enhancement: line-rendering overlapping lines

Motivation

Example Here

(NOTE: the experiment currently only exists in Utah for demonstration purposes, just click a point to see it working)

right now I am using the cpu to render the polygons to ensure clean polylines / polygons.

I was hoping to draw this via the GPU so that during movement and zoom you could still enjoy the visual.

currently the line/fill apis from mapbox has issues with overlapping geometry:

Is this an easy fix? If not, I would say just drop it.
My theory is that when points are too close together, the current tessellation algorithm gets confused.

If it is fixable, I was just going to copy paste your solution into a custom with proper alpha filtering to blend like i did as you see in the example link.

Design Alternatives

I said enhancement rather then bug because it's not an issue for >95% map use cases.

Design

see link above

Mock-Up

see link above

Concepts

Implementation

WebGL

Start by reproducing the overlapping-line behavior in the linked isochrones.regia.io example, then trace the line and fill rendering paths and the tessellation behavior for closely spaced points. Done would mean GPU-rendered polylines or polygons remain visually clean during map movement and zoom without the reported overlap artifacts.