assimp/code/IFCBoolean.cpp

/*
Open Asset Import Library (assimp)
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*/

/** @file  IFCBoolean.cpp
 *  @brief Implements a subset of Ifc boolean operations
 */

#include "AssimpPCH.h"

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

#include <iterator>

namespace Assimp {
	namespace IFC {
		
// ------------------------------------------------------------------------------------------------
enum Intersect {
	Intersect_No,
	Intersect_LiesOnPlane,
	Intersect_Yes
};

// ------------------------------------------------------------------------------------------------
Intersect IntersectSegmentPlane(const IfcVector3& p,const IfcVector3& n, const IfcVector3& e0, 
								const IfcVector3& e1, 
								IfcVector3& out) 
{
	const IfcVector3 pdelta = e0 - p, seg = e1-e0;
	const IfcFloat dotOne = n*seg, dotTwo = -(n*pdelta);

	if (fabs(dotOne) < 1e-6) {
		return fabs(dotTwo) < 1e-6f ? Intersect_LiesOnPlane : Intersect_No;
	}

	const IfcFloat t = dotTwo/dotOne;
	// t must be in [0..1] if the intersection point is within the given segment
	if (t > 1.f || t < 0.f) {
		return Intersect_No;
	}
	out = e0+t*seg;
	return Intersect_Yes;
}

// ------------------------------------------------------------------------------------------------
void ProcessBooleanHalfSpaceDifference(const IfcHalfSpaceSolid* hs, TempMesh& result, 
									   const TempMesh& first_operand, 
									   ConversionData& /*conv*/)
{
	ai_assert(hs != NULL);

	const IfcPlane* const plane = hs->BaseSurface->ToPtr<IfcPlane>();
	if(!plane) {
		IFCImporter::LogError("expected IfcPlane as base surface for the IfcHalfSpaceSolid");
		return;
	}

	// extract plane base position vector and normal vector
	IfcVector3 p,n(0.f,0.f,1.f);
	if (plane->Position->Axis) {
		ConvertDirection(n,plane->Position->Axis.Get());
	}
	ConvertCartesianPoint(p,plane->Position->Location);

	if(!IsTrue(hs->AgreementFlag)) {
		n *= -1.f;
	}

	// clip the current contents of `meshout` against the plane we obtained from the second operand
	const std::vector<IfcVector3>& in = first_operand.verts;
	std::vector<IfcVector3>& outvert = result.verts;

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

	outvert.reserve(in.size());
	result.vertcnt.reserve(first_operand.vertcnt.size());

	unsigned int vidx = 0;
	for(iit = begin; iit != end; vidx += *iit++) {

		unsigned int newcount = 0;
		for(unsigned int i = 0; i < *iit; ++i) {
			const IfcVector3& e0 = in[vidx+i], e1 = in[vidx+(i+1)%*iit];

			// does the next segment intersect the plane?
			IfcVector3 isectpos;
			const Intersect isect = IntersectSegmentPlane(p,n,e0,e1,isectpos);
			if (isect == Intersect_No || isect == Intersect_LiesOnPlane) {
				if ( (e0-p).Normalize()*n > 0 ) {
					outvert.push_back(e0);
					++newcount;
				}
			}
			else if (isect == Intersect_Yes) {
				if ( (e0-p).Normalize()*n > 0 ) {
					// e0 is on the right side, so keep it 
					outvert.push_back(e0);
					outvert.push_back(isectpos);
					newcount += 2;
				}
				else {
					// e0 is on the wrong side, so drop it and keep e1 instead
					outvert.push_back(isectpos);
					++newcount;
				}
			}
		}	

		if (!newcount) {
			continue;
		}

		IfcVector3 vmin,vmax;
		ArrayBounds(&*(outvert.end()-newcount),newcount,vmin,vmax);

