Domain Whitewater Settings
This page documents the domain settings for the FLIP Fluid Whitewater panel. All parameters in this panel must be set before baking for changes in the simulation to take effect.
Video Guides: Part A: Mastering Foam | Part B: Mastering Bubbles/Spray/Dust
- Parameters
| Enable Whitewater Simulation | Enable the whitewater foam/bubble/spray particle solver |
| Settings View Mode | How to display the settings in the panel UI. Basic Display only the basic and most important whitewater settings. Most simulation scenarios will only need to adjust these parameters. Advanced Display all parameters for full customization of whitewater behaviour. Settings in this documentation will denote an advanced setting with an (A) symbol next to the parameter name. |
| Highlight Advanced Settings | Enabling this option will highlight advanced settings with a red color in the UI. This setting is only available if Settings View Mode is set to Advanced. Settings in this documentation will denote an advanced setting with an (A) symbol next to the parameter name. |
| Foam | Enable solving for foam particles. Foam particles form a layer on the fluid surface and are advected with the fluid velocity. If disabled, any particles that enter the foam layer will be destroyed. |
| Bubble | Enable solving for bubble particles. Bubble particles below the foam layer are advected with the fluid velocity and float towards the foam layer against gravity. If disabled, any particles that move below the foam layer will be destroyed. TIP: Bubble particles are a large contributor to the foam layer and disabling may severely limit the amount of generated foam |
| Spray | Enable solving for spray particles. Spray particles above the foam layer are simulated ballistically with gravity. If disabled, any particles that move above the foam layer will be destroyed. |
| Dust | Enable solving for dust particles. Dust particles are generated near obstacle surfaces and are advected with the fluid velocity while sinking towards the ground. Unlike foam/bubble/spray particles that are part of a lifecycle, dust particles will remain dust particles for the entire simulation and do not transform into other particles. |
| Enable Whitewater Emission | Allow whitewater emitters to generate new foam/bubble/spray particles |
| Emitter Generation Rate (A) | Amount of whitewater emitters that the solver may generate. Emitters are generated within the fluid at wavecrests and in areas of high turbulence. |
| Wavecrest Emission Rate | Maximum number of whitewater particles that a wavecrest emitter may generate per simulation second. |
| Turbulence Emission Rate | Maximum number of whitewater particles that a turbulence emitter may generate per simulation second. |
| Dust Emission Rate | Maximum number of whitewater dust particles that a dust emitter may generate per simulation second. |
| Min Curvature (A) | When the wavecrest curvature around an emitter is less than this value, the emitter will generate no whitewater particles. |
| Max Curvature (A) | When the wavecrest curvature around an emitter lies in the range of Min Wavecrest Curvature up to this value, proportionally increase the rate of generated whitewater particles up to the Wavecrest Emission Rate. |
| Min Turbulence (A) | When the fluid turbulence around an emitter is less than this value, the emitter will generate no whitewater particles. |
| Max Turbulence (A) | When the fluid turbulence around an emitter lies in the range of Min Turbulence up to this value, proportionally increase the rate of generated whitewater particles up to the Turbulence Emission Rate. |
| Min Energy Speed | When the fluid speed around an emitter is less than this value, the emitter will generate no whitewater particles. |
| Max Energy Speed | When the fluid speed around an emitter lies in the range of Min Energy Speed up to this value, proportionally increase the rate of generated whitewater particles up to the emitter's generation rate. |
| Max Particles | Maximum number of particles (in millions) that the whitewater solver is allowed to simulate. The solver will stop generating new whitewater particles to prevent exceeding this limit. If set to 0, the simulator will not limit the particles. However, We still recommend setting some reasonable limit to prevent generating too many particles which can slow down simulation and require large amounts of cache storage. |
| Enable Emission Near Domain Boundary (A) | Enable whitewater emitters to generate particles at the edges of the domain bounding box. |
| Enable dust emission near domain floor | Allow whitewater emitters to generate dust near the domain floor. |
There are other simulation settings and set ups that can cause side effects and affect the amount of whitewater generated. Specifically, settings that affect the frequency of physics calculations such as simulation resolution, frame rate, and speed/timescale can affect whitewater generation. It is possible that changes in settings that increase the frequency of simulation calculation can result in less whitewater being generated.
For more information on settings that affect simulation behaviour, see this topic: Scene Troubleshooting: Fluid behaviour changes when changing Frame Rate, Speed, or Substeps.
Explanation: Whitewater generation works by scattering emitters throughout the fluid in areas where whitewater is likely to be generated, such as in areas of high turbulence or at wavecrests. Each emitter is calculated to emit particles at a certain rate in particles per second based on the emission rates, fluid speed, turbulence, and sharpness of wavecrests. The minimum number of particles that an emitter can generate during a single simulation substep is one particle.
It is possible that a change in settings that results in more frequent substeps can cause emitters to no longer generate particles (What are substeps?). For example, if an emitter regularly generates 1 particle/substep at the current settings, a change that doubles the number of substeps will now generate 0.5 particles/substep which rounds down to 0, or no particles emitted.
