Create hollow thick-walled spherical solid


#1

I am trying to create a hollow sphere with a thick wall. My approach is to create two concentric spheres:

shown here with a section cut to reveal the inner one. I group each sphere (hence the blue bounding boxes). When I try to subtract the inner solid from the outer solid, I am left with the outer sphere alone and no inner surface where the inner sphere used to be. Is this a bug or a misunderstanding of how subtract should work? Is there an easier way to create a thick-walled spherical surface?


#2

No bug.
Subtracting with the solid tools means youĺl be left with the space that the larger sphere takes.

To get a thick wall ‘SketchUp’s Solid’ you only have one group (or one component.
Within this group you’ll have two spheres, one concentric placed in the other.
Both spheres need to have their surface oriented correctly, the back faces “towards” the materal side, the inside of the wall.
The group will (should) show the correct subtracted volume in ‘Entity Info’.


#3

So it appears that when I create a sphere, it’s not a solid, but a surface. Does SketchUp distinguish between solids and a closed assemblage of surfaces? How do I know when I have a surface rather than a solid?


#4

SketchUp does not have true solids. Everything is assembled from Edges and Faces; the rest is empty space. However, it calls a complete surface that encloses volume and has no interior Faces a “solid”.


#6

Ah, that clears it up @slbaumgartner. And explains why subtracting the smaller sphere from the bigger one didn’t do what I expected.

So how do I check the orientation of the inner sphere to see if the “back” of the faces are oriented toward the outer sphere, and if they are in the wrong direction, how do I switch them?


#7

Right click on a (sur-)face and select ‘Reverse Faces’ in the appearing context menu.


#8

p.s. if the faces of both different shapes (both spheres) aren’t oriented the same way (back to back or front to front, you may and up with the sum of both their respective volumes When grouped into one single SketchUp Solid in 'Entity Info.