Creating a Solid for a Closed Polyline

Hello Everyone,

I need some help trying to extrude a solid from a curve. I have a tent that I’m trying to get in to a 3D model. I have the basic 2D drawing with the pattern pieces placed together of how the tent needs to look.


But, when I try to start extruding the pieces they are not extruding as a solid piece. I’m trying to extrude to a thickness of 0.063. I’m using Solid > Extrude Planar Curve > Straight. But the patterns are only extruding on the edges.


I’ve retraced the pattern using osnap with the polyline tool and made sure all ends were joined.


But no luck… I can create a regular rectangle and it extrudes with no issues


Is it something I need to do differently where the pattern pieces are curved or what am I doing wrong?


ExtrudeCrv can only create a solid if the input curve is a closed planar curve. Your input curve appears to be non-planar. If so ExtrudeCrv cannot create a solid. You will need to create surface first and then extrude the surface.

There appears to be an error or faulty logic in the functioning of ExtrudeCrv. If the selected curve to extrude is non-planar the Solid option is still displayed but ignored. If the selected curve is non-planar the Solid option should not be displayed.

Thanks David, if I’m understanding correctly, my surface is non-planar because the corners of the floor panel are curved down (rectangle isn’t flat)? To be able to extrude, I would have to create a flat 2D rectangle with the measurements I need, extrude the surface at a thickness I need, and then shape the surface? I was thinking it would be easier to start out with drawing the object in 2D and then extrude… I also tried the loft function but it didn’t look right that way either. I’m new so I’m sure it was something I was doing. In your opinion, what would be the best way to create the tent in a 3D model? Just trying to get started in the right direction with the best way to understand. Thanks for all your help!

“Planar” means a curve would fit on a flat plane. So if the corners curve down the curve is non-planar.

My next step would be to create surfaces using the 3D curves. I would not try to create any thickness until I had a complete set of surfaces and was satisfied with the surfaces. I would probably use OffsetSrf or Shell to create thickness rather than one of the extrude commands.

Commands for creating surfaces include Loft, Sweep1, Sweep2, EdgeSrf, PlanarSrf, NetworkSrf. Each is appropriate for certain situations and has limitations. If you post a .3dm file with your curves someone might make some suggestions of how to create the surfaces you need. You can post a file using the vertical arrow above where you type your post.

You should consider taking time to read through the User’s Guide which is actually a tutorial on the basics of Rhino, and look through the relevant parts of the Level 1 and Level Manuals.

Hi and thanks for all the info David. I greatly appreciate all your help. I work for a company that specializes in cut and sew and we are working our way into the 3D world. So I’m trying to learn all I can! I’m working on getting a project (tent) put into 3D. I’ve been reading the tutorial and I’m almost through chapter 6. When I wasn’t able to get the outcome I was looking for with the tent I thought I was misunderstanding something somewhere. Looks like I just need to skip around the tutorials and find the info to get the tent project finished and then I will need come back to all the rest of it. I have also attached the .3dm file if anyone might have any suggestions please let me know.

Oh one other question… you mentioned to create surfaces using the 3D curve but I’m using the lines in the standard tab, which curves do you mean? Would you be talking about the curve tool tab?

1MT-2D.3dm (118.6 KB)


Just wanted to ask if anyone has any suggestions on how I would create a surface from the curves that I put together for a tent I’m trying to put in to a 3D model.

Thanks in Advance,

Hi Veronica - a few pointers:
Try to keep your curves as low-point as possible. So, instead of your curve to the left, make a curve that -within your tolerances - is more like the one on the right:

Make those curves in one of the orthogonal viewports. Then extrude these into surfaces and create intersections with other surfaces. Use these intersections to trim one another.

Many of your curves consist of very short single line segments. The different curves that should define the same border between surfaces are also not lined up and some have weird steps like this:

Details such as using different color or even type of materials in one object can be added later. They will still need to represent the same general shape and should be modeled as one surface.

The input curves don’t completely define the desired output shape - the attached is a quick attempt to generate some surfaces that more or less resemble the input curves. It’s by no means perfect.

1MT-2D.3dm (524.7 KB)

Also, when you want to model for production of real objects, you will also have to learn about developability of surfaces in relatation to allowed stretch and deformation of specific materials.

Hi Wim,

Thank you so much for all your information. These were pattern pieces that I imported in with the weird step in it (those were notches for sewing). I realize it’s going to be best to create the patterns myself in rhino using the actual pieces as just a reference. So when making the curves they need to be made in one of the viewports such as the front, top, and right views. It’s best to use the arc tool for curves to not have so many short single line segments. The steps I need to take would be to draw the lines with the curves, extrude surfaces, and trim with other intersecting surfaces. Also thank you for the file to view. It looked great! Hoping I can achieve this some day. I know you said it was by no means perfect but it looks really good. I’m going to read through the tutorials some more and attempt piecing the tent together as I go along.

Thanks Again,

Note that that is not a strict requirement. Generally, you will want to draw planar curves (but not always) and the front, top, and right views are readily available. Going a step further, you could set up your own “construction plane” (CPlane) and draw a planar curve in that.

Yes, you want to avoid short line segments but also single curves with lots of points. Arcs are nice and simple but you don’t always want a true arc. This is where the “degree” of a curve comes in. In the document that John linked to in your other thread, you will read that circles, arcs, and conic sections are degree 2. Often, you will work with curves of degree 3 or 5. The simplest degree 3 curve will have 4 points (degree + 1).