[Bf-blender-cvs] [849debe36c8] master: Fix T80970: Copy Rotation constraint incorrect under shear
Joseph Brandenburg
noreply at git.blender.org
Thu Nov 26 13:15:24 CET 2020
Commit: 849debe36c82f4a6bf94eb108de7a2d2fd2e35fb
Author: Joseph Brandenburg
Date: Thu Nov 26 13:11:23 2020 +0100
Branches: master
https://developer.blender.org/rB849debe36c82f4a6bf94eb108de7a2d2fd2e35fb
Fix T80970: Copy Rotation constraint incorrect under shear
Orthogonalize the constraint target's matrix before decomposing it into
Euler angles. This removes sheer, and is actually a requirement for
correct decomposition.
It's conceivable that someone has used the incorrect behaviour in a rig.
As the shear caused unpredictable flipping of the constrained object,
this is unlikely.
Reviewed By: angavrilov, sybren
Differential Revision: https://developer.blender.org/D8915
===================================================================
M source/blender/blenkernel/intern/constraint.c
===================================================================
diff --git a/source/blender/blenkernel/intern/constraint.c b/source/blender/blenkernel/intern/constraint.c
index 974d536d83e..bc918df84ed 100644
--- a/source/blender/blenkernel/intern/constraint.c
+++ b/source/blender/blenkernel/intern/constraint.c
@@ -1833,8 +1833,14 @@ static void rotlike_evaluate(bConstraint *con, bConstraintOb *cob, ListBase *tar
/* To allow compatible rotations, must get both rotations in the order of the owner... */
mat4_to_eulO(obeul, rot_order, cob->matrix);
/* We must get compatible eulers from the beginning because
- * some of them can be modified below (see bug T21875). */
- mat4_to_compatible_eulO(eul, obeul, rot_order, ct->matrix);
+ * some of them can be modified below (see bug T21875).
+ * Additionally, since this constraint is based on euler rotation math, it doesn't work well with shear.
+ * The Y axis is chosen as the main axis when we orthoganalize the matrix because constraints are
+ * used most commonly on bones. */
+ float mat[4][4];
+ copy_m4_m4(mat, ct->matrix);
+ orthogonalize_m4_stable(mat, 1, true);
+ mat4_to_compatible_eulO(eul, obeul, rot_order, mat);
/* Prepare the copied euler rotation. */
bool legacy_offset = false;
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