Components and Layers in Google SketchUp

An Eccentric Anomaly: Ed Davies's Blog

I've been doing some redrawing of my house designs in Google SketchUp. SketchUp is generally pretty well thought out and impressively clever at working out what you want it to do except the odd occasions it isn't at which point it can become seriously frustrating. Here's something which has a simple explanation which took me a while to figure out.

SketchUp has a fairly simple notion of layers: a scheme for classifying the lines and planes in a model to allow them to be switched on and off for display in a systematic way. This is really handy if you want to be able to remove parts of a construction to show internal parts: put the walls or whatever on a different layer and turn them off to see inside.

The problem with this is that the surface which forms the interface between two building components has to be on one layer or the other. In one case I had each of the gable end walls on its own layer (actually set of layers) and north and south roofs on other layers. Where they abutted the interface needed to be on one or the other layer. Put it on a gable layer then turn those off and you're left with a roof with a hole in the bottom. Put it on a roof layer and then turn off the roofs to see inside and you're left with a hollow looking gable end.

You can't have two surfaces on different layers occupying the same space. I suppose you could create the two surfaces then carefully place them 0.001 mm apart or something but that seems like a lot of messing around.

The answer is to model each real-world object as an object, called a component, within the drawing. Components can consist of multiple lines and planes which are moved and generally manipulated as a group. The neat thing is that planes in different components can be put in the same place but be kept separate from the point of view of layering.

Here's the bit that got me rather frustrated, though, and seems worth writing up. Components can be put on layers and you can turn those layers on and off so the components appear and disappear as you would expect. However, the individual lines and surfaces within the component remain on their original layers and will disappear if those layers are switched off. In essence, parts of a component are displayed iff the part's layer is switched on and the component's layer is switched on.

This was not immediately obvious to me: I thought it was just that I was having difficulty assigning instances of components to layers. Working out what was going on was not helped by the fact that I'm running SketchUp under Wine on Ubuntu. This works pretty well but often seems to be one step behind in updating the display which can be very confusing when something else is also not working exactly as you expect.

The solution I've adopted for now is to put all the parts of components on a “Component Component” layer. That's kept switched on almost all of the time but it is handy to switch it off to see if I've left any detritus in the drawing which is not part of a component.

Update: 2014-01-05: More on this general subject at SketchUp Components and Groups