# Skinning a non-coplanar frame

Hello! This is probably a common issue but I’m struggling to find a solution that achieves what I want. I’m making some twisted non-coplanar shapes and I want to skin the pointy frame in the above image so that the surfaces are as flat/smooth as possible (like the object next to it).
Is there an extension or native tool way of doing this? I know sketchup only likes triangles in these situations but the result is too bumpy looking for my liking.
Apologies if this question has been answered a million times before. I can’t find the answer I need but maybe someone could point me in the right direction…
Thanks, Chris

It’s not specifically that SketchUp only likes triangles. It’s that the bounding edges must be coplanar in order to create a face. This is a fundamental concept in geometry. If the edges you’ve drawn aren’t planar, you need to make loops of edges that are. Triangles are the easiest way to do that. If you want the surface to look smoother, you have to create smaller triangles which means dividing the edges you have into shorter lengths. You could put in a single diagonal between corners and use SubD (see the Extension Warehouse) to sub divide the two triangular faces into smaller one.

Another option would be to divide the bounding edges into shorter segments (right click on an edge and select Divide) and then use an extension, either Fredo6’s Curviloft or TIG’s Extrude Tools, both from SketchUcation to skin the surface. On the left a single diagonal to make two triangles, on the right, all four perimeter edges divided into 12 segments and then skinned with Curviloft.

If you go to View > Hidden Geometry you should see that the object on the left has a bunch of triangles making up it’s faces too. They’ve just been Smoothed and Softened so it looks nice visually.

With that in mind, are you trying to just make it look good on screen, or are you trying to 3d print it and make it as smooth as possible in the real world, or ?

Either way DaveR has you covered. But if it’s just for the screen, then you can probably get away with using fewer triangles as the Soften and Smooth tools will do the work for you.

Thank you both for your quick replies and sorry for my slow acknowledgement!

Curviloft is definitely the tool I needed; I will spend some time experimenting with it and see whats possible.
In answer to your question Jimmy, I am hoping to eventually 3d print the shapes I come up with so , yes I am trying to keep them as smooth as possible. I suppose this will mean keeping the entity count pretty high.

Yes. It does.

A couple of notes for you since you are 3D printing from your models.

Likely you’ll want to model at a larger size. When I model for printing I set the model units to meters and enter either mm or inches as appropriate. For example this crank handle for a drill press is supposed to be 95mm long.

Working that large allows you to create small details.

Here’s a grab of it in the slicer. It needs to have some support added to it, of course. This was just as an example.

If your slicer will let you define the import units you don’t even need to scale the model down before exporting. There are some slicers that don’t give you the option to set units, though. If yours is like that you will need to scale the model down before export.

As for the smoothness of the parts, here’s a comparison with the crank. The motor support bracket in the next images was modeled with smaller faces to get smoother surfaces. They are still faceted but it’s not as noticeable as on the crank handle.