source: GTP/trunk/App/Demos/Illum/Ogre/Media/materials/programs/_oldGameTools_DepthShadow.hlsl @ 1094

///////depth map
struct VS_OUT
{
        float4 hPosition        : POSITION;
        float4 Position : TEXCOORD0;
};

VS_OUT hDepthVS(float4 position : POSITION,     
                uniform float4x4 worldView,
                uniform float4x4 worldViewProj)
{
  
  VS_OUT OUT;
  OUT.hPosition = mul(worldViewProj, position);
  OUT.Position = mul(worldView, position);
  OUT.Position.z *= -1.0;
  return OUT;
}



float4 DepthPS(VS_OUT IN ):COLOR
{
        float dist = length(IN.Position.xyz);
        return float4(dist, dist, dist, 1);     
}

///////////////Shadow

struct VS_OUT_SHADOW
{
        float4 hPosition        : POSITION;
        float4 Position         : TEXCOORD0;
};

VS_OUT_SHADOW depthShadowVS(float4 position : POSITION, 
                uniform float4x4 world,
                uniform float4x4 worldViewProj)
{
  VS_OUT_SHADOW OUT;
  OUT.hPosition = mul(worldViewProj, position);
  OUT.Position = mul(world, position);
  return OUT;
}


float4 depthShadowPS(VS_OUT_SHADOW IN,
                                        uniform float4x4 lightView,
                                        uniform float4x4 lightViewProj,
                                        uniform sampler2D depthShadowMap ):COLOR
{
        float bias = 0.0;
        float4 shadowColor = float4(0.4, 0.4, 0.4, 1.0);

        float4 light = 1;
        
        float4 lightCamPos = mul(lightView, IN.Position);
        float d = length(lightCamPos.xyz);
        
        float4 lightScreenPos = mul(lightViewProj, IN.Position);
        lightScreenPos = lightScreenPos / lightScreenPos.w ;
        float dist = length(lightScreenPos.xy);
        
        if(dist < 1.0 && lightCamPos.z < 0)
        {
                lightScreenPos = ( lightScreenPos + 1.0 ) / 2.0;
                lightScreenPos.y = 1.0 - lightScreenPos.y;
                float4 storedDepth = tex2D(depthShadowMap, lightScreenPos.xy);
                        
                
                if(storedDepth.r + bias < d)
                        light = shadowColor;
                if(storedDepth.r == 0)
                        light = 1;                      
        }
        else
                light = 1;
                
        return light;   
}