In certain cases, a scatter3d trace line disappears

[monfera]

The connecting line on scatter3d may thin away to even zero width, depending on the angle of view. In this example, the trace has no gaps but a gap looks to be present:

Possible reason is this: the rendering seems to represent a line with a flat band (thin, long 2D rectangle). The WebGL renderer attempts to always transform this rectangle such that its cross-section is perpendicular to the line of sight, giving the approximate appearance of a cylindrical line. In specific angles, numerical issues may cause this transform to not work properly; maybe the 'gymbal lock' issue. In this case, a solution may be to pick another reference vector, or switch to a quaternion based rotation which is free of the gymbal lock issue. Will need to look into it to confirm.

Loosely related issue in scatter3d: if there's a gap in the data, but connectgaps is set to true, then the rotation seems to not be in effect for the point with the null value - the line vanishes over its length.

[etpinard]

Fixed in #3163

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