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This page provides information on the Dynamics rollout for liqui= ds.
This rollout controls the fluid's motion parameters, which affect the fl= uid=E2=80=99s behavior when simulating.
UI Path: ||Select Liquid Simulator object|| >= Modify panel > Dynamics rollout
Expand =E2=80=93 Opens a floating dialog that cont= ains the selected rollout and automatically folds the command panel rollout= .
Re-Center =E2=80=93 Resets the position of the floating= rollout.
? =E2=80=93 Opens up the help documents for t= he Liquid Dynamics.
Simulate Air Effects | simair =E2=80=93 When e= nabled, 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 Simula= tor. 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, i= t will not affect the liquid back. So for example you can use Simul= ate Air Effects when realistic mist is needed in waterfall setups,= or stormy ocean scenes. The air simulation can dramatically increase the q= uality of splash and mist effects.
The air effects stop affecting particles = once they exit the Simulator thus altering the particle speed and direction= around the Simulator's walls.
Motion Inertia | ext_wind =E2=80=93 When enabled, moving the Simulator's object over a series of fr= ames 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 t= he grid relatively small, as opposed to creating a large grid that covers t= he entire path of the moving object. Motion Inertia can be= used for moving ground and water vehicles, torches, fireballs, rockets, et= c. When this option is used together with the Initial Fill Up option and Open Container Wall conditions, a simulatio= n of moving an object over a sea surface can be done. For more informat= ion, see the Motion Inert= ia example below.
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 t= o the direction of movement, with Motion Inertia enabled, = please ensure that the Scene Scale is reasonable consideri= ng the type of effect being simulated. Other possible solutions in case twe= aking the scale is not possible are to either increase the Steps Pe= r Frame, or to reduce the Cell Size of the Simula= tor.
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 =E2=80=93 Phoenix Gravity makes the liquids fall down and makes fire rise up.&= nbsp;The Gravity option is a multiplier, so usin= g the default 1.0 will make it behave like real world gravity, setting it t= o 0.0 will disable its effect completely, and you can also use negative val= ues, which will inverse the gravity effect.
Initial Fill Up | ini= tfill, flevel =E2=80=93 When enabled, the container= is filled up with liquid when the simulation starts. This option dete= rmines the fill-up level, measured in % of the vertical Z size of the Grid.= For liquid simulations using Confine Geometry, you c= an enable Cle= ar Inside on the geometry and liquid will not be created at simula= tion startup in the voxels inside the geometry.
The liquid created through the Initial Fill Up option will be initialized with t= he values set for the Default RGB and = Default Viscosity parameters below.
Fill Up For Ocean | =
oceanfill =E2=80=93 Changes the Open
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, ev=
en if they don't contain any Liquid particles. If you don't want this effec=
t, enable Clear Inside from the&nbs=
p;Chaos Phoenix Pe=
r-Node Properties of the Solid geometry. See the&nbs=
p;Fill Up For Ocean a=
nd Clear Inside example below.
All Simulator walls must be set = to Open from the Grid rollout = for Fill Up For Ocean to take effect.<= /p>
= Steps Per Frame | spf =E2=80= =93 Determines how many calculations the simulation will perform between tw= o consecutive frames of the timeline. For more information, see the&nbs= p;Steps Per Frame = example below.
Steps Per Frame (SPF) is one of the most important parameters of the simulator, with a signifi=
cant impact on quality and performance. To understand how to use it, keep i=
n 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, wi=
thout first simulating all of the frames that come before it, one by one.=
p> The simulation produces good results if each step introduces s=
mall 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 t=
o introduce intermediate steps, until the object's movement becomes small e=
nough that it happens smoothly across all steps for that frame. The&n=
bsp;SPF parameter creates these steps within each fra=
me. 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 inter=
mediate step, i.e. each second step is exported to the cache file, while in=
termediate steps are simply calculated, but not exported.
Increasing the Steps Per Fra= me (SPF) also comes with significant trade-o= ffs to performance and detail.
A higher SPF decreases perform= ance in a linear way. For example, if you increase the <= strong>SPF twice, your simulation will take twice as long. Ho= wever, quality does not have a linear relation to SPF= .
