assimp/code/IFCGeometry.cpp

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/** @file  IFCGeometry.cpp
 *  @brief Geometry conversion and synthesis for IFC
 */

#include "AssimpPCH.h"

#ifndef ASSIMP_BUILD_NO_IFC_IMPORTER
#include "IFCUtil.h"
#include "PolyTools.h"
#include "ProcessHelper.h"

#include "../contrib/poly2tri/poly2tri/poly2tri.h"
#include "../contrib/clipper/clipper.hpp"

#include <iterator>

namespace Assimp {
	namespace IFC {

// ------------------------------------------------------------------------------------------------
bool ProcessPolyloop(const IfcPolyLoop& loop, TempMesh& meshout, ConversionData& /*conv*/)
{
	size_t cnt = 0;
	BOOST_FOREACH(const IfcCartesianPoint& c, loop.Polygon) {
		IfcVector3 tmp;
		ConvertCartesianPoint(tmp,c);

		meshout.verts.push_back(tmp);
		++cnt;
	}

	meshout.vertcnt.push_back(cnt);

	// zero- or one- vertex polyloops simply ignored
	if (meshout.vertcnt.back() > 1) { 
		return true;
	}
	
	if (meshout.vertcnt.back()==1) {
		meshout.vertcnt.pop_back();
		meshout.verts.pop_back();
	}
	return false;
}

// ------------------------------------------------------------------------------------------------
void ProcessPolygonBoundaries(TempMesh& result, const TempMesh& inmesh, size_t master_bounds = (size_t)-1) 
{
	// handle all trivial cases
	if(inmesh.vertcnt.empty()) {
		return;
	}
	if(inmesh.vertcnt.size() == 1) {
		result.Append(inmesh);
		return;
	}

	ai_assert(std::count(inmesh.vertcnt.begin(), inmesh.vertcnt.end(), 0) == 0);

	typedef std::vector<unsigned int>::const_iterator face_iter;

	face_iter begin = inmesh.vertcnt.begin(), end = inmesh.vertcnt.end(), iit;
	std::vector<unsigned int>::const_iterator outer_polygon_it = end;

	// major task here: given a list of nested polygon boundaries (one of which
	// is the outer contour), reduce the triangulation task arising here to
	// one that can be solved using the "quadrulation" algorithm which we use
	// for pouring windows out of walls. The algorithm does not handle all
	// cases but at least it is numerically stable and gives "nice" triangles.

	// first compute normals for all polygons using Newell's algorithm
	// do not normalize 'normals', we need the original length for computing the polygon area
	std::vector<IfcVector3> normals;
	inmesh.ComputePolygonNormals(normals,false);

	// One of the polygons might be a IfcFaceOuterBound (in which case `master_bounds` 
	// is its index). Sadly we can't rely on it, the docs say 'At most one of the bounds 
	// shall be of the type IfcFaceOuterBound' 
	IfcFloat area_outer_polygon = 1e-10f;
	if (master_bounds != (size_t)-1) {
		ai_assert(master_bounds < inmesh.vertcnt.size());
		outer_polygon_it = begin + master_bounds;
	}
	else {
		for(iit = begin; iit != end; iit++) {
			// find the polygon with the largest area and take it as the outer bound. 
			IfcVector3& n = normals[std::distance(begin,iit)];
			const IfcFloat area = n.SquareLength();
			if (area > area_outer_polygon) {
				area_outer_polygon = area;
				outer_polygon_it = iit;
			}
		}
	}

	ai_assert(outer_polygon_it != end);

	const size_t outer_polygon_size = *outer_polygon_it;
	const IfcVector3& master_normal = normals[std::distance(begin, outer_polygon_it)];

	// Generate fake openings to meet the interface for the quadrulate
	// algorithm. It boils down to generating small boxes given the
	// inner polygon and the surface normal of the outer contour.
	// It is important that we use the outer contour's normal because
	// this is the plane onto which the quadrulate algorithm will
	// project the entire mesh.
	std::vector<TempOpening> fake_openings;
	fake_openings.reserve(inmesh.vertcnt.size()-1);

	std::vector<IfcVector3>::const_iterator vit = inmesh.verts.begin(), outer_vit;

	for(iit = begin; iit != end; vit += *iit++) {
		if (iit == outer_polygon_it) {
			outer_vit = vit;
			continue;
		}

