TV Reel 2011
Japan Reel 2011

http://limjeff.wordpress.com/works/

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.

* 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:

$.systemScale = 0.5

Test Animations:

Crawl Smoke Side

Crawl Smoke Alley

Crawl Smoke City

Crawl Smoke Wispy

Crawl Smoke Front

Additional Video: Large Scale Crawling Smoke

Quote from the FumeFX 1.2 help file:
Vorticity - This parameter is very useful for coarse grids, where simulations lack detail.  When you increase grid detail then the need for vorticity is lowered, since the simulation itself will result in more detail.  Higher vorticity will increase the number and strength of small vortices in the fluid.

Spacing - This parameter directly affects the detail level in your simulation.  Type in or use the spinner to set the spacing of the voxel-based grid.  The chosen value defines voxel size; smaller voxel size allows for more voxels in simulation, which produces greater detail.

@ Frame 40

@ Frame 80

Animation on Vimeo

Notes:

• It can be clearly seen that with very coarse grids (large values), adding Vorticity can drastically change the fluid.
• I also noticed that 0.5 Vorticity gives the highest simulation time, and 1.0 Vorticity the lowest. Here is a graph representing the time curve:

Quote from the FumeFX 1.2 help file:
Cubic interpolation - If you need maximum quality, you will want to check this option.  Simulation times will rise considerably, but less dissipation will occur and more swirls will be created.

@ Frame 40

@ Frame 80

Animation on Vimeo

Notes:

• With Cubic Interpolation turned ON and an Advection Stride of 0.01, one can expect very long simulation times.
• Smoke seems to traverse the grid more with Cubic Interpolation OFF.
• Increase in quality is hardly noticeable with Cubic Interpolation ON.

Normal Grid / Partitioned Grid

FumeFX Partitioner

current version as of 2010-feb-11 is 0.10

This script will divide a FumeFX Grid into partitions. The script is divided into two parts, one for partitioning, and one for simulating the partitions.

Partiton Options:

Partition Options Group

Pick FumeFX Grid – Select a FumeFx grid that you wish to divide into parts.
Holding down the ALT button will select whatever FumeFX Grid object you’ve selected.
Holding down CTRL will clear the selected item and delete it’s corresponding Preview Objects and Layers from the scene.

Grid Count -  Shows the number of grids that the script will generate. (X*Y*Z)

Length/Width/Height (X/Y/Z) – Set the number of partitions on all 3 axes.

Overlap - This is the overlapping space between the partitions. 1 unit of overlap equals the spacing size of the picked grid.

Display Preview – Displays a preview (in the form of frozen box objects) of the partition settings in the viewports.

Create Layers – Will create a separate Layer for the generated grids.

Create Selection Set – Will create a Selection Set for the generated grids.

Pick Folder Path – Choose a base folder path on where to store the FXD cache files.
Hold ALT to open the chosen path in an explorer window.

Create Partition – This will generate the partitions using your settings above. The created partitions will then be automatically added to the Simulation FumeFX List.

X – This will simple delete the generated partitions.

Simulation:

Simulation Group

FumeFX List – This is where items (FumeFX Grids) for simulation is placed and arranged.

+/- -Add or remove selected items from the list.

Up/Down – Move selected items in the list. You can select multiple items to move around.

Network Simulation – Turn this ON to send separate partition jobs to Backburner.
This method uses the command line method of submission (3dsmaxcmd.exe).

Manager Name – Set the manager name to send jobs to.

Initially Suspended – Sends the jobs as suspended. It is recommended that you set this to ON, because there’s no way to assign servers using the command line. You must assign the servers for the jobs using the Backburner Manager.

Priority - The priority of the job as it is queued by the manager.

Platform - switch between 32bit or 64bit servers.

Simulate Locally – This will simulate the FumeFX Grids on your local machine, it will follow the FumeFX List as the sequence starting from the top. It will also print out a summary of simulation time in the listener after it has finished everything.
This button is visible if you have Network Simulation Turned OFF.

Send Simulation – Send each partition to Backburner as separate jobs. A command prompt window  showing each file getting sent will appear.
This button is visible if you have Network Simulation Turned ON.

