Best strategy to complete this shell from solids


What is the best strategy to make a shell from these intersecting solids? I’d prefer to learn how to manually create the finished shell rather than use plugins so that I can build familiarity with the fundamental tools of Sketchup.

Many thanks.

Shell-Solids-0.0.1.skp (152.4 KB)

If you want to use Native tools, I would suggest making a copy of the entire thing. If you only have the originals, you won’t have anything to fall back to if you wreck things since you’ve used groups instead of components. Then explode them, select the geometry and use Intersect Faces to create the intersections where the faces cross. Then use a combination of Select/Delete and the Eraser tool to get rid of the unneeded geometry. I would probably explode two groups to start and work on them. Then explode another one and repeat the process.

By the way, you might want to soften the edges on the central group before you start exploding and intersecting.

By the way, what short of shape are you really after? Is it supposed to be something like I show on the right?

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Yes! I tried 50 different ways to get there but none were successful. Do you mind sharing how to get there?

Re above suggestion to intersect component by component, I separated into components then started with two. Resulting in some geometry I couldn’t get rid of.Vertical-Long Axis 1-Intersect.skp (185.1 KB)

Evidently you didn’t get to the fifty oneth way.

I didn’t use Intersect Faces at all. Instead I used Follow Me. I started by copying the curve profile from one of your straight sections as well as the bottom “oval” from that group. In order to get a workable path for Follow Me I used Offset to create the smaller oval inside. Note the vertical guideline is aligned with the top end of your profile and intersects the side of the small oval.

Then I selected the path, got Follow Me (I use a keyboard shortcut) and clicked on the profile.

FWIW, if you use the larger oval as the path, the resulting extrusion needs a bunch of cleanup that isn’t required with the way I show above.

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Well huh. I tried follow me so many times, so many different ways, but probably didn use the inner offset. I’ll try it when I get back!

Thank you!

Not using the offset aligned with the vertical guide was the problem. I am ashamed at how long it took me to accomplish this shape. Thanks again.


No need to be ashamed. It took me a few tries with Follow Me before I first figured it out. If you really analyze what is happening during the extrusion, it starts to make sense and you get where you can sort out the right location for the path from the beginning. As far as that goes, many times it’s not a problem, too.

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Following the inner offset has made the outline of the base “oval” not match this part’s mating part. This Is destined for 3D printing for prototyping. There are also tertiary parts that this shape must fit inside but not attach to. Is there a simple way to select the bottom perimeter of the resulting shape so that I can redesign the mating pieces?

You can select the bottom edge but modifying the shape may be difficult depending on what the modification needs to be. It might be easier or more appropriate to change the shape of the smaller path. Or maybe yet another approach is required. Maybe an extension like Curviloft would be in order. Especially if the top shape and the bottom one need to be different.

SketchUp’s follow-me algorithm works by creating a copy of the profile at the end of each edge of the path and then attempting to create edges connecting corresponding points on the two profile copies. Problems arise when the path has sharp interior corners or tight curves compared to the size of the profile. The two profile copies “fan in” and can cross each other. That breaks the logic to connect the profiles, leaving a mess. If the corners are exterior, as when you follow your inner path with the profile outside it, the profile copies “fan out” from the sharp corner and don’t cross each other.


Maybe the parts need to be modeled all together to be sure of a good fit.

Selecting the bottom edge appears to do the trick. The mating pieces look like they came out ok. Thanks again so much.

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Right. That’s the path I’ve chosen. By the way, the shell shape was modeled using that strategy to match the existing parts. The resulting shape of the shell was different than the mating pieces. It is now easier to remodel the mating pieces to match the shell than the making the shell shape fit the mating pieces.