This patch redesigns the Sun Beams node. The old implementation produces
unexpected results with an arbitrary alpha channel, due to the use of a
step count normalization instead of a weighted normalization. The
quality is also questionable due to the use of nearest neighbour
interpolation as well as a low resolution integration.
This patches redesign the node to be a simple line integration towards
the source, limited by the maximum ray length. The sampling resolution
covers the entire path of the integration and the image is sampled using
bilinear filtering, producing smoother results. No alpha is introduced.
Pull Request: https://projects.blender.org/blender/blender/pulls/116787
9e358fcd44