Filling in a Multi-Sided Area

I wanted to know if anyone has an approach for this type of problem.

I have an odd outline that is given to me. In this particular case I need to fill in the area outlined blue with “a surface.” Because it’s 5-sided, that means more than one surface. In this particular case that surface(s) needs to be tangent to the purple shape but needs only to be coincident to the red (not tangent but needs to be not way different—there will be a gap inserted below the red to conceal any slight discontinuity)

The rest of the area should be as smooth as possible. There is obviously going to be some undulation. The curve at the lower left is going to create an indentation. That indentation should flow horizontally.

I have tried to divide the open area in many ways. My problem is that I have is that I always get a noticeable kink at my division curve.

Is there a good method to divide a border like this up such that one can create surfaces that will flow smoothly from one to the next?

Problem Filling.3dm (3.0 MB)

I’m not sure if I understood your problem right, but is something like this what you want?

Problem Filling 001.3dm (189.1 KB)

// Rolf

That’s generally what I am trying to do. However, I would need to make all three subsurfaces smooth.

Use the command DupBorder of the red and Blue surface, hide the surfaces, explode the curves and trim.

The remaining should be able to be surfaced with "patch and then joined
Problem Filling.3dm (81.9 KB)

The problem I have with PATCH is the surface pulls away from the border.

I’ve gotten something fairly close here but I cannot seem to get a smooth transition especially at the corn.

It looks like I I my be getting curved lip whenever I do a networksrf so that adding a tangent surface causes a wave.

Is there any way to smooth this out?

Again, I am trying to be tangent to the surface on the right but only need to be coincident to the upper surface.
Problem Filling 2.3dm (3.1 MB)

I got something looking pretty reasonable. I don’t know how I got it, however. I was doing partial sweeps an intersections. It was a time consuming iterative process. It seemed much harder than it should be.

@bigjimslade I recently found this video/tutorial, you may find it helpful for these kind of surfaces, :slight_smile:

That was a good video. I wish there were one on ways to deal with 3 sides.

Basically following that, I was able to simply things. Due to the difference in shape, I could not follow the video exactly.


  1. Split the curve at the left at the top of the arc.

[Building the bottom gray surface]

  1. Create the pink curve on the surface to that it points to the upper end of the arc.
  2. BlendCrv to point from the pink curve to the top of the arc.
  3. Sweep2 along the edge at the right and the curve with the arc, using match curvature to the edge.

This would not follow the curve generated in #3 without wildly distorting the surface. I only matched the bottom curve.

  1. DupEdge surface at the top edge and deleted the curve created in #irhino3d

[Upper Gray Surface]

  1. Sweep2 along the upper upper edge of the lower surface and the short segment at the upper left. Make the edge match tangent. Doing Curvature creates a wild surface.