Because the range of coordinates in the opengl are between 1 to 1, all the sample program at the time of the input data is directly fixed as constant and between 1 to 1, if I'm in a range of 1000 to - 1000 drawing, painting, a width of 500 cube are the coordinates of the cube (0, 0) and (500500500), how conversion (500500500) the coordinate values between 1 and 1? This is their implementation or directly submitted to opengl opengl to achieve?