Fix T91253: Slow pose bone selection with many bones

Viewport cull bones during selection to avoid depth-picking
reading the depth buffer for bones that aren't in the viewport.

Files with thousands of bones could hang blender for seconds while
selecting. The issue could still happen with overlapping bones or when
zoomed out so all bones are under the cursor, however in practice this
rarely happens.

Now files with many bones select quickly.

Related changes include:

- Split `BKE_pchan_minmax` out of `BKE_pose_minmax`.
- Add `mat3_to_size_max_axis` to return the length of the largest
  axis (used for scaling the radius).

Reviewed By: sybren

Maniphest Tasks: T91253

Ref D13990

1 files changed, 14 insertions, 0 deletions

diff --git a/source/blender/blenlib/BLI_math_matrix.h b/source/blender/blenlib/BLI_math_matrix.h
index 03b6ff25a4f..1dcc1c1df49 100644
--- a/source/blender/blenlib/BLI_math_matrix.h
+++ b/source/blender/blenlib/BLI_math_matrix.h
@@ -431,6 +431,20 @@ void mat3_to_size(float size[3], const float M[3][3]);
 void mat4_to_size(float size[3], const float M[4][4]);
 
 /**
+ * Return the largest scale on any axis, the equivalent of calling:
+ * \code{.c}
+ * mat3_to_size(size_v3, mat);
+ * size = size_v3[max_axis_v3(size_v3)];
+ * \endcode
+ * .. without 2x unnecessary `sqrtf` calls.
+ */
+float mat3_to_size_max_axis(const float M[3][3]);
+/**
+ * Only the first 3 axes are used.
+ */
+float mat4_to_size_max_axis(const float M[4][4]);
+
+/**
  * Extract scale factors from the matrix, with correction to ensure
  * exact volume in case of a sheared matrix.
  */