Maya Fluid Effects Playing Dynamic Fluid Simulations
Setting the initial state of a fluid

The state of a fluid is the collection of its grid property values (the values in the Density, Velocity, Temperature, Fuel, Color, and Texture Coordinate grids). The state of an uncached dynamic fluid in any frame other than the first is based on its state in the prior frame. Maya calculates dynamic fluid effects sequentially starting at the first frame.

The grid property values defined in a fluid container at the first frame of a simulation describe the fluid's initial state. You can play a simulation up to any frame, then use the current state at that frame as the initial state for the fluid.

For example, suppose you have an empty fluid container but you want the scene to start with fluid already in it. You could add a fluid emitter to the container, play and stop the simulation at a frame with the desired emitted fluid, and then set the emitted fluid values as the initial state. When you go to the start frame of the simulation and play, the fluid will start with the grid property values that are stored in its initial state.

If the current time changes to any frame before the start frame for the fluid simulation, Maya reads the initial state. For example, if you set your initial state when the fluid start frame is 1, and then change the fluid start frame to frame 10, Maya reads the initial state at frame 1, but does not start the simulation until frame 10. If there is no initial state, Maya clears the contents of the container.

When you paint fluid property values into a grid, you must set the initial state of the fluid. Otherwise, when you play the simulation, the initial values you paint will be lost when you go back to the first frame. For information on painting fluid values, see Painting fluid properties into grids.

To set a fluid's current dynamic grid property values as the initial state:

1. Add the property values to the fluid container.
See Adding properties to fluid containers.
2. Play and stop the simulation at the frame with the fluid property values you want to set (save) as the initial state, if necessary.
3. Select the fluid container.
4. Select Fluid Effects > Set Initial State.

Maya creates a hidden initial state cache node in the Temp directory. When you save the scene, Maya creates an initial state cache node and a disk cache file and stores the file in the project's data directory.

The initial state cache file is named filename_fluidShape.mcfi.
The node is named initialState_fluidShape.

To delete the initial state of a fluid:

1. Select the fluid container.
2. Select Fluid Effects > Clear Initial State.

Maya deletes the initialState_fluidShape node but does not delete the initial state cache file (in case it is being used by another scene). When you go to the start of the simulation, the contents of the container will be empty.

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