SIMTOI with pure off-screen rendering

[bkloppenborg]

It is possible to reconfigure SIMTOI to operate without any on-screen GUI with some changes to the way the QGLWidget is created. Consider the following example:

'''

include

#include <QtOpenGL/QGLWidget>
#include <QtGui/QApplication>

void renderOffScreen ()
{
  std::cout << glGetString(GL_VENDOR)   << std::endl;
  std::cout << glGetString(GL_RENDERER) << std::endl;
  std::cout << glGetString(GL_VERSION)  << std::endl;

  // do whatever you want here, e.g. setup a FBO, 
  // render stuff, read the results back until you're done
  // pseudocode:
  //     
  //      setupFBO();
  //   
  //      while(!done)
  //      {
  //        renderFrame();
  //        readBackPixels();
  //        processImage();
  //      }
}

int main(int argc, char* argv[])
{
  QApplication app(argc, argv);
  QGLWidget gl;

  // after construction, you should have a valid context
  // however, it is NOT made current unless show() or
  // similar functions are called
  if(!gl.isValid ())
  {
    std::cout << "ERROR: No GL context!" << std::endl;
    return -1;
  }

  // do some off-screen rendering, the widget has never been made visible
  gl.makeCurrent (); // ABSOLUTELY CRUCIAL!
  renderOffScreen ();

  return 0;
}

'''