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生成的DSM被用作DTM计算的基础#xff0c;即地面表示为过滤掉非地面点后的另一个TIN。主要是去除一些建筑物和植被非地形点。
建筑物立面及连通区域提取
建筑物立面的特征是三角形面片的高度变化剧烈。 通过遍历每一个三角面片#xff0c;…CGAL 从DSM到DTM-建筑物区域提取
生成的DSM被用作DTM计算的基础即地面表示为过滤掉非地面点后的另一个TIN。主要是去除一些建筑物和植被非地形点。
建筑物立面及连通区域提取
建筑物立面的特征是三角形面片的高度变化剧烈。 通过遍历每一个三角面片计算顶点之间最大的高差face_height与事先设置的阈值spacing比较大于阈值或包含无限远点infinite_vertex标记为建筑物立面。
除去建筑物立面对剩下的三角面片使用洪水算法确定连通区域并标记对应的区域id取值范围[0component_size.size()]。
代码
#includeiostream#includeCGAL/Surface_mesh.h
#includeCGAL/Surface_mesh/IO/PLY.h#include CGAL/Exact_predicates_inexact_constructions_kernel.h
#include CGAL/Projection_traits_xy_3.h
#include CGAL/Delaunay_triangulation_2.h
#include CGAL/Triangulation_vertex_base_with_info_2.h
#include CGAL/Triangulation_face_base_with_info_2.h#include CGAL/boost/graph/graph_traits_Delaunay_triangulation_2.h
#include CGAL/boost/graph/copy_face_graph.h#include CGAL/compute_average_spacing.husing Kernel CGAL::Exact_predicates_inexact_constructions_kernel;using Projection_traits CGAL::Projection_traits_xy_3Kernel;using Point_3 Kernel::Point_3;
using Mesh CGAL::Surface_meshPoint_3;using Concurrency_tag CGAL::Sequential_tag;using Vbi CGAL::Triangulation_vertex_base_with_info_2 Mesh::Vertex_index, Projection_traits;
using Fbi CGAL::Triangulation_face_base_with_info_2int, Projection_traits;
using TDS CGAL::Triangulation_data_structure_2Vbi, Fbi;
using TIN_with_info CGAL::Delaunay_triangulation_2Projection_traits, TDS;int main() {Mesh mesh;CGAL::IO::read_PLY(./data/dsm.ply, mesh);auto idx_to_point_with_info [](const Mesh::Vertex_index idx) - std::pairPoint_3, Mesh::Vertex_index{return std::make_pair ( mesh.point(idx), idx);};TIN_with_info tin_with_info(boost::make_transform_iterator (mesh.vertices().begin(), idx_to_point_with_info),boost::make_transform_iterator (mesh.vertices().end(), idx_to_point_with_info));double spacing CGAL::compute_average_spacingConcurrency_tag(mesh.points(), 6);spacing * 2;auto face_height [](const TIN_with_info::Face_handle fh) - double{double out 0.;for (int i 0; i 3; i)out (std::max) (out, CGAL::abs(fh-vertex(i)-point().z() - fh-vertex((i1)%3)-point().z()));return out;};// Initialize faces info 初始化三角面附件信息int类型for (TIN_with_info::Face_handle fh : tin_with_info.all_face_handles())if (tin_with_info.is_infinite(fh) || face_height(fh) spacing) // Filtered faces are given info() -2fh-info() -2;else // Pending faces are given info() -1;fh-info() -1;// Flooding algorithmstd::vectorint component_size;for (TIN_with_info::Face_handle fh : tin_with_info.finite_face_handles()){if (fh-info() ! -1)continue;std::queueTIN_with_info::Face_handle todo;todo.push(fh);int size 0;while (!todo.empty()){TIN_with_info::Face_handle current todo.front();todo.pop();if (current-info() ! -1)continue;current-info() int(component_size.size()); size;for (int i 0; i 3; i)todo.push (current-neighbor(i));}component_size.push_back (size);}std::cerr component_size.size() connected component(s) found std::endl;Mesh tin_colored_mesh;//Mesh::Property_mapMesh::Face_index, CGAL::IO::Colorcolor_map tin_colored_mesh.add_property_mapMesh::Face_index, CGAL::IO::Color(f:color).first;CGAL::copy_face_graph (tin_with_info, tin_colored_mesh,CGAL::parameters::face_to_face_output_iterator(boost::make_function_output_iterator([](const std::pairTIN_with_info::Face_handle, Mesh::Face_index ff){// 灰色标记建筑物立面及待处理的其他非地面点if (ff.first-info() 0){color_map[ff.second] CGAL::IO::Color(128, 128, 128);// put(color_map, ff.second, CGAL::IO::Color(128, 128, 128));}else{// 其他标记随机颜色CGAL::Random r (ff.first-info());color_map[ff.second] CGAL::IO::Color (r.get_int(64, 192),r.get_int(64, 192),r.get_int(64, 192));/*put(color_map, ff.second, CGAL::IO::Color(r.get_int(64, 192),r.get_int(64, 192),r.get_int(64, 192)));*/}})));std::ofstream tin_colored_ofile (colored_tin.ply, std::ios_base::binary);CGAL::IO::set_binary_mode (tin_colored_ofile);CGAL::IO::write_PLY (tin_colored_ofile, tin_colored_mesh);tin_colored_ofile.close();return 0;
}如下图所示灰色标记为建筑物立面其他联通区域标记随机颜色 构建编译运行
cmake -B build -S . -DCMAKE_TOOLCHAIN_FILED:\vcpkg\scripts\buildsystems\vcpkg.cmake
cmake --build build --config Debug
.\build\Debug\coloredTIN.exe参考
https://doc.cgal.org/latest/Manual/tuto_gis.html