		// Filter degenerate polygons to keep them from causing trouble later on
		IfcVector3& n = normals[std::distance(begin,iit)];
		const IfcFloat area = n.SquareLength();
		if (area < 1e-5f) {
			IFCImporter::LogWarn("skipping degenerate polygon (ProcessPolygonBoundaries)");
			continue;
		}

		fake_openings.push_back(TempOpening());
		TempOpening& opening = fake_openings.back();

		opening.extrusionDir = master_normal;
		opening.solid = NULL;

		opening.profileMesh = boost::make_shared<TempMesh>();
		opening.profileMesh->verts.reserve(*iit);
		opening.profileMesh->vertcnt.push_back(*iit);

		std::copy(vit, vit + *iit, std::back_inserter(opening.profileMesh->verts)); 
	}

	// fill a mesh with ONLY the main polygon 
	TempMesh temp;
	temp.verts.reserve(outer_polygon_size);
	temp.vertcnt.push_back(outer_polygon_size);
	std::copy(outer_vit, outer_vit+outer_polygon_size,
		std::back_inserter(temp.verts));

	GenerateOpenings(fake_openings, normals, temp, false, false);
	result.Append(temp);
}

// ------------------------------------------------------------------------------------------------
void ProcessConnectedFaceSet(const IfcConnectedFaceSet& fset, TempMesh& result, ConversionData& conv)
{
	BOOST_FOREACH(const IfcFace& face, fset.CfsFaces) {
		// size_t ob = -1, cnt = 0;
		TempMesh meshout;
		BOOST_FOREACH(const IfcFaceBound& bound, face.Bounds) {
			
			if(const IfcPolyLoop* const polyloop = bound.Bound->ToPtr<IfcPolyLoop>()) {
				if(ProcessPolyloop(*polyloop, meshout,conv)) {

					// The outer boundary is better determined by checking which
					// polygon covers the largest area.

					//if(bound.ToPtr<IfcFaceOuterBound>()) {
					//	ob = cnt;
					//}
					//++cnt;

				}
			}
			else {
				IFCImporter::LogWarn("skipping unknown IfcFaceBound entity, type is " + bound.Bound->GetClassName());
				continue;
			}

			// And this, even though it is sometimes TRUE and sometimes FALSE,
			// does not really improve results.

			/*if(!IsTrue(bound.Orientation)) {
				size_t c = 0;
				BOOST_FOREACH(unsigned int& c, meshout.vertcnt) {
					std::reverse(result.verts.begin() + cnt,result.verts.begin() + cnt + c);
					cnt += c;
				}
			}*/
		}
		ProcessPolygonBoundaries(result, meshout);
	}
}

// ------------------------------------------------------------------------------------------------
void ProcessRevolvedAreaSolid(const IfcRevolvedAreaSolid& solid, TempMesh& result, ConversionData& conv)
{
	TempMesh meshout;

	// first read the profile description
	if(!ProcessProfile(*solid.SweptArea,meshout,conv) || meshout.verts.size()<=1) {
		return;
	}

	IfcVector3 axis, pos;
	ConvertAxisPlacement(axis,pos,solid.Axis);

	IfcMatrix4 tb0,tb1;
	IfcMatrix4::Translation(pos,tb0);
	IfcMatrix4::Translation(-pos,tb1);

	const std::vector<IfcVector3>& in = meshout.verts;
	const size_t size=in.size();
	
	bool has_area = solid.SweptArea->ProfileType == "AREA" && size>2;
	const IfcFloat max_angle = solid.Angle*conv.angle_scale;
	if(std::fabs(max_angle) < 1e-3) {
		if(has_area) {
			result = meshout;
		}
		return;
	}

	const unsigned int cnt_segments = std::max(2u,static_cast<unsigned int>(16 * std::fabs(max_angle)/AI_MATH_HALF_PI_F));
	const IfcFloat delta = max_angle/cnt_segments;

	has_area = has_area && std::fabs(max_angle) < AI_MATH_TWO_PI_F*0.99;
	
	result.verts.reserve(size*((cnt_segments+1)*4+(has_area?2:0)));
	result.vertcnt.reserve(size*cnt_segments+2);

