Is there a way to properly render shadowing of particles on each other with large amounts of particles.
I’m actually facing several issues that come and go depending on the settings used and where they are used. Some of the issues result from the type of lighting used, others just don’t work right under certain settings.
I know this is all a game of smoke and mirrors and that there will be limitations, but I’ll pose the big question. Am I missing something? Or, am I fighting the the limits of this system? Or heck, is this broken?
here is the video followed by a quick break down of what I am experiencing:
0:00 - The original cloud from the content demo was used as baseline. I used this in my other map as well to determine how settings are actually affecting things since i know what its supposed to look like. the only noticeable artifact I get with this system is from moving along the relative path of the directional light. Very forgivable IMO.
0:23 - Cloud with velocity to mimic smoke is basically the same thing. just shows how movement affects it for a baseline comparison. I circle around it to show that it works fine from any angle. keep that in mind…
0:45 - the above modified to be a GPU emitter instead. behaves roughly the same way so I don’t spend much time on it. proof of concept. it works fine.
1:00 - GPU cloud with tiny particles. I shrunk the particles quite a bit and made it so this system has roughly 1k particles at all times. whats noticable about this system is that all particles in the spotlight beam react the same way to the light. so even the ones in the back light up so to speak. This is one of the issues I’ve kept noticing and thinking was an issue with normals or something. turns out as soon as I flip over to directional lighting that goes away, but then we have other issues. As I turn my camera view roughly 90 degrees back and forth, the color of the particles gets altered. I figure it’s expected behavior considering these are billboards, but there seems to be a fairly big difference between observing it with spotlights vs directional. I guess its just the way the textures blend with directional light.
1:53 - 10k GPU Particles with spherical normals (and a sharp circle texture). Everything looks nice at first, you can see that all of the particles within the cone of light are illuminating properly. the only downside is that with spotlights they each sample the light and dont occlude each other from it. I switch over to directional light and this is where things get really… interesting? So while I understand that there may be some loss of precision as the systems get bigger and more complex, what I’m seeing is just not right. First, there are shadows in the front where there should be none. This is a short video, but I’ve looked at individual particles before and the shadow positions are wrong. second, you can see here that the shadows are moving up on the particles themselves. The colors are wrong. it’s no longer spherical, but flat! It also seems like there is some issue with depth, though that is not quite apparent in this one… Also just to add an extra note. I had velocity on these at uniform 80 - 100… i just made it 100 even while writing this and the shadow moving issue is still there.
2:45 - 100k GPU particles. the same as above, just more of it. (The only tiny difference is that I accidentally left the translucent multiple sscattering extinction color at white instead of default, but that only changes the color of the shadow, not the issue) Because everything is tightly packed, you can see the errors clearly standing out now. mostly the same as above. stuff pops in and out at places. One thing I do want to point out while looking at the back of the system (time index 3:28 is a good spot) I notice that the shadows on the shadowed particles … are on top?
3:35 - Mesh particles. I wasnt going to do this one originally, but I remembered seeing something very odd… you can see it right at the start. with this new minimalist setup, the shadows appear to be rendered right over the particle system. I think there might also be a depth problem, but whatever is happening is messing with my brain and I cant stare at this for long enough to figure it out. its apparent when I rotate the camera. I just triple checked this and PSORTMODE is “Distance to view”. My instinct tells me the shadow issue shown here is related to the other particles since they seem to show the same behavior for directional and spot lighting changes.
4:17 - I finally found the cause of one of my headaches!! read the note… watch the issue.
end.
PS. I posted this on Trying to get particle shadows to apply to other particles. - Rendering - Unreal Engine Forums and have not been able to get a real answer.
