Partial drawing of model

[stiva]

I am developing a 2d editor. In some cases, is necessary render specific regions of the model, instead of render it all.  This is possible?

[pepijnve]

I guess what you want is view frustum culling. You can find a nice explanation of this technique at flipcode. The view frustum culling can of course be generalized to cull objects that lie within any region, not just the view frustum.
Alternatively you can specify the region you wish to render using additional clipping planes. Check the red book section on "Additional Clipping Planes" for this.