		// filter our IfcFloat points - those may happen if a point lies
		// directly on the intersection line. However, due to IfcFloat
		// precision a bitwise comparison is not feasible to detect
		// this case.
		const IfcFloat epsilon = (vmax-vmin).SquareLength() / 1e6f;
		FuzzyVectorCompare fz(epsilon);

		std::vector<IfcVector3>::iterator e = std::unique( outvert.end()-newcount, outvert.end(), fz );

		if (e != outvert.end()) {
			newcount -= static_cast<unsigned int>(std::distance(e,outvert.end()));
			outvert.erase(e,outvert.end());
		}
		if (fz(*( outvert.end()-newcount),outvert.back())) {
			outvert.pop_back();
			--newcount;
		}
		if(newcount > 2) {
			result.vertcnt.push_back(newcount);
		}
		else while(newcount-->0) {
			result.verts.pop_back();
		}

	}
	IFCImporter::LogDebug("generating CSG geometry by plane clipping (IfcBooleanClippingResult)");
}

// ------------------------------------------------------------------------------------------------
// Check if e0-e1 intersects a sub-segment of the given boundary line.
// note: this functions works on 3D vectors, but performs its intersection checks solely in xy.
bool IntersectsBoundaryProfile( const IfcVector3& e0, const IfcVector3& e1, const std::vector<IfcVector3>& boundary,
	std::vector<size_t>& intersected_boundary_segments,
	std::vector<IfcVector3>& intersected_boundary_points,
	bool half_open = false,
	bool* e0_hits_border = NULL)
{
	ai_assert(intersected_boundary_segments.empty());
	ai_assert(intersected_boundary_points.empty());

	if(e0_hits_border) {
		*e0_hits_border = false;
	}

	const IfcVector3& e = e1 - e0;

	for (size_t i = 0, bcount = boundary.size(); i < bcount; ++i) {
		// boundary segment i: b0-b1
		const IfcVector3& b0 = boundary[i];
		const IfcVector3& b1 = boundary[(i+1) % bcount];

		const IfcVector3& b = b1 - b0;

		// segment-segment intersection
		// solve b0 + b*s = e0 + e*t for (s,t)
		const IfcFloat det = (-b.x * e.y + e.x * b.y);
		if(fabs(det) < 1e-6) {
			// no solutions (parallel lines)
			continue;
		}

		const IfcFloat x = b0.x - e0.x;
		const IfcFloat y = b0.y - e0.y;

		const IfcFloat s = (x*e.y - e.x*y)/det;
		const IfcFloat t = (x*b.y - b.x*y)/det;

#ifdef ASSIMP_BUILD_DEBUG
		const IfcVector3 check = b0 + b*s  - (e0 + e*t);
		ai_assert((IfcVector2(check.x,check.y)).SquareLength() < 1e-5);
#endif

		// for a valid intersection, s-t should be in range [0,1].
		// note that for t (i.e. the segment point) we only use a
		// half-sided epsilon because the next segment should catch
		// this case.
		const IfcFloat epsilon = 1e-6;
		if (t >= -epsilon && (t <= 1.0+epsilon || half_open) && s >= -epsilon && s <= 1.0) {

			if (e0_hits_border && !*e0_hits_border) {
				*e0_hits_border = fabs(t) < 1e-5f;
			}
	
			const IfcVector3& p = e0 + e*t;

			// only insert the point into the list if it is sufficiently
			// far away from the previous intersection point. This way,
			// we avoid duplicate detection if the intersection is
			// directly on the vertex between two segments.
			if (!intersected_boundary_points.empty() && intersected_boundary_segments.back()==i-1 ) {
				const IfcVector3 diff = intersected_boundary_points.back() - p;
				if(IfcVector2(diff.x, diff.y).SquareLength() < 1e-7) {
					continue;
				}
			}
			intersected_boundary_segments.push_back(i);
			intersected_boundary_points.push_back(p);
		}
	}

	return !intersected_boundary_segments.empty();
}


// ------------------------------------------------------------------------------------------------
// note: this functions works on 3D vectors, but performs its intersection checks solely in xy.
bool PointInPoly(const IfcVector3& p, const std::vector<IfcVector3>& boundary)
{
	// even-odd algorithm: take a random vector that extends from p to infinite
	// and counts how many times it intersects edges of the boundary.
	// because checking for segment intersections is prone to numeric inaccuracies
	// or double detections (i.e. when hitting multiple adjacent segments at their
	// shared vertices) we do it thrice with different rays and vote on it.

