Karma slower (and noisier) than Mantra - PYRO VOLUME LIGHTS

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Hi everyone.

I'm trying to render something in Karma to test out volume lights, it is a fire sim and i want volume lights in it.

For Mantra, i'm simply using a geo light with the point cloud settings (16 point samples)on my pyro sim.

For Karma, i'm sopimporting the pyro sim, giving it it's materials and then using a rendergeometrysettings with treat as light enabled with the following settings: Light source diffuse 16 and light source specular 1.

For render settings, Mantra is set to default and completely untouched, i'm getting 57 seconds on this one frame.

For Karma, primary samples are set to 20 (from the 9 default) and minimum samples is set to 1. (Motion blur and depth of field options are also unchecked) and i'm getting a noisier result as well as a longer render time at 1 minute and 37 seconds.

I've attached both frames, as well as the way the stages is currently set up.

Am i doing something wrong with trying to render a volume light this way through Karma, or does Karma suffer when it comes to geo/volumes lights as a whole?

Thanks

(First pic is mantra, second is karma)



Edited by K3DFX - Sept. 23, 2022 18:44:58

Attachments:
mantra.png (1.2 MB)
karma.png (1.3 MB)
set.png (72.4 KB)

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I noticed too that volumes are pretty noisy in Karma. Not using it because of that for volumes.
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Hi. Karma's volume rendering is broadly faster than mantra, but volume lights may be faster in mantra: mantra's volume lights are a pointcloud-based approximation that produces very biased results. Karma aims to produce much more accurate results but it may come at an added cost.
In cases such as above where the volume is close to surface receiving emission, I might recommend disabling "treat as lightsource" entirely and rely on indirect bounces instead (and enable it in cases where the volumes are difficult/unlikely to be sampled by indirect rays, e.g. faraway sources or thin trails).
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