Small addition^^: Rendering line primitives with WebGL always results in 1px wide lines. If you need wider lines, consider to use three.js's mesh line implementation:
Apparently openGL had a linewidth property, but it didn’t work on windows, because directX didn’t support it, so the webGL standard removed the linewidth property, or made it optional, depending on the version iirc.
I use this extension if I want more flexibility with lines:
You can specify linewidth proportional to the screen, or object, and even provide an array of widths for custom tapering, it’s very useful.