assimp/code/IFCLoader.cpp

/*
Open Asset Import Library (assimp)
----------------------------------------------------------------------

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All rights reserved.

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  following disclaimer.

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*/

/** @file  IFCLoad.cpp
 *  @brief Implementation of the Industry Foundation Classes loader.
 */


#ifndef ASSIMP_BUILD_NO_IFC_IMPORTER

#include <iterator>
#include <limits>
#include <boost/tuple/tuple.hpp>

#ifndef ASSIMP_BUILD_NO_COMPRESSED_IFC
#	include "../contrib/unzip/unzip.h"
#endif

#include "IFCLoader.h"
#include "STEPFileReader.h"

#include "IFCUtil.h"

#include "StreamReader.h"
#include "MemoryIOWrapper.h"
#include "../include/assimp/scene.h"
#include "../include/assimp/Importer.hpp"


namespace Assimp {
	template<> const std::string LogFunctions<IFCImporter>::log_prefix = "IFC: ";
}

using namespace Assimp;
using namespace Assimp::Formatter;
using namespace Assimp::IFC;

/* DO NOT REMOVE this comment block. The genentitylist.sh script
 * just looks for names adhering to the IfcSomething naming scheme
 * and includes all matches in the whitelist for code-generation. Thus,
 * all entity classes that are only indirectly referenced need to be
 * mentioned explicitly.

  IfcRepresentationMap
  IfcProductRepresentation
  IfcUnitAssignment
  IfcClosedShell
  IfcDoor

 */

namespace {


// forward declarations
void SetUnits(ConversionData& conv);
void SetCoordinateSpace(ConversionData& conv);
void ProcessSpatialStructures(ConversionData& conv);
void MakeTreeRelative(ConversionData& conv);
void ConvertUnit(const EXPRESS::DataType& dt,ConversionData& conv);

} // anon

static const aiImporterDesc desc = {
	"Industry Foundation Classes (IFC) Importer",
	"",
	"",
	"",
	aiImporterFlags_SupportBinaryFlavour,
	0,
	0,
	0,
	0,
	"ifc ifczip" 
};


// ------------------------------------------------------------------------------------------------
// Constructor to be privately used by Importer
IFCImporter::IFCImporter()
{}

// ------------------------------------------------------------------------------------------------
// Destructor, private as well 
IFCImporter::~IFCImporter()
{
}

// ------------------------------------------------------------------------------------------------
// Returns whether the class can handle the format of the given file. 
bool IFCImporter::CanRead( const std::string& pFile, IOSystem* pIOHandler, bool checkSig) const
{
	const std::string& extension = GetExtension(pFile);
	if (extension == "ifc" || extension == "ifczip") {
		return true;
	}

	else if ((!extension.length() || checkSig) && pIOHandler)	{
		// note: this is the common identification for STEP-encoded files, so
		// it is only unambiguous as long as we don't support any further
		// file formats with STEP as their encoding.
		const char* tokens[] = {"ISO-10303-21"};
		return SearchFileHeaderForToken(pIOHandler,pFile,tokens,1);
	}
	return false;
}

// ------------------------------------------------------------------------------------------------
// List all extensions handled by this loader
const aiImporterDesc* IFCImporter::GetInfo () const
{
	return &desc;
}


// ------------------------------------------------------------------------------------------------
// Setup configuration properties for the loader
void IFCImporter::SetupProperties(const Importer* pImp)
{
	settings.skipSpaceRepresentations = pImp->GetPropertyBool(AI_CONFIG_IMPORT_IFC_SKIP_SPACE_REPRESENTATIONS,true);
	settings.skipCurveRepresentations = pImp->GetPropertyBool(AI_CONFIG_IMPORT_IFC_SKIP_CURVE_REPRESENTATIONS,true);
	settings.useCustomTriangulation = pImp->GetPropertyBool(AI_CONFIG_IMPORT_IFC_CUSTOM_TRIANGULATION,true);

	settings.conicSamplingAngle = 10.f;
	settings.skipAnnotations = true;
}


// ------------------------------------------------------------------------------------------------
// Imports the given file into the given scene structure. 
void IFCImporter::InternReadFile( const std::string& pFile, 
	aiScene* pScene, IOSystem* pIOHandler)
{
	boost::shared_ptr<IOStream> stream(pIOHandler->Open(pFile));
	if (!stream) {
		ThrowException("Could not open file for reading");
	}