	IfcMatrix4 rot;
	rot = tb0 * IfcMatrix4::Rotation(delta,axis,rot) * tb1;

	size_t base = 0;
	std::vector<IfcVector3>& out = result.verts;

	// dummy data to simplify later processing
	for(size_t i = 0; i < size; ++i) {
		out.insert(out.end(),4,in[i]);
	}

	for(unsigned int seg = 0; seg < cnt_segments; ++seg) {
		for(size_t i = 0; i < size; ++i) {
			const size_t next = (i+1)%size;

			result.vertcnt.push_back(4);
			const IfcVector3& base_0 = out[base+i*4+3],base_1 = out[base+next*4+3];

			out.push_back(base_0);
			out.push_back(base_1);
			out.push_back(rot*base_1);
			out.push_back(rot*base_0);
		}
		base += size*4;
	}

	out.erase(out.begin(),out.begin()+size*4);

	if(has_area) {
		// leave the triangulation of the profile area to the ear cutting 
		// implementation in aiProcess_Triangulate - for now we just
		// feed in two huge polygons.
		base -= size*8;
		for(size_t i = size; i--; ) {
			out.push_back(out[base+i*4+3]);
		}
		for(size_t i = 0; i < size; ++i ) {
			out.push_back(out[i*4]);
		}
		result.vertcnt.push_back(size);
		result.vertcnt.push_back(size);
	}

	IfcMatrix4 trafo;
	ConvertAxisPlacement(trafo, solid.Position);
	
	result.Transform(trafo);
	IFCImporter::LogDebug("generate mesh procedurally by radial extrusion (IfcRevolvedAreaSolid)");
}



// ------------------------------------------------------------------------------------------------
void ProcessSweptDiskSolid(const IfcSweptDiskSolid solid, TempMesh& result, ConversionData& conv)
{
	const Curve* const curve = Curve::Convert(*solid.Directrix, conv);
	if(!curve) {
		IFCImporter::LogError("failed to convert Directrix curve (IfcSweptDiskSolid)");
		return;
	}
	
	const unsigned int cnt_segments = 16;
	const IfcFloat deltaAngle = AI_MATH_TWO_PI/cnt_segments;

	const size_t samples = curve->EstimateSampleCount(solid.StartParam,solid.EndParam);

	result.verts.reserve(cnt_segments * samples * 4);
	result.vertcnt.reserve((cnt_segments - 1) * samples);

	std::vector<IfcVector3> points;
	points.reserve(cnt_segments * samples);

	TempMesh temp;
	curve->SampleDiscrete(temp,solid.StartParam,solid.EndParam);
	const std::vector<IfcVector3>& curve_points = temp.verts;

	if(curve_points.empty()) {
		IFCImporter::LogWarn("curve evaluation yielded no points (IfcSweptDiskSolid)");
		return;
	}

	IfcVector3 current = curve_points[0];
	IfcVector3 previous = current;
	IfcVector3 next;

	IfcVector3 startvec;
	startvec.x = 1.0f;
	startvec.y = 1.0f;
	startvec.z = 1.0f;

	unsigned int last_dir = 0;

	// generate circles at the sweep positions
	for(size_t i = 0; i < samples; ++i) {

		if(i != samples - 1) {
			next = curve_points[i + 1];
		}

		// get a direction vector reflecting the approximate curvature (i.e. tangent)
		IfcVector3 d = (current-previous) + (next-previous);
	
		d.Normalize();

