Basic particle sim questions

[WAV94]

Hello,

I have two basic questions regarding particle simulations in Houdini.

I have a very simple setup, where I make particles emanate from a human base mesh, and instance some simple geometry onto the particles to export the simulation as alembic to 3rd party software (Blender).

The first problem is that the simulation seems to duplicate all particles and place them at 0,0,0 global in global space (see the tiny sphere in the picture foreground). This is unwanted, because the geometry from these particles will show up in final render in Blender, and because it makes the simulation heavier than it needs to be. How can I get rid of it?

My second problem is that whenever I export the simulation as Alembic (with the setup also shown in the picture), Blender seems to read every particle as an individual object. Is there any way to merge all the geometry into a single object from Houdini before export? There is no option in Blender to make it read the file as a single object.

Thanks in advance!

//William

[jdiazsaezwd]

Hello, I'm, no master on the matter, don't know why particles are being replicated at the origin, you can get rid of them with a simple delete node with a bounding box in sops, or directly in pops. As for the alembic export, there is a node called packpoints, which may help with with the times but you would need to unpack in blender I think, don't really know the workflow for that. Hope it helps

[DonRomano]

The particles going at (0,0,0) may be some deleted particles in the sim that the instance node try to retrieve and then it just pop some particles at (0,0,0) to keep the @ptnum logic. For instancing use the @id attribute instead of @ptnum attribute, it should resolve this.

Regarding you second question, I assume that alembic exports a geometry and not an instance, so Blender reads geometry and not particles, so I guess that's why you have multiple objects. You should export particles from Houdini and then make your instancing in Blender rather than what you're currently doing, the alembic will be lighter and you'll have real instances instead of thousands of geometry objects.

 

Cheers,

[WAV94]

18 hours ago, jdiazsaezwd said:

Hello, I'm, no master on the matter, don't know why particles are being replicated at the origin, you can get rid of them with a simple delete node with a bounding box in sops, or directly in pops. As for the alembic export, there is a node called packpoints, which may help with with the times but you would need to unpack in blender I think, don't really know the workflow for that. Hope it helps

The points are created in the DOP network, and you can't use the blast node in there to delete the generated points, unfortunately.

18 hours ago, DonRomano said:

The particles going at (0,0,0) may be some deleted particles in the sim that the instance node try to retrieve and then it just pop some particles at (0,0,0) to keep the @ptnum logic. For instancing use the @id attribute instead of @ptnum attribute, it should resolve this.

Regarding you second question, I assume that alembic exports a geometry and not an instance, so Blender reads geometry and not particles, so I guess that's why you have multiple objects. You should export particles from Houdini and then make your instancing in Blender rather than what you're currently doing, the alembic will be lighter and you'll have real instances instead of thousands of geometry objects.

 

Cheers,

Alright, so how do I make the POP Instance node use @id instead of @ptnum?