Tutorial for PolyfaceΒΆ

The Polyface entity represents a 3D mesh build of vertices and faces and is just an extended POLYLINE entity with a complex VERTEX structure. The Polyface entity was used in DXF R12 and older DXF versions and is still supported by newer DXF versions. The new Mesh entity stores the same data much more efficient but requires DXF R2000 or newer. The Polyface entity supports only triangles and quadrilaterals as faces the Mesh entity supports n-gons.

Its recommended to use the MeshBuilder objects to create 3D meshes and render them as POLYFACE entities by the render_polymesh() method into a layout:

import ezdxf
from ezdxf import colors
from ezdxf.gfxattribs import GfxAttribs
from ezdxf.render import forms

cube = forms.cube().scale_uniform(10).subdivide(2)
red = GfxAttribs(color=colors.RED)
green = GfxAttribs(color=colors.GREEN)
blue = GfxAttribs(color=colors.BLUE)

doc = ezdxf.new()
msp = doc.modelspace()

# render as MESH entity
cube.render(msp, dxfattribs=red)
cube.translate(20)

# render as POLYFACE a.k.a. POLYLINE entity
cube.render_polyface(msp, dxfattribs=green)
cube.translate(20)

# render as unconnected 3DFACE entities
cube.render_3dfaces(msp, dxfattribs=blue)

doc.saveas("meshes.dxf")
../_images/mesh_cubes.png

Warning

If the mesh contains n-gons the render methods for POLYFACE and 3DFACES subdivides the n-gons into triangles, which does not work for concave faces.

The usage of the MeshBuilder object is also recommended for inspecting Polyface entities:

  • MeshBuilder.vertices is a sequence of 3D points as ezdxf.math.Vec3 objects

  • a face in MeshBuilder.faces is a sequence of indices into the MeshBuilder.vertices sequence

import ezdxf
from ezdxf.render import MeshBuilder

def process(mesh):
    # vertices is a sequence of 3D points
    vertices = mses.vertices
    # a face is a sequence of indices into the vertices sequence
    faces = mesh.faces
    ...

doc = ezdxf.readfile("meshes.dxf")
msp = doc.modelspace()
for polyline in msp.query("POLYLINE"):
    if polyline.is_poly_face_mesh:
        mesh = MeshBuilder.from_polyface(polyline)
        process(mesh)