Merge pull request #2653 from nortikin/dual_mesh

Dual mesh node

Merge pull request #2653 from nortikin/dual_mesh
Dual mesh node
e9c3df54 · Ilya V. Portnov · GitHub · 31db2e51 · 90b3576e · e9c3df54
--- a/docs/nodes/modifier_make/dual_mesh.rst
+++ b/docs/nodes/modifier_make/dual_mesh.rst
+Dual Mesh
+=========
+
+Functionality
+-------------
+
+This node generates dual mesh for the given mesh. Dual mesh is defined as a
+mesh which has vertices at center of each face of source mesh; edges of the
+dual mesh connect the vertices, which correspond to faces of original mesh with
+common edge.
+
+This node may be useful to convert the mesh consisting of Tris to mesh
+consisting to NGons, or backwards.
+
+Note that the volume of dual mesh is always a bit smaller than that of original mesh.
+
+Inputs
+------
+
+This node has the following inputs:
+
+- **Vertices**. Vertices of original mesh. This input is mandatory.
+- **Edges**. Edges of original mesh.
+- **Faces**. Faces of original mesh. This input is mandatory.
+
+Outputs
+-------
+
+This node has the following outputs:
+
+- **Vertices**. Vertices of the dual mesh.
+- **Faces**. Faces of the dual mesh.
+
+Examples of Usage
+-----------------
+
+Dual mesh for cube is an octahedron:
+
+.. image:: https://user-images.githubusercontent.com/284644/68086032-278bb800-fe69-11e9-80d5-5b46bde8d9b0.png
+
+Dual mesh for Voronoi diagram is Delaunay triangulation:
+
+.. image:: https://user-images.githubusercontent.com/284644/68086114-fcee2f00-fe69-11e9-95f5-d57f03dbbf0f.png
+
--- a/docs/nodes/modifier_make/modifier_make_index.rst
+++ b/docs/nodes/modifier_make/modifier_make_index.rst
@@ -23,3 +23,5 @@ Modifier Make
   contour2D
   fractal_curve
   convex_hull_mk2
+   dual_mesh
+
--- a/index.md
+++ b/index.md
@@ -126,6 +126,7 @@
    Voronoi2DNode
    SvOffsetLineNode
    SvContourNode
+    SvDualMeshNode
    ---
    SvBevelCurveNode
    SvAdaptiveEdgeNode

