pop emission issue

[mrWolf]

I created a very simple pop sim, where I emit particles from a previously cached particle sim.

 

I notice that the amount of particles emitted gets less and less in time. I couldn't find any possible explanation for this.

The only workaround I found is to key the Impulse Count so that it increases a lot with time, but I'd love to understand the reason why this is happening.

 

Has anyone experienced anything like this or maybe there is a known bug in this version of Houdini ?

I am using H13.0.476.

 

hip file attached.

 

 

pop_emission_issue.hip

[loopyllama]

Hi Mr. Wolf,

Your second popnet creates 1000 particles and your first popnet (the source) has 3 particles. This means you see nice streamers behind each point because there are about 333 for each primary particle. As time goes on your source popnet has more and more points, more than 1,000. You still are creating 1,000 secondary particles, so your nice streamers are down from 333 a source point to 1 per source point.

 

What you want to do is set up a ratio. You want to create secondary particles at the rate of n per source point, let's say 100 per source point. We can get the source point count with the npoints expression.

 

To fix your scene, in your dopnet2 popsource 1 impuse channel, change the 1000 to npoints("../../OUT_sourcePoints")*100

 

Now you will get 100 secondary points per cook per source point.

[mrWolf]

Hi Loopyllama !

it makes perfect sense, every ~1 month I tend to forget how particles are emitted in Houdini !

Thank you a lot for the explanation, it works great now!