Hi. I’m trying to filter the emission of particles by the velocity of emitter, with no success…
I did a simple test plugging the “Test Current Frame” node in the ICE TREE and it works, but trying to validate the emission by the condition of “Point Velocity” value to bigger then “0” doesn’t works… What I’m doing wrong? Any help?

I found an old topic with the same theme, but the example attached is no longer available… http://area.autodesk.com/for...t/emit-based-on-velocity/

Thanks!

	Attachment

It’s likely because there isn’t a PointVelocity attribute set on the emitter’s points. That attribute is only added as needed, e.g. on a simulated particle cloud.

What you can do is open the emitter’s global kinematics property editor and click Compute Vel/Acc on the Velocity/Acceleration tab. Then in the ICE tree you can get the Kinematics/Global Transform/Velocity/Linear Velocity parameter and compare that value (assuming you have fcurves on the emitter’s position).

I noticed that your point cloud is not simulated, which is unusual. Was that deliberate?

Ops… Not so fast… :(
I forgot that my mesh is baked, with mixer controlling the cached simulation…
I can´t access the Linear velocity since it don’t have Fcurves…
Maybe if I create a group of a Cluster with center in each rock and then use it to access this parameter?

In that case you’ll need to use PointVelocity instead of the object’s velocity.

The easiest thing would be to re-cache the falling rocks and explicitly specify PointVelocity in the Attribute List.

If you don’t have the original simulation, then you could use a second hidden mesh to read the cache at CurrentFrame - 1, subtract the PointPosition of the second mesh from the first (use a Switch Context node), and divide by Simulation Step to get the velocity. Instead of using a second mesh, you could alternatively use a simulated tree to store the previous point position.