--- a/nodes/modifier_make/dual_mesh.py
+++ b/nodes/modifier_make/dual_mesh.py
+# ##### BEGIN GPL LICENSE BLOCK #####
+#
+#  This program is free software; you can redistribute it and/or
+#  modify it under the terms of the GNU General Public License
+#  as published by the Free Software Foundation; either version 2
+#  of the License, or (at your option) any later version.
+#
+#  This program is distributed in the hope that it will be useful,
+#  but WITHOUT ANY WARRANTY; without even the implied warranty of
+#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+#  GNU General Public License for more details.
+#
+#  You should have received a copy of the GNU General Public License
+#  along with this program; if not, write to the Free Software Foundation,
+#  Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+#
+# ##### END GPL LICENSE BLOCK #####
+
+import operator
+
+import bpy
+from mathutils import Matrix, Vector
+
+from bpy.props import IntProperty, FloatProperty, EnumProperty
+from sverchok.node_tree import SverchCustomTreeNode
+from sverchok.data_structure import (Vector_generate, updateNode,
+                                     match_long_repeat)
+from sverchok.utils.sv_bmesh_utils import pydata_from_bmesh, bmesh_from_pydata, dual_mesh
+
+class SvDualMeshNode(bpy.types.Node, SverchCustomTreeNode):
+    """
+    Trigers: Dual Mesh
+    Tooltip: Create dual mesh for the given mesh
+    """
+    bl_idname = 'SvDualMeshNode'
+    bl_label = "Dual Mesh"
+    bl_icon = 'OUTLINER_OB_EMPTY'
+    sv_icon = 'SV_DUAL_MESH'
+
+    def sv_init(self, context):
+        self.inputs.new('SvVerticesSocket', 'Vertices')
+        self.inputs.new('SvStringsSocket', 'Edges')
+        self.inputs.new('SvStringsSocket', 'Faces')
+
+        self.outputs.new('SvVerticesSocket', 'Vertices')
+        self.outputs.new('SvStringsSocket', 'Faces')
+
+    def process(self):
+        if not any((s.is_linked for s in self.outputs)):
+            return
+
+        verts_s = self.inputs['Vertices'].sv_get()
+        edges_s = self.inputs['Edges'].sv_get(default=[[]])
+        faces_s = self.inputs['Faces'].sv_get()
+
+        verts_out = []
+        faces_out = []
+
+        objects = match_long_repeat([verts_s, edges_s, faces_s])
+        for verts, edges, faces in zip(*objects):
+            bm = bmesh_from_pydata(verts, edges, faces)
+            new_verts, new_faces = dual_mesh(bm)
+            bm.free()
+            new_verts = [tuple(v) for v in new_verts]
+            verts_out.append(new_verts)
+            faces_out.append(new_faces)
+
+        self.outputs['Vertices'].sv_set(verts_out)
+        self.outputs['Faces'].sv_set(faces_out)
+
+def register():
+    bpy.utils.register_class(SvDualMeshNode)
+
+
+def unregister():
+    bpy.utils.unregister_class(SvDualMeshNode)
+
--- a/ui/icons/sv_dual_mesh.png
+++ b/ui/icons/sv_dual_mesh.png
--- a/ui/icons/svg/sv_dual_mesh.svg
+++ b/ui/icons/svg/sv_dual_mesh.svg
+<?xml version="1.0" encoding="UTF-8" standalone="no"?>
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+
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+   xmlns:svg="http://www.w3.org/2000/svg"
+   xmlns="http://www.w3.org/2000/svg"
+   xmlns:sodipodi="http://sodipodi.sourceforge.net/DTD/sodipodi-0.dtd"
+   xmlns:inkscape="http://www.inkscape.org/namespaces/inkscape"
+   width="64"
+   height="64"
+   viewBox="0 0 16.933333 16.933334"
+   version="1.1"
+   id="svg8"
+   inkscape:version="0.92.2 (5c3e80d, 2017-08-06)"
+   sodipodi:docname="sv_dual_mesh.svg"
+   inkscape:export-filename="/home/portnov/src/sverchok_280/ui/icons/sv_dual_mesh.svg.png"
+   inkscape:export-xdpi="96"
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+     borderopacity="1.0"
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+     id="metadata5">
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+         rdf:about="">
+        <dc:format>image/svg+xml</dc:format>
+        <dc:type
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+        <dc:title></dc:title>
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+  </metadata>
+  <g
+     inkscape:label="Layer 1"
+     inkscape:groupmode="layer"
+     id="layer1"
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+</svg>
--- a/utils/sv_bmesh_utils.py
+++ b/utils/sv_bmesh_utils.py
@@ -161,3 +161,61 @@ def remove_doubles(vertices, edges, faces, d):
    v, e, p =pydata_from_bmesh(bm)
    bm.free()
    return v, e, p
+
+def dual_mesh(bm, recalc_normals=True):
+    # Make vertices of dual mesh by finding
+    # centers of original mesh faces.
+    new_verts = dict()
+    for face in bm.faces:
+        new_verts[face.index] = face.calc_center_median()
+
+    #new_edges = []
+    new_faces = []
+
+    # For each vertex of original mesh,
+    # find all connected faces and connect
+    # corresponding vertices of the dual mesh
+    # with a face.
+    # The problem is, that the order of edges in
+    # vert.link_edges (or faces in vert.link_faces)
+    # is undefined, so we have to sort them somehow.
+    for vert in bm.verts:
+        if not vert.link_faces:
+            continue
+        face0 = vert.link_faces[0]
+        new_face = [face0.index]
+        other_faces = set(vert.link_faces[:])
+        n = len(vert.link_faces)
+        while other_faces:
+            n = n-1
+            if n <= 0:
+                break
+            for edge in vert.link_edges:
+                if face0 in edge.link_faces:
+                    fcs = [face for face in edge.link_faces if face != face0]
+                    if not fcs:
+                        continue
+                    other_face = fcs[0]
+                    if other_face in other_faces:
+                        face0 = other_face
+                        other_faces.remove(face0)
+                        if face0.index not in new_face:
+                            new_face.append(face0.index)
+
+        if len(new_face) > 2:
+            new_faces.append(new_face)
+
+    vertices = [new_verts[idx] for idx in sorted(new_verts.keys())]
+    # We cannot guarantee that our sorting above gave us faces
+    # of original mesh in counterclockwise order each time.
+    # So if we want normals of dual mesh to be consistent,
+    # we have to call bmesh.ops.recalc_face_normals.
+    if not recalc_normals:
+        return vertices, new_faces
+    else:
+        bm2 = bmesh_from_pydata(vertices, [], new_faces, normal_update=True)
+        bmesh.ops.recalc_face_normals(bm2, faces=bm2.faces)
+        new_vertices, new_edges, new_faces = pydata_from_bmesh(bm2)
+        bm2.free()
+        return new_vertices, new_faces
+