Circle Tangent Tangent Radius fails on curves?

It seems that Circle TTR works between straight lines but not curves. The radius option produces no result.

In this example lets say we want to draw circles tangent to the original two and have a radius of exactly 7, 8, 9, and 10.

Am I doing it wrong ?

ttr.3dm (230.7 KB)

if you enter the radius before picking the second tangent point, it works


Thanks Diego.
How about now ? Can you do a 12.5 radius on this one ?
ttr.3dm (201.5 KB)

I can make something similar by hand but not with a precise value

hmmm- I don’t know if that counts as tangent for both curves - it looks like at best only one - either the curve or the line - can be tangent to the circle, am I right about that?


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Well, if you use the Circle TTT command it will dynamically display circles tangent to both, but it will not let you define a radius explicitly.

Right but… only one side gets what I’d call tangent. The other curve is tangent to a cylinder made from the circle - but the tangents are out of plane on the circle and just the curve,

ttr_PG.3dm (228.2 KB)


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I see it and strictly speaking, you are right; in this scenario there is no true tangent in a 3D sense.

Is there a way to force an “Apparent” tangent from (say) the top view only ? (Maybe that’s what my brain was going for subconsciously). It seems the Circle TTT is using the apparent view to draw its dynamic suggestions in the first place, can we make that official somehow and allow to specify a radius exactly ?

This idea came up while trying to fillet these edges. I did it using other methods, but I thought it would be interesting to have an apparent-tangent-fillet-something thing.

fillet.3dm (238.3 KB)

Hi Thomas - there is an ancient vb script here that, rather awkwardly, does that if you extract the edges first:
Looks like there is still some debugging curve color changes in there as well.
I’ll see if I can’t pythonize that so it flows a little more smoothly.


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Good find ! Thanks.
Somebody must have asked for it in 2011 :slight_smile:

(PS don’t tell me 2011 is now ancient, I thought Rhino V1 was only a couple of years ago).

‘Ancient’ , here = I can’t remember much about it, it could be dumb & junky code.