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The Break operation is used to induce a fracture line into the input geometry. The fracture can be determined by a grid, sphere, box, or custom configuration. The resulting pieces are disconnected, and a new inside group of faces is created.
The operator can be used to create a fractured object for RBD simulation, or to roughly separate geometry into disconnected, whole objects.
If you do not want to cut up your geometry manually, you can use the shatter tool to do it automatically for you.
Select the object you want to break.
Click the Break tool on the Model tab.
You can do this multiple times to create multiple breaks in a single geometry object.
By default, the Break tool will select connected primitives. If you want to select individual faces, right-click the component mode button on the left toolbar and turn off Select Connected Geometry.
If you want to simulate pieces breaking off of something else, for example rocks breaking off a cliff, you can use the extract tool to separate the static objects from dynamic objects.
If you do not want to use this tool with dynamics, you will need to append an Assemble SOP. Turning the object into an RBD Fracture Object or an RBD Glue Object will create the Assemble node for you.
If the inside faces created by the break operator contain any bad geometry (missing or extraneous faces), various parameters can be adjusted to try to eliminate it:
Increasing the resolution of the cutting surface will improve the detail of the insides surfaces.
Choose a new Seed value or Noise Type for the cutting surface deformation.
Enable Do Jitter and adjust the seed and amount values.
The group that will be broken by the operator.
Whether or not the outside part of the geometry will remain after the break occurs.
Whether or not the inside part of the geometry will remain after the break occurs.
Inside Group Name
The name assigned to the group of faces created on the interior of the broken geometry.
The Inside Group Name should be consistent over break operators applied to the same geometry, since it will be used by the Assemble operator to create the pieces of the object.
Visualize cut geometry by applying a random color to each piece.
The initial shape of the cutting surface before any deformation.
A flat plane surface.
A standard box shape with six sides.
A closed spherical surface.
The number of rows in the grid cutting plane.
The number of columns in the grid cutting plane.
The resolution of the box cutting surface.
The resolution of the sphere cutting surface.
The central position of the cutting plane.
The orientation of the cutting plane.
The scale of the cutting plane.
The maximum height of the deformations applied to the cutting plane.
Use a height of 0 for a perfectly flat (or perfectly spherical) cutting surface.
How rough or jagged the deformations of the cutting plane will be.
The number of fractal iterations performed when deforming the cutting plane.
The frequency of the deformations in the cutting plane, in each of the three dimensions.
A randomization seed for the deformations of the cutting plane.
Change this value to give your cutting surface a different set of deformations.
The type of surface deformation that will be applied to the cutting plane.
Standard noise which performs a 3 dimensional hermite spline interpolation on a lattice of random values.
Scatters points randomly through space and interpolates their values.
A variation of sparse convolution which gives higher frequency discontinuities.
This value is used to suppress potentially incorrect geometry. Any segments smaller than this value are deleted, and any gaps between