Using OpenGL C functions within Matlab using MEX

Question

Alla 2017-6-7

1
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/343717-using-opengl-c-functions-within-matlab-using-mex

编辑： Alla 2018-7-23

Hello everyone I have been working on a 3D model using Matlab functions and after finishing it I was instructed to "refine" it and make it more realistic in addition to extracting and displaying depth information using OpenGL (C) functions, I have been looking into this for the last few days and it seems possible but I just can't seem to successfully get the simplest Mex files to work because of header problems and missing files and even when I compile the Mex file Matlab crashes when I call it, I want to start by simply compiling a MEX application which creates an OpenGL window, then I assume I'll have to redo the model using OpenGL functions and attempt to display the depth buffer.

I would appreciate any help I can get. Thanks.

EDIT01: Here is an example of a code that I compiled without any problems but crashes MATLAB when I attempt to run it.

#include "mex.h"   
#define GL_VIEWPORT                       0x0BA2
#define GL_DEPTH_COMPONENT                0x1902
#define GL_FLOAT                          0x1406
void mexFunction(int nlhs, mxArray *plhs[], int nrhs, const mxArray *prhs[])
{
  int viewport[4], i, x, y;
  int colLen;
  float *data;
  double *matrix;
    glGetIntegerv(GL_VIEWPORT, viewport);
    data = (float*)malloc(viewport[2] * viewport[3] * sizeof(float));
    glReadPixels(0, 0, viewport[2], viewport[3], GL_DEPTH_COMPONENT, GL_FLOAT, data);
    plhs[0] = mxCreateNumericMatrix(viewport[3], viewport[2], mxDOUBLE_CLASS, mxREAL);
    matrix = mxGetPr(plhs[0]);
    colLen = mxGetM(plhs[0]);
    for(x = 0; x < viewport[2]; ++ x) {
        for(y = 0; y < viewport[3]; ++ y)
            matrix[x * colLen + y] = data[x + (viewport[3] - 1 - y) * viewport[2]];
    }
    free(data);
    return;
}

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li yang 2018-7-23

Hi Alaa,i am wondering if you have solved this problem

Alla 2018-7-23

编辑：Alla 2018-7-23

Helllo Li Yang, this was about a year ago, as I recall I could not use the MEX files because of the problems I described in the original question, I used this <https://uk.mathworks.com/matlabcentral/fileexchange/23792-opengl-net-examples?s_tid=prof_contriblnk%20OpenGL%20.NET%20wrapper OpenGL NI wrapper > OpenGL wrapper for a while and got decent results but it is quite restricted. I eventually moved on from using Matlab as a whole.

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Answer 1

Mark 2017-10-12

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https://ww2.mathworks.cn/matlabcentral/answers/343717-using-opengl-c-functions-within-matlab-using-mex#answer_285559

在 MATLAB Online 中打开

I found you need to run opengl in software mode and not hardware mode. Running the matlab command:

opengl software

before plotting does this. So now mexGetDepth runs without crashing Matlab, but it just plain doesn't work. The viewport never gets set to anything. It's always what I initialize it to before calling glGetIntegerv. If I call glGetError after glGetIntegerv I get 1282 which translates to "invalid command."