Expand – Opens a floating dialog that contains the selected rollout and automatically folds the command panel rollout.
Re-Center – Resets the position of the floating rollout.
? – Opens up the help documents for the Liquid Dynamics.
Simulate Air Effects | simair – When enabled, turns on the built-in air simulator for the areas in the simulation grid which are not full of liquid. The air velocity can be affected by the liquid movement, by Sources, or by fast moving obstacles inside the Simulator. In turn, the air velocity will affect and carry splash, mist, and foam particles. Note, however, that no matter how strong the air velocity is, it will not affect the liquid back. So for example you can use Simulate Air Effects when realistic mist is needed in waterfall setups, or stormy ocean scenes. The air simulation can dramatically increase the quality of splash and mist effects.
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The air effects stop affecting particles once they exit the Simulator thus altering the particle speed and direction around the Simulator's walls.
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InertialForces
InertialForces
Motion Inertia| ext_wind – When enabled, moving the Simulator's object over a series of frames causes inertial forces in the opposite direction of the movement. This allows you to link the Simulator to a moving object and keep the size of the grid relatively small, as opposed to creating a large grid that covers the entire path of the moving object. Motion Inertia can be used for moving ground and water vehicles, torches, fireballs, rockets, etc. When this option is used together with the Initial Fill Up option and Open Container Wall conditions, a simulation of moving an object over a sea surface can be done. For more information, see the Motion Inertia example below.
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When running liquid simulations with the Initial Fill Up option and Open Container Wall conditions, the surface of the generated liquid should remain smooth. If you encounter artifacts in the form of horizontal lines perpendicular to the direction of movement, with Motion Inertia enabled, please ensure that the Scene Scale is reasonable considering the type of effect being simulated. Other possible solutions in case tweaking the scale is not possible are to either increase the Steps Per Frame, or to reduce the Cell Size of the Simulator.
Liquid artifacts usually appear when the liquid particles move a great distance between frames. Increasing the Scene Scale or the Steps Per Frame allows them to stabilize, which in turn keeps the surface smooth.
Gravity | grav, gmul – Phoenix Gravity makes the liquids fall down and makes fire rise up. The Gravity option is a multiplier, so using the default 1.0 will make it behave like real world gravity, setting it to 0.0 will disable its effect completely, and you can also use negative values, which will inverse the gravity effect.
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InitialFillUp
InitialFillUp
Initial Fill Up | initfill, flevel – When enabled, the container is filled up with liquid when the simulation starts. This option determines the fill-up level, measured in % of the vertical Z size of the Grid. For liquid simulations using Confine Geometry, you can enable Clear Inside on the geometry and liquid will not be created at simulation startup in the voxels inside the geometry.
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The liquid created through the Initial Fill Up option will be initialized with the values set for the Default RGB and Default Viscosity parameters below.
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FillupForOcean
FillupForOcean
Fill Up For Ocean| oceanfill – Changes the Open Container Walls of the Simulator so they would act like there is an infinite liquid volume beyond them. Pressure will be created at the Simulator's walls in order to support the liquid, and if the surface of a wall below the Initial Fill Up level, or the bottom, gets cleared from liquid during simulation, new incoming liquid would be created. You can also animate the Simulator's movement or link it to a moving geometry, and it would act like a moving window over an ocean that stays in place. This way you can simulate moving ships or boats that carry their Liquid Simulator along with them as they sail into an ocean, so you don't need to create one huge long Simulator along their entire path.
In order to eliminate air pockets between Solid geometry and the liquid mesh, this option will automatically set all Solid voxels below the Initial Fill Up level to contain Liquid amount of 1, even if they don't contain any Liquid particles. If you don't want this effect, enable Clear Inside from the Chaos Phoenix Per-Node Properties of the Solid geometry. See the Fill Up For Ocean and Clear Insideexample below.
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All Simulator walls must be set to Open from the Grid rollout for Fill Up For Ocean to take effect.
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SPF
SPF
Steps Per Frame | spf – Determines how many calculations the simulation will perform between two consecutive frames of the timeline. For more information, see the Steps Per Frame example below.
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Steps Per Frame (SPF) is one of the most important parameters of the simulator, with a significant impact on quality and performance. To understand how to use it, keep in mind that the simulation is a sequential process and happens step by step. You cannot take a shortcut to simulate the last frame of a simulation, without first simulating all of the frames that come before it, one by one.
The simulation produces good results if each step introduces small changes to the sim.
For example, if you have an object that is hitting a liquid surface with a high speed, the result will not be very good if at the first step, the object is far away from the water, and at the second step, the object is already deep under the water. You need to introduce intermediate steps, until the object's movement becomes small enough that it happens smoothly across all steps for that frame.
The SPF parameter creates these steps within each frame. A value of 1 means that there are no intermediate steps, and each step is exported into the cache file. A value of 2 means that there is one intermediate step, i.e. each second step is exported to the cache file, while intermediate steps are simply calculated, but not exported.
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Increasing the Steps Per Frame (SPF) alsocomes with significant trade-offs to performance and detail.
A higher SPF decreases performance in a linear way. For example, if you increase the SPF twice, your simulation will take twice as long. However, quality does not have a linear relation to SPF.
For maximum detail, it is best to use the lowest possible SPF that simulates without any of the issues described in the tip box below, since each additional step kills fine details. For more information, please refer to the Phoenix Explained docs.
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Signs that the Steps Per Frame (SPF) needs to be increased include:
Liquid simulations that have too many single liquid particles.
