Domain Surface Settings
This page documents the domain settings for the FLIP Fluid Surface panel.
All parameters in this panel must be set before baking for changes in the simulation to take effect.
This section contains settings to control the mesh generation quality.
Video: Comparing Surface Mesh Subdivisions
| Enable Surface Mesh Generation | Enable the generation of the liquid surface mesh. If disabled, the surface mesh and any surface attributes will not be generator or exported to the simulation cache. |
| Subdivisions | The level of detail of the generated surface mesh. This value is the number of times that the simulation voxels are split. For example, a subdivision of 1 splits each voxel into 2x2x2 blocks, and a subdivision of 2 splits each voxel into 3x3x3 blocks. Higher subdivision levels result in a higher resolution mesh. In general our advice is: - A value of 0 is good for speeding up the simulation while testing or for situations where high detail is not needed such as effects viewed from a distance - A value of 1 is good for a final simulation result and is the default value - A value of 2 is good in situations where very high detail is needed such as in slow motion simulations or high viscosity simulations where flickering artifacts can be noticeable - Higher values can help with further reducing flickering issues but at a large added cost of simulation performance and diminishing returns in quality |
| Particle Scale | The particle scaling factor to use for mesh generation. The surface mesh generation works by converting the internal fluid particles into a triangle mesh. This is done by giving the particles a size, merging them together into a volume, and then creating a mesh around the volume. A larger particle scale value such as around 1.0 - 1.5 can help smooth out the surface mesh, but also can result in a more 'blobby' mesh with less detail. Values lower than 1.0 are not recommended and can result in a mesh with holes and gaps. For most situations, this setting does not need to be adjusted. |
This section contains settings to control what areas of the domain or which portions of fluid are converted to a surface mesh.
| Meshing Volume Mode | Determine what volume of the fluid will be converted into a mesh. Domain Volume Mesh all fluid that is inside of the domain. Object Volume Mesh only fluid that is inside of a custom object. |
| Object | An object selector for the custom meshing volume. Only fluid that is inside of this object will be meshed. This setting is only available if the Meshing Volume Mode is set to Object Volume. Note: This object must have manifold/watertight geometry. |
| Export Animated Mesh | Export the custom object mesh as an animated one. This setting is only available if the Meshing Volume Mode is set to Object Volume. TIP: Animated objects can be slower to export, so use this option only if necessary, such as for armatures or parented objects. Objects with keyframed position/rotation/scale do not require this option to be enabled. |
Settings to control weather or not the surface that touches the domain boundary walls will be meshed.
| Remove Mesh Near Boundary | Remove parts of the surface mesh that are near the domain boundary. If a meshing volume object is set, parts of the mesh that are near the volume object boundary will also be removed. |
| Distance | Distance from domain boundary to remove mesh parts. This value is in number of voxels. If a meshing volume object is set, this distance will be limited to 1 voxel. This setting is only available if the Remove Mesh Near Boundary checkbox is Enabled. |
These options control how the surface mesh is generated against solid obstacle boundaries and can sometimes have consequences on the render result. The mesh generator creates a smooth interface between the fluid and obstacles, a nice improvement over the voxelization artifacts that often appear when using the built-in Blender Mantaflow fluid simulator. For most cases, the default settings will generate the desired mesh result.
| Enable | Enable smooth meshing against obstacles. If disabled, obstacles will not be considered during meshing and all fluid particles will be converted to a mesh. |
| Meshing Offset Mode | How the fluid will be meshed against obstacles. Inside Surface Generate fluid-solid interface on the inside of the obstacle. The fluid surface will penetrate the obstacle. On Surface Generate fluid-solid interface directly on the obstacle surface. This may lead to rendering artifacts if using a transparent material due to overlapping triangles between the fluid and obstacle object. Ouside Surface Generate fluid-solid interface on the outside of the obstacle. This will leave a gap between the fluid surface and obstacle. |
The choice meshing offset mode will affect how the fluid-solid interface appears when rendering your simulation. In general we recommend:
- Inside Surface - Use when the obstacle is opaque and the fluid is transparent. This will result in a more clear and bright obstacle underneath the liquid. If Outside Surface is chosen for this case, the obstacle can often look too dark.
- On Surface - Use when both the obstacle and fluid are opaque or if the obstacle is not rendered. If this option is chosen when either the surface or obstacle is transparent, artifacts at the fluid-solid interface may appear due to z-fighting.
- Outside Surface - Use when both the obstacle and fluid are transparent or if the obstacle is transparent and the fluid is opaque. If Inside Surface is chosen for this case, the fluid penetration of the obstacle will be apparent.
This submenu contains options to enable exporting simulation attributes for the surface mesh vertices. 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.
- To produce a smoother mesh surface, try increasing the Blender Smooth Modifier values on the fluid surface object.
- When the meshing subdivision level is set higher than 0, you might start seeing bumps in the surface mesh. This is caused by individual fluid particles being defined due to higher mesh quality. To smooth out these bumps, increase the number of repetitions using a smooth modifier.
- The values used on the smooth modifier will depend on the effect and desired results, but in general a larger repeat value will be needed for meshes that have denser polycounts such is in higher detailed simulations. Adjusting the modifier values do not require re-baking the simulation, so it is quick and easy to experiment with the values.