title: How can I increase the speed of redraw in AutoCAD like app
body: <p>I'm developing AutoCAD like application in C++.I have implemented the basic functions such as pan,zoom and select.But it's very slow because when the mouse moved or zoomed,I must calculate the new position of all the elements and then redraw them.
     enter code hereTo increase the speed of redraw I used a space partitioning technique which divides the space in regions or quadrants and redraw the elements only if they are in the region showing in the current viewport,what's more,when the elements are too small to see,they are ignored in the process of redrawing,this is the so-called LOD.
    Despite this,the speed is slow all the same.
    How can I increase the speed of redraw?
    Or I can't redraw at all.
    How does AutoCAD achive this?
    what exactly does AutoCAD do?</p>