Draw all nodes in the tree using gl.TRIANGLES instead of gl.LINES?

[fedarko]

I read through this article and thought that this might be a useful option to add in. A few reasons that stick out:

• Users may want to increase the overall line thickness for the tree (not just for colored nodes)
  • This could be particularly important for people with vision impairments
• Users may want to be able to "zoom in" on parts of the tree and see the lines / points increase in size. Lines / points aren't impacted by zooming (as far as I can tell), so zooming in can be a bit confusing.
  • Although I could also see "lines look the same at any zoom level" as being an upside to the current way of doing things...
• Plain lines can apparently be inconsistently rendered across different browsers (I don't think this has been a problem, but as more people start using Empress it could be)
• This looks closer to what other tree visualizers, e.g. iTOL / ggtree, do by default (so it makes Empress look less different; I guess this could be an upside or a downside depending on how you look at it)

In terms of the code, I think this'd just involve treating each line analogously to how "thick lines" are currently treated. I'm not sure if this will be a performance problem, but if so we could probably make this a configurable option.

I set up a quick and dirty prototype in this branch, where all nodes are treated as thick lines and all points are drawn as squares using two triangles -- it doesn't look that bad, although nodes overlapping is a problem since the line width used here is 5:

The line thickness would need to be adjusted based on the dimensions of the tree (...so, the same problem as #276). On the other side of things, using too small of a thickness results in an invisible-looking tree when the user is zoomed out:

... although using a default color of black, rather than gray, helps a bit:

Anyway, not a big deal -- but something that we may want to consider.

[ElDeveloper]

This is an interesting idea, I like it in general so as long as performance isn't impacted for large trees.

[kwcantrell]

This would be nice to have as a parameter users can toggle.

For large trees, this can become a bit expensive. However, as tree get larger, making all lines thicker greatly increases the amount of branch overlap. Even in the moving pictures tree, you can begin to see a fair amount of overlap. For tress > 100,000 nodes, I think we risk the tree looking like a single blob. I choose to only thicken colored branch because it them easier to see for large trees.