Advice for people new to SketchUp, but with lots of experience with 2d CAD


Continuing the discussion from Welcome to our forums! Please introduce yourself :slight_smile::

@woodystanford introduced himself in the thread above, and also described his experience: Lots of 2d using AutoCad, essentially none in Sketchup. There are some issues that come up frequently in this forum that trip up people coming “over” from AutoCad (and other 2d CAD programs). To get them off on the right foot, I’ve long thought we needed a specific guide just for them. I’m using Woody’s introduction as a starting point for what needs to be said.

SketchUp “Layers” are a completely different concept - and function - than what you’re used to in AutoCad!
In AutoCad, Layers isolate geometry. That is, what you draw “on” one layer won’t interact with what you draw on another layer. This is not true in SketchUp!!! Instead, in SU, you use “groupings” to isolate geometry (more later).

In Sketchup, Layers are a visibility control. Turn on visibility for a layer and you’ll be able to see anything assigned to that layer (unless it’s a grouping that has been explicitly hidden using the “hide” command). Turn off visibility for a layer and - poof! - anything assigned to that layer disappears from view.

To isolate geometry in SketchUp, use groupings
Groupings come in two varieties in SketchUp: “Groups” and “Components”. Both isolate geometry contained within them from geometry elsewhere in the model. Of these, Components are far more useful that Groups (in my opinion) for a few reasons:

  • Components can be named! This is incredibly useful when using the “Outliner” in the Default Tray to show the meta structure of your model. What groupings do you have? How are they nested?
  • When you make a copy of a component, they share a single instance of the contained geometry! So if you need to make a change in one, all others will reflect that change. This relationship can be severed using “Make Unique”.
  • SketchUp has problems with very small geometry (see below), but workarounds exist. The best workaround uses Components.

SketchUp is an edge/face modeler.
As such, it’s ONLY primitives are edges (don’t call them lines!) and faces. (OK. I just told a fib - there are other primitives, like dimensions, text, guide lines and guide points, but none of these are intended to represent real world geometry.) This has consequences that may initially upset you, but once you’re used to them, you’ll be OK:

  • A face is the area enclosed by a closed loop of edges - if the lines are all in the same plane. SketchUp autocreates faces when it detects such a closed loop. If you don’t want the face, you can then select and delete it.
  • Faces have two “sides” - Front and Back. They are displayed in two different colors. The default settings of these colors when you first install SketchUp are White for the front, and a light blue for the back. It can be difficult to tell them apart! - Especially as you start getting lots of small faces and orbit around your model. Most experienced SketchUp users change the default color of the “back” to something highly contrasting in the “Styles” tool - I use red.
  • Edges are always straight! There are no curves in SketchUp’s internal model. Everything your eye perceives as a curve is actually a connected set of very short, straight edges.
  • There are no curved faces in SketchUp! Although you will often see what you think is a curved face, it will actually be made of of many smaller, flat faces with their bounding edges hidden and “smoothed”

The geometry within a grouping can be assigned to a different layer than the grouping!
This is actually a good thing! The basic rule is this: Keep all edges and faces assigned to Layer0 (This is SketchUp’s default layer - and can’t be deleted). I’m not going to detail the many ways it can cause problems if you assign geometry to other layers - way too long for this already long topic!. By doing this, you’ll avoid some incredible headaches down the road. You can still assign the grouping to another layer and make it (and all the geometry contained within it) invisible by turning “on” and “off” the grouping’s assigned layer.

SketchUp isn’t very good for annotations, dimensions, callouts, text, etc.
Yes, you can add these in SketchUp. But these sorts of things are intended for a 2d space (like a piece of paper that contains drawings derived from your model) and really clutter up the view while you’re modeling.

Plus, you don’t have much control over where they appear - because they’re going to move as you orbit, pan, and zoom around your model.

If you intend to produce detailed drawings based on your model, get SketchUp Pro!
SketchUp Pro adds a few new tools to SketchUp, and adds the companion programs Layout and Style Builder. Layout is specifically designed to create professional drawings from your SketchUp model. Do you need to annotate, call out, dimension, or add text? Do it in Layout if you put any value on your time.

SketchUp Make is for non-commercial use only!
Did you choose to install Make because it’s free? Are you deriving ANY commercial benefit? If so, you are violating the Terms of Use and you should be using SketchUp Pro This includes ANY use of SketchUp in the context of a business.

  • You say you’re just using it to model possible office arrangements - that’s a commercial use.
  • You’re just designing a gizmo to organize/streamline/improve an internal process - that’s a commercial use
  • You work for yourself and you want to try to sell your models - that’s a commercial use
  • You want to put your work into the 3d Warehouse in order to attract clients - that’s a commercial use.
  • Etc., Etc., Etc.

Take whatever time is necessary to read the online documentation and work through the tutorials of the tools and features you anticipate using.
Don’t jump in and start by trying to model something highly detailed and complex! Start simple and teach yourself the basics.

I’m 90% sure that I’ve forgotten something else that’s important. When I realize what it is (they are), I’ll reply to this post with the addition. And I encourage other people to chime in with common “Gotcha’s” as well.

Looking for help creating some tutorial videos

Yep. Remembered one. And it’s one that was promised by a “(more below)” note in my original!

Sketchup has problems dealing with very small geometry!

Sketchup has an internal resolution of 0.001 inches (or is it 0.01? Somebody correct me!). When you do a number of operations where you’re either combining geometry or asking SketchUp to create geometry (push/pull, follow me, etc) and it results in points which are too close together, SketchUp merges them into a single point because their separation is smaller than SketchUp’s minimum resolution. This can cause - (ahem) - unexpected results.

There are at least two work arounds that I’m aware of:

  1. Model in large units. When I’m creating something for 3d printing, I model in Meters, but think in Millimeters. The most common format of 3d models that the 3d printing houses need is .stl - and .stl is dimensionless! So you model in Meters (while thinking in Millimeters), export the .stl, then specify the units as Millimeters when you upload the .stl file to the 3d printing house.
  2. Use components! If you have 2 component instances that are tied to the same component definition, then any changes in one are accurately reflected in the other. And you can scale component instances without breaking their connection with the component definition. So you have some tiny details you need to model accurately? Throw them into a component, COPY that component, use the scale tool to enlarge one of them by x10, x100, x1000 - whatever you need. Edit the enlarged copy - and the edits will accurately appear - at the original scale - in the original component.