	// if this is a ifczip file, decompress its contents first
	if(GetExtension(pFile) == "ifczip") {
#ifndef ASSIMP_BUILD_NO_COMPRESSED_IFC
		unzFile zip = unzOpen( pFile.c_str() );
		if(zip == NULL) {
			ThrowException("Could not open ifczip file for reading, unzip failed");
		}

		// chop 'zip' postfix
		std::string fileName = pFile.substr(0,pFile.length() - 3);

		std::string::size_type s = pFile.find_last_of('\\');
		if(s == std::string::npos) {
			s = pFile.find_last_of('/');
		}
		if(s != std::string::npos) {
			fileName = fileName.substr(s+1);
		}

		// search file (same name as the IFCZIP except for the file extension) and place file pointer there
		if(UNZ_OK == unzGoToFirstFile(zip)) {
			do {
				// get file size, etc.
				unz_file_info fileInfo;
				char filename[256];
				unzGetCurrentFileInfo( zip , &fileInfo, filename, sizeof(filename), 0, 0, 0, 0 );
				if (GetExtension(filename) != "ifc") {
					continue;
				}
				uint8_t* buff = new uint8_t[fileInfo.uncompressed_size];
				LogInfo("Decompressing IFCZIP file");
				unzOpenCurrentFile( zip  );
				const int ret = unzReadCurrentFile( zip, buff, fileInfo.uncompressed_size);
				size_t filesize = fileInfo.uncompressed_size;
				if ( ret < 0 || size_t(ret) != filesize )
				{
					delete[] buff;
					ThrowException("Failed to decompress IFC ZIP file");
				}
				unzCloseCurrentFile( zip );
				stream.reset(new MemoryIOStream(buff,fileInfo.uncompressed_size,true));
				break;

				if (unzGoToNextFile(zip) == UNZ_END_OF_LIST_OF_FILE) {
					ThrowException("Found no IFC file member in IFCZIP file (1)");
				}

			} while(true);
		}
		else {
			ThrowException("Found no IFC file member in IFCZIP file (2)");
		}

		unzClose(zip);
#else
		ThrowException("Could not open ifczip file for reading, assimp was built without ifczip support");
#endif
	}

	boost::scoped_ptr<STEP::DB> db(STEP::ReadFileHeader(stream));
	const STEP::HeaderInfo& head = static_cast<const STEP::DB&>(*db).GetHeader();

	if(!head.fileSchema.size() || head.fileSchema.substr(0,3) != "IFC") {
		ThrowException("Unrecognized file schema: " + head.fileSchema);
	}

	if (!DefaultLogger::isNullLogger()) {
		LogDebug("File schema is \'" + head.fileSchema + '\'');
		if (head.timestamp.length()) {
			LogDebug("Timestamp \'" + head.timestamp + '\'');
		}
		if (head.app.length()) {
			LogDebug("Application/Exporter identline is \'" + head.app  + '\'');
		}
	}

	// obtain a copy of the machine-generated IFC scheme
	EXPRESS::ConversionSchema schema;
	GetSchema(schema);

	// tell the reader which entity types to track with special care
	static const char* const types_to_track[] = {
		"ifcsite", "ifcbuilding", "ifcproject"
	};

	// tell the reader for which types we need to simulate STEPs reverse indices
	static const char* const inverse_indices_to_track[] = {
		"ifcrelcontainedinspatialstructure", "ifcrelaggregates", "ifcrelvoidselement", "ifcreldefinesbyproperties", "ifcpropertyset", "ifcstyleditem"
	};

	// feed the IFC schema into the reader and pre-parse all lines
	STEP::ReadFile(*db, schema, types_to_track, inverse_indices_to_track);
	const STEP::LazyObject* proj =  db->GetObject("ifcproject");
	if (!proj) {
		ThrowException("missing IfcProject entity");
	}

	ConversionData conv(*db,proj->To<IfcProject>(),pScene,settings);
	SetUnits(conv);
	SetCoordinateSpace(conv);
	ProcessSpatialStructures(conv);
	MakeTreeRelative(conv);

	// NOTE - this is a stress test for the importer, but it works only
	// in a build with no entities disabled. See 
	//     scripts/IFCImporter/CPPGenerator.py
	// for more information.
	#ifdef ASSIMP_IFC_TEST
		db->EvaluateAll();
	#endif

