To align better with the pixel and reduce the samples needed. The paper was using gamma because the jacobian |d_gamma/d_h| approaches infinity at the boundaries, but it seems that clamping at 0.999 is enough for numerical stability. In practice I did not notice a change in the noise level, but it simplifies the range computation and renders faster due to reduced sample amount. Co-authored-by: Olivier Maury <omaury@meta.com> Ref: !129616 Pull Request: https://projects.blender.org/blender/blender/pulls/134130