Merge branch 'fix-seeds-from_grid' into 'development'

correct calculation for origin

See merge request damask/DAMASK!837

python/damask/_grid.py

@@ -487,9 +487,11 @@ class Grid:
         size : sequence of float, len (3)
             Edge lengths of the grid in meter.
         seeds : numpy.ndarray of float, shape (:,3)
-            Position of the seed points in meter. All points need to lay within the box.
+            Position of the seed points in meter. All points need
+            to lay within the box [(0,0,0),size].
         weights : sequence of float, len (seeds.shape[0])
-            Weights of the seeds. Setting all weights to 1.0 gives a standard Voronoi tessellation.
+            Weights of the seeds. Setting all weights to 1.0 gives a
+            standard Voronoi tessellation.
         material : sequence of int, len (seeds.shape[0]), optional
             Material ID of the seeds.
             Defaults to None, in which case materials are consecutively numbered.
@@ -544,7 +546,8 @@ class Grid:
         size : sequence of float, len (3)
             Edge lengths of the grid in meter.
         seeds : numpy.ndarray of float, shape (:,3)
-            Position of the seed points in meter. All points need to lay within the box.
+            Position of the seed points in meter. All points need
+            to lay within the box [(0,0,0),size].
         material : sequence of int, len (seeds.shape[0]), optional
             Material ID of the seeds.
             Defaults to None, in which case materials are consecutively numbered.

python/damask/seeds.py

@@ -134,6 +134,12 @@ def from_grid(grid,
     coords, materials : numpy.ndarray, shape (:,3); numpy.ndarray, shape (:)
         Seed coordinates in 3D space, material IDs.
 
+    Notes
+    -----
+    The origin is not considered in order to obtain coordinates
+    in a coordinate system located at the origin. This is expected
+    by damask.Grid.from_Voronoi_tessellation.
+
     Examples
     --------
     Recreate seeds from Voronoi tessellation.
@@ -166,8 +172,8 @@ def from_grid(grid,
         materials = _np.unique(material[mask])
         coords_ = _np.zeros((materials.size,3),dtype=float)
         for i,mat in enumerate(materials):
-            pc = (2*_np.pi*coords[material[:,0]==mat,:]-grid.origin)/grid.size
-            coords_[i] = grid.origin + grid.size / 2 / _np.pi * (_np.pi +
+            pc = 2*_np.pi*coords[material[:,0]==mat,:]/grid.size
+            coords_[i] = grid.size / 2 / _np.pi * (_np.pi +
                          _np.arctan2(-_np.average(_np.sin(pc),axis=0),
                                      -_np.average(_np.cos(pc),axis=0))) \
                          if periodic else \