Note:This is a Qt project, in order to run this you have to have Qt installed! Open Graphics Library (OpenGL) is a cross-language, cross-platform application programming interface (API) for rendering 2D and 3D vector graphics. The API is typically used to interact with a graphics processing unit (GPU), to achieve hardware-accelerated rendering.

• In order to use opengl libray in Qt, we need to add QT += opengl to .pro file to link against the module. Add #include <QtOpenGL> to include the definitions of the module's classes. Note: A module is just a bunch of header files reside together in one file, example of #include <QtOpenGL>:

  #ifndef QT_QTOPENGL_MODULE_H
  #define QT_QTOPENGL_MODULE_H
  #include <QtOpenGL/QtOpenGLDepends>
  #include "qgl.h"
  #include "qglbuffer.h"
  #include "qglcolormap.h"
  #include "qglframebufferobject.h"
  #include "qglfunctions.h"
  #include "qglpixelbuffer.h"
  #include "qglshaderprogram.h"
  #include "qtopenglglobal.h"
  #include "qtopenglversion.h"
  #endif
  
  

  After #include <QtOpenGL>, you can use <QGLFunctions>, <QGLShaderProgram> and so on. Alternatively, you can do #include <QGLShaderProgram> or #include <QGLFunctions>to include each of the class definition in <QtOpenGL>, that way you can be aware of what methods come from what classes.
• gl_ModelViewProjectionMatrix in shader file(normally is multiplied by a Position attribute variable, eg. gl_Position = gl_ModelViewProjectionMatrix * a.Position) is controlled by glfunctions, eg. glLoadIdentity(), glOrtho(GLdouble left, GLdouble right, GLdouble bottom, GLdouble top, GLdouble zNear, GLdouble zFar), glRotated(GLdouble angle, GLdouble x, GLdouble y, GLdouble z) and so on, these are outside shader files, normally they reside in program methods, like

  void HW3a::resizeGL(int w, int h)
  {
      // save window dimensions
      m_winW = w;
      m_winH = h;
  
      // compute aspect ratio
      float ar = (float) w / h;
      float xmax, ymax;
      if(ar > 1.0) {		// wide screen
    	  xmax = ar;
    	  ymax = 1.;
      }
      else {			// tall screen
    	  xmax = 1.;
    	  ymax = 1 / ar;
      }
  
      // set viewport to occupy full canvas
      glViewport(0, 0, w, h);
  
      // init viewing coordinates for orthographic projection
      glLoadIdentity();                               ////////////////Control gl_ModelViewProjectionMatrix//////////// 
      glOrtho(-xmax, xmax, -ymax, ymax, -1.0, 1.0);   ////////////////Control gl_ModelViewProjectionMatrix//////////// 
  }