Rendering with forest, wireframe+triangulation shown as black lines

[GO6827]

Hi
I'm having some issues with forest pack pro (9.2.1, but same problem on previous versions). When rendering with forest elements, the wireframe and triangulation appears as black lines on my geometry. I've attached images of the problem. The left car is merged into the scene and the red box is a standard box with 12x12x12 segments.
When rendering without forest elements in my scene there isn't a problem, but when adding a forest object (right car, same model as the merged on the left), the render is showing black lines on all of the geometry. The two renders are the exact same scene, just with and without forest element (and the Railclone that is used to reference the cars onto). 3ds max 2025 and Vray 7 hotfix 2, but same problem on max 2024 and Vray 6. The scene uses a daylight system, no effects added, just basic Vray setup.
The third image is with an override material where the problem persist. If I remove the forest element, the scene is rendering out normal again.

[Michal Karmazín]

Hi,

If possible, please feel free to send us your scene - preferably simplified and containing only the problematic object(s). Ideally, if you can reproduce it in a minimal scene, it would be greatly appreciated. Thanks in advance.

Best regards,

[GO6827]

Thanks Michal, I've sent the scene to you.

[iToo]

We asked to the Chaos team about this issue:

The geometry is located quite far away from the scene origin - the car pivot for example is at (3850,241m, 11923,396m, 33,2m). That causes various numerical issues here and there.
V-Ray has a mechanism to avoid this problem, translating all objects near from the origin. But it requires to be supported for all objects and plugins.
In this case Forest doesn't support it, because we didn't know about this mechanism.

We'll try to implement it for next updates. Meanwhile, i would suggest to move scene objects near the origin, if possible. That should fix the artifacts.

Regards,

[GO6827]

Thank you for looking into the issue, nice to have an idea of what the problem is. The project is a long stretch of road, so unfortunately it's not an option to move it closer to origin. Do you have a timeline on a fix?

[iToo]

No idea, sorry. We have to study how this mechanism works, and if it's possible to implement it in Forest or not.

[iToo]

We have fixed the issue in our development build, but it requires further testing.

If you want to test it in your scene, please tell me your Max version, and i will send you a custom patch.

[GO6827]

Thanks, I'm on 3ds max 2026.

[iToo]

Sent by e-mail.
You will find patches for Forest Pack and RailClone, since both are necessary to fix the problem.

[GO6827]

Yay Itoosoft!
It works like a charm, will do further testing on another scene. Thank you for the quick response!

[GO6827]

Minor error, when using the IPR, the lines are shown. The GPU render is not affected.
EDIT: 3ds max 2026 and Forest 9.2.4 and RailClone 6.4.3

[iToo]

You're right. I can confirm it's not working for IPR CPU.
Please, hold on. I just wrote to Chaos about it.

[iToo]

Well, they replied quickly: the mechanism to avoid triangulation lines is not supported on IPR.

[GO6827]

Fair enough. Good to know.