godot/core/math/quick_hull.cpp

/*************************************************************************/
/*  quick_hull.cpp                                                       */
/*************************************************************************/
/*                       This file is part of:                           */
/*                           GODOT ENGINE                                */
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/* Copyright (c) 2007-2017 Juan Linietsky, Ariel Manzur.                 */
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#include "quick_hull.h"
#include "map.h"

uint32_t QuickHull::debug_stop_after=0xFFFFFFFF;

Error QuickHull::build(const Vector<Vector3>& p_points, Geometry::MeshData &r_mesh) {


	static const real_t over_tolerance = 0.0001;

	/* CREATE AABB VOLUME */

	AABB aabb;
	for(int i=0;i<p_points.size();i++) {

		if (i==0) {
			aabb.pos=p_points[i];
		} else {
			aabb.expand_to(p_points[i]);
		}
	}


	if (aabb.size==Vector3()) {
		return ERR_CANT_CREATE;
	}


	Vector<bool> valid_points;
	valid_points.resize(p_points.size());
	Set<Vector3> valid_cache;

	for(int i=0;i<p_points.size();i++) {

		Vector3 sp = p_points[i].snapped(0.0001);
		if (valid_cache.has(sp)) {
			valid_points[i]=false;
			//print_line("INVALIDATED: "+itos(i));
		}else {
			valid_points[i]=true;
			valid_cache.insert(sp);
		}
	}



	/* CREATE INITIAL SIMPLEX */

	int longest_axis = aabb.get_longest_axis_index();

	//first two vertices are the most distant
	int simplex[4];

	{
		real_t max,min;

		for(int i=0;i<p_points.size();i++) {

			if (!valid_points[i])
				continue;
			float d = p_points[i][longest_axis];
			if (i==0 || d < min) {

				simplex[0]=i;
				min=d;
			}

			if (i==0 || d > max) {
				simplex[1]=i;
				max=d;
			}

		}
	}

	//third vertex is one most further away from the line


	{
		float maxd;
		Vector3 rel12 =  p_points[simplex[0]] - p_points[simplex[1]];

		for(int i=0;i<p_points.size();i++) {

			if (!valid_points[i])
				continue;

			Vector3 n = rel12.cross(p_points[simplex[0]]-p_points[i]).cross(rel12).normalized();
			real_t d = Math::abs(n.dot(p_points[simplex[0]])-n.dot(p_points[i]));

			if (i==0 || d>maxd) {

				maxd=d;
				simplex[2]=i;
			}
		}
	}

	//fourth vertex is the one  most further away from the plane

	{
		float maxd;
		Plane p(p_points[simplex[0]],p_points[simplex[1]],p_points[simplex[2]]);

		for(int i=0;i<p_points.size();i++) {

			if (!valid_points[i])
				continue;

			real_t d = Math::abs(p.distance_to(p_points[i]));

			if (i==0 || d>maxd) {

				maxd=d;
				simplex[3]=i;
			}
		}
	}


	//compute center of simplex, this is a point always warranted to be inside
	Vector3 center;

	for(int i=0;i<4;i++) {
		center+=p_points[simplex[i]];
	}

	center/=4.0;

	//add faces

	List<Face> faces;

	for(int i=0;i<4;i++) {

		static const int face_order[4][3]={
			{0,1,2},
			{0,1,3},
			{0,2,3},
			{1,2,3}
		};

		Face f;
		for(int j=0;j<3;j++) {
			f.vertices[j]=simplex[face_order[i][j]];
		}


		Plane p(p_points[f.vertices[0]],p_points[f.vertices[1]],p_points[f.vertices[2]]);

		if (p.is_point_over(center)) {
			//flip face to clockwise if facing inwards
			SWAP( f.vertices[0], f.vertices[1] );
			p=-p;
		}


		f.plane = p;

		faces.push_back(f);

