source: GTP/trunk/App/Demos/Illum/Ogre/Media/materials/programs/GameTools_Smoke_IllumVolume.hlsl @ 1424

struct VS_OUT
{
        float4 hPosition        : POSITION;
        float4 texCoord         : TEXCOORD0;
        float4 color            : COLOR0;
};

VS_OUT SmokeIllumVolumeVS(float4 position : POSITION,   
                float4 texCoord : TEXCOORD0,
                float4 color    : COLOR0,
                uniform float baseRadius,
                uniform float4x4 worldView,
                uniform float4x4 Proj,
                uniform float4x4 worldViewProj)
{
        VS_OUT OUT;

   texCoord.y = 1.0 - texCoord.y;
   float2 offset = texCoord.zw * baseRadius;
   float4 cPosition = mul(worldView, position);
   cPosition.xy += offset;
   
   OUT.hPosition = mul( Proj, cPosition );
   OUT.texCoord = texCoord;
   OUT.color = 1;
   
   float z = OUT.hPosition.z / OUT.hPosition.w;
        
   float4 planes = float4(0.33, 0.5, 0.66, 1);
   if(z > planes.x)
        {
                OUT.color.r = 0;
        }
        if(z > planes.y)
        {
                OUT.color.g = 0;
        }
        if(z > planes.z)
        {
                OUT.color.b = 0;
        }

   
   return OUT;
}


float4 SmokeIllumVolumePS(VS_OUT IN ,
                uniform sampler2D colorTexture : register(s0)):COLOR
{

        return tex2D( colorTexture, IN.texCoord.xy).a * 0.1 * IN.color;
}