Houdini 21.0 Nodes Geometry nodes

MPM Post-Fracture geometry node

Fractures the renderable geometry represented in a MPM simulation using the final state of the simulation.

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Since 21.0

Overview

The MPM Post-Fracture fractures the renderable geometry represented in an MPM simulation using the final frame of the simulation. It attempts to fracture the geometry exactly where things are breaking or bending so that the renderable geometry can accurately capture the dynamics of the MPM simulation while preserving all of its original attributes.

For more information, see the Destruction help page in the MPM Chapter.

Warning

The deformation gradient F needs to be cached for the destruction workflow. It is not by default. You must turn on the Deformation Gradient (F) checkbox on the Output tab of the MPM Solver.

Inputs

Geometry to Fracture

MPM Particles

Parameters

Start Frame

Manually define the start frame of the MPM simulation. The start frame usually comes as a detail attribute on the MPM particles.

End Frame

Define the end frame of the MPM simulation.

Fracture Namespace

Adds a prefix to the name of each input piece. This can be useful for avoiding duplicate piece names or grouping the new pieces that are created.

Cutter Method

The algorithm to use to perform the fracturing step.

Boolean

Supports detailed cutting geometry to add interior and edge details to the fractures. Can be less robust in the presence of bad geometry.

Voronoi

Only supports clean voronoi cells with no interior or edge details. Can be more robust in the presence of bad geometry.

Perform Fracture

Disables the fracturing step. This allows you to interactively play with the parameters of the node while looking at the guide geometries to estimate how things are going to be fractured. When the parameters are roughly in the right spot, this toggle can be turned back on to fine tune the fractures.

Tip

If you forget this toggle off, the MPM Deform Pieces will throw an error and complain about the geometry not being fractured.

Output Input Geometry

Outputs the input geometry to see the guides in context.

Geometry Type

The type of geometry to fracture.

Solid

Closed geometry where interior faces will be generated.

Surface

Single sided geometry where no interior faces will be generated.

Global Scale

Scales all scene scale dependent parameters in one go. This allows you to quickly adjust the node to a different scene scale without having to touch multiple parameters.

Pieces Selection

Show Guides

Display the pieces that will be candidates for fracturing. The pieces that will be fractured are green while the others are red.

Min Length

The minimum length for a piece to be considered as a candidate for fracturing.

Fracture Points

Show Guides

Display the points that will be used as fracture centroids.

Fuse Distance

The minimum point separation of the centroids used for fracturing. This prevents tiny pieces from being created.

MPM Points

Min Stretching

The minimum stretching amount for the point to be considered breaking.

Align Fractures to Stretch Points

Use the points that are immediate neighbors to the points selected by stretch thresholding as piece centroid. This improves the alignment between the geometry fractures and the MPM fractures.

Filler Points

Point Separation

The point separation of the filler points. These points are only there to allow the geometry to bend gracefully and prevent very elongated pieces from being generated, which could cause artifacts when transformed rigidly.

Max Distance

Only create filler points within this distance of the selected MPM Points.

Cutter Geometry

Show Guides

Display the cutting geometry that will be used for fracturing. This is useful to inspect the interior and edge details.

Add Interior Details

Add Interior Details

Enables interior and edges details to be generated. This operation can be time consuming and should only be enabled when you are satisfied with the rest of the parameters.

Mesh Target Size

Determines the target edge length of the triangle mesh.

Noise Element Size

The size of the noise pattern.

Noise Amplitude

The amplitude of the noise pattern.

Tip

This node has a dive target that allows you to edit the cutting geometry before performing the fracturing step. This gives you more control over the interior details of the fractured geometry.

See also

Geometry nodes