I've been experimenting with the export to wavefront .obj file option in Blender, and I had the following two questions: 1) In what kind of situations might you want to use the group by materials option so as to make there be (as far as I can tell) one group for each combination of a material and object? 2) Here's an example output (no texture coordinates / normals). In this instance vertices 1-8 are used in the face statements for the 1st object, and vertices 9-16 are used in the face statements for the 2nd object. Is there ever a situtation in which a 2nd object is liable to reference vertices from the 1st object (ie object 2 accessing vertex #8?) When would this occur - a shared vertex between objects? How much of a rarity would it be? mtllib group_experiment_Scene.mtl g Left_Cube.002 v 8.000000 -1.737355 -1.000000 v 8.000000 -1.737355 1.000000 v 6.000000 -1.737355 1.000000 v 6.000000 -1.737355 -1.000000 v 8.000000 0.262645 -0.999999 v 8.000000 0.262645 1.000001 v 6.000000 0.262645 1.000000 v 6.000000 0.262645 -1.000000 usemtl Material s off f 1 2 3 4 f 5 8 7 6 f 1 5 6 2 f 2 6 7 3 f 3 7 8 4 f 5 1 4 8 g Right_Cube.001 v -5.000000 -0.737355 -1.000000 v -5.000000 -0.737355 1.000000 v -7.000000 -0.737355 1.000000 v -7.000000 -0.737355 -1.000000 v -5.000000 1.262645 -1.000000 v -5.000000 1.262645 1.000001 v -7.000000 1.262645 1.000000 v -7.000000 1.262645 -1.000000 usemtl (null) s off f 9 10 11 12 f 13 16 15 14 f 9 13 14 10 f 10 14 15 11 f 11 15 16 12 f 13 9 12 16