zlacker

>>fs_sof+(OP)
Sutherland figured out how graphic interaction ought to work, with the computer recognizing near points and connecting them. What we now call "snap". He had the key idea of CAD - you can draw with more accuracy if the computer helps.

That demo is running on the MIT TX-0, a transistorized version of Whirlwind and the predecessor of the PDP-1. It was somewhat obsolete at that point, so projects like this could get time on it.

>>Animat+phb
He brushes over the zoom out, which I think was pretty impressive for a computer of this time. There is a lot of redrawing/recalculating going on there. Would be impressive on a 80s microcomputer.

>>depend+2nb
No, rendering to a vector display (hardware whose primitive operations are points and lines) is almost free for the kind of drawings he was rendering. Zoom is just one linear transformation on each point in the model, no different from panning the view.

>>d-us-v+1Jb
I mean, the panning was pretty impressive at the time as well. In Sutherland's 1994 "Bay Area Computer History Perspectives" talk https://www.youtube.com/watch?v=k_cevebLO-A&list=PLKTTWvMgeg... he points out flickering or 'jumping' due to the processor burden of rescaling in a number of places in the Sketchpad demo video, including at 42:30 https://www.youtube.com/watch?v=k_cevebLO-A&list=PLKTTWvMgeg... and at 50:10 https://www.youtube.com/watch?v=k_cevebLO-A&list=PLKTTWvMgeg... .