Triangulation in SU



I like to try.


Check your PMs.


I have just published an extension, SB Trilateration, at SketchUcation based on the discussion in this topic. It solves both 2D and 3D trilateration problems precisely without the user needing to first draw circles or spheres.


Great help for surveyors.


It’s a huge improvement on everything that has gone before.


I’m using Triangle Tool, by Christian B. It works a dandy!




I have just downloaded and tested this extension. It’s certainly a neat way of drawing triangles. However, for mapping points in space, it has the drawback that you would have to go round afterwards eliminating a bunch of unwanted lines. For my purposes, SB trilateration is the better tool.


I wrote my extension to place guide points instead of actually drawing triangles for two reasons:

  • Provided the input side lengths yield any solution and don’t add up to exactly the length of the reference line, there are always two solutions. So if the extension draws a triangle, it must either draw both possibilities or somehow automatically choose between them. Drawing both is fraught with potential issues because SketchUp will cause the new edges and faces to merge with pre-existing ones, permanently altering them. I believe that Triangle Tool dynamically marks the vertices the user selects as A and B, and uses some rule such as right-hand circulation to decide which of the two solutions to draw. At the time, I didn’t think there was much effort saved by making the user remember such a technical rule (with the risk of having to undo and try again) vs just placing guides and letting the user draw. Maybe that was wrong? See more below.

  • There are use cases in which you only want to know the location of the intersection, you don’t actually want to draw triangles. For example, to know where to place a building using distances from ends of a baseline. There isn’t necessarily any geometry, let alone a triangle, joining the baseline to the building. It is easy to delete all guides without any impact on other geometry, much messier to delete triangles that are no longer needed - especially if they intersected other edges and faces.

It wouldn’t be hard to add a mode to my SB Trilateration extension so that it would draw triangles vs guide points; after all, it has all the required info. As noted above, the main issue would be to provide a simple way to control which solution is drawn. The vertex order-of-selection technique works but is perhaps a bit subtle and technical. Maybe a keystroke or click that would toggle between the two alternatives for a given set of data?


Not quite. Once you have input the line lengths for the two sides of the triangle that are not its base line, there is then the dynamic ability to select orientation. Clicking locks it. That is actually quite neat, at least for 2D trilateration.

As you have pointed out, drawing actual triangles that may then merge with other geometry and having to delete them is a pain when what you are trying to establish is actually a point. Your extension has the edge for me and of course includes the option of 3D trilateration. The only thing I might change is having to have two extensions (2D and 3D) in the menu rather than, say, choosing Trilateration and then selecting between 2D and 3D. It’s a minor point but could save clogging up the menu.


Guide circles and arcs would have the advantage that they can be realized without opening the pandora’s box and extending the geometric entity model (edges/faces).

A true guide circle would be no more than a inference target for creating classic edges/faces, but users would not be able to extrude or intersect true circles (which could creating infinitely complex curvatures that can not be represented by SketchUp’s entity model).


Ah! I hadn’t actually installed the extension, just took a quick glance at the code. That is indeed a neat solution to the ambiguity.


I’m not sure I understand. I deliberately put a single top-level item in the Extensions menu with two submenu items, 2D and 3D, to avoid cluttering the main menu, where it mixes in with all the items from other extensions. I guess it’s a matter of visual clutter vs minimal mouse clicks?

The extension also provides a toolbar you can show and choose which variation by clicking a single button.

And for the ultimate in quick access, you can set a keyboard shortcut to
Extensions/SB Trilateration/2D Trilateration
Extensions/SB Trilateration/3D Trilateration


This is how it looks on my screen:


Is it 'cos I is Mac?


Hmm…not Mac, there’s no difference in that between systems. I wonder if I changed that after I published it? Or are you using a pre-release copy I sent you? I’m going to have to take a look at what I put out on SketchUcation :lying_face:

Edit: the version on SketchUcation definitely uses the submenus.


Steve, here are some more screen shots in case it helps identify the problem. If I have an earlier version, do I need to uninstall it and then install the current Sketchucation one? I can’t remember how I uploaded it last time.



The fact that it shows as unsigned says it wasn’t from SketchUcation, as the one there is signed. You can just install from the Plugin Store over top of what you’ve got. It will overwrite whatever files are there.


Tried that but it made no difference. So I uninstalled the previous version and tried again. Still no dice. This is what the process looks like:

Now I no longer have any version. Any idea what I am doing wrong, Steve?


Let’s take this over to PM, as it seems to be specific to you and me.