animated per point friction without deforming geo

[Bill]

I'm using the SPH solver and I'd like to animate friction values on the RBD object (per point). If I create a point attribute in SOPs called 'friction' and set my values there, they do get used in DOPs if I have 'Use Deforming Geometry' turned on (on the RBD Obj node). However, that's kind of overkill... I really don't have deforming geometry (it's not moving), and turning that on REALLY slows down my sim. So is there a way I can keep it as a static RBD object and then fetch the friction values and apply them (per timestep)?

Thanks,

Bill

[anim]

if your geometry is not deforming, then one thing you can do is

go to first frame of your sim

on your RBD object/collisions/volume fill in File parameter(path where the collision geo will be saved like $HIP/file.simdata) and change file mode to Write Files, this will save collision volume for the current frame

change File Mode to Read Files

this way the collision volume generation will be skipped so you can turn on Use Deforming Geometry and it should run much faster and pick up your updating point attributes

Edited May 28, 2010 by anim

[Bill]

Yeah, I had tried that already and it was still VERY slow. I didn't know what else DOPs was doing when you turn on 'use deforming geo', other than creating the SDF (which it doesn't if you're reading it from disk). It shouldn't have been calculating velocities, because I had turned on 'use point velocities.' I sifted through the RBD Object OTL but didn't see what could be taking so long.

I found that the point attrs are stored in the 'geometry' data on the RBD object. So I used a SOP Geometry DOP and pointed it to my SOP with the friction attr values and had it update the 'Geometry' data every frame. This worked. However, it's still slower than I'd like. I stripped out all other attrs except for friction. However, DOPs is still updating the vector P and the float friction. It would be nice if there is a way to only update friction, not P.

[anim]

have you tried SOP solver and just copying friction attribute?

(of course then turn use deforming geometry off)

[Bill]

No. I will give that a try.

Thanks.

[anim]

actually i've tested it now and it's not very different from SOP Geometry method, but I don't think both are so much slower than default static geometry in DOPs

maybe your geometry is very dense

you may consider using lower-res mesh for DOPs

[anim]

you can check your Cache Memory size on your DOP network, because simulation is usually slower when it starts caching to disk so you may want to keep this cache size to maximum (according to your RAM) to get faster simulation