If you encounter this error when importing CAD files, it may be due to the model's geometry.
In most cases this due to a "poor geometry" conversion to polygons from the CAD software.
This type of poor geometry may render successfully when using offline software to render still images, but real-time render engines like BRIO require clean sets of polygons and UVs to work properly. AR devices have even stricter requirements for clean geometry to function without errors.
What does it mean to have poor geometry?
"Poor geometry", technically referred to as Degenerate geometry & Non Manifold geometry, includes the following issues:
- Degenerate polygons are those that have zero area.
- A degenerate surface is a surface that is collapsed to a line or point.
- Non-manifold geometry is s a 3D shape that cannot be unfolded into a 2D surface with all its normals pointing in the same direction.
A polygon is degenerate if some of its vertices lie on each other. e.g the triangle (0,0),(0,1),(0,0) is degenerate. It has 3 sides and 3 vertices, but two of the vertices repeat. It's possible to repeat a vertex multiple times (for example (0,0),(0,0),(0,0) is another degenerate triangle).
Improving CAD model geometry
By definition, checking whether a polygon is degenerate or not is easy. Basically, it means a surface that lacks the usual properties needed in order to function well as a surface in a CAD application. This is due to the fact that the math does not work as expected.
Export STEP from your CAD software and use products like MOI or Fusion 360 to convert into better, clean geometry.