Point Sprite automatic texture coords

I'm rendering points (not triangles or quads) and would like to use texture coordinates automatically generated by the hardware after the vertex shader. In OpenGL/GLSL one would simply use the build-in fragment shader input gl_PointCoord. What is the Unity/Cg equivalent of that?

(Note: There is already a discussion in the Scripting forum about this topic, but I think it is more likely to get an answer in the Shaders forum )

Point rendering seems to be badly documented, so for anyone interested:
Set your Mesh to MeshTopology.Points mode using the SetIndices method. Then use a shader like this which writes the point size:

Code (csharp):

1. Shader "Custom/Starfield" {
2.     Properties {
3.     }
4.     SubShader {
5.         Tags { "RenderType"="Opaque" }
6.         LOD 200
7.         Pass {
8.             CGPROGRAM
9.                 #pragma exclude_renderers flash
10.                 #pragma vertex vert
11.                 #pragma fragment frag
12.                
13.                 struct appdata {
14.                     float4 pos : POSITION;
15.                 };
16.                
17.                 struct v2f {
18.                     float4 pos : SV_POSITION;
19.                     float size : PSIZE;
20.                 };
21.    
22.                 v2f vert(appdata v)
23.                 {
24.                     v2f o;
25.                     o.pos = mul(UNITY_MATRIX_MVP, v.pos);
26.                     o.size = 10.0;
27.                     return o;
28.                 }
29.    
30.                 half4 frag(v2f i) : COLOR
31.                 {
32.                     return half4(1,0,0,1);
33.                 }
34.             ENDCG
35.         }
36.     }
37. }

 

I've been looking into this outside of Unity. In OpenGL and Cg, I'm doing this:

Code (csharp):

1.  
2.             glEnable(GL_POINT_SPRITE_ARB);
3.             glEnable(GL_PROGRAM_POINT_SIZE_EXT);
4.             CgGL.SetStateMatrixParameter(mParticleModelViewProj, cgGLModelviewProjectionMatrix, cgGLMatrixIdentity);
5.             mParticleShader.Activate();
6.             cgGLSetTextureParameter(mParticleTexture, TextureId);
7.             cgGLEnableTextureParameter(mParticleTexture);
8.             glTexEnvi(GL_POINT_SPRITE, GL_COORD_REPLACE, GL_TRUE);
9.             glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_REPLACE);
10.             mParticleFragShader.Activate();
11.             mParticles.Render(true);
12.  

(I have shader classes etc that handle some things but the gl and cggl calls are what's important here)

vertex shader

Code (csharp):

1. struct output{
2.     float4 position : POSITION;
3.     float4 color : COLOR;
4.     float  size      : PSIZE;
5. };
6. struct input {
7.     float4 position: POSITION;
8.     float4 color : COLOR;
9. };
10.  
11.  
12. output main(input IN, uniform float4x4 ModelViewProj)
13. {
14.    
15.     output OUT;
16.  
17.     OUT.position = mul(ModelViewProj, IN.position);
18.     OUT.size = 500.0f / OUT.position.w;
19.     OUT.color = IN.color;
20.  
21.     return OUT;
22. }

fragment shader

Code (csharp):

1. struct output
2. {
3.     float4 color : COLOR;
4. };
5.  
6. struct input
7. {
8.     float4 color : COLOR;
9.     float2 texCoord : TEXCOORD0;
10. };
11.  
12. output main(input IN, uniform sampler2D tex)
13. {
14.  
15.   output OUT;
16.  
17.   OUT.color = IN.color * tex2D(tex, IN.texCoord.xy);
18.  
19.   return OUT;
20.  
21. }

Hope that helps.

 

Thanks for your effort, but as I would like to do this inside Unity it's not helping :|