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jed

What's a Cissoid ?

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Today I needed to align an object to a figure of 8 spline, and I noticed, in the pen panel, something called Cissoid. In the drop down there's Lemniscate - which is a nice smooth figure of 8. Bingo ! However, when I aligned my object, it was all jerky. I've never used Cissoid before, so it's probably me making a noob mistake - or is a Cissoid not a spline?

 

cissoid.c4d

 

I feel a D'OH coming on ...

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I couldn't get the angular jumps out of the Cissoid either.  I tried different Intermediate Points settings, and they seemed to do nothing.  For some reason the points hidden in the parametric object are linear.  So, I made it editable and changed the spline Type to B-Spline, which helped a lot.  But I noticed some weirdness especially when it got to the center.  I think the Cissoid is a little too mathematical and not as beautiful as what I think of as a nice figure 8.  So, I drew one by hand!  I'm pretty happy with how elegant and smooth it is now :D

cissoid figure 8 v1.c4d

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  • Thanks for having a look. Wiki says a Cissoid is generated from 2 curves, so maybe it's not suitable for align stuff.

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  • Using a cloner + rate or offset to animate an object on a Cissoid is still jerky. It's no big deal BTW, I can easily draw a figure of 8, I just wondered what a Cissoid is and why it appears to be a spline but acts slightly differently.

     

     

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    Ah, I see.... The issue here is that internally cissoid is compromised of many points. If their tangents are used for orientation then there will be abrupt changes due to point density. You can circumvent this by using Cloner and MoSpline with which you can resample the spline.

     

     

    cissoid_0001.c4d

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