FumeFX-Smoke Settings

Hopefully this will help make setting your Smoke Parameters a little easier.

Minimum Density is for instance if you have 10.0 values of smoke (example: you generate smoke with a simple source at a set value of 10.0) in a voxel, if your Min Density setting is at 5.0, the smoke will only begin to dissipate when the voxel contains 5.0 or less values of smoke.

This density value is constantly changing because of forces that are imposed on the grid like gravity/buoyancy/temperature/turbulence/spacewarps/ect. So it there were absolutely no forces to move the smoke around, the smoke in the 10.0 value voxel the smoke would never ever dissipate.

The Dissipation Strength Value is the easiest one to understand, it is simply how fast the smoke is going to dissipate once the Minimum Density value is reached. So going to the above example setting of 10.0 values of smoke in the voxel and a Dissipation setting of 99.999 if the smoke density in the voxel never gets to 5.0 it will never dissipate. BUT as soon as the smoke density in the voxel goes below 5.0 the smoke will immediately dissipate.

Diffusion simply diffuses the voxel much like adding a blur to a pixel in Photoshop. That is the only way I now how to explain it. The blur has the most density in the center and has a falloff to zero at the outer edges. So adding Diffusion takes that value of 10.0 and spreads it out (according to whatever algorithm it uses). Also note when you use diffusion it is constant, so the original voxel that contained 10.0 values of smoke is now spreading to neighboring voxels populating them with smoke, which are then being diffused again, and spreading to the neighboring voxels and so on.

Here is a little illustration to help:

14 Comments to FumeFX-Smoke Settings

  1. thx for this information JR ^^

  2. b.aboubakr on July 8th, 2010
  3. Thank you very much for your explanation. Very usefull indeed. I was straggling understanding these settings.

  4. daniel on August 24th, 2010
  5. hey johnny you should put the video on loop mode!
    its great-

    question- theres this one fume kraka tutorial where he has smoke gathering at the bottom, i tried the tutorial but it still rises, whatever i do
    boyancy at 0 even gravity on, but it still rises

    how to make the smoke gather in a box at the bottom of a sim?
    (waiting for it to be knocked down by other objects)

  6. ian on November 10th, 2010
  7. There are a couple of settings you can mess with.

    Increase your smoke density, this will make you smoke in effect, heavier.

    Adjust your temperature, try to imagine the actual temp of the smoke you are try to reproduce

    Emitter velocities play a huge role, no matter what your other settings, your emitter velocities will always induce motion. Just lower them, generally 0.0 is too low, but something like 0.1 or so

    Your emitter type is important too, for instance if you are using a simple source, you will want to generate your smoke then move it out of the way, this will keep the emitter itself from dissipating stationary smoke.

    Hope that helps 🙂

  8. admin on November 10th, 2010
  9. Very nice clip describing how the setting affect the effect!

  10. Danilo Buendia on April 27th, 2011
  11. Hi,

    Do you know any way to make a smoke generated by a particle source that is affected by forces to last for ever?


  12. Carlos on March 13th, 2013
  13. Well you can zero out the Dissipation value. The thing is you can make it last for ever, the problem lies within keeping its shape. Temperature, velocity, gravity, buoyancy, vorticity, all work against you, they constantly effect the fluid. So after a while you end up with pretty much a soft smokey blob with no details.

  14. admin on March 13th, 2013
  15. OK John,

    Many thanks for your answer.

  16. Carlos on March 19th, 2013
  17. plz give some parameter for large scale fire and smoke.

  18. 14Kk on June 29th, 2013
  19. Well it is a balance of params BUT it is more of a method of thinking. For instance when you look at a smokey fire or explosion from far away something strange happens, things actually look slower than they actually are (given the phenomena is large enough)

    Try lowering your gravity and buoyancy rates. Play with the timescale, add a couple keyframes to it (just don’t go much below 1.0 it will muddy up the advection). Inject a lot of fluid in the grid, dense fluid moves slower. It takes experimentation to get it the way you want.

    You can also use the MXS .systemScale param, although I would only recommend this when you have a firm grasp on what is happening within your fluid sims. You can get great results when you know what your doing BUT you can also screw things up royally if you don’t. You have been warned 😉

  20. admin on June 29th, 2013
  21. Plz help to realistic car blast ?
    Plz help.

  22. 14k on July 7th, 2013
  23. Seriously? Could you be more vague? That is like asking “How do I model a car?” That is a workflow not just settings.

    Dude do some research there is a ton of this stuff out there. What did you do with the last info I gave you?

  24. admin on July 7th, 2013
  25. Ive been researching the best method to attain a cigarette smoke look that would come to exactly this kind of esthetic:


    I recently bought Fumefx thinking I could get this effect and look. Could you point me in a few directions that I should adjust to achieve this? Im close to the form but not at all getting the fluid curls and transparency that I need.

    It keep coming out to “foggy”

    Much obliged

  26. John Bellamy on October 1st, 2013
  27. Thin smoke can be tough. That said some things to think about generally point to the render shader. Go to the Render Tab. You can get rid of a lot of the softness by lowering the high threshold and adjust the AFC curve on the smoke to get rid of less dense smoke and only render the thicker bits. It is what I have done here: https://vimeo.com/15046313

    Other sim based thing to consider are things like the gravity/buoyancy, play with them in equal parts. Turbulence, it is map based, adjust the input values (the X Y Z values) and the maps scale to find a match that you are looking for. Grid spacing, fine smoke doesn’t require a super tight voxel but it does need to be good enough to pass nice advection, you want you advection repetitively lower so the fluid doesn’t progress too quickly in the buoyant direction. You want it to linger.

    Man there is a ton of other stuff from turb with particles to using effectors. Just take your time and iterate a lot! save all you iterations you may find down the road a bunch of sims later you liked what you were doing 10 or 15 sims prior to current. Also something I like to do is keep a simple spreadsheet with the scene iteration and watch changes I made from the base sim, this is really helpful to get a good solid idea of how the solver works.


  28. admin on October 1st, 2013

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