Enhancement/Bug: Potential fixes for func_smokevolume

[spiro9-peef]

What would this enhancement be for?

Entity

Describe your enhancement suggestion in more detail

This isn't strictly a bug report since the issue is sorta minor (imo) and may not actually be present, so I'm treating it like an enhancement suggestion.

When using func_smokevolume I noticed that having the particle separation settings be super low (say, 65u) seemed to lock most of the particles into a box area at one end of the room I was working with. This wasn't intended behavior, and I'm not sure if there's a coded-in limit on how many particles the entity can create, so I'm treating that as a possible bug report to be looked into.

Apart from that, I think having added settings for the entity (as regards light) would be nifty to have. Currently, the upper limit of color (Particle Color2 in Hammer) restricts the maximum color the particles can become when lit. Though I think for most use cases this is probably fine, I think it can stand to be improved by having a "direct light" functionality that works with both rt lights and stock lights, in such a way it would allow direct light to "overbrighten" particles in its AOE beyond the upper limit parameter. In different phrasing, it would be nice to have a way to fake volumetrics using this entity without getting random patches of bright particles floating about, which I'm guessing is a consequence of ambient light samplers? I don't know for sure. But consistently, setting the max brightness to 255 255 255 seems to cause random particles to get unusually and distractingly bright, which ruins the effect.

Additionally, this entity's particles seem to have a tendency to Z-fight/incorrectly alpha sort, specifically with stock P2 vine models (but this applies to anything with non-alphatest transparency, from what I've seen). This is extremely distracting and I think it would be worth fixing.