViewProjectionmatrix * gl_Vertex;
  gl_Position = clipCoord;

  gl_FrontColor = gl_Color;

    vec3 ndc = clipCoord.xyz / clipCoord.w;

So the clipCoord is just doing standard fixed pipeline ransforms. Now, the ndc ... why do I divide by w, and what do I get from this?

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