Houdini 18.0 Shelf tools

Ocean Flat Tank shelf tool

Creates a FLIP fluid simulation from an underlying ocean surface.

This tool creates a FLIP tank simulation with particles initialized from an ocean surface with velocities. A boundary layer of particles suppresses reflections at the edge of the tank, contributes ocean velocities back to the simulation, and maintains the water volume level to match the ocean. This boundary layer also applies ocean velocities at the closed boundaries to allow in/out-flow of the FLIP simulation.

The Ocean Flat Tank can be a static tank or can follow a moving object through the ocean.

The Ocean Spectrum node allows you to shape the initial frame of your simulated ocean, and Ocean Source controls the outputs.


For more information, see the differences between ocean tank types help page.


Several of the ocean tanks use the Narrow Band feature in the FLIP Solver by default. If the traditional full tank is desired, it can be changed back by selecting Particle Field in the FLIP Object.

Using Ocean Flat Tank

  1. Click the Ocean Flat Tank tool on the Oceans tab to create a tank.

  2. Select an animated object to follow and press Enter to confirm your selection. If no object is selected, you will be prompted to place a static tank.

Changing the look of your ocean

To...Do this

Set the height of the wave

Navigate to the Ocean Spectrum node and adjust the Wave Scale parameter on the Wave Amplitude tab.

This value is multiplied by the Speed parameter on the Wind tab.

Set the direction of the waves

Navigate to the Ocean Spectrum node and adjust the Directional Bias parameter on the Wind tab.

This controls how many frequencies are moving in the same direction as the wind. Increasing this value will cause more frequencies to travel in the same direction, which is useful for creating shoreline effects.

You can also try increasing the Directional Movement parameter. This will dampen the waves moving in the opposite direction of the wind, leaving only the ones moving in the same direction.

Control the height of the peak

Navigate to the Ocean Spectrum node and adjust the Chop parameter on the Wind tab.

Increasing this parameter creates sharp peaks on waves. However, if this value is too high waves, may invert on themselves.

Add more detail to your ocean

Increase the Resolution Exponent parameter on the Ocean Spectrum node.


The Resolution Exponent parameter will not only determine the quality of your ocean, but also the size of the texture maps that you will eventually write out.

Create a large ocean

Use the Large Ocean shelf tool.

Understanding the network of nodes

There are three important layers to focus on when creating your ocean. First create the ocean, next add whitewater, and finally add specularity for the whitewater.


Disable all whitewater nodes at the OBJ level while you work on your ocean, then disable the ocean nodes while you work on your whitewater.

The first set of nodes control the ocean itself.

  1. fluidtank_initial controls the first frame of your simulation. This is where you can shape the initial frame of your tank with Ocean Spectrum and control the outputs with Ocean Source. This includes the size of your tank, the depth of the water etc.

  2. AutoDopNetwork controls the simulation of your tank. This is where you will find the FLIP Tank and FLIP Solver. The FLIP simulation will contain Volume Source DOPs to sink and source the boundary layer particles, and a POP Advect By Volumes POP to add ocean velocities to the simulation.

  3. fluidtank_fluid is the result of #1 and #2 combined, and is where the results are rendered. After the simulation is done, this node collects the fluid particles, sets up a material, creates some nodes for surfacing to finish the effect.

  4. fluidtank_interior is also used for rendering, and for creating the volumetric effect that one of the shaders applies to the interior of the fluid. It controls the volume beneath the surface, such as how cloudy or murky the water will appear.

The next set of nodes are to control the whitewater.


To add whitewater to your simulation, use the Whitewater tool on the Oceans shelf.

  1. whitewater_source is where the spray and foam is coming from.

  2. whitewater_sim is where the whitewater simulated. This is where you can modify the animation.

  3. import_whitewater is the result of #1 and #2 combined.


Do not try to set up a whitewater simulation from scratch. Always use the tools. For more information about using whitewater, see the Whitewater help.

For more information see How to animate a wave tank with whitewater.

Understanding the extended ocean surface nodes

The Guided Ocean Layer and Ocean Flat Tank tools also create a network for rendering an "extended" fluid surface that can stretch to the horizon and be rendered with ocean displacement to provide a seamless integration between a FLIP simulation and the surrounding source ocean.

  1. The Particle Fluid Surface node (called particlefluidsurface1) creates the extended FLIP mesh. The settings on the Flattening tab of this node will flatten the fluid simulation near the edges of the simulation area, and extrude the edges of the polygonal mesh outwards to form an extended flat surface. This flat area surrounding the simulation is then rendered with ocean displacement.