		// figure out an arbitrary point q so that (p-q) * d = 0,
		// try to maximize ||(p-q)|| * ||(p_last-q_last)|| 
		IfcVector3 q;
		bool take_any = false;

		for (unsigned int i = 0; i < 2; ++i, take_any = true) {
			if ((last_dir == 0 || take_any) && std::abs(d.x) > 1e-6) {
				q.y = startvec.y;
				q.z = startvec.z;
				q.x = -(d.y * q.y + d.z * q.z) / d.x;
				last_dir = 0;
				break;
			}
			else if ((last_dir == 1 || take_any) && std::abs(d.y) > 1e-6) {
				q.x = startvec.x;
				q.z = startvec.z;
				q.y = -(d.x * q.x + d.z * q.z) / d.y;
				last_dir = 1;
				break;
			}
			else if ((last_dir == 2 && std::abs(d.z) > 1e-6) || take_any) {
				q.y = startvec.y;
				q.x = startvec.x;
				q.z = -(d.y * q.y + d.x * q.x) / d.z;
				last_dir = 2;
				break;
			}
		}

		q *= solid.Radius / q.Length();
		startvec = q;

		// generate a rotation matrix to rotate q around d
		IfcMatrix4 rot;
		IfcMatrix4::Rotation(deltaAngle,d,rot);

		for (unsigned int seg = 0; seg < cnt_segments; ++seg, q *= rot ) {
			points.push_back(q + current);	
		}

		previous = current;
		current = next;
	}

	// make quads
	for(size_t i = 0; i < samples - 1; ++i) {

		const aiVector3D& this_start = points[ i * cnt_segments ];

		// locate corresponding point on next sample ring
		unsigned int best_pair_offset = 0;
		float best_distance_squared = 1e10f;
		for (unsigned int seg = 0; seg < cnt_segments; ++seg) {
			const aiVector3D& p = points[ (i+1) * cnt_segments + seg];
			const float l = (p-this_start).SquareLength();

			if(l < best_distance_squared) {
				best_pair_offset = seg;
				best_distance_squared = l;
			}
		}

		for (unsigned int seg = 0; seg < cnt_segments; ++seg) {

			result.verts.push_back(points[ i * cnt_segments + (seg % cnt_segments)]);
			result.verts.push_back(points[ i * cnt_segments + (seg + 1) % cnt_segments]);
			result.verts.push_back(points[ (i+1) * cnt_segments + ((seg + 1 + best_pair_offset) % cnt_segments)]);
			result.verts.push_back(points[ (i+1) * cnt_segments + ((seg + best_pair_offset) % cnt_segments)]);

			IfcVector3& v1 = *(result.verts.end()-1);
			IfcVector3& v2 = *(result.verts.end()-2);
			IfcVector3& v3 = *(result.verts.end()-3);
			IfcVector3& v4 = *(result.verts.end()-4);

			if (((v4-v3) ^ (v4-v1)) * (v4 - curve_points[i]) < 0.0f) {			
				std::swap(v4, v1);
				std::swap(v3, v2);
			} 

			result.vertcnt.push_back(4);
		}
	}

	IFCImporter::LogDebug("generate mesh procedurally by sweeping a disk along a curve (IfcSweptDiskSolid)");
}

// ------------------------------------------------------------------------------------------------
IfcMatrix3 DerivePlaneCoordinateSpace(const TempMesh& curmesh, bool& ok, IfcVector3& norOut) 
{
	const std::vector<IfcVector3>& out = curmesh.verts;
	IfcMatrix3 m;

	ok = true;

	// The input "mesh" must be a single polygon
	const size_t s = out.size();
	assert(curmesh.vertcnt.size() == 1 && curmesh.vertcnt.back() == s);

	const IfcVector3 any_point = out[s-1];
	IfcVector3 nor; 

