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Calculating Far Frustum Corners in Pixel Shader


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#1 TiagoCosta   Crossbones+   -  Reputation: 2189

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Posted 04 May 2012 - 04:09 PM

I'm trying to calculate the far frustum corners position in view space in the pixel shader but it's not working...

I'm following MJP's article:

So I draw a fullscreen quad with the following vertices:

PVertex vertices[] = 
{
     PVertex(-1.0f, -1.0f, 1.0f),
     PVertex(-1.0f, 1.0f, 1.0f),
     PVertex(1.0f, 1.0f, 1.0f),
     PVertex(1.0f, -1.0f, 1.0f)
};

And the vertex shader looks like this:

VS_OUT VS(VS_IN vIn)
{
VS_OUT vOut;

vOut.posH = float4(vIn.posL, 1.0f);

#ifdef DIRECTIONAL_LIGHT
vOut.positionVS = mul(float4(vIn.posL, 1.0f), gInvView);
#else
vOut.positionVS = mul(float4(vIn.posL, 1.0f), gWorld).xyz;
#endif

return vOut;
}

However positionVS gets values like: (-0.736, -0.414, 1.0); which is far from a far frustum corner position in view space...

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#2 jameszhao00   Members   -  Reputation: 271

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Posted 04 May 2012 - 04:38 PM

(-1, -1, 1), ... are in NDC space.

NDC -> VS

float3 ndc = //....
float4 hcs = float4(ndc, 1) * invProj
float3 vs = hcs.xyz / hcs.w

#3 TiagoCosta   Crossbones+   -  Reputation: 2189

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Posted 04 May 2012 - 05:06 PM

Thanks I totally forgot to do the w-divide.




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