For maximum detail, it is best to use the lowest possible S= PF that simulates without any of the issues described in the = tip box below, since each additional step kills fine details. For more info= rmation, please refer to the Phoenix Explained docs.
Signs that the Steps Per Fra= me (SPF) needs to be increased include:
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 t= he objects in the scene are moving very fast). In such cases, you should us= e a higher SPF.
Time Scale | timescale =E2=80= =93 Specifies a time multiplier that can be used for slow motion effects.&n= bsp;For more information, see the = Time = Scale example below.
In order to achieve the same simulation l= ook when changing the Time Scale, the Steps P= er 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 a= nimated 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 <= strong>Default RGB is also used to color the fluid generated = by Initial Fill Up, or by Initial L= iquid Fill from the Chaos Phoenix Per-Node Properties of a g= eometry - both of these options create liquid only at the start of the simu= lation. During simulation, more colors can be mixed into the sim by us= ing a Phoenix Liquid Source= with RGB enabled, or the color of exis= ting fluid can be changed over time by using a Phoenix Mapper. If a Phoenix Liquid Source does not have R= GB enabled, it also emits using the Default RGB<= /strong> value.
The RGB Grid Channel
RGB Diffusion | rgbdiff =E2=80=
=93 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 wh=
en 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 i=
n contact, thus achieving uniform color in the resulting mixed liquid. =
;For more information, see the
Default Viscosity | lqvis= c =E2=80=93 Determines the default viscosity of the liquid. Visco= sity means how thick the liquid is. Liquids such as honey, syrup, or even t= hick mud and lava need to be simulated with high viscosity. On the other ha= nd, liquid such as water, beer, coffee or milk are very thin and show have = zero or very low viscosity. The Default Viscosity&nbs= p;value is used when no viscosity information for the emitted liquid is pro= vided to the Simulator by the Source. Also note that the effect of the visc= osity works more strongly with more Steps Per Frame, and a= lso when the grid resolution is lower. Increasing the grid resolution or re= ducing the Steps Per Frame can make viscous liquid thinner= . For more information, see the Viscosity example below.
Viscosity Diffusion | viscdiff - Phoenix supports sourcing of fluids with different vis= cosity (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 th= ickness.
Non-Newtonian | nonnewt = =E2=80=93 Modifies the viscosity with respect to the liquid's velocity to o= vercome the conflict between viscosity and wetting, where a high viscosity = of real liquids prevents wetting. Non-Newtonian liquids are liquids that be= have differently at different velocities. This parameter accounts for this = behavior by decreasing the viscosity in areas where the liquid is movi= ng 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 o= f 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 with= out roughness and holes. If the viscosity is high enough, the chocolate mig= ht look right during the pouring and settling motions but won't settle in t= o form a smooth thin layer over the cookie. This parameter decreases the vi= scosity where the liquid is moving slowly (over the surface of the cookie) = while keeping the faster-moving stream tight and highly viscous. F= or more information, see the Non-Newtonian example below.
Droplets Surfing | dsurf =E2=80= =93 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 Surfin= g example below.
The following video provides examples of = moving containers with Motion In= ertia enabled to show the differences between values of = 0, 0.5, and 1.0.
Software used: Phoenix 4.30.00 Official Re= lease
This example shows the Liquid voxels, wit= h a submerged Solid ellipsoi= d. There are never FLIP particles inside it, but disabling Clear Inside will fill it with Liquid voxels= so the liquid mesh can intersect it.
=
The following video provides examples to = show the differences of Steps Per Frame values at 1, 5, and 15.
Software used: Phoenix 4.30.01 Night= ly (02 Oct 2020)
Here is the difference between Steps Per = Frame values of 1 and 10 when a Source emits liquid with high velocity.
=
<= /span>
The following video provides examples to = show the differences of Time Scale with values o= f 0.3, 1.0, and 2.0.
Software used: Phoenix 4.30.01 Night= ly (02 Oct 2020)
The following video provides examples to = show the differences of RGB Diffusion with value= s of 0.0, 0.5, and 1.0.