	// The input polygon is arbitrarily shaped, therefore we might need some tries
	// until we find a suitable normal. Note that Newell's algorithm would give
	// a more robust result, but this variant also gives us a suitable first
	// axis for the 2D coordinate space on the polygon plane, exploiting the
	// fact that the input polygon is nearly always a quad.
	bool done = false;
	size_t i, j;
	for (i = 0; !done && i < s-2; done || ++i) {
		for (j = i+1; j < s-1; ++j) {
			nor = -((out[i]-any_point)^(out[j]-any_point));
			if(std::fabs(nor.Length()) > 1e-8f) {
				done = true;
				break;
			}
		}
	}

	if(!done) {
		ok = false;
		return m;
	}

	nor.Normalize();
	norOut = nor;

	IfcVector3 r = (out[i]-any_point);
	r.Normalize();

	//if(d) {
	//	*d = -any_point * nor;
	//}

	// Reconstruct orthonormal basis
	// XXX use Gram Schmidt for increased robustness
	IfcVector3 u = r ^ nor;
	u.Normalize();

	m.a1 = r.x;
	m.a2 = r.y;
	m.a3 = r.z;

	m.b1 = u.x;
	m.b2 = u.y;
	m.b3 = u.z;

	m.c1 = -nor.x;
	m.c2 = -nor.y;
	m.c3 = -nor.z;

	return m;
}

// Extrudes the given polygon along the direction, converts it into an opening or applies all openings as necessary.
void ProcessExtrudedArea(const IfcExtrudedAreaSolid& solid, const TempMesh& curve,
	const IfcVector3& extrusionDir, TempMesh& result, ConversionData &conv, bool collect_openings)
{
	// Outline: 'curve' is now a list of vertex points forming the underlying profile, extrude along the given axis, 
	// forming new triangles.
	const bool has_area = solid.SweptArea->ProfileType == "AREA" && curve.verts.size() > 2;
	if( solid.Depth < 1e-6 ) {
		if( has_area ) {
			result.Append(curve);
		}
		return;
	}

	result.verts.reserve(curve.verts.size()*(has_area ? 4 : 2));
	result.vertcnt.reserve(curve.verts.size() + 2);
	std::vector<IfcVector3> in = curve.verts;

	// First step: transform all vertices into the target coordinate space
	IfcMatrix4 trafo;
	ConvertAxisPlacement(trafo, solid.Position);

	IfcVector3 vmin, vmax;
	MinMaxChooser<IfcVector3>()(vmin, vmax);
	BOOST_FOREACH(IfcVector3& v, in) {
		v *= trafo;

		vmin = std::min(vmin, v);
		vmax = std::max(vmax, v);
	}

	vmax -= vmin;
	const IfcFloat diag = vmax.Length();
	IfcVector3 dir = IfcMatrix3(trafo) * extrusionDir;

	// reverse profile polygon if it's winded in the wrong direction in relation to the extrusion direction
	IfcVector3 profileNormal = TempMesh::ComputePolygonNormal(in.data(), in.size());
	if( profileNormal * dir < 0.0 )
		std::reverse(in.begin(), in.end());

	std::vector<IfcVector3> nors;
	const bool openings = !!conv.apply_openings && conv.apply_openings->size();

	// Compute the normal vectors for all opening polygons as a prerequisite
	// to TryAddOpenings_Poly2Tri()
	// XXX this belongs into the aforementioned function
	if( openings ) {

		if( !conv.settings.useCustomTriangulation ) {
			// it is essential to apply the openings in the correct spatial order. The direction	 
			// doesn't matter, but we would screw up if we started with e.g. a door in between	 
			// two windows.	 
			std::sort(conv.apply_openings->begin(), conv.apply_openings->end(), TempOpening::DistanceSorter(in[0]));
		}

		nors.reserve(conv.apply_openings->size());
		BOOST_FOREACH(TempOpening& t, *conv.apply_openings) {
			TempMesh& bounds = *t.profileMesh.get();

			if( bounds.verts.size() <= 2 ) {
				nors.push_back(IfcVector3());
				continue;
			}
			nors.push_back(((bounds.verts[2] - bounds.verts[0]) ^ (bounds.verts[1] - bounds.verts[0])).Normalize());
		}
	}


