+
+/* apply a rotation from the perspective of root */
+static void keyframe_rotate_around( mdl_keyframe *kf,
+ v3f origin, v3f offset, v4f q )
+{
+ v3f v0, co;
+ v3_add( kf->co, offset, co );
+ v3_sub( co, origin, v0 );
+ q_mulv( q, v0, v0 );
+ v3_add( v0, origin, co );
+ v3_sub( co, offset, kf->co );
+
+ q_mul( q, kf->q, kf->q );
+ q_normalize( kf->q );
+}
+