Solution: If this is an issue, this may indicate that the current whitewater emission settings are not optimal for this set up. The solution is to increase the amount of whitewater generation either by increasing Wavecrest/Turbulence Emission Rates or by Lowering the Min/Max Energy Speed thresholds. For more information on these solutions, see this topic: Scene Troubleshooting: Simulation not generating enough whitewater.
| Advection Strength | The strength of the advection force that carries the foam with the fluid velocity. High values cause tighter streaks of foam that closely follow the fluid motion. Lower values will cause more diffuse and spread-out foam. |
| Depth (A) | The thickness of the foam layer. |
| Offset (A) | The height offset of the foam layer in relation to the fluid surface. If set to a value of 1.0, the foam layer will rest entirely above the fluid surface. If set to a value of -1.0, the foam layer will rest entirely below the fluid surface. |
| Drag Coefficient | Controls how quickly bubble particles are dragged along with the fluid velocity. If set to 1.0, bubble particles will be immediately dragged into the flow direction of the fluid. |
| Buoyancy Coefficient | Controls how quickly bubble particles float towards the fluid surface against gravity. If set to a negative value, bubbles will sink away from the fluid surface with gravity. |
| Drag Coefficient | The amount of air resistance on a spray particle. |
| Drag Coefficient | Controls how quickly dust particles are dragged along with the fluid velocity. If set to 1.0, dust particles will be immediately dragged into the flow direction of the fluid. |
| Buoyancy Coefficient | Controls how quickly dust particles sink towards the ground along with gravity. Decreasing this value will cause dust particles to sink more quickly. If set to a positive value, dust will float towards the fluid surface against gravity. |
| Min Lifespan | Minimum whitewater particle lifespan in seconds. |
| Max Lifespan | Maximum whitewater particle lifespan in seconds. |
| Lifespan Variance | A random number of seconds in this range will be added or subtracted from the whitewater particle lifespan. |
| Foam Lifespan Modifier | Multiply the lifespan of foam particles by this value. |
| Bubble Lifespan Modifier | Multiply the lifespan of bubble particles by this value. |
| Spray Lifespan Modifier | Multiply the lifespan of spray particles by this value. |
| Dust Lifespan Modifier | Multiply the lifespan of dust particles by this value. |
Settings used to set open or closed boundaries for each side of the domain for whitewater particles. For more information on boundary collision settings, refer to the Domain Simulation > Boundary Collisions topic.
| Boundary Collisions Mode | Select how to set the domain boundary collisions. Inherit Use the same boundary collisions as set in the FLIP Fluid Simulation panel. Custom Set custom boundary collisions for each Foam/Bubble/Spray/Dust particle type. For example, you may want to use the default boundary collisions for all particle types except add a special case for Spray to allow for these particles to be removed when colliding with the domain sides and ceiling. |
This UI section lists the FLIP Fluid Obstacle objects present in the scene with their corresponding Whitewater Influence and Dust Emission Strength parameters.
Refer to Domain > Display > Whitewater Particle Display and Render.
This submenu contains options to enable exporting simulation attributes for the whitewater particles. After baking, these attributes can then be accessed in a shader, in a geometry node network, or in other areas of Blender. Refer to the Attributes and Data documentation for more information.
These features are currently affected by a bug in Blender and are hidden by default. Unhide this feature by enabling the Developer Tools option in the addon preferences. See the Preferences > Developer Tools documentation for more information on how to enable this feature, the features affected by this bug, and how to work around this issue.
Whitewater in the FLIP Fluids addon, Blender's fluid simulators, and many other simulation systems are simulated and rendered using particles, and are also often rendered as spheres. In your render, you may be seeing the individual spheres of the whitewater particles that are being simulated. The trick to getting good looking whitewater renders are a combination of high resolution (high detail simulation), simulating a large number of whitewater particles, and rendering the particles as very small spheres. Here are some tips:
- You will often want to simulate a large number of particles, generally in the range of 2 million to 6+ million particles. See this topic for how to generate more particles: Scene Troubleshooting: Simulation not generating enough whitewater.
- We often suggest simulating a higher resolution simulation, which generates more whitewater and improves detail of whitewater motion. For example, beach simulations are often in the range of 300 - 400 resolution (or even higher!)
- We also suggest increasing the Wavecrest/Turbulence emission rates if your simulation is not generating enough whitewater. It is often good to set these both as the same value.
- Tip: If you end up simulating too much whitewater, you can always reduce the amount of particles rendered by adjusting the display percentages in the FLIP Fluid Display Settings > Whitewater Display menu
- Tip: you can see how many whitewater particles are contained in each frame by viewing the FLIP Fluid Stats > Frame Info panel.
- For rendering, you will want to set the size of the particles so that they are quite small. Often small enough so that individual particle floating by themselves are barely visible in the render. This helps the particles blend into each other during rendering and helps hide the fact that they are just a large amount of separate spheres. This option can be found in the FLIP Fluid Display Settings > Particle Scale menu.
- The camera angle and distance can also play a very large role in rendering your effect. Whitewater is often best rendered at a distance, which makes the individual spheres less noticeable.
- A popular technique is to render with motion blur or to use post-processing software to quickly add motion blur to the rendered animation. Motion blur helps smooth the particle motion in the render which has the effect of blending the particles into each other. Motion blur also helps with video compression when rendering particles as a bonus! Common software for post-processing motion blur are Adobe After Effects, DaVinci Resolve, and ReelSmart Motion Blur.
- Related topic: Setting up motion blur