OBJ import bug: Index out of range

[kintel]

The OBJ importer uses PolySetBuilder to track vertices. This causes duplicate vertices to be merged, but the indices used are taken directly from the file, indexing unmerged vertices, and if any duplicate vertex is found in the file, it will result in an index out of range error.

Example file (two cubes touching in one vertex):

v 0 0 0
v 0 0 1
v 0 1 0
v 0 1 1
v 1 0 0
v 1 0 1
v 1 1 0
v 1 1 1
v 1 1 1
v 1 1 2
v 1 2 1
v 1 2 2
v 2 1 1
v 2 1 2
v 2 2 1
v 2 2 2
f  4 1 2
f  1 6 2
f  1 4 3
f  7 1 3
f  6 1 5
f  1 7 5
f  6 4 2
f  4 6 8
f  4 7 3
f  7 4 8
f  7 6 5
f  6 7 8
f  12 9 10
f  9 14 10
f  14 12 10
f  9 12 11
f  15 9 11
f  12 15 11
f  14 9 13
f  9 15 13
f  15 14 13
f  12 14 16
f  15 12 16
f  14 15 16

Error importing the file:

WARNING: Index /Users/kintel/code/OpenSCAD/openscad/build/tests/output/objpngtest/polyhedrons-touch-vertex.scad.obj out of range in Line 40
WARNING: Index /Users/kintel/code/OpenSCAD/openscad/build/tests/output/objpngtest/polyhedrons-touch-vertex.scad.obj out of range in Line 41
WARNING: Index /Users/kintel/code/OpenSCAD/openscad/build/tests/output/objpngtest/polyhedrons-touch-vertex.scad.obj out of range in Line 42

The imported is missing a few triangles because of this.

[gsohler]

will propose easy fix to that soon