Interface Bullet Physics library to MATLAB

Question

I'm trying to use the Bullet Physics library within MATLAB. I need to do Collision detection and therefore I wanna use the GJK algorithm. In MATLAB it is possible to compile a so-called MEX function. With the MEX function it is possible to call your own C or C++ programs from the MATLAB command line as if they were built-in functions. My problem is that the Bullet library is very big with a lot of files, header function and so on and I am not really familiar with programming. I looked for simpler implementations and found:

https://github.com/ElsevierSoftwareX/SOFTX_2018_38

It is GJK wrote in C code with a file that gains the wanted MEX function. This file looks like this:

% CLEAR ALL VARIABLES
clearvars

% SELECT OPTIMISATION FLAG - FASTER BUT NOT SUITABLE FOR DEBUGGING
if 0
    optflug = '-g'; %#ok<*UNRCH>
else
    optflug = '-O';
end
% SELECT SILET COMPILATION MODE.
if 1 
    silflag = '-silent'; 
else
    silflag = '-v';
end

% TRY COMPILING MEX FILE
fprintf('Compiling mex function... ')
try
mex('../lib/src/openGJK.c',...  % Source of openGJK 
    '-largeArrayDims', ...      % Support large arrays
    optflug, ...                % Compiler flag for debug/optimisation
    '-I../lib/include',...      % Folder to header files
    '-outdir', pwd,...          % Ouput directory for writing mex function
    '-output', 'openGJK',...    % Name of ouput mex file
    '-DMATLABDOESMEXSTUFF',...  % Define variable for mex function in source files
    silflag )                   % Silent/verbose flag

    % File compiled without errors. Return path and name of mex file
    fprintf('completed!\n')
    fprintf('The following mex file has been generated:')
    fprintf('\t%s\n',[pwd,filesep,'openGJK.',mexext]) 
catch
    % Build failed, refer to documentation
    fprintf('\n\n ERROR DETECTED! Mex file cannot be compiled.\n')
    fprintf('\tFor more information, see ')
    fprintf('<a href="http://www.mathworks.com/help/matlab/ref/mex.html">this documentation page</a>.\n\n')
    return
end

So I tried to do a similar thing with the Bullet library, but I even don't know which source file to use. I tried the 'btBulletCollisionAll.cpp' in the 'src' folder. But like I'm said I'm not really familiar with C++ and I'm wondering why there are only a lot oof header files. Also I need to tell MATLAB where the header files are and how to link them.

So basically I just want to call a function on MATLAB like this:

dist = GJK(shapeA,shapeB);

Here is the Bullet depository: https://github.com/bulletphysics/bullet3

Thanks a lot for your help

Addit: I don't use the SOFTX_2018_38 because I also need EPA algorithm and I think the Bullet library is efficient and robust implementation.

You can not simply compile the library, some adjustement have to be done. Everything is explained in the documentation — obchardon
Hey obchardon, I know that I can't compile the whole library at once. But it would be helpful to know which source file I have to compile and which header files I need to link for that to get a function like this: [dist,simplex] = GJK(shapeA, shapeB) and penetrationDepth = EPA(shapeA, shapeB, simplex) — Marius S.

Bob Bob · Accepted Answer · 2021-06-02T16:41:01

As far as I know a .mex defines a single MATLAB function. The library you pointed seems to be a python library, so I would suggest you to review quickstart guide (88 pages), use it in python and then you think about porting to MATLAB.

It seems you can run python libraries directly in MATLAB

About python, it is a so well covered subject that will not try to write anything else here, there are tons of tutorials you can find with a quick search.

Interface Bullet Physics library to MATLAB

1 Answers