	// do final data copying
	if (conv.meshes.size()) {
		pScene->mNumMeshes = static_cast<unsigned int>(conv.meshes.size());
		pScene->mMeshes = new aiMesh*[pScene->mNumMeshes]();
		std::copy(conv.meshes.begin(),conv.meshes.end(),pScene->mMeshes);

		// needed to keep the d'tor from burning us
		conv.meshes.clear();
	}

	if (conv.materials.size()) {
		pScene->mNumMaterials = static_cast<unsigned int>(conv.materials.size());
		pScene->mMaterials = new aiMaterial*[pScene->mNumMaterials]();
		std::copy(conv.materials.begin(),conv.materials.end(),pScene->mMaterials);

		// needed to keep the d'tor from burning us
		conv.materials.clear();
	}

	// apply world coordinate system (which includes the scaling to convert to meters and a -90 degrees rotation around x)
	aiMatrix4x4 scale, rot;
	aiMatrix4x4::Scaling(static_cast<aiVector3D>(IfcVector3(conv.len_scale)),scale);
	aiMatrix4x4::RotationX(-AI_MATH_HALF_PI_F,rot);

	pScene->mRootNode->mTransformation = rot * scale * conv.wcs * pScene->mRootNode->mTransformation;

	// this must be last because objects are evaluated lazily as we process them
	if ( !DefaultLogger::isNullLogger() ){
		LogDebug((Formatter::format(),"STEP: evaluated ",db->GetEvaluatedObjectCount()," object records"));
	}
}

namespace {


// ------------------------------------------------------------------------------------------------
void ConvertUnit(const IfcNamedUnit& unit,ConversionData& conv)
{
	if(const IfcSIUnit* const si = unit.ToPtr<IfcSIUnit>()) {

		if(si->UnitType == "LENGTHUNIT") { 
			conv.len_scale = si->Prefix ? ConvertSIPrefix(si->Prefix) : 1.f;
			IFCImporter::LogDebug("got units used for lengths");
		}
		if(si->UnitType == "PLANEANGLEUNIT") { 
			if (si->Name != "RADIAN") {
				IFCImporter::LogWarn("expected base unit for angles to be radian");
			}
		}
	}
	else if(const IfcConversionBasedUnit* const convu = unit.ToPtr<IfcConversionBasedUnit>()) {

		if(convu->UnitType == "PLANEANGLEUNIT") { 
			try {
				conv.angle_scale = convu->ConversionFactor->ValueComponent->To<EXPRESS::REAL>();
				ConvertUnit(*convu->ConversionFactor->UnitComponent,conv);
				IFCImporter::LogDebug("got units used for angles");
			}
			catch(std::bad_cast&) {
				IFCImporter::LogError("skipping unknown IfcConversionBasedUnit.ValueComponent entry - expected REAL");
			}
		}
	}
}

// ------------------------------------------------------------------------------------------------
void ConvertUnit(const EXPRESS::DataType& dt,ConversionData& conv)
{
	try {
		const EXPRESS::ENTITY& e = dt.To<ENTITY>();

		const IfcNamedUnit& unit = e.ResolveSelect<IfcNamedUnit>(conv.db);
		if(unit.UnitType != "LENGTHUNIT" && unit.UnitType != "PLANEANGLEUNIT") {
			return;
		}

		ConvertUnit(unit,conv);
	}
	catch(std::bad_cast&) {
		// not entity, somehow
		IFCImporter::LogError("skipping unknown IfcUnit entry - expected entity");
	}
}

// ------------------------------------------------------------------------------------------------
void SetUnits(ConversionData& conv)
{
	// see if we can determine the coordinate space used to express. 
	for(size_t i = 0; i <  conv.proj.UnitsInContext->Units.size(); ++i ) {
		ConvertUnit(*conv.proj.UnitsInContext->Units[i],conv);
	}
}


// ------------------------------------------------------------------------------------------------
void SetCoordinateSpace(ConversionData& conv)
{
	const IfcRepresentationContext* fav = NULL;
	BOOST_FOREACH(const IfcRepresentationContext& v, conv.proj.RepresentationContexts) {
		fav = &v;
		// Model should be the most suitable type of context, hence ignore the others 
		if (v.ContextType && v.ContextType.Get() == "Model") { 
			break;
		}
	}
	if (fav) {
		if(const IfcGeometricRepresentationContext* const geo = fav->ToPtr<IfcGeometricRepresentationContext>()) {
			ConvertAxisPlacement(conv.wcs, *geo->WorldCoordinateSystem, conv);
			IFCImporter::LogDebug("got world coordinate system");
		}
	}
}


