#379 g-stl export error for simple symmetric offset blocks

[JacobP]

I'm trying to learn and figure out BRL-CAD and am just combining two unit blocks with the second offset by half the width

mged -c test.g in BLOCK1 arb8 0 0 0 0 1 0 1 1 0 1 0 0 0 0 1 0 1 1 1 1 1 1 0 1
mged -c test.g in BLOCK2 arb8 0.5 0.5 0.5 0.5 1.5 0.5 1.5 1.5 0.5 1.5 0.5 0.5 0.5 0.5 1.5 0.5 1.5 1.5 1.5 1.5 1.5 1.5 0.5 1.5
mged -c test.g r COJ1 u BLOCK1 u BLOCK2

This works fine but exporting to STL does not seem to work unless the offset is unsymmetric (about 0.501 or so) with the error

g-stl -o test.stl test.g COJ1

{BLOCK1} u {BLOCK2}
class_eu_vs_s(): eu vu has classification status OUTSIDE
class_eu_vs_s(): eumate vu has classification status INSIDE
class_eu_vs_s(): wrote nmg_class0.plot3

class_eu_vs_s():  edge didn't get cut

FAILED in boolean evaluation: /COJ1
0 triangles written

I have tried permutation of the vertices but nothing seems to work, but maybe I have missunderstood how something works?

[John Anderson]

A test for parallel in nmg_isect_2faceuse() was incorrect and was flagging faces as parallel when they were not. Revision #73377 corrects this.