[Octave-patch-tracker] [patch #8951] Calculate vertexnormals for patch objects

[Pantxo Diribarne]

Follow-up Comment #13, patch #8951 (project octave):

As you are now a frequent contributor, it would be even better if you asked
for tests on the help/maintainers mailing lists. This is the best way to do
clean reverse engineering. Generally answers come in a few hours.

>>Do I understand correctly that Matlab only triggers the calculation of
FaceNormals if the patches have polygons with more than 3 corners? 

Yes, that is what I mean, but I concluded too fast, the test in comment 10
shows that ML computes normals even for flat lighting. So I don't know what
went wrong with those tests.

On the other hand, I think the reason why vertexnormals are not computed for
"flat" lighting is because vertexnormals don't have a unique value here: I'd
bet when two faces share vertices - say [abc] and [bcd] are triangular faces
with "b" and "c" common vertices - the rendering in opengl uses actually 6
vertices (no triangle strip/fan) - [abc] and [b'c'd]. In flat lighting "b" and
"c" inherit the facenormals of face "abc" while "b'" and "c'" inherit from
"bcd" facenormals (hence vertexnormals has no sense).

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