	TempMesh temp;
	TempMesh& curmesh = openings ? temp : result;
	std::vector<IfcVector3>& out = curmesh.verts;

	size_t sides_with_openings = 0;
	for( size_t i = 0; i < in.size(); ++i ) {
		const size_t next = (i + 1) % in.size();

		curmesh.vertcnt.push_back(4);

		out.push_back(in[i]);
		out.push_back(in[next]);
		out.push_back(in[next] + dir);
		out.push_back(in[i] + dir);

		if( openings ) {
			if( (in[i] - in[next]).Length() > diag * 0.1 && GenerateOpenings(*conv.apply_openings, nors, temp, true, true, dir) ) {
				++sides_with_openings;
			}

			result.Append(temp);
			temp.Clear();
		}
	}

	if( openings ) {
		BOOST_FOREACH(TempOpening& opening, *conv.apply_openings) {
			if( !opening.wallPoints.empty() ) {
				IFCImporter::LogError("failed to generate all window caps");
			}
			opening.wallPoints.clear();
		}
	}

	size_t sides_with_v_openings = 0;
	if( has_area ) {

		for( size_t n = 0; n < 2; ++n ) {
			if( n > 0 ) {
				for( size_t i = 0; i < in.size(); ++i )
					out.push_back(in[i] + dir);
			}
			else {
				for( size_t i = in.size(); i--; )
					out.push_back(in[i]);
			}

			curmesh.vertcnt.push_back(in.size());
			if( openings && in.size() > 2 ) {
				if( GenerateOpenings(*conv.apply_openings, nors, temp, true, true, dir) ) {
					++sides_with_v_openings;
				}

				result.Append(temp);
				temp.Clear();
			}
		}
	}

	if( openings && ((sides_with_openings == 1 && sides_with_openings) || (sides_with_v_openings == 2 && sides_with_v_openings)) ) {
		IFCImporter::LogWarn("failed to resolve all openings, presumably their topology is not supported by Assimp");
	}

	IFCImporter::LogDebug("generate mesh procedurally by extrusion (IfcExtrudedAreaSolid)");

	// If this is an opening element, store both the extruded mesh and the 2D profile mesh
	// it was created from. Return an empty mesh to the caller.
	if( collect_openings && !result.IsEmpty() ) {
		ai_assert(conv.collect_openings);
		boost::shared_ptr<TempMesh> profile = boost::shared_ptr<TempMesh>(new TempMesh());
		profile->Swap(result);

		boost::shared_ptr<TempMesh> profile2D = boost::shared_ptr<TempMesh>(new TempMesh());
		profile2D->verts.insert(profile2D->verts.end(), in.begin(), in.end());
		profile2D->vertcnt.push_back(in.size());
		conv.collect_openings->push_back(TempOpening(&solid, dir, profile, profile2D));

		ai_assert(result.IsEmpty());
	}
}

// ------------------------------------------------------------------------------------------------
void ProcessExtrudedAreaSolid(const IfcExtrudedAreaSolid& solid, TempMesh& result, 
	ConversionData& conv, bool collect_openings)
{
	TempMesh meshout;
	
	// First read the profile description. 
	if(!ProcessProfile(*solid.SweptArea,meshout,conv) || meshout.verts.size()<=1) {
		return;
	}

	IfcVector3 dir;
	ConvertDirection(dir,solid.ExtrudedDirection);
	dir *= solid.Depth;

	// Some profiles bring their own holes, for which we need to provide a container. This all is somewhat backwards, 
	// and there's still so many corner cases uncovered - we really need a generic solution to all of this hole carving.
	std::vector<TempOpening> fisherPriceMyFirstOpenings;
	std::vector<TempOpening>* oldApplyOpenings = conv.apply_openings;
	if( const IfcArbitraryProfileDefWithVoids* const cprofile = solid.SweptArea->ToPtr<IfcArbitraryProfileDefWithVoids>() ) {
		if( !cprofile->InnerCurves.empty() ) {
			// read all inner curves and extrude them to form proper openings. 
			std::vector<TempOpening>* oldCollectOpenings = conv.collect_openings;
			conv.collect_openings = &fisherPriceMyFirstOpenings;