	}


	/* COMPUTE AVAILABLE VERTICES */

	for(int i=0;i<p_points.size();i++) {

		if (i==simplex[0])
			continue;
		if (i==simplex[1])
			continue;
		if (i==simplex[2])
			continue;
		if (i==simplex[3])
			continue;
		if (!valid_points[i])
			continue;

		for(List<Face>::Element *E=faces.front();E;E=E->next()) {

			if (E->get().plane.distance_to(p_points[i]) > over_tolerance ) {

				E->get().points_over.push_back(i);
				break;
			}
		}



	}

	faces.sort(); // sort them, so the ones with points are in the back


	/* BUILD HULL */


	//poop face (while still remain)
	//find further away point
	//find lit faces
	//determine horizon edges
	//build new faces with horizon edges, them assign points side from all lit faces
	//remove lit faces


	uint32_t debug_stop = debug_stop_after;

	while(debug_stop>0 && faces.back()->get().points_over.size()) {

		debug_stop--;
		Face& f = faces.back()->get();

		//find vertex most outside
		int next=-1;
		real_t next_d=0;

		for(int i=0;i<f.points_over.size();i++) {

			real_t d = f.plane.distance_to(p_points[f.points_over[i]]);

			if (d > next_d) {
				next_d=d;
				next=i;
			}
		}

		ERR_FAIL_COND_V(next==-1,ERR_BUG);



		Vector3 v = p_points[f.points_over[next]];

		//find lit faces and lit edges
		List< List<Face>::Element* > lit_faces; //lit face is a death sentence

		Map<Edge,FaceConnect> lit_edges; //create this on the flight, should not be that bad for performance and simplifies code a lot

		for(List<Face>::Element *E=faces.front();E;E=E->next()) {

			if (E->get().plane.distance_to(v) >0 ) {

				lit_faces.push_back(E);

				for(int i=0;i<3;i++) {
					uint32_t a = E->get().vertices[i];
					uint32_t b = E->get().vertices[(i+1)%3];
					Edge e(a,b);

					Map<Edge,FaceConnect>::Element *F=lit_edges.find(e);
					if (!F) {
						F=lit_edges.insert(e,FaceConnect());
					}
					if (e.vertices[0]==a) {
						//left
						F->get().left=E;
					} else {

						F->get().right=E;
					}
				}
			}
		}


		//create new faces from horizon edges
		List< List<Face>::Element* > new_faces; //new faces

		for(Map<Edge,FaceConnect>::Element *E=lit_edges.front();E;E=E->next()) {

			FaceConnect& fc = E->get();
			if (fc.left && fc.right) {
				continue; //edge is uninteresting, not on horizont
			}

			//create new face!

			Face face;
			face.vertices[0]=f.points_over[next];
			face.vertices[1]=E->key().vertices[0];
			face.vertices[2]=E->key().vertices[1];

			Plane p(p_points[face.vertices[0]],p_points[face.vertices[1]],p_points[face.vertices[2]]);

			if (p.is_point_over(center)) {
				//flip face to clockwise if facing inwards
				SWAP( face.vertices[0], face.vertices[1] );
				p = -p;
			}

			face.plane = p;
			new_faces.push_back( faces.push_back(face) );
		}

		//distribute points into new faces

		for(List< List<Face>::Element* >::Element *F=lit_faces.front();F;F=F->next()) {

			Face &lf = F->get()->get();

			for(int i=0;i<lf.points_over.size();i++) {

				if (lf.points_over[i]==f.points_over[next]) //do not add current one
					continue;

				Vector3 p = p_points[lf.points_over[i]];
				for (List< List<Face>::Element* >::Element *E=new_faces.front();E;E=E->next()) {

					Face &f2 = E->get()->get();
					if (f2.plane.distance_to(p)>over_tolerance) {
						f2.points_over.push_back(lf.points_over[i]);
						break;
					}
				}


			}
		}

		//erase lit faces

		while(lit_faces.size()) {

			faces.erase(lit_faces.front()->get());
			lit_faces.pop_front();
		}

		//put faces that contain no points on the front

		for (List< List<Face>::Element* >::Element *E=new_faces.front();E;E=E->next()) {

			Face &f2 = E->get()->get();
			if (f2.points_over.size()==0) {
				faces.move_to_front(E->get());
			}
		}

