[SOLVED] VEX - addpoint randomly on geo

[cgcris]

Hi guys,

I am trying to replicate the scatter behaviour, when plugin something like a grid.

Using VEX, what's the best way of adding a point on a geometry randomly?

Thanks,

Cris

Edited July 15, 2016 by cgcris

[animatrix]

You can pre-generate N points using Point Generate SOP, then generate a random integer from 0 to nprims(1)-1 using something like ptnum and a random position (using another seed) and then feed these into primuv VEX function for the second input. This will move your points randomly over a surface.

[holycause]

set your wrangle in detail mode and connect your geo to the second input

int prims = nprimitives(1);
int count = chi("count");
float seed = clamp(chf("seed"),1E-3, 1E8);
for(int i=0; i<count; i++){
    float rr = random(prims*i*seed);
    int prnum = int(rr*prims);
    float u,v;
    u = rand(i*seed);
    v = rand(i*rr*seed);
    vector pos = primuv(1, "P", prnum, set(u,v,0));
    addpoint(0, pos);
}

just noticed that I wasn't using the correct variable to initialize my for loop

It s fixed now ^^

Edited July 13, 2016 by holycause

[cgcris]

Hi Guys,

Thanks a lot for your replies, now looking at the code Ruben.

There is one line that doesnt work, I am guessing is a typo

float rr = random(prims*i*seed);

// should be
float rr = rand(prims*i*seed);

weirdly when using random the value doesn't update when changing the seed. 

Thanks for your help putting this together!

Best,

Cris

 

 

 

 

[animatrix]

Here is an implementation I put together in a few mins:

https://www.dropbox.com/s/1hqlv5n5nf3gk6c/vex_vs_scatter.hip?dl=0

It takes face area into account for even distribution. It's ~8 times faster on my PC than the SESI's Scatter SOP (no relaxing, no copying of attributes). So the more cores you have the faster it should get.

[cgcris]

Nice one pusat, will enjoy going through your example!!