Help Particle size over lifetime

[Barbelot]

Hello,

I am trying to create a constant stream with Obi Fluid with a source that emit constantly.
However I run into an issue where the particle removed as they reach their lifetime limit create visible blinking as they disappear instantly.

Here is a gif of the issue : https://imgur.com/Pzgkvnh

Is there a way to make the particles fade out in size or color as they reach their death ? Like a size over lifetime or color over lifetime parameter ?

Have a nice day !

[josemendez]

Hello,

I am trying to create a constant stream with Obi Fluid with a source that emit constantly.
However I run into an issue where the particle removed as they reach their lifetime limit create visible blinking as they disappear instantly.

Here is a gif of the issue : https://imgur.com/Pzgkvnh

Is there a way to make the particles fade out in size or color as they reach their death ? Like a size over lifetime or color over lifetime parameter ?

Have a nice day !

Hi,

I'm aware of this. In a fluid simulation, it's not easy to dynamically change the size of particles. This is because each particle interacts with its neighborhood using a support function (a normalized kernel), whose normalization factor is precalculated for performance reasons. Dynamically changing the size of a particle would require to recalculate and re-normalize the kernels at runtime, which can be expensive. Skipping renormalization entirely would result in pressure spikes, which are highly undesirable.

Fading their color out would not solve the issue, as you'd see a part of the fluid become progressively clearer, then pop out of existence. If anything, it would make the issue even more jarring.

As of now, there's no way to prevent this "popping". Will investigate ways to reduce it for future updates.

[Barbelot]

Oh ok. Thanks for the explanation.

Since it is just for a short time at the end of the simulation, would it be possible to have a fixed size for the all the physical simulation and only change the rendering size of the particle ? Basically being able to change the Radius scale of the renderer but on a per particle basis according to their age.
This would lead to incorrect visual results when the two sizes do not match but might be less jarring than the popping if it is only for a second or less at the end of the particles life. Wouldn't it be even less visible with the fluid rendering since the particles are blurred together ?

Thanks for your help !