source: GTP/trunk/App/Demos/Vis/FriendlyCulling/src/shaders/mrt.cg @ 3017

// input
struct vtxin 
{
  float4 position: POSITION;
  float3 normal: NORMAL;
  float4 color: COLOR0;
  float4 texCoord: TEXCOORD0;
};

// vtx output
struct vtxout
{
  float4 position: POSITION; // eye space
  float4 texCoord: TEXCOORD0;    

  float4 color: COLOR0;  
  float4 worldPos: TEXCOORD1; // world position
  float3 normal: TEXCOORD2;
  float4 projPos: TEXCOORD3;
};


// fragment input
struct fragin
{
        float4 color: COLOR0;  
        float4 position: POSITION; // eye space
        float4 texCoord: TEXCOORD0;    

        float4 winPos: WPOS;
        float4 worldPos: TEXCOORD1; // world position
        float3 normal: TEXCOORD2;
        float4 projPos: TEXCOORD3;
};


struct pixel
{
        float4 col: COLOR0;
        float3 norm: COLOR1;
        float3 pos: COLOR2;
};

#pragma position_invariant vtx

vtxout vtx(vtxin IN, 
                   const uniform float4x4 ModelViewProj,
                   uniform float4x4 ModelView)
{
        vtxout OUT;

        OUT.color = IN.color;
        OUT.texCoord = IN.texCoord;

        //OUT.worldPos = mul(glstate.matrix.inverse.projection, OUT.position);
        OUT.worldPos = mul(ModelView, IN.position);
        // transform the vertex position into eye space
        OUT.position = mul(glstate.matrix.mvp, IN.position);

        OUT.normal = IN.normal;
        OUT.projPos = OUT.position;

        return OUT;
}


// bilinear interpolation
inline float3 Interpol(float2 w, float3 bl, float3 br, float3 tl, float3 tr)
{
        float3 x1 = lerp(bl, tl, w.y);
        float3 x2 = lerp(br, tr, w.y); 
        float3 v = lerp(x1, x2, w.x); 

        return v;
}

//#pragma position_invariant fragtex

pixel fragtex(fragin IN, 
                          uniform sampler2D dirtTex,
                          uniform sampler2D tex,
                          uniform float3 eyePos,
                          uniform float3 bl,
                          uniform float3 br,
                          uniform float3 tl,
                          uniform float3 tr
                          )
{
        float4 texColor = tex2D(tex, IN.texCoord.xy);

        // account for alpha blending
        if (texColor.w < 0.5f) discard;

        pixel pix;

        // save color in first render target
        // hack: use combination of emmisive + diffuse (emmisive used as constant ambient term)
        pix.col = (glstate.material.emission + glstate.material.diffuse) * texColor; 
        // save world space normal in rt
        pix.norm = IN.normal;

        // hack: squeeze some information about ambient into the texture
        //pix.col.w = glstate.material.emission.x;

        // compute eye linear depth
        const float4 projPos = IN.projPos / IN.projPos.w;
        
        float2 screenCoord = projPos.xy * 0.5f + 0.5f;
        
        const float3 viewVec = Interpol(screenCoord, bl, br, tl, tr);
        const float invMagView = 1.0f / length(viewVec);
        // note: has to done in this order, otherwise strange precision problems!
        pix.col.w = invMagView * length(eyePos - IN.worldPos.xyz);

        return pix;
}


pixel frag(fragin IN, 
                   uniform float3 eyePos,
                   uniform float3 bl,
                   uniform float3 br,
                   uniform float3 tl,
                   uniform float3 tr)
{
        pixel pix;

        // hack: use comination of emmisive + diffuse (emmisive used as constant ambient term)
        pix.col = glstate.material.diffuse + glstate.material.emission;

        pix.norm = IN.normal;

        // hack: squeeze some information about the ambient term into the target
        //pix.col.w = glstate.material.emission.x;
        
        // compute eye linear depth and scale with lenght to avoid sqr root in pixel shader
        const float4 projPos = IN.projPos / IN.projPos.w;
        
        float2 screenCoord = projPos.xy * 0.5f + 0.5f;
        const float magView = length(Interpol(screenCoord, bl, br, tl, tr));
        pix.col.w = length(eyePos - IN.worldPos.xyz) / magView;

        return pix;
}