Houdini 21.0 Nodes Geometry nodes

RBD Material Fracture geometry node

Fractures the input geometry based on a material type.

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Since 17.0

Overview

This node allows you to accurately fracture geometry based on a specific type of material. Currently concrete, glass panels, and wood are supported.

It accepts four inputs: geometry, constraint geometry, proxy geometry, and an optional input for extra points to control the fracturing process. It will fracture the incoming geometry using different fracturing method depending on the material specified in the Material Type parameter. If an input constraint geometry is specified, it will update the constraints for the fractured pieces.

See fracturing objects for simulation for a guide to fracturing workflows and tools in Houdini.

Using different displays

The Guide Geometry parameter on the RBD Material Fracture node will allow you to switch between different displays. All materials have Fractured Geometry, which will display the group being fractured.

They also all have Constraint Network, which will display the internal constraint network of all fractured pieces.

There are two concrete-specific displays: Primary Volume and Edge Detail. These views allow you to display the volume distribution for each primary fracture level used for scattering and display the boolean cutting planes used to generate the edge detail.

There are also two glass-specific displays: Concentric Noise and Edge Detail. These views allow you to display the noise used for determining the discontinuity for concentric cracks and display the magnitude distribution of the edge noise.

The three wood-specific displays allow you to display the cutting planes for grains, cuts, and splinters.

Working with concrete

  • The Fracture Level will control how many cuts your object will have. Increasing this number will add more fractures to the existing fractured pieces, breaking each chunk into smaller pieces.

  • Turning on Edge Detail will add more noise to the cuts.

  • Use the RBD Paint node to interactively paint weaker areas on the geometry in the viewport before the RBD Material Fracture node. This will paint a density attribute in the areas you want more fracturing to occur.

    Note

    Choose Scatter From Attribute on the RBD Material Fracture node and specify density as the Attribute Name.

Working with glass

Note

This is meant to be used for glass panels (flat objects). Curved glass isn’t currently supported.

  • Fracture per Piece is extremely useful when working with different panes of glass. It allows you to loop through each piece in the input geometry and fracture them individually.

  • The parameters on the Cracks tab are useful for determining how many cracks you want the glass to have.

  • Enable Chipping on the Chipping tab will give your simulation more details, as it will chip the corners of the broken glass as it breaks apart.

Working with wood

  • By default, the fracture direction of wood is determined by its longest point.

  • To determine the amount of fracturing, you can edit the Cut Spacing parameters to give the wood more or less cuts.

  • Use the controls on the Cluster tab to stick fractured pieces together into larger chunks that won’t break apart. This will give your simulations more variation in shapes and sizes.

Parameters

Group

The geometry to be fractured. If no group is specified, the full input geometry will be fractured.

Material Type

The type of material of the incoming geometry.

Concrete

Concrete material type.

Glass

Glass material type. Only flat glass panel is currently supported.

Wood

Wood material type.

Fracture Namespace

Adds a namespace prefix to the name of each piece. This is useful for avoiding duplicated piece name or isolating a group of constraints.

Fracture per Piece

Loop through each piece in the input geometry and fracture them individually. If the Piece Attribute is not found, it will fracture based on connectivity.

Piece Attribute

The primitive attribute that defines each piece for partitioning.

Single Pass

Fractures a specific piece at the given index. This can be useful for debugging and testing using a single piece.

Random Seed

Seed used when adding random variation of the parameters for each piece.

Reset Cached Pass

Reset the currently cached display in the for loop. Use this to update the guide geometry if it is not displaying the current geometry.

Concrete

Guide Geometry

None

No guide geometry.

Fractured Geometry

The group that is currently being fractured will be highlighted.

Primary Volume

Display the volume distribution for each primary fracture level used for scattering.

Edge Detail

Display the cutting planes used to generate the edge detail.

Constraint Network

Display the constraint network of all pieces.

