- procedure ResizeViewport(Width: GLsizei; Height: GLsizei);
 -  var
 -    fWidth, fHeight: GLdouble;
 -  begin
 -    w:=Width;
 -    h:=height;
 -    if (Height=0) then            // prevent divide by zero
 -      Height:=1;
 -    glViewport(0, 0, Width, Height);    // reset viewport and perspective transformation
 -    glMatrixMode(GL_PROJECTION);
 -    glLoadIdentity();
 -    fWidth := Width;
 -    fHeight := Height;
 -    gluPerspective(45, fWidth/fHeight, 0.1, 100);
 -    glMatrixMode(GL_MODELVIEW);
 -  end;
 

