Metalights: Improved interleaved shading

We present metalights, a novel Virtual Point Light (VPL) encapsulating structure which enhances classic interleaved shading by improving VPL sampling, based on few initial screen space samples to estimate VPL contribution to current view. Our method leads to important noise variance reduction in the final picture by only adding a small fraction of computation. The implementation is straight-forward and well adapted to both CPU and GPU-based engines. We also present different image-space assignment schemes for the VPL subsets to break the regularity of the noise pattern or to adapt it to simple antialiasing.