mirror of https://github.com/vitalif/openscad
249 lines
9.1 KiB
C++
249 lines
9.1 KiB
C++
#include "polyset-utils.h"
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#include "polyset.h"
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#include "Polygon2d.h"
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#include "printutils.h"
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#include "cgal.h"
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#ifdef NDEBUG
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#define PREV_NDEBUG NDEBUG
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#undef NDEBUG
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#endif
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#include <CGAL/Exact_predicates_inexact_constructions_kernel.h>
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#include <CGAL/Constrained_Delaunay_triangulation_2.h>
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#include <CGAL/Delaunay_mesher_2.h>
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#include <CGAL/Delaunay_mesher_no_edge_refinement_2.h>
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#include <CGAL/Delaunay_mesh_face_base_2.h>
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#include <CGAL/Delaunay_mesh_criteria_2.h>
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#include <CGAL/Mesh_2/Face_badness.h>
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#ifdef PREV_NDEBUG
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#define NDEBUG PREV_NDEBUG
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#endif
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typedef CGAL::Exact_predicates_inexact_constructions_kernel K;
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typedef CGAL::Triangulation_vertex_base_2<K> Vb;
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typedef CGAL::Delaunay_mesh_face_base_2<K> Fb;
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typedef CGAL::Triangulation_data_structure_2<Vb, Fb> Tds;
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typedef CGAL::Constrained_Delaunay_triangulation_2<K, Tds, CGAL::Exact_predicates_tag > CDT;
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//typedef CGAL::Delaunay_mesh_criteria_2<CDT> Criteria;
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typedef CDT::Vertex_handle Vertex_handle;
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typedef CDT::Point CDTPoint;
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template <class T> class DummyCriteria {
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public:
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typedef double Quality;
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class Is_bad {
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public:
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CGAL::Mesh_2::Face_badness operator()(const Quality) const {
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return CGAL::Mesh_2::NOT_BAD;
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}
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CGAL::Mesh_2::Face_badness operator()(const typename T::Face_handle&, Quality&q) const {
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q = 1;
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return CGAL::Mesh_2::NOT_BAD;
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}
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};
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Is_bad is_bad_object() const { return Is_bad(); }
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};
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#include <boost/foreach.hpp>
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namespace PolysetUtils {
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// Project all polygons (also back-facing) into a Polygon2d instance.
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// It's important to select all faces, since filtering by normal vector here
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// will trigger floating point incertainties and cause problems later.
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Polygon2d *project(const PolySet &ps) {
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Polygon2d *poly = new Polygon2d;
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BOOST_FOREACH(const PolySet::Polygon &p, ps.polygons) {
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Outline2d outline;
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BOOST_FOREACH(const Vector3d &v, p) {
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outline.vertices.push_back(Vector2d(v[0], v[1]));
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}
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poly->addOutline(outline);
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}
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return poly;
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}
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/* Tessellation of 3d PolySet faces
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This code is for tessellating the faces of a 3d PolySet, assuming that
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the faces are near-planar polygons.
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We do the tessellation by projecting each polygon of the Polyset onto a
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2-d plane, then running a 2d tessellation algorithm on the projected 2d
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polygon. Then we project each of the newly generated 2d 'tiles' (the
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polygons used for tessellation, typically triangles) back up into 3d
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space.
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(in reality as of writing, we dont need to do a back-projection from 2d->3d
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because the algorithm we are using doesn't create any new points, and we can
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just use a 'map' to associate 3d points with 2d points).
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The code assumes the input polygons are simple, non-intersecting, without
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holes, without duplicate input points, and with proper orientation.
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The purpose of this code is originally to fix github issue 349. Our CGAL
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kernel does not accept polygons for Nef_Polyhedron_3 if each of the
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points is not exactly coplanar. "Near-planar" or "Almost planar" polygons
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often occur due to rounding issues on, for example, polyhedron() input.
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By tessellating the 3d polygon into individual smaller tiles that
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are perfectly coplanar (triangles, for example), we can get CGAL to accept
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the polyhedron() input.
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*/
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typedef enum { XYPLANE, YZPLANE, XZPLANE, NONE } projection_t;
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// this is how we make 3d points appear as though they were 2d points to
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//the tessellation algorithm.
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Vector2d get_projected_point( Vector3d v, projection_t projection ) {
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Vector2d v2(0,0);
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if (projection==XYPLANE) { v2.x() = v.x(); v2.y() = v.y(); }
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else if (projection==XZPLANE) { v2.x() = v.x(); v2.y() = v.z(); }
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else if (projection==YZPLANE) { v2.x() = v.y(); v2.y() = v.z(); }
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return v2;
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}
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CGAL_Point_3 cgp( Vector3d v ) { return CGAL_Point_3( v.x(), v.y(), v.z() ); }
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/* Find a 'good' 2d projection for a given 3d polygon. the XY, YZ, or XZ
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plane. This is needed because near-planar polygons in 3d can have 'bad'
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projections into 2d. For example if the square 0,0,0 0,1,0 0,1,1 0,0,1
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is projected onto the XY plane you will not get a polygon, you wil get
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a skinny line thing. It's better to project that square onto the yz
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plane.*/
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projection_t find_good_projection( PolySet::Polygon pgon ) {
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// step 1 - find 3 non-collinear points in the input
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if (pgon.size()<3) return NONE;
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Vector3d v1,v2,v3;
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v1 = v2 = v3 = pgon[0];
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for (size_t i=0;i<pgon.size();i++) {
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if (pgon[i]!=v1) { v2=pgon[i]; break; }
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}
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if (v1==v2) return NONE;
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for (size_t i=0;i<pgon.size();i++) {
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if (!CGAL::collinear( cgp(v1), cgp(v2), cgp(pgon[i]) )) {
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v3=pgon[i]; break;
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}
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}
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if (CGAL::collinear( cgp(v1), cgp(v2), cgp(v3) ) ) return NONE;
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// step 2 - find which direction is best for projection. planes use
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// the equation ax+by+cz+d = 0. a,b, and c determine the direction the
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// plane is in. we want to find which projection of the 'normal vector'
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// would make the smallest shadow if projected onto the XY, YZ, or XZ
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// plane. 'quadrance' (distance squared) can tell this w/o using sqrt.
