This allows adding a "fake" sun beam effect, simulating crepuscular rays from light being scattered in a medium like the atmosphere or deep water. Such effects can be created also by renderers using
volumetric lighting, but the compositor feature is a lot cheaper and is independent from 3D rendering. This makes it ideally suited for motion graphics.
The implementation uses am optimized accumulation method for gathering color values along a line segment. The inner buffer loop uses fixed offset increments to avoid unnecessary multiplications and
avoids variables by using compile-time specialization (see inline comments for further details).
More optimization could be achieved by sparser sampling (quality steps) and by utilizing SSE instructions. Currently no antialiasing is done. A number of usability features could be added as well, such
as angle-based blurring (randomizing ray angles) and different blend modes.