All points whose radii overlap the view should be rendered

[jcn-ithaca]

Currently only points whose centers are in view are rendered, causing (sometimes very large) circles to pop in and out of existence at view edges as you pan.
All points whose radii overlap the view should be rendered. This would create a more seamless experience when panning.
In the below screenshots, scrolling to left by a small amount causes one of the gradient circles to vanish.