	// the even-odd algorithm doesn't work for points which lie directly on
	// the border of the polygon. If any of our attempts produces this result,
	// we return false immediately.

	std::vector<size_t> intersected_boundary_segments;
	std::vector<IfcVector3> intersected_boundary_points;
	size_t votes = 0;

	bool is_border;
	IntersectsBoundaryProfile(p, p + IfcVector3(1.0,0,0), boundary, 
		intersected_boundary_segments, 
		intersected_boundary_points, true, &is_border);

	if(is_border) {
		return false;
	}

	votes += intersected_boundary_segments.size() % 2;

	intersected_boundary_segments.clear();
	intersected_boundary_points.clear();

	IntersectsBoundaryProfile(p, p + IfcVector3(0,1.0,0), boundary, 
		intersected_boundary_segments, 
		intersected_boundary_points, true, &is_border);

	if(is_border) {
		return false;
	}

	votes += intersected_boundary_segments.size() % 2;

	intersected_boundary_segments.clear();
	intersected_boundary_points.clear();

	IntersectsBoundaryProfile(p, p + IfcVector3(0.6,-0.6,0.0), boundary, 
		intersected_boundary_segments, 
		intersected_boundary_points, true, &is_border);

	if(is_border) {
		return false;
	}

	votes += intersected_boundary_segments.size() % 2;
	//ai_assert(votes == 3 || votes == 0);
	return votes > 1;
}


// ------------------------------------------------------------------------------------------------
void ProcessPolygonalBoundedBooleanHalfSpaceDifference(const IfcPolygonalBoundedHalfSpace* hs, TempMesh& result, 
													   const TempMesh& first_operand, 
													   ConversionData& conv)
{
	ai_assert(hs != NULL);

	const IfcPlane* const plane = hs->BaseSurface->ToPtr<IfcPlane>();
	if(!plane) {
		IFCImporter::LogError("expected IfcPlane as base surface for the IfcHalfSpaceSolid");
		return;
	}

	// extract plane base position vector and normal vector
	IfcVector3 p,n(0.f,0.f,1.f);
	if (plane->Position->Axis) {
		ConvertDirection(n,plane->Position->Axis.Get());
	}
	ConvertCartesianPoint(p,plane->Position->Location);

	if(!IsTrue(hs->AgreementFlag)) {
		n *= -1.f;
	}

	n.Normalize();

	// obtain the polygonal bounding volume
	boost::shared_ptr<TempMesh> profile = boost::shared_ptr<TempMesh>(new TempMesh());
	if(!ProcessCurve(hs->PolygonalBoundary, *profile.get(), conv)) {
		IFCImporter::LogError("expected valid polyline for boundary of boolean halfspace");
		return;
	}

	IfcMatrix4 proj_inv;
	ConvertAxisPlacement(proj_inv,hs->Position);

	// and map everything into a plane coordinate space so all intersection
	// tests can be done in 2D space.
	IfcMatrix4 proj = proj_inv;
	proj.Inverse();

	// clip the current contents of `meshout` against the plane we obtained from the second operand
	const std::vector<IfcVector3>& in = first_operand.verts;
	std::vector<IfcVector3>& outvert = result.verts;

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

	outvert.reserve(in.size());
	result.vertcnt.reserve(first_operand.vertcnt.size());

	std::vector<size_t> intersected_boundary_segments;
	std::vector<IfcVector3> intersected_boundary_points;

	// TODO: the following algorithm doesn't handle all cases. 
	unsigned int vidx = 0;
	for(iit = begin; iit != end; vidx += *iit++) {
		if (!*iit) {
			continue;
		}

		unsigned int newcount = 0;
		bool was_outside_boundary = !PointInPoly(proj * in[vidx], profile->verts);

		// used any more?
		//size_t last_intersected_boundary_segment;
		IfcVector3 last_intersected_boundary_point;

		bool extra_point_flag = false;
		IfcVector3 extra_point;

