Volumes with Huge Size = slow

[7enith]

Hi Vladimir,

currently I face a problem where I want to render objects inside a fog using the Volume Shader or the Volume Grid. I´m currently using Vray 3.6.

The Box to which the Volume Material is applied is above 1km in size. It renders fast as long as if I don´t change anything besides the density. But if I even touch the FadeOut or even try to modulate the density with a texture Vray gets extremely slow. The same happens with the Volume Grid with some VDB Clouds, it looks really nice but it gets really really slow when the size gets big. I played around with the step size parameters, but it doesn´t seem to do much. I really would love to use this, since I need Volumes for the project I´m on!

Thanks
Christian

[7enith]

Hi,

again I tried to wrap my forest into a box with a (volume material) fog that is fading out into the up direction via a gradient. And again its just not working out! Its just incredible slow. Is this a known bug? I just cant get Volumes to work, be it the Volume Scatter or the Volume Grid. The only way is not to use a texture on the volumes at all. I tried increasing the Step Size of the raymarching, I turned off Adaptive Lights, it just doesnt work!

I tried to render the Forest in Houdini´s with Mantra and made textured fog and it goes pretty well. Vray usually is much much faster than mantra, but with volumetrics it seems rather useless (at least in my scene). This is super frustrating for Environment Work, since atmosphere is so important for this kind of images! Sorry for this rant!

best
c

[boyan]

Howdy,

Thank you for the feedback, Why did you use Environment fog. You still can use it with geometry. And best of it with specific light/ or group of light. Is there a chance to prove us the scene file?

Cheers,

[7enith]

Howdy,

Thank you for the feedback, Why did you use Environment fog. You still can use it with geometry. And best of it with specific light/ or group of light. Is there a chance to prove us the scene file?

Cheers,

Hello Boyan,

I did use it with Geometry. A box wrapped around the elements I want in Fog and it renders fast as long as I dont use a texture on a fog. With texture its extremely slow
best
Christian

[vladimir.nedev]

You can modify the options under the Raymarching roll-out to help with the render speed.
You can
- check Simplify textures for GI
- increase the step size
- decrease the max steps
- decrease the texture samples
- increase the cutoff threshold

All of these will lead to faster render times but might reduce the quality of the result.

Greetings,
Vladimir Nedev

[7enith]

Thanks Vladimir,

I already did some of these steps but not all. In my case it didn’t help, but I’ll try again and report if it’s working

best
christiab