Support opaque (and black) particles

[HifiExperiments]

Closes #833

Particles can render opaque if their texture has no alpha or is detected as "alpha mask" (e.g. https://pngimg.com/d/grass_PNG4922.png). If any of their alpha properties (start, middle, finish) are < 1, or their alpha spread is > 0, or they have alpha pulsing, they'll go back to transparent (+ additive blending). At a later date, we could support overriding the automatic detection via material entities.

Funding

This project is funded through NGI0 Entrust, a fund established by NLnet with financial support from the European Commission's Next Generation Internet program. Learn more at the NLnet project page.

[SilverfishVR]

It's beautiful

And everything seems to work as advertised 👍

[vegaslon]

interesting side effect is they cast shadows, can even be turned off correctly

[vegaslon]

if all alpha properties are set to 1 are they suppose to render as black and have no color? this is on high setting for the graphics on a amd

Tested it on a Nvidia card and they are showing up with color so must be amd.

[HifiExperiments]

@vegaslon ah AMD has given us this problem in the past. I don't have an AMD card to test but I've pushed a potential fix.

[vegaslon]

that worked to restore color to the particles, side effect is the particles no longer throw shadows (For how ever much that is worth).

[HifiExperiments]

that would explain this comment that I copied from polyvox: // FIXME: custom pipelines like this don't handle shadows or renderLayers correctly lol

renderLayers actually do seem to work...but it seems neither polyvox nor particles can cast shadows. these are the only two things that use a specific codepath (custom pipelines). I would vote to merge this as is and then I can fix that issue separately so as to not clutter up this PR.

I already have shadows working with GPU particles^TM though 😄

[vegaslon]

Ok this is something, When I run the build from github actions the particle cast shadows. So ya as far as particles go this pr seems to definitely do the job.

[JulianGro]

What build did you run before? You built from source yourself?

But yeah, maybe the shader cache was just being problematic. I have seen that before on Nvidia at the very least.

[gydence]

oh weird! I built locally and couldn’t get particles or polyvox to cast shadows, which isn’t wholly surprising to me because the way we pick shadow pipelines has never handled this “custom pipeline” path

[vegaslon]

What build did you run before? You built from source yourself?

But yeah, maybe the shader cache was just being problematic. I have seen that before on Nvidia at the very least.

ya I did a self build at first since the github actions had the linux builds stuck in line, so it was not willing to release the download links for the windows one.

[HifiExperiments]

just to be sure, I went ahead and fixed custom pipeline shadows and render layers. this only affects particles and polyvox

to test, opaque particles and polyvox should be able to cast shadows and render correctly in all renderLayers. transparent particles should work like they used to

[vegaslon]

Everything continues to appear in order, Particles and Polyvox apear to both cast shadows now, Opaque textures appear to work and transparent particles continue to function.