source: GTP/branches/IllumWPdeliver2008dec/IlluminationWP/demos/OgreGames/CarGame/Media/materials/programs/GameTools_DepthShadow.hlsl @ 3255

///////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;
        float4 cPosition        : TEXCOORD1;
};

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


float4 depthShadowPS(VS_OUT_SHADOW IN,
                                        uniform float4x4 lightView,
                                        uniform float4x4 lightViewProj,
                                        uniform float4x4 lightView2,
                                        uniform float4x4 lightViewProj2,
                                        uniform sampler2D depthShadowMap : register(s0),
                                        uniform sampler2D depthShadowMap2 : register(s1)):COLOR
{                                       
        float bias = 0.06;
        float4 shadowColor = float4(0.6, 0.6, 0.6, 1.0);

        float4 light1 = 1;
        float4 light2 = 1;
        float weight1 = 1;
        float weight2 = 1;
        
        float4 lightCamPos1 = mul(lightView, IN.Position);
        float d1 = length(lightCamPos1.xyz);    
        float4 lightScreenPos1 = mul(lightViewProj, IN.Position);
        lightScreenPos1 = lightScreenPos1 / lightScreenPos1.w ; 
        lightScreenPos1 = ( lightScreenPos1 + 1.0 ) / 2.0;
        lightScreenPos1.y = 1.0 - lightScreenPos1.y;
        float4 storedDepth1 = tex2D(depthShadowMap, lightScreenPos1.xy);
                if(storedDepth1.r + bias < d1)
                        light1=0;
        
        
        float4 lightCamPos2 = mul(lightView2, IN.Position);
        float d2 = length(lightCamPos2.xyz);
        
                        
        float4 lightScreenPos2 = mul(lightViewProj2, IN.Position);
        lightScreenPos2 = lightScreenPos2 / lightScreenPos2.w ; 

        if(abs(lightScreenPos2.x) < 0.99 && abs(lightScreenPos2.y) < 0.99 )
        {
                lightScreenPos2 = ( lightScreenPos2 + 1.0 ) / 2.0;
                lightScreenPos2.y = 1.0 - lightScreenPos2.y;
                float4 storedDepth2 = tex2D(depthShadowMap2, lightScreenPos2.xy);
                        if(storedDepth2.r + bias < d2)
                                light2=0;       
        }
        else
                weight2 = 0;
                
        weight1 = 1 - weight2;  
                
        return saturate((light1*weight1 + light2*weight2) + shadowColor);       
}