plugin3D, formerly RTRE, claims to bring real-time high-end visualization to the 3dsMax viewports, and do it for free.

Our powerful 3D realtime rendering engine works inside any 32-bit (64-bit soon) Autodesk 3ds Max 2009, 2010 or 2011 viewport. See and interact with your fully rendered scene in realtime, even with hundreds of thousands or millions of polygons. Move around, make changes, improve look and feel, add animations and see changes instantly. Meet “impossible” deadlines. Make last minute changes. Make an image or movie instantly.

The 64-bit support is still in beta, but the 32-bit version is available for free.  If you want to take your scene and create a standalone interactive visualization to share with others, that’ll only cost $99.

via What’s New | plugin3D – 3D real-time plug-in for 3ds Max and 3ds Max Design.