Reduce the number of particles MAGMA

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  11 November 2013
Reduce the number of particles MAGMA

Hi everyone, is there any way of reduce the number of particles with magma? Im creating some bubbles for a beer and I currently have a lot of particles and I need a bit less.

  11 November 2013
If you are using a PRT Loader, you can just tell it to only load a % of particles.
  11 November 2013
Yes, but it does not give me a uniform distribution of the particles, for example, if I just load a 50% of the particles, what I will get is the particles slice for the half.
  11 November 2013
Ah no I just realice that changing the rendering to Load Every NTH by ID is the way to go.

Thanks man
  11 November 2013
I was just going to ask you this, then saw that you noticed the Every Nth Option. No problem.
  11 November 2013
For completeness, yes, you can also use Magma to reduce the number of particles, but that is useful typically when you are using some more complex logic than just the ID of the particle. For example, you could reduce particles based on proximity to some object's positions or mesh's surface (e.g. reduce more in the center of the glass than around its walls), or based on any channels that might be in the particle stream...

Basically you can set the Selection channel to 0 for not-selected, 1.0 or higher for fully selected, or to a value between 0.0 and 1.0 for semi-selected. Then drop a Krakatoa Delete modifier above the Magma, and it will delete selected particles (Selection > 0). If there is an ID channel and you switch the radio button in the Delete modifier to use Soft Selection, particles with semi-selection will be deleted with that probability - for example a particle with 0.5 Selection value has 50% chance of being deleted, a value of 0.1 means only 10% chance for deleting etc. Thanks to the ID channel, the deleting by probability will always delete the same particles on all frames... If there is no ID channel, the Index channel will be used instead without guarantee that the same particles will be deleted on every frame.

Hope this helps.

Last edited by Bobo : 11 November 2013 at 05:15 AM.
  11 November 2013
Thanks Bobo, great explanation.
  11 November 2013
Just to add to this, I was just doing the exact thing that Bobo was describing. I needed particles to stick to a surface - but ONLY if the main geometry was at a certain distance.

In my case I needed the particles to be arbitrarily placed so the default PRT Surface was fine. Then I made a distance threshold of "x distance" - anything within the threshold stuck to a surface, anything farther was selected and deleted. Worked perfectly.
  11 November 2013
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