dual_mesh.py

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#
#  This program is free software; you can redistribute it and/or
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#  as published by the Free Software Foundation; either version 2
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import bpy
import math

from sverchok.node_tree import SverchCustomTreeNode
from sverchok.data_structure import (match_long_repeat)
from sverchok.utils.sv_bmesh_utils import bmesh_from_pydata, dual_mesh
from sverchok.utils.nodes_mixins.sockets_config import ModifierNode

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_faces = []

    def calc_angle(co, orth, co_orth, face_idx):
        face_center = new_verts[face_idx]
        direction = face_center - co
        dx = direction.dot(orth)
        dy = direction.dot(co_orth)
        return math.atan2(dy, dx)

    # 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
        normal = vert.normal
        orth = normal.orthogonal()
        co_orth = normal.cross(orth)
        face_idxs = [face.index for face in vert.link_faces]
        new_face = sorted(face_idxs, key = lambda idx : calc_angle(vert.co, orth, co_orth, idx))
        new_face = list(new_face)

        m = len(new_face)
        if m > 2:
            new_faces.append(new_face)

    vertices = [new_verts[idx] for idx in sorted(new_verts.keys())]
    return vertices, new_faces

class SvDualMeshNode(ModifierNode, SverchCustomTreeNode, bpy.types.Node):
    """
    Triggers: 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')

    @property
    def sv_internal_links(self):
        return [
            (self.inputs[0], self.outputs[0]),
            (self.inputs[2], self.outputs[1]),
        ]

    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, normal_update=True)
            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)