I think the difference in your tests comes from the fact that some vertices are not rendered at all, since they are out of the camera range. You create the vertices using random coordinates, including negative numbers, so some vertices will be out of sight for the camera.
EDIT: Nm, your camera is at -100, so all vertices are visible :)
But perhaps overlapping vertices cause the vertices behind not to be rendered?
Hmm, SeedRnd Millisecs() still makes it error out at 15700, so it has nothing to do with the random vertices.
EDIT: Nm, your camera is at -100, so all vertices are visible :)
But perhaps overlapping vertices cause the vertices behind not to be rendered?
Hmm, SeedRnd Millisecs() still makes it error out at 15700, so it has nothing to do with the random vertices.