Line rendering without geometry shaders?

[rastertail]

Some old hardware may not support geometry shaders, which are currently required for line rendering. It is possible to implement it without geometry shaders, however it is at the expense of generating more verts on the CPU and using a bit more memory bandwidth every frame. It may not even be worth it to support devices this old, especially depending on what the overall performance cost will be.

[rastertail]

Turns out wgpu intentionally doesn't support geometry shaders due to some performance concerns. 😃 Looks like we will either have to deal with the CPU penalty or use computer shaders, and I'm not a big fan of compute shaders.

[rastertail]

New plan: upload line data to an SSBO, don't bind a vertex buffer, and assemble the line quads directly in the vertex shader. This solves everything with no apparent drawbacks.