POPS question

[loudsubs]

I have a simple setup of a particle system as the template for a grid on a primitive sop. I want to make a crumbling ground effect.

The falling motion of each primitive looks good as each particle gets affected by gravity, but the primitives stay parallel to the ground as they fall, which doesnt look too convincing. I would like to have them rotate down as they fall, as if the outer edge is pulling the rest of the primitive down with it. Hard to explain, please take a look at the file.

Messing with the rotation and up vector pops didn't really work for me, I'm not totally sure how these operators work. one thing I did notice is when I turn on particle origins, on the display bar, the y-vector of each particle is pointing straight up (the way it prolly should), before gravity affects it, but once the gravity hits it, the orientation immediately flips 90 degrees and points in the Z direction. This doesnt have an effect on the falling primitives in sops, but it seems this might be part of the mystery.

Any insight is much appreciated.

pops_ground.hipnc

[static]

Make sure you have Rotate to Template (dorot) set to On on the primitive SOP. I also switched out the rotation POP with an angular velocity POP. You don't want them to start rotating a ton at first so I added another attribute to help ramp up the angular velocity. As for the particle normals, they face towards their trajectory, which can lead to sudden jerks and flips if they all of a sudden start moving. In this case, you can simply blast the normals after the sim to make sure they line up. Hope this helps.

pops_ground_update.hipnc

[loudsubs]

Thanks for the lesson static. Very good idea to manipulate the normals. And the angular velocity pop is definately what I was looking for.