CGAL users discussion list

["Rasal Raj, Anish" <>]

Hello Guys,

I have recently started working with CGAL. I have a doubt.

I am using CGAL intersection operation on a list of triangles. currently, it takes some time to complete the information. What are the possible ways to improve the execution time?

Note: the list of triangles contains around 25k triangles. I have attached a sample code with this e-mail. I am using Exact_predicates_exact_constructions_kernel kernel.

typedef CGAL::Exact_predicates_exact_constructions_kernel Kernel;
typedef Kernel::Point_3 Point;
typedef Kernel::Segment_3 Segment_3;
typedef Kernel::Triangle_3  Triangle;
typedef CGAL::Cartesian<double> tc;


struct Ternion
{
	Triangle triangle;
	int unique_id;
	std::list<Segment_3> intersection_lines;	
}

void cgal_intersect(std::list<Ternion> &list_of_ternions)
{
      
	for(auto &i : list_of_ternions)
	{
		for (auto &j : list_of_ternions)
		{
			if(i.unique_id == j.unique_id) continue;
			
			if(CGAL::do_intersect(i.triangle, j.triangle))
			{


				CGAL::cpp11::result_of<Kernel::Intersect_3(Triangle, Triangle)>::type result;
				result = CGAL::intersection(i.triangle, j.triangle);

				if (result) 
				{
					if (Segment_3* s = boost::get<Segment_3>(&*result))
					{
						Segment_3 seg = *s;
						Point P1(seg.vertex(0).x(), seg.vertex(0).y(), seg.vertex(0).z());
						Point P2(seg.vertex(1).x(), seg.vertex(1).y(), seg.vertex(1).z());
						
						i.intersecting_lines.emplace_back(P1, P2);
						j.intersecting_lines.emplace_back(P1, P2);
					}
					else if (Triangle* t = boost::get<Triangle>(&*result)) 
					{
						Triangle tri = *t;
						Point P1(tri.vertex(0).x(), tri.vertex(0).y(), tri.vertex(0).z());
						Point P2(tri.vertex(1).x(), tri.vertex(1).y(), tri.vertex(1).z());
						Point P3(tri.vertex(2).x(), tri.vertex(2).y(), tri.vertex(2).z());


						auto dist = CGAL::squared_distance(P1, P2);
						if (CGAL::to_double(dist) >= (25e-14)) {
							i.intersecting_lines.emplace_back(P1, P2);
							j.intersecting_lines.emplace_back(P1, P2);
						}
						
						auto dist1 = CGAL::squared_distance(P2, P3);
						if (CGAL::to_double(dist1) >= (25e-14)) {
							i.intersecting_lines.emplace_back(P2, P3);
							j.intersecting_lines.emplace_back(P2, P3);
						}
						
						auto dist2 = CGAL::squared_distance(P1,P3);
						if (CGAL::to_double(dist2) >= (25e-14)) {
							i.intersecting_lines.emplace_back(P3, P1);
							j.intersecting_lines.emplace_back(P3, P1);
						}
					}
					else if (boost::get<std::vector <Point>>(&*result))
					{
						std::cout << "[WARNING] vector of points, unhandles" << std::endl;
					}
					else if (boost::get<Point>(&*result))
					{
						std::cout << "[WARNING] point intersection, unhandled " << std::endl;
					}
					else
					{
						std::cout << "[WARNING] Unknown intersection, unhandled " << std::endl;
					}

				}
			}
		}
	}
}