			BOOST_FOREACH(const IfcCurve* curve, cprofile->InnerCurves) {
				TempMesh curveMesh, tempMesh;
				ProcessCurve(*curve, curveMesh, conv);
				ProcessExtrudedArea(solid, curveMesh, dir, tempMesh, conv, true);
			}
			// and then apply those to the geometry we're about to generate
			conv.apply_openings = conv.collect_openings;
			conv.collect_openings = oldCollectOpenings;
		}
	}

	ProcessExtrudedArea(solid, meshout, dir, result, conv, collect_openings);
	conv.apply_openings = oldApplyOpenings;
}

// ------------------------------------------------------------------------------------------------
void ProcessSweptAreaSolid(const IfcSweptAreaSolid& swept, TempMesh& meshout, 
	ConversionData& conv)
{
	if(const IfcExtrudedAreaSolid* const solid = swept.ToPtr<IfcExtrudedAreaSolid>()) {
		ProcessExtrudedAreaSolid(*solid,meshout,conv, !!conv.collect_openings);
	}
	else if(const IfcRevolvedAreaSolid* const rev = swept.ToPtr<IfcRevolvedAreaSolid>()) {
		ProcessRevolvedAreaSolid(*rev,meshout,conv);
	}
	else {
		IFCImporter::LogWarn("skipping unknown IfcSweptAreaSolid entity, type is " + swept.GetClassName());
	}
}

// ------------------------------------------------------------------------------------------------
bool ProcessGeometricItem(const IfcRepresentationItem& geo, unsigned int matid, std::vector<unsigned int>& mesh_indices, 
	ConversionData& conv)
{
	bool fix_orientation = false;
	boost::shared_ptr< TempMesh > meshtmp = boost::make_shared<TempMesh>(); 
	if(const IfcShellBasedSurfaceModel* shellmod = geo.ToPtr<IfcShellBasedSurfaceModel>()) {
		BOOST_FOREACH(boost::shared_ptr<const IfcShell> shell,shellmod->SbsmBoundary) {
			try {
				const EXPRESS::ENTITY& e = shell->To<ENTITY>();
				const IfcConnectedFaceSet& fs = conv.db.MustGetObject(e).To<IfcConnectedFaceSet>(); 

				ProcessConnectedFaceSet(fs,*meshtmp.get(),conv);
			}
			catch(std::bad_cast&) {
				IFCImporter::LogWarn("unexpected type error, IfcShell ought to inherit from IfcConnectedFaceSet");
			}
		}
		fix_orientation = true;
	}
	else  if(const IfcConnectedFaceSet* fset = geo.ToPtr<IfcConnectedFaceSet>()) {
		ProcessConnectedFaceSet(*fset,*meshtmp.get(),conv);
		fix_orientation = true;
	}	
	else  if(const IfcSweptAreaSolid* swept = geo.ToPtr<IfcSweptAreaSolid>()) {
		ProcessSweptAreaSolid(*swept,*meshtmp.get(),conv);
	}   
	else  if(const IfcSweptDiskSolid* disk = geo.ToPtr<IfcSweptDiskSolid>()) {
		ProcessSweptDiskSolid(*disk,*meshtmp.get(),conv);
	}   
	else if(const IfcManifoldSolidBrep* brep = geo.ToPtr<IfcManifoldSolidBrep>()) {
		ProcessConnectedFaceSet(brep->Outer,*meshtmp.get(),conv);
		fix_orientation = true;
	} 
	else if(const IfcFaceBasedSurfaceModel* surf = geo.ToPtr<IfcFaceBasedSurfaceModel>()) {
		BOOST_FOREACH(const IfcConnectedFaceSet& fc, surf->FbsmFaces) {
			ProcessConnectedFaceSet(fc,*meshtmp.get(),conv);
		}
		fix_orientation = true;
	}  
	else  if(const IfcBooleanResult* boolean = geo.ToPtr<IfcBooleanResult>()) {
		ProcessBoolean(*boolean,*meshtmp.get(),conv);
	}
	else if(geo.ToPtr<IfcBoundingBox>()) {
		// silently skip over bounding boxes
		return false; 
	} 
	else {
		IFCImporter::LogWarn("skipping unknown IfcGeometricRepresentationItem entity, type is " + geo.GetClassName());
		return false;
	}

	// Do we just collect openings for a parent element (i.e. a wall)? 
	// In such a case, we generate the polygonal mesh as usual,
	// but attach it to a TempOpening instance which will later be applied
	// to the wall it pertains to.

