Help! closing open polysurface

Hi there,

I hope someone can help me troubleshoot this problem.

I am trying to close an open ploysurface but I am having a very difficult time. Now, I have extruded a 2d drawing and I am trying to make a “roof” for the open ends. I have tried the blendsrf tool I find that since my curves are complex in certain parts which either makes my it go really wild or the the edges keep pinching. I am trying to make a “rounded roof” rather than flat but not sure which tools to use.

I’ve looked at several video but I’m not sure what I am doing wrong.

Any suggestions?

Hi Athanasia - it really is best to post a Rhino file with the objects you’re asking about.


Thanks Pascal

I’m trying to close the flower of the children’s drawing. I’ve tired tools like rail, Boolean difference and blendsrf. I want a rounded roof rather than a flat point. I thought maybe I could grab points and pull to desired shape but there are no points on polysurfaces. I’ve also tried making this drawing as a mesh the patching the mesh but the same outcome.

My file is too large to send. Brb with a smaller file

Hi Athanasia - select and export just the bits you are asking about to a new Rhino file, and use Save Small in the export…


Wow! Didn’t know you could do that!

Here you goflower head.3dm (7.3 MB)

Hi Athanasia - do you want the top to be flat? Just cap off the vertical walls?

  • Pascal

No, I want the top to be rounded. I’m not sure which tools would be best to do this.

Hi Athanasia - rounded as in ‘puffy’ as if t were a sort of cushion with this outline, or rounded as in all cut out if a more or less spherical surface? (First one hard, second one easy)

In any case the large outer curve has a couple of spots that should probably be tuned up - in the upper left there’s this zig:

(I’d just delete those two points)

And over to the right, you might want to separate the two points that are piled up at the base of the arrow here:

Then you can at least create a solid from that curve and the interior curves, which will be a start.


Thanks Pascal.

Is there something I should know about the “zig”? I’m not sure what’s wrong with it. I guess the second image looks like it is overlapping.

At this point I woulf like this test drawing to be look like a spherical surface. What tool would you suggest? Blend surface?


Here is an image of my blendsrf fail. I’m trying to blend the entire image for the rounded effect. This really shouldn’t be this difficult. What am I doing wrong?
Please help me figure this out.
Example of blendsurface.3dm (7.5 MB)

Yeah… that is not going to work. My guess is that what you want is a sort of ‘bubble’ top to this thing and that s not easy given the curves you have - I’d be inclined to use meshes for this rather than surfaces. It’s possible that using Heightfield may get you something workable, I’ll see if I can make something that is not too terrible.

@Athanasia, I’d say this is possible but very hard to make cleanly to make from surfaces - I’d investigate mesh based programs that can use images for sculpting meshes and use the outline you have, filled in black, as a starting point. Rhino’s Heightfield can make 3d surfaces or meshes from grayscale images but there are better tools I think for the sort of thing you have here - MudBox or ZBrush might be useful.


Here’s what I did - I picked the curve I wanted to put a roof on. This is just ONE of the Eleven curves you had. I cleaned up the curve where you have Cusps, and then created a surface using the Surface - Planar Curve tool. I then drew a curve on the surface using Curve - Freeform - Interpolate on Surface as the “Spine of the Roof”. I then lifted the line an arbitrary distance, turned on Control Points, and brought the ends into contact with the edge of the surface. I then used the new line to split the line that was the outline of the surface. I now have two connected “Rails” so I can build the surface one section at a time using the Surface - Sweep 2 Rails function. To make this work I have to add “Cross Section” curves.
Because your outline is so complex, I put “Cross Section” curves at the sides of the skinny, complex sections of the curve.
Then I started building the roof in sections. Select inside the section you want to surface, and have at it. I’ve attached my version so you can see what I did, and hopefully reconstruct the process.flower head BH.3dm (10.2 MB)

Thanks @pascal and @Brian_Hughes

I decided to do this the most simplest way possible. I’m really trying to learn this program and feel I am missing some basics. Thanks again for your help.

Let me highly recommend various Rhino videos. I learned most of what I use in the video about designing a pair of sunglasses, on Vimeo I think. Great stuff.

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