A solid source's resolution sets mask edge quality: higher resolution gives smoother edges

VPT’s solid source produces a flat white (tintable) fill at selectable pixel sizes: XS (4×4), S (80×60), M (320×240), L (640×480) or XL (1024×768). Used as a plain colour fill with no mask, XS is enough and costs almost nothing to render. But when the solid carries a polygon mask, its resolution determines how smoothly the mask edges render: a 4×4 solid gives visibly blocky mask edges while a 1024×768 solid gives smooth curves. This is a common cause of jaggy masks — beginners leave the default small resolution and wonder why a carefully drawn mask looks pixelated in the output.

Examples

Put a circular mask on a solid layer and compare XS (4×4) versus XL (1024×768): the XL solid shows a smooth circle edge, the XS solid a blocky one.

Assessment

You are masking a solid layer with curved edges. Which solid resolution gives the smoothest result, and when is XS resolution appropriate instead?