Grasshopper

algorithmic modeling for Rhino

Hi guys! Here is another puzzle. I am sure there is a simple way to do it. But I have no clue.

I need to make this helix. It will be a tunnel as a final 3d. I need to give it a width. 

I need that the lines should match perfectly when they pass each other. If you can look at the image you will understand better what I am talking about. Check the 4th step in between point 10 and 9. The lines dont match there. And they just get worst once in loop them more.

Can someone help me?

Thanks a lot!!

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There are 2 Interpolate curve components:

- Interpolate (IntCrv) which you used;

- Interpolate (t) (IntCrv(t)) which you need.

This second one uses tangent vectors for the start and end of the curve.

Probably someone already made a component for custom helix...

I'll make another one just for fun...

Hi Riccardo, tks for your help. But it didn't work for me. Is there any other solution?

tks!

That's an helix not a spiral.

And also, i never had problems with interpolations, you just need to give correct start-end vectors, i always get very smooth curvature graphs...

Max, see attached file, use red slider and try to understand how to use the vector.

I can't fix your definition because i don't get where to take diameters.

The angle for vectors should be a=arctan[pitch/(Pi*Ø)]

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Thanks Riccardo!

I got what you did. I was really struggling with this issue. 

Btw,the diameter I've done this (x*y)/360 where x come from my series and y is the distance between the lines. It is proportional, where 360 means 360 degrees. By doing this, all the loops will have the same width. 

The diameter is given by the distance of the center and the first point of the curve. I started the helix from outside, not from inside. 

Anyway, tks a lot for your help. I really need to go deeper on curves. I need to understand how they really work, and the differences between them all.

I am really new in Grasshopper, and this is the only way I could find the solution. I am pretty sure there is something better.

Why you don't want to use cylindrical system of coordinates? At it use the spiral turns out very simply with full control.........

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Sorry but...I didn't understood you.

Are you talking about using weighted control points and knot vectors?

Really, i never had problems with interpolated curves; a projection of a interpolated(t) helix perfectly overlap with a circle, and from side give a perfect sine/cosine shape...

I'm missing your point...

I personally would prefer to create curves, not to join pieces together.

But then, going back to op, how to achieve a flat helix, or spiral, with the same method you suggest?

Well then...

I'm indeed interested in this, but i supposed knots and weights whould help the explanation....

Can you explain how you achieved that helix "sample" (which you used to make any other helix) and why it is better?

(the how and why might have the same answer... i'm being repetitive, sorry)

Maybe with some math... can't we create a good single-curve helix or spiral by using just control points (and/or knots and weights)?

Thanks already.

Well ...

IF you intend to sweep1 something (i.e. a collection of profiles) using a spiral/helix as a rail I would strongly suggest the approach used in the def attached.

Of course NOT all profiles could "comply" with the rail topology ... but the gist is rather clear I do hope.

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