Does having too many point lights suck all the energy out of other lights and the environment?

Support Lighting and Rendering
1

I downloaded a night scene that contained a lot of street lights.

I want to make it daytime so I added Nishita Sky Texture.

There seemed to be no shadows being cast by the sun in the sky texture.

I turned off all the lights:
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I see the shadows I expect from the sky texture’s sun

I turn on 3 lights deep inside of a building at the far end of the street. Everything gets a little darker.
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I turn on all lights that line the street and things get super dark:
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any idea what’s happening?

This happens in 2.92 as well as the 3.0 branch with the new version of Cycles.

I deleted all lights and recreated them from scratch. The problem still happens.

point lights disabled
point lights disabled960×540 136 KB

point lights enabled
point lights enabled960×540 117 KB

2

Are you doing regular path tracing? I bet branched path tracing solves that situation. It’s quite a big limitation thou. I hope a robust solution will be behind the corner for cycles x

3

Can you give more info about the actual limitation? I don’t understand what’s happening?

4

I don’t know the technical side, but I also faced this problem.
I think that branched path tracing can clear the issue since, by its design, for each sample the ray look for all lights in the scene, and not just a random one.

5

Keep in mind you can render out in different light passes and simply add the images together. For interior lights you can add a simple passthrough node group you can add as a dummy in world for easy access with the sun setup.

6

Have you tried disabling “Multiple Importance” on all of the point lights? It may result in more noisy image, but may solve problem with “light sucking”.

7

yes. no improvement.

8

Ans what about using branched path tracing?

9

yes branched path tracing works but only is available on CPU. The cpu in the laptop I’m using at the moment is slower than cpu in 7 year old macbook. No fun.

10

Hopefully cycles x will tackle this once for all. They removing BPT in favor of regular path tracing and of course they know what they’re doing: I miss the technical part but something like sampling all light will be used, or at least the result will be like that.
Actually I’m not sure how I know this…