Strange Artifacts in highres textures

[JonasNöll]

Fingers crossed

[kosso_olli]

Here is another example. The dark artifact on the left is caused by a very thin and long polygon.

[JonasNöll]

Does this also show up in IPR when zoomed in? For me it is only happening when the camera is further away and I render in highres. Or is it consistently there? Also, if the theory is correct then in V-Ray GPU the line should disappear (?)

[Joelaff]

We have gotten the same issue and narrowed it down to the long polys. Had to retopologize to solve it.

Interesting that it works fine in Scanline. Hopefully VRay can fix this.

[kosso_olli]

Does this also show up in IPR when zoomed in? For me it is only happening when the camera is further away and I render in highres. Or is it consistently there? Also, if the theory is correct then in V-Ray GPU the line should disappear (?)

The line is always there. It does not disappear with GPU.
Might be a different issue altogether, but at first I thought it was the same.

[kosso_olli]

We have gotten the same issue and narrowed it down to the long polys. Had to retopologize to solve it.

Interesting that it works fine in Scanline. Hopefully VRay can fix this.

I remember the thread, it was with Displacement, right?

[Joelaff]

I remember the thread, it was with Displacement, right?

Yes. You guys helped me figure it out.

I kept refusing to believe that long polys were the cause because most renderers have no trouble. But that’s exactly what it was! Since it was displacement the errors were very obvious.

[fixeighted]

Though displacement doesn't have that issue any more does it? I thought they fixed it....I remember topology being a real issue with displacement but it was years ago iirc.

[hermit.crab]

We tested this and it seems to occur in Arnold as well with geometry, which has thin and elongated polygons. We've logged the issue (internal bug-tracker id: VMAX-13720) for investigation.

[JonasNöll]

Oh really, how did you test that? Because in my test with the test scene you can find on page 1 of this thread Arnold renders without any issues. It seems to be a V-Ray related problem.

[hermit.crab]

By comparing your geometry to a regular plane geometry both assigned with the same shader and texture. Check the attached file.

[JonasNöll]

By comparing your geometry to a regular plane geometry both assigned with the same shader and texture. Check the attached file.

Hi, if I take your provided file it renders correctly with arnold, no matter if its the original geometry or the simplified geometry.

[^Lele^]

With V-Ray as renderer, type the following line in a maxscript window, and with the cursor at the end of the line press shift+enter.

renderers.current.system_embree_on = false

This will deactivate Intel Embree, reverting to V-Ray's own raycaster.
The issue will be gone, but memory usage and performance will change.
If the scene is heavy with geometry, it could potentially have important consequences, so be wary of it.
The change saves with the scene.

We're still not sure if it's something in our code, or with Embree, and the devs are still investigating.

[JonasNöll]

Perfect, this works! Thx!

[fixeighted]

Very interesting. I wonder if this solves the issues kosso_olli showed also.

In any case, good to know there's at least a workaround for it when geometry rebuilds aren't possible.