Flame detail scale

[jordanw]

What would be the best method for reducing the scale of flames? I have settings that give me a decent looking flame motion but they are way too big. Here are some settings:
timescale: 0.5
Advection Step: 4.0
Vorticity: 0.5

Im playing around with advection and vorticity, but not getting where I want.

[Ivaylo Katev]

the scale of the scene is the most important, the time scale gives the same effect. or may be the question is not about this?

[jordanw]

im using the time scale to get the speed correct, but the physical size of the flame detail is too big. I want to reduce the size of the flame detail (the size of the vorticity) by half.

[Ivaylo Katev]

i got it, but there small scale details tends to disappear and this is general issue of the grid simulation. you can try the mapping, compose a three component noise texture and set it to attract the velocity.

[wxyz]

Can you explain the 3 component texture in more detail?

[Ivaylo Katev]

when the velocity is attracted by map, the r component influences the x component of the velocity etc. set to each rgb component a noise texture, and set to these textures different seeds, to avoid their correlation, this will produce turbulence like force.

[wxyz]

Is this done with Explicit map channels?

[Ivaylo Katev]

no, world or object. during the simulation you can't use the uvw channel, that is needed for explicit mapping.

[wxyz]

Do you use Bercon Noise to get the 3 components?

[Ivaylo Katev]

this was just a suggestion, try any type of noise, but do not expect miracles at all. the fine details tend to disappear and this is a fundamental problem of all the grid based solvers.

[wxyz]

RGB multiply with the map affecting the alpha seems to work well

[Ivaylo Katev]

yes, but this is a render time effect. i think the question was about how to affect the simulation

[jordanw]

yes, it is about the sim... I dont think my grid size is small enough to lose the flame detail. What about the other way then. What if i did some flames then the director came to me and said "The flame scale is too small, make the flame scale 2x as big, but dont affect the speed, or the volume they take up" how would you try to achieve that?
like the difference between these two photos:

[Ivaylo Katev]

I dont think my grid size is small enough to lose the flame detail.

the smallest details are not equal to the cell size, they are bigger with a constant. so if the vorticity and the advection do not give the desired effect, i think the only real solution is to increase the resolution of the grid. even this does not guarantee that the general movement will remain the same, because the vorticity is not scale invariant. my observations are that for keeping the flame behavior you have to increase the vorticity
the attached images i made using the same settings, with doubled resolution and doubled vorticity for the second one. the behavior of the fire looks the same, but if only the resolution is doubled the fire does not look the same.