Cycles runs a check to see if the camera is possibly inside a
volumetric object by seeing if the bounding box of the camera
and volumetric object intersect.
If the calculation is wrong (Cycles says the camera is outside the
volume when it's inside it), then the volume will not render properly.
This commit resolves most of these issues by making the camera
bounding box larger than before, taking into consideration
features like:
1. The impact DOF could have on the camera ray start position and how
that should impact the bounding box size.
2. Taking into consideration near clipping, which was missed from the
orthographic camera due to a oversight in a previous commit
(08cc73a9bb).
Pull Request: https://projects.blender.org/blender/blender/pulls/123341
56bb8b2b3c