Best way to join complex solids with a radius

At work, I import components from others that are probably produced on ProE and I import a .STP file. In an effort to cleanup the file (better appearance, reduced file size, etc), I end up reproducing the component in SU. I also find that this endeavor has taught me a LOT about how to operate in SU.

In any case, I am trying to figure out the best way to produce a nice radius where 2 complex solids meet. I know how to get a path where faces intersect but I don’t know how to get a nice flowing radius (or fillet) where they meet. The first picture shows my basic solids. The second is the desired result (as imported from my vendor with hidden lines visible).

The closest I can think of is the Round Corner plugin. Have a look at these 2 examples. They were taken from the Take the Edge Off: Round Corner article from SketchUp Blog.

If you’re ok with this result, you can go ahead and download the plugin from the SketchUcation website here.

  • Please mind you need the Fredo Library installed before you can use the Round Corner.

I highly doubt this plugin will work. Following a 2D path (like a straight edge or an arc) is simple enough without a plugin. You can see that I already rounded the edges of the cubic solid. The problem is when you want to round a twisting, turning 3D path that you get at the intersection of two solids with complex curves.

Could you share the SKP file or at least the part of it shown in your first screen shot?

The files are big, so they are on my DropBox. I removed identifying info from the original. On a side note, can anyone explain how in the world my recreation has a larger file size when it has WAY FEWER entities (lines, faces, etc)?

Sorry. Bad example. A purge knocks it down to almost nothing. I do have this issue on other files. I will get a .STP file from a vendor, I import it into SU, and the file size explodes.

Fredo’s Rounded Corner does a great job. Of course, you DO have to intersect the two solid, first. I scales the whole thing up by 10x, used Outer Shell to merge the two solids, then selected the line at the intersection and ran Rounded Corner:

I did have a little bit of cleanup to do at the corners, but it was pretty quick.


All programs have ways of ‘optimising’ file size, but at the end of the day it’s down to edges and triangles when you export to a different format…

Unless the exporter/importer knows each others tricks you will get a bigger file…


I tried RoundCorner as suggested by you and Aaron. It does okay if you make the rounded area small enough to kill overlaps. If you look at the original file, the radius at the intersection is about 1/4" which results in 26 or more overlaps according to the plugin. Plus the result does not actually intersect with the larger solid in several large areas (the complex curved barrel). So, you end up trying to correct all of the overlaps and non-intersecting areas by hand (impossible).

1/4" radius is small enough to run a risk of issues due to SketchUp’s failure to create small edges. Did you scale the model up before trying this?

Yes. It doesn’t matter what scale you use because you have to scale the radius as well. A 10x scale means you have to use a 2-1/2" radius (100x = 25" radius), all resulting in the same number of overlaps and surface border issues (non-solid).