[Somanna]

See the "Rectangular selection" sample in the "Ab3d.DXEngine hit testing" section of the Ab3d.DXEngine samples. The sample shows two possible ways to do the rectangular object selection.

After you have the list of selected objects, you can call the camera.FitIntoView method - choose the method that takes IList<Visual3D> visuals as an argument - pass the selected objects.

I would advice you to check the Ab3d.PowerToys samples and Ab3d.DXEngine samples.

I'm sorry I actually wanted to zoom a (screen) area in the viewport and not zoom a selection. I've edited the question title. Please see.