source: GTP/trunk/App/Demos/Illum/Ogre/Media/materials/programs/GameTools_HPS_Smoke_L_Depth.hlsl @ 1879

#define method1

struct VS_OUT
{
        float4 hPosition        : POSITION;
        float4 cPosition        : TEXCOORD1;
        float2 texCoord         : TEXCOORD0;
        float r                         : TEXCOORD2;    
        float4 center           : TEXCOORD3;
        float4 Color            : TEXCOORD4;    
        float2 screenCoord      : TEXCOORD5;
};

VS_OUT HPS_Smoke_L_Depth_VS (float4 position : POSITION,        
                float4 texCoord : TEXCOORD0,
                float4 Color: COLOR0,
                uniform float baseRadius,
                uniform float4x4 worldView,
                uniform float4x4 Proj,
                uniform float4x4 worldViewProj)
{
        VS_OUT OUT;
        float2 offset = texCoord.zw * baseRadius;
        OUT.r = abs(offset.x);
        float4 cPosition;   
        cPosition = mul(worldView, position);
        OUT.center = cPosition; 
        cPosition.xy += offset; 
        OUT.cPosition = cPosition;
        OUT.cPosition.z += baseRadius;
        OUT.cPosition.z *= -1;
        
    OUT.hPosition = mul( Proj, cPosition );
    float4 sPosition = OUT.hPosition / OUT.hPosition.w;
    OUT.screenCoord = (sPosition.xy + float2(1, 1)) / 2.0;
    OUT.screenCoord.y = 1.0 - OUT.screenCoord.y;
     
    OUT.texCoord = texCoord.xy;  
    OUT.Color = Color;  
        return OUT;
} 


float4 HPS_Smoke_L_Depth_PS(VS_OUT IN,
                                                uniform float4x4 Proj,
                                                uniform sampler2D Texture  : register(s0),
                                                uniform sampler2D depthTexture : register(s1),
                                                uniform sampler2D illumVolume : register(s2),
                                                uniform float farplane,
                                                uniform float nearplane                                         
                                                        ) : COLOR
{
        float4 Color = 0;
        float4 impostor = tex2D(Texture, IN.texCoord);
        float f = 1.0 - impostor.g;
        float b = impostor.r;
        float alpha = 0;
        
        if(b == 0)
                discard;        

        float sceneDepth = tex2D(depthTexture, IN.screenCoord).r;
        if(sceneDepth == 0)
                sceneDepth = farplane;
           
        float size = 2.0 * IN.r;
        float frontDepth = IN.cPosition.z + size * (f - 0.5);
        float backDepth = IN.cPosition.z +  size * (b - 0.5);
        
        float far = min(sceneDepth, backDepth);
        float near = max(frontDepth, nearplane);
        
        alpha = (far - near) / (backDepth - frontDepth);
        alpha = saturate(alpha) * impostor.a;
        
        
        Color = float4(1, 1, 1, alpha) * IN.Color;
    return Color; 
        
}

struct VS_OUT_ILLUM
{
        float4 hPosition        : POSITION;
        float4 cPosition        : TEXCOORD1;
        float2 texCoord         : TEXCOORD0;
        float r                         : TEXCOORD2;    
        float4 center           : TEXCOORD3;
        float4 Color            : TEXCOORD4;    
        float2 screenCoord      : TEXCOORD5;
        float4 lightCoord       : TEXCOORD6;
};

VS_OUT_ILLUM HPS_Smoke_L_Depth_Illum_VS (float4 position : POSITION,    
                float4 texCoord : TEXCOORD0,
                float4 Color: COLOR0,
                uniform float width,
                uniform float height,
                uniform float baseRadius,
                uniform float4x4 worldView,
                uniform float4x4 worldViewInv,
                uniform float4x4 lightViewProj,
                uniform float4x4 Proj,
                uniform float4x4 worldViewProj)
{
        VS_OUT_ILLUM OUT;
        //texCoord.z = normalize(texCoord.z);
        //texCoord.w = normalize(texCoord.w);
    float2 offset = texCoord.zw * baseRadius;
        OUT.r = abs(offset.x);
        float4 cPosition;   
        cPosition = mul(worldView, position);
        OUT.center = cPosition; 
        cPosition.xy += offset; 
        OUT.cPosition = cPosition;
        OUT.cPosition.z *= -1;
        //OUT.cPosition.z = OUT.cPosition.z - OUT.r;    
        
