A header-only C++ class for intersecting a triangulated mesh with a plane.
It returns the intersecting segments, joined into open and/or closed polylines.
The class is templated to suit your required floating point coordinate type and integer index type. For example here we will use a typedef for easy reference:
#include "MeshPlaneIntersect.hpp"
typedef MeshPlaneIntersect<double, int> Intersector;We then create a mesh object object for the intersection. The mesh consists of vertices (points) in 3D space and a list of triangles (three point indices) that make up the faces.
// create some example vertices
std::vector<Intersector::Vec3D> vertices{
{1,0,-1},
{3,0,1},
{7,0,-1}
};
// create a face that links the first three vertices
std::vector<Intersector::Face> faces{
{0,1,2}
};
// create the mesh object referencing the vertices and faces
Intersector::Mesh mesh(vertices, faces);Finally, we need a plane to intersect with our mesh
// by default the plane has an origin at (0,0,0) and normal (0,0,1)
// these can be modified, but we can also just use the default
Intersector::Plane plane;To carry out the intersection we simply call:
auto result = mesh.Intersect(plane);
// the result is a vector of Path3D objects, which are planar polylines
// in 3D space. They have an additional attribute 'isClosed' to determine
// if the path forms a closed loop. if false, the path is open
// in this case we expect one, open Path3D with one segmentThere is a further method "Clip" which, as well as returning the intersection polygons, also returns the polygons around any free edges on the positive side of the intersection plane.
auto result = mesh.Clip(plane);
// the result type is the same as above, but the polylines
// are not neccessarily planar.
// in this case we expect one, closed Path3D with three segmentsThere is a test project that verifies the result for a number of cases. If you come across an unexpected result then please let me know.