Fire light emission cut off producing banding artifacts

[jstrob]

Hi,
I have another shot here (my missile launcher) where the light from the missile fire on the wall and objects around (which are matte objects) is very noisy and too long to render. using clamp and subpixel doesn't correct it. I think I will just fake it in a separate pass using an omni light animated to follow the fire.

If anyone find a fix for this please tell me.

[jstrob]

In fact I was using matte objects to create light from fire pass to comp on live footage. But I noticed if I use a black material override instead, I get a lot less noise. Still noisy but I will use the denoiser to see.

[Svetlin.Nikolov]

Good find! I'm afraid that until we make the Fire lights native to V-Ray, there will always be similar situations, and workarounds such as this or reducing the light resolution, the light power on scene options or experimenting with the light subdivisions would be the way to go.

[jstrob]

Good find! I'm afraid that until we make the Fire lights native to V-Ray, there will always be similar situations, and workarounds such as this or reducing the light resolution, the light power on scene options or experimenting with the light subdivisions would be the way to go.

In fact the biggest problem with lighting on objects (from PhoenixFD) when the objects are matte object (from their prop in vray prop) is the render time. It was more than 8 hours a frame and still very noisy. So creating a separate pass with a black vray material on regular objects was way faster to render ( 50 minutes a frame down from more than 8 hours on dual xeon E5-2640 v3).

And so raising light subdiv would not work, reducing light power on scene would not work cause in my scene is was alreayd pretty dark. I am trying lowering light resolution just to see but even at 0.01 (I was at 6 or 7 before), there is still noise.

[jstrob]

Now I had a problem with too much noise/artefact and very slow render in my light pass even with the black shader override. I even had some bucket with noise and some other that were ok.

but I just change the volumetric mode to the volumetric geometry mode for my light pass and now it works lik e a charm and renders super fast.

before (the result of some render region experiment avorted because it was too slow):


and the vol geo mode:
:

[Paul Oblomov]

Can ya try changing to pure gi scattering mode + probabilistic volumetric + and use bf with no second bounce like bf or lc. Maybe that will work.

[jstrob]

In fact in my last post i was thinking I had a working solution but it worked only on this particular scene. I tried in other scene with all the same assets, just a different sim of the same tank shooting form different angle and now it doesn't work anymore! Artefacts and slowness are back and even worse. I doubled check my settings (vray render settings as well as volumetric options in phoenix) to be sure they were the exact same in all of my 3 scenes and they are! So my final and easy solution is to just manually animate an omni light with area shadow and it works in this case perfectly and so faster.

[Svetlin.Nikolov]

Once the V-Ray Adaptive lights are stable and we're done with the current stabilization of Phoenix, we should change the light model to use the Adaptive lights. The current Phoenix lights were doing an acceptable job initially, but as V-Ray has progressed, the Phoenix part of the illumination has become obsolete, and the V-Ray part cannot be properly controlled by Phoenix anymore. I hope Adaptive lights would be the ultimate solution, so for now if it doesn't work out of the box, working around it with an animated light would be a solution as well.

Cheers!