How to find a line that is slightly off plane?

Several times I have imported a jpg of a floor plan, then started outlining the walls with the line tool. Then using the rectangle tool I start filling in the elements, such as a future coffered ceiling. Then, magically, the rectangle tool stops working. My guess is that it is no longer on the same plane as everything I have drawn. Perhaps one line goes up or down, and the rectangle tool stops working because there’s a twist or something.

What is an easy way to fix it? What is a way to force all of what you draw, before pulling it into 3D, onto one flat plane?

Thanks G

The rectangle FAIK does not stop working when dimensions are large enough. (more than say 1mm x 1mm). It always produces two pairs of parallel edges, all coplanar and at 90 degrees, filled in with a face.

SketchUp 2015 has a ‘Rotated Rectangle’ tool but this is not the one you should use here.

If you import a jpg floor plan, then there are several hints that SketchUp can give you when drawing in the jpg. Dragging the rectangle on it shows:

  1. On Face in Image (jpg imported as image)
  2. On Face (image exploded into basic geometry, four edges and a textured face)
  3. On Face in Group (geometry in (2) has been grouped again)
  4. On Face in Component (as 3 but the grouped geometry is a component rather than a group)

If you are too hasty in dragging and clicking, then SketchUp may not be able to find that inference ‘On Face…’. Once there are some endpoints out of plain, then SketchUp may even start inferencing on these points. making things worse for you.

For starters, set your camera to parallel projection and shift to top view. Then when you import the image it should go exactly onto the z=0 plane and the lines you draw should also be all on that plane. You can rotate to a different viewpoint or change to perspective camera when you need to start adding 3D elements away from z=0.

One quick diagnostic would be to group everything that should be flat and then scale it vertically by a really large number. That would make the offending nonplanar geometry easier to identify. Just remember what you scaled it at so you can scale it back down.

Otherwise if your geometries are more complicated than flat geometries, I’ll just start drawing triangles between what I think should be coplanar edges. Once the offending end is identified, you can move it and infer the plane it should be on.

Third thing is to turn on hidden geometries. Sometimes hidden folds just happen. In this gif, I am tapping the “up” arrow key to lock the corner move in the blue direction when I reference the slope from the upper right portion of the roof.

Just thought of another diagnostic. If your model is orthogonal, you can set your edges to be colored by axis from the Styles dialog window. In this example, the offending line should be green.

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Good suggestion about scaling it up vertically, but you needn’t remember the scale factor because you won’t need to scale it back down. Once you remove the offending geometry, it will already be as flat as it can be.


Ha! Good point Gully. I was over thinking that.

There’s a bit more to it.
A selection may not show the middle grip to scale in vertical direction. You’ll then need to add and include a short vertical edge to the selection, to be able to scale in the Z direction, to then see any non-coplanar “horizontal” edges. (edges that were supposed to be horizontal). Also this calls for grouping the selection, as mentioned, (if not yet done so) to make selecting easier.
So far so good.
But once you’ve corrected the incorrect endpoints to make them coplanar, … and deleted the added vertical edge, don’t forget to reset the scale. Basic geometry and grouped selections “may be” (=are) flat but groups and components still have a scale definition other than 1 hanging on them.

Example: a rectangle on the ground with one corner lifted 0.076mm still does not reveal its erratic Z location. (no hidden diagonal) And the “rectangle” does not have a grip in it’s selection to scane it. some extra ‘out of plane’ geometry (vertical edge) is needed to be able to scale it.
Group everything and scale twice with 100x. In the group delete the vertical edge and move the corner in plane. leave the editing context. The group has “Restet Scale” available. If you forget to reset (be aware that all component instancs then inherit the new scale!) you may get into trouble later on. Or Scale down twice with 0.01x

Set units precision to six decimal places and use the native Text Tool.
By default, Leader Text displays the coordinates of an endpoint.

