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sessionbeer

Recreate arc curve from two circles

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Hey,

I would ideally like to have this all happen in Vex rather than the set I have made here. This would allow it to be more scalable, but perhaps I can save that for my next problem.

Right now I am wondering how I go about recreating the curve I have outlined in pink on the image? Any ideas would be a big help as I'm really stuck.

Thanks

Curve.png

Metaball Arc_Circles_A_01.hip

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I would start by thinkng in geometric terms about the shape you want to achieve.

For example if you visually connect the center of the circles you see that the imaginary line cuts the circles when they touch, and at those points the red dotted profile you want to obtain changes its concavity.

The top and bottom circles touch (and don't intersect) the side circles 2 times (one for each circle). This means also that they have the same tangent at those points, so the center of the top circle should be in the intersection of the normals of the side circles at those points of contact. 

You could choose 2 points on the side circles and find the radius and the center of the top circle with some algebra and trig.

Also if you follow the red profile and analyse the concavity you see that it's always concave-covex-concave-covex... you never have a concave-concave for example, so this pattern could help maybe to choose which part of the circle to keep once you find a way to split it in 2 parts. Oh yes and each circle is divided in 2 parts, one that forms the part of the profile, and one that has to be deleted.

The way I would boil down this problem would be: having circles where they need to be, find cut points, keep only parts of the circle i need. And then back again, what kind of control I want for this setup? how easy is for example to find intersection points and deciding which part to blast ,compared to generating the geometry point by poiint via vex, or deforming something else into that shape maybe?

Sorry it's a bit of rambling, not really a solution, but this is how I usually approach these kind of problems, trying to see a pattern or a feature that I can take advantage of, and see what tools gives me the closest solution to this "attack point".

hope it helps...

 

anyway i'm pretty sure i have seen some example file here on odforce for this. There was also a website where a motion graphic artist were making lots of tests with this kind of patterns, they were interactive "things" on the browser and you could see the code he used and play around with the controls he exposed. Maybe someone else here knows what i'm talking about.

Edited by MENOZ

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i thought of this some months ago and did a tutorial about this. here's the link to my tutorial, hope it help you:

 

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7 minutes ago, haiheo said:

i thought of this some months ago and did a tutorial about this. here's the link to my tutorial, hope it help you:

 

Thanks for the link and tutorial :)

You go through how to build my current set with vex which is great, I still need to recreate that red outlined shape though, and ideas with that and your vex route?

Thanks for the ideas @MENOZ that's sort of the way I've been approaching this problem so far, but haven't been successful in finding a viable solution yet.

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