Reference or use point picking system from unrender

[pablo-mayrgundter]

Avanka has a good ray picker for large point sets:

https://github.com/anvaka/unrender
https://github.com/anvaka/unrender/blob/master/lib/particle-view.js

used in his great software galaxy, 100k+ point, viewer:

https://anvaka.github.io/pm/#/?_k=6yf0ol