Other than implementing a `mid_v3_v3_array` function, this removes
`cent_tri_v3` and `cent_quad_v3` in favor of `mid_v3_v3v3v3` and
`mid_v3_v3v3v3v3` respectively.
Reviewed By: mont29
Differential Revision: https://developer.blender.org/D2459
This commit lands the core backend of the Custom Manipulators project onto the blender2.8 branch. It is a generic backend for managinig interactive on-screen controls that can be integrated into any 2D or 3D edito. It's also already integrated into the window-manager and editor code where needed.
NOTE: The changes here should not be visible for users at all. It's really just a back-end patch. Neither does this include any RNA or Python integration.
Of course, there's still lots of work ahead for custom manipulators, but this is a big milestone. WIP code that actually uses this backend can be found in the 'custom-manipulators' branch (previously called 'wiggly-widgets').
The work here isn't completely my own, all the initial work was done by @Antony Riakiotakis (psy-fi) and - although it has changed a lot since them - it's still the same in essence. He definitely deserves a big credit! Some changes in this patch were also done by @Campbell Barton (campbellbarton). Thank you guys!
Merge accepted by @brecht and @merwin.
Patch: https://developer.blender.org/D2232
Code documentation: https://wiki.blender.org/index.php/Dev:2.8/Source/Custom_Manipulator
Main task: https://developer.blender.org/T47343
More info: https://code.blender.org/2015/09/the-custom-manipulator-project-widget-project/
Issue was in BLI's rotation_between_vecs_to_quat(), which did not handled correctly cases where both vectors are colinear.
Patch by Campbell Barton and me.
Issue originaly tracked down by Yan Shi, many thanks!
rather then getting the longest edge, get the edge which which is most different from the 2 others ends up giving more useful results: for an isosceles triangle it returns the base weather its longer or shorter then the other sides.
