Static MSAA_SCENE 

pub static MSAA_SCENE: SceneDef

The same scene on a multisampled target.

The world is the one SCENE builds — the difference is the sample count the capture binds, which is the one thing that changes how an opaque stroke is antialiased: single-sampled it cuts at half its coverage, and multisampled the cut yields to alpha-to-coverage, which spreads that same coverage over the samples and keeps the edge smooth.