knot points

[andrewjohn81]

knots make a kink. They are several cv's sharing the same space that move together.

There are few instances that you should use them. One is if you want to loft two lines. One going from a sharper angle, and another that has a large radius at that angle. If you want to keep that one surface then there will be a knot on one side, but not on the other.

Moving a knot will not keep anything tangent to it.
Moving an edit point always keeps in the tangent angle. I wish it showed the cv's at the same time. It makes it much more understandable. If you have access to Maya, you can get a great example of that. A cv always lays on a cv, but when you move it it also moves it's shared cv's. You just can't see them.

That's the best way I can explain it.

[jamesvalue]

thanks andrewjohn81!

[Hypernaut]

sorry, but I have to contradict you andrewjohn81, concerning the kink - at least in Rhino.
There is a clear difference between kink and knot in Rhino. The kink is curvepoint making kink on the curve as you described it (with no possible tangente), while the knot is also a curve point that definitly has a tangente - has to have a tangente gointg through all knots (I think it is called steadiness or constancy or continuousness).
I don't know the mathematical terms in english on curve-tracing, so I can't describe with the mathematical terms :-(
With edit point you just move around the curve points (no matter if kink or knot), resulting in new curves which fulfill the steadiness (or whatever it is called)
while control points lets influence you direction of tangency and the shifting of the point of inflexion on the curve.
Hope I could make myself clear...
Any correction and addition welcome...

[jamesvalue]

Thanks alot to you Hypernaut for your explanations.

I also noticed that Rhino's help , tryes to explain the difference between "edit points" and "knot".

"edit points" are simply distribuited on the curve , by averaging, the location of knots.


Anyway thanks again!

[andrewjohn81]

Ah, you are correct.

After your post I too read what it said in the help documents and noticed that it's different than alias. I find that strange since this guy came from Alias.
In alias products you must make your own "kinks" from duplicate edit points. Those are described in that help file as knots when you do that. This is because if you were ever able to zoom infinitely into those points on top of one another, because of tolerances, they would lie on top of eachother and would create a knot. Or at least a squigly mess from what I understand.

In alias products there is one edit point for each span for whatever the degree surface it is. If there is a degree 3 surface with 7 cvs, then there will be 3 edit points. Keeping that in mind, a good model should always have an edit point sharing a cv if you want the object to be able to be perfectly tangent with the next. This is in Rhino as well. If you don't then the edit point has to be averaged along with the surface span that goes along with it.
So for every curve on a degree 3 curve there should be 4 cv's, but the first and last can be shared with the next curve if needed.

[Azeiku]

If they're knot points... then what are they? Curves?...hahah.. Get it? NOT points. :bounce: hahaha! Okay that was lame.:shrug: Sorry.

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