pop rbd scale over time

[ela1995]

I have a DOP Network with multi solver, which spawn rbd sphere with pop solver. How do I make the size of the sphere small at the source, then become bigger as the current size when it touches the ground.

 

pop_rbd.hip

[GDonkey]

Hi there,

Try putting a Sop Solver between the pop solver and bullet solver. Then in there, a primitive sop, turn on transformations. and use a fit expression with @age to scale them over time starting from when each particle is born. Hope that helps.

[toadstorm]

If you want Packed RBDs to grow over time, you need to do two things: scale up the transform intrinsic attribute, and force the solver to recalculate collision geometry.

You can do all this in a Geometry Wrangle or POP Wrangle, it's faster than a SOP Solver.

matrix3 xf = primintrinsic(0, "transform", @ptnum);

scale(xf, 1.02);

setprimintrinsic(0, "transform", @ptnum, xf);

i@id = -1; // force collision recompute

 

[merlino]

On 9/5/2021 at 8:25 PM, toadstorm said:

i@id = -1; // force collision recompute

that's the line of the year for me  

Thanks Henry!

[toadstorm]

Note that you don't need to do this anymore as of Houdini 19! You can just set `scale` or `pscale` point attributes during the simulation. They'll scale the transforms relative to the `resttransform` that's automatically generated on the first timestep of the simulation.

[merlino]

hmmm ... that's strange, as my setup isn't working without this line, actually using pscale attribute. In order to make it works we had to add this line at the end of the geo wrangle ... maybe is something related to this specific release, 19.0.561, not sure as we can't use newer version for Arnold compatibility, but I'll do a test with a newer 19.0 release on my home pc.

Thanks for the advice