Houdini 20.5 Nodes Geometry nodes

Lattice from Volume geometry node

Create a point cloud, connected polyline, tet or hex mesh around the active region of volumes. This node creates a deformation lattice for use with the Volume Deform node.

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Overview

This node is often used with the Volume Deform node and deformation nodes.

  • This node creates a lattice geometry from a volume or set of volumes.

  • You deform the lattice using deformation nodes such as Soft Transform and Bend.

  • The Volume Deform node automatically applies the equivalent deformations to the volume(s).

See the help for Volume Deform for more information.

Besides just creating a lattice for the Volume Deform node, this node can also be used alone to build a regular lattice of points in the shape of a VDB volume. This may be useful in advanced workflows as a representation of voxel data or as input to various solvers.

This node creates ix, iy, and iz integer point attributes on the lattice geometry, which together specify the 3D location of the original sample on the voxel grid.

It also creates a rest point attribute which records the point’s original position in space. The Volume Deform node compares the deformed lattice point positions to their “rest” positions and uses those transformations to deform the input volumes.

Tips and notes

  • The Volume Deform tool puts down both a Volume Deform node and a Lattice From Volume node, already wired together. You should use it when building a volume deform network.

  • Setting Output type to Points (the default) is fastest. Some deformer nodes cannot deal with unconnected points, and expect connected/polygonal geometry (for example, the Soft Transform SOP). To be able to use those types of nodes, set Output type to Polyline.

  • The tetrahedron and hexahedron output type are useful for creating regular meshes of those types that match the shape of a volume. Future deformers may support them as well.

Inputs

Volumes to Convert

The volumes you want to deform. This should come from the same output as the wire you connect to the Volume Deforrm node’s first input.

Optional Reference VDB

If you wire a VDB node into the second input, this node resamples the input volumes to the VDB’s voxel size before converting to a lattice.

Parameters

Group

Which volumes to convert into a point cloud. If this is blank it means all volumes in the first input.

Sampling

Whether to sample the volume at the corners (where voxel borders intersect), or in the center of each voxel.

Expand Active Region

Expand the active area by at least this number of voxels in each direction. Adding padding ensures the borders of a volume are properly captured.

Output Type

What kind of lattice to create.

Points

The fastest and light weight. However, some deformer nodes work best with connected points, for example, the Soft Transform SOP. In those cases Polyline is better.

Polyline

Create a two-point line between two points if they share a face in the volume. This creates an open cage. Tools that work with connectivity, like soft transform and attribute fill, are then able to understand the connectivity.

Tetrahedron

Each complete lattice element - ie, each place where the eight corner points are defined - is turned into a cube. These cubes are then converted to five tetrahedra. The regular mesh can then be used in solvers and other places that use tetrahedra.

Hexahedron

Each complete lattice element - ie, each place where the eight corner points are defined - is turned into a cube. These cubes are then converted to a single hexahedra, which is a primitive that represents a distorted cube.

Output Attributes from Volumes

Create attributes on the lattice points that sample the voxel values of the input volumes. In Center sampling these will correspond with voxel values. In Corner sampling, they will be an interpolation.

Examples

PigLattice Example for Lattice from Volume geometry node

This example demonstrates how to create a lattice around volumetric data.

See also

Geometry nodes