Get random but connected points on a geometry

[cur10us]

Hey there!

I'm totally new to here and Houdini. Trying to learn it by doing some practical tests.

How can I get random points on a grid or any geometry? The condition is that they have to be connected. So, I would give it some number(or a range), it would create one "island" of points with that number. With some seed value I can change the pattern. (example below)

Can anyone give me some pointers?

Thanks a lot

Edited September 10, 2021 by cur10us

[Atom]

Well, they are all connected, right? You mean connected by a certain vertex count?

You could select a bunch of random points, then throw away the ones that fail the neighbor vertex count test.

https://www.sidefx.com/docs/houdini/vex/functions/neighbourcount.html

[cur10us]

thanks for the reply.

actually I meant something more like this. I want to get patterns like this on a geometry. can this be done with neighbourcount ?

[Librarian]

///1 points wrangle

float r = rand(@ptnum * chf("randseed"));
i@group_sources = r > 0.85;


--------------------------------------
/////2 wrangle
//group sources
int nears[] = nearpoints(0, @P, chf("maxdist"));
foreach (int pt; nears) {
    setpointgroup(0, "nears", pt, 1);
}

 

[konstantin magnus]

Hi @cur10us,

I think I would mainly use the surfacedist() function.

First group a few target points:

rand(@elemnum, chi('seed')) < chf('chance')

Add noise to a custom position attribute:

v@pos = v@P + noise(v@P * freq);

Then measure the distance over the noised position attribute:

int pt_close = -1;
float dist = surfacedist(0, 'target', 'pos', i@ptnum, pt_close, 'edge');

And apply random ranges for each island.

float range = fit01(rand(pt_close), 0.2, 0.4);
i@group_island = dist < range;

 

group_islands.hiplc

[cur10us]

this is great. thanks guys! I'll check these out as I get the chance and come back If I have question. though, a quick one: is it possible to do this with vops? is one method more preferable over the other?

to me this is more readable and faster to analyze.