io_mesh_stl/blender_utils.py

   1 # SPDX-License-Identifier: GPL-2.0-or-later
   2
   3
   4 def create_and_link_mesh(name, faces, face_nors, points, global_matrix):
   5     """
   6     Create a blender mesh and object called name from a list of
   7     *points* and *faces* and link it in the current scene.
   8     """
   9
  10     import array
  11     from itertools import chain
  12     import bpy
  13
  14     mesh = bpy.data.meshes.new(name)
  15     mesh.from_pydata(points, [], faces)
  16
  17     if face_nors:
  18         # Note: we store 'temp' normals in loops, since validate() may alter final mesh,
  19         #       we can only set custom lnors *after* calling it.
  20         mesh.create_normals_split()
  21         lnors = tuple(chain(*chain(*zip(face_nors, face_nors, face_nors))))
  22         mesh.loops.foreach_set("normal", lnors)
  23
  24     mesh.transform(global_matrix)
  25
  26     # update mesh to allow proper display
  27     mesh.validate(clean_customdata=False)  # *Very* important to not remove lnors here!
  28
  29     if face_nors:
  30         clnors = array.array('f', [0.0] * (len(mesh.loops) * 3))
  31         mesh.loops.foreach_get("normal", clnors)
  32
  33         mesh.polygons.foreach_set("use_smooth", [True] * len(mesh.polygons))
  34
  35         mesh.normals_split_custom_set(tuple(zip(*(iter(clnors),) * 3)))
  36         mesh.use_auto_smooth = True
  37         mesh.free_normals_split()
  38
  39     mesh.update()
  40
  41     obj = bpy.data.objects.new(name, mesh)
  42     bpy.context.collection.objects.link(obj)
  43     bpy.context.view_layer.objects.active = obj
  44     obj.select_set(True)
  45
  46
  47 def faces_from_mesh(ob, global_matrix, use_mesh_modifiers=False):
  48     """
  49     From an object, return a generator over a list of faces.
  50
  51     Each faces is a list of his vertices. Each vertex is a tuple of
  52     his coordinate.
  53
  54     use_mesh_modifiers
  55         Apply the preview modifier to the returned liste
  56
  57     triangulate
  58         Split the quad into two triangles
  59     """
  60
  61     import bpy
  62
  63     # get the editmode data
  64     if ob.mode == "EDIT":
  65         ob.update_from_editmode()
  66
  67     # get the modifiers
  68     if use_mesh_modifiers:
  69         depsgraph = bpy.context.evaluated_depsgraph_get()
  70         mesh_owner = ob.evaluated_get(depsgraph)
  71     else:
  72         mesh_owner = ob
  73
  74     # Object.to_mesh() is not guaranteed to return a mesh.
  75     try:
  76         mesh = mesh_owner.to_mesh()
  77     except RuntimeError:
  78         return
  79
  80     if mesh is None:
  81         return
  82
  83     mat = global_matrix @ ob.matrix_world
  84     mesh.transform(mat)
  85     if mat.is_negative:
  86         mesh.flip_normals()
  87     mesh.calc_loop_triangles()
  88
  89     vertices = mesh.vertices
  90
  91     for tri in mesh.loop_triangles:
  92         yield [vertices[index].co.copy() for index in tri.vertices]
  93
  94     mesh_owner.to_mesh_clear()