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Add IfcDerivedUnit support to ifcopenshell.util.unit (scale, symbol, dimension identification)

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Richard Brice
2026-08-10 08:14:15 -07:00
parent 2bfcf8ab83
commit 20a6c73fbf
2 changed files with 201 additions and 32 deletions
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src/ifcopenshell-python/test/util/test_unit.py
+70
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@@ -204,6 +204,17 @@ class TestCalculateUnitScale(test.bootstrap.IFC4):
ifcopenshell.api.unit.assign_unit(self.file, units=[angle])
assert subject.calculate_unit_scale(self.file, "PLANEANGLEUNIT") == pi / 180 * 0.001
def test_derived_units_are_considered(self):
ifcopenshell.api.root.create_entity(self.file, ifc_class="IfcProject")
force = ifcopenshell.api.unit.add_si_unit(self.file, unit_type="FORCEUNIT")
area = ifcopenshell.api.unit.add_si_unit(self.file, unit_type="AREAUNIT", prefix="MILLI")
modulus = ifcopenshell.api.unit.add_derived_unit(self.file, "MODULUSOFELASTICITYUNIT", None, {force: 1, area: -1})
ifcopenshell.api.unit.assign_unit(self.file, units=[modulus])
# AREAUNIT is a pure power of length, so its MILLI prefix is raised to
# the length exponent (2) per #9278: (1e-3)**2 = 1e-6, inverted by the
# derived unit's -1 exponent to give 1e6.
assert subject.calculate_unit_scale(self.file, "MODULUSOFELASTICITYUNIT") == pytest.approx(1_000_000.0)
def test_prefix_is_raised_to_the_length_exponent_for_area_and_volume(self):
# A prefixed square/cubic metre is (prefix-metre) squared/cubed:
# DECI SQUARE_METRE = dm2 = 1e-2 m2, DECI CUBIC_METRE = dm3 (litre) = 1e-3 m3.
@@ -258,6 +269,65 @@ class TestCalculateUnitScaleOnLinkedFile(test.bootstrap.IFC4):
tmp_file.unlink(missing_ok=True)
class TestGetNamedUnitScale(test.bootstrap.IFC4):
def test_prefix_is_raised_to_the_length_exponent_for_area_and_volume(self):
area = ifcopenshell.api.unit.add_si_unit(self.file, unit_type="AREAUNIT", prefix="DECI")
assert subject.get_named_unit_scale(area) == pytest.approx(0.1**2)
def test_prefix_stays_linear_for_units_that_are_not_a_pure_power_of_length(self):
pressure = ifcopenshell.api.unit.add_si_unit(self.file, unit_type="PRESSUREUNIT", prefix="KILO")
assert subject.get_named_unit_scale(pressure) == pytest.approx(1000)
class TestGetDerivedUnitScale(test.bootstrap.IFC4):
def test_composes_scale_from_elements(self):
ifcopenshell.api.root.create_entity(self.file, ifc_class="IfcProject")
mass = ifcopenshell.api.unit.add_si_unit(self.file, unit_type="MASSUNIT", prefix="KILO")
volume = ifcopenshell.api.unit.add_si_unit(self.file, unit_type="VOLUMEUNIT")
density = ifcopenshell.api.unit.add_derived_unit(self.file, "MASSDENSITYUNIT", None, {mass: 1, volume: -1})
assert subject.get_derived_unit_scale(density) == 1000.0
def test_unnamed_derived_unit_still_composes(self):
# A made-up "force per unit time" derived unit with no IfcDerivedUnitEnum match.
ifcopenshell.api.root.create_entity(self.file, ifc_class="IfcProject")
force = ifcopenshell.api.unit.add_si_unit(self.file, unit_type="FORCEUNIT")
time = ifcopenshell.api.unit.add_si_unit(self.file, unit_type="TIMEUNIT", prefix="MILLI")
weird = ifcopenshell.api.unit.add_derived_unit(self.file, "USERDEFINED", "force per time", {force: 1, time: -1})
assert subject.get_derived_unit_scale(weird) == pytest.approx(1 / 0.001)
class TestGetUnitSymbol(test.bootstrap.IFC4):
def test_derived_unit_composes_a_symbol(self):
ifcopenshell.api.root.create_entity(self.file, ifc_class="IfcProject")
force = ifcopenshell.api.unit.add_si_unit(self.file, unit_type="FORCEUNIT")
area = ifcopenshell.api.unit.add_si_unit(self.file, unit_type="AREAUNIT")
modulus = ifcopenshell.api.unit.add_derived_unit(self.file, "MODULUSOFELASTICITYUNIT", None, {force: 1, area: -1})
assert subject.get_unit_symbol(modulus) == "N/m2"
def test_unnamed_derived_unit_still_composes_a_symbol_without_crashing(self):
ifcopenshell.api.root.create_entity(self.file, ifc_class="IfcProject")
force = ifcopenshell.api.unit.add_si_unit(self.file, unit_type="FORCEUNIT")
time = ifcopenshell.api.unit.add_si_unit(self.file, unit_type="TIMEUNIT")
weird = ifcopenshell.api.unit.add_derived_unit(self.file, "USERDEFINED", "force per time", {force: 1, time: -1})
assert subject.get_unit_symbol(weird) == "N/s"
class TestIdentifyUnitDimensions(test.bootstrap.IFC4):
def test_matches_a_named_unit_type_by_dimension(self):
ifcopenshell.api.root.create_entity(self.file, ifc_class="IfcProject")
force = ifcopenshell.api.unit.add_si_unit(self.file, unit_type="FORCEUNIT")
area = ifcopenshell.api.unit.add_si_unit(self.file, unit_type="AREAUNIT")
modulus = ifcopenshell.api.unit.add_derived_unit(self.file, "MODULUSOFELASTICITYUNIT", None, {force: 1, area: -1})
assert subject.identify_unit_dimensions(modulus) == "PRESSUREUNIT"
def test_returns_none_for_no_match(self):
ifcopenshell.api.root.create_entity(self.file, ifc_class="IfcProject")
force = ifcopenshell.api.unit.add_si_unit(self.file, unit_type="FORCEUNIT")
time = ifcopenshell.api.unit.add_si_unit(self.file, unit_type="TIMEUNIT")
weird = ifcopenshell.api.unit.add_derived_unit(self.file, "USERDEFINED", "force per time", {force: 1, time: -1})
assert subject.identify_unit_dimensions(weird) is None
class TestFormatLength(test.bootstrap.IFC4):
def test_run(self):
assert subject.format_length(1, 1, decimal_places=0, unit_system="metric") == "1"