Strange Artifacts in highres textures

[JonasNöll]

Hi there,

I'm facing some issues which I somehow can't seem to fix. See attached images. In the rendering the texture is being distorted and some artifacts appear.
Here is what I tried already without any affect:

- Increase the Min/Max Subdivs to 64/64 and Noise treshold 0.001 in the rendersettings to make sure it's not a sampling issue
- Increased or decreased the FilterMult in the VRayBitmap
- used all interpolation options in the VRayBitmap
- used all filtering options in the VRayBitmap
- switches VRayBitmap to standard 3ds Max Bitmap
- used different file formats for the texture (jpg. png)

Always have the same issues appearing. Any advice?
Thx

[kosso_olli]

Can you share a small crop of that texture and the object it is assigned to?

[JonasNöll]

Hi,

I cropped away the other parts and saved just that part. Interesting the jagged lines now also appear on the cropping borders. So maybe it has something to do with the camera? It only shows up when rendering in high resolution in bucket rendering. So you always have to make a full rendering and then zoom in 100% to see the issues.

Cheers

[kosso_olli]

Hi,

I cropped away the other parts and saved just that part. Interesting the jagged lines now also appear on the cropping borders. So maybe it has something to do with the camera? It only shows up when rendering in high resolution in bucket rendering. So you always have to make a full rendering and then zoom in 100% to see the issues.

Cheers

The issue is caused by the triangulation of that object. The polies are too thin. We had this issue many many times, with no solution in sight.
On the right, I quickly remodeled the surface using an extruded spline shape and the texture is now crisp and clear.



Regards

Oliver

[JonasNöll]

Oh wow, the geometry Wouldn't have guessed that! I just tried to remodel and can confirm its fine now. So far never ran into that issue, but happy to know the solution now! Thx a lot for the help

[JonasNöll]

Seems to be a V-Ray issue, in 3ds Max Scanline it works fine even with the same highres object...

[kosso_olli]

Here is a crop from our first encounter with that problem. See the thin lines running from top to bottom? Those are caused by very thin polygons.

[JonasNöll]

Oh wow, I also had that in similar areas in the same project, but didn't know it is the same issue. Any workaround for more complex geometry which you can't easily remodel?
I probably would need to try to import lower polycount objects from the CAD data. But if I do some previous rounded corners become too lowres, so you can see the polygons and those parts. Headache...

[fixeighted]

Looks like an error in the CAD export/import to me, as it does happen for sure, but not with every object that has long polys.
Do you have a small piece that you can share for investigation?

[JonasNöll]

Hi,

sure, attached you can find a file. As said, it seems to be a V-Ray specific issue as the problem doesn't happen when using Standard Scanline Render.
It seems to be a combination of very dense long polygons + camera quite far away from the object and render in very high resolution. The geometry itself is ok, it just has dense and long polygons.

[kosso_olli]

Oh wow, I also had that in similar areas in the same project, but didn't know it is the same issue. Any workaround for more complex geometry which you can't easily remodel?

None that I know of. Maybe retopology would be worth a try, it's quite good in Max.

[kosso_olli]

Looks like an error in the CAD export/import to me, as it does happen for sure, but not with every object that has long polys.
Do you have a small piece that you can share for investigation?

From what I gathered during debugging of this, it is not related to the import/export.
The long thin lines should not be there. With some tesselators you can avoid this issue by specifying a maximum edge length, but if you get a step/iges and import that in Max, you do not have that parameter. Buying software like InstaLod, Polytrans or Vred is too expensive for the smaller jobs where you get just some small parts via step/iges.

[fixeighted]

Thanks.

I played with a few things and found that yes it seems to be Vray, though oddly only cpu, as gpu renders it just fine.
It's not even triangles causing it, as quads have the same result.
Maybe it's some sort of tolerance thing, as with cpu it can be pretty close to the camera and be fine, then starts to degrade as you zoom out. Weird.

A quick solution if you have a load of objects and can't remodel is to subdivide of course, though that may mess things up depending on the geometry you have.

[JonasNöll]

Thanks.

I played with a few things and found that yes it seems to be Vray, though oddly only cpu, as gpu renders it just fine.
It's not even triangles causing it, as quads have the same result.
Maybe it's some sort of tolerance thing, as with cpu it can be pretty close to the camera and be fine, then starts to degrade as you zoom out. Weird.

A quick solution if you have a load of objects and can't remodel is to subdivide of course, though that may mess things up depending on the geometry you have.

Yeah, but subdividing with converted CAD geometry is is not likely to succed and subdividable geometry probably doesn’t pose this issue
As you also mentioned it seems to be a V-Ray specific issue as other renderer such as Arnold and Scanline don't have the same issue. I agree the geometry could be optimized but other renderers are handling it just fine.

[fixeighted]

Maybe the devs will have a solution, given that GPU works fine...