Function ring_uniform 

fn ring_uniform(
    out_x: f32,
    out_y: f32,
    size: f32,
    color: [f32; 4],
    aspect_ratio: f32,
) -> (BorderUniform, bool)

Build a BorderUniform for one ring given its outer extent (out_x, out_y) in clip space, the MD2 size (a fraction of the shorter screen axis), the RGBA colour, and the framebuffer aspect ratio width / height.

Returned (uniform, visible) — visible is false when alpha is ≤ 0 or when the requested thickness is so small it would render zero pixels.