Vector math

Replies to This Discussion

Permalink Reply by David Rutten on October 30, 2016 at 8:49am

Hi Tomas,

vectors don't have starting points, they are merely directions in space. What you have there are lines. Although if they are all supposed to have the same startpoint, then I guess you can just focus on the direction only...

When you say adjacent, do you mean you want to find the one that points as much as possible in the same direction, or one that is actually pointing in the exact same direction, or the two vectors on either side? If the latter, then it's a strictly 2D problem because 'side' doesn't work in 3D as a concept.

Permalink Reply by Tomas Vinkevicius on October 30, 2016 at 8:59am

It can also be lines. I would like to have two lines/vectors that pointing in the similar direction as red one.

First I was thinking that I could measure angles between all vectors and take two with smallest angle. But this worked only two certain extent. When I have very wide angle this type of sorting fails to find.

What would be a method in 2d either in lines or vectors?

I was also thinking use convex hull. But I want to find a more simple method of sorting.

Permalink Reply by Tomas Vinkevicius on October 30, 2016 at 9:03am

I also saw someone using circle as a guid curve for sorting points. But is there a more simple method for retrieving specific element "neighbours"?

Permalink Reply by Tomas Vinkevicius on October 30, 2016 at 9:32am

And it can be lines instead of vectors as I start from them.

Permalink Reply by Daniel González Abalde on October 30, 2016 at 11:19am

If this serves you, you should unitize vectors, in this example I did not make for better viewing.

Permalink Reply by Tomas Vinkevicius on October 30, 2016 at 12:25pm

Does the vector subraction sorting works when taking this line as start member?

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• 785bc9e3-8ab1-4424-af8d-b51430f63ca3.png, 312 KB

Permalink Reply by Daniel González Abalde on October 30, 2016 at 1:57pm

You have to use the vector line, heading out, replacing the [List item] (A), and replaces the [Cull item] with the other vectors (B). The [Subtract] component returns the vector from B to A and [Sort List] receives the length of the vector. That is, simply measures the distance. As the vectors are unitary, the two closest are the surrounding.

Permalink Reply by Daniel González Abalde on October 30, 2016 at 7:13pm

Uooops, forget this, the two closest are not necessarily neighbors, sorry! Pieter's method is the correct way.

Permalink Reply by Pieter Segeren on October 30, 2016 at 5:10pm

Hi Tomas, provided the lines end points are the mutual point, here's my two cents, a kind of circular sort really:

Permalink Reply by Pieter Segeren on October 31, 2016 at 4:09am

I should have said: provided all lines start at the mutual point (like you stated in your initial question), or all lines end at the mutual point.

Permalink Reply by Tomas Vinkevicius on October 31, 2016 at 2:30pm

Dear Pieter,

Thank you very much that was what I looking for:)

I tried to use this in 3d and it also works.

Do you know if this works in 3d in all cases or it is a 2d problem? 

Permalink Reply by Pieter Segeren on October 31, 2016 at 4:06pm

Hi Tomas, it's a pure 2d solution. I'd say for a reliable method in 3d you'll need to find the two smallest angles.