Implement ability to add SI units

src/blenderbim/blenderbim/bim/module/unit/__init__.py

@@ -8,6 +8,7 @@ classes = (
     operator.DisableUnitEditingUI,
     operator.RemoveUnit,
     operator.AddMonetaryUnit,
+    operator.AddSIUnit,
     operator.EnableEditingUnit,
     operator.DisableEditingUnit,
     operator.EditUnit,

src/blenderbim/blenderbim/bim/module/unit/operator.py

@@ -1,5 +1,6 @@
 import bpy
 import ifcopenshell.api
+import ifcopenshell.util.unit
 import blenderbim.bim.helper
 from blenderbim.bim.ifc import IfcStore
 from ifcopenshell.api.unit.data import Data
@@ -156,8 +157,29 @@ class AddMonetaryUnit(bpy.types.Operator):
     def _execute(self, context):
         props = context.scene.BIMUnitProperties
         self.file = IfcStore.get_file()
-        unit = ifcopenshell.api.run("unit.add_monetary_unit", self.file)
-        ifcopenshell.api.run("unit.assign_unit", self.file, units=[unit])
+        ifcopenshell.api.run("unit.add_monetary_unit", self.file)
+        Data.load(self.file)
+        bpy.ops.bim.load_units()
+        return {"FINISHED"}
+
+
+class AddSIUnit(bpy.types.Operator):
+    bl_idname = "bim.add_si_unit"
+    bl_label = "Add SI Unit"
+    bl_options = {"REGISTER", "UNDO"}
+
+    def execute(self, context):
+        return IfcStore.execute_ifc_operator(self, context)
+
+    def _execute(self, context):
+        props = context.scene.BIMUnitProperties
+        self.file = IfcStore.get_file()
+        unit = ifcopenshell.api.run(
+            "unit.add_si_unit",
+            self.file,
+            unit_type=props.named_unit_types,
+            name=ifcopenshell.util.unit.si_type_names[props.named_unit_types],
+        )
         Data.load(self.file)
         bpy.ops.bim.load_units()
         return {"FINISHED"}

src/blenderbim/blenderbim/bim/module/unit/prop.py

@@ -1,6 +1,7 @@
 import bpy
 import ifcopenshell
 import ifcopenshell.util.schema
+import ifcopenshell.util.attribute
 from blenderbim.bim.ifc import IfcStore
 from blenderbim.bim.prop import StrProperty, Attribute
 from bpy.types import PropertyGroup
@@ -17,11 +18,14 @@ from bpy.props import (
 
 
 unitclasses_enum = []
+namedunittypes_enum = []
 
 
 def purge():
     global unitclasses_enum
+    global namedunittypes_enum
     unitclasses_enum = []
+    namedunittypes_enum = []
 
 
 def getUnitClasses(self, context):
@@ -33,6 +37,16 @@ def getUnitClasses(self, context):
     return unitclasses_enum
 
 
+def getNamedUnitTypes(self, context):
+    global namedunittypes_enum
+    if not len(namedunittypes_enum) and IfcStore.get_file():
+        values = ifcopenshell.util.attribute.get_enum_items(
+            IfcStore.get_schema().declaration_by_name("IfcNamedUnit").all_attributes()[1]
+        )
+        namedunittypes_enum.extend([(c, c, "") for c in sorted(values)])
+    return namedunittypes_enum
+
+
 class Unit(PropertyGroup):
     name: StringProperty(name="Name")
     unit_type: StringProperty(name="Unit Type")
@@ -47,4 +61,5 @@ class BIMUnitProperties(PropertyGroup):
     active_unit_index: IntProperty(name="Active Unit Index")
     active_unit_id: IntProperty(name="Active Unit Id")
     unit_classes: EnumProperty(items=getUnitClasses, name="Unit Classes")
+    named_unit_types: EnumProperty(items=getNamedUnitTypes, name="Named Unit Types")
     unit_attributes: CollectionProperty(name="Unit Attributes", type=Attribute)

src/blenderbim/blenderbim/bim/module/unit/ui.py

@@ -40,8 +40,11 @@ class BIM_PT_units(Panel):
             row.operator("bim.add_monetary_unit", text="", icon="ADD")
         elif self.props.unit_classes == "IfcDerivedUnit":
             pass  # TODO
+        elif self.props.unit_classes == "IfcSIUnit":
+            row.prop(self.props, "named_unit_types", text="")
+            row.operator("bim.add_si_unit", text="", icon="ADD")
         else:
-            pass  # TODO
+            row.prop(self.props, "named_unit_types", text="")
 
