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+--- Thread: Help Controlling speed of emitter particles (/thread-4550.html)
Controlling speed of emitter particles - Aroosh - 06-09-2025
Hello
I am using Disk with ObiEmitter to emit particles and I see that speed and amount of particles spawned are correlated in Stream mode.
Is there any easy way to change velocity of emitted particles and amount of emitted particles separately such that we can get slow moving fluid stream that is still contiguous and not a sequence of drops?
Thanks
Aroosh
RE: Controlling speed of emitter particles - josemendez - 06-09-2025
(06-09-2025, 12:41 AM)Aroosh Wrote: Hello
I am using Disk with ObiEmitter to emit particles and I see that speed and amount of particles spawned are correlated in Stream mode.
Is there any easy way to change velocity of emitted particles and amount of emitted particles separately such that we can get slow moving fluid stream that is still contiguous and not a sequence of drops?
Thanks
Aroosh
Hi Aroosh,
No, that’s physically impossible. The defining characteristic of fluids is that they have constant density, that is, the amount of mass per volume unit is always the same.
For this to hold, the distance between particles must be approximately constant. If you reduce emission speed, you must also reduce the amount of particles emitted per second, otherwise they’d pile up causing a pressure buildup and the fluid would explode. Conversely, if you increase emission speed, you need to increase the amount of particles emitted per second to ensure there’s no gaps between them. So emission speed and emission rate must be linked.
This is what happens in a real world faucet: open it up, and you get more fluid that also comes out faster. Close it, and you get less fluid that comes out slower.
Note that fluids in Obi (and all existing simulators) are a discrete approximation of a continuous material, so at slow emission speeds, each frame you either get a particle spawned or you don’t: the only way to make the stream more continuous is to increase discretization resolution, that is, have smaller particles that represent a smaller volume of fluid each. This of course increases the cost of thr simulation.
Kind regards,