Primary Fracture

Enable Fracture

Turning this off will bypass this fracture level.

Fracture Level

The number of levels of recursive fracturing to perform.

Fracture ID

The fracture ID for this fracture level. The output attributes and groups associated with this fracture level will have this tag.

Fracture Ratio

The ratio out of all the pieces from the previous level to fracture at this level.

Scatter From

Volume

Scatter points based on the fog volume generated.

Attribute

Scatter points based on the specified point attribute in the incoming geometry. For example, the RBD Paint SOP can be used to paint a density attribute on the geometry.

Attribute Name

The name of the point attribute to use as a density attribute when scattering points.

Scatter Points

The number of points to scatter.

Scatter Seed

The random seed for scattering points.

Use Input Points

Use additional Voronoi cell points from the fourth input.

Input Points

Specifies a group of points from the fourth input geometry to use for Voronoi cells.

Volume Resolution

The resolution of the fog volume. The higher the resolution, the slower the fracturing time will be. Smaller geometry will require higher volume resolution.

Noise Frequency

The frequency of the noise. Higher values give smaller scaled details in the noise.

Noise Offset

The offset of the input into the noise function. If you visualize the noise as a 2D graph or 3D height field, this has the effect of “panning” across the space of possible noise outputs. If you have the general noise effect you want but just want to get a different set of values for a different look, try changing the offset.

Cutoff Density

The low density level to cutoff at. Density below this value will be discarded.

Chipping

Enable Chipping

Break off corners of pieces to create chips.

Overall Ratio

The overall ratio out of all the pieces to perform chipping.

Overall Seed

The overall seed for the ratio of fracturing.

Detail

Detail Size

The size of the polygons added for the edge and interior detail.

Edge Detail

Use Boolean to obtain edge detail.

Detriangulate

Convert geometry back to N-gons after applying boolean. Turning this off can sometime make the result more stable.

Interior Detail

Add noise to the interior points, scaled based on their distance to the surface.

Depth Volume Voxel Size

The size in world space of the voxels in the SDF used for depth sampling.

Noise Amplitude

Scales the amount of displacement.

Noise Type

The type of noise added to the interior points.

Frequency

The frequency of the noise. Higher values give smaller scaled details in the noise.

Offset

The offset of the input into the noise function. If you visualize the noise as a 2D graph or 3D height field, this has the effect of “panning” across the space of possible noise outputs. If you have the general noise effect you want but just want to get a different set of values for a different look, try changing the offset.

Constraints

Apply Constraint Properties

Apply constraint properties to the output constraint geometry. The RBD Constraint Properties SOP can be used for advanced constraint setups.

Glue Constraint Name

Primary Strength

The starting strength of the glue bonds of primary fracture.

Level Multiplier

The number to multiply the primary strength with for each increment of fracture level.

Chipping Strength

The strength of glue bonds of corner chips.

Strength Variance

Randomly varies the strength of each glue bond.

Switch to Soft Constraint when Broken

Specifies a different constraint type to switch to if the glue constraint is broken by the Bullet Solver.

Note

This parameter does not set attributes directly but determines which parameters are relevant to streamline the UI.

Soft Constraint Name

Degrees of Freedom

Specifies whether the constraint affects position, orientation, or both. This does not apply to glue constraints, which work by simulating glued chunks together as a single object with a compound collision shape.

Glass

Guide Geometry

None

No guide geometry.

Fractured Geometry

The group that is currently being fractured will be highlighted.

Concentric Noise

Display the noise used for determining the discontinuity for concentric cracks.

Edge Noise

Display the magnitude distribution of the edge noise.

Constraint Network

Display the constraint network.

Impact Points

Use Scatter

Use randomly scattered points on the surface as impact points.

Use Input Points

Use points from the fourth input as additional impact points.

Input Points

The group of points from the fourth input to use as impact points.

Cracks

Radial Crack Number

The number of radial cracks to generate for each impact point.

