FumeFX – Crawling Smoke

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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Scene Setup:

• I’m using 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.
• “Fuel Creates Smoke” checked. (This was renamed to “Fire Creates Smoke” on newer versions 2.x?)

The Comparisons:

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 smaller 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, simply select your FumeFX Grid Object and enter this to the Listener:

$.systemScale = 0.5

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Test Simulations:

Crawl Smoke Side

Crawl Smoke Alley

Crawl Smoke City

Crawl Smoke Wispy

Crawl Smoke Front

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