Trouble rounding the end of a closed, flat planar curve

Hi, I am having a tough time creating a rounded cap or fillet on the ends of a chair that I am modeling in Rhino 5. Here is a screenshot. I have tried the fillet command and it is not reading properly due to there being a closed curve. I also tried blending surfaces to no avail. Finally I duplicated the border, drew arcs on the x and y axes and attempted a curve network that didn’t work. I know for a fact it’s planar bc it caps etc. Thanks in advance.

If you Cap it you can FilletEdge it. For a more overall rounded edge you can use setPt to collapse the control points of the opening down to a single point, then you need to make sure (again SetPt can help) that the end point and the points surrounding it are on the same plane.

Thanks for your response Jim,

I have attempted to Fillet Edge it and it is twisting at the corners of the curves. I adjusted the radius of the handles as well. At a small amount it works, but is not enough.

As for the set point I do not completely understand. Is that a way of checking if it is planar? Is it true that it would not close if it were not planar? Thanks again. I like the fillet option maybe theres something I am doing wrong. I wonder if theres any other options.

post your model please.

maybe you could try railrevolve. just an idea.

Thanks here is my model.

Chaise Closing Attempt.3dm(7.5 MB)

As far as rail revolve goes, I am not sure how that would work because the closed curve is not symmetrical; however, I am not an expert on that commands intricacies.

Here’s one way to do it. I offset the edge on the flat cap and cut a section through the body parallel to the cap. I trimmed both parts to these curves. The new edges become the rails for a 2-rail sweep. Then I created a cross section curve at either end of the rails and made them tangent to the surfaces.

I did the 2-rail sweep and used tangency on both A & B rails. It’s pretty sharp on the top, but this can be adjusted with the offset curves.


Chaise Closing Attempt JT.3dm(243.5 KB)

Hi James that looks clean. Thanks for the work!
I am attempting to follow your instructions, but am a little confused as to how you offset the curve. Did you do it to the object with the cap on or with it off? When I offset the half curve it only moves the curve (and twists on the corners) and not the surface as well. I am guessing you split the curve then. Also when you created the tangent curves what were your two rails if there was only one curve that was offset?

Thanks so much!

Chaise Closing Attempt JT.3dm(230.3 KB)

I exploded the model so that I could work with half of the body. I also cut the cap in half on the centerline. In the front view I offset the edge of the cap and used the offset curve to cut the cap back the distance of the fillet. I used offset with the “throughpoint” option and eyeballed the result to get a curve that wouldn’t loop at the tight part of the curve.

Then, in the side view. I cut a vertical section through the body where I thought I’d want the fillet to be tangent. Then I used the resulting section to trim the body. The new attachment has the line I used to cut the section…

So, there are the 2 cross sections that I drew by hand and made tangent. The rails are the edges of the cap and body. Use the edges rather than the curves so you have surfaces to make the sweep tangent to.