Curves: new Grow/Shrink brush

This adds a new Grow/Shrink brush which is similar to the Length
brush in the old hair system.
* It's possible to switch between growing and shrinking by hold
  down ctrl and/or by changing the direction enum.
* 3d brush is supported.
* Different brush falloffs are supported.
* Supports scaling curves uniformly or shrinking/extrapolating
  them. Extrapolation is linear only in this patch.
* A minimum length settings helps to avoid creating zero-sized curves.

Differential Revision: https://developer.blender.org/D14474

1 files changed, 18 insertions, 0 deletions

diff --git a/source/blender/blenlib/BLI_math_geom.h b/source/blender/blenlib/BLI_math_geom.h
index 9e65093a05f..5c1b6c8d774 100644
--- a/source/blender/blenlib/BLI_math_geom.h
+++ b/source/blender/blenlib/BLI_math_geom.h
@@ -329,6 +329,24 @@ float closest_to_line_segment_v2(float r_close[2],
                                  const float p[2],
                                  const float l1[2],
                                  const float l2[2]);
+
+/**
+ * Finds the points where two line segments are closest to each other.
+ *
+ * `lambda_*` is a value between 0 and 1 for each segment that indicates where `r_closest_*` is on
+ * the corresponding segment.
+ *
+ * \return Squared distance between both segments.
+ */
+float closest_seg_seg_v2(float r_closest_a[2],
+                         float r_closest_b[2],
+                         float *r_lambda_a,
+                         float *r_lambda_b,
+                         const float a1[2],
+                         const float a2[2],
+                         const float b1[2],
+                         const float b2[2]);
+
 /**
  * Point closest to v1 on line v2-v3 in 3D.
  *