Polysurface triangle artifacts

I am puzzling with strange artifacts on very simple triangular surfaces joint into polysrf. At very first I thought it is just a display bug, but after converting into mesh, it takes this “Artifact” as a real geometry. Any ideas? Model is in meters, tolerance 0.001, graphic drivers up to date…

what happen if you extract or explode thos surfaces and run _RebuildEdges?

Do you see the artifact with the original geometry (not converted to mesh) in Wireframe mode? If not then it is not in the original geometry.

How big is the object? What is the length of the side with the gap?

How far from the origin?

What were the setting used for the mesh conversion? What setting in Options > Mesh? Unless the mesh conversion settings are different I would expect the mesh conversion to be the same as the render mesh. The best way to visually check the geometry is to use Wireframe mode.

thanks for the suggestion. Interesting things are happening. After hitting rebedge command, the geometry changes. See the pictures. But still don’t understand this behaviour of very simple surfaces.

Hi David,
see the wireframe and shaded display modes. Problem is these artifacts affect the geometry itself - the control points are at the same place as the “artifacts”. The object itself lays on the word origin - so I guess there is no problem with this.

It looks to me like render mesh artifacts. The wireframe shows the edges of the surface geometry. The shaded surfaces are the render mesh which approximates the surface.

Are any surfaces trimmed? If so the trimmed edge will be away from the control points.

How large is the object in your images?

Please post a .3dm file with your object if possible.

I remember having similar issues with triangles only, the nurbs are ok but the mesh doesn’t. other alternative could be change the degree to 2 or 3.

Hi David,
I also thought it is only render mesh…But after unrolling the surface, there is visible “fail” in the geometry. After running rebuild edge, bad triangles always adjust to the “shaded” outline. I tried working in metres and mm, but every now and then the problem appears.

Surfaces are trimmed as they are triangles. I will post the file later this day.


I’ve just noticed that the problem is when I want to join more trimmed surfaces (triangles). Seems like I am missing some typological basics here :slight_smile: