Sketchup Smooth, Soft, and Hidden

Matt Donley News, Tips & Tricks 8 Comments

Have you ever been confused about the differences between Smooth, Soft and Hidden Edges? So have I! This article will give you a complete explanation of each edge type, and some examples of places to use them.

Sketchup Edges

An edge is any line segment in Sketchup. It can exist as a single element in a model, or it can be connected to other edges at intersecting points. When you have at least three edges connecting on the same plane, you can have a face. These are the core building blocks of every model in Sketchup.

Everything in Sketchup is either an edge or a face (Except for extra stuff like construction guides, floating text, dimensions, etc). I’m just talking about the geometry here. Even circles and arcs are actually made up of segmented lines (edges). There are no curved surfaces in Sketchup. But Sketchup does provide a few clever tools to give the illusion of a curved or smooth surface.

An edge can be in either one of three states

  1. Visible – This is the regular state of every edge. Self explanitory.
  2. Hidden – You can’t see the edge, and no edge styles will be applied to it while hidden.
  3. Soft – Same as Hidden, but adjoining faces will be selected as one

But what about Smooth?? Smoothing technically doesn’t do anything to the edge, it affects the appearance of faces that are connected to the edge. We’ll talk about that in a little bit.

Hidden Edge

The only thing that happens when you hide an edge is it will not “appear” on the screen. The faces connected to the edge will still look the same, but if you have any type of edge style active, hidden edges will not be “drawn”. You will not be able to select a hidden edge unless you go to VIEW --> Hidden Geometry.

I consider this to be the most basic way to manipulate the visibility of an edge. In Sketchup, you can hide any piece of geometry that’s in your workspace; edges included. You can hide an edge a few different ways. You can right click an edge and select “hide”. Or you can use the Eraser Tool(E)Eraser Tool on that edge while holding down the SHIFT key. The thing that’s nice about using the Eraser Tool is you can click and drag across multiple lines at the same time instead of trying to select each one individually. You can also look at the Entity Info Window while the edge is selected, and check off the “hidden” box.

To find the Entity Info Window, go to WINDOW -> Entity Info

Hiding an edge is a good idea when you have a shape with multiple non-prominent corners and lines that you don’t want see, but you still want to be able to select each face individually.

Soft Edge

By softening an edge, it does the same thing as hiding it, except the adjacent faces are treated as the same face. So if you click one face, the face on the other side of the edge also becomes selected. This is great when you have a rounded corner, or an organic mesh type of surface. This will allow you to treat all of the faces as one surface, which makes it easier to select and paint. If you need to select faces individually, you can always go to VIEW -> Hidden Geometry.

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To soften an edge, right click and select “Soften”. Alternatively, you can select an edge and check “soft” in the Entity Info Window. Or, use the Eraser Tool while holding down CTRL to Soften/Smooth multiple edges at the same time by clicking and dragging. Note: By using the Eraser tool in this manner, you are applying both the Soften and Smooth action to the edge. In most cases, this is the appropriate thing to do, but it is a source of confusion between what each of them do. Just remember that the soften edge only affects the appearance of the edge and forces the selection of multiple connected faces.

Smooth Edges

Hidden and soften are the only two actions that affect the appearance of edges. The Smooth edge action doesn’t actually do anything to the appearance or characteristics of an edge line. Smoothing affects the faces on each side of the “smoothed” edge. A Smoothed edge blends the shading characteristics of the two adjoining faces to give the illusion that they curve into one another. It tries to make the edges appear smooth, rather than sharp.

Now, with that said, it doesn’t make a lot of sense to have the faces appear to be smooth if you’re going to leave the edge visible. That’s why it is very common to use the Smooth Edges (affects the shading of the faces) with the Soften or Hidden Edges (affects the visibility of the edge) to achieve the full illusion.

By default, extruded circles and arcs will automatically soften and smooth the edges to make it look like it is a rounded, curved surface. But we all know it’s just a bunch of straight lines and faces, right? This is actually the only difference between the Polygon Tool and the Circle tool. Edges on extruded polygons are treated like regular edges.

There are times where you might want to soften an edge, but you don’t want the faces to smooth. Like in the picture above. If the edge was smoothed at the body line above the wheel well, you would lose a lot of the shape of the car. Just by making the edge line disappear, you can still see where the edge occurs, but it’s not as prominent. But the hood of the car is Soft and Smooth, so it gives the illusion of a continually curved surface, even though it’s actually made up of flat faces and edges.

It’s all an illusion

Imagine if you were to print your Sketchup model on a 3D printer. All of these edge characteristics wouldn’t matter, because it’s all just an illusion. They are little visual tricks Sketchup allows us to do in order to make the model look better on the screen. But the reality is even if an edge is hidden or softened, it’s still there. If you have smoothed edges (maybe they should be called smoothed faces), the faces don’t actually curve. They are still straight. So just remember that all of these tricks only affect the visual representation of your model on the computer screen, they don’t affect the structure of your model.

About the Author

Matt Donley

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Matt has been creating SketchUp tutorials since 2012. After writing the book SketchUp to LayOut, he conducted the "Intro to LayOut" seminar at the official SketchUp conference in Colorado. Matt writes about how to use SketchUp for design, construction and 3D printing.

Comments 8

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  1. Arie

    Thanks for sharing. I was so confused by this.

    So, if I made a Cone, and I want the edges around the flat base (the circle face of the cone) to actually be softened, so there is a curved edges, how would I do that???

    Please let me know and thank you!!!!

  2. Arie

    I meant, I think it’s better put that, If I wanted a bulged cone to be actually bulge, not just APPEARS to be smooth. How would I do that and what are thet steps?


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