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Fluids

Fluids have been with Maya for many years, there is a newer utility called Bifrost. You may want to compare. I found Bifrost was not able to create a certain fire effect I was after.

Set up your Maya options for animation
Move the time slider over to frame 0 at the bottom of the screen.
timeslider_0

Change 24 fps to 30 fps over to the right on the time slider.
timeline_30fps


Lights
Add Lights to the scene. These will illuminate the smoke etc.



Basic Fire Tutorial
fx_module  
Use the FX Module

Fluids->3D Container->option
     Uncheck Add Emitter:

Select the fluid object
Attribute Editor
Container Properties
     Select Keep Voxels Square
     Base Resolution 40
     (default 10, higher for more detail and slower render)
     Size 5  15  5
     Boundary Y -Y side


Emitter Object
Add an object or more to the scene to emit fluids, place within the container.

Select the fluid, shift select emitter object(s)
Fluids->Add/Edit Contents->Emit from Object


Select the emitter, tab in the fluid or grouped under emitter object
Basic Emitter Attributes
     Emitter rate 100
     (default 100)
     Select Use Distance   (default not checked)
          Max Distance  3


     Fluid Attributes
          Density/Voxel/Sec   1
     (play with this, default 1)
          Heat/Voxel/Sec  2  (default 1)
          Fuel/Voxel/Sec    4   (1, default 1)
     Fluid Dropoff 2  (0, default 2)

     Keep Jitter checked     (maybe no difference)


Fluid Emission Turbulence
     Turbulence 1.2
  (1, default 0)



Fluid Container Settings
Select the fluid
Contents Method
     Temperature   Dynamic Grid
      (default Off(zero))
     Fuel   Dynamic Grid                   (default Off(zero))
     Falloff Method   Static Grid

Dynamic Simulation
     High Detail Solve  All Grids Except Velocity



Content Details
     Density
          Dissipation .2
     (default 0)    dies off faster
          Noise .5   (default 0)

     Velocity
     Swirl 10
    (default 0)
     Noise .1       (can be higher, default 0)

     Turbulence
     Strength  .01
   (default 0)

     Temperature
     Temperature Scale 
1    (default 1)
     Buoyancy 9 (default 3)
     Dissipation .1     (default .1)
     Turbulence  .1     (2, default .1)
     Noise 0     (1, default 0)





Fluid Shader Settings
You do not need to re-run the simulation for color changes.

Select the fluid
Shading
     Transparency .2
    (color value, default .25)
     Dropoff Shape  Cube  (default Cube)
     Edge Drop Off   .1     (This effects the height, default .05)


Color
     Selected Color .2
(default 1, white)


Incandescence
     Make the value of orange 15    (push the color selector over limit, default .7)
     Incandescence Input   Density
  (default Temperature)
     Input Bias  .1  (-.088, try various numbers, default 0)


Opacity
Make the ramp spiky, try different patterns.
Play with the Input Bias try .3  (this can make a huge difference, default 0))
fluid_opacity


Shading Quality
Quality  1    (default 1)
Render Interpolator  smooth    (default linear)



Textures
Select Texture Opacity
Input Texture Scale Y 1.5    (default 1)


Arnold
Step Size  .05
  (default .1)
Enable Deformation Blur (This makes everything a little trippy if the flame is transparent. default not checked)



timesliderplay Play the animation simulation to see changes you have made.



Cache the Simulation
This can create some huge files, caching allows you to look at any frame in the sequence or batch render on multiple computers.

Select the fluid
nCache->Create New Cache->Maya Fluid
     Create a folder for cache, I make a folder in the scenes directory
If you would like this to cache faster:
     Hide everything in the scene, except the fluid and emitters.
     Select the fluid and change Display, Wireframe Display Off   (default Particles)



Render Test Settings
Press Render Settings icon upper right or middle  srender_settings

Under the Arnold Renderer
tab:
Under the Sampling arrow:
     Camera (AA) to 2      (a little grainy, default 3)
     Diffuse to 0      (default 2)
     Specular to 0      (default 2)
     Transmission to 0      (
default
2)
     SSS to 0      (
default
2)
     Volume Indirect to 1      (
default 2)
Under
Filter arrow
    
Width to 1
Under the Ray Depth arrow
     Total to 1      (
default 10)
     Diffuse
to 1     (
default 1)
     Specular
to 0      (
default 1)
     Transmisssion
to 0      (
default 8)
     Volume
to 1     (leaves specks,
default 0)
    
Transparency Depth to 0      (
default
10)




Batch Render
Open a text document with Notepad, type this:

@echo off
set render=C:\"Program Files"\Autodesk\Maya2023\bin\Render.exe
set directory=C:\Users\%USERNAME%\Documents\maya\projects\default\images\folder
set scene_folder=C:\Users\%USERNAME%\Documents\maya\projects\default\scenes
%render% -s 1 -e 100 -x 960 -y 540 -cam persp -rd %directory% -im image_name %scene_folder%\fluid_test4.mb


Save the file as this_batch.bat on your Desktop
Double click the batch file to run it.



Fluids Batch Render BUGs


The batch ignores the cached files and takes a lot of time to calculate a run-up for sequences if the entire animation is not cached starting from frame 0 - the end of the fluid effect, even if your fluid starts later.  This is an unfortunate bug because cache files can be huge.

Another very important thing to do:
Select the fluid and then select the cache node in the Attribute editor
    
Change the Start Frame for the cache from 0 to 1
     This way you will not see black frames at the start of a sequence.

In addition, the first frame of any sequence will also have no fluid rendered, unless you save your scene file with the time slider at 0.

This is the run-up error message:
Warning: line 1: This file contains an uncached fluid; rewind and playback to see correct current state.



Deadline Render Server
It works out best to save the fluid cache files in the same folder as your scene.
Make sure to open the Maya scene file from the local folder and reconnect the cache.


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© 1988-2022 34 years Jennifer Steinkamp