_Arc -- doesn't snap to intersection

when using _Arc (center,start,angle) , i’m unable to get an intersection snap where the arc’s path crosses another curve (or edge etc).

i feel like i used to be able to do this in rhino but it doesn’t work for me anymore (though it’s possible i’m confusing rhino with another software regarding this)

so, this is either A) a feature request or B) a bug report. (or C-- a “is anybody else able to do this and i’m just doing something wrong?” question)


I don’t recall ever having been able to do this, although admittedly I haven’t tried much. Would be a cool feature though.


I don’t recall it either- it would, I suppose, need to be ‘special cased’ since there is no arc in the document to intersect until the command finishes. The same fails on the second point on Line, but it works if you establish a fixed line with tab or SmartTracking to intersect with the existing curve.


actually, i know what i’m confusing it with now… when rotating an object, you can get an intersection snap with a different curve.

so yeah, i guess it’s a feature request-- make Arc work similarly to Rotate in regards to the Intersection osnap. (seems like the same maths would be involved to get it working?)

Ah, Jeff
So you want to activate Osnap (intersect in this case) as if the object in command has allready been constructed. Very neat feature… such would be. For now you simple draw it twice:

  1. with extended version
  2. the same with the intersect active
    Sure you know this or just trim the extent piece of arc. (I do it both depends on the mood I guess)

Well, I would suggest there to be Ext option toggle in the Osnap pannel (Ext stands for Extension). Or Osnap → Apparent Extension (like it is with the Apparent Intersect)… just to be optional.

Or, making a circle, followed by SubCrv would also work, as a workaround of sorts.


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Oh, I forget all the time about SubCrv – very powerful command, works with curves of higher degree which is great.

it’s not that odd and we see the behavior elsewhere in rhino…

again- just look at the Rotate command… it does the same thing i’d like to see in the arc tool… in this example, it has nothing to do with whether or not geometry has already been created… i’m not even clicking on the geometry-- just a random mouse click…

(maybe confusing at first to understand the drawings :blush:)



to me at least, it seems like the Arc tool could do the same thing.

As I said, my guess is it could too- once the center and radius are known, a circle is defined that can be intersected with existing curves- at least, that is my guess at how this stuff works in Rotate and when a some line is defined like with Tab. At any rate, I’ll add it to the heap of things to check into for V6…



Yeah, Jeff
You are absolutely right. I haven’t noticed this double behavior of the Int option of Osnap.
Well, Rhino seems to have the features for many good things. Just appears to be not so good optimised I guess.

Similar to the WireCut compared to the Fillet for example. Just for the experiment:
could such “hidden” features be activated with scripts (Rhino, Python) maybe?


my guess would be that a dev might see the benefit of a feature in a certain command so they get it working… but with 700+ commands, it could be difficult sometimes to immediately recognize other operations where the same benefit could happen…
once it’s in the hands of thousands of users, they’ll start making the connections then gripe about it here…

or something like that :smile:

Hi Jeff, all - this works in V6 now.



ha! nice.

I’m not sure if I should hang around here when mcneel starts the v6 public beta.

it will probably make me start considering boot-camping my computers :smile: