Individual Solid Groups Combined as Simple Group

I thought I understood solids, but maybe not.

I have two objects (rectangles, 1.5" x 3.5" x 24", not that this matters). I create the first one and group it. As expected, entity info tells me it is a solid group, ok, no surprises here. I move/copy and create a second instance (entity info reports solid group, 2 in model). It is also a solid group. I join the two individual solid groups and create a new combined group. This new single combined group is reported as a plain group, not a solid group. I then explode the combined group and again have two solid groups, but this time entity info reports each solid group as 1 in model.

Still with me? Now the questions:

  1. So, why after the grouping/ungrouping did the two single solid groups become unique when they started as identical?

  2. Is it possible to have two objects (each an individual group) combine to form a single solid group?

Thanks in advance for your help !

Another twist …
If I copy/paste, then after exploding, the individual groups are back to being identical. Entity info reports each as 2 in model. Strange !

SketchUp does not consider a container (group or component) with nested groups to be a solid. Depending on what you will do with the model, that might or might not matter. For example, some slicers for 3D printers are happy with nested groups.

Any edit of either group will cause them to become distinct. I’d have to guess that nesting them and then exploding the container was deemed to be an edit. Can’t explain the twist, though.

Edit: on further check, I can’t reproduce the made unique effect either. I made a box, made it a group, used move-copy to get two, grouped them, and then exploded the container group. I get back two copies of the same solid group.

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A Solid Group or Solid Component may contain one or more separate airtight solid vessels.
But it must all be raw geometry. No nested Groups or Components.

A Solid in SketchUp is a single Group or Component whose geometry meets certain conditions.
When those conditions are met, Entity Info indicates the model is a Solid Group or Solid Component.
Also notice Entity Info indicates the Volume of a selected Solid.

• The geometry must form a single* airtight vessel.
Like a perfect soap bubble … •No gaps •No holes •No leaks

• No extraneous Faces** inside or outside the vessel.
All Faces must serve to enclose the singular volume of the vessel.

• No stray Edges.
All Edges must serve to support a Face that in turn serves to enclose the airtight vessel.
Thus, each Edge supports two Faces … no more, no less.

• No nested Groups or Components.

*A Solid Group or Solid Component may contain one or more separate airtight vessels.
**Best that all Faces are oriented Front Side (white) facing out.

Understanding Solid Objects in SketchUp — Aidan Chopra
Programming & Web Design Articles - dummies

Solid Inspection/Repair Tools

SolidSolver by TIG

Solid Inspector² by ThomThom²

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So, as I thought, I am in a catch-22 position.

I use the Medeek extensions. These extensions create nested groups. I find models where I have to edit the nested groups. Once I make the edit, the extensions will no longer see the entity as it’s own, and I cannot use the robust editing tools of the extension. More so, when exploded, the entities lose their solid characteristic, and the solid tool set within the extension will not work.

I tried taking the two objects, joining them, removing the groups, exploding and then re-grouping the two now joined objects. Entity info states they are just a group, not a solid group.

Maybe my approach is flawed.

Solid from two

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When you say you joined them, do you mean they are intersecting each other? That would stop it counting as a solid unless you made an outer shell of the combined object.

Another thing that could be happening is you have tiny faces that can exist in the group, but are lost when you explode it and it will never count as a solid again. If that’s the case you’d have to scale it up, then down again to avoid this.

Could you show us the actual objects you’re using?


Box and McGordon, I did not save the file. The two objects were simple rectangles (described in original post above). Actually I was thinking about two 2x4s. I joined them by intersecting one common side via move.

Your objects are not touching, mine were.

Did you remove the common face!?

No, I simply exploded and then selected everything and made a new group.

I interpreted this as two separate airtight vessels.

They are one vessel with an internal face. You can’t have any internal faces.
Put the two together and use Outershell.

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What does the word mean?

Well, after I made a group of the two exploded objects, I then exploded again and separated into the original objects. Which led me to believe I was dealing with two objects.

True. They must be separate and all raw geometry.

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I’ve had enough of guessing what you are doing.

Very sorry for wasting your time, have a great day and thanks for the information. As I stated above my approach must be flawed. You are correct to point that out.

What matters, in the interest of saving time and frustration, is communicating precisely what you’re working with and what you wish to accomplish.

Forcing us to guess does little to hep us help you.
Kindly build and share with us a simple model that illustrates the issue.


@EosDawn, you would be wise to add the extension, Solid Inspector “found here”, to your arsenal.

That would help you discover flaws in your solids.

Sort of a similar problem here. I can make solid groups and/or solid components from the individual “pieces” of this model, but when I explode all and try to make a solid group/component out of all, i am unable to make it a solid, thanks for any help!

Edit: Wait a minute! Just tried Outer Shell and it worked to make everything one complete solid!

ask_experts_why_not_solid.skp (355.3 KB)