Problem with pathtracing on Blender 3.1 & Luxcore 2.6

[Fomhorian]

.blend file:

Steps to reproduce:
When using Luxcore in pathtracing mode the caustics from a transparent object doesn't show on a base
surface, unless you flip the normal(s) of the base surface. Bidir works perfectly.

Screenshots or rendered images:

Error message from Blender console:
None.

OS: Win10
Blender version: 3.1 (& 3.01, possibly 2.93)
LuxCore version: 2.6 (& 2.5, don't know/remember about 2.4)

[Fomhorian]

The lower image has the "base surface", a cube, with its normals inverted. Hence the yucky beige & flat shading.

[foreachthing]

Silly question: do you have "Light Tracing" in "Render Properties -> Light Paths" active?

[Fomhorian]

Yup. Always. I generally don't goof around with the settings. I tried switching LightTracing off because of your mail, but apart from some serious fireflies, I still don't see any caustics akin to the bidir ones. Sincerely, T. Sandberg Den mån 21 mars 2022 22:27foreachthing ***@***.***> skrev:

…

Silly question: do you have "Light Tracing" in "Render Properties -> Light Paths" active? — Reply to this email directly, view it on GitHub <#758 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AYKV6ANQR43LKQTAWL3UDMTVBDSUJANCNFSM5RIOME5Q> . You are receiving this because you authored the thread.Message ID: ***@***.***>

[foreachthing]

I said it was a silly question 😄
Oh, I just checked, I got 2.61a0 installed. Maybe that made all the difference?!

[Fomhorian]

I got the latest build, 2.61a, too.😵‍💫 Den mån 21 mars 2022 23:04foreachthing ***@***.***> skrev:

…

I said it was a silly question 😄 Oh, I just checked, I got 2.61a0 installed. Maybe that made all the difference?! — Reply to this email directly, view it on GitHub <#758 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AYKV6ALA6MKX5U4SPZ7RCO3VBDXAFANCNFSM5RIOME5Q> . You are receiving this because you authored the thread.Message ID: ***@***.***>

[foreachthing]

Please try the simplest scene of'em all:

Blender 3.1 and LuxCore 2.61a0

Suzanne.zip

If that doesn't help, maybe you can upload your .blend?

[Fomhorian]

I found the culprit!!! When I add the material "Glossy Coating" to a base material; that's when PathTracing fails to produce caustics on that surface! =D Sincerely, T Sandberg (Yet again a happy toddler😁🐣) PS: I tried to add a Blend-file (at 4.5 mB), but the mail-system considered it too large! :DS Den tis 22 mars 2022 kl 07:42 skrev foreachthing ***@***.***>:

Please try the simplest scene of'em all: [image: image] <https://user-images.githubusercontent.com/10420187/159422587-6d3bedcf-556e-47ae-b737-1c0204e57449.png> Blender 3.1 and LuxCore 2.61a0 Suzanne.zip <https://github.com/LuxCoreRender/BlendLuxCore/files/8321776/Suzanne.zip> If that doesn't help, maybe you can upload your .blend? — Reply to this email directly, view it on GitHub <#758 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AYKV6AMEADZK24RXPUTMOFLVBFTWRANCNFSM5RIOME5Q> . You are receiving this because you authored the thread.Message ID: ***@***.***>

<https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail> Virusfritt. www.avast.com <https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail> <#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>

[foreachthing]

@Fomhorian, upload the zip on the website.
Good you found the issue.

But ...
Disney and glossy works (unless I am doing something wrong)

AND, carpaint! Carpaint doesn't want to work with glossy!

What are your thoughts?!

[CodeFHD]

Some notes from an updated review:

• Issue can be reproduced in latest version
• Using Suzanne test scene uploaded by foreachthing
• Matte material + glossy coating --> Caustics only with BiDir, not Path+Light
• Disney material + glossy coating --> Caustics with both engines,
• Follow-up analysis needed if this is expected behavior or a bug with either material combination

[odil24]

• Using Suzanne test scene uploaded by foreachthing
• Matte material + glossy coating --> Caustics only with BiDir, not Path+Light
  

• Disney material + glossy coating --> Caustics with both engines,