* More notes on Send Simulation at the bottom. *

Some Use Cases:

* Cases shown here were all done on a 32bit machine, 2Gig ram (3Gig switch ON) *

Case A: Thin Trails

Preview

Original Grid:
100x100x100 @ 0.2 (500x500x500)
4888 mb

Partition Settings:
4x4x4 Parts | 64 FumeFX Grids

Partitioned Grid:
29x29x29 @ 0.2 (145x145x145)
120 mb

Thin Fire Trails

Thin Smoke Trail

Case B: Straigh Trails

Long Smoke Preview

Original Grid:
100x1000x100 @ 0.45 (222x2222x222)
4282 mb

Partition Settings:
1x15x1 Parts | 15 FumeFX Grids

Partitioned Grid:
109×75.667×109 @ 0.45 (242x168x242)
385mb

Long Smoke

Don’t Use Cases:

Case C: Buoyant Fluids – data won’t transfer well to neighboring grids.

Bouyancy Wire

Bouyancy

Case D: Turbulent Grids – notice the obvious  separation.

Turbulent

Turbulent

Misc:

Use Container Edges Falloff - This helps smooth out the overlapping edges of the grids, slightly eliminating the separation visible n Fig A below.

Grid Wireframe

Fig A - Falloff Type: None

Fig B - Falloff Type: Box (Strength 0.25)

Considerations:

• Use this method on scenes with low or zero fluid motion.
• Avoid having a smoke that would travel to a neighboring grid because of turbulence/gravity/bouyancy.
• 32bit machines will be able to better handle the sim because of partitioning.
• Can be simply used as a Batch Simulation tool.

Notes on Sending Sim to Backburner:
*** I haven’t fully tested the Network Sim feature, I might rewrite the way it sends jobs to the server, use with caution ***
- After pressing  Send Simulation, the script will save out multiple max files (set to simulate a single grid partition) on to a temporary location.
- Then a batch window will appear utilizing 3dsmaxcmd.exe to send max files as jobs on to the specified server.
- The strange thing is, the jobs would use ALL SERVERS by default, so it is recommended that send the files as Suspended. Assign the servers yourself from Backburner.

macroScript Select_PF_Nodes
category:"Particle Flow"
buttonText:"Select PF Nodes"
tooltip:"Select PF Nodes"
(
pf_sources = for i in $* where (i.classid)[1] == 1345457306 collect i
pf_events = for i in $* where (i.classid)[2] == 515064576 collect i
pf_actions = for i in $* where (i.classid)[2] == 515064320 collect i
deselect $*
selectmore pf_sources
selectmore pf_events
selectmore pf_actions
)

This also let’s you collect all the Particle Flow nodes on to a single layer. Occasionally the nodes can become scattered inside your layers which often leads to the ff:

• Particles operators getting deleted accidentally.
• Particles not showing in the viewports because the Display Operator is on a different (hidden) layer.
• Layers having invisible items.

The script is a Macroscript, run it once and go to your Customize User Interface dialog, under the Keyboard tab, look for Select PF Nodes inside the Particle Flow category.

$*.material = undefined

Running the script will simply clear out and/or delete all the materials assigned to objects in the scene. It doesn’t include maps and materials that are  assigned to button parameters like the Environment Map.

Quote from the FumeFX 1.2 help file:
Advection Stride - The lower this stride is, the less dissipation of velocity and smoke will happen. It is a more or less inverse proportion to simulation time.

TIP: For smoke with many small curls you may want to decrease this number to 0.1 or less.

Vorticity - This parameter is very useful for coarse grids, where simulations lack detail.  When you increase grid detail then the need for vorticity is lowered, since the simulation itself will result in more detail.  Higher vorticity will increase the number and strength of small vortices in the fluid.

@ Frame 30

@ Frame 80

Here is a link to the animation on Vimeo.

Notes:

• The Advection Stride becomes more noticeable with higher Vorticity.
• Advection Stride lower than 0.1 (< 0.1) results in lower simulation times.
• Lower Vorticity, Bigger Curls.
• Higher Vorticity, Smaller Curls.

(Please feel free to post some of your observations regarding these parameters, I will be very happy to hear them)

Here are a few ways to tackle this…

(Updated: March 06, 2011 – Added methods 5 & 6)

*** Created/Tested on FumeFX 1.x ***

1. Large Static Grid

One way to simulate the fire is to create a very large grid which would encompass the boundaries of it’s movement.

You could download a free script by Allan Mckay at ScriptSpot called Create Animation Bounding Box.

