Creating the fluid smoke and flames

In the next steps, you create a 3D fluid object that emits from the surface of the geo_slag polygon object.

To create the 3D fluid container

Switch to the Dynamics menu set.
In the Dynamics menu set, select Fluid Effects > Create 3D Container > .
The Create 3D Container Options window opens.
In the Create 3D Container Options window, select Edit > Reset Settings and ensure the X, Y, and Z resolution values are 10.
Keeping the fluid resolution values set to the default value of 10 ensures that the fluid simulates quickly. Later in the lesson, you increase the resolution values to improve the quality and overall appearance of the effect.
Click Apply and Close.
In the Outliner, rename fluid1 object to fluid_slag_smoke.
To position the container at the top of the slag chute, in the Attribute Editor, click the fluid_slag_smoke tab.
In the Transform Attributes section, set the Translate values to:
- X: -7.0
- Y: 16.
- Z: -1
The Translate values position the fluid container at the top of the slag chute. You can now add the emitter to the fluid container.

To emit fluid from the slag mesh

In the Outliner, Ctrl-click fluid_slag_smoke and geo_slag, then select Fluid Effects > Add/Edit Contents > Emit from Object > from the main menu bar.
In the Emit from Objects Options window that appears, select Edit > Reset Settings, then set the following:
- For the Emitter name, type emitter_slag_smoke.
- In the Basic Emitter Attributes section, set Emitter type to Surface.
Click Apply and Close.
Rewind and play the simulation.
Notice that the fluid emits from the slag mesh, but only while the slag passes through the fluid container. Turning on Auto Resize enables the fluid container to follow the slag mesh as it emits fluid.
In the Outliner select fluid_slag_smoke, then switch to the fluid_slag_smokeShape tab in the Attribute Editor.
In the Auto Resize section, turn on Auto Resize.
Rewind and play the simulation.
Notice that the fluid container now resizes and follows the movements of the slag. When Auto Resize is on, the boundaries (Size and Resolution) of a fluid container dynamically resize as the fluid density increases or decreases. Auto Resize keeps the fluid container relatively small, so it works well with fluid effects that move quickly, such as a missile vapor trail or the rolling smoke of an explosion.

Turning on Auto Resize can increase simulation speed, reduce memory use, creating smaller fluid cache files, and decrease fluid render time.

Notice that the fluid does not look or behave like smoke and flames. To improve the effect you will do the following:
- Reduce the fluid emission rate so that the fluid emits less density and temperature into the container. This helps create the wispy smoke suitable for the effect.
- Adjust the density Dissipation attribute, so that the smoke gradually dissipates after it is emitted. For this effect, the smoke density should dissipate fairly quickly.

Adjusting fluid emission

In this section of the lesson, you set attributes to control how the fluid contents emit into the container. For this effect, you emit Density and Heat into the container. You also add Turbulence, to add swirling motion to the fluid.

For more information about fluid effects, see the Fluid Effects section in the Maya Help.

To adjust the fluid emission

In the Attribute Editor, click the emitter_slag_smoke tab.
If you do not have the fluid selected, you access the fluid emitter object through the Outliner by expanding geo_slag and selecting emitter_slag_smoke1.
In the Basic Emitter Attributes section, do the following:
- Turn on Use Distance.
- Set Min Distance to 0.06.
- Set Max Distance to 0.44.
These values define the minimum and maximum distance that fluid is emitted from the mesh surface.
In the Fluid Attributes section, set the rate of Density and Heat emission in the fluid container as follows:
- Density/Voxel/Sec: 0.28
- Heat/Voxel/Sec: 0.4
In the Fluid Emission Turbulence section, set Turbulence to 6.3.
This adds turbulence to the Density and Heat as they emit into the container, which generates additional movement in the fluid.
Rewind and play the simulation.
Notice that the fluid emission is less dense, but there is little motion in the fluid. In the next section, you set fluidShape node attributes to add detail and movement to the smoke.

Setting fluidShape node attributes

Next, you will adjust the Buoyancy and Dissipation attributes to define the behavior of the Density and Heat in the fluid container after emission.

To set the fluidShape node attributes

In the Attribute Editor, click the fluid_slag_smokeShape tab.
In the Contents Method section, set Temperature to Dynamic Grid.
In the Contents Details section, click Density, and set the following:
- Buoyancy: 0.31
  This determines the tendency of the Density to rise in the container, similar to the way a lighter-than-air gas rises in the atmosphere. Decreasing Buoyancy will keep the fluid from rising and increasing in size.
- Dissipation: 3.0
  This determines how quickly Density is removed from the container similar to evaporation. Increasing Dissipation causes the Density to dissipate quicker into the air.
In the Temperature section, set the following:
- Temperature Scale: 0.5
- Buoyancy: 30.0
- Dissipation: 3.0
- Diffusion: 0.0
- Turbulence: 10
  Setting these attributes adds movement to the Heat in the container, but they do not affect Density.
Rewind and play the simulation.
The fluid appears more subtle in the scene, but it is difficult to see how the Density and Temperature attribute adjustments have affected its behavior. Before setting the fluid Shading attributes to color the fluid, you can increase the fluid resolution to make the fluid's behavior easier to see. Be aware that increasing fluid resolution increased simulation time.
In the Container Properties section, set the Base Resolution to 30.
Rewind and play the simulation.
The fluid behavior is now much easier to assess.

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