If you are used to working in a 2D program like AutoCAD or if you’ve ever used Photoshop, you probably understand the basic principles behind using layers. Most people start using Sketchup expecting layers to perform the same way, but quickly find out this is not the case. This article will help you understand how layers work in Sketchup, and also show you why groups & components may be a better way to organize your model.
I should use Layers, right?
When modeling, there are two main things you want to have control over: Organizing the structure, and toggling the visibility of the different entities in your model.
Structural organization in Sketchup is handled using Groups, Components and the Outliner window. Groups and components allow you to take any number of edges and faces and place them in an imaginary protective “shell”. This shell allows you to move and manipulate a collection of entities at the same time, and the contents of a group or component become protected from other entities outside of their group.
Traditionally, the term “layers” is used in 2D programs for both structural and visual organization. You can turn layers on or off to control visibility, but they also provide a way to separate objects from each other by assigning them to separate layers. So naturally, when someone comes into Sketchup for the first time, they expect Sketchup layers to behave the same way. Layers actually have a very specific purpose in Sketchup, but it has no effect on the STRUCTURE of your model.
Layers will only change the visibility of an entity.
Think of it like this. If you are standing in a room and someone turns off the lights, can you still interact with the objects in the room even though you can’t see them? Of course! The same goes for layers in Sketchup. When you put something on a layer, it doesn’t isolate or protect it in any way. It only assigns it to a certain “visibility channel”. This allows you to “turn the lights on or off” on any combination of objects, depending upon which layer you assign them to. You can assign individual entities to layers, or better yet, assign a group to a layer and everything inside that group will inherit the same layer assignment.
Now here’s the kicker. groups & components have a built in “Hide” & “Unhide” feature. Coupled with the organizational layout of the outliner window, it makes for a very easy way to manage the visibility of your groups and components while you’re modeling. Since you are already using groups and components to organize the structure of your model (you better be!), why not use groups and components to organize the visibility of your model too?
Advantages of using Groups and Components for organizing structure AND visibility
- Organizing your model into groups creates a natural hierarchy in the outliner window that makes it easy to hide individual groups or parent groups that contain other groups.
- While modeling, sometimes you want to turn off visibility of objects that are blocking your view. Sketchup has a special feature called “Hide rest of model”. This feature will hide everything outside of your active group, sometimes preventing you from even having to turn visibility on or off in the first place. Creating a keyboard shortcut for that feature makes quick work of turning it on and off.
- By managing your visibility using groups, you prevent the need for having two separate organizational structures. Instead of assigning objects to both a group and a Layer, you would only have to assign them to a group.
- When you hide a group or component, switching on “Hidden Geometry” (View –> Hidden Geometry) will reveal an outline of all hidden groups. However, if you have entities on a layer that is turned off, they will NOT be revealed when you turn on hidden geometry. They will remain invisible until you turn that layer back on. They will also disappear from the Outliner window until you turn that layer back on.
Advantages of using Layers for organizing visibility
- Layers provide a way to assign similar items to a common visibility channel, even if they reside in separate, unrelated groups. For example, if you are modeling a house, you might put all the furniture on a layer labeled “furniture”. This way, you can quickly turn off all the furniture in your model with one click. Otherwise, if you hadn’t assigned all the furniture to a layer, you’d have to open up each group in your model and find all the furniture components and hide them individually.
- Sketchup scenes do not track hidden groups/components very well when they are nested into parent groups. For this reason, it is best to use layers when trying to save scenes of your model with different visibility “configurations”.
- UPDATE 3/17/13 via James Ogston from www.see-it-3d.co.uk James emailed me and brought up a good point about another reason to use layers. If you are planning on exporting your model to another program and you want to retain the organizational structure of your model, you might have to assign layers. If you don’t, all of your groups and components will show up as one object in the program you imported into.
Layers may not be necessary
After assessing your organization needs, you may find that you don’t need to use layers at all. Personally, I rarely use them. I do all of my organizing using groups and components. Just don’t make the mistake of thinking layers will isolate geometry. It’s only purpose is to control visibility.