// ------------------------------------------------------------------------------------------------
void ResolveObjectPlacement(aiMatrix4x4& m, const IfcObjectPlacement& place, ConversionData& conv)
{
	if (const IfcLocalPlacement* const local = place.ToPtr<IfcLocalPlacement>()){
		IfcMatrix4 tmp;
		ConvertAxisPlacement(tmp, *local->RelativePlacement, conv);

		m = static_cast<aiMatrix4x4>(tmp);

		if (local->PlacementRelTo) {
			aiMatrix4x4 tmp;
			ResolveObjectPlacement(tmp,local->PlacementRelTo.Get(),conv);
			m = tmp * m;
		}
	}
	else {
		IFCImporter::LogWarn("skipping unknown IfcObjectPlacement entity, type is " + place.GetClassName());
	}
}

// ------------------------------------------------------------------------------------------------
bool ProcessMappedItem(const IfcMappedItem& mapped, aiNode* nd_src, std::vector< aiNode* >& subnodes_src, unsigned int matid, ConversionData& conv)
{
	// insert a custom node here, the cartesian transform operator is simply a conventional transformation matrix
	std::auto_ptr<aiNode> nd(new aiNode());
	nd->mName.Set("IfcMappedItem");
		
	// handle the Cartesian operator
	IfcMatrix4 m;
	ConvertTransformOperator(m, *mapped.MappingTarget);

	IfcMatrix4 msrc;
	ConvertAxisPlacement(msrc,*mapped.MappingSource->MappingOrigin,conv);

	msrc = m*msrc;

	std::vector<unsigned int> meshes;
	const size_t old_openings = conv.collect_openings ? conv.collect_openings->size() : 0;
	if (conv.apply_openings) {
		IfcMatrix4 minv = msrc;
		minv.Inverse();
		BOOST_FOREACH(TempOpening& open,*conv.apply_openings){
			open.Transform(minv);
		}
	}

	unsigned int localmatid = ProcessMaterials(mapped.GetID(),matid,conv,false);
	const IfcRepresentation& repr = mapped.MappingSource->MappedRepresentation;

	bool got = false;
	BOOST_FOREACH(const IfcRepresentationItem& item, repr.Items) {
		if(!ProcessRepresentationItem(item,localmatid,meshes,conv)) {
			IFCImporter::LogWarn("skipping mapped entity of type " + item.GetClassName() + ", no representations could be generated");
		}
		else got = true;
	}

	if (!got) {
		return false;
	}

	AssignAddedMeshes(meshes,nd.get(),conv);
	if (conv.collect_openings) {

		// if this pass serves us only to collect opening geometry,
		// make sure we transform the TempMesh's which we need to
		// preserve as well.
		if(const size_t diff = conv.collect_openings->size() - old_openings) {
			for(size_t i = 0; i < diff; ++i) {
				(*conv.collect_openings)[old_openings+i].Transform(msrc);
			}
		}
	}

	nd->mTransformation =  nd_src->mTransformation * static_cast<aiMatrix4x4>( msrc );
	subnodes_src.push_back(nd.release());

	return true;
}

// ------------------------------------------------------------------------------------------------
struct RateRepresentationPredicate {

	int Rate(const IfcRepresentation* r) const {
		// the smaller, the better

		if (! r->RepresentationIdentifier) {
			// neutral choice if no extra information is specified
			return 0;
		}

		
		const std::string& name = r->RepresentationIdentifier.Get();
		if (name == "MappedRepresentation") {
			if (!r->Items.empty()) {
				// take the first item and base our choice on it
				const IfcMappedItem* const m = r->Items.front()->ToPtr<IfcMappedItem>();
				if (m) {
					return Rate(m->MappingSource->MappedRepresentation);
				}
			}
			return 100;
		}

		return Rate(name);
	}

	int Rate(const std::string& r) const {


		if (r == "SolidModel") {
			return -3;
		}
		
		// give strong preference to extruded geometry.
		if (r == "SweptSolid") {
			return -10;
		}
		
		if (r == "Clipping") {
			return -5;
		}

		// 'Brep' is difficult to get right due to possible voids in the
		// polygon boundaries, so take it only if we are forced to (i.e.
		// if the only alternative is (non-clipping) boolean operations, 
		// which are not supported at all).
		if (r == "Brep") {
			return -2;
		}
		
