How do to do an elipse/oval to circle blend?

See attached screenshot and 3dm file. I would like to create a funnel-like object that has an elliptical base that blends into a round top. Anyone have any suggestions on how to do this?

BlendTest.3dm (38.5 KB)


PS RC1 Rocks! I can hardly wait to actually cough up the $ for the shipping product!

Loft or Sweep1 should do what you need. Any luck?

You rock Brian! I had tried sweep without success but Loft worked perfectly:


So the next question is, how would you do this so the taper is also curved and not straight? Does that make sense?


Click ellipse, click circle, click the taper curve, Enter.

Thanks. Maybe I just don’t understand how to use the sweep tools since I can’t seem to get anything logical out of them when I try.

Spoke too soon: I got sweep 2 to do what I want, now I need to figure out how to get the curve I want to sweep! thanks!

And the next and hopefully final question…

I’ve never quite understood how to use a surface to make a solid. In this case, take a look at:

This is the surface I created using Sweep 2 Rails and it is exactly what I want the surface to look like! Now, I want to create a solid that I can ultimately use to 3D print a part. I’ve tried Solid->Cap Planar Holes and that does not appear to do anything. How would you create a solid from this? After I have a solid, I can easily create a elliptical base extrusion that attaches to the bottom of this part and a little detail on the top. Imagine a chess piece.

Hi Michael- if the top and bottom edges are planar and closed, Cap should close off the ends, then Shell can give you a wall thickness. Any luck with that?


No, cap does nothing but I think I have something that works like this:

  1. use Surface->Patch to patch the top and bottom openings
  2. use Solid->Create Solid and select the top and bottom “patches” and the surface

This seems to have created a solid. The object details say: Geometry: valid polysurface. Closed solid polysurface with 3 surfaces/

That will work but if you expect the ends to be planar and they are not, I would investigate and fix that.


I do expect the ends to be planar and they seem to be. How would I check?

Hi Michael - can you post the model?


Sure, this is what I have so far. Of course, it is a lot more complicated than I was presenting above! I am basically making a mold that I can 3D print and then cast in rubber to replace a rubber electrical boot on a fuel pump. The mold has a solid core with a hole in it for a locator pin. That is the Core layer. I then need to make the shell with a 1mm gap between it and this core. That is the Solid layer and the Shell layer is an arbitrarily larger piece that the Solid will be subtracted from to make a mold. Make sense?

EarlyPorsche911FuelPumpBoot.3dm (294.2 KB)

Hi Michael - you have cap surfaces in place but not joined in - you can delete those and run Cap (than you will see the difference) or just Join them to the bottley shape to close it off.


That file was a WIP so I am not sure what you mean. I create the cap surfaces using Patch and then Create Solid to join them. That seems to work as I’ve now made all 3 solids.

The only minor issue I’m running into is subtracting the Solid layer from the Shell layer - the bottom has an opening as expected but the top is still closed. Here are some screen shots and an updated 3dm file with my current version.

EarlyPorsche911FuelPumpBoot.3dm (462.2 KB)

Hi Michael- if you want both ends open, you can either pick both ends in the Shell command, or start with the open surface (no caps) and OffsetSrf with Solid=Yes.


Thanks Pascal, I’m not sure how to do what you are asking but I used brute force by adding a 1mm tall cylinder on the top of Solid and joining them into a single. I then subtract this from Shell and it opens the top. Perhaps the top of Solid is slightly lower than the top of Shell so it was not subtracting properly.

I’d love to figure out what you are suggesting though so I’ll try to think through it.


Hi Michael - see if the attached helps.

EarlyPorsche911FuelPumpBoot_PG.3dm (533.2 KB)


Ok, I’ve simplified this drawing to focus on what you are talking about. The attached has two surfaces Solid and Shell. Basically, Shell was created by offsetting the Solid by a few mm. What I want to end up with should look like this from the bottom:

Simplified.3dm (215.7 KB)

Wow, this was very helpful. OffsetSrf with solid! Now that’s a great feature. It’s really too bad that there is not a good book on RhinoCAD. I can’t afford the time or money to attend a training class and I don’t like those sorts of classes anyway. But a good book I can grok.