Explained: Real-time heatmap example

Hilarious...I wrote almost the exact same thing as a GazeHawk visualization about a week ago.

Interesting how he uses the same canvas element to track opacity and display the colorization. You can split out the opacity into its own (hidden) canvas so that the opacity is only bound to the color mapping, not the actual display.

The demo doesn't seem to account for a stopped mouse. If you move the mouse slowly in one area, it gets really hot, but if you put your mouse in one spot and don't move, it doesn't get recorded at all. This seems like a big hole.