# Help with smoke simulation scaling and appending

I am putting together a preset pack of different types of smoke simulations (explosions, candle flame, after burner, exhaust etc... )

I would like the user to be able to append any of the smoke scenes to their scene. The only problem is if their scene is not to scale, when they resize the smoke sim to fit their scene it will drastically change what it looks like.

Is there some sort of Simulation scale feature they can use?

Or can anyone think of a creative way to help the user be able to scale the smoke sim and have it look the same at any scale?

Here are some examples:

Let's say this is the original sim that I always want it to look like.

This is a brand new blend file with the smoke scene appended, with the smoke sim copy and pasted to the new scene and scaled down (or up doesn't matter), the scaling has NOT been applied.

This image is the same but WITH the scaling applied.

In these examples there is not much of a difference between the NON-applied and applied samples (but even between these there are differences, especially with some of my other sims).

I understand that the scale affects how the smoke looks. The solution I am looking for is to have my original smoke sim to look the same no matter what scale the user uses.

I am using openVBD.

• "drastically change what it looks like": can you include pictures? Is the smoke a 3D texture or openVDB? – Jaroslav Jerryno Novotny Jul 13 '18 at 18:08

You need to adjust the density for how much you scale the smoke. If the original scale was 1.0, the new density is: $$density' = density / scale$$ If you want exactly same render result (from scaled camera closer/further from smoke), you will also need to adjust the Volume Sampling Step Size under Properties > Render Tab > Geometry: $$stepsize' = stepsize * scale$$