    OUT.hPosition = mul( Proj, cPosition );
    float4 sPosition = OUT.hPosition / OUT.hPosition.w;
    OUT.screenCoord = (sPosition.xy + float2(1.0, 1.0)) / float2(2.0, 2.0);
    float2 halfpixel = float2(0.5 / width, 0.5 / height);
    OUT.screenCoord += halfpixel;   
    OUT.screenCoord.y = 1.0 - OUT.screenCoord.y;
         
    OUT.texCoord = texCoord.xy;  
    OUT.Color = Color;
    float4 wPosition = mul(worldViewInv, cPosition);
    OUT.lightCoord = mul(lightViewProj, wPosition);
        return OUT;
} 

float ext(float z, sampler2D illumVolume, float2 lightCoord)
{
        float4 extintion = tex2D(illumVolume, lightCoord);
        
        float intensities[5];
        intensities[0] = 1.0;
        intensities[1] = extintion.r;
        intensities[2] = extintion.g;
        intensities[3] = extintion.b;
        intensities[4] = extintion.a;
        
        z = 4.0 * z;
        int start = floor(z);
        return lerp( intensities[start], intensities[start + 1], z - ((float) start));  
}

float4 HPS_Smoke_L_Depth_Illum_PS(VS_OUT_ILLUM IN,
                                                uniform float4x4 Proj,
                                                uniform sampler2D Texture  : register(s0),
                                                uniform sampler2D depthTexture : register(s1),
                                                uniform sampler2D illumVolume : register(s2),
                                                uniform float farplane                                          
                                                        ) : COLOR
{
        float4 Color = 0;
        float4 impostor = tex2D(Texture, IN.texCoord);
        float f = 1.0 - impostor.g;
        float b = impostor.r;
        float alpha = 0;
        
        if(b == 0)
                discard;        

        float sceneDepth = tex2D(depthTexture, IN.screenCoord).r;
        if(sceneDepth == 0)
        {
                alpha = impostor.a;
        }
        else
        {       
                float size = 2.0 * IN.r;
                float frontDepth = IN.cPosition.z + size * (f - 0.5);
                float backDepth = IN.cPosition.z +  size * (b - 0.5);
                
                alpha = (sceneDepth - frontDepth) / (backDepth - frontDepth);
                alpha = saturate(alpha) * impostor.a;
        }
        
        float2 lightCoord;
        lightCoord = (IN.lightCoord.xy + float2(1.0, 1.0)) / 2.0;
        lightCoord.y = 1.0 - lightCoord.y;
        float z = IN.lightCoord.z / IN.lightCoord.w;
        
#ifdef method1
        
                float4 extintion = tex2D(illumVolume, lightCoord);
        
                float intensities[5];
                intensities[0] = 1.0;
                intensities[1] = extintion.r;
                intensities[2] = extintion.g;
                intensities[3] = extintion.b;
                intensities[4] = extintion.a;
                        
                float3 start;
                float3 end;
                float3 temp = 1.0;
                float t;
                
                float4 planes = float4(0.33, 0.5, 0.66, 1);
                if(z < planes.x)
                {
                        start = intensities[0];
                        end = intensities[1];
                        t = z / planes.x;
                        temp = lerp(start, end, t);                             
                }
                if(z > planes.x && z < planes.y)
                {
                        start = intensities[1];
                        end = intensities[2];
                        t = (z - planes.x) / (planes.y - planes.x);
                        temp = lerp(start, end, t);                                     
                }
                if(z > planes.y && z < planes.z)
                {
                        start = intensities[2];
                        end = intensities[3];
                        t = (z - planes.y) / (planes.z - planes.y);
                        temp = lerp(start, end, t);                             
                }
                if(z > planes.z)
                {
                        start = intensities[3];
                        end = intensities[4];
                        t = (z - planes.z) / (planes.a - planes.z);
                        temp = lerp(start, end, t);                                     
                }
                IN.Color.rgb *= temp;

#else
        
        float4 extintion = tex3D(illumVolume, float3(lightCoord, z));
        IN.Color.rgb *= extintion;
        /*
        float intensities[5];
        intensities[0] = 1.0;
        intensities[1] = extintion.r;
        intensities[2] = extintion.g;
        intensities[3] = extintion.b;
        intensities[4] = extintion.a;
        
        z = 4.0 * z;
        int start = floor(z);
        float ext = lerp( intensities[start], intensities[start + 1], z - ((float) start));     
        IN.Color.rgb *= ext;*/

#endif
        
        Color = float4(1, 1, 1, alpha) * IN.Color;
      return Color; 
        
}