		IfcVector3 enter_volume;
		bool entered_volume_flag = false;

		for(unsigned int i = 0; i < *iit; ++i) {
			// current segment: [i,i+1 mod size] or [*extra_point,i] if extra_point_flag is set
			const IfcVector3& e0 = extra_point_flag ? extra_point : in[vidx+i];
			const IfcVector3& e1 = extra_point_flag ? in[vidx+i] : in[vidx+(i+1)%*iit];

			// does the current segment intersect the polygonal boundary?
			const IfcVector3& e0_plane = proj * e0;
			const IfcVector3& e1_plane = proj * e1;

			intersected_boundary_segments.clear();
			intersected_boundary_points.clear();

			const bool is_outside_boundary = !PointInPoly(e1_plane, profile->verts);
			const bool is_boundary_intersection = is_outside_boundary != was_outside_boundary;
			
			IntersectsBoundaryProfile(e0_plane, e1_plane, profile->verts, 
				intersected_boundary_segments, 
				intersected_boundary_points);
		
			ai_assert(!is_boundary_intersection || !intersected_boundary_segments.empty());

			// does the current segment intersect the plane?
			// (no extra check if this is an extra point)
			IfcVector3 isectpos;
			const Intersect isect =  extra_point_flag ? Intersect_No : IntersectSegmentPlane(p,n,e0,e1,isectpos);

#ifdef ASSIMP_BUILD_DEBUG
			if (isect == Intersect_Yes) {
				const IfcFloat f = fabs((isectpos - p)*n);
				ai_assert(f < 1e-5);
			}
#endif

			const bool is_white_side = (e0-p)*n >= -1e-6;

			// e0 on good side of plane? (i.e. we should keep all geometry on this side)
			if (is_white_side) {
				// but is there an intersection in e0-e1 and is e1 in the clipping
				// boundary? In this case, generate a line that only goes to the
				// intersection point.
				if (isect == Intersect_Yes  && !is_outside_boundary) {
					outvert.push_back(e0);
					++newcount;

					outvert.push_back(isectpos);
					++newcount;
					
					/*
					// this is, however, only a line that goes to the plane, but not
					// necessarily to the point where the bounding volume on the
					// black side of the plane is hit. So basically, we need another 
					// check for [isectpos-e1], which should yield an intersection
					// point.
					extra_point_flag = true;
					extra_point = isectpos;

					was_outside_boundary = true; 
					continue; */

					// [isectpos, enter_volume] potentially needs extra points.
					// For this, we determine the intersection point with the
					// bounding volume and project it onto the plane. 
					/*
					const IfcVector3& enter_volume_proj = proj * enter_volume;
					const IfcVector3& enter_isectpos = proj * isectpos;

					intersected_boundary_segments.clear();
					intersected_boundary_points.clear();

					IntersectsBoundaryProfile(enter_volume_proj, enter_isectpos, profile->verts, 
						intersected_boundary_segments, 
						intersected_boundary_points);

					if(!intersected_boundary_segments.empty()) {

						vec = vec + ((p - vec) * n) * n;
					}
					*/				

					//entered_volume_flag = true;
				}
				else {
					outvert.push_back(e0);
					++newcount;
				}
			}
			// e0 on bad side of plane, e1 on good (i.e. we should remove geometry on this side,
			// but only if it is within the bounding volume).
			else if (isect == Intersect_Yes) {
				// is e0 within the clipping volume? Insert the intersection point
				// of [e0,e1] and the plane instead of e0.
				if(was_outside_boundary) {
					outvert.push_back(e0);
				}
				else {
					if(entered_volume_flag) {
						const IfcVector3& fix_point = enter_volume + ((p - enter_volume) * n) * n;
						outvert.push_back(fix_point);
						++newcount;
					}

					outvert.push_back(isectpos);	
				}
				entered_volume_flag = false;
				++newcount;
			}
			else { // no intersection with plane or parallel; e0,e1 are on the bad side
			
				// did we just pass the boundary line to the poly bounding?
				if (is_boundary_intersection) {

					// and are now outside the clipping boundary?
					if (is_outside_boundary) {
						// in this case, get the point where the clipping boundary
						// was entered first. Then, get the point where the clipping
						// boundary volume was left! These two points with the plane
						// normal form another plane that intersects the clipping
						// volume. There are two ways to get from the first to the
						// second point along the intersection curve, try to pick the
						// one that lies within the current polygon.

