Merge pull request #924 from compas-dev/mesh-strip-split

Mesh split strip

Author: tomvanmele

CHANGELOG.md

@@ -11,6 +11,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 * Added halfedge loops in `compas.datastructures.Halfedge.halfedge_loop`.
 * Added halfedge strips in `compas.datastructures.Halfedge.halfedge_strip`.
+* Added `compas.datastructures.mesh_split_strip` and `compas.datastructures.Mesh.split_strip`.
 * Added boundingbox to `compas_rhino.conduits.BaseConduit`
 
 ### Changed

src/compas/datastructures/__init__.py

@@ -108,6 +108,7 @@
     mesh_smooth_centroid
     mesh_split_edge
     mesh_split_face
+    mesh_split_strip
     mesh_subdivide_catmullclark
     mesh_subdivide_corner
     mesh_subdivide_doosabin
@@ -246,6 +247,7 @@
     mesh_smooth_centroid,
     mesh_split_edge,
     mesh_split_face,
+    mesh_split_strip,
     mesh_subdivide_catmullclark,
     mesh_subdivide_corner,
     mesh_subdivide_doosabin,
@@ -385,6 +387,7 @@
     'mesh_smooth_centroid',
     'mesh_split_edge',
     'mesh_split_face',
+    'mesh_split_strip',
     'mesh_subdivide_catmullclark',
     'mesh_subdivide_corner',
     'mesh_subdivide_doosabin',

src/compas/datastructures/mesh/mesh.py

@@ -45,6 +45,7 @@
 from .operations import mesh_collapse_edge
 from .operations import mesh_split_edge
 from .operations import mesh_split_face
+from .operations import mesh_split_strip
 from .operations import mesh_merge_faces
 
 from .bbox import mesh_bounding_box
@@ -122,6 +123,7 @@ class Mesh(HalfEdge):
     smooth_area = mesh_smooth_area
     split_edge = mesh_split_edge
     split_face = mesh_split_face
+    split_strip = mesh_split_strip
     subdivide = mesh_subdivide
     transform = mesh_transform
     transformed = mesh_transformed

src/compas/datastructures/mesh/operations/split.py

@@ -2,10 +2,13 @@
 from __future__ import absolute_import
 from __future__ import division
 
+from compas.utilities import pairwise
+
 
 __all__ = [
     'mesh_split_edge',
     'mesh_split_face',
+    'mesh_split_strip',
     'trimesh_split_edge',
 ]
 
@@ -222,3 +225,39 @@ def mesh_split_face(mesh, fkey, u, v):
     del mesh.face[fkey]
 
     return f, g
+
+
+def mesh_split_strip(mesh, edge):
+    """Split the srip of faces corresponding to a given edge.
+
+    Parameters
+    ----------
+    mesh : :class:`compas.datastructures.Mesh`
+        The input mesh.
+    edge : tuple of int
+        The edge identifying the strip.
+
+    Returns
+    -------
+    list of int
+        The split vertices in the same order as the edges of the strip.
+    """
+    strip = mesh.edge_strip(edge)
+    is_closed = strip[0] == strip[-1]
+
+    ngons = []
+    splits = []
+    for u, v in strip[:-1]:
+        ngons.append(mesh.halfedge_face(u, v))
+        splits.append(mesh.split_edge(u, v, t=0.5, allow_boundary=True))
+
+    if is_closed:
+        splits.append(splits[0])
+    else:
+        u, v = strip[-1]
+        splits.append(mesh.split_edge(u, v, t=0.5, allow_boundary=True))
+
+    for (u, v), ngon in zip(pairwise(splits), ngons):
+        mesh.split_face(ngon, u, v)
+
+    return splits

tests/compas/datastructures/test_halfedge.py

@@ -4,6 +4,7 @@
 import compas
 
 from compas.geometry import Sphere
+from compas.geometry import Box
 
 from compas.datastructures import HalfEdge
 from compas.datastructures import Mesh
@@ -47,6 +48,13 @@ def sphere():
     return mesh
 
 
+@pytest.fixture
+def box():
+    box = Box.from_corner_corner_height([0, 0, 0], [1, 1, 0], 1.0)
+    mesh = Mesh.from_shape(box)
+    return mesh
+
+
 @pytest.fixture
 def grid():
     mesh = Mesh.from_meshgrid(dx=10, nx=10)
@@ -358,3 +366,31 @@ def test_loops_and_strips_open_boundary(grid):
         assert edge == strip[-1]
     else:
         assert edge == strip[0]
+
+
+def test_split_strip_closed(box):
+    edge = box.edge_sample()[0]
+
+    box.split_strip(edge)
+
+    assert box.is_valid()
+    assert box.number_of_faces() == 10
+
+
+def test_split_strip_open(grid):
+    edge = grid.edge_sample()[0]
+
+    grid.split_strip(edge)
+
+    assert grid.is_valid()
+    assert grid.number_of_faces() == 110
+
+
+def test_split_strip_open_corner(grid):
+    corner = list(grid.vertices_where({'vertex_degree': 2}))[0]
+
+    for edge in grid.vertex_edges(corner):
+        grid.split_strip(edge)
+
+    assert grid.is_valid()
+    assert grid.number_of_faces() == 121