		// Curves, bounding boxes - those will most likely not be loaded
		// as we can't make any use out of this data. So consider them
		// last.
		if (r == "BoundingBox" || r == "Curve2D") {
			return 100;
		}
		return 0;
	}

	bool operator() (const IfcRepresentation* a, const IfcRepresentation* b) const {
		return Rate(a) < Rate(b);
	}
};

// ------------------------------------------------------------------------------------------------
void ProcessProductRepresentation(const IfcProduct& el, aiNode* nd, std::vector< aiNode* >& subnodes, ConversionData& conv)
{
	if(!el.Representation) {
		return;
	}

	// extract Color from metadata, if present
	unsigned int matid = ProcessMaterials( el.GetID(), std::numeric_limits<uint32_t>::max(), conv, false);
	std::vector<unsigned int> meshes;

	// we want only one representation type, so bring them in a suitable order (i.e try those
	// that look as if we could read them quickly at first). This way of reading
	// representation is relatively generic and allows the concrete implementations
	// for the different representation types to make some sensible choices what
	// to load and what not to load.
	const STEP::ListOf< STEP::Lazy< IfcRepresentation >, 1, 0 >& src = el.Representation.Get()->Representations;
	std::vector<const IfcRepresentation*> repr_ordered(src.size());
	std::copy(src.begin(),src.end(),repr_ordered.begin());
	std::sort(repr_ordered.begin(),repr_ordered.end(),RateRepresentationPredicate());
	BOOST_FOREACH(const IfcRepresentation* repr, repr_ordered) {
		bool res = false;
		BOOST_FOREACH(const IfcRepresentationItem& item, repr->Items) {
			if(const IfcMappedItem* const geo = item.ToPtr<IfcMappedItem>()) {
				res = ProcessMappedItem(*geo,nd,subnodes,matid,conv) || res;
			}
			else {
				res = ProcessRepresentationItem(item,matid,meshes,conv) || res;
			}
		}
		// if we got something meaningful at this point, skip any further representations
		if(res) {
			break;
		}
	}
	AssignAddedMeshes(meshes,nd,conv);
}

typedef std::map<std::string, std::string> Metadata;

// ------------------------------------------------------------------------------------------------
void ProcessMetadata(const ListOf< Lazy< IfcProperty >, 1, 0 >& set, ConversionData& conv, Metadata& properties, 
	const std::string& prefix = "", 
	unsigned int nest = 0) 
{
	BOOST_FOREACH(const IfcProperty& property, set) {
		const std::string& key = prefix.length() > 0 ? (prefix + "." + property.Name) : property.Name;
		if (const IfcPropertySingleValue* const singleValue = property.ToPtr<IfcPropertySingleValue>()) {
			if (singleValue->NominalValue) {
				if (const EXPRESS::STRING* str = singleValue->NominalValue.Get()->ToPtr<EXPRESS::STRING>()) {
					std::string value = static_cast<std::string>(*str);
					properties[key]=value;
				}
				else if (const EXPRESS::REAL* val = singleValue->NominalValue.Get()->ToPtr<EXPRESS::REAL>()) {
					float value = static_cast<float>(*val);
					std::stringstream s;
					s << value;
					properties[key]=s.str();
				}
				else if (const EXPRESS::INTEGER* val = singleValue->NominalValue.Get()->ToPtr<EXPRESS::INTEGER>()) {
					int64_t value = static_cast<int64_t>(*val);
					std::stringstream s;
					s << value;
					properties[key]=s.str();
				}
			}
		}
		else if (const IfcPropertyListValue* const listValue = property.ToPtr<IfcPropertyListValue>()) {
			std::stringstream ss;
			ss << "[";
			unsigned index=0;
			BOOST_FOREACH(const IfcValue::Out& v, listValue->ListValues) {
				if (!v) continue;
				if (const EXPRESS::STRING* str = v->ToPtr<EXPRESS::STRING>()) {
					std::string value = static_cast<std::string>(*str);
					ss << "'" << value << "'";
				}
				else if (const EXPRESS::REAL* val = v->ToPtr<EXPRESS::REAL>()) {
					float value = static_cast<float>(*val);
					ss << value;
				}
				else if (const EXPRESS::INTEGER* val = v->ToPtr<EXPRESS::INTEGER>()) {
					int64_t value = static_cast<int64_t>(*val);
					ss << value;
				}
				if (index+1<listValue->ListValues.size()) {
					ss << ",";
				}
				index++;
			}
			ss << "]";
			properties[key]=ss.str();
		}
		else if (const IfcComplexProperty* const complexProp = property.ToPtr<IfcComplexProperty>()) {
			if(nest > 2) { // mostly arbitrary limit to prevent stack overflow vulnerabilities
				IFCImporter::LogError("maximum nesting level for IfcComplexProperty reached, skipping this property.");
			}
			else {
				ProcessMetadata(complexProp->HasProperties, conv, properties, key, nest + 1);
			}
		}
		else {
			properties[key]="";
		}
	}
}