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CGAL::Plane_3<CGAL_Kernel3> pl( cgp(v1), cgp(v2), cgp(v3) );
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NT3 qxy = pl.a()*pl.a()+pl.b()*pl.b();
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NT3 qyz = pl.b()*pl.b()+pl.c()*pl.c();
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NT3 qxz = pl.c()*pl.c()+pl.a()*pl.a();
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NT3 min = std::min(qxy,std::min(qyz,qxz));
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if (min==qxy) return XYPLANE;
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else if (min==qyz) return YZPLANE;
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return XZPLANE;
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}
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/* triangulate the given 3d polygon using CGAL's 2d Constrained Delaunay
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algorithm. Project the polygon's points into 2d using the given projection
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before performing the triangulation. This code assumes input polygon is
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simple, no holes, no self-intersections, no duplicate points, and is
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properly oriented. output is a sequence of 3d triangles. */
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bool triangulate_polygon( const PolySet::Polygon &pgon, std::vector<PolySet::Polygon> &triangles, projection_t projection )
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{
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bool err = false;
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CGAL::Failure_behaviour old_behaviour = CGAL::set_error_behaviour(CGAL::THROW_EXCEPTION);
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try {
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CDT cdt;
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std::vector<Vertex_handle> vhandles;
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std::map<CDTPoint,Vector3d> vertmap;
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CGAL::Orientation original_orientation;
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std::vector<CDTPoint> orienpgon;
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for (size_t i = 0; i < pgon.size(); i++) {
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Vector3d v3 = pgon.at(i);
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Vector2d v2 = get_projected_point( v3, projection );
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CDTPoint cdtpoint = CDTPoint(v2.x(),v2.y());
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vertmap[ cdtpoint ] = v3;
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Vertex_handle vh = cdt.insert( cdtpoint );
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vhandles.push_back(vh);
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orienpgon.push_back( cdtpoint );
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}
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original_orientation = CGAL::orientation_2( orienpgon.begin(),orienpgon.end() );
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for (size_t i = 0; i < vhandles.size(); i++ ) {
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int vindex1 = (i+0);
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int vindex2 = (i+1)%vhandles.size();
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cdt.insert_constraint( vhandles[vindex1], vhandles[vindex2] );
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}
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std::list<CDTPoint> list_of_seeds;
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CGAL::refine_Delaunay_mesh_2_without_edge_refinement(cdt,
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list_of_seeds.begin(), list_of_seeds.end(), DummyCriteria<CDT>());
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CDT::Finite_faces_iterator fit;
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for( fit=cdt.finite_faces_begin(); fit!=cdt.finite_faces_end(); fit++ )
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{
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if(fit->is_in_domain()) {
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CDTPoint p1 = cdt.triangle( fit )[0];
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CDTPoint p2 = cdt.triangle( fit )[1];
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CDTPoint p3 = cdt.triangle( fit )[2];
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Vector3d v1 = vertmap[p1];
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Vector3d v2 = vertmap[p2];
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Vector3d v3 = vertmap[p3];
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PolySet::Polygon pgon;
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if (CGAL::orientation(p1,p2,p3)==original_orientation) {
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pgon.push_back(v1);
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pgon.push_back(v2);
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pgon.push_back(v3);
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} else {
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pgon.push_back(v3);
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pgon.push_back(v2);
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pgon.push_back(v1);
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}
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triangles.push_back( pgon );
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}
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}
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} catch (const CGAL::Failure_exception &e) {
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// Using failure exception to catch precondition errors for malformed polygons
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// in e.g. CGAL::orientation_2().
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PRINTB("CGAL error in triangulate_polygon(): %s", e.what());
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err = true;
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}
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CGAL::set_error_behaviour(old_behaviour);
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return err;
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}
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/* Given a 3d PolySet with 'near planar' polygonal faces, Tessellate the
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faces. As of writing, our only tessellation method is Triangulation
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using CGAL's Constrained Delaunay algorithm. This code assumes the input
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polyset has simple polygon faces with no holes, no self intersections, no
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duplicate points, and proper orientation. */
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void tessellate_faces(const PolySet &inps, PolySet &outps) {
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int degeneratePolygons = 0;
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for (size_t i = 0; i < inps.polygons.size(); i++) {
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const PolySet::Polygon pgon = inps.polygons[i];
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if (pgon.size() < 3) {
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degeneratePolygons++;
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continue;
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}
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std::vector<PolySet::Polygon> triangles;
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if (pgon.size() == 3) {
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triangles.push_back(pgon);
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}
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else {
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projection_t goodproj = find_good_projection( pgon );
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if (goodproj==NONE) {
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degeneratePolygons++;
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continue;
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}
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bool err = triangulate_polygon(pgon, triangles, goodproj);
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if (err) continue;
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}
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for (size_t j=0;j<triangles.size();j++) {
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PolySet::Polygon t = triangles[j];
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outps.append_poly();
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outps.append_vertex(t[0].x(),t[0].y(),t[0].z());
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outps.append_vertex(t[1].x(),t[1].y(),t[1].z());
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outps.append_vertex(t[2].x(),t[2].y(),t[2].z());
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}
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}
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if (degeneratePolygons > 0) PRINT("WARNING: PolySet has degenerate polygons");
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}
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}
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