Commit: e2ec045cc995bb8767a5f88e8830aa1062921011
Author: Campbell Barton
Date: Tue Mar 19 16:50:18 2019 +1100
Branches: master
https://developer.blender.org/rBe2ec045cc995bb8767a5f88e8830aa1062921011
BLI_math: add utility to calculate compatible quaternions
===================================================================
M source/blender/blenlib/BLI_math_rotation.h
M source/blender/blenlib/intern/math_rotation.c
===================================================================
diff --git a/source/blender/blenlib/BLI_math_rotation.h
b/source/blender/blenlib/BLI_math_rotation.h
index 5246d7ad1a9..60adcf8c762 100644
--- a/source/blender/blenlib/BLI_math_rotation.h
+++ b/source/blender/blenlib/BLI_math_rotation.h
@@ -77,6 +77,8 @@ void add_qt_qtqt(float q[4], const float a[4], const float
b[4], const float t);
void quat_to_mat3(float mat[3][3], const float q[4]);
void quat_to_mat4(float mat[4][4], const float q[4]);
+void quat_to_compatible_quat(float q[4], const float a[4], const float old[4]);
+
void mat3_normalized_to_quat(float q[4], const float mat[3][3]);
void mat4_normalized_to_quat(float q[4], const float mat[4][4]);
void mat3_to_quat(float q[4], const float mat[3][3]);
diff --git a/source/blender/blenlib/intern/math_rotation.c
b/source/blender/blenlib/intern/math_rotation.c
index a348edaece8..d52c8f54096 100644
--- a/source/blender/blenlib/intern/math_rotation.c
+++ b/source/blender/blenlib/intern/math_rotation.c
@@ -201,6 +201,23 @@ void pow_qt_fl_normalized(float q[4], const float fac)
normalize_v3_length(q + 1, si);
}
+/**
+ * Apply the rotation of \a a to \a q keeping the values compatible with \a
old.
+ * Avoid axis flipping for animated f-curves for eg.
+ */
+void quat_to_compatible_quat(float q[4], const float a[4], const float old[4])
+{
+ BLI_ASSERT_UNIT_QUAT(a);
+ float delta[4];
+ float old_unit[4];
+ normalize_qt_qt(old_unit, old);
+ rotation_between_quats_to_quat(delta, old_unit, a);
+ mul_qt_qtqt(q, old, delta);
+ if ((q[0] < 0.0f) != (old[0] < 0.0f)) {
+ negate_v4(q);
+ }
+}
+
/* skip error check, currently only needed by mat3_to_quat_is_ok */
static void quat_to_mat3_no_error(float m[3][3], const float q[4])
{
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