Water Exclusion Volumes

These are functionally similar to, but different, from #3455. This takes the idea, and extends it to a full volume which is useful for interiors of underwater structures.

The basic premise is to to have a volume, such as a box or sphere, that when the camera is inside of it excludes water from rendering just in that volume. The idea is that if the volume is not intersecting a water plane, the water plane should continue to render. If the plane intersects with water fog, then only the intersected part of the water fog should not be rendered.

Test Plan

• Rez a cube.
• In the cube's features tab, tick the "volume" tickbox (final location TBD)
• Set the shape to "box"
• Set the volume to "water exclusion"
• Intersect the cube with water
• Note that fog behind the volume renders, but does not render inside the volume
• Note that the water plane renders behind the volume, but not inside of the volume
• Pass if both of the above two conditions are true