Domain Object Settings
This page documents settings for the FLIP Fluid Domain object. The simulation domain is the volume where the fluid will be simulated. Fluid cannot exist outside of the domain object. The domain object contains a large number of settings to control the fluid simulation.
Need help with how to create a FLIP Fluid Domain? Take a look at our getting started guide: Creating Your First FLIP Fluids Simulation.
- The domain object should be created from a cuboid shaped object.
- The domain object must be aligned to the Blender X/Y/Z axis' and cannot be rotated.
- The location and scale of the domain object cannot be keyframed or animated.
- The domain object should not contain any modifiers.
- There can only be one domain object in a single Blend file.
The many domain settings are split into tabbed panels, each with their own documentation page.
| Simulation Settings | Adjust the domain grid resolution, physical size, frame rate, begin running a fluid simulation, and control other important aspects of baking. |
| Cache Settings | Simulation results are stored in an external location called the "Cache". Set and manage the simulation cache directory in this panel. |
| Display Settings | Adjust how the simulation will be displayed in the viewport and during a render. |
| Surface Settings | Configure mesh generation and data settings for the fluid surface. |
| Particle Settings | Enable and configure fluid particle export and data settings for fluid particles. |
| Whitewater Settings | Enable and configure the whitewater simulation to generate foam, bubbles, spray, and dust particles. |
| Attributes | Generate simulation attributes for the fluid surface and whitewater particles for use in rendering and in Geometry Nodes. The attribute options are not contained in their own panel and are instead located across multiple panels: Surface Settings, Particle Settings, Whitewater Settings, and World (Viscosity) Settings. |
| World Settings | Adjust settings related to the world that the fluid lives in as well as properties of the liquid will affect how the fluid behaves within the simulation. |
| Material Settings | Apply Blender materials to the fluid surface and whitewater particles. |
| Advanced Settings | Configure frame substeps, stability, multithreading, performance, optimization settings, and more. |
| Debug Settings | Tools for debugging the domain grid, fluid particles, force fields, and solid obstacles. |
| Stats Settings | View simulation, solving status, timing, and mesh statistics. |
The fluid surface, fluid particle, and whitewater meshes are loaded into Blender from the simulation cache and are stored in the FLIPMeshes collection.
| fluid_surface | Triangle meshes representing the fluid surface will be stored in this object. |
| fluid_particles | Vertex only meshes representing the simulation fluid particles will be stored in this object. |
| whitewater_foam | Vertex only meshes representing the whitewater foam particles will be stored in this object. |
| whitewater_bubble | Vertex only meshes representing the whitewater bubble particles will be stored in this object. |
| whitewater_spray | Vertex only meshes representing the whitewater spray particles will be stored in this object. |
| whitewater_dust | Vertex only meshes representing the whitewater dust particles will be stored in this object. |
Simulation Mesh Notes
- The whitewater_foam, whitewater_bubble, whitewater_spray, and whitewater_dust objects will only be present if the whitewater simulation feature is enabled. See Domain Whitewater Settings.
- To keep a persistent copy of a loaded frame mesh in your .blend file, you may simply duplicate the loaded mesh (SHIFT+D) to create a separate Blender object. This can be useful for still rendering and for editing a single mesh that won't be reloaded from the simulation cache. Alternatively, you may also export the frame mesh to one of Blender's supported export formats and import back into a Blend file.
- To export an animated simulation for archiving simulations, for exporting to other software, or for sending to a render farm, use Blender's Alembic exporter. See Alembic Export Support.
The fluid surface, whitewater, and fluid particle simulation meshes are initialized with geometry node modifiers that can be used to customize the display and render of the simulation. These modifiers can be found in the Modifier Properties panel (wrench icon) are prefixed with the name FF_GeometryNodes.
Updating Geometry Node Modifiers: Newer versions of the addon may contain new features in the geometry node modifiers. For how to update these modifiers in an older Blend file, see the FLIP Fluids Sidebar > Geometry Node Tools > Update Geometry Node Modifiers operator.
Rendering the simulation with motion blur requires additional configuration outside of this geometry nodes modifier. To automatically set up the simulation for motion blur rendering, use the FLIP Fluids Sidebar > Geometry Node Tools > Initialize Motion Blur operator.
