Multithreaded Paraboloid Mapping - Practical Rendering and Computation with Direct3D 11 - page 590

// Calculate the world space reflection vector, and then transform it to
// the paraboloid basis.
float3 R = reflect ( E, N );
R = mul( R, (float3x3)ParaboloidBasis );

// Calculate the forward paraboloid map texture coordinates, with z
// determining which paraboloid map to sample (front or back).
float3 front;
front. x = (R.x / (2*(1 + R.z))) + 0.5;
front.y = l-((R.y / (2*(1 + R.z))) + 0.5);
front. z = 0.0f;

// Calculate the backward paraboloid map texture coordinates, with z
// determining which paraboloid map to sample (front or back).
float3 back;
back.x = (R.x / (2*(1 - R.z))') + 0.5;
back.y = l-((R.y / (2*(1 - R.z))) + 0.5);
back.z = 1.0f;

// Sample the appropriate paraboloid map based on which direction
// the reflection vector is pointing,
if ( R.z > 0 )
OUT = ParaboloidTexture.Sample( ParaboloidSampler, front );

else

OUT = ParaboloidTexture.Sample( ParaboloidSampler, back );

OUT *= 0.8f;

return OUT;

}

Listing 1 3.8. The pixel shader for rendering a reflective object into another object's paraboloid map.

Figure 13.11. The result of rendering reflective objects into another reflective object's reflection. Model
courtesy of Radioactive Software, LLC, www.radioactive-software.com . Created by Tomas Drinovsky,
Danny Green.