Guess units if none are present and convert back if needed

src/ifcgeom/IfcGeomObjects.cpp

@@ -47,9 +47,12 @@
 
 // Welds vertices that belong to different faces
 bool weld_vertices = true;
+bool convert_back_units = false;
 
 int IfcGeomObjects::IfcMesh::addvert(const gp_XYZ& p) {
-	const float X = (float)p.X();const float Y = (float)p.Y();const float Z = (float)p.Z();
+	const float X = convert_back_units ? (float)p.X() / Ifc::LengthUnit : (float)p.X();
+	const float Y = convert_back_units ? (float)p.Y() / Ifc::LengthUnit : (float)p.Y();
+	const float Z = convert_back_units ? (float)p.Z() / Ifc::LengthUnit : (float)p.Z();
 	int i = (int) verts.size() / 3;
 	if ( weld_vertices ) {
 		const VertKey key = VertKey(X,std::pair<float,float>(Y,Z));
@@ -277,7 +280,7 @@ IfcGeomObjects::IfcGeomObject* _get() {
 		int parent_id = -1;
 		const std::string name = ifc_product->hasName() ? ifc_product->Name() : "";
 		const std::string guid = ifc_product->GlobalId();
-
+		
 		gp_Trsf trsf;
 		try {
 			IfcGeom::convert(ifc_product->ObjectPlacement(),trsf);
@@ -469,6 +472,9 @@ void IfcGeomObjects::Settings(int setting, bool value) {
 	case WELD_VERTICES:
 		weld_vertices = value;
 		break;
+	case CONVERT_BACK_UNITS:
+		convert_back_units = value;
+		break;
 	}
 }
 int IfcGeomObjects::Progress() {

src/ifcgeom/IfcGeomObjects.h

@@ -70,6 +70,7 @@ namespace IfcGeomObjects {
 
 	const int WELD_VERTICES = 1;
 	const int USE_WORLD_COORDS = 2;
+	const int CONVERT_BACK_UNITS = 3;
 
 	typedef std::vector<int>::const_iterator IntIt;
 	typedef std::vector<float>::const_iterator FltIt;

src/ifcjni/IfcJni.cpp

@@ -71,5 +71,6 @@ JNIEXPORT bool JNICALL Java_org_ifcopenshell_IfcOpenShellModel_setIfcData (JNIEn
   if ( ! data || ! length ) return false;
   IfcGeomObjects::Settings(IfcGeomObjects::USE_WORLD_COORDS,true);
   IfcGeomObjects::Settings(IfcGeomObjects::WELD_VERTICES,false);
+  IfcGeomObjects::Settings(IfcGeomObjects::CONVERT_BACK_UNITS,true);
   return has_more = IfcGeomObjects::Init(data,length);
 }

src/ifcparse/IfcParse.cpp

@@ -628,8 +628,22 @@ bool Ifc::Init(IfcParse::File* f) {
 	if ( unit_assignments->Size() ) {
 		Ifc2x3::IfcUnitAssignment::ptr unit_assignment = *unit_assignments->begin();
 		units = unit_assignment->Units();
-    }
-	if ( ! units ) return true;
+	}
+	if ( ! units ) {
+		// No units eh... Since tolerances and deflection are specified internally in meters
+		// we will try to find another indication of the model size.
+		// Note that for IfcTrimmedCurves to render correctly, IfcParameterValues better be 
+		// in radians or IfcOpenShell would not know what to make of them.
+		Ifc2x3::IfcExtrudedAreaSolid::list extrusions = EntitiesByType<Ifc2x3::IfcExtrudedAreaSolid>();
+		if ( ! extrusions->Size() ) return true;
+		float max_height = -1.0f;
+		for ( Ifc2x3::IfcExtrudedAreaSolid::it it = extrusions->begin(); it != extrusions->end(); ++ it ) {
+			const float depth = (*it)->Depth();
+			if ( depth > max_height ) max_height = depth;
+		}
+		if ( max_height > 100.0f ) Ifc::LengthUnit = 0.001f;
+		return true;
+	}
 	try {
 	for ( IfcUtil::IfcAbstractSelect::it it = units->begin(); it != units->end(); ++ it ) {
 		const IfcUtil::IfcAbstractSelect::ptr base = *it;