1 Reply Latest reply on Nov 1, 2016 6:26 PM by Ryan Feeley

    Equal Curvature Relation Bends the Wrong Way in 3D Sketch

    Ryan Feeley

      Hi, I'm trying to put an "equal curvature" relation on a style spline in a 3D sketch. The spline is sketched with an "on plane" relation. When I attempt to add the relation, the magnitude of the curvature is correct, but the sign is flipped (i.e., it curves in the wrong direction). Is this the expected behavior or a bug? I tried to add the tangent first and manually adjust so the curvature of the two sketch entities "close" before adding the relation, but it still flips to curving the wrong way.

       

      This picture below is from a simple example. Prior to adding the curvature continuous relation, both the arc and the style spline have an "On Plane" relation that puts them both on the front plane. 

       

      Adding Equal Curvature relation flips the direction of curvature:


      After Curvature Relation.PNG

      Here is the position of the two sketch entities before adding the Equal Curvature relation:

       

      Before Curvature Relation.PNG

       

      Any ideas for how I can most easily work around this? So far I'll I've come up with is to manually create construction geometry that curves in the other direction, and then add my relation to that.

       

      Thanks!

        • Re: Equal Curvature Relation Bends the Wrong Way in 3D Sketch
          Ryan Feeley

          Here's another work-around (no fully tested) that is still ugly. Use two sketches to force the solver order. First create arc in a 2d or 3d sketch on the desired plane. Now midpoint extrude a surface with the arc. Create a new sketch with the style spline and the "On Plane" relation. Add the "Equal Curvature" relation to the arc. This will be over-defined since a tangent relation is automatically applied, and one component of the tangent direction is redundant with the "On Plane" relation. Now delete the auto-generated tangency relation and add it back as tangent to the extruded surface, rather than the sketched arc.

           

          I realize that the math is messy when you have "On Plane" relations in 3D sketches, but I want that relation on the style spline itself (rather than say all the control points) so that I can readily change the degree.