Dear Author,
I would like to inform you that the posted problem has been checked and partly reproduced. We confirm the existence of a triangulation problem in the resulting shape, but it differs from the provided description. The triangulation problem is reproducible for revolution surface only if slice angle is <= 180 degree. Starting and ending faces looks well. See the corresponding pictures for case 1 and case 2 in attached zip file.
Draw reproducer (for case 1):
pload MODELING AISV
vertex v1 0 10 0
vertex v2 0 10 10
vertex v3 0 0 -10
edge e1 v1 v2
edge e2 v2 v3
edge e3 v3 v1
wire w1 e1 e2 e3
plane pln 0 10 0 1 0 0
mkface f1 pln
add w1 f1
don f1
revol r f1 0 10 0 0 0 1 180
fit
checkshape r
vinit
vsetdispmode 1
vdisplay r
vfit
The corresponding issue with ID = 22818 has been registered for this case.
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Regards