Caustics on Car Paint doesn't work

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AcidNemesis
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Joined: Thu Dec 02, 2021 12:24 pm

Caustics on Car Paint doesn't work

Post by AcidNemesis » Thu Dec 02, 2021 1:00 pm

So I've added both Light-Tracing and Caustics cache to be sure, and after multiple attempts it still doesn't work. I won't be able to attach the file as it is too big but I'll bring an image of the render and the caustics pass.

https://imgur.com/a/4woZKW0
https://imgur.com/a/90ZvSIP

Edit : "[img]" doesn't work :/

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Dade
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Location: Italy

Re: Caustics on Car Paint doesn't work

Post by Dade » Thu Dec 02, 2021 3:32 pm

AcidNemesis wrote:
Thu Dec 02, 2021 1:00 pm
So I've added both Light-Tracing and Caustics cache to be sure, and after multiple attempts it still doesn't work. I won't be able to attach the file as it is too big but I'll bring an image of the render and the caustics pass.
Car paint is a glossy material and glossy material caustics are rendered only if you set the light tracing/cache glossiness threshold over the one used by the material (otherwise the material is excluded). If you post a scene of a cube over a plain with the carpaint material you are using, I can tell you how to set the threshold in order to render caustics.
AcidNemesis wrote:
Thu Dec 02, 2021 1:00 pm
https://imgur.com/a/4woZKW0
https://imgur.com/a/90ZvSIP

Edit : "[ img ]" doesn't work :/
It does but you need to use the link to an image (https://i.imgur.com/cK5GQWo.png and https://i.imgur.com/Dzng4qT.png), not to a web page:

Image
Image
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AcidNemesis
Posts: 4
Joined: Thu Dec 02, 2021 12:24 pm

Re: Caustics on Car Paint doesn't work

Post by AcidNemesis » Thu Dec 02, 2021 4:56 pm

Dade wrote:
Thu Dec 02, 2021 3:32 pm
Car paint is a glossy material and glossy material caustics are rendered only if you set the light tracing/cache glossiness threshold over the one used by the material (otherwise the material is excluded). If you post a scene of a cube over a plain with the carpaint material you are using, I can tell you how to set the threshold in order to render caustics.
https://drive.google.com/file/d/1SkV9da ... sp=sharing

Doing it the good old way with Google Drive ! I added a simple plane with some noise to get the caustics. Other than that I changed nothing in terms of settings.
Dade wrote:
Thu Dec 02, 2021 3:32 pm
It does but you need to use the link to an image (https://i.imgur.com/cK5GQWo.png and https://i.imgur.com/Dzng4qT.png), not to a web page
Oh thanks for that !

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Dade
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Location: Italy

Re: Caustics on Car Paint doesn't work

Post by Dade » Fri Dec 03, 2021 9:44 am

AcidNemesis wrote:
Thu Dec 02, 2021 4:56 pm
https://drive.google.com/file/d/1SkV9da ... sp=sharing

Doing it the good old way with Google Drive ! I added a simple plane with some noise to get the caustics. Other than that I changed nothing in terms of settings.
I'm not sure if you are really aware of what you are trying to render: your scene is illuminated only by caustic so it includes only SDS paths. And the light path of including carpaint is a (nearly) all specular path: all specular paths from not intersectable light sources, can not be rendered ... at all. However thanks to the "(nearly)", it can be done.

This is the original test scene:

im0.jpg

You have to:

1) disable light tracing (because it is not particular useful here and we need to use caustic cache anyway);
2) the caustic PhotonGI cache glossiness threshold to 0.0 (so car paint is not considered a specular material).

and you get:

im1.jpg

As you see, caustic on car paint start to be visible. In order to reduce the "blurriness", you may want also to:

1) set caustic cache photon count from 100000 to 500000
2) set caustic cache lookup radius from 0.075 to 0.05
3) set caustic cache min. radius from 0.075 to 0.02
4) set caustic cache radius reduction from 96% to 99%

and you get:

im2.jpg

P.S. I disabled sky2 light source in the test scene so the result is more clear.
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AcidNemesis
Posts: 4
Joined: Thu Dec 02, 2021 12:24 pm

Re: Caustics on Car Paint doesn't work

Post by AcidNemesis » Fri Dec 03, 2021 11:30 am

Thank you so much ! I'll try that as soon as I come back home ! I'll post a render of the final look !

AcidNemesis
Posts: 4
Joined: Thu Dec 02, 2021 12:24 pm

Re: Caustics on Car Paint doesn't work

Post by AcidNemesis » Fri Dec 03, 2021 8:55 pm

Okay so after tampering a bit with the values, I got something "satisfying", I can definitely do better but it's a great start, thanks again !
Attachments
Car with caustics
Car with caustics

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