Caustics Issue

[philryan]

Hi all,

I'm having an issue rendering caustics in my scene.

If I isolate the geometry, it renders perfectly fine, however if I render it with everything that's in the scene turned on, it doesn't render correctly at all. As you  can see from the shadows, there is nothing 'blocking' the light from causing the caustics so I'm at a loss as to what could be causing the issue.

Any help at all would be greatly appreciated!

[mferster]

From my own tests, I have come to the conclusion that this happens because the caustics samples that were exclusively being used for the glass are now being spread out through out the entire scene and the caustics effect is lessened.

I could be totally wrong, but as far as I can tell the current caustics doesn't use adaptive techniques to concentrate samples on high impact caustics areas in renders. Or if it does, it isn't particularly effective.

For the time being, if you want a good caustic result you should isolate your scene like you did and and then combine your caustics passes in post.

[philryan]

I had a feeling that might be the case, but it's great to hear from someone else. That makes sense, thanks for your thoughts!

[maru]

One idea here would be to make sure the other objects in the scene generate as little reflective and refractive caustics as possible - so for example disabling reflectivity for some materials and/or using the rayswitch material to change some materials' appears to GI (for example removing reflectivity for GI rays only).

Other than that, you could try increasing the photon count in the development settings of the caustics solver which becomes available after enabling the development / experimental stuff rollout - https://coronarenderer.freshdesk.com/support/solutions/articles/12000021288

Just don't go too high with the photon count. Usually incrementally adding 5000 to the default 5000 is a good idea not to run out of RAM (10k, 15k, 20k, and so on...).