plutoplot.com is an online 3D graphing application I wrote a while ago. It supports entering equations in a fixed WYSIWYG panel in the top left, and using orbit controls (click and drag to orbit, scroll wheel to zoom) to control the 3D view.

Plutoplot is built on THREE.js, which in turn uses webGL for its rendering. For the math input, it uses guppy.js, which is relatively obscure, but gets the job done in a really nice way. The source for Plutoplot is, more or less, the source of the page, except for the modifications I had to make to the guppy on-screen-keyboard. At this point, I’m mostly documenting its existence, since the source code isn’t very extensible (especially for the interface).