Hi Danny,

> Isn't N-gons the same as just quads?

On an untrimmed surface they will be the same - that's because the mesher starts out with quads that come from the subdivided underlying surface.

If the trim curves on the surface are aligned with the natural boundaries of the underlying surface, then you'll get an all quad mesh for that case.

But if you have trim curves that are not aligned with the underlying mesh's UV directions then those trim curves will basically trim the surface quad and become an n-gon. That's for areas near a trim boundary - pieces of the surface that do not intersect the trim boundary will be quads.

The easiest example that I can show to help explain it is the image I posted above:



Here the top cap surface is a simple plane surface that is trimmed to an irregular outline.

It's easy to see in this example that the n-gon formed by the top cap has a lot of points in its boundary, it's made up of many edges and is not just a quad. There are still quads in other areas though like the side wall parts which is an untrimmed surface (trim curves on it are the natural edges of the underlying surface).

So an "all quad" mesh is a much different kind of mesh than an "n-gon" mesh, I hope this example helps illustrate the difference.

- Michael