Pyro renders taking way too long

[awkwardpoly]

Hey guys, Im rendering a pyro sim around 1-3 mil voxels, im using an environment light and a volume light emitting from the pyroshader. Rendering using PBR with pixel samples 3x3, volume limit 1, noise level, 0.1, volume quality 0.1, volume shadow quality 0.5 and stochastic 8 im not even using motion blur, but one frame is almost taking 1.5 hours. Any ideas how to increase the performance, am i doing some nonos that i missed? the smoke is fairly transparent and the light from the fire is strong.

[Andrea]

This quality values are already low, seems like a lot of time. What I would check:

 - Is your pc usually that slow with other volumes rendering?

- Which resolution are you rendering?

- Which and how many lights do you have? Keep in mind that enviroment lights take longer to render than a directional or a point light for example

- In the light settings I would check the Sampling Quality if is still at 1

- Being the smoke fairly transparent is possible that Mantra thinks is all noise and is shooting every time the Max Ray Samples. I would also try to reduce this to 4-5 if you have it at an high number and set higher the noise level, just to see if this is the problem

Edited May 16, 2019 by Andrea

[lukeiamyourfather]

Rendering volumes with physically based lighting and shading is incredibly expensive. If you need fast render times then consider deep shadow maps instead of ray tracing for the lighting.

[willow wafflebeard]

i find that adding a volumelimit or geolights spikes volume renders up to 10 folds.  --check does out,  and if like internal scattering, go with geolight my test shows its atleast 2x faster than having a volume limit of 1

or  just add a glow in comp and don't do emissive lights, you'll be lightning fast

Edited June 17, 2019 by willow wafflebeard
spelling

[tinyhawkus]

Jesus, please don't use deep shadow maps, unless you want to go retro 2001 style.
Can we see a frame? Can you upload a single bgeo + your scene to have a look at?

Volume limit of 1 means 1 bounce of indirect, which is already pretty expensive as Mantra kinda sucks in that regard (but guess what, almost all of them
suck at volume bouncing, hello Arnold!), your volume light is doing a point cloud bake to simulate emissive illumination. So you don't want to be using it
as well as doing a volume bounce too. I would steer clear of using volume limit (volume bouncing) completely in Mantra, it is just too slow to be usable
unless the shot really calls for it. Use PBR mode, your env hdr, and a volume light.