Module Contents#

class ifcopenshell.api.void.add_opening.Usecase(file, opening=None, element=None)#

Create an opening in an element

It is often necessary to cut out openings in elements like walls and slabs to make space to insert doors, windows, and other services that go through these penetrations.

Whereas it is possible to simply draw the wall as a rectangle with a hole in it for the opening, often these openings have specific meanings. For example, an opening might be filled with a window, and so when the window moves, the opening should move with it. Alternatively, the opening itself might have fire or acoustic requirements, such that any service or equipment passing through that space must also comply with those requirements. For these types of semantic openings, you should have a distinct opening element which voids your regular element. For example, your wall will still be a rectangular prism with no hole in it, and a separate opening element will have a box representing the extents of the opening for a window. The opening element will automatically perform a geometric boolean operation to cut out the wall’s geometry.

Whenever you have an opening in you project, you should determine whether or not the opening is semantic (i.e. should be represented by a distinct opening object) or non-semantic (i.e. should simply be booleaned or be part of the shape of the object).


The new IfcRelVoidsElement relationship

Return type



# A bit of preparation, let's create some geometric contexts since
# we want to create some geometry for our wall and opening.
model3d = ifcopenshell.api.run("context.add_context", model, context_type="Model")
body = ifcopenshell.api.run("context.add_context", model,
    context_type="Model", context_identifier="Body", target_view="MODEL_VIEW", parent=model3d)

# Create a wall
wall = ifcopenshell.api.run("root.create_entity", model, ifc_class="IfcWall")

# Let's use the "3D Body" representation we created earlier to add a
# new wall-like body geometry, 5 meters long, 3 meters high, and
# 200mm thick
representation = ifcopenshell.api.run("geometry.add_wall_representation", model,
    context=body, length=5, height=3, thickness=0.2)
ifcopenshell.api.run("geometry.assign_representation", model,
    product=wall, representation=representation)

# Place our wall at the origin
ifcopenshell.api.run("geometry.edit_object_placement", model, product=wall)

# Create an opening, such as for a service penetration with fire and
# acoustic requirements.
opening = ifcopenshell.api.run("root.create_entity", model, ifc_class="IfcOpeningElement")

# Let's create an opening representation of a 950mm x 2100mm door.
# Notice how the thickness is greater than the wall thickness, this
# helps resolve floating point resolution errors in 3D.
representation = ifcopenshell.api.run("geometry.add_wall_representation", model,
    context=body, length=.95, height=2.1, thickness=0.4)
ifcopenshell.api.run("geometry.assign_representation", model,
    product=opening, representation=representation)

# Let's shift our door 1 meter along the wall and 100mm along the
# wall, to create a nice overlap for the opening boolean.
matrix = np.identity(4)
matrix[:,3] = [1, -.1, 0, 0]
ifcopenshell.api.run("geometry.edit_object_placement", model, product=opening, matrix=matrix)

# The opening will now void the wall.
ifcopenshell.api.run("void.add_opening", model, opening=opening, element=wall)