It was not the same bug/issue. It’s been there from the beginning. In the GPU volumes test build, I had much better lighting, albeit with glitched out 8x8 pixel artifacts. It can be worked around a number of ways though:
- Cranking all the lights up to insane levels and having to reduce brightness on all other materials.
- Cranking the volume bounces up to insane levels, which unacceptably slows down the render.
- Some interesting blending with hacky negative absorption.
For static scenes or very distant elements in a scene, the fastest solution is to use #1 rendered out to an alpha texture placed on a quad. Fake and static, but fast and simple.
It would seem the nature of cycles volumes is that color and density are basically the same thing. Color just being a way adjust the density independently for R, G, and B. Thus the need to come up with node group solutions with varying blending techniques of scatter and absorption to get the look your after.
On a related note: For static renders I still find moblur abuse to be the fastest and easiest to tweak for certain fog/haze effects. Unless the scene has particle instances. Particle instances of static particle systems apparently are not static when motion blur is enabled with long exposure times. It creates a fuster cluck of motion blur as though the particles all had seizures.