Obstacle Object Settings
Obstacle objects are solids for the fluid to interact with in the simulation.
Need help with how to create simulation objects? Take a look at our getting started guide: Creating Your First FLIP Fluids Simulation.
Video Guides:
- FLIP Fluids Guide Episode 2A: Domain, Fluid, Obstacles objects.
- FLIP Fluids Guide Episode 5: Mastering Imported Geometry
Obstacle object settings can be viewed in the Physics Properties by selecting the object.
- Obstacle objects are required to be Blender mesh type objects.
- Object geometry is required to be Manifold/Closed/Watertight in order to work correctly and predictably within the FLIP Fluids simulator. The objects are required to have volume and planar surfaces cannot be used.
- The object should be sufficiently large/thick in order to be resolved on the simulation grid. The smallest/thinnest geometry features of the object should cover at least one voxel on the simulation grid (What is the simulation grid?).
- If the object contains thin walls that cannot be fully resolved on the grid, this can result in leakage. See this topic for more information and how to resolve these types of issues: Scene Troubleshooting: Thin Obstacles, Leaking Fluid.
- If the object is animated, the mesh geometry must not change topology between frames. This means that each frame of the animation must have the same number of vertices and triangles and that the vertices are always connected to the same neighboring vertices.
- If the object animation is more complex than keyframed location/rotation/scale, enabling the Export Animation Mesh option will be required.
- Complete Guide Episode 5: Mastering Imported Geometry - All about using imported geometry in the FLIP Fluids addon and solutions to common issues.
Related Topics
- For easily containing liquids inside of closed objects, the Obstacle > Inverse option can be useful for this scenario.
- Simulations with large amounts of rapid obstacle motion or liquids inside of moving containers can suffer from volume loss. See this topic for more information and how to resolve these types of issues: Limitations: Volume and Mass Preservation.
| Enable | Whether the object will be present in the simulation. |
| Inverse | Turn the obstacle 'inside-out'. Enabling this option will make the inside of this object empty while everything outside of the obstacle will become solid. This option is useful for creating perfect containers that hold liquid without leakage. See the Inverse Obstacle Workflow documentation topic for how to use this option in your projects. |
| Friction | The amount of friction between the fluid and the surface of the obstacle. NOTE: Other simulation settings may have side effects that affect amount of friction on an obstacle. For more information, see Domain World > Friction > Side effects that affect friction. |
| Velocity Scale | Scale the moving obstacle velocity by this amount within the simulation. Values greater than 1.0 will exaggerate the velocity and the simulation will behave as if the object is moving faster than it actually is. Values between 0.0 and 1.0 will dampen the velocity, but may result in increased volume loss. Negative values will reverse the direction of velocity. This setting is for artistic control and any value other than 1.0 will not be physically accurate. |
| Whitewater Influence | Scale the amount of whitewater generated near this obstacle by this value. A value of 1.0 will generate the normal amount of whitewater, a value greater than 1.0 will generate more, a value less than 1.0 will generate less. Whitewater simulation must be enabled for this setting to take effect. This parameter is also displayed in the Whitewater Panel. |
| Dust Emission Strength | Scale the amount of dust particles generated near this object by this value. A value of 1.0 will generate the normal amount of dust, a value greather than 1.0 will generate more, a value less than 1.0 will generate less. Whitewater dust simulation must be enabled for this setting to take effect. This parameter is also displayed in the Whitewater Panel. |
| Sheeting Strength Multiplier | Scale the amount of fluid sheeting strength against this obstacle by this value. The resulting sheeting strength after scaling will be clamped at a maximum of 1.0. This parameter will only take effect if the sheeting effects feature is enabled. |
| Expand | Expand the obstacle mesh by this value. If the obstacle mesh is composed of multiple mesh pieces, each piece will be expanded separately. TIP: This setting can be used to prevent fluid from slipping through small cracks between obstacles, such as in fractured objects. Only a small value should be used (e.g. max 0.05). This option is not applicable to situations where fluid is leaking through thin walls (See this topic for leakage solutions). |
In the first stage of simulation baking, the addon will begin by exporting all object geometry for the animation. These settings allow for control on how and if the geometry should be exported. These settings are only applicable to the object's mesh geometry and do not apply to the object's options and parameters.
| Export Animated Mesh | Export the obstacle object mesh as an animated one. 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. |
| Skip re-export | If enabled, the addon will skip re-exporting this mesh when starting or resuming a bake. If this mesh has not been exported or is missing files, the addon will automatically export the required files. Notes: Animated mesh export can slow down the export stage if the mesh is complex and contains a lot of geometry. Skipping mesh export for animated meshes will speed up export and help your simulation start quicker. If your animated mesh geometry or motion has changed, you will need to disable this option or force the object to export so that the addon will re-export the mesh geometry. |
| Force Re-Export On Next Bake | When enabled, this option will force the addon to re-export the object’s mesh data the next time that the user bakes or resumes the simulation. This option overrides the Skip Re-Export option. After the object has been re-exported, the force export option will be automatically disabled so that subsequent bakes will continue skipping the mesh for export. This option is only applicable if the Skip Re-Export option is enabled. TIP: Useful for if you have a complex animation or object with a lot of geometry with the Skip Re-Export option enabled to save time during export. Use this option if you make an change to your mesh geometry and want to easily mark the object to update the next time you bake/resume the simulation. |
This operator will copy the Obstacle settings of the active object (highlighted object) to all other selected FLIP objects of the same type. Hint: The settings displayed in this UI panel will be the settings of the active FLIP object.
Notes:
- Keyframed settings will not be copied - these will need to be copied manually, such as through the Blender graph editor.
- Settings cannot be copied to an object that has not already been set as an Obstacle type object. You will first need to set non-FLIP objects to a FLIP type. Tip: to set multiple objects to a FLIP object quickly, use the FLIP Fluids sidebar > Add Objects operators.
No, it is okay for your object to be larger than the domain. However, we do not recommend the object to be very large compared to the domain size. Objects much larger than the domain will require more RAM and can slow down computation or you may even run out of memory. For very large objects, you may want to create smaller trimmed down proxy object for use in the simulator.
Is your obstacle not behaving as expected? See the first tip in our 10 Tips to Improve Your FLIP Fluids Workflow in Blender article/video.