Get Sop Vel to pops

[mhspadez]

I'm trying to find a way to get bring in the velocity from a field i created in sops into pops directly. 

I can do this easily in dops with a sop geo and a particlestofield node, but i can't seem to replicate this in pops. I've seen this done before in a pop wrangle, but I don't know the code myself. Can anybody help me out?

[bunker]

in a pop wrangle, set your first input binding to your vel volumes SOP path, then:

// using VDBs
vector v =  volumesamplev(0,0,@P);

// or using Houdini volumes
float vx = volumesample(0,0,@P);
float vy = volumesample(0,1,@P);
float vz = volumesample(0,2,@P);
vector v = set(vx,vy,vz);

 

 

 

[mhspadez]

@bunker Thanks for the reply, very much appreciated. But I'm still not able to get it to work. Maybe I'm doing something wrong. I assumed in the sops level I have to convert my vel field to a vdb, but that didn't work either, and then I copied your code for vdbs into my wrangle. Would you be able to show me a sample file?

I've uploaded the .hip where I'm trying to just test the vel update. 

 

Also, Just to clarify on my first post -- i'm just looking for any way to bring the vel into pops. It doesn't have to necessarily be using a wrangle. 

vToPOPs.hip

[Sepu]

You can use just the  Trail node, change it to "compute velocity". 

[mhspadez]

@Sepu I appreciate the response, but I'm not trying to add velocity to the emission source. I'm trying to bring in a separate velocity field that would affect particles that enter the area of the field. This additional field would be separate from the emission source. So while the trail sop would add velocity to a sop, I'm more specifically asking about how to get those velocity fields to affect particles in a pop sim.

[Martin47]

Here is an approach, there is some sticky notes inside for explanation

take a look..

vToPOPs.hipnc

[mhspadez]

Thanks Martin, this definitely works and is a perfect solution for this sample file. When it's scaled up creating the volume definitely starts to get heavy though. There must be another way to bring in the velocities directly without the conversion to a volume. 

[rbowden]

The slow down is being caused by the points from volume node. When you scale it up and keep the particle separation the same, the number of points inside your sphere object is going to grow exponentially.

 

[mhspadez]

Ah that's a good idea. Definitely worth giving it a shot. 

[mhspadez]

@Martin / @rbowden -- you guys were right. As long as you keep the resolution down in the volume it works fine even with a larger sim. Thanks for the tip. This will work well for what I'm doing. Thanks again.