BLI_math: axis_angle_to_quat_single

Useful to avoid defining a vector for an axis-aligned rotation.
Matches axis_angle_to_mat3_single behavior.

1 files changed, 14 insertions, 0 deletions

diff --git a/source/blender/blenlib/intern/math_rotation.c b/source/blender/blenlib/intern/math_rotation.c
index 575710e8d75..949473a8d86 100644
--- a/source/blender/blenlib/intern/math_rotation.c
+++ b/source/blender/blenlib/intern/math_rotation.c
@@ -1016,6 +1016,20 @@ void angle_to_mat2(float mat[2][2], const float angle)
 	mat[1][1] =  angle_cos;
 }
 
+void axis_angle_to_quat_single(float q[4], const char axis, const float angle)
+{
+	const float angle_half = angle * 0.5f;
+	const float angle_cos = cosf(angle_half);
+	const float angle_sin = sinf(angle_half);
+	const int axis_index = (axis - 'X');
+
+	assert(axis >= 'X' && axis <= 'Z');
+
+	q[0] = angle_cos;
+	zero_v3(q + 1);
+	q[axis_index + 1] = angle_sin;
+}
+
 /****************************** Exponential Map ******************************/
 
 void quat_normalized_to_expmap(float expmap[3], const float q[4])