tangent circles between 2 curves

Hi,

I might be asking for the impossible... but I'm looking for a definition to do the following.

- it starts with a circle that can be predefined; in this case, the largest green one on the left.

- from there, I want a circle that is tangent to the top curve, to the bottom curve and to a circle that is 2/3 (or some other factor, I imagine a slider here...) of the diameter of the first circle

- and so on, until the end of one of the black curves is reached...

I don't even know where to start with this - any ideas?

Thanks very much, Michiel

Replies to This Discussion

Permalink Reply by David Rutten on December 5, 2011 at 3:12pm

Hi Michiel,

quite tricky. Rhino has a Circle TanTanTan fitter which is used inside the _Circle command, but this algorithm is not available to plugins as far as I'm aware. One of the reasons might be because it is such an underdefined problem. The Circle command requires the user to pick with the mouse and from this information a lot can be inferred. I'll have a look at the command, maybe I can harvest the algorithm (don't hold your breath though).

David Rutten

david@mcneel.com

Poprad, Slovakia

Permalink Reply by David Rutten on December 5, 2011 at 4:05pm

I got the relevant function into RhinoCommon, so now I can use it from Grasshopper. It works (see screenshot) but the problem is you need to specify three starting points that are reasonably close to the final solution. Reason for this is that there might be a lot of possible solutions and Rhino needs a good place to start looking.

I might be able to invent these starting points automagically based on other input (such as a point near the desired circle center, or a guide circle or something) but that will require further testing.

This function should be available for Rhino5 in the next beta (should be tomorrow evening) and for Rhino4 come the next Grasshopper release, for which I have no schedule. If you get tomorrows Rhino5 beta, you'll be able to run the VB component in the attached file.

David Rutten

david@mcneel.com

Poprad, Slovakia

Attachments:

CircleTTT.gh, 4 KB

Permalink Reply by Michiel Cornelissen on December 5, 2011 at 5:30pm

Really fantastic of you to look into this so quickly, David. i didn't even need to hold my breath, turns out. It looks great, hopefully tomorrow I can have a go at applying this!

Permalink Reply by Michiel Cornelissen on December 9, 2011 at 1:57am

Just downloaded the latest Rh5 build, but I'm not getting the script to work, I'm afraid... I do get a message about something having been made in a newer version of GH (I have 0.8.0061, that's the latest publicly available, right?) - could that have something to do with it?

Permalink Reply by David Rutten on December 9, 2011 at 3:07am

I'm using Grasshopper 0.6.0082 because I'm working on that one now. However apart from the warning the file should still open because I didn't break forwards file compatibility for this release.

David Rutten

david@mcneel.com

Poprad, Slovakia

Permalink Reply by Michiel Cornelissen on December 9, 2011 at 3:37am

Any idea what else could be going wrong? I have the rhino and gh files set up exactly as you have it, but I just don't get the circle showing up...

Permalink Reply by David Rutten on December 9, 2011 at 4:00am

Are any of the components red or orange? If so, what's the error message associated with them?

David Rutten

david@mcneel.com

Poprad, Slovakia

Permalink Reply by Michiel Cornelissen on December 9, 2011 at 4:03am

Nope, all looking fine and grey. I just get a 'null' output.

Permalink Reply by David Rutten on December 9, 2011 at 4:52am

I'll probably release a minor Grasshopper update within one or two days, you should then be able to use a specifically written component for this in Rhino4.

David Rutten

david@mcneel.com

Poprad, Slovakia

Permalink Reply by Michiel Cornelissen on December 9, 2011 at 5:51am

That's really great. Quite eager to try out this function :)

Permalink Reply by Michiel Cornelissen on February 2, 2012 at 11:40am

Bit late, this reaction; just wanted to let you know that I tried it, but I couldn't get anything other than the super simple cases to work. I'm sure it's mathematically correct, just a bit of a mind-bender. Not sure when I'll be able to play with it again, to have another go.

In any case, definitely appreciated the effort you put into this!

Permalink Reply by Michiel Cornelissen on December 9, 2011 at 11:00am

Guess I didn't have the latest rhino 5 after all; just installed another update and it's working great now. Will now be fiddling with my definition to get something like the above. Super tof man.