Visualhull — the series
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The dish no outline reaches
An outline is a pair of numbers per direction and nothing more, so a shape built from outlines has two errors that behave differently. The part outside the convex hull falls as one over the square of the view count. The part inside a concavity is the same area at four views and at a hundred and twenty-eight, because no pair of supporting lines ever reaches into a bite.
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An outline reaches a waist and not a dish
In a cross-section nothing a silhouette does can enter a concavity. On a solid that stops being true, because a solid has lines a section does not contain. A spool's waist comes back in full from a ring of outlines, and a dish in the same object's lid never does. What decides it is whether a straight line can leave, and the answer is water.
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A groove is reached only along its own plane
A groove round a drum is the kind of hollow outlines can clear, and a level ring clears it completely. Raise the camera three degrees and more than half of it stays filled at any number of views. On this object the height of the camera decides the result, and the count of views buys almost nothing.