I’m not sure how I created this curve, so I can’t reproduce this, but in this case I can’t set any continuity options for sweep2 without rebuilding the curve.cant sweep2 tangent.3dm (61.0 KB)
The curve is rational. The continuity options only work with non-rational curves. Added: Rebuilding creates a non-rational curve.
Continuity is only enabled if the rails are surface edges and the shape curves are non-rational, that is, all control-point weights are 1. Exact arcs and ellipse segments are rational.
Only continuity options that the curve structure (point count and rational/non rational) supports will be available.