  2. The two Particle Fluid Mask nodes (called particlefluidmask1 and hifrequency_mask) will create masks on the input ocean spectra that limit the render-time ocean displacement to specified areas of the simulation, usually where there is little velocity, vorticity, or splash height in the fluid. These nodes also blend in ocean displacement around the edges of the simulation bounding box to match the flattening applied while surfacing. The hifrequency_mask node additionally filters the incoming ocean spectra to remove all but the highest-frequency waves, usually so these can be applied to the simulated FLIP mesh and allow it to better integrate with the surrounding ocean.

  3. The surface_preview node is a fast preview of the FLIP simulation that then samples the created mask to allow visualization of the ocean contribution using a viewport visualizer on the mask attribute. The oceanevaluate1 node applies ocean displacements to that preview based on the calculated masks.

  4. The split_spectra_masks node will separate out the static ocean spectra from the time-dependent masks created by the masking nodes. They are cached to two different sets of files to take advantage of the Ocean Surface material’s ability to have separate spectra and mask inputs.

Tips for improving the look of your water

  • The defaults for the tank will create a low res simulation, which makes it easy to animate. However, to create a nice looking render, you will need to change some of the defaults. For example, you will need to increase the number of particles in your scene. Decreasing the Particle Separation parameter to about 0.03 will create a simulation with approximately 30 million particles.

  • Add an environment light to your scene. Water reflects and refracts a lot of the environment around it, so having an environment map in your scene will significantly improve the look.


    In your Environment Map parameter, navigate to the HFS/houdini/pic/ folder and choose the sky file DOSCH_SKIESV2_${F2}SN_lowres.rat.

See also

Shelf tools

Using the shelf

  • Customize the shelf

    How to change the look of the shelf, change and rearrange its contents, and create your own shelf tools.

Shelf tabs

  • Create tab

    Tools on the Create tab let you create and place primitives, curves, and null objects in the scene view.

  • Modify tab

    Tools on the Modify tab let you easily customize objects in the scene view.

  • Model tab

    Tools on the Model tab let you edit objects in the scene view.

  • Polygon tab

    Tools on the Polygon tab let you modify polygons in the scene view.

  • Deform tab

    Tools on the Deform tab let you deform objects in the scene view.

  • Texture tab

    Tools on the Texture tab let you texture objects in the scene view.

  • Rigging tab

    The Rigging tab contains tools for creating premade rigs.

  • Muscles tab

    The Muscles tab contains tools for creating muscles.

  • Characters tab

    Tools on the Character tab let you create characters in the scene view.

  • Constraints tab

    Tools on the Constraints tab create a constraint network where you can constrain objects to each other in the scene view.

  • Hair Utils tab

    Tools on the Hair Utils tab let you quickly set up hair and fur on objects.

  • Guide Process tab

    Tools on the Guide Process tab let you influence the placement and orientation of guide hairs by painting skin attributes.

  • Guide Brushes tab

    Tools on the Grooming tab let you add and directly manipulate hair.

  • Terrain FX shelf tab

  • Simple FX tab

    The Simple FX tab contains tools for creating dynamic simulations at the geometry level.

  • Cloud FX tab

    The Cloud FX tab contains tools for creating cloud effects.

  • Volume tab

    The Volume tab contains tools for creating volume effects.

  • Lights and Cameras tab

    Tools on the Lights and Cameras tab let you create and place lights and cameras in the scene view.

  • Collisions tab

    Tools on the Collisions tab let you create collision objects in the scene view.

  • Particles tab

    Tools on the Particles tab let you create dynamic particle simulations.

  • Grains tab

    The Grains tab contains tools for simulate grains of sand and other granular matter.

  • Vellum tab

    The Vellum tab contains tools for creating different types of vellum effects.

  • Rigid Bodies tab

    Tools on the Rigid Bodies tab let you create dynamic RBD objects in the scene view.

  • Particle Fluids tab

    Tools on the Particle Fluids tab let you create particle based liquids in the scene view.

  • Viscous Fluids tab

    Viscous fluids are FLIP simulations that use a temperature attribute to drive viscosity.

  • Oceans tab

    The Oceans tab contains tools for creating ocean simulations.

  • Fluid Containers tab

    The Fluid Containers tab contains tools for creating pyro, smoke, and liquid containers.

  • Populate Containers tab

    The Populate Containers tab contains tools for creating and removing fire, smoke, and liquid.

  • Container Tools tab

    The Container Tools tab contains tools for manipulating fire, smoke, and liquid.

  • Pyro FX tab

    Tools on the Pyro FX tab let you create simulated smoke and fire effects.

  • Sparse Pyro FX tab

    Tools on the Sparse Pyro FX tab let you create simulated smoke and fire effects.

  • Solid tab

    Tools on the Solid tab let you create and modify solid objects.

  • Wires tab

    Tools on the Wires tab let you create flexible dynamic objects in the scene view.

  • Crowds tab

    The Crowds tab contains tools for creating crowds, crowd behaviors, as well as examples.

  • Drive Simulation tab

    Tools on the Drive Simulation tab let you manipulate dynamic objects in the scene view.