[jasza]

Ok thanks for the tips, The code does this a few thousand times (can be up to 60 000 times) :
 _viewport3D.Children.Add(boxVisual3D)
   _viewport3D.Children.Add(txtVisual3D)
_eventManager3D.RegisterEventSource3D(visualEventSource3D) // for each boxVisual3D

I will try without the textboxes.

Excuse my ignorance, are there any code changes needed to switch to using Ab3d.DXEngine ?
I don't feel like re-writing a year's worth of code!