I've been doing some grains sims, about 1.3 million pts per wedge. After I write out each wedge, there are around 15k to 30k particles per wedge (different for each), that have NAN values for the P and v attributes.

I cant view these particles in the viewport, they seem to be invisible when I isolate them, but I can see them in the details view. The other attributes I have on them (orient, pscale, etc), seem to come through fine, but P and v get NAN values.

Unfortunately I can't post the hip file because it's from work, but I can give some details about my setup. I think the issue may be the clumping (attractionweight attribute). I have very high values for the clumping stiffness, ~200 or more.

The grain pts are interacting with a pre-cached rigid body sim, which is causing some violent collisions. It's basically characters digging through rocks, and I've made dirt (pbd grains) to go with the rbd rocks. I've been trying to get more clumping and clods of dirt, but the violent movement of the collision geo always breaks the particles apart.

So recently I've cranked the clumping stiffness from 35 to 200, and that's when I started having problems. It seems to affect my renders too, unless I delete all the NAN points.

Has anyone encountered NAN particles when working with grains, or knows how to get clumping to work with really violent collision geo?

Also openCL stopped working once I turned up clumping. Same amount of pts, but the scene started crashing everytime I initialized the sim.

My setup:
Creating attractionweight attrib on source pts, using vop noise, values are 0-1
pop solver substeps: 15
grain solver constraint iterations: 120
particle separation: .005
particle to particle friction: .95
particle to collision friction: .95
scale kinetic: .3
collision weight: .5
clumping weight: .5
clumping stiffness: 200
explicit constraint weight: 0
disable constraint averaging is checked on

sourcing my collisions into a static object DOP, with both a “collision” field sdf, and “collisiongeo” polys with v.

Thanks for any ideas on these issues!