Hi,

I'm hoping someone can help me with a problem I'm struggling with.

I have my one little engine going with deferred rendering and shadows etc. Now I'm trying to do a forward rendering pass for transparent models.

I've got as far as getting the models to render (and be transparent) but I don't seem able to work out how to use my depth map in the forward pass. I'm possibly getting lost in the various coordinate spaces.

Here's a screen shot of the problem (the barrel shouldn't be visible since its behind the wall)

The shader is pretty simple for rendering the barrel:

VertexShaderOutput VertexShaderFunction(VertexShaderInput input)

{

VertexShaderOutput output;

float4 worldPosition = mul(float4(input.Position.xyz,1), World);

float4 viewPosition = mul(worldPosition, View);

output.Position = mul(viewPosition, Projection);

output.Depth.x = output.Position.z;

output.Depth.y = output.Position.w;

output.TexCoord = input.TexCoord;

?

return output;

}

struct PixelShaderOutput

{

half4 Color : COLOR0;

};

PixelShaderOutput PixelShaderFunction(VertexShaderOutput input)

{

//sample depth from depth map

float depthFromMap = tex2D(DepthMapSampler, input.TexCoord).r;

float depthOfPixel = input.Depth.x/input.Depth.y;

if (depthFromMap < depthOfPixel)

discard;

PixelShaderOutput output;

output.Color = tex2D(diffuseSampler, input.TexCoord);

output.Color.a = 0.1f;

return output;

}

And the shader for creating the depth map is:

VertexShaderOutput VertexShaderFunction(VertexShaderInput input)

{

VertexShaderOutput output;

float4 worldPosition = mul(float4(input.Position.xyz,1), World);

float4 viewPosition = mul(worldPosition, View);

output.Depth.x = output.Position.z;

output.Depth.y = output.Position.w;

return output;

}

PixelShaderOutput PixelShaderFunction(VertexShaderOutput input)

{

PixelShaderOutput output;

output.Depth = input.Depth.x / input.Depth.y;

return output;

}

Which seems essentially the same. So what am I doing wrong, any ideas please?

    ...
    float2 depthTex = input.Position.xy / input.Position.w;	
    depthTex.y = -depthTex.y;
    depthTex.xy = depthTex.xy / 2  + 0.5;
    float depthFromMap = tex2D(DepthMapSampler, depthTex).r;
    ...

Thanks for the great help guys, that works perfectly. I still get confused by clip space, texture space and all the other coordinate spaces.

I'll remember the code tags next time I have a question too