| Enable Motion Blur | Enable to transfer motion blur vectors to Blender's internal velocity attribute. |
| Scale | Scale the amount of motion blur by this amount. |
| Apply Simulation Time Scale | Automatically scale motion blur according to the baked simulation time scale for consistent screenspace motion blur. If applying simulation time scale to motion blur, you will not need to manually sync the motion blur scale to the simulation time scale for slowmotion effects. |
| Apply Simulation World Scale | Automatically scale motion blur according to the baked simulation world scale for consistent screenspace motion blur. |
| Shade Smooth | Shade smooth the fluid surface mesh. Disable this option for flat shading. |
| Remove Mesh Near Domain Boundary | Remove parts of the mesh near the domain boundary to create a surface-only mesh. This feature works similar to the Domain > Simulation > Meshing Against Boundary feature except that the result is not baked into the mesh and can be applied after the simulation. |
| ±X/Y/Z Removed Sides | Enable or disable removing the fluid surface against this side of the domain. For example, X- represents the side of the domain that is in the negative X direction and X+, the side of that is in the positive X direction. If enabled, the fluid surface against this side of the mesh will be removed. |
| Distance | Distance from domain boundary to remove parts of the mesh. |
| Flatten Mesh Near Domain Boundary | Flatten the surface mesh towards a water level near the edges of the domain boundary. Useful for compositing or combining the surface mesh into a larger ocean plane. This feature should be used in combination with the Remove Mesh Near Domain Boundary feature, using geometry nodes or domain settings. |
| Water Level Mode | How to set the Z value of the water level. Value Use a Z value for the water level. Object Use Z value of an object's coordinates for the water level. |
| Flattened Width | Width of the flattened edge at the domain boundary. |
| Transition Width | Width of the smoothed flattening transition. |
| Store Displacement Attribute | Store amount of applied Z displacement as a flip_displacement named attribute. Enabling is required for matching displacement in the whitewater and fluid particle simulation meshes. |
| Store Transition Mask Attribute | Store transition mask as a flip_transition_mask named attributes. Values are in the range [0.0, 1.0] where 0.0 is fully flattened and 1.0 is no flattening. Useful for fading out the edges of the fluid surface in a shader. |
These parameters are used as part of the Compositing Tools feature set.
The fluid particles and whitewater share some of the same geometry nodes features. The following features are supported on both the fluid particle and whitewater meshes.
A quirk of Blender's geometry nodes system is that a material needs to be specified within the node group when the geometry type changes. For fluid and whitewater particles, the geometry type may change between Vertices, Point Clouds, and Instances depending on the modifier settings. When the geometry type changes, the resulting geometry will not automatically inherit the material set in the simulation mesh material properties, which is why these modifier settings are needed.
| Apply Material | Apply the specified material to the particles. Disable to inherit material from instances if object instancing is used. |
| Material | Material to assign to the fluid particles when the Apply Material option is Enabled. When assigning the simulation mesh a material in the domain settings or in the material properties menu, the addon will try to automatically sync this modifier property to the set material. Depending on the Blender context, syncing this material may not always be possible. If the material is not displaying correctly in the render, the first thing to check is if this modifier value contains the correct material. |
Refer to the Fluid Surface Modifier Motion Blur documentation.
| Particle Display Mode | How to display and render the particles. None Display the particles as raw vertices. Use this mode if customizing the particles in a custom geometry nodes modifier. Note: vertices are not renderable in Blender. Point Cloud Display the particles as a Point Cloud type object. This is the most performant method to render and display particles in Blender. Instancing Display the particles with object instances. This is the least performant method to render and display particles in Blender, but offers more customizations over the shape. Try to limit the amount of particles rendered using this method to avoid performance issues. |
Point Cloud and Instancing Options
The following options are supported in both Point Cloud and Instancing particle display modes.
| Particle Scale | Object scale of particles in Blender Units. |
| Particle Scale Multiplier | Multiply particle scale by this value. Useful for precision scaling for small particle sizes. |
| Particle Scale Random | Amount of linear randomized particle scaling. |
| Random Bias | Random bias of particle scaling distribution. Values less than 1.0, bias towards small particles. Values greater than 1.0, bias towards large particles. Value equal to 1.0, no bias. |
Particle Instancing Options
The following options are supported when the particle display mode is set to Instancing.
| Instancing Mode | How to instance objects on vertices. Icosphere Instance icosphere objects over the particles. Object Set a custom object to instance over the particles. Collection Randomly instance objects from a collection over the particles. |
| Randomize Instance Rotation | Apply a random rotation for each particle instance. |
| Align Instance to Velocity | Align instance Z axis to the particle velocity vector. Requires enabling the FLIP Velocity attribute before baking. |
| Shade Smooth Instances | Option to specify whether to smooth shade or flat shade the instance objects. |
| Realize Instances | Convert particle instances to mesh geometry. Required for transferring simulation or custom attributes the particle geometry. This option can generate a large amount of geometry and result in performance issues for large amounts of particles or for high geometry instances. |
| Match Flattened Surface Displacement | If the Surface Modifier > Flatten Mesh Near Domain Boundary option is enabled, apply the same displacement to the particle Z level. |
This feature requires enabling the fluid particle and/or whitewater Lifetime attributes (See Attributes Documentation).
| Lifetime Based Particle Scaling | Scale particles at the end of their lifetime. Requires enabling the FLIP Lifetime attribute before baking. |
| Final Scale Factor | Particle scale factor at the end of the particle lifetime. |
| Scaling Duration | Duration of the scaling transition in simulation seconds. |
| Lifetime Offset | Time offset for when the scaling transition begins. |
| Store Lifetime Scaling Transition Attribute | Store transition values as a flip_lifetime_transition named attribute. Values are in range [0.0, 1.0], starting at 0.0 before scaling transition begins and ending at 1.0 when scaling transition is complete. Useful for shading the particles based on scaling transition. |
These parameters are used as part of the Compositing Tools feature set.
The following features are supported only on the fluid particle simulation meshes.