// ------------------------------------------------------------------------------------------------
void ProcessMetadata(uint64_t relDefinesByPropertiesID, ConversionData& conv, Metadata& properties) 
{
	if (const IfcRelDefinesByProperties* const pset = conv.db.GetObject(relDefinesByPropertiesID)->ToPtr<IfcRelDefinesByProperties>()) {
		if (const IfcPropertySet* const set = conv.db.GetObject(pset->RelatingPropertyDefinition->GetID())->ToPtr<IfcPropertySet>()) {
			ProcessMetadata(set->HasProperties, conv, properties);			
		}
	}
}

// ------------------------------------------------------------------------------------------------
aiNode* ProcessSpatialStructure(aiNode* parent, const IfcProduct& el, ConversionData& conv, std::vector<TempOpening>* collect_openings = NULL)
{
	const STEP::DB::RefMap& refs = conv.db.GetRefs();

	// skip over space and annotation nodes - usually, these have no meaning in Assimp's context
	bool skipGeometry = false;
	if(conv.settings.skipSpaceRepresentations) {
		if(el.ToPtr<IfcSpace>()) {
			IFCImporter::LogDebug("skipping IfcSpace entity due to importer settings");
			skipGeometry = true;
		}
	}

	if(conv.settings.skipAnnotations) {
		if(el.ToPtr<IfcAnnotation>()) {
			IFCImporter::LogDebug("skipping IfcAnnotation entity due to importer settings");
			return NULL;
		}
	}

	// add an output node for this spatial structure
	std::auto_ptr<aiNode> nd(new aiNode());
	nd->mName.Set(el.GetClassName()+"_"+(el.Name?el.Name.Get():"Unnamed")+"_"+el.GlobalId);
	nd->mParent = parent;

	conv.already_processed.insert(el.GetID());

	// check for node metadata
	STEP::DB::RefMapRange children = refs.equal_range(el.GetID());
	if (children.first!=refs.end()) {
		Metadata properties;
		if (children.first==children.second) {
			// handles single property set
			ProcessMetadata((*children.first).second, conv, properties);
		} 
		else {
			// handles multiple property sets (currently all property sets are merged,
			// which may not be the best solution in the long run)
			for (STEP::DB::RefMap::const_iterator it=children.first; it!=children.second; ++it) {
				ProcessMetadata((*it).second, conv, properties);
			}
		}

		if (!properties.empty()) {
			aiMetadata* data = new aiMetadata();
			data->mNumProperties = properties.size();
			data->mKeys = new aiString[data->mNumProperties]();
			data->mValues = new aiMetadataEntry[data->mNumProperties]();

			unsigned int index = 0;
			BOOST_FOREACH(const Metadata::value_type& kv, properties)
				data->Set(index++, kv.first, aiString(kv.second));

			nd->mMetaData = data;
		}
	}

	if(el.ObjectPlacement) {
		ResolveObjectPlacement(nd->mTransformation,el.ObjectPlacement.Get(),conv);
	}

	std::vector<TempOpening> openings;

	IfcMatrix4 myInv;
	bool didinv = false;

	// convert everything contained directly within this structure,
	// this may result in more nodes.
	std::vector< aiNode* > subnodes;
	try {
		// locate aggregates and 'contained-in-here'-elements of this spatial structure and add them in recursively
		// on our way, collect openings in *this* element
		STEP::DB::RefMapRange range = refs.equal_range(el.GetID());

		for(STEP::DB::RefMapRange range2 = range; range2.first != range.second; ++range2.first) {
			// skip over meshes that have already been processed before. This is strictly necessary
			// because the reverse indices also include references contained in argument lists and
			// therefore every element has a back-reference hold by its parent.
			if (conv.already_processed.find((*range2.first).second) != conv.already_processed.end()) {
				continue;
			}
			const STEP::LazyObject& obj = conv.db.MustGetObject((*range2.first).second);

