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Message 1 of 7
900 Views, 6 Replies


I'm running Maya 2019.  I'm new to bitfrost. I can't get bitfrost to simulate rain.  I've tried a variety of physical models (propellers, sieves) on liquid to get droplets to form, but bitfrost seems to want to keep the liquid in sheets or strands and not break up into bits of water.  What I want is to get the effect of rain falling on animated objects partially submerged in water.  I want the rain to splatter off the objects as well as to disturb the water (ripples).  I haven't seen a tutorial on this.  I realize scale is critical to getting the correct effect.  I tried a variety of  gravity magnitudes (9.8 to 980) physical attribute densities ( 1 to 1000), droplet thresholds, and surface bandwidths. Any suggestions as to how to proceed would be welcome.



Message 2 of 7
in reply to: matthewGNQTJ

I also have the same problem, does anyone have any ideas on the subject?



Message 3 of 7



This will be very expensive (in terms of memory requirements and computation time) to do as a single simulation. I suggest that you break it up into separate effects and blend them together in post production. This approach will also give you better control over the different parts.


  • For medium-distance regions where you can't see the individual drops, you can use a BOSS mesh for the water surface and an animated texture for the rain. See Add and edit BOSS influences.
  • For close-ups where you want to see the individual drops and resulting splashes, keep the simulated region as small as possible. You can emit from a number of small simple meshes like cubes or spheres for the rain. To get good splashes, you may need to enable surface tension and increase the number of frames per second. Be forewarned that this will take a long time to compute.
  • For the background, blur and fog are your friends :).

Good luck!


Grahame Fuller
Learning Content Developer
Message 4 of 7

Thanks I'll try


Message 5 of 7

A kludged solution:


Use nParticle1 as points.

Have nParticle1 collide with objects in bitfrost puddle, but not the bitfrost.

Create nParticle2 from collision (I wasn't concerned with bitfrost interacting with these secondary droplets; it would never be noticed).

Convert nParticle1 to Output Mesh (polysurface)with long Motion Streak.

Make polysurface collide with bitfrost.

Basically used Glass Ai shader for polysurface.

Hope this helps.


Message 6 of 7
in reply to: matthewGNQTJ

Many thanks, now I am also trying with Bifrost Graph particles, it look interesting ...

Message 7 of 7
in reply to: arboitlucio

I realize I forgot to mention that you need to nCache the entire animation for nParticle1 before you convert to polysurface, because the polysurface animates on the nCache and is incapable of generating its own animation. 

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