### 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.

#### Solution

Export STEP from your CAD software and use products like MOI or Fusion 360 to convert into better, clean geometry.