# Thread: "Five Point Sphere"/ "3 point circle"

1. ## "Five Point Sphere"/ "3 point circle"

Lookin' around for two plugins:

I found this one: select 3 points, and it creates a circle that passes thru those three points.

The other one I'm looking for does the same thing, but for spheres, and I believe it requires 5 points ....although shouldn't 4 be enough?)

2. Originally Posted by jeric_synergy
Lookin' around for two plugins:

I found this one: select 3 points, and it creates a circle that passes thru those three points.

The other one I'm looking for does the same thing, but for spheres, and I believe it requires 5 points ....although shouldn't 4 be enough?)
Yes, I believe 4 should be enough...

3. Not sure...if you have a perfect 4 vertex poly, there are a lot of possibility of sphere...but with a 5th vertex...

4. well, in that case for any cyclic N vertex poly you'll have many possibilities for creating a sphere.

5. Usually these routines insist that there be vertex that is not coplanar with more than 3 others.

Any given 3 vertices can define a circle. Throw in another that is not coplanar with the first 3 and you define a sphere.

And I'm still looking for that plugin.

6. Where did you find the 3 point to circle plugin. I was looking for something like that the other day.

7. It was on, and by, Kevin MacPhail's site.

The math for a 4 point sphere involves matrices. ::shudder::

8. Thanks

9. If you guys can't find a plugin that does 4 point sphere (maybe LWCad can do it?) I could probably create a quick lscript for that... I think.

10. Originally Posted by art
If you guys can't find a plugin that does 4 point sphere (maybe LWCad can do it?) I could probably create a quick lscript for that... I think.
LOL. We shall see: search the page for "Four points are sufficient":

Wolfram!

I remember the old routine was instantaneous: I'm not sure how fast all this math will get executed in LScript.

+++++++
Oh, now I found the one I originally saw...

11. Originally Posted by art
If you guys can't find a plugin that does 4 point sphere (maybe LWCad can do it?) I could probably create a quick lscript for that... I think.
Yes, please. I'm finding that nothing works here except UB plugins ending in .plugin, and good ol' lscript, which always works, and seems to be pretty solidly cross-platform.

12. The link Jeric posted has a piece of C code there as well, which i think can quite easily be adapted to LScript or a plugin.

I'm quite busy at the moment, but i still have some Phantom super slow mo shots to convert, might give it a try when those are converting.

13. Edit: never mind...I was thinking of something else.

Kuzey

14. I've been to that site before (Paul Bourke's) and they have plenty of useful stuff for 3d math. As Red Oddity said, converting that C code should be very straightforward. I can try to do it this evening unless he beats be to it

15. Took a quick look at it, seems very doable, it looks like removing the memory allocation and initial sphere setup are the only things that need to be removed and some variables need to be declared (like the multidimensional arrays).

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