Noise propogating in circles

[ChrisCousins]

Hi - hope someone can help. I'm trying to make a fairly common effect of noise propogating in a circle, but I'm new-ish to Houdini so it's got me stumped.

My attempt uses a point VOP to animate the inner circle, and I'm attempting to use the Solver SOP to propogate this animation, basically setting the P.y of each point to the P.y of the point inside it in the previous frame. I thought this would be simple but I'm missing something very basic I think - file is attached. This is the VEX in the solver:

if (@ptnum > 100) {
    vector newpos = point(0, "P.y", @ptnum-100);
    v@P = setpointattrib(0, "P", @ptnum, set(0,newpos,0), "add");
}

Each circle currently has 100 points. Any advice would be welcome! Cheers - Chris

stackedCircles.hiplc

[Noobini]

here's my take on it...

vu_stackedCircles.hipnc

Edited July 11, 2018 by Noobini

[Atom]

It's makin' my mind spin.

[Noobini]

just a warning....if you plan to emit particles from this, make sure you RESET pscale back to 1 after you copied out the successively larger rings...otherwise, if you have them colliding with a ground plane say...you'd get a weird conical shape cuz...the outside particles are 'larger'...instead of the default 1.

hmm..well that's in theory....in practice...I had to reset it to 0 !.....doesn't make sense...here's that file, see if you can figure out why pscale should be reset to 0 instead of 1...

(so I guess a particle is just a point...ie. radius/pscale = 0, my bad for thinking of default 1)

vu_stackedCircles_particles.hipnc

Edited July 12, 2018 by Noobini

[ChrisCousins]

Fantastic stuff Noobini - thanks so much for this. Much more than I expected! Timeshift is much more elegant than solver, thanks for the pointers.

I can see this place is going to be my new favourite hangout - just browsing the old posts is like digging for gold... in a goldmine.

Cheers! Chris