Ticket #6488 - Cone surface returns wrong dv derivative

[jnxd]

This might have some implications in https://forum.freecadweb.org/viewtopic.php?f=10&t=20261.

[wmayer]

The OCC bug has been fixed now. However, their solution looks a bit different and it should be checked if our suggested fix works correctly in all cases.

[wmayer]

@tanderson69
Have a look at how OCC has fixed the problem.

You can see the differences when computing the derivatives for DN(u, v, 1, 1).

I have applied the fix to our workaround and implemented a unit test to compare the results of the cone and its conversion to a NURBS: git commit b02705d79f

[tanderson69]

@tanderson69
Have a look at how OCC has fixed the problem.

You can see the differences when computing the derivatives for DN(u, v, 1, 1).

I have applied the fix to our workaround and implemented a unit test to compare the results of the cone and its conversion to a NURBS: git commit b02705d79f

Yeah I looked at occt's fix afterwards and realized what they are trying to do with that function. My occt branch is rebased onto official branches, so after their fix makes into a release I will simply skip my commit.