Sorry if we weren't clear. I thought you'd "got" it. Here's a really simple example - a figure with two groups, one triangle in each. I've omitted UV coordinates and normals for clarity. v -0.05 0.00 0.00 v 0.05 0.00 0.00 v 0.05 0.10 0.00 v -0.05 0.10 0.00 g group1 f 3 4 1 g group2 f 2 3 1 So, an export of group1 would be the first, third and fourth vertices, in that order - not the order in which they're specified in the facet definition, but the order in which they appear in the v section. So, group1 exported would look like this: v -0.05 0.00 0.00 v 0.05 0.10 0.00 v -0.05 0.10 0.00 g group1 f 2 3 1 Vertex 2 from the orignal file is not required, so it's omitted from the v list. Vertices 3 and 4 are now renumbered as 2 and 3 respectively, and the facet definition changed accordingly.