Both Fin and OffsetNormal commands fail when used on isocurves of a degree-1-surface.
In this example, the surface is a hyperbolic paraboloid with degree 1 in both directions, all isocurves are straight lines.
- OffsetNormal results in straight line, which has correct offset directions and distances at the ends but obviously comes closer to the surface towards the middle.
- Fin results in a HP-surface (degree 1/1), using the above offset curve as the new edge. The orientation is correctly perpendicular to the original surface, but the height of the fin surface is not constant.
If I’m not totally mistaken, the result should rather look like the green curve with all offset vectors of the same length. As soon as the original curve is NOT of degree 1 both commands seem to be working fine…
Fabian