The surfacing method used to create the initial VDB signed-distance field from the particles.

The distance between two particles in the fluid simulation. This parameter should generally reference the same parameter on the FLIP Object of the fluid simulation that created the particles.

The voxel side length to use for the generated VDB volume. This is a scale on the Particle separation length. For example, if Particle separation is 0.1 and Voxel size is 0.5, the side length of the voxels of the output field will be 0.05.

The maximum distance at which particles interact. Small increases can give smoother results but increase the cooking time and memory usage greatly. This is a scale on the Particle separation length. For example, if Particle separation is 0.1 and Influence radius is 3, particles will interact if they are within 0.6 units of each other.

The approximate desired distance between the particles and the generated surface. This is a scale on the Particle separation length, and must be smaller than the Influence scale. It becomes a scale on the pscale attribute value (instead of Particle separation length) if pscale is present.

You can use the pscale attribute to locally manipulate the distance of the surface to particles (pulling it closer or pushing it away). The pscale value replaces Particle Separation as the scale by which this parameter is multiplied to calculate the indented distance of each particle from the surface of the fluid.

You must ensure the Droplet Scale times pscale value of all particles is smaller than Influence Radius times Particle Separation.

When the checkbox is on, the node will only refine the geometry the specified number of times. When off, the node uses as many iterations as it needs to achieve a certain quality. Set this parameter from 1 to 4 to trade speed for quality.

The number of iterations chosen by the node is always finite, and the time taken by each iteration drops quickly as the number increases. So, there is little benefit to setting an explicit limit beyond 3 or 4.

Points with radius less than this number of voxels are ignored. You may need to reduce this parmater to get an output with lower settings for Voxel Scale.

Bubbles that are entirely submerged in the fluid could be lost while resampling the surface SDF. This option preserves bubbles in the generated surface by using a different sampling method. This option adds additional computation time and should only be activated when it is necessary to preserve internal geometry.

If the input fluid was compressed with the Fluid Compress SOP, use the compressed surface fluid VDB to fill in the deeper parts of the fluid below the particle detail.

When Union compressed fluid surface is on, this erodes the surface field to the compressed fluid’s particle bandwidth. If seams between the field and the particles are visible, you can decrease this value to remove them.

Specifies the output of the surfacing operation. The first three options are intended mostly for previews.

Create the surface where the computed surface volume equals this value. The default (0) creates the surface at the boundary between “any volume” and “no volume”. You can increase this value to expand the surface.

How much tolerance to allow when generating the surface. Higher values give fewer, larger polygons with a less precise match. Lower values give a denser mesh with a more precise match.

Copies the attributes in this list from the input points onto the generated surface.

For the attributes listed in Transfer attributes, this is the radius used for smoothing the sampled attribute values, as a multiplier on Particle Separation. Higher values will smooth out the attribute values more.

For the attributes listed in Transfer attributes, this is the number of points to sample when transferring particle attributes to the mesh. More samples give smoother attribute values, especially for velocities and motion blur if rendering with Geometry Velocity Blur.

Choose “Velocity” or “Vorticity” to visualize the values as surface colors in the viewer.

Expand the surface outward by the specified number of voxels. This filter will apply only to masked areas if its Mask parameter is enabled.

Smooth the surface using the specified filter for the number of iterations. This filter is applied after any dilation and will apply only to masked areas if its Mask parameter is enabled.

Reduce the surface inward by the specified number of voxels. This filter is applied after any smoothing and will apply only to masked areas if its Mask parameter is enabled.

Smooth the surface again using the specified filter for the number of iterations. This filter is applied after any erosion and will apply only to masked areas if its Mask parameter is enabled.

Generate a filter mask from the fluid velocity, where surface areas with velocity below the minimum speed get full filtering, while areas above the maximum speed get none.

Generate a filter mask from the fluid vorticity, where surface areas with vorticity below the minimum speed get full filtering, while areas above the maximum vorticity get none.

Generate a filter mask within the specified world-space offset of any collision objects or volumes connected to the second input.

