The standard approach for rendering a single lights inscattering is to render the backfaces of a cone around the light, and ray march through the shadowmap, adding inscattering for each unoccluded step. This is the approach I was going to use for volumetric fog before the current method worked out (camera-aligned volume texture with reprojection). Unfortunately this requires code changes because you can’t access the shadowmap in the material editor out of the box. It also doesn’t integrate with other translucency very well - you have to sort per-object so translucent hair that’s halfway through the flashlight will either be in front or behind the flashlight inscattering.
Thanks! So basically this approach is not possible without a custom build of the engine? Out of curiosity, is there any intention to expose shadow maps to the material editor?