Fix: Apply tilt in curves data-block normals calculation

The ported normal calculation from ceed37fc5cbb466a0 neglected to
use the tilt attribute to rotate the normals around the tangents.
This commit adds that behavior back, adding a new math header file
to avoid duplicating the rotation function for normalized axes.

Differential Revision: https://developer.blender.org/D14655

1 files changed, 18 insertions, 0 deletions

diff --git a/source/blender/blenlib/BLI_math_rotation.hh b/source/blender/blenlib/BLI_math_rotation.hh
new file mode 100644
index 00000000000..e8b746b34df
--- /dev/null
+++ b/source/blender/blenlib/BLI_math_rotation.hh
@@ -0,0 +1,18 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+#pragma once
+
+/** \file
+ * \ingroup bli
+ */
+
+#include "BLI_math_vec_types.hh"
+
+namespace blender::math {
+
+/**
+ * Rotate the unit-length \a direction around the unit-length \a axis by the \a angle.
+ */
+float3 rotate_direction_around_axis(const float3 &direction, const float3 &axis, float angle);
+
+}  // namespace blender::math