To simulate flow for a fluid property, the Contents Method for that property must be set to Dynamic Grid and Velocity cannot be Off. During simulation, the values in the container are solved using the Navier-Stokes fluid dynamics equations (solvers) and replaced with the new values to create the fluid motion. Use the attributes in this section to define the information used by the solvers.
The Gravity setting is a built-in gravitational constant that simulates the gravitational attraction of the mass of the world in which the simulation is occurring. Negative values cause a downward pull (relative to the world coordinate system).
If Gravity is zero, DensityBuoyancy and TemperatureBuoyancy have no effect
Viscosity represents the resistance of the fluid to flow, or how thick, and non-liquid the material is. When this value is high, the fluid flows like tar. When this value is small, the fluid flows more like water.
(When Viscosity is 1, the material Reynolds Number is 0; when it is 0, the Reynolds Number is 10000. The Reynolds Number is a parameter used in solving the fluid dynamics equations that is proportional to the viscosity of the fluid.)
Defines internal friction used in Velocity solving.
Defines the amount the Velocity solution is damped towards zero at each time step. At a value of 1, the flow is totally suppressed. Small amounts of damping can be useful when boundaries are open to keep strong winds from building up and leading to instability.
Select one of the following options:
No solver is used.
A Navier-Stokes solver is used (best for fluids, air, and other situations where flow swirls around but doesn’t expand outward or compress inward)
A wave propagation simulator is used (best for up-and-down, back-and-forth motion found in waves).
This option may reduce diffusion of density, velocity and other attributes during a simulation. For example, it may make fluid simulations appear much more detailed without increasing resolution, and allow the simulation of rolling vortices. Using High Detail Solve is ideal for creating effects such as explosions, rolling clouds and billowing smoke.
Simulations run faster, but there is a lot of diffusion of both density and velocity as the simulation progresses.
Some artifacts that appear when using High Detail Solve can be removed using Density or TemperatureTension.
Applies the additional solve steps to all grids except for velocity, requiring simulation computation time that is not much more than when High Detail Solve is Off.
Only velocity grid values have the additional solve steps applied. This option may avoid some artifacts that can result from high detail on the density grid. (Use the HermiteGrid Interpolation option—while it is slower, it can yield high-quality results.)
Applies the additional solve steps first when computing the velocity, and also when applying the velocity to the rest of the grids. There is much more detail in the flow, resulting in a simulation that is significantly more realistic. Since propagating velocity is much more computationally intensive than propagating scalar grid values like density, using this option doubles the simulation computation time.
Specifies the number of times the solver performs calculations per frame. Substeps are useful for improving the stability and simulation results of fast-moving fluids, fluids with high density grids, and when the High Detail Solve is used.
Increasing the Solver Quality increases the number of steps used by the solver to compute the incompressibility of the fluid flow. This calculation, called the Poisson solve, is generally the most computation intensive part of the solve.
Lowering Solver Quality results in less detailed simulations with more diffusion. However, you can allow for some compression of the fluid by lowering Solver Quality, particularly when High Detail Solve is off and Forward Advection is on. Adding compression to a fluid is useful when using Self Attraction and Gradient Force in your effects. See Self Attraction and Repulsion.
Select which interpolation algorithm to use to retrieve values from points within a voxel grid.
Interpolate the values linearly. This is the faster of the two methods.
Use a hermite curve to interpolate the fluid. This method causes less diffusion than linear, but makes the simulation run several times more slowly, especially when the fluid is colliding with geometry. Use hermite if you want Friction to be computed by the solver at the boundaries. (Use this option with the Velocity OnlyHigh Detail Solve method—while it is slower, it can yield high-quality results. Do not use this option with the All Grids Except Velocity or All Grids options.)
When Forward Advection is on, Density, Temperature, and Fuel grids are solved using a mass conserving forward propagation technique that pushes density forward through the grid. Velocity grids are not calculated using Forward Advection.
The default solve method uses a backwards propagation technique that pulls density into voxels from surrounding voxels.
Fluid effects solved using Forward Advection can produce fewer artifacts when High Detail Solve is used and results in less density diffusion than the default solve method. Forward Advection can also resolve instances where density remains static in voxels.
The default solve method (Forward Advection turned off) relies on the incompressibility of the fluid flow and diffuses if Solver Quality is set to a low value. When Forward Advection is on, the fluid does not have this issue, making it useful for simulations that have compression effects.
Sets the frame after which the fluid simulation will start. The default is 1.0. Nothing will play back for this object prior to this frame. You could use this attribute to delay the effect of a field on a fluid until the frame of your choice.
If you change the Time units setting (Windows > Settings/Preferences > Preferences), you must set the Start Frame to the correct initial value so that Maya computes the start time again.
Scales the time step used in emission and solving.
Turn this option on to turn off solving during interactive playback. If there is a fluids cache present, Maya plays back the simulation from the cache.
Turn this option on to conserve mass when updating the Density values during solving.
Turn this option off to disable the collision of fluid with collision geometry in the container.
Turn this option to off to ignore all connected fluid emitters during simulation.
Turn this option to off to ignore all connected external fields during simulation.
When on, fluid emission is computed each substep rather than once per step. Turning on Emit In Substeps is useful for effects that have high emission speeds such as in an explosion.