$.systemScale = 0.5

Largely inspired by the work done in the movie 2012, I did some tests on how some FumeFX (1.x) parameters would affect a crawling smoke simulation.

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The following tests were set up to use a Gravity Vector object pointing towards the side, thus creating the effect of crawling smoke.
Grid Size is on average @ 300x300x300.
Simple Src with a disabled Smoke Channel emitting Fuel.
“Fuel Creates Smoke” checked.

(Tip: When playing the videos over at the Vimeo site, you can press spacebar to Play/Pause the video.)
(Tip 2: You may also just download the MOV videos from the Vimeo site.)

1. Smoke – Density | Diffusion
- High Diffusion for softer/fluffy smoke
- High Density seems to have affected the smoke movement.

2. Smoke – Density | Gravity
- High Density also seems to prevent the smoke to expand.

3. Grid Spacing & System Scale*
- To see smoke details on a small SystemScale setup, use small Grid Spacing.

4. Grid Spacing & Advection Stride
- The Grid Spacing doesn’t seem to have a significant effect on Advection Stride. (Also see #8)

5. Grid Spacing & Time Scale
- It is generally a good practice to have higher Time Scale values in order to bring out more details.

6. Grid Spacing & Vorticity
- High Vorticity will add more details.
- Low Vorticity, smoother smoke.

7. Advection Stride & Vorticity
- In the case of this scene, a Vorticity setting of 1.0 is not recommendable as you loose a lot of detail.

8. Time Scale & Advection Stride
- The Time Scale also doesn’t have a significant effect on Advection Stride. (See #4)

9. Time Scale & Vorticity
- Time Scale helps to impose the sense of scale.

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* The System Scale parameter is only accessible through MaxScript. Here’s a quote from Kresimir Tkalcec from the Afterworks forums:

“Some params that are visible from MXS and not documented are not officially supported, and/or they’re used internally.”

To set the parameter say to a value of 0.5, simple select your FumeFX Grid Object and enter this to the Listener:

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Test Animations:

Crawl Smoke Side

Crawl Smoke Alley

Crawl Smoke City

Crawl Smoke Wispy

Crawl Smoke Front

Additional Video: Large Scale Crawling Smoke

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