nParticle and nCache substeps

#1

Hi everybody,

I’m doing some tests with nParticles with vray and I have one problem with the rate of my emitter and an other one with the nucleus wind noise.

  • First one : Emitter rate !!

To have a correct motion blur with vray I have to evaluate my ncache every X frames.
But if I evaluate every 0.2 frame, my emitter generate lot more particles !!!
So I thought I juste have to multiply my rate by 0.2 to have my number of partilces back but it seems it’s not the correct math !

Here is some infos I found.

for an emitter with a rate of 800, after 100 frames I have a total of 3299 particles
To have the same number of particles with different evaluation, I found this :

evaluate every 1.00 frame = rate 800
evaluate every 0.50 frame = rate 533.333 >> 800/533.333 = 1.5
evaluate every 0.20 frame = rate 266.666 >> 800/266.666 = 3
evaluate every 0.10 frame = rate 145.454 >> 800/145.454 = 5.5

So there is not logic for me :frowning:
Is there anybody who can explain what is the math behind this ???

  • Second one : Nucleus wind noise with the ncache substeps

Here is my second problem link to the first one ! I found that If I use the nucleus wind noise and ncache my particles with evaluate every 0.2 frame or any value under 1, my simulation change !! I multiply the noise wind by different value but I can’t find the correct value to have the same simulation behaviour.

So I also need your help to find the math to fix this :slight_smile:
Maybe it’s a question for Duncan ?!

Thanks a lot for your help !!

#2

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