What's wrong with my planesoreshout

Hi there,

I am trying to make a series of planes along a catenery curve at point specified byu a series. I am the finding the tangents to those vectors and then using the 'plane normal' component. However the x and y axis of these planes are all over the place. Any ideas as to how to make them sit normal to the vector in the same plane as the catenerary crv?

Thanks

Replies to This Discussion

Permalink Reply by Tudor Cosmatu on May 14, 2012 at 1:06pm

i guess the same thing is happening if you're using the pframes component? Had this issue for quite some time and didn't get the logic behind the flipping planes... maybe david knows something about this issue?

Permalink Reply by David Rutten on May 14, 2012 at 1:34pm

Planes from origin and normal vector are underdefined. The rotation about the plane z-axis is basically made up on the spot. I think the planes are minimal rotation planes from either the XY, YZ or XZ plane, whichever is closest.

If you want your planes to be aligned, you'll either have to use PerpFrames (which are minimum rotation amongst themselves) or some form of Plane orientation component.

David Rutten

david@mcneel.com

Poprad, Slovakia

Permalink Reply by Tudor Cosmatu on May 14, 2012 at 3:30pm

Thanks for the reply, but is it normal for something like this to happen even when you are using perpFrames? I recall an issue i had few weeks ago where "according" to the number of perpFrames i was getting seemingly random flipped planes throughout the curve and after passing 10 divisions i was getting only the end frame flipped...

Permalink Reply by David Rutten on May 15, 2012 at 1:02am

PerpFrames shouldn't do that, though I suspect they might not work very well on polylines. I could be totally wrong about that, but if the PerpFrame algorithm in Rhino relies on curvature or torsion, then polylines won't yield good frames because they have no curvature or torsion.

Another problem could be a singularity in the curve. For example when two adjacent polyline points are coincident, the segment in between them has zero length and might cause all kinds of funky behaviour. This can be remedied by Simplifying/Reducing the polyline.

David Rutten

david@mcneel.com

Poprad, Slovakia

Permalink Reply by Tudor Cosmatu on May 15, 2012 at 1:23am

ok, sounds fair enough :) ! Thank you David! Will keep that in mind next time, and if it will occur again will let you know with a proper example ;)

Permalink Reply by crayfishyfishyfishy on May 14, 2012 at 3:22pm

Hi thanks guys figured it out. However if you can see in the picture the first and last planes along the line are like spazzing out. They keep on spinning out they keep on turning around randomly and I can't figure out why. I'm running the curve out of a Kangaroo Simulation. Any ideas?

Permalink Reply by TheChosenOne on July 10, 2012 at 7:18am