Hi Brian, yeah that is strange. I investigated it, and it does have to do with the heavy density of the curve.

The way curves are drawn is that they're converted to polylines and then the polyline gets drawn. But the polyline draw engine ignores line segments that are really tiny on screen like less than 0.01 pixels in length. In your case here at certain zoom out levels you're getting on screen lines that are all smaller than that cutoff limit, so nothing ends up getting drawn.

It would not be difficult to tweak this value to something tighter to allow say lines of 0.001 in length, the only thing that I'm not so sure about is what effect that will have on performance on heavy scenes, it's not bad for heavy model performance to have little things drop out really...

- Michael