Here’s a short description from the site:

The idea is that I wanted to roughly work out the entire dimensions of a characters animation, so a bounding box – of the entire animation.

Also note the reply by Anubis for his version, which seems be much simpler and faster.

2. Isolate Bounding Box Script

This next one also uses a very large grid, but it will need to use a script inside FumeFX to isolate only the voxels inside a bounding box object.

Here are some requirements:

• An object (Preferably a Box) to be used as the bounding volume.
• The box can be linked/animated to follow the object you want to burn.
• The box shouldn’t have any rotations whatsoever.
  

  BBox Alignment

Download the script FumeFX – Object Bounding Box Script, and assign it to FumeFX.

MaxScript Assignment Rollout

Press Edit and replace the contents of the original script with the script provided above.  You will then need to edit the encircled parts of the script:

Set the $'BBox' (in red) to the name of your bounding box object.
Lastly, set the $'FumeFX01' to the name of your FumeFX object.

Object Bounding Box Script Snippet

note: You could skip setting the name for the FumeFX object, just comment out line 26 of the script, and uncomment line 25. I did that because I had some problems with the script where the built-in ffx variable didn’t return the proper FumeFX object, so a direct assignment of the node by name was the safer approach.

Here’s a preview of the resulting simulation.

FumeFX Simulation Preview

You can take a look at the Log window being generated by fume as it simulates, look for the ones with “–>”. These are infos generated by the script.

FumeFX Log

If you then try to not use the script and simulate the scene in a 32bit Windows environment, you will likely get a crash as I did.

Out Of Memory Error

Essentially, whenever doing simulations, it is largely recommended to do it on a 64bit environment, as you’ll be able to better maximize your memory usage.

Some pros with this method aside from being able to simulate with very large grids is that you will most likely always get a constant simulation speed per frame.  Looking at the FumeFx Log image above shows that the isolation time is a constant 7.0 per second.

The drawback is that the voxels outside the Box volume will definitely get deleted. So this method is obviously not suitable for large pluming smoke sims.

max 2009: fume-bbox.zip

3. Grid Lock

This method also makes use of a script, and in way, is similar to method #2 above.
The Idea was to be able to directly animate the FumeFX grid object itself.

You start off by animating or linking the FumeFX grid object to an animated object.. as with the Bounding Box method, you’re not allowed to have any rotations for the animation.

As an example, I linked the FumeFX grid to a Point Helper that is linked to the animated object. I used a Point Helper to help center the pivot of the FumeFX grid, since the grid always has it’s pivot at the base.

I then used this Baking Script called Tera Bake Transforms which has an option to retain a constant grid alignment even if it’s moving around the 3d space.

Tera Bake Transforms Script

This script simply bakes any object animation into keyframes.

A special option that it does is called the Snap Positions. Using this option when baking, you can snap the animation positions to values that are divisible by the specified amount.
(The resulting comparison image below might better explain what this option does.)

The Get button is a special button to quickly get the Spacing value of the selected FumeFX Grid.

Here’s the result after baking using this script, with and without the Snap Positions checked:

Baking with Snap Positions OFF/ON

Notice the seemingly non-moving grid with the Snaps ON.

With the positions snapped to the spacing value, we could then proceed to assigning a script to offset the voxel data based on the grid emitter movement.

Download the script FumeFX – Grid Lock and place it to your FumeFX maxscript section.

Now we can proceed with the simulation…
Here’s the result using the same scene from the method #2 above:

FumeFX Simulation Preview

This method took a bit longer to simulate compared to method #2 for this scene.

Including doing other tasks while simulating in the background (300 frames):

• method #2 -  37 mins
• method #3 – 47 mins

max 2009: fume-grid_lock.zip

4. Cut-Off

This method can be found in the Afterworks forums. It also uses a script to delete voxel data that falls below a specified user threshold. I think it is also available in the CGFluids website.

5. Void Src

If you have FumeFX 2.x, you can make use of a new FumeFx Helper called the Void Source. It essentially works like methods #2 & #3 above. But with the convenience of it being a non-scripted approach, plus you’re allowed rotations.

6. Script by lutteral @ CGTalk

Also worth noting is a script done by lutteral which was based on the Isolate Bounding Box Method above (#2).
Click here for the link to the Thread.
The script can be found on the 3rd post.