Missing triangles when importing large GLB terrain meshes into SketchUp

Technical Problems SketchUp
1

Hi everyone,

I’m developing a macOS application that converts GeoTIFF elevation data into GLB terrain meshes for use in SketchUp.

I’ve spent quite a bit of time debugging this, and I’m now trying to determine whether I’m running into a limitation or bug in SketchUp’s GLB importer.

Here are my observations:

  • Small terrain meshes (around 100 × 100 m) import perfectly.
  • Around 200–300 m square, a few random triangles start disappearing.
  • Larger terrain meshes show progressively more missing triangles.
  • The missing faces appear random rather than following any obvious pattern.

Things I have already verified:

  • No missing vertices.
  • No degenerate triangles.
  • Correct triangle indices.
  • Correct normals.
  • Correct winding order.
  • Valid GLB structure (buffers, bufferViews, accessors, alignment, etc.).
  • The exact same GLB renders perfectly in Apple’s Preview application with no missing faces.

Additional observations:

  • Simplifying the imported mesh using Skimp still produces missing triangles.
  • The issue appears to become worse as the mesh size increases.

My question is:

Has anyone experienced SketchUp randomly dropping triangles on large triangulated GLB meshes?

Is there a known limitation in the GLB importer regarding:

  • very large triangle counts?
  • very large connected meshes?
  • triangle aspect ratios?
  • vertex precision?
  • something else?

I’d also be interested to know if anyone has compared importing the same terrain as OBJ versus GLB, and whether one format behaves more reliably.

Any ideas or experiences would be greatly appreciated.

Thanks!

2

SketchUp has an internal vertex tolerance of 0.001". Any points closer will be treated as coincident.

SketchUp also cannot create very small faces whose sides are very short. Search the forum on “small face problem”.

I would encourage you to instead create a bona fide extension that runs within SketchUp and uses the Geom::PolygonMesh class and Sketchup::Importer interface.