Frequently Asked Questions¶

How do I include IPC Toolkit in my project?¶

If you are using CMake, the public include directory is added to the ipc::toolkit cmake target which means that any lib/bin that includes ipc::toolkit as a dependency also adds those include directories too.

If you are not using CMake, the include path is src.

Files are included with the prefix #include <ipc/...> in C++ and import ipctk in Python.

How do I determine which edges intersect?¶

We do not provide an edge-edge intersection function in 3D, but you can approximate it by computing the distance between the two edges and checking if it is less than a threshold.

Inside any BroadPhase classes, the function detect_edge_edge_candidates determines which edges intersect based on their bounding boxes. You can then use edge_edge_distance to check if they approximatly intersect by computing the distance.

How do I build the edge matrix from the face matrix?¶

To build the edge matrix you can use igl::edges(faces, edges); in C++ or ipctk.edges(faces) in Python.

Is there a way to ignore select collisions?¶

Yes, it is possible to ignore select collisions.

The functionality for doing so is through the BroadPhase::can_vertices_collide. This function takes two vertex IDs and returns a true if the vertices can collide otherwise false.

This is used to determine if any geometry connected to the verties can collide. E.g., when checking if vertex vi can collide with triangle f = (vj, vk, vl), the code checks:

can_face_vertex_collide(f, vi) := can_vertices_collide(vj, vi) && can_vertices_collide(vk, vi) && can_vertices_collide(vl, vi)

This is a little limited since it will ignore the one-ring around a vertex instead of a single face-vertex pair, but hopefully that can get you started.

To get something more customized, you can try to modify the BroadPhase class, which has these functions hard-coded:

virtual bool can_edge_vertex_collide(size_t ei, size_t vi) const;
virtual bool can_edges_collide(size_t eai, size_t ebi) const;
virtual bool can_face_vertex_collide(size_t fi, size_t vi) const;
virtual bool can_edge_face_collide(size_t ei, size_t fi) const;
virtual bool can_faces_collide(size_t fai, size_t fbi) const;

You can modify these with function pointers or override them to have the specific implementation you are interested in.

My question is not answered here. What should I do?¶

Please open an Q&A discussion post on GitHub and we will do our best to help you.