GPU Pro 5

174 II Lighting and Shading

4.5.3 Ray-Tracing Pass

The implementation in Listing 4.5 is the Hi-Z ray-tracing code in Microsoft HLSL.

The code snippet is heavily commented and should be easy to follow once the

algorithm presented in Section 4.4.3 is clear.

float3 hiZTrace( float3 p , float3 v )

{

const float rootLevel = mipCount − 1.0f ; // Convert to 0

// based indexing

float level = HIZ_START_LEVEL ; // HIZ START LEVEL was

// set to 2 in the demo

float iterations =0.0f ;

// Get the cell cross direction and a small offset to enter

// the next cell when doing cell crossing.

float2 crossStep , crossOffset ;

crossStep . x =( v . x >=0 ) ? 1.f : −1.f ;

crossStep ...