						// TODO this approach doesn't handle all cases

						// ...

						IfcFloat d = 1e20;
						IfcVector3 vclosest;
						BOOST_FOREACH(const IfcVector3& v, intersected_boundary_points) {
							const IfcFloat dn = (v-e1_plane).SquareLength();
							if (dn < d) {
								d = dn;
								vclosest = v;
							}
						}

						vclosest = proj_inv * vclosest;
						if(entered_volume_flag) {
							const IfcVector3& fix_point = vclosest + ((p - vclosest) * n) * n;
							outvert.push_back(fix_point);
							++newcount;

							entered_volume_flag = false;
						}

						outvert.push_back(vclosest);
						++newcount;

						//outvert.push_back(e1);
						//++newcount;
					}
					else {
						entered_volume_flag = true;

						// we just entered the clipping boundary. Record the point
						// and the segment where we entered and also generate this point.
						//last_intersected_boundary_segment = intersected_boundary_segments.front();
						//last_intersected_boundary_point = intersected_boundary_points.front();

						outvert.push_back(e0);
						++newcount;

						IfcFloat d = 1e20;
						IfcVector3 vclosest;
						BOOST_FOREACH(const IfcVector3& v, intersected_boundary_points) {
							const IfcFloat dn = (v-e0_plane).SquareLength();
							if (dn < d) {
								d = dn;
								vclosest = v;
							}
						}

						enter_volume = proj_inv * vclosest;
						outvert.push_back(enter_volume);
						++newcount;
					}
				}				
				// if not, we just keep the vertex
				else if (is_outside_boundary) {
					outvert.push_back(e0);
					++newcount;

					entered_volume_flag = false;
				}
			}

			was_outside_boundary = is_outside_boundary;
			extra_point_flag = false;
		}
	
		if (!newcount) {
			continue;
		}
		
		IfcVector3 vmin,vmax;
		ArrayBounds(&*(outvert.end()-newcount),newcount,vmin,vmax);

		// filter our IfcFloat points - those may happen if a point lies
		// directly on the intersection line. However, due to IfcFloat
		// precision a bitwise comparison is not feasible to detect
		// this case.
		const IfcFloat epsilon = (vmax-vmin).SquareLength() / 1e6f;
		FuzzyVectorCompare fz(epsilon);

		std::vector<IfcVector3>::iterator e = std::unique( outvert.end()-newcount, outvert.end(), fz );

		if (e != outvert.end()) {
			newcount -= static_cast<unsigned int>(std::distance(e,outvert.end()));
			outvert.erase(e,outvert.end());
		}
		if (fz(*( outvert.end()-newcount),outvert.back())) {
			outvert.pop_back();
			--newcount;
		} 
		if(newcount > 2) {
			result.vertcnt.push_back(newcount);
		}
		else while(newcount-->0) {
			result.verts.pop_back();
		}

	}
	IFCImporter::LogDebug("generating CSG geometry by plane clipping with polygonal bounding (IfcBooleanClippingResult)");	
}

// ------------------------------------------------------------------------------------------------
void ProcessBooleanExtrudedAreaSolidDifference(const IfcExtrudedAreaSolid* as, TempMesh& result, 
											   const TempMesh& first_operand, 
											   ConversionData& conv)
{
	ai_assert(as != NULL);

	// This case is handled by reduction to an instance of the quadrify() algorithm.
	// Obviously, this won't work for arbitrarily complex cases. In fact, the first
	// operand should be near-planar. Luckily, this is usually the case in Ifc 
	// buildings.

	boost::shared_ptr<TempMesh> meshtmp = boost::shared_ptr<TempMesh>(new TempMesh());
	ProcessExtrudedAreaSolid(*as,*meshtmp,conv,false);

	std::vector<TempOpening> openings(1, TempOpening(as,IfcVector3(0,0,0),meshtmp,boost::shared_ptr<TempMesh>()));

	result = first_operand;

	TempMesh temp;

	std::vector<IfcVector3>::const_iterator vit = first_operand.verts.begin();
	BOOST_FOREACH(unsigned int pcount, first_operand.vertcnt) {
		temp.Clear();

		temp.verts.insert(temp.verts.end(), vit, vit + pcount);
		temp.vertcnt.push_back(pcount);

		// The algorithms used to generate mesh geometry sometimes
		// spit out lines or other degenerates which must be
		// filtered to avoid running into assertions later on.

