SDS Caustics in a nutshell

[igmar75]

Hi,
first of all, thank you for Luxrender. It is invaluable.

I'm experimenting with specular-diffuse-specular caustics with Path Tracing and PhotonGI Caustic Cache. After some search and tests (maybe not enough..) I'm still confused about the minimal configuration required to see caustics through mirrors; attached, a not-working example. Is there someone able to give a very basic list of to-do in order to have the SDS caustics working with PhotonGI Caustic Cache?

Thank you!
Igmar

Blender v2.83.3
LuxCore 2.4
Win 10 64bit

[Sharlybg]

You have to make your twos cube renderable in the collection.

blend

Caustics_through_mirror.blend

(1006.9 KiB) Downloaded 137 times

[igmar75]

The caustic cannot be seen in the 3D Viewport?

[Sharlybg]

The caustic cannot be seen in the 3D Viewport?

SDS caustic is generated by caustic cache.It is a cached solution. only light traced caustic can be seen in the viewport because they are not cached but directly computed.

[B.Y.O.B.]

All caches currently in LuxCore are only computed for final renders.
It does not really make sense to compute them in the viewport because they would need to be re-computed on every geometry or material change, and cache computation is usually too expensive for real-time feedback.

[igmar75]

Thank you!
Igmar

[igmar75]

1) I continued experimenting, and I found a possible cause of confusion: even if I leave checked the "Caustic Light Cache" file (under "Persistence"), it is not updated! To update it, I have to change the cache file name; unflagging and flagging again the checkbox will not work. Attached you can find the test file. I think you should try to reproduce this behaviour on your machine..

2) Moreover, I noticed that I have to put the Roughness (of the big cylinder) to a value >0.25 to have it collecting caustics. This is not in agreement with the Glossiness Thresholds, whose value is 0.05.

Any idea?