Use volumes in the geometry connected to this node’s third input (“Mask volumes”) to mask the filters.

If you specify multiple mask fields (for example, turning on Velocity range and Vorticity range, or specifying multiple mask volumes in the Mask input field), the node uses this operation to combine them.

Smooth the combined filter mask before using it to mask any surface filtering. Note this parameter is for smoothing the mask volume. It is not about masking the smooth filter.

Restrict the mask to allow filtering only within the specified voxel bandwidth from the original raw surface generated from the particles.

Visualize the amount of masking as surface colors in the viewer.

The parameters above will be enabled if Visualize Mask is on, so it can be quicker to modify the masking parameters while visualized, but before being applied to any of the above filters with their Mask parameter.

This node represents the regions internally as VDB volumes, with a base resolution of Particle Separation multiplied by Voxel Scale. This is a multiplier on the scale of the voxels in the region volumes. Increasing the scale makes the regions faster to compute but makes clipping less precise. Lowering the scale is slower but more precise. Do not decrease this value below 1.

When this option is enabled, the node does not generate surface inside geometry or volumes from this node’s second input (“Collision objects and volumes”).

Expand the subtracted area beyond the input geometry by this many Houdini units.

Only generate the surface inside a bounding box.

When this parameter is on, you can use the Handles tool in the viewer to size and position the bounding box.

The size of the bounding box.

The center of the bounding box.

Create walls at the boundaries of the box to enclose the surface. When this is off, the node simply clips the surface at the boundaries and leaves the surface open.

Flatten the edges of the surface to make it easy to match the edges of the simulated fluid with a surrounding ocean surface. This operation works best with a mesh that is already fairly close to flat. It can generate overlapping polygons if the fluid has splashes and waves at the boundaries. Turn on Rebuild SDF to help ensure smooth surfaces around the edges.

Rebuild the VDB signed-distance field after flattening, which can remove artifacts from flattening splashes around the boundary and provide a smoother final mesh.

Output a flattened point attribute on the polygonal geometry that indicates how far the point lies within the Flatten Distance to the boundary, normalized from zero to one. This attribute can be used to scale procedural displacement shading to apply only on the flattened part of the fluid.

Do not flatten the fluid near any collision geometry or volumes (see Subtract collision volumes above). This option helps avoid flattening the bottom of a fluid when there is a collision object representing the bottom of the fluid domain, such as a riverbed.

The distance from any collision input at which to suppress flattening if Suppress Near Collisions is enabled, specified as multiples of the Particle Separation.

The plane across which to flatten.

The shape of the tapering from the edges. “Rectangle” gives you a dilating rectangle with corners, “Circle” gives you a dilating circle.

The “resting” ocean level to flatten to at the edges.

The surface is smoothly scaled down from this maximum height at Flatten distance from the edges, to the Water level at the edges.

The fluid will be flattened to this distance within the flattening region with a smooth falloff.

Extend the flattening plane this far outside the bounding box. This padding will affect both polygonal and volume outputs. For large scale extension of the mesh, use the Extrude Polygons option.

Extrude the polygons at the edge of the mesh outwards to create a large plane with the liquid surface in the middle. This can be useful to generate a large, flat ocean surface with the simulated surface in the middle, and then apply ocean displacements to the entire thing. This is only available when Closed boundaries is off and Pad bounds is on.

The distance to extrude the mesh boundary polygons in all horizontal directions.

The number of polygonal divisions in the extruded geometry.

Clip the fluid surface to the specified camera’s frustum.

If the points are from a packed geometry and the node loading the points has Delay load geometry turned on, only the visible particles will be loaded from disk.

The distance from the camera to start the clip region.

The distance from the camera to stop the clip region.

If set, use the camera’s window scale, offset, and crop parameters in addition to the following Window X/Y settings.

The min/max portions of the camera’s view to fill with the clip region. This allows you to add padding to ensure good boundary conditions or focus into a key area of the scene.

Create closed walls at the boundaries of the frustum. Otherwise the surface will be clipped at the boundaries.