Houdini 20.5 Nodes Geometry nodes

VDB Extrapolate geometry node

Extrapolate a VDB signed distance field.

Since 19.0

This node extrapolates signed distance fields stored as VDB volumes. Optionally, extrapolation can be masked with another VDB, so that new distances are computed only where the mask is active.

Parameters

Source Group

A subset of the input VDB scalar grid(s) to be processed in an operation involving Fast Sweeping.

See specifying volumes).

Extension Group

Arbitrary VDB fields picked up by this group will be extended off an iso-surface of a scalar VDB (fog/level set) as specified by the Source Group. This group is only used when the Operation parameter is set to Extend Field(s) Off Fog VDB or Extend Field(s) Off SDF.

Mask VDB

A VDB volume whose active voxels are to be used as a mask (see specifying volumes). This mask is only used when the Operation parameter is set to Expand SDF Into Mask SDF.

Operation

The operation to perform _Expand SDF Narrowband__

Dilates the narrowband of an existing signed distance field by a specified number of voxels.

Expand SDF Into Mask SDF

Expand/extrapolate an existing signed distance field into a mask.

Convert Fog VDB To SDF

Converts a scalar Fog volume into a signed distance grid. Active input voxels with scalar values above the given isoValue will have NEGATIVE distance values on output, i.e. they are assumed to be INSIDE the iso-surface.

Renormalize SDF

Given an existing approximate SDF it solves the Eikonal equation for all its active voxels. Active input voxels with a signed distance value above the given isoValue will have POSITIVE distance values on output, i.e. they are assumed to be OUTSIDE the iso-surface.

Extend Field(s) Off Fog VDB

Computes the extension of several attributes off a Fog volume. The attributes are defined by VDB grids that will be sampled on the iso-surface of a Fog volume (defined by the Source Group). The attributes are defined by the Extension Group parameter. This mode only uses the first Fog grid specified by the Source Group parameter.

Extend Field(s) Off SDF VDB

Computes the extension of several attributes off a signed distance field. The attributes are defined by VDB grids that will be sampled on the iso-surface of a SDF (defined by the Source Group). The attributes are defined by the Extension Group parameter. This mode only uses the first SDF grid specified by the Source Group parameter.

Domain Direction

Convert Fog To SDF or Renormalize SDF

Only works when Extend Field(s) of Scalar VDB is chosen. If checked, it will either convert a Fog Grid to an SDF or it will renormalize an SDF.

Use this option if one wants to convert the Fog grid specified by the Source Group to be an SDF or to renormalize an SDF.

Iterations

The desired number of iterations of the Fast Sweeping algorithm (one is often enough).

SDF Isovalue

Use this to define an implicit surface from the SDF volume.

Fog Isovalue

Use this to define an implicit surface from the Fog volume.

Ignore Active Tiles

Ignore active tiles in scalar field and mask VDBs.

This option should normally be disabled, but note that active tiles (sparsely represented regions of constant value) will in that case be densified, which could significantly increase memory usage.

Proper signed distance fields don’t have active tiles.

Dilation

The number of voxels by which to dilate the level set narrow band. Works with Expand SDF Narrowband mode of operation.

Dilation Pattern

The neighborhood pattern for the dilation operation.

Faces is fastest. Faces, Edges and Vertices is slowest. but can produce the best results for large dilations. Faces and Edges is intermediate in speed and quality.

See also

Geometry nodes