Raytrace shadow render optimization

#1

Hello all. The issue I have is render time. I have a fairly simple scene with a few objects on a table. I have two directional lights lighting my scene and I am fairly happy with it. In order to get good “un-noisy” shadows, I have had to crank my shadow rays all the way up to 100. This cause my render time to sky rocket up to about 6 min/frame.

Does anybody have tips or suggestions to get sexy looking shadows while maintaining a manageable render time?

Screenshots attached!!!

NOTE: The up close render is with shadow rays at 20.

#2

You should have a look at elementalray.com, they have an article there about area lights and optimisation.Instead of increasing the shadow ray count, you should set it to 4 or 6 and increase the unfied quality. You can increase it above 1.0, e.g. 3.0 and check if it works better.

#3

Thanks for your reply. I did try bumping up the Unified Sampling while reducing the Shadow Rays. It really didn’t effect my render times though. I now have turned off Final Gather to help diagnose this issue, but I not really getting anywhere. Currently my setting are as follows:

Two Directional Lights w/ Raytrace Shadows
Light Angle: 30
Shadow Rays: 8
Ray Depth: 1
Final Gather: OFF

Unified Sampling: 8

Render Time: 4min/frame

#4

6 min a frame isn’t too bad for a quality render

if you need faster than that and shadows are the issue, then I’d consider depth mapped shadows or lowering the shadows light angle radius

#5

Why directional lights for a render of a metallic surface? Since the ‘look’ of metal comes 99% from reflections, why not use proper area lights? Additionally, use the physical light shader and tune out unnecessary lighting that falls below a certain threshold. Then set your ‘shadow rays’ to 1 and use the sampling of the light to tune both lighting and ‘shadow’ quality at the same time along with unified. For simple scenes like this, you might get better performance from adaptive though. Unified really shines in more complex scenarios where adaptive performs poorly. But for simple things, you might get faster results from adaptive.

#6

I ‘concur’ with Sentry66; 6 minutes per frame is not bad at all.

You may be able to speed it up by using just the final gather and no lights/shadows, that’s what I do when I can. Lights that broad are inheriently very noisy and require tons of rays to clean up, while FG isn’t noisy at all