		//whew, done with iteration, go next



	}

	/* CREATE MESHDATA */


	//make a map of edges again
	Map<Edge,RetFaceConnect> ret_edges;
	List<Geometry::MeshData::Face> ret_faces;


	for(List<Face>::Element *E=faces.front();E;E=E->next()) {

		Geometry::MeshData::Face f;
		f.plane = E->get().plane;



		for(int i=0;i<3;i++) {
			f.indices.push_back(E->get().vertices[i]);
		}

		List<Geometry::MeshData::Face>::Element *F = ret_faces.push_back(f);

		for(int i=0;i<3;i++) {

			uint32_t a = E->get().vertices[i];
			uint32_t b = E->get().vertices[(i+1)%3];
			Edge e(a,b);

			Map<Edge,RetFaceConnect>::Element *G=ret_edges.find(e);
			if (!G) {
				G=ret_edges.insert(e,RetFaceConnect());
			}
			if (e.vertices[0]==a) {
				//left
				G->get().left=F;
			} else {

				G->get().right=F;
			}
		}
	}

	//fill faces

	for (List<Geometry::MeshData::Face>::Element *E=ret_faces.front();E;E=E->next()) {

		Geometry::MeshData::Face& f = E->get();

		for(int i=0;i<f.indices.size();i++) {

			uint32_t a = E->get().indices[i];
			uint32_t b = E->get().indices[(i+1)%f.indices.size()];
			Edge e(a,b);

			Map<Edge,RetFaceConnect>::Element *F=ret_edges.find(e);

			ERR_CONTINUE(!F);

			List<Geometry::MeshData::Face>::Element *O = F->get().left == E ? F->get().right : F->get().left;
			ERR_CONTINUE(O==E);
			ERR_CONTINUE(O==NULL);

			if (O->get().plane.is_almost_like(f.plane)) {
				//merge and delete edge and contiguous face, while repointing edges (uuugh!)
				int ois = O->get().indices.size();
				int merged=0;


				for(int j=0;j<ois;j++) {
					//search a
					if (O->get().indices[j]==a) {
						//append the rest
						for(int k=0;k<ois;k++) {

							int idx = O->get().indices[(k+j)%ois];
							int idxn = O->get().indices[(k+j+1)%ois];
							if (idx==b && idxn==a) {//already have b!
								break;
							}
							if (idx!=a) {
								f.indices.insert(i+1,idx);
								i++;
								merged++;
							}
							Edge e2(idx,idxn);

							Map<Edge,RetFaceConnect>::Element *F2=ret_edges.find(e2);

							ERR_CONTINUE(!F2);
							//change faceconnect, point to this face instead
							if (F2->get().left == O)
								F2->get().left=E;
							else if (F2->get().right == O)
								F2->get().right=E;

						}

						break;
					}
				}


				ret_edges.erase(F); //remove the edge
				ret_faces.erase(O); //remove the face


			}

		}

	}

	//fill mesh
	r_mesh.faces.clear();
	r_mesh.faces.resize(ret_faces.size());
//	print_line("FACECOUNT: "+itos(r_mesh.faces.size()));

	int idx=0;
	for (List<Geometry::MeshData::Face>::Element *E=ret_faces.front();E;E=E->next()) {
		r_mesh.faces[idx++]=E->get();


	}
	r_mesh.edges.resize(ret_edges.size());
	idx=0;
	for(Map<Edge,RetFaceConnect>::Element *E=ret_edges.front();E;E=E->next()) {

		Geometry::MeshData::Edge e;
		e.a=E->key().vertices[0];
		e.b=E->key().vertices[1];
		r_mesh.edges[idx++]=e;
	}

	r_mesh.vertices=p_points;

	//r_mesh.optimize_vertices();
/*
	print_line("FACES: "+itos(r_mesh.faces.size()));
	print_line("EDGES: "+itos(r_mesh.edges.size()));
	print_line("VERTICES: "+itos(r_mesh.vertices.size()));
*/

	return OK;
}