         self.layout.template_list(
             "BIM_UL_units",

src/ifcopenshell-python/ifcopenshell/api/unit/add_si_unit.py

@@ -0,0 +1,9 @@
+class Usecase:
+    def __init__(self, file, **settings):
+        self.file = file
+        self.settings = {"unit_type": "LENGTHUNIT", "name": "METRE"}
+        for key, value in settings.items():
+            self.settings[key] = value
+
+    def execute(self):
+        return self.file.create_entity("IfcSIUnit", UnitType=self.settings["unit_type"], Name=self.settings["name"])

src/ifcopenshell-python/ifcopenshell/util/unit.py

@@ -25,7 +25,7 @@ unit_names = [
     "CANDELA",
     "COULOMB",
     "CUBIC_METRE",
-    "DEGREE CELSIUS",
+    "DEGREE_CELSIUS",
     "FARAD",
     "GRAM",
     "GRAY",
@@ -43,7 +43,7 @@ unit_names = [
     "SECOND",
     "SIEMENS",
     "SIEVERT",
-    "SQUARE METRE",
+    "SQUARE_METRE",
     "METRE",
     "STERADIAN",
     "TESLA",
@@ -52,7 +52,6 @@ unit_names = [
     "WEBER",
 ]
 
-
 si_dimensions = {
     "METRE": (1, 0, 0, 0, 0, 0, 0),
     "SQUARE_METRE": (2, 0, 0, 0, 0, 0, 0),
@@ -87,6 +86,39 @@ si_dimensions = {
     "OTHERWISE": (0, 0, 0, 0, 0, 0, 0),
 }
 
+# See https://github.com/buildingSMART/IFC4.3.x-development/issues/72
+si_type_names = {
+    "ABSORBEDDOSEUNIT": "GRAY",
+    "AMOUNTOFSUBSTANCEUNIT": "MOLE",
+    "AREAUNIT": "SQUARE_METRE",
+    "DOSEEQUIVALENTUNIT": "SIEVERT",
+    "ELECTRICCAPACITANCEUNIT": "FARAD",
+    "ELECTRICCHARGEUNIT": "COULOMB",
+    "ELECTRICCONDUCTANCEUNIT": "SIEMENS",
+    "ELECTRICCURRENTUNIT": "AMPERE",
+    "ELECTRICRESISTANCEUNIT": "OHM",
+    "ELECTRICVOLTAGEUNIT": "VOLT",
+    "ENERGYUNIT": "JOULE",
+    "FORCEUNIT": "NEWTON",
+    "FREQUENCYUNIT": "HERTZ",
+    "ILLUMINANCEUNIT": "LUX",
+    "INDUCTANCEUNIT": "HENRY",
+    "LENGTHUNIT": "METRE",
+    "LUMINOUSFLUXUNIT": "LUMEN",
+    "LUMINOUSINTENSITYUNIT": "CANDELA",
+    "MAGNETICFLUXDENSITYUNIT": "TESLA",
+    "MAGNETICFLUXUNIT": "WEBER",
+    "MASSUNIT": "GRAM",
+    "PLANEANGLEUNIT": "RADIAN",
+    "POWERUNIT": "WATT",
+    "PRESSUREUNIT": "PASCAL",
+    "RADIOACTIVITYUNIT": "BECQUEREL",
+    "SOLIDANGLEUNIT": "STERADIAN",
+    "THERMODYNAMICTEMPERATUREUNIT": "KELVIN", # Or, DEGREE_CELSIUS, but this is a quirk of IFC
+    "TIMEUNIT": "SECOND",
+    "VOLUMEUNIT": "CUBIC_METRE",
+}
+
 si_conversions = {
     "inch": 0.0254,
     "foot": 0.3048,
@@ -169,7 +201,7 @@ def get_prefix_multiplier(text):
 def get_unit_name(text):
     text = text.upper().replace("METER", "METRE")
     for name in unit_names:
-        if name in text:
+        if name.replace("_", " ") in text:
             return name
 
 
@@ -263,19 +295,17 @@ def convert(value, from_prefix, from_unit, to_prefix, to_unit):
     return value
 
 
-"""Returns a unit scale factor to convert to and from IFC project length units and SI meters
-
-Example::
-
-    ifc_project_length * unit_scale = si_meters
-    si_meters / unit_scale = ifc_project_length
-
-:returns: The scale factor
-:rtype: float
-"""
-
-
 def calculate_unit_scale(file):
+    """Returns a unit scale factor to convert to and from IFC project length units and SI meters
+
+    Example::
+
+        ifc_project_length * unit_scale = si_meters
+        si_meters / unit_scale = ifc_project_length
+
+    :returns: The scale factor
+    :rtype: float
+    """
     units = file.by_type("IfcUnitAssignment")[0]
     unit_scale = 1
     for unit in units.Units: