I just posted the video I made of Virtus Walkthrough. I created this in 1990 with David Easter and Mark Uland. I am actually demonstrating Virtus 4 here. Scott Haynes was responsible for this version, and I think it is the best version of Walkthrough we ever did. It was also, unfortunately the last. The overall design and interaction is almost identical to the original 1990 version, though. This is using a software renderer that I wrote and was greatly enhanced by the team led by Greg Rivera. It uses portals extensively, and though you won't notice it, it does not actually have a z-buffer. The objects are sorted using a kind of BSP thing I did that is extremely fast. I am actually running this on Parallels on an older Macbook, and it feels faster to me than Sketchup 7.1, which I run native. But of course, considering that this had to run in real time on sub-20 mHz 68010 and 68020 machines, this had to be pretty damn fast to work at all.
This is the system I first prototyped the virtual collaboration space in that I showed to Alan Kay. This led to the development of ICE (see previous post), OpenSpace, the Croquet Project, and Teleplace.
Virtus Walkthrough won many awards, including the very first Breakthrough Product of the Year from MacUser Magazine, and the PC Computing Best Drawing Program, where we beat Adobe Photoshop.
Here is the demo: