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[Python][IfcOpenShell][BlenderBIM] Using an edge mesh to create IfcWallType instances

1. C by Coen on 2 Sep 2022, edited 6 Sep 2022 # +1 votes

   I have drawn a random mesh in blender like so:

   

   Found this script wich gets the coordinates from the mesh:

   
   import bpy, bmesh
   
   obj = bpy.context.active_object
   
   
   if obj.mode == 'EDIT':
   
       # this works only in edit mode,
   
       bm = bmesh.from_edit_mesh(obj.data)
   
       verts = [vert.co for vert in bm.verts]
   
   
   else:
   
       # this works only in object mode,
   
       verts = [vert.co for vert in obj.data.vertices]
   
   
   # coordinates as tuples
   
   plain_verts = [vert.to_tuple() for vert in verts]
   
   print(plain_verts)
   

   It returns a list of coordinates

   
   ... truncated[(9.0, 0.0, 0.0), (9.0, 7.0, 0.0), (5.0, 7.0, 0.0), (5.0, 8.0, 0.0), (0.0, 8.0, 0.0), (0.0, 0.0, 0.0), (-2.0, 4.0, 0.0)]
   

   I would like these coordinates to place IfcWallType instances from the IFC4 Demo Library,

   When creating a new IFC project I see the following command

   
   bpy.ops.bim.assign_class(   obj="Wall", 
   
                               ifc_class="IfcWall",
   
                               ifc_representation_class="IfcExtrudedAreaSolid/IfcArbitraryClosedProfileDef")
   

   Which places a wall instance at the origin point. I can't find programmaticaly how to place a lot of walltype instances with this list of coordinates, or if it's even possible? How would the script now where to place the wall? I take it from each vertice coordinates? Then how would the script know where to stop?

2. C by Coen on 2 Sep 2022 # +1 votes

   

   

   

   Almost there, I think I need to order the vertices...?

   This is what I came up with so far in general.

   
   def create_wall(coordinates, building_storey_height):
   
       print ("create wall")  
   
   
   
       extrusion=(building_storey_height)
   
       elevation = (building_storey.Elevation)
   
   
   
       ifc_wall    = ifcopenshell.api.run("root.create_entity", ifc_file, ifc_class="IfcWall", name="wall_from_edge" )
   
       ifc_walltype= ifcopenshell.api.run("root.create_entity", ifc_file, ifc_class="IfcWallType")
   
       ifcopenshell.api.run("type.assign_type", ifc_file, related_object=ifc_wall, relating_type=ifc_walltype) 
   
   
   
       coordinate_list = []
   
       for coordinate in coordinates:
   
           point = ifc_file.createIfcCartesianPoint( (coordinate))
   
           coordinate_list.append(point)
   
   
   
       wall_line    = ifc_file.createIfcPolyline(coordinate_list)
   
       ifcclosedprofile = ifc_file.createIfcArbitraryClosedProfileDef("AREA", None, wall_line) 
   
       ifc_direction    = ifc_file.createIfcDirection(Z)
   
   
   
       point = ifc_file.createIfcCartesianPoint((0.0,0.0,0.0))
   
       dir1 = ifc_file.createIfcDirection((0., 0., 1.))
   
       dir2 = ifc_file.createIfcDirection((1., 0., 0.))
   
   
   
       axis2placement = ifc_file.createIfcAxis2Placement3D(point, dir1, dir2)
   
       wall_solid = ifc_file.createIfcExtrudedAreaSolid(ifcclosedprofile,  axis2placement, ifc_direction, extrusion)
   
   
   
   
   
   
       shape_representation    = ifc_file.createIfcShapeRepresentation( ContextOfItems=context,
   
                                                                       RepresentationIdentifier='Body', 
   
                                                                       RepresentationType='SweptSolid',
   
                                                                       Items=[wall_solid])
   
   
   
   
   
       ifcopenshell.api.run("geometry.assign_representation", ifc_file, product=ifc_walltype, representation=shape_representation)
   
       ifcopenshell.api.run("spatial.assign_container", ifc_file, product=ifc_wall, relating_structure=building_storey) 
   
   
   
   create_wall(coordinates=plain_verts, building_storey_height=3.0)  
   
   

3. T by theoryshaw on 6 Sep 2022, edited 6 Sep 2022 # +1 votes

   found the following script on the internets, to reorder vertices

   
   obj = bpy.context.active_object
   
   
   def reordered(bm):
   
       f = bmesh.ops.contextual_create(
   
               bm,
   
               geom=bm.verts[:] + bm.edges[:],
   
               )["faces"][0]
   
   
       for i, v in enumerate(f.verts):
   
           v.index = i
   
       bm.verts.sort()
   
       bm.faces.remove(f)
   
       return bm
   
   
   if obj.mode == 'EDIT':
   
       # this works only in edit mode,
   
       bm = bmesh.from_edit_mesh(obj.data)
   
       reordered(bm)
   
       verts = [vert.co for vert in bm.verts]
   
   else:
   
       # this works only in object mode,
   
       reordered(bm)
   
       verts = [vert.co for vert in obj.data.vertices]
   

4. B by brunopostle on 6 Sep 2022 # +2 votes

   I think that the natural way to draw a wall in blenderbim should be to draw vertical faces rather than horizontal lines:

   1. Collections of blender lines don't have any 'direction'. You can string them together programmatically, but walls have inside and outside, so you want to control the direction.

   2. Faces in blender have a normal direction, the inside and outside is implicit

   3. Not all walls have horizontal tops and bottoms, attics, under stairs, stepped footings etc.. in IFC this should be represented by a simple vertically extruded wall with half space clipping at the top and bottom. I can't imagine any intuitive way of specifying these clipping solids directly. But deriving them from a face geometry is doable.

5. B by brunopostle on 6 Sep 2022 # +1 votes
   4. This is how it works in the Homemaker add-on. It probably doesn't make sense to transfer all the Homemaker functionality into blenderbim, but this is an obvious one.

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