Every cooling vessel logged "Invalid polygon data, triangulation failed"
once per frame, for as long as its cooldown ran - 16 of them in a single
test_laser_vessel run. The fill was drawn anyway, so nothing looked wrong,
but it buried real errors in test logs.
_filled_hull cut each hull edge against the fill line itself, which is
Sutherland-Hodgman, and Sutherland-Hodgman is only sound for a CONVEX
subject. Hulls are not: the gas bomber has a tail notch and the distorder a
waist. On those it stitched the pieces back together with a zero-width
bridge, and a polygon with a zero-width bridge is not one the triangulator
accepts.
Geometry2D.intersect_polygons does the clipping properly and returns a list
of polygons, which is also the truer answer - a notched hull genuinely fills
as two puddles until the level rises past the notch. A weld-and-area guard
stays in front of the renderer for repeated vertices and slivers.
Zero triangulation errors across the vessel tests now.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
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