### When the top of a cut is not that simple

In the previous entry, I discussed how the silhouette of a cut, which would be a closed polygonal line, could be turned into a triangulated surface so these triangles could form a closed lid for the sliced triangular mesh.

But there are many cases when that surface is not that simple as a closed polygonal line. So the general case is a little bit more challenging. Let us see some sample cases in the image below:

So the simple case I talked about would be the circle label with the number 1. But the rest of the cases 2,3, and 4 are a bit trickier.

Case 2: We have a hole inside the exterior cut. That would be the result of cutting a tube-like shape. Here we do not want to cover the whole circle as in case number 1, but we want to keep the hole uncovered. Luckily, the Earcut library handles the cases where the external polygonal line encloses an area with one or more holes. But we still need to tell the library which points delimit the external perimeter and which ones are the perimeter of…

But there are many cases when that surface is not that simple as a closed polygonal line. So the general case is a little bit more challenging. Let us see some sample cases in the image below:

So the simple case I talked about would be the circle label with the number 1. But the rest of the cases 2,3, and 4 are a bit trickier.

Case 2: We have a hole inside the exterior cut. That would be the result of cutting a tube-like shape. Here we do not want to cover the whole circle as in case number 1, but we want to keep the hole uncovered. Luckily, the Earcut library handles the cases where the external polygonal line encloses an area with one or more holes. But we still need to tell the library which points delimit the external perimeter and which ones are the perimeter of…