Reconstructing Position From Depth Buffer

Reconstructing Position From Depth Buffer

float3 vFrustumCornersWS[8] =
{
	float3(-1.0,  1.0, 0.0),	// near top left
	float3( 1.0,  1.0, 0.0),	// near top right
	float3(-1.0, -1.0, 0.0),	// near bottom left
	float3( 1.0, -1.0, 0.0),	// near bottom right
	float3(-1.0,  1.0, 1.0),	// far top left
	float3( 1.0,  1.0, 1.0),	// far top right
	float3(-1.0, -1.0, 1.0),	// far bottom left
	float3( 1.0, -1.0, 1.0)		// far bottom right
};

for(int i = 0; i < 8; ++i)
{
	float4 vCornerWS = mul(mViewProjInv, float4(vFrustumCornersWS[i].xyz, 1.0));
	vFrustumCornersWS[i].xyz = vCornerWS.xyz / vCornerWS.w;
}

for(int i = 0; i < 4; ++i)
{
	vFrustumCornersWS[i + 4].xyz -= vFrustumCornersWS[i].xyz;
}

// Passes to the pixel shader - there are two ways to do this:
// 1. Pass the corner with the vertex of your quad as part of the input stage.
// 2. If you're quad is created dynamically with SV_VertexID, as in this example, just pick one from a constant array based on the position.
float3 vCamVecLerpT = (OUT.vPosition.x>0) ? vFrustumCornersWS[5].xyz : vFrustumCornersWS[4].xyz;
float3 vCamVecLerpB = (OUT.vPosition.x>0) ? vFrustumCornersWS[7].xyz : vFrustumCornersWS[6].xyz;	


///PIXEL:


float3 vWorldPos = fLinearDepth * IN.vCamVec.xyz + vCameraPos;


From:
http://www.gamedev.net/topic/659279-reconstructing-position-from-depth-buffer/#entry5170000
OUT.vCamVec.xyz = (OUT.vPosition.y<0) ? vCamVecLerpB.xyz : vCamVecLerpT.xyz;