Visualization library in Python and computation in c++

Question

I am interested in implementing some geometric algorithms and making them interactive. I have used the Matplotlib library in Python for some simple animations and I find it sooo simple and easy to visually test my ideas with. (Thanks Jake VanderPlas!)

However, the biggest and robust geometric algorithms library on the planet is CGAL. I want to make heavy use of the large number of packages in it.

I have played around with CGAL's Qt visualization package, and I did not like it very much. There are not too many examples to play around with and it looks like I will have to spend a wasteful investment in time and effort for a task that seems (at least on the face of it) simple.

My use case would be something like this: When the code starts, a matplotlib window opens, the user clicks in some points, or places and moves certain objects like disks with his mouse. He presses a button which then animates the progress of the algorithm.

My codes will be written in C++ (the language of CGAL) but the code that takes care of the interactivity and visualization will be done in Python. Muscle in C++ and the eyes in Python so-to-speak.

Is this possible? I heard of a library called ZeroMQ which allows to send messages between two live processes but I don't know if this would be appropriate for my problem

Answer 1

You can embed python and its libraries in a C/C++ program and you can embed C/C++ code into python programs as well - either would take care of your use case.

To embed python inside of a C++ program there are useful examples in the documentation for both Python 2 and Python 3 but the simplest example in C would be:

#include <Python.h>

int
main(int argc, char *argv[])
{
    wchar_t *program = Py_DecodeLocale(argv[0], NULL);
    if (program == NULL) {
        fprintf(stderr, "Fatal error: cannot decode argv[0]\n");
        exit(1);
    }
    Py_SetProgramName(program);  /* optional but recommended */
    Py_Initialize();
    PyRun_SimpleString("from time import time,ctime\n"
                       "print('Today is', ctime(time()))\n");
    Py_Finalize();
    PyMem_RawFree(program);
    return 0;
}

Your C/C++ code and python code can call each other as required. It is also worth looking at extending python with C/C++.

There is a huge list of programs that combine C/C++ and python including: GIMP & Blender

Finally there is a python package for interfacing directly to CGAL called cgal-bindings this provides wrappers for the following CGAL packages as at version 0.7:

• Few Kernel primitives
• 2D Triangulations
• 3D Triangulations
• 2D Alpha Shapes
• 2D Convex Hulls and Extreme Points
• dD Spatial Searching (only for 2D and 3D cases)
• 3D Fast Intersection and Distance Computation (AABB Tree)
• 3D Polyhedral Surfaces
• 2D Conforming Triangulations and Meshes
• 3D Surface Mesh Generation
• 3D Mesh Generation
• 2D and Surface Function Interpolation
• 2D Voronoi Diagram Adaptor
• Halfedge Data Structures
• Point Set Processing
• Intersecting Sequences of dD Iso-oriented Boxes
• Polygon Mesh Processing