	// Note: swep area solids are added in ProcessExtrudedAreaSolid(),
	// which returns an empty mesh.
	if(conv.collect_openings) {
		if (!meshtmp->IsEmpty()) {
			conv.collect_openings->push_back(TempOpening(geo.ToPtr<IfcSolidModel>(),
				IfcVector3(0,0,0),
				meshtmp,
				boost::shared_ptr<TempMesh>()));
		}
		return true;
	} 

	if (meshtmp->IsEmpty()) {
		return false;
	}

	meshtmp->RemoveAdjacentDuplicates();
	meshtmp->RemoveDegenerates();

	if(fix_orientation) {
//		meshtmp->FixupFaceOrientation();
	}

	aiMesh* const mesh = meshtmp->ToMesh();
	if(mesh) {
		mesh->mMaterialIndex = matid; 
		mesh_indices.push_back(conv.meshes.size());
		conv.meshes.push_back(mesh);
		return true;
	}
	return false;
}

// ------------------------------------------------------------------------------------------------
void AssignAddedMeshes(std::vector<unsigned int>& mesh_indices,aiNode* nd,
	ConversionData& /*conv*/)
{
	if (!mesh_indices.empty()) {

		// make unique
		std::sort(mesh_indices.begin(),mesh_indices.end());
		std::vector<unsigned int>::iterator it_end = std::unique(mesh_indices.begin(),mesh_indices.end());

		const size_t size = std::distance(mesh_indices.begin(),it_end);

		nd->mNumMeshes = size;
		nd->mMeshes = new unsigned int[nd->mNumMeshes];
		for(unsigned int i = 0; i < nd->mNumMeshes; ++i) {
			nd->mMeshes[i] = mesh_indices[i];
		}
	}
}

// ------------------------------------------------------------------------------------------------
bool TryQueryMeshCache(const IfcRepresentationItem& item, 
	std::vector<unsigned int>& mesh_indices, unsigned int mat_index,
	ConversionData& conv) 
{
	ConversionData::MeshCacheIndex idx(&item, mat_index);
	ConversionData::MeshCache::const_iterator it = conv.cached_meshes.find(idx);
	if (it != conv.cached_meshes.end()) {
		std::copy((*it).second.begin(),(*it).second.end(),std::back_inserter(mesh_indices));
		return true;
	}
	return false;
}

// ------------------------------------------------------------------------------------------------
void PopulateMeshCache(const IfcRepresentationItem& item, 
	const std::vector<unsigned int>& mesh_indices, unsigned int mat_index,
	ConversionData& conv)
{
	ConversionData::MeshCacheIndex idx(&item, mat_index);
	conv.cached_meshes[idx] = mesh_indices;
}

// ------------------------------------------------------------------------------------------------
bool ProcessRepresentationItem(const IfcRepresentationItem& item, unsigned int matid,
	std::vector<unsigned int>& mesh_indices, 
	ConversionData& conv)
{
	// determine material
	unsigned int localmatid = ProcessMaterials(item.GetID(), matid, conv, true);

	if (!TryQueryMeshCache(item,mesh_indices,localmatid,conv)) {
		if(ProcessGeometricItem(item,localmatid,mesh_indices,conv)) {
			if(mesh_indices.size()) {
				PopulateMeshCache(item,mesh_indices,localmatid,conv);
			}
		}
		else return false;
	}
	return true;
}


} // ! IFC
} // ! Assimp

#endif