Is there a way to sort points in clockwise or CCW order?

[magneto]

Hi,

I have a bunch of points and I want to sort their point numbers in a clockwise, or counter-clockwise order. Is there a SOP that can do this or do I have to do this manually in VOPs?

Thanks

[edward]

I'm assuming that they belong to a polygon? Try the Reverse SOP and the followed by a Sort SOP with vertex order.

[magneto]

Thanks Edward, actually no it's not a polygon. It could be a polygon though

Basically I want to create a polygon using the outline of multiple continuous polygons. So I was trying to create the polygon from the outline points manually. Do you think I can rely on the vertex numbers using your technique? I just thought the verte numbers wouldn't necessarily be in increasing order. So that's why I thought of creating a polygon from the points manually, but also have the points in CW or CCW order.

Thanks

[edward]

Ah, no that's a different problem. It really depends on your data, and probably hard in general without taking into account whatever structure is present.

[eetu]

I'm not sure I understand your use case, but here's a method for just sorting points in a cw/ccw fashion. Basically just create a cylindrical uv mapping and sort according to u.

For added proceduralism you could maybe make the center of the mapping be the center of bounding box or weighted average of point positions..

ee_clockwise_sort.hip

[magneto]

Thanks Eetu, that's exactly what I needed. Great trick

[acey195]

Alternative you can just use a "Sort" SOP and create an expression to sort in a circle:

atan2($TX,$TZ) for the XZ plane

As a matter of fact, I created this a long while back already (so it may be a little inefficient). The attached OTL will only work for points, but the expression above can easily be adapted for primitives as well.

Acey

SortCircle.otl

[magneto]

Thanks alot acey, this is definitely a useful OTL. Can this be adapted to use any plane normal? This way if your points lie on an arbitrary normal like {1,2,3}.normalized(), you could still use it to sort the points in the same fashion.

Thanks

[acey195]

Currently it only works on orthogonal planes (XY, XZ and YZ planes), I probably can make it to work on an arbitrary normal as well, but that would require a more complex expression.

I haven't used that OTL in a while, since I tend to use Vopsops more nowadays, which I would also use to tackle this problem.

I can try to update the OTL, using a VopSop if you want to.

[magneto]

Thanks, that would be cool if you have a few free minutes, especially if it could handle any normal

[acey195]

It is by no means perfect, results may vary

The preview Plane does not turn with negative values.

I hope it works for what you are trying to do.

SortCircle2.otl

[magneto]

Thanks alot man, that's great

[Jephyr]

The cylindrical mapping solution and sort by expression works wonders for me too! THANK YOU eetu!