296ac0e9ef
In the original paper, the falloff inside `bcone.theta_e` is assumed to be `pi/2`, which is too large for spot light and resulted in an overestimation near the cone boundary. To address this issue, attenuate the energy of a spot light using the minimal possible angle formed by the light axis and the shading point when traversing the light tree. Ref: #122362 Pull Request: https://projects.blender.org/blender/blender/pulls/122667