Multi-Objects: MBALL_OT_select_similar

Compared to previous implementation, the following has been changed:
* Threshold: is now an absolute value. This allows a comparison with e.g. radii
  that are much larger than selected radius. This is also consistent with
  `CURVE_OT_select_similar`

* Radius in world space is the average of the radius scaled in x, y and z
  directions
* Since MetaBalls are symmetrical, rotation is only considered from 0 to π/2.
  So for example rotations of 90° and -90° are considered equal.
  This is also consistent with the way `CURVE_OT_select_similar` works.

Fix/changes from committer (Dalai Felinto):
* Drawing not updating after changes. (see original patch for details).

Reviewers: dfelinto
Differential Revision: https://developer.blender.org/D3895

1 files changed, 2 insertions, 0 deletions

diff --git a/source/blender/blenkernel/BKE_mball.h b/source/blender/blenkernel/BKE_mball.h
index ae86d978cb7..c09d3f3fba1 100644
--- a/source/blender/blenkernel/BKE_mball.h
+++ b/source/blender/blenkernel/BKE_mball.h
@@ -71,6 +71,8 @@ void BKE_mball_translate(struct MetaBall *mb, const float offset[3]);
 
 struct MetaElem *BKE_mball_element_add(struct MetaBall *mb, const int type);
 
+int BKE_mball_select_count(struct MetaBall *mb);
+int BKE_mball_select_count_multi(struct Object **objects, int objects_len);
 void BKE_mball_select_all(struct MetaBall *mb);
 void BKE_mball_select_all_multi(struct Object **objects, int objects_len);
 void BKE_mball_deselect_all(struct MetaBall *mb);