Since we do not use the 'along' property anywhere, and the
resulting array returned by closestOnSegment could cause trouble
when working with 3d coodinates, now only the closest point is
returned, and the squared distance to the segment is calculated
by squaredDistanceToSegment instead.
In the typical sequence of parse-transform-render the most efficient place to transform coordinate values is deep within the parser immediately after values have been read (this would avoid a second pass over whatever structure is used to back geometries). To accomplish this transform during parsing, we could add back parser read options to pass the transform function around.
Until then, a transform method on geometries is straightforward to implement. This means we do a second pass through coordinate structures to transform, but this is typically done only once immediately after parsing.
Previously, a lookup object containing start indexes was also used. This allowed us to remove arrays of vertices and properly update the start indexes for remaining coordinate values. In order to provide callers with stable identifiers and to work with arrays of integers alone, we cannot support a remove method. I think this is worth revisiting. Even if the array length cannot be changed in WebGL, we don't need to also impose the restriction outside. Instead, the WebGL renderer could be notified when array sizes change and update itself accordingly. I think there is more value in providing geometries with stable identifiers.
This common structure is used to store vertices for all geometry types. A slight optimization could be made by creating yet another structure to store point vertices - since these don't need to have a counts array (always 1). Creating a new structure would mean saving memory at the expense of more lib code to transport. The coordinate value lookups are not negatively impacted by using the same structure for points and higher order geometries. Since the first change above goes against my instincts, I'm not making this second change (to add another structure for shared point vertices).
Its not clear that we will be able to leverage the Float64Array. It may also be that the overhead of constructing these small arrays negates any benefit of faster access. And for all coordinate arrays, we'll need arrays that grow/shrink.
