local variations of the density of a random point distribution

Hi everybody!

Sorry to bother you with such a simple issue, but I can't figure out how to create a random distribution of points which local density would be based on some sort of "mapping"...

For example:

I wish to populate a rectangle with some random points, but I need them to be more dense at the base of the rectangle and then linearly getting more and more sparse towards the top.

This is how I worked it around:

1) first I have created a triangular prism,

2) then I've populated its volume with some random points

3) and finally I've projected them on the plane I'm wishing to populate.

But I don't really like the final result since the points are not as nicely spaced as if they were produced by the "Populate 2d" command. They look kind of "clumpy":

Do you have any better idea?

The best thing would be to be able to put a grayscale bitmap underneath and use it as a "density map"...

Here you have the .gh file I made:

prism.gh

Thank you very very much for the help! :)

By the way:

While I was preparing my 3d random distribution of points I've spotted a weird behaviour of the random command:

Even if the seeds are all different, for some values of them the points still belong to some common planes...

To solve that I had to jitter the output of one of the Random components.

I suppose this is a weakness of the pseudorandom generator implemented in the random component, isn't it?

Replies to This Discussion

Permalink Reply by David Rutten on April 27, 2013 at 12:19pm

The non-randomness of the pseudo-random numbers has been remarked upon. I might implement a random generator that performs better than the standard one at some point, not sure.

As for your points, it will be very difficult to not have them clump together. I think the best approach would be to create a full density distribution using the Populate components and then remove points from this set. I attached a file which show-cases three ways of removing points from a collection. It may give you some hints as to an approach that does what you want.

Another approach would be to unclump your points once you've made them. Delaunay meshing + smoothing would be a good way and I think the Kangaroo plug-in offers a whole range of exciting options.

David Rutten

david@mcneel.com

Poprad, Slovakia

Permalink Reply by David Rutten on April 27, 2013 at 12:20pm

Aaaaand the file.

David Rutten

david@mcneel.com

Poprad, Slovakia

Attachments:

gradient.gh, 19 KB

Permalink Reply by Matteo Falduto on April 30, 2013 at 5:09am

David, thank you for your time!

You're probably right: I'll try the kangaroo method. As soon as I'll have time to obtain some result I'll surely post it.

Permalink Reply by Andreas Iosif on April 18, 2015 at 2:33am

hey guys, how can i achieve that result with Populate3D with the dense part on the bottom?

Permalink Reply by Laurent DELRIEU on April 18, 2015 at 4:28am

You could use graphmapper

Attachments:

variable_density.gh, 10 KB

Permalink Reply by Andreas Iosif on April 18, 2015 at 4:57am

thanks for the help Laurent!

Permalink Reply by mark jongman-sereno on November 2, 2015 at 8:23pm

Does anyone know how to get the point gradient on a complex single surface (see attached).

I am trying to re-create the gradient with points. My thought was to color the mesh with a simple Black/White gradient and then populate the points based on the gradient values of black, however it seems like this is not possible...

Any suggestions would be of huge help!!!

Thank You so much,

mark

Permalink Reply by Hof architects on June 22, 2017 at 2:21am

Thank you.

Is there a way to apply the same principle (weight culling) on a order list of pts ? without flatten the list of pts ? in order to move in Z the cull pts.

Attachments: