some of these were only returning a boolean, others returned a count even though only a boolean was needed.
split some of the functions in two as well where check/count are both needed.
- update face normals when triangulating.
- avoid divide by zero when interpolating customdata on a zero length edge.
- replace zero float comparisons with fabsf() < FLT_EPSILON to avoid numeric error.
also renamed BLI_heap_empty() --> BLI_heap_is_empty() so its obviously readonly function.
The direction for these are flipped from other end caps, so add a root
flag to indicate whether the cap polygon's vertex output order should be
reversed.
Fixes bug [#32079] Skin-modifier calculates root's normals wrong
projects.blender.org/tracker/index.php?func=detail&aid=32079&group_id=9&atid=498
Skin modifier documentation:
http://wiki.blender.org/index.php/User:Nicholasbishop/SkinModifier
Implementation based in part off the paper "B-Mesh: A Fast Modeling
System for Base Meshes of 3D Articulated Shapes" (Zhongping Ji,
Ligang Liu, Yigang Wang)
Note that to avoid confusion with Blender's BMesh data structure,
this tool is renamed as the Skin modifier.
The B-Mesh paper is current available here:
http://www.math.zju.edu.cn/ligangliu/CAGD/Projects/BMesh/
The main missing features in this code compared to the paper are:
* No mesh evolution. The paper suggests iteratively subsurfing the
skin output and adapting the output to better conform with the
spheres of influence surrounding each vertex.
* No mesh fairing. The paper suggests re-aligning output edges to
follow principal mesh curvatures.
* No auxiliary balls. These would serve to influence mesh
evolution, which as noted above is not implemented.
The code also adds some features not present in the paper:
* Loops in the input edge graph.
* Concave surfaces around branch nodes. The paper does not discuss
how to handle non-convex regions; this code adds a number of
cleanup operations to handle many (though not all) of these
cases.