Scaling particle based on age requires enabling the fluid particle Age attribute (See Attributes Documentation).
| Age Based Particle Scaling | Scale particles at the beginning of their age. Requires enabling the FLIP Age attribute before baking. |
| Starting Scale Factor | Particle scale factor at the start of the particle age. |
| Scaling Duration | Duration of the scaling transition in simulation seconds. |
| Age Offset | Time offset for when the scaling transition begins. |
| Store Age Scaling Transition Attribute | Store transition values as a flip_age_transition named attribute. Values are in range [0.0, 1.0], starting at 0.0 before scaling transition begins and ending at 1.0 when scaling transition is complete. Useful for shading the particles based on scaling transition. |
Filtering particles based on Source ID requires enabling the fluid particle Source ID attribute (See Attributes Documentation).
| Filter Particles by Source ID | Show or hide particles based on Source ID attribute. Requires enabling the FLIP Source ID attribute. Useful for selectively rendering particles based on the Fluid/Inflow object that they are emitted from. As an example: in a variable density simulation, you may only want to display the lower density particles that float to the surface. This can be done by assigning Source ID values to the Fluid/Inflow objects and setting this modifier to only display the Source ID of the lower density particles. |
| Source IDs 0 - 8 | Checkboxes from 0 to 8 to control whether to show or hide particles with the corresponding Source ID. For example, disabling checkbox 2 will hide particles with Source ID = 2. |
I am new to the FLIP Fluids addon or fluid simulation, how do I start learning what all of these settings do?
We suggest starting with small simple experiments and not to get too ambitious with your first project. You might have the urge to jump right in and create a huge complex simulation scene, but we suggest scaling back and learning the basics first. Learning a new tool can take a bit of time and jumping into a large project right away can lead to frustration.
We suggest beginning with our getting started guide: Creating Your First FLIP Fluids Simulation.
To learn what a setting does, start by creating a basic scene. Maybe just a ball of fluid dropping, or an inflow pouring into a cube. Read along with the documentation to get an idea of what the parameter does and try only adjusting a single parameter at a time to test how it works. Lowering the resolution to speed up simulation will help you test and compare different parameter values quickly.
In addition to learning through experimentation and documentation, you can check out our Video Tutorial Series and Learning Resources page.
The FLIP Fluids addon contains a lot of different settings to customize how the fluid looks and behaves. Many of the settings are for specific use cases and do not need to be changed for most scenarios and effects. The default values are set up so that they work well with a domain that is roughly the width of four Blender units or more. For many simulation setups, you'll not need to change very many settings outside the default values.
With all of these settings, the UI can be intimidating to a new user of the addon. For beginners, you may enable the Beginner Friendly Mode in the addon preferences. This option will hide all but the most basic and commonly used settings.
In general, all panels except the Display Panel and Material Panel need to be set before baking. The display and material panel all contain settings for viewport display and render setup which can be changed after baking a simulation. The exception is the Debug Panel which contains a mixture of simulation and display settings.
If you are unclear whether a setting must be set before baking, the top of the documentation for each panel will state which parameters must be set before baking.
Ideally, the domain should fit as tightly as possible around the fluid effect that you are trying to achieve. A tight fitting domain maximizes performance.
Why should I make my domain fit more tightly around the effect? The simulator makes calculations over the entire domain/grid volume. If there is a lot of empty space in the domain, this can lead to more calculations and longer simulation times.
A tighter fitting domain can also concentrate the grid resolution. A tighter fitting domain at the same resolution may have smaller voxels. This can help obstacles and other simulation objects show up better on the grid. This will also increase voxel coverage for fluid generating objects, leading to larger amounts of fluid particles and more fluid particles can help produce high quality motion and detail.
Related Topics:
- See the Simulation: Grid Info topic which explains the simulation grid in detail.
- See the first topic in our '10 Tips' article/video to learn more about the simulation grid and how to visualize and debug the grid.
- For more tips on improving simulation performance, see this topic: Scene Troubleshooting: Simulation baking is taking too long to compute!
- Is your fluid never going to reach the top of your domain? Reduce empty space by lowering the domain ceiling.
- Will splashes not reach the sides of your domain? Consider closing in the sides of your domain to reduce the empty space.
- Are you beginning your simulation by dropping fluid from a large height? If the motion of the fall is predictable, consider animating the fall instead and beginning the simulation right before the fluid hits the ground. You may be able to lower the ceiling if you take this route, and you will avoid having to calculate the simulation frames during the fall. Make sure to emit the fluid at a speed downwards as if it were falling.
- Are you simulating a deep ocean or pool of liquid? Think about whether you can get away with simulating a more shallow body of water. Will there be motion deep under the water that will affect the surface? Will you be able to see the bottom of the liquid in the render? If not, consider raising the domain floor and simulating a thinner layer of water. This will also reduce the amount of fluid that needs to be simulated which will speed up baking times.
- Do you need to resize your domain, but don't want to change the voxel size so that the simulation maintains a constant level of detail? Enable the Lock Voxel Size before resizing your domain. When enabled, this option will automatically update the simulation resolution setting so that the voxel size is the same before and after resizing.