I've attached a comparison picture where, what the model should look like is on the left and what I'm generating is on the right. You can see that I'm missing parts of the green area. The green and blue are part of the same shell, and when I'm iterating through all the faces for this shell, I do come across some that do not have triangulation data, and have confirmed that their color is green. I use BRepMesh_IncrementalMesh to generate the data. As far as I understand, iterating through shape topology is the way to obtain polygon data. Am I missing something?