Increase sampling resolution of volumetric grid

[oriolopocholo]

The floor is basically a flat light with a mask with a lot of white dots on it and heavy directionality, and the top is a relatively thin volumetric grid. I'd like to see defined lines coming out but they're really spotty and some don't appear at all. Any tips on what to tweak? Thanks

[Joelaff]

You say the top is a volumetric grid. What do you mean by that? You are using VRayEnvironmentFog? Or is it something else? If so you need a smaller Step Size or Texture Samples.

I would be considering VRayEnvironmentFog or traditional volumetric spotlight (far away to get almost parallel rays).

You could also build an array of transparent cylinders and texture map them from above with the same texture used to make the floor. This would be fake volumetrics made with thin transparent vertical cylinders. This could even be modulated with a world space noise texture to make them feel subtly smoky if you wanted. (As if they were light beams through a fog machine, which almost never gets PERFECTLY smooth. There is usually some fractal detail in there because on a practical production the AD never wants to waste time waiting for the smoke machine to even out.)

https://docs.chaosgroup.com/display/...rsWithTextures
https://knowledge.autodesk.com/suppo...D9D62-htm.html

[oriolopocholo]

Hey Joelaff,

Thanks for the reply. The top is a volumetric grid with a 3D map of a cloud loaded on it as smoke. I didn't use the environment fog because i liked the textures at the end of the cloud. The reason why i used the texture and the light is because i sometimes render using video maps, and each light functions independently and they would take much too long to program to respond to the data i have coming in.

PD I don't know what I've done wrong but now when i press render it prepares light cache and then it gets indefinitely stuck on pass 0 (hours) and when i press stop it takes about 5 minutes to do so. Has it happened to you before? Thanks!

https://docs.chaosgroup.com/display/...VRayVolumeGrid


PPD: I fixed the rendering issue by restarting. I have also reduced step size and increased directionality, and look at what happens:

https://imgur.com/a/ZlX2l6j

Thanks for the help.

[oriolopocholo]

Okay, seems like I kinda solved it. I had to turn off the Volume Light Cache in Volumetric Options in the Volumetric Fog's Modify menu. It takes much longer because it seems to be bruteforcing it now but at least it works.

[Joelaff]

Oh, I see.

I have found a fast rendering approximation of this type of thing can be done by stimulating particles with your fog in Phoenix (or wherever), and then using the Fog mode of the ParticleShader. You need a lot of particles, but it looks pretty nice and renders pretty quickly.