Hi all,
In the attached picture, you can see that the front arch isn’t solid - I’m trying to make it a solid shape (like the arch at the back). I also had loads of problems turning the back arch into a solid shape - it did it eventually but I don’t know why.
I make the arch shape as a curve and then extruded it ‘Along Curve’ from the Soild drop-down menu. I thought that extruding it from the Solid drop-down menu would create a solid shape, why does it create a hollow shape instead?
As the solid extrusion didn’t work, I’ve been trying to cap the hollow shape instead, but the error message keeps saying ‘Unable to cap one object. The openings did not have closed, planar loops of edges.’
The curves are closed, as far as I can tell, but I don’t know what it means by planar…
please upload the open objects so we can see where is the problem ( not the entire project, just the objects you want closed)
you can select those object and then export them as a Rhino file.
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“Planar” means the curve will fit on a plane. The plane does not have to be aligned with a Cplane.
The extruded curve must be planar for a solid to be created by ExtrudeCrv or ExtrudeCrvAlongCrv.
Cap has the same requirement.
Arch file.3dm (34.8 KB)
Hi, is the file attached? Thanks for your help
I’m still not sure what this means. Can you put it in different words? 
Do you know what a plane is in geometry? (Not an airplane and not a woodworking tool.)
A plane is a perfectly flat surface. A plane in geometry can be as large as needed or desired, so it can extend to infinity. It is a basic concept in 3 dimensional geometry.
there is a tiny difference between edges. in this case I would check the input curves and run SetPt first to align them and have a completely flat closed curve. and then extrude.
but if you want you can close this objetc using Loft between the longer edges:
once joined, it will be a closed polysurface
you also have open objects there with coincident surfaces. I guess is the same issue ( not completely flat or closed curves )
The Rhino Level 1 training shows methods to model with the needed precision and accuracy. The manual can be used for self-learning as well as class instruction. Rhinoceros Help
Tools for precision modeling:
http://docs.mcneel.com/rhino/5/help/en-us/seealso/sak_precisionmodeling.htm
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So, before I extrude, the 2d shape (the plane) needs to be completely flat - and if it’s not completely flat I’ll run into these problems?
I deleted the extrusion and redrew the curve to try and make sure it’s on the same plane. After extruding I was able to cap the open polysurface on both sides - so it now looks how I wanted it to look. However, I extruded from the Solid drop-down, so I’m still confused about why it’s not making a solid arch - it’s making a hollow arch which I then need to cap to make it look solid.
Yes, I need to use these resources. I’m new to Rhino, as I’m sure you can tell. I didn’t have any problems extruding upwards from 2d shapes, but for the arch I needed to draw shapes on the z axis and then extrude along the x and y axis. I was struggling to draw the shapes in perspective view and that’s probably why they ended up being ‘non-planar’. There are probably much easier ways of drawing which I need to learn 
Learn to draw in other views. The Planar and SetPlanar commands are a major help in creating planar geometry. Planar | Rhino 3-D modeling
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