How to get full geometry information from Brep when IFCPRODUCTDEFINITIONSHAPE has multiple IFCSHAPEREPRESENTATION?

[sennhvi]

How to get full geometry information from Brep when IFCPRODUCTDEFINITIONSHAPE has multiple IFCSHAPEREPRESENTATION?

I have viewed some pages, like trying use settings to show Brep data --
https://blenderbim.org/docs-python/ifcopenshell/geometry_settings.html#disable-triangulation, but I don't know how to use the output and seems the output doesnot contains all vertices I need(what i really care).

#2744 gave me some inspiration that maybe I need to use sth like setting up a MODEL_VIEW to get all the geometry data.

When I use code below, I only get geometry data from the first SHAPEREPRESENTATION.

import ifcopenshell
import ifcopenshell.geom
import  ifcopenshell.util.shape

test_file = r'a-window.ifc'
ifc_file = ifcopenshell.open(test_file)
window = ifc_file.by_type('IfcBuildingElement')[0]

settings = ifcopenshell.geom.settings()
shape = ifcopenshell.geom.create_shape(settings, window)
matrix = ifcopenshell.util.shape.get_shape_matrix(shape)
location = matrix[:,3][0:3]


verts = shape.geometry.verts
edges = shape.geometry.edges
faces = shape.geometry.faces

a-window.ifc.txt

verts is a tuple contains 24 float number which stands for 8 3d points.

Stuck in how to get all verts\edges\faces in Brep. Any idea is welcome:)

[sennhvi]

The comparison pic shows that the missing geometry is necessary.

[aothms]

Yes, but that's a bit of a given in IFC. Depending on the use case you can have either very little or very detailed information on a window. And not always these different aspects of the window are semantically related because modellers predominantly care about the documenting the physical characteristics and not so much delineate on a functional level what a single window constitutes.

[sennhvi]

Thanks for your reply, I can understand what you described, so I tried to handle this kind of artifact with multiple shapeRepresentations via geometry iterator, but found that the artifact's shaperepresentation property access during iteration is discontinuous, is this normal?

This meant that I couldn't stitch together geometry data that belonged to the same component during iteration

[sennhvi]

@aothms Hi, I just found a very useful parameter -- rep, it was previously neglected due to the lack of documentation and insufficient exploration of the source code.

representations = product.Representation.Representations
for rep in representations:
    shape = ifcopenshell.geom.create_shape(settings, product, rep)

By setting the third parameter, I can get specific representation's geometry and now this window show perfectly!

Thanks again for your reply!

[aothms]

rep, it was previously neglected due to the lack of documentation

To be honest I also forgot a bit about that. If you can find some time to add a note to the documentation that would be greatly appreciated. https://github.com/IfcOpenShell/IfcOpenShell/blob/v0.7.0/src/ifcopenshell-python/docs/ifcopenshell-python/geometry_processing.rst#individual-processing

[sennhvi]

Yes, I have added a note in PR #4154 :)