LuxCoreRender Forums

I've got 2 issues when trying to render caustics with the cache and light tracing.

First issue is the fireflies. These paths really should be disabled because the caustics are handled by both the cache and light tracing, but there presence make my renders basically unusable.

Second issue is that the brightness of the caustics doesn't seem to be correct. The material of the cube is 100% reflective, so the caustic and reflection of the caustic should be the same brightness, yet the reflection is noticeably brighter. This may be an issue with the metropolis estimation, but I'm not entirely sure about it

The scene attached below used a daily build from a day ago, and a daily build of Blender 2.90

In Blender 2.9 i have several issues, especially crashes when using Mantaflow, but also with Luxcore.
So i recommend to stick - at least when there are problems - with 2.83.

These issues persist when using 2.83
This isn't an issue with blender, it's an issue with LuxCore

jgrover110 wrote: Mon Jul 13, 2020 10:51 am First issue is the fireflies. These paths really should be disabled because the caustics are handled by both the cache and light tracing, but there presence make my renders basically unusable.

I suspect it's the Light Tracing, but I can't really speak to that.

jgrover110 wrote: Mon Jul 13, 2020 10:51 am Second issue is that the brightness of the caustics doesn't seem to be correct. The material of the cube is 100% reflective, so the caustic and reflection of the caustic should be the same brightness, yet the reflection is noticeably brighter. This may be an issue with the metropolis estimation, but I'm not entirely sure about it

I get the same result as you. Blender 2.83, LuxCore 2.4 beta 1


If I use PhotonGI only (no Light Tracing), at 12K samples, the brightness is equal, although it does seem like it might be a little too bright overall?

If I disable the PhotonGI cache and use Light Tracing, the result is still quite noisy at 12K samples; the brightness is equal.

If I disable the Light Tracing as well (pure path tracing), the brightness is equal, although a little noisier at 12K samples.

With BiDir Metropolis at 2K samples I get almost the correct brightness, it's just a little brighter in the reflection.

With BiDir Sobol at 2K samples I get equal brightness, it's just... very noisy and will take a long time to converge.

Conclusion:

In 2 of the 3 cases where Metropolis was used (BiDir, Light Tracing + PhotonGI) the brightness was not equal. However, when Light Tracing was used on its own, the brightness was equal.

With Light Tracing + PhotonGI the result feels quite like their contributions are additive, so you get the brightness from PhotonGI, plus the brightness from Light Tracing.


Hope this helps