			// handle regularly-contained elements
			if(const IfcRelContainedInSpatialStructure* const cont = obj->ToPtr<IfcRelContainedInSpatialStructure>()) {
				if(cont->RelatingStructure->GetID() != el.GetID()) {
					continue;
				}
				BOOST_FOREACH(const IfcProduct& pro, cont->RelatedElements) {		
					if(pro.ToPtr<IfcOpeningElement>()) {
						// IfcOpeningElement is handled below. Sadly we can't use it here as is:
						// The docs say that opening elements are USUALLY attached to building storey,
						// but we want them for the building elements to which they belong.
						continue;
					}
					
					aiNode* const ndnew = ProcessSpatialStructure(nd.get(),pro,conv,NULL);
					if(ndnew) {
						subnodes.push_back( ndnew );
					}
				}
			}
			// handle openings, which we collect in a list rather than adding them to the node graph
			else if(const IfcRelVoidsElement* const fills = obj->ToPtr<IfcRelVoidsElement>()) {
				if(fills->RelatingBuildingElement->GetID() == el.GetID()) {
					const IfcFeatureElementSubtraction& open = fills->RelatedOpeningElement;

					// move opening elements to a separate node since they are semantically different than elements that are just 'contained'
					std::auto_ptr<aiNode> nd_aggr(new aiNode());
					nd_aggr->mName.Set("$RelVoidsElement");
					nd_aggr->mParent = nd.get();

					nd_aggr->mTransformation = nd->mTransformation;

					std::vector<TempOpening> openings_local;
					aiNode* const ndnew = ProcessSpatialStructure( nd_aggr.get(),open, conv,&openings_local);
					if (ndnew) {

						nd_aggr->mNumChildren = 1;
						nd_aggr->mChildren = new aiNode*[1]();

						
						nd_aggr->mChildren[0] = ndnew;
						
						if(openings_local.size()) {
							if (!didinv) {
								myInv = aiMatrix4x4(nd->mTransformation ).Inverse();
								didinv = true;
							}

							// we need all openings to be in the local space of *this* node, so transform them
							BOOST_FOREACH(TempOpening& op,openings_local) {
								op.Transform( myInv*nd_aggr->mChildren[0]->mTransformation);
								openings.push_back(op);
							}
						}
						subnodes.push_back( nd_aggr.release() );
					}
				}
			}
		}

		for(;range.first != range.second; ++range.first) {
			// see note in loop above
			if (conv.already_processed.find((*range.first).second) != conv.already_processed.end()) {
				continue;
			}
			if(const IfcRelAggregates* const aggr = conv.db.GetObject((*range.first).second)->ToPtr<IfcRelAggregates>()) {
				if(aggr->RelatingObject->GetID() != el.GetID()) {
					continue;
				}

				// move aggregate elements to a separate node since they are semantically different than elements that are just 'contained'
				std::auto_ptr<aiNode> nd_aggr(new aiNode());
				nd_aggr->mName.Set("$RelAggregates");
				nd_aggr->mParent = nd.get();

				nd_aggr->mTransformation = nd->mTransformation;

				nd_aggr->mChildren = new aiNode*[aggr->RelatedObjects.size()]();
				BOOST_FOREACH(const IfcObjectDefinition& def, aggr->RelatedObjects) {
					if(const IfcProduct* const prod = def.ToPtr<IfcProduct>()) {

						aiNode* const ndnew = ProcessSpatialStructure(nd_aggr.get(),*prod,conv,NULL);
						if(ndnew) {
							nd_aggr->mChildren[nd_aggr->mNumChildren++] = ndnew;
						}
					}
				}
			
				subnodes.push_back( nd_aggr.release() );
			}
		}

		conv.collect_openings = collect_openings;
		if(!conv.collect_openings) {
			conv.apply_openings = &openings;
		}

		if (!skipGeometry) {
		  ProcessProductRepresentation(el,nd.get(),subnodes,conv);
		  conv.apply_openings = conv.collect_openings = NULL;
		}

