diff --git a/interpolate_strokes/operators.py b/interpolate_strokes/operators.py
index c4082b8..30fad0c 100644
--- a/interpolate_strokes/operators.py
+++ b/interpolate_strokes/operators.py
@@ -3,7 +3,7 @@ import numpy as np
 from time import perf_counter, time, sleep
 from mathutils import Vector, Matrix
 
-from gp_interpolate.utils import (matrix_transform,
+from ..utils import (matrix_transform,
                                   plane_on_bone,
                                   ray_cast_point,
                                   obj_ray_cast,
diff --git a/utils.py b/utils.py
index b6090ca..4556295 100644
--- a/utils.py
+++ b/utils.py
@@ -84,6 +84,20 @@ def get_tri_from_face(hit_location, face_index, object_hit, depsgraph):
     return tri, tri_indices
 
 def ray_cast_point(point, origin, depsgraph):
+    '''Return object hit by ray cast, hit location and triangle vertices coordinates and indices
+
+    point: point coordinate in world space
+    origin: origin of the ray in world space
+    depsgraph: current depsgraph (use bpy.context.evaluated_depsgraph_get())
+
+    return:
+        object_hit (object): Object that was hit
+        hit_location (Vector3, as np.array): Location Vector of the hit
+        tri (list(Vector)): List of Vector3 world space coordinate of hitten triangle (tesselated from face if needed)
+        tri_indices (list(int)): List of vertices index corresponding to tri coordinates
+
+    if nothing hit. return None, None, None, None 
+    '''
     ray = (point - origin)
     hit, hit_location, normal, face_index, object_hit, matrix = bpy.context.scene.ray_cast(depsgraph, origin, ray)
     
@@ -479,4 +493,25 @@ def index_list_from_bools(bool_list) -> list:
 ## -- animation
 
 def is_animated(obj):
-    return True
\ No newline at end of file
+    return True
+
+
+## -- regions operations
+
+def location_to_region(worldcoords) -> Vector:
+    '''Get a world 3d coordinate and return 2d region coordinate
+    
+    return: 2d vector in region space
+    '''
+    from bpy_extras import view3d_utils
+    return view3d_utils.location_3d_to_region_2d(bpy.context.region, bpy.context.space_data.region_3d, worldcoords)
+
+def region_to_location(viewcoords, depthcoords) -> Vector:
+    '''Get 3d world coordinate from viewport region 2d coordianate
+    viewcoords (Vector2): 2d region vector coordinate
+    depthcoords (Vector3): 3d coordinate to define the depth
+
+    return: Vector3 of the placed location
+    '''
+    from bpy_extras import view3d_utils
+    return view3d_utils.region_2d_to_location_3d(bpy.context.region, bpy.context.space_data.region_3d, viewcoords, depthcoords)
\ No newline at end of file