Add faq.rst

Author: zfergus

docs/source/index.rst

@@ -15,6 +15,7 @@
     tutorial/nonlinear_ccd.rst
     tutorial/simulation.rst
     tutorial/misc.rst
+    tutorial/faq.rst
     tutorial/references.rst
 
 .. toctree::

docs/source/tutorial/faq.rst

@@ -0,0 +1,37 @@
+.. _faq:
+
+Frequently Asked Questions
+==========================
+
+.. role:: cpp(code)
+   :language: c++
+.. role:: cmake(code)
+   :language: cmake
+.. role:: python(code)
+   :language: python
+
+How do I include IPC Toolkit in my project?
+-------------------------------------------
+
+If you are using CMake, the public include directory is added to the :cmake:`ipc::toolkit` cmake target which means that any lib/bin that includes :cmake:`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 :cpp:`#include <ipc/...>` in C++ and :python:`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 :cpp:`BroadPhase` classes, the function :cpp:`detect_edge_edge_candidates` determines which edges intersect based on their bounding boxes. You can then use :cpp:`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 :cpp:`igl::edges(faces, edges);` in C++ or :python:`ipctk.edges(faces)` in Python.
+
+My question is not answered here. What should I do?
+---------------------------------------------------
+
+Please open an issue on `GitHub <https://github.com/ipc-sim/ipc-toolkit/issues>`_ and we will do our best to help you.