Software used: Phoenix 4.30.01 Nightly (02= Oct 2020)
The following video provides examples to = show the differences of Default Viscosity with v= alues of 0.0, 0.5, and 1.0.
= span>Software used: Phoenix 4.30.01 Night= ly (02 Oct 2020)
The following video provides examples to = show the differences of Non-Newtonian with value= s of 0, 0.1, and 1.0.
Software used: Phoenix 4.30.01 Night= ly (02 Oct 2020)
The following video provides examples to = show the differences of Droplets Surfing with va= lues of 0.0, 0.5, and 1.0.
Software used: Phoenix 4.30.00 Offic= ial Release
Strength | lqsurft =E2=80=93 Controls the= force produced by the curvature of the liquid surface. This parameter= plays an important role in small-scale liquid simulations because an accur= ate simulation of surface tension indicates the small scale to the audience= . Lower Strength values will cause the liquid to= easily break apart into individual liquid particles, while higher values w= ill make it harder for the liquid surface to split and will hold the liquid= particles together. With high Strength, when an exte= rnal force affects the liquid, it would either stretch out into tendrils, o= r split into large droplets. Which of these two effects will occur is contr= olled by the Droplet Formation parameter. <= em>For more information, see the Surface Tension example below.
Droplet Formation | lqstdropbreak&nb= sp;=E2=80=93 Balances between the liquid forming tendrils or droplets. When= set to a value of 0, the liquid forms long tendrils. When set to a value o= f 1, the liquid breaks up into separate droplets, the size of which can be = controlled by the Droplet Radius parameter. = ;For more information, see the Droplet Formation example below.
Droplet Radius | lqstdroprad = =E2=80=93 Controls the radius of the droplets formed by the Dr= oplet Formation parameter, in voxels. T= his means that increasing the resolution of the Simulator will reduce the o= verall size of the droplets in your simulation.
Increasing the
The following video provides examples to = show the differences of Surface Tension with val= ues of 0.0, 0.07, 0.28 and = em>Droplet Formation with value of <= em>0.0.
Software used: Phoenix 4.30.01 Night= ly (02 Oct 2020)
The following video provides examples to = show the differences of Droplet Formation with values of&n= bsp;0.0, 0.5, 1.0 and Sur= face Tension with value of&n= bsp;0.1.
Software used: Phoenix 4.30.01 Night= ly (02 Oct 2020)
The simulation of wetting can be used in = rendering for blending wet and dry materials, depending on which parts of a= geometry have been in contact with the simulated liquid. Wetting can also = change the behavior of a simulated viscous liquid and make it stick to geom= etries.
The wetting simulation produces a particle system called
Wh= en used with a Blend Material, the Particle Texture acts as a mask to blend= between two materials, for example, a wet material and a dry surface mater= ial. This way, geometry covered by WetMap particles can ap= pear wet, and the rest of the geometry can appear dry.
Wetting | wetting =E2=80=93 Enables the wettin= g simulation. The liquid will leave a trail over the surfaces of bodies it = interacts with.
Consumed Liquid | lq2wet =E2=80=93 Controls ho= w many liquid particles disappear when creating a single WetMap particle. The main purpose of this parameter is to prevent long visib= le tracks from being left by a single liquid particle. For more informa= tion, see the Consumed Liquid example below.
Drying Time (sec) | drying =E2= =80=93 Controls the drying speed in seconds. The WetMap pa= rticles are born with a size of 1, and if they are in an air environment, t= he size decreases until it reaches zero after the time specified with this = parameter.
Sticky Liquid | wetdyn =E2=80= =93 This option produces a connecting force between the WetMap particles at the geometry surface and nearby liquid particles.= For more information, see the Sticky Liquid= a> example below.
Geometry transforming or deforming at a h= igh velocity may cause some or all of the Wetting particle= s stuck to it to disappear. To resolve this, dial up the Steps Per Frame parameter from the Dynamics tab of the Simulator.
The following video provides examples to = show the differences of Consumed Liquid values of 0, 0.1, and 0.3.
Software used: Phoenix 4.30.01 Night= ly (02 Oct 2020)
The following video provides examples to = show the differences of Sticky Liquid values of&= nbsp;0, 0.5, and 1, when the V= iscosity is set to 0.