Liquid simulations that appear torn and chaotic.
Liquid simulations of streams that have visible steps or other periodical artifacts.
Fire/Smoke simulations with artifacts that produce a grainy appearance.
More often than not, these issues will be caused by the simulation moving too quickly (e.g. the emission from the source is very strong, or the objects in the scene are moving very fast). In such cases, you should use a higher SPF.
Time Scale | timescale – Specifies a time multiplier that can be used for slow motion effects. For more information, see the Time Scale example below.
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In order to achieve the same simulation look when changing the Time Scale, the Steps Per Frame value must be changed accordingly. For example, when decreasing the Time Scale from 1.0 to 0.5, Steps Per Frame must be decreased from 4 to 2. All animated objects in the scene (moving objects and sources) must be adjusted as well.
Time Scale different than 1 will affect the Buildup Time of Particle/Voxel Tuners and the Phoenix Mapper. In order to get predictable results you will have to adjust the buildup time using this formula: Time Scale * Time in frames / Frames per second
Default RGB | lq_default_rgb - The Simulator is filled with this RGB color at simulation start. The Default RGB is also used to color the fluid generated by Initial Fill Up, or by Initial Liquid Fill from the Chaos Phoenix Per-Node Properties of a geometry - both of these options create liquid only at the start of the simulation. During simulation, more colors can be mixed into the sim by using a Phoenix Liquid Source with RGB enabled, or the color of existing fluid can be changed over time by using a Phoenix Mapper. If a Phoenix Liquid Source does not have RGB enabled, it also emits using the Default RGB value.
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The RGB Grid Channel or RGB Particle Channel has to be enabled in the Output Rollout for this parameter to take effect.
RGB Diffusion | rgbdiff – Control how quickly the colors of particles are mixed over time during the simulation. When it's set to 0, each FLIP liquid particle carries its own color, and the color of each individual particle does not change when liquids are mixed. This means that if red and green liquids are mixed, a dotted red-green liquid will be produced instead of a yellow liquid. This parameter allows the colors of particles to change when the particles are in contact, thus achieving uniform color in the resulting mixed liquid. For more information, see theRGB Diffusion example below.
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Default Viscosity | lqvisc – Determines the default viscosity of the liquid. Viscosity means how thick the liquid is. Liquids such as honey, syrup, or even thick mud and lava need to be simulated with high viscosity. On the other hand, liquid such as water, beer, coffee or milk are very thin and show have zero or very low viscosity. The Default Viscosity value is used when no viscosity information for the emitted liquid is provided to the Simulator by the Source. Also note that the effect of the viscosity works more strongly with more Steps Per Frame, and also when the grid resolution is lower. Increasing the grid resolution or reducing the Steps Per Frame can make viscous liquid thinner. For more information, see the Viscosity example below.
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All FLIP liquid particles are set to this viscosity value at simulation start. You should use higher viscosity for thicker liquids such as chocolate, cream, etc.
The Default Viscosity is also used for the fluid generated by Initial Fill Up, or by Initial Liquid Fill from the Phoenix Per-Node Properties of a geometry - both of these options create liquid only at the start of the simulation.
If a Phoenix Liquid Source does not have Viscosity enabled, it emits using the Default Viscosity value.
During simulation, liquids of variable viscosity can be mixed into the sim by using a Phoenix Liquid Source with Viscosity enabled.
The Viscosity Grid Channel export has to be enabled in the Output Rollout for variable viscosity simulations to work.
The viscosity of existing liquid can be changed over time by using a Phoenix Mapper in order to achieve melting or solidifying of fluids.
You can shade the liquid mesh or particles using the fluid's viscosity with the help of the Phoenix Grid Texture or Particle Texture.
It's important to note that using viscosity does not automatically make the liquid sticky. For example, molten glass is viscous, but not sticky at all. Stickiness can be enabled explicitly from the Wetting parameters section. If Stickiness is not enabled, even the most viscous fluid would slide from the surfaces of geometries or from the jammed walls of the Simulator.
Viscosity Diffusion | viscdiff - Phoenix supports sourcing of fluids with different viscosity (thickness) values. This parameter specifies how quickly they blend together. A low value will preserve the distinct viscosities, while a high value will allow them to mix together and produce a fluid with a uniform thickness.
Non-Newtonian | nonnewt – Modifies the viscosity with respect to the liquid's velocity to overcome the conflict between viscosity and wetting, where a high viscosity of real liquids prevents wetting. Non-Newtonian liquids are liquids that behave differently at different velocities. This parameter accounts for this behavior by decreasing the viscosity in areas where the liquid is moving slowly and retains a higher viscosity where the liquid is moving quickly. For example, to cover a cookie with liquid chocolate, high viscosity is needed in the pouring portion of the motion to obtain the curly shape of the chocolate as it lands on the cookie and begins to settle down. On the other hand, a smooth chocolate is needed to settle in over the cookie without roughness and holes. If the viscosity is high enough, the chocolate might look right during the pouring and settling motions but won't settle in to form a smooth thin layer over the cookie. This parameter decreases the viscosity where the liquid is moving slowly (over the surface of the cookie) while keeping the faster-moving stream tight and highly viscous. For more information, see the Non-Newtonian example below.
Droplets Surfing | dsurf – This parameter affects the liquid and the splash particles, controlling how long a particle hovers on the surface before it merges with the liquid. The parameter is used mostly in ocean/wave simulations. For more information, see the Droplets Surfing example below.
