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About System Scale

In FumeFx, you can control the System Scale with a script, but I don't quite understand the impact of this operation, so I'd like to ask for your help.
Is it the "unit" of the system that is changed by System Scale?

--In the case of Spacing
When the spacing is 1cm, 1voxel is formed by the following equation.
If the System Scale is 0.1, does 1voxel become as follows?

--In the case of Velocity
In the case of Velocity is 1cm/s, if System Scale is 0.1, velocity will be 0.1cm/s?

--In the case of smoke density
If you change the System Scale, will the density of the smoke be as follows? The unit is not specified in the user guide, so I am guessing. Is this the correct unit?

If the amount of smoke is 1mg (mass) and 1 voxel is 1cm^3, then the density of smoke is 1mg/cm^3.
If the System Scale is set to 0.1
Therefore, the density of the smoke is as follows
1(mg)/0.001(cm^3) = 1000 (mg/cm^3)

This means that the density of smoke is 1000 times higher when the system scale is 0.1 than when the system scale is 1. (When the system scale is set to 0.1, the smoke becomes surprisingly dense.)

--Difference from Time Scale
Please tell me the difference between System Scale and Time Scale.

I'm sorry for asking so many questions. I would appreciate it if you could answer my questions.
Hello Jumpei,

Thank you for your questions.

The systemscale is just used to internally multiple the gravity, internal tubulent noise scale and rendering.
In rendering it is a linear transform, not a volume(cubic).

TimeScale is used to accelerate or decelerate simulation, but you can also change the simulation speed with Retimer in
a more predictable way as Time Scale alters the simulation look.

You're welcome to ask any questions you might have.

Best regards,
Kresimir Tkalcec
Hello Kresimir.

Thank you for your reply.
I don't fully understand it yet, but I will try it in various cases and see how it behaves.

If you want to achieve bigger scale, then you can just lower the gravity as this would make fire/smoke to rise/fall slower.
In the case of the sources, lower the velocity as well.
It all depends in what you want to achieve.

K:resimir Tkalcec
Hello Kresimir.

I am still having trouble understanding the system scale.
I still do not understand the system scale.
Under the same conditions, when the system scale is 1.0 and when the system scale is 2.0, the smoke rises faster at 2.0. I do not understand this logic.
As a simple example, if the grid size is 100cm*100cm*100cm, the spacing is 1cm, and the smoke rises at a rate of 1m/s, and the system scale is set to 2.0, the grid size of 100cm*100cm*100cm in the viewport will internally be 200cm*200cm *200cm, which I thought would make the smoke appear to rise at a relatively slower rate.
However, the smoke actually rises twice as fast.
What is changing by changing the system scale? I would appreciate it if you could explain the logic clearly once again.
Thank you.
Can someone please respond to the above?

The system scale just alters the gravity value - that's all it does.
It's undocumented scripted value and never intended to be actually used.

Kresimir Tkalcec

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