Software used: Phoenix 4.41.02 Nightly (24= Jun 2021)
The following video provides examples to =
show the differences of Viscosity values of 0.1=
em>, 0.5, and 1.0 and Sticky Liquid
Software used: Phoenix 4.41.02 Nightly (24= Jun 2021)
The following video provides examples to =
show the differences of Surface Force values of 5=
0, 500, and 1000, Sticky Liquid
Software used: Phoenix 4.30.01 Nightly (02= Oct 2020)
Note that interaction between Active B= odies and the Phoenix Fire/Smoke Simulator is not supported.
Chaos Phoenix can make a ship, or ice cubes, or other geometry float in = water using the Active Bodies feature, which introduces Rigid Body Dynamics= for specified Active Body objects. Phoenix can even simulate waves that ca= n carry Active Body objects around, or wash them away.
To use Active Bodies, you=E2=80=99ll need to create an Active Body Solver component, and specif= y the scene geometry which will partake in the Active Bodies simulation. Th= en, in the simulator=E2=80=99s Dynamics rollout, enable the Active = Bodies parameter, and specify the Active Body Solver node.
You can then set the density and other Active Body properties in the Phoenix Per-Node Prop= erties menu for each Active Body object.
The Active Bodies simulation currently su= pports interaction between scene geometry and the Phoenix Liquid Simulator.= When an object is selected as an Active Body, the simulation both in= fluences and is influenced by the Active Body's movement.
Fo= r more information on Active Bodies, please check out the Active Body Solver and the Active Bodies Setup Guide.
Active Bodies | use_activeBodySolverNode<= /em> =E2=80=93 Enables the simulation of Active Bodies.
Active Body Solver | activeBodySolverNode= =E2=80=93 Specifies the Active Body Solver node holding the objects to b= e affected by the Phoenix Simulation.
The main purpose of the Texture UVW= feature is to provide dynamic UVW coordinates for texture mapping that fol= low the simulation. If such simulated texture coordinates are not present f= or mapping, textures assigned to your simulation will appear static, with t= he simulated content moving through the image. This undesired behavior is o= ften referred to as 'texture swimming'.
UVW coordinates are ge= nerated by simulating an additional Texture UVW Grid Channel which = has to be enabled under the Outp= ut rollout for the settings below to have any effect= strong>.
The custom UVW texture coordinates can be used for advanced = render-time effects, such as recoloring of mixing fluids, modifying the opa= city or fire intensity with a naturally moving texture, or natural movement= of displacement over fire/smoke and liquid surfaces. For more information,= please check the Text= ure mapping, moving textures with fire/smoke/liquid, and TexUVW page.= p>
Interpolation | texuvw_interpol_influence= =E2=80=93 Blends between the UVW coordinates of the liquid parti= cle at time of birth and its UVW coordinates at the current position in the= Simulator. When set to 0, no interpolation will be performed - as a conseq= uence, textures assigned to the fluid mesh will be stretched as the simulat= ion progresses. This is best used for simulations of melting objects. When = set to 1, the UVW coordinates of the fluid mesh will be updated with a freq= uency based on the Interpol.Step parameter - thi= s will essentially re-project the UVWs to avoid stretching but cause the te= xtures assigned to the fluid to 'pop' as the re-projection is applied. If y= ou intend to apply e.g. a displacement map to a flowing river, set this par= ameter to a value between 0.1 and 0.3 - this will suppress both the effects= of stretching and popping. See the Interpolation example below.
Interpol. Step | texuvw_interpol_step =E2=80=93 Specifies the update frequency for the UVW coordinates. Wh= en set to 1, the UVWs are updated on every frame, taking into account the&n= bsp;Interpolation parameter. See the Interpolation Step example belo= w.
The following video provides exampl=
es to show the differences of Interpolation
Software used: Phoenix 4.30.01 Night= ly (02 Oct 2020)
The following video provides examples to = show the differences of Interpolation Step value= s of 1, 3, and 6, and an = Interpolation with value of 1.0.
Software used: Phoenix 4.30.01 Night= ly (02 Oct 2020)