Multithreaded Paraboloid Mapping - Practical Rendering and Computation with Direct3D 11 - page 589

for ( int i = 0; i < 3; i++ )
{

// Create a projection factor, which determines which half space
// will be considered positive and also adds the viewing vector
// which is (0,0,1) and hence can only be added to the z-component.
float projFactor = input[order[i] ] .z_value * direction + 1.0f;
output.position.x = input[order[i]].position.x / projFactor;
output.position.y = input[order[i]].position.y / projFactor;
output.position.z = input[order[i]].position.z;
output.position.w = 1.0f;

// Simply use the geometry shader instance as the render target
// index for this primitive,
output.rtindex = id;

// Propagate the normal and eye vectors,
output.normal = input[order[i]].normal;
output.eye = input[order[i]].eye;

output.z_value = input[order[i]].z_value * direction;

// Write the vertex to the output stream.
OutputStream. Append (output);

}

OutputStream. RestartStrip( );

}

Listing 13.7. The geometry shader for rendering a reflective object into another object's paraboloid map.

The final step this rendering configuration is to look up the paraboloid map of the ob-
ject being rendered. This is done in the pixel shader, which is in fact the same pixel shader
that we used when rendering the reflective object into a standard render target. 6

float4 PSMAIN( PS_INPUT IN ) : SV_Target
{

float4 OUT;

clip( IN.z_value + 0.05f );

// Normalize the input normal and eye vectors
float3 N = normalize( IN.normal );
float3 E = normalize( IN.eye );

6 At this point in the pipeline, the pixel shader isn't concerned with whether we are rendering into another
paraboloid map, or if we are rendering into a standard perspective-projection-based render target. This is one
of the advantages of designing the rendering pipeline in stages, which promotes the reuse of individual shader
programs.