In case you did not know: This is closely related to an s-buffer (s for span) in graphics. And the first approach (height map) is pretty much a z-buffer. Your

In case you did not know: This is closely related to an s-buffer (s for span) in graphics. And the first approach (height map) is pretty much a z-buffer. Your silhouette there is eye distance (z) across a single scan line. One difference of how it is approached in graphics is that usually not all spans are an input array but inserted one at a time.