POP split confusion

[Andy Nicholas]

Hi guys,

Okay, I'm a bit confused about this.

I've got a POP network which creates some particles, adds a force, assigns a colour, and then uses a Split node to spawn some more particles (transferring all attributes except color - intentionally as that helps to exhibit the issue I'm having).

The problem is that all the particles that are created by the Split node in my POP network don't seem to get fed back into the main simulation. I.e. they don't experience the force, or pick up the color attribute. It's as if the particles created by the Split node are in an entirely separate particle system.

What am I missing here?! How can I get the split particles to behave exactly like all the other particles in the system? I tried putting a Collect POP at the end to merge the main set of particles and the split ones, but it doesn't appear to do anything.

Any ideas?

Regards

Andy

[SpencerL]

Hi guys,

Okay, I'm a bit confused about this.

I've got a POP network which creates some particles, adds a force, assigns a colour, and then uses a Split node to spawn some more particles (transferring all attributes except color - intentionally as that helps to exhibit the issue I'm having).

The problem is that all the particles that are created by the Split node in my POP network don't seem to get fed back into the main simulation. I.e. they don't experience the force, or pick up the color attribute. It's as if the particles created by the Split node are in an entirely separate particle system.

What am I missing here?! How can I get the split particles to behave exactly like all the other particles in the system? I tried putting a Collect POP at the end to merge the main set of particles and the split ones, but it doesn't appear to do anything.

Any ideas?

Regards

Andy

Thats exactly what its doing. All POPs after the split POP will only affect the split particles and vice versa. The split particles will inherit the attributes from the particle they are splitting from on the frame they are born but if you want the same behavior, just copy and paste the Force, Drag, etc after the split POP.

A collect POP is essentially like a Merge SOP for particles.

[Andy Nicholas]

Thats exactly what its doing. All POPs after the split POP will only affect the split particles and vice versa. The split particles will inherit the attributes from the particle they are splitting from on the frame they are born but if you want the same behavior, just copy and paste the Force, Drag, etc after the split POP.

A collect POP is essentially like a Merge SOP for particles.

Hi Spencer,

Thanks for the reply. Okay, I understand what you're saying.

The problem is however, that I want to have exactly the same behaviour from the split particles. I.e. I want them to be able to create particles themselves using the Split node. So if I understand you correctly, I'll have to keep on copying and pasting the entire tree numerous times according to how many levels of recursive splitting I want? Aaaaargh! That's totally crazy!!!

Is there really no way I can just tell these new split particles that they're exactly the same as the other particles? Do any of the lineage type of attributes have any effect on this? How is Houdini keeping track of which particles are which?

[RichieMayor]

The trick is to emit the split particles from a group and then add the split particles to this group.

Create a group POP node before your split POP, set the rule to 1, or whatever suits your needs and check the 'preserve group' option.

In the split POP add the same group name in the source and the birth group fields and also check 'preserve group' under the birth group field.

[Wolfwood]

The trick is to emit the split particles from a group and then add the split particles to this group.

Create a group POP node before your split POP, set the rule to 1, or whatever suits your needs and check the 'preserve group' option.

In the split POP add the same group name in the source and the birth group fields and also check 'preserve group' under the birth group field.

Richie with the very knowledgeable first post! Well done.

Aye, exploiting the superset functionality of groups is exactly the way to handle this.

I posted a sample on the SESI thread dealing with recursive pop splitting.

http://www.sidefx.com/index.php?option=com...pic&p=64582

[Andy Nicholas]

The trick is to emit the split particles from a group and then add the split particles to this group.

Create a group POP node before your split POP, set the rule to 1, or whatever suits your needs and check the 'preserve group' option.

In the split POP add the same group name in the source and the birth group fields and also check 'preserve group' under the birth group field.

Thanks Richie, I'll give it a go. Looking at the link that Wolfwood posted, I think that should do the trick.

Cheers!

Andy