Houdini 20.5 Nodes Geometry nodes

Joint Capture Biharmonic geometry node

Captures skin geometry to a SOP skeleton for use with Joint Deform.

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Since 19.0

This node creates capture weights on geometry that is to be deformed by the Joint Deform SOP. It provides a high-level setup for using the Bone Capture Biharmonic SOP by internally building the required tetrahedral mesh.

Note

This node uses Intel’s Math Kernel Library when run on x86 processors. You can use an environment variable to tune the library for speed or for producing identical results from run to run.

Parameters

Skin Group

Optional point group from the first input for computing capture weights. By default, all points are used.

Skeleton Group

Optional point group from the second input used to compute capture weights. By default, all points are used.

Max Iterations

The maximum number of iterations when solving for the weights. Using a large number of max iterations will allow the solver to converge to a higher quality solution at the expense of speed. Since biharmonic functions for capture weights do not usually need to be very precise, a low number of max iterations often produces suitable results.

Tet Method

Tetrahedralization method. The choices here trade quality and speed depending on the skin geometry.

Adaptive

Creates a tetrahedral mesh from an adaptively remeshed version of the skin geometry. This method offers a good trade off between performance and accuracy. It will almost always produce a tetrahedralization that faithfully matches the surface of the input, but can give unnecessary detail to certain areas.

Uniform

Creates a tetrahedral mesh from a uniformly remeshed version of the skin geometry. This method can be faster than Adaptive at the loss of accuracy. More useful when the amount of detail in the skin geometry that you want to capture is fairly even.

Exact

Creates a tetrahedral mesh whose surface polygons matches the skin geometry exactly. This is the most precise method but is usually the slowest. This method is best for avoiding accidental weight leakage in tight areas like in between fingers.

Embed

Creates a tetrahedral mesh whose surface polygons only approximately match the skin geometry while giving an even distribution of tet sizes. This uses the Tet Embed SOP which was the default method used in the Object level Capture Geometry shelf tool. While this method is slower than Uniform, it can guarantee that the resulting tetrahedral mesh fully encloses the skin geometry when Enlarge Offset is set to 1 or more. Therefore it can provide higher quality surface capture weights while being slower at generating the tetrahedral mesh. It can also be useful for capturing certain 2D surfaces, like a flat grid, by giving it a thickness.

Scale Attribute

When turned on, uses the specified float point attribute to control the size of tets at particular areas on the skin geometry. This can be created from the Attribute Paint SOP for fine control over where capture weights should be computed more precisely.

This is only available when Tet Method is set to Adaptive.

Uniform Scale

Controls the size of the triangles when remeshing the skin geometry. This is only available when Tet Method is set to Uniform.

Enlarge Offset

When enabled, this enlarges the tethedral mesh by the given the number of tet layers.

This is only available when Tet Method is set to Embed.

Max Tet Scale

Controls the maximum size of individual generated tets. The higher the value, the larger the tetrahedra in the interior of the tetrahedral mesh are allowed to be (less interior detail).

Max Triangle Scale

Controls the maximum size of the triangles on the surface of the tetrahedral mesh. The higher the value, the larger the triangles on the tet mesh boundary will be (less surface detail).

This is only available when Tet Method is set to Adaptive.

Min Triangle Scale

Controls the minimum size of the triangles on the surface of the tetrahedral mesh. The higher the value, the larger the triangles on the tet mesh boundary will be (less surface detail).

This is not available when Tet Method is set to Exact.

Do Blend

Enable blending of the result with the existing capture weights from the skin geometry input.

Blend Factor

When turned on, this is the blend factor used to blend the result with the input capture weights.

Skeleton Resample Options

Resample Segments

Specifies how the lines should be resampled.

Off

No resampling.

By Max Axis Fraction

Resample using a maximum segment length derived from Max Axis Fraction multiplied by the largest axis of the lines' bounding box.

By Max Segment Length

Resample using the Max Segment Length value.

Max Axis Fraction

The fraction of the largest axis of the lines' bounding box side to use for resampling. This is only used when Resample Segments is set to Max Axis Fraction.

Max Segment Length

When when Resample Segments is set to Max Segment Length, this specifies the maximum line segment length to resample with.

Exclude Short Bones

When enabled, bones whose lengths are equal or less than Exclude Threshold will be ignored.

Exclude Threshold

When Exclude Short Bones is enabled, bones whose lengths are equal or less than this value are ignored.

Fuse Threshold

The threshold at which points will be fused in the output. A tolerance is computed from this value by multiplying it with the maximum bounding box axis size. Points whose positions are equal or less than the tolerance will be fused into a single point.

Capture Geo Options

Use Capture Geo

When turned on, the attached joint geometry of the Capture Pose input is used as influence objects for the biharmonic solve. The points of the geometry attached to a specific joint will strengthen the influence of the given joint in that region of the geometry to be captured.

Capture Geo Role

Defines the function within the rig setup of the attached geometry.

Control

The attached geometry is used as control geometry that eases the joint selection for viewport interactions with the skeleton.

Capture Geo

The attached geometry is used to manipulate the result of the Joint Capture Biharmonic SOP. The points of the geometry attached to a specific joint strengthen the influence of the given joint in that region of the geometry to be captured.

Inputs

Rest Geometry

The geometry to capture. It must be closed.

Capture Pose

The SOP skeleton to capture the Rest Geometry input to.

Animated Pose

The SOP skeleton intended for deforming the skin geometry. It is provided for wiring convenience since this input is merely passed through to the corresponding output.

Outputs

Rest Geometry

The skin geometry with capture attributes created as the boneCapture point attribute.

Capture Pose

Provided for wiring convenience, it is identical to the second input.

Animated Pose

Provided for wiring convenience, it is identical to the third input.

Attributes

boneCapture

Attribute added in the Rest Geometry output that defines the skinning weights for the deformation, ready for use with the Joint Deform SOP.
See also

Geometry nodes