In Final Gather, is the hemisphere orientation determined by the surface normal of the triangle at the point?

In Final Gather, is the hemisphere orientation determined by the surface normal of the triangle at the point?

• A. True
• B. False
• C. Depends on light type
• D. It is never used

Answer: (A)

The main idea being tested is that Final Gather uses a hemisphere oriented by the local surface normal to sample incoming light. At each shading point, FG casts rays into the half-sphere that sits in front of the surface, defined by the surface normal, so directions behind the surface aren’t considered. This ensures the indirect lighting estimate reflects how light actually reaches that point from above the surface. The normal used for this orientation is the shading normal, which can be influenced by smoothing or normal maps, so the sampling direction follows how the surface appears to the eye rather than just the raw geometric facet. This behavior is independent of the light type, and FG is indeed used to approximate indirect illumination. So, the correct understanding is that the hemisphere orientation is determined by the surface normal at the point.

The main idea being tested is that Final Gather uses a hemisphere oriented by the local surface normal to sample incoming light. At each shading point, FG casts rays into the half-sphere that sits in front of the surface, defined by the surface normal, so directions behind the surface aren’t considered. This ensures the indirect lighting estimate reflects how light actually reaches that point from above the surface.

The normal used for this orientation is the shading normal, which can be influenced by smoothing or normal maps, so the sampling direction follows how the surface appears to the eye rather than just the raw geometric facet. This behavior is independent of the light type, and FG is indeed used to approximate indirect illumination. So, the correct understanding is that the hemisphere orientation is determined by the surface normal at the point.