		// ComputePolygonNormal returns the Newell normal, so the
		// length of the normal is the area of the polygon.
		const IfcVector3& normal = temp.ComputeLastPolygonNormal(false);
		if (normal.SquareLength() < static_cast<IfcFloat>(1e-5)) {
			IFCImporter::LogWarn("skipping degenerate polygon (ProcessBooleanExtrudedAreaSolidDifference)");
			continue;
		}

		GenerateOpenings(openings, std::vector<IfcVector3>(1,IfcVector3(1,0,0)), temp, false, true);
		result.Append(temp);

		vit += pcount;
	}

	IFCImporter::LogDebug("generating CSG geometry by geometric difference to a solid (IfcExtrudedAreaSolid)");
}

// ------------------------------------------------------------------------------------------------
void ProcessBoolean(const IfcBooleanResult& boolean, TempMesh& result, ConversionData& conv)
{
	// supported CSG operations:
	//   DIFFERENCE
	if(const IfcBooleanResult* const clip = boolean.ToPtr<IfcBooleanResult>()) {
		if(clip->Operator != "DIFFERENCE") {
			IFCImporter::LogWarn("encountered unsupported boolean operator: " + (std::string)clip->Operator);
			return;
		}

		// supported cases (1st operand):
		//  IfcBooleanResult -- call ProcessBoolean recursively
		//  IfcSweptAreaSolid -- obtain polygonal geometry first

		// supported cases (2nd operand):
		//  IfcHalfSpaceSolid -- easy, clip against plane
		//  IfcExtrudedAreaSolid -- reduce to an instance of the quadrify() algorithm


		const IfcHalfSpaceSolid* const hs = clip->SecondOperand->ResolveSelectPtr<IfcHalfSpaceSolid>(conv.db);
		const IfcExtrudedAreaSolid* const as = clip->SecondOperand->ResolveSelectPtr<IfcExtrudedAreaSolid>(conv.db);
		if(!hs && !as) {
			IFCImporter::LogError("expected IfcHalfSpaceSolid or IfcExtrudedAreaSolid as second clipping operand");
			return;
		}

		TempMesh first_operand;
		if(const IfcBooleanResult* const op0 = clip->FirstOperand->ResolveSelectPtr<IfcBooleanResult>(conv.db)) {
			ProcessBoolean(*op0,first_operand,conv);
		}
		else if (const IfcSweptAreaSolid* const swept = clip->FirstOperand->ResolveSelectPtr<IfcSweptAreaSolid>(conv.db)) {
			ProcessSweptAreaSolid(*swept,first_operand,conv);
		}
		else {
			IFCImporter::LogError("expected IfcSweptAreaSolid or IfcBooleanResult as first clipping operand");
			return;
		}

		if(hs) {

			const IfcPolygonalBoundedHalfSpace* const hs_bounded = clip->SecondOperand->ResolveSelectPtr<IfcPolygonalBoundedHalfSpace>(conv.db);
			if (hs_bounded) {
				ProcessPolygonalBoundedBooleanHalfSpaceDifference(hs_bounded, result, first_operand, conv);
			}
			else {
				ProcessBooleanHalfSpaceDifference(hs, result, first_operand, conv);
			}
		}
		else {
			ProcessBooleanExtrudedAreaSolidDifference(as, result, first_operand, conv);
		}
	}
	else {
		IFCImporter::LogWarn("skipping unknown IfcBooleanResult entity, type is " + boolean.GetClassName());
	}
}

} // ! IFC
} // ! Assimp

#endif