Show the Radius when drawing an Arc

When drawing an Arc, the information given in the Measurements box shows either the Bulge or the Length, Followed by the Radius.

I dont find “bulge” particularly helpful. Radius is more informative to me.
Can the measurements box show both Bulge and Radius?

If not in the measurements box, then how about a dimensioned arm on the actual arc?

The Dimension Tool can give you the radius or the diameter of the arc.

But that is only “after the fact”.

As I understand the feature request it is to show the radius (for example as a tooltip as illustrated) while the arc tool is “in progress”.

And possibly to be able to specify the radius rather than a bulge value.

Thanks for this suggestion; we are investigating some ways to make tangent arcs quicker and more predictable to draw, so this idea is relevant to what we are working on.

Have you looked at how the 3-point Arc tool creates arcs? In this tool, the radius (and implied pie section) are previewed when the tangent inference is active. However, we are not yet showing the exact radius or allowing you to define the arc you are creating by its implied radius. @AK_SAM , Can you share a bit more about why the radius is a more informative or useful way to define the arc length?

The radius can be specified while drawing an arc. If you enter the letter r before or after a numerical value it will be used as a radius instead of a bulge. For example r1000 or 1000r.


I didn’t know that. Thanks.

Not to disagree with the feature request, which I think is a good one.
It’s worth pointing out for the people that will inevitably read this thread that you can specify a radius by using the magenta inference.
Draw any arc to the magenta inference, click once, move back along the edge until you get magenta again(don’t click), type the radius you want and hit enter.


In my projects I often set-out urban streets, footpaths or landscaping (eg lawns, retaining walls). These need to adopt a mininum radius (horizontal and/or vertical). These use linked arcs (then an offset to create the other side).
There’s an element of design creativity to this process, eg following a stream edge, or going around a tree, or tracing over a topographical contour line.

I’ve also done modelling in the past that showing pipework, cables, or fencing & balustrades etc, which also use a minimum radius as a key input to the process.

I’ve actually never used bulge - can’t even think what that could be useful for.

I like the simplicity of the arc tool & so don’t want to add a lot of complexity. My favoured approach is for Sketchup to just report on the radius while it is being drawn (using the measurements bar).

A nice addition could be to specify a precise or a minimum radius prior to drawing it… John pointed out that you can type r before the number - I didnt even know that so will try that next.

& Yes I do use all the 3-point arc tools and what Box shows with the chamfer radius (@box it still works if it’s not a tangent (magenta) arc)


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Actually, it was Jean Lemire (@jean_lemire_1) who should get the credit for that - I didn’t know it either.