Or try either of these handy little extensions:

Utilities Tools — Extension Warehouse
Provides the Query Tool

Export Vertices to CSV v1.3 by TIG — SketchUcation Pluginstore
Exports all Vertices is a Selection to a X,Y,Z ‘CSV’ file.
Launch from File menu or Ruby Console

Wow what a pain in the a$$ this is.
Been spending more time on fixing the little problems that crop up than making my model.
This kind of BS really makes 3d modelling tedious and unfulfilling.

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Forgive me for saying so, but SketchUp’s inferencing system should make it easy to keep everything properly aligned (even accounting for the huge range of what “properly” means in different contexts). This is one of SketchUp’s greatest features. If you pause for about a half-second when positioning the cursor, you give SketchUp a chance to provide feedback if that position is on an endpoint, a midpoint, somewhere along a line, or on a face (i.e., flat plane) or surface (i.e., curved set of adjacent faces), etc. and to automatic snap to positions such as those. SketchUp is “inferring” your intent by performing that snapping adjustment to your position. It works remarkably well.

Yes. It is a pain when you allow the model to get sloppy and out of your control. Fortunately models don’t have to go that route. It’s entirely possible and not at all difficult to stay in control and create clean models. It takes some discipline but the payback is well worth it.

A lesson that many of us have learned the hard way: you may have to proceed a bit slower and more cautiously, but in the end it is faster and easier to avoid getting small errors in your model than finding and correcting them after the fact!

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I try to keep things on a plane but sometimes it goes haywire. It isn’t just on tracing lines on a pdf with a line tool and finding they aren’t on a plane when you connect the last dot. It is a bugaboo on some other surfaces when you are drawing stuff after having pulled up the walls, such as ceilings and roofs. Then you find the error has compounded.

And finding where it all went to heck is a trying task. It is difficult to find the out of plane errors, because they can be microscopic. It gets worse when you make changes to the model and find they weren’t on plane.

I really wish there was a tool that would slam the model to 2d prior to pulling up the walls. Or one that changed colors of the off plane line so you could find it easier. I have tried that diagonal line bit and it isn’t always the easiest thing to do. For example, I was trying to find the area of an irregular pond. So I am tracing a photograph of the pond using arcs, and the freehand tool. It was exacerbating to find the out of plane errors.


There are several that can do this. Search the Extension Warehouse and the SketchUcation plugin store for “flatten”.

This is more of a problem because of the computer’s finite precision arithmetic. How far off plane must a line be before it is colored? The existing “color by axis” setting for edges illustrates the problem: it works to within a tolerance and can miss edges that are only a tiny amount out of alignment.

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Isn’t this why we use computers? To keep thing correct and true? If a 3D modelling program can’t do that then I am not sure why we are wasting our time with them? I could have been done in a couple of hours with a pencil, ruler and paper.
Just spent 12 hours on my Sunday to work on a project and the last four are not showing up on my project today.
I am afraid Sketchup is not ready for use with the public.

Some of the public certainly.


You’re quite right, pencil, ruler and paper are much more advanced tools to work with than a computer program. You’ll not even be bothered (on paper) with the little mistakes that you talk about when working with SketchUp. For you won’t even be able to find them on your drawing board.
Yeez, stupid programs they make these days.


I agree. These programs are pretty stupid if they are as troublesome as they appear to be.
I thought we were over the era of Windows 95.

It sounds to me as if you just aren’t ready to use a computer to design your projects. That’s fine. There’s nothing wrong with using paper and pencil. It has worked for hundreds of years. Computer aid design isn’t for everyone. But your assertion that SketchUp isn’t ready for the public couldn’t be farther off base.

Thanks for your opinion but I have been using Sketchup for years with little problems so I doubt, I am the problem.
I also want to point out that your comment states the problem with CAD. The AID is left out. When the user has to figure out all of the problems that the computer has not corrected, there is no aid left.
When people are satisfied with a system that does not correct for the human condition, that system is not helping us. It is hindering us.
You want to hide behind that. No problem, but don’t forget that other systems are well on their way supplementing for the human condition.
“Farther off base”, I don’t think so…