		if (subnodes.size()) {
			nd->mChildren = new aiNode*[subnodes.size()]();
			BOOST_FOREACH(aiNode* nd2, subnodes) {
				nd->mChildren[nd->mNumChildren++] = nd2;
				nd2->mParent = nd.get();
			}
		}
	}
	catch(...) {
		// it hurts, but I don't want to pull boost::ptr_vector into -noboost only for these few spots here
		std::for_each(subnodes.begin(),subnodes.end(),delete_fun<aiNode>());
		throw;
	}

	ai_assert(conv.already_processed.find(el.GetID()) != conv.already_processed.end());
	conv.already_processed.erase(conv.already_processed.find(el.GetID()));
	return nd.release();
}

// ------------------------------------------------------------------------------------------------
void ProcessSpatialStructures(ConversionData& conv)
{
	// XXX add support for multiple sites (i.e. IfcSpatialStructureElements with composition == COMPLEX)


	// process all products in the file. it is reasonable to assume that a
	// file that is relevant for us contains at least a site or a building.
	const STEP::DB::ObjectMapByType& map = conv.db.GetObjectsByType();

	ai_assert(map.find("ifcsite") != map.end());
	const STEP::DB::ObjectSet* range = &map.find("ifcsite")->second;

	if (range->empty()) {
		ai_assert(map.find("ifcbuilding") != map.end());
		range = &map.find("ifcbuilding")->second;
		if (range->empty()) {
			// no site, no building -  fail;
			IFCImporter::ThrowException("no root element found (expected IfcBuilding or preferably IfcSite)");
		}
	}

	
	BOOST_FOREACH(const STEP::LazyObject* lz, *range) {
		const IfcSpatialStructureElement* const prod = lz->ToPtr<IfcSpatialStructureElement>();
		if(!prod) {
			continue;
		}
		IFCImporter::LogDebug("looking at spatial structure `" + (prod->Name ? prod->Name.Get() : "unnamed") + "`" + (prod->ObjectType? " which is of type " + prod->ObjectType.Get():""));
	
		// the primary site is referenced by an IFCRELAGGREGATES element which assigns it to the IFCPRODUCT
		const STEP::DB::RefMap& refs = conv.db.GetRefs();
		STEP::DB::RefMapRange range = refs.equal_range(conv.proj.GetID());
		for(;range.first != range.second; ++range.first) {
			if(const IfcRelAggregates* const aggr = conv.db.GetObject((*range.first).second)->ToPtr<IfcRelAggregates>()) {
			
				BOOST_FOREACH(const IfcObjectDefinition& def, aggr->RelatedObjects) {
					// comparing pointer values is not sufficient, we would need to cast them to the same type first
					// as there is multiple inheritance in the game.
					if (def.GetID() == prod->GetID()) { 
						IFCImporter::LogDebug("selecting this spatial structure as root structure");
						// got it, this is the primary site.
						conv.out->mRootNode = ProcessSpatialStructure(NULL,*prod,conv,NULL);
						return;
					}
				}

			}
		}
	}

	
	IFCImporter::LogWarn("failed to determine primary site element, taking the first IfcSite");
	BOOST_FOREACH(const STEP::LazyObject* lz, *range) {
		const IfcSpatialStructureElement* const prod = lz->ToPtr<IfcSpatialStructureElement>();
		if(!prod) {
			continue;
		}

		conv.out->mRootNode = ProcessSpatialStructure(NULL,*prod,conv,NULL);
		return;
	}

	IFCImporter::ThrowException("failed to determine primary site element");
}

// ------------------------------------------------------------------------------------------------
void MakeTreeRelative(aiNode* start, const aiMatrix4x4& combined)
{
	// combined is the parent's absolute transformation matrix
	const aiMatrix4x4 old = start->mTransformation;

	if (!combined.IsIdentity()) {
		start->mTransformation = aiMatrix4x4(combined).Inverse() * start->mTransformation;
	}

	// All nodes store absolute transformations right now, so we need to make them relative
	for (unsigned int i = 0; i < start->mNumChildren; ++i) {
		MakeTreeRelative(start->mChildren[i],old);
	}
}

// ------------------------------------------------------------------------------------------------
void MakeTreeRelative(ConversionData& conv)
{
	MakeTreeRelative(conv.out->mRootNode,IfcMatrix4());
}

} // !anon



#endif