For example, you could use open-source OpenTK, based on OpenGL:
http://www.opentk.com/doc/chapter/2/glcontrol[
^].
But frankly,
System.Windows.Forms
application is not the best container for advanced (and even not so advanced) 3D graphics; you can do a lot more and much easier with WPF:
http://msdn.microsoft.com/en-us/library/ms747437%28v=vs.110%29.aspx[
^].
As to the Forms, I can see one major benefit: the possibility of Mono-compliant development; OpenTK is, for example, Mono-compliant. If you don't care about it, WPF will be, in most cases, the apparent winner.
And by the way, if you are really want to target G code, CNC and other CAD/CAM stuff, the sooner you get rid of your illusion that this work is "very simplified", the better. It is not "simplified", it is serious enough; take it very seriously.
—SA