Group & Layer question for newbie

As a newcomer I am currently trying to understand how groups/components and layers relate to each other. I have studied many video tutorials & postings and am getting better, but strange things still do seem to happen.

As an example in the attached file, I have assigned four different groups to four different layers, but for some unknown reason when I toggle layer 1 off and on, it turns a group off that has not been placed on layer 1. Can anyone tell me what I’m doing wrong?

Group & Layer Question.skp (494.3 KB)

You have made the classic mistake of associating the edges and faces in your groups with layers other than layer0. In particular, the edges and faces of the numeral 2 group are associated with layer1!

It is not necessary to use the same layer as the group for its contents, as making the layer of the group non-visible will cause the entire group to disappear regardless of what layers the edges and faces use. But, in addition, when the layers are criss-crossed, as in your model, confusing things happen! Edges and faces should always be associated with Layer0.

You have put all the geometry (faces and edges) in the numeral ‘2’ on Layer 1. So when you turn off visibility for Layer 1, the number ‘2’ disappears too.

Perhaps you exploded the group after assigning the group to Layer 1? That’s one way this can happen unexpectedly.

Anyway, open ‘2’ for editing, select all, and reasign the geometry to Layer0 - which is where (with extremely rare exceptions for advanced users) it should ALWAYS be assigned.

Steve got there first!

PS. I see you’ve made the same common mistake, and ALL your faces and edges have been assigned to layers. Don’t do that in future, to prevent the same kind of confusion in future.

You’ve managed to assign the group which forms the number “2” to Layer 2, but you’ve also assigned the primitive geometry (faces and edges) that actually form the number “2” to Layer 1.

So when you turn off visibility of Layer 1, you also turned off visibility of all the geometry contained in the number “2”. So the grouping that organizes the number “2” is visible, but the actual geometry is not!

I made the same sort of mistake when I was a noob, so don’t feel bad about this.

The general rule of thumb is: Keep all primitive geometry on Layer 0! And always keep Layer 0 visible and the active drawing layer. The only things that should be assigned to other layers are the containers (groups and components) that serve to associate a set of primitive geometry together. Containing geometry in groups and components also prevents the geometry from interacting with geometry in other containers or uncontained (“loose”) geometry.

There are, of course, exceptions. You can do some fancy control of what is visible if you have nested containers with the outer containers assigned to different layers than the inner containers. Many people also put dimensions, text, and layout lines in their own layers - but none of these entities are considered to be “primitive” or “raw” geometry. I actually hesitated before outlining these exceptions (there are more) because, as a newcomer, you’re far better off adhering fanatically to the general rule - and learn about how the exceptions can be useful only if and when you encounter a modeling situation in which breaking the general rule makes sense.

To “fix” your model, double click on the letter “2” to open for editing, then “Select All”, right click for the context options and select “Entity Info”. In the resulting dialog, pull down arrow to the right of “Layer1” and select “Layer0”.

You should do the same for each of your other letters - that is: reassign the geometry to Layer0 while leaving the container (group) in your preferred layer.

Thank you Steve & John,
I just had done a little more searching and found exactly what you have explained to me! I see now that I need to keep the primitives on layer 0, amongst other things. I feel I’m on my way to wrapping my head around this stuff…I come from an AutoCAD background so I have to rethink all of this.

Don’t think of layers as layers. The hierarchy of groups and components (shown in the Otliner) works similarly to layers in most other programs. Each group/component has its own drawing context where primitive don’t merge with those in other drawing contexts.

What SketchUp calls Layers does not define drawing contexts but is just a way to toggle visibility. Some people prefer to call them Visibility Tags instead of Layers since they really are tags or classes applied to entities, not contexts the entities are placed on. Layer0 is fundamentally different from the others. It’s a “layer” you can never delete or rename. In my view “None” is a more explanatory term than Layer0 because it really means no specific “layer”/tag is applied.

I hope this helps understanding layers in SketchUp!


Thank you…
Wow this aspect of SketchUp is deep! I think your description is helping me grasp the concept better, but I might call on you again if necessary.

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