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I recently tested sun and light caustics and the results seem strange to me. Am I wrong to expect the caustics to spread/light on the sss (milk preset) accordingly?





cheers

Daniel

are you used environement in the second image ?

looks like just have to wait some time ... day , two days , max 3 years

Could you send me this scene please?

Mihai wrote:Could you send me this scene please?

pm sent;)

It's the same "specular seen on specular" problem, so yes as Zdeno says it will take a really long time to show up, or you could raise the roughness of the SSS and then it will appear much quicker. Perhaps blend a 20 or so roughness duplicate of the SSS bsdf with a 0 roughness one....or, a second Layer set to additive with a rough bsdf, the layer weighted low so it doesn't influence too much the look of the base SSS.

Just tried now and then caustics appear on the surface of the SSS quickly - with either a copy of the SSS bsdf and set to roughness 20, or a second layer set to additive. But you'll have to compromise between how much of an influence you want these to have on your original SSS and how strong you want the caustics to appear on the surface.

Here just adding a second BSDF, a glass type one with the same ND as the SSS one, and roughness set to 80, weight to 50. Of course it will change the look of the SSS itself a bit. But you can lower its influence if you only want a small hint of caustics seen on the SSS. Bottom render is your original material.

Thank you very much Mihai. So is the presetshader of the Milk (and the other sss materials) lacking this extra layer? shouldn't it be included to act as natural/realistic as possible?

I mean I expect the caustics to penetrate volumetrically and light up the milk from the inside, not just show up on the surface.

Well no, my material is the unnatural one

The idea is you need to add something rough to the mix, so that the caustics will start to show up on the surface.

Caustics on specular surface = really long time to become visible
Caustics on surface with roughness = caustics will show up very fast

so you mean in my scene the caustics will show up eventually and clean? I mean the top image with the physical sun.

I am looking for the caustics to scatter into the sss volume, not appear on the surface as per the roughness approach;)

Yes I realized It should appear to light up the inside as well eventually, I will check further....

I rendered both in coop on 9 machines, up to SL 25 (merged). Shall I render it on one machine only up to SL 30-40?

I guess it's the same problem as caustics seen through dielectric adding a bit more complexity with the dispersion of the sss.

Well, if the caustics appear at all and act as they should, I am fine. Just need to know what is an appropriate SL to expect them to be clearly visible. Currently at SL 25 I don't see a hint, so I thought there is some different error on my side..

You can't even see any bright dots showing up yet at SL 25?