Number Variance

The variance in the number of radial cracks for each piece.

Number Seed

The seed for the variance of the number of radial cracks.

Minimum Width

The minimum width between each concentric crack going outward radially.

Impact Spread

How far from the origin(s) the concentric cracks spread.

Discontinuity Freq

The frequency of the discontinuity noise for concentric cracks.

Discontinuity Size

The amplitude of the discontinuity noise for concentric cracks.

Chipping

Overall Ratio

The overall ratio out of all the pieces to perform chipping.

Overall Seed

The overall seed for the ratio of fracturing.

Corner Ratio

The ratio of corners in a piece that are chipped off.

Detail

Detail Size

The size of the polygons to add for the edge noise.

Enable Edge Noise

Add noise to the cracks.

Fade From Origin

How far to fade off the edge noising from the fracture origins.

Fade From Border

How far to fade off the edge noising from the borders of the glass.

Use Convex Decomposition

Create proxy geometry from the high-resolution pieces using a convex decomposition.

Max Concavity

The maximum distance from a point on the geometry to it’s closest convex hull edge. Reducing this value will produce convex hulls that are a closer fit to the input geometry, but the geometry may be split into more segments.

Constraints

Radial Strength

The strength of the glue bonds between radial cracks.

Concentric Strength

The strength of the glue bonds between concentric cracks.

Chipping Strength

The strength of the glue bonds for corner chips.

Wood

Guide Geometry

None

No guide geometry.

Fractured Geometry

The group that is currently being fractured will be highlighted.

Grains

Display the cutting planes for the grains.

Cuts

Display the cutting planes for the cuts.

Splinters

Display the cutting planes for the splinters.

Constraint Network

Display the constraint network.

Grain

Fracture Direction

The direction of fracturing.

Auto (Bounding Box)

Determine the direction automatically based on the oriented bounding box.

Vector

Use the vector specified as the direction of fracturing.

Grain Spacing

The spacing between grain lines.

Grain Offset

The size of offset randomly applied to each grain line.

Grain Offset Seed

The seed of the random offset.

Height

Displacement amount of the height.

Element Size

Distance between peaks of lowest frequency noise.

Grain Detail Size

The size of polygons used to cut the grain lines.

Cut

Cut Spacing

The spacing between cuts.

Cut Offset

The size of offset randomly applied to each cut.

Cut Offset Seed

The seed of the random offset.

Splinter Density

The amount of splinters for each cut.

Splinter Length

The length of the splinters.

Detail

Use Convex Decomposition

Create proxy geometry from the high-resolution pieces using a convex decomposition.

Max Concavity

The maximum distance from a point on the geometry to it’s closest convex hull edge. Reducing this value will produce convex hulls that are a closer fit to the input geometry, but the geometry may be split into more segments.

Cluster

Cluster Type

Specifies how to apply the clustering to the input geometry.

Combine Pieces

Adjusts the name primitive attribute to combine pieces into clusters. This will result in fewer objects in the simulation. The constraint geometry is also updated to reflect the new pieces.

Group Constraints

The input geometry is not modified, but primitive groups are added to the constraint geometry to identify constraints between clusters, internal constraints in a cluster, etc. This can be used with the RBD Constraint Properties SOP to, for example, create stronger constraints between pieces in the same cluster. With this approach, the clustered chunks may be broken apart during the simulation by breaking the constraints within a cluster.

Offset

The offset of the cellular noise added to the input points.

Jitter

The jitter of the cellular noise added to the input points.

Size

The size of the cells for the noise added to the input points. This roughly corresponds to the size of the clusters.

Random Detachment

Randomly detach pieces from clusters.

Detach Ratio

The probability that a particular piece will be detached.

Detach Seed

The random seed used for detachment.

Constraints

Grain Strength

The strength of glue bonds between grains.

Cut Strength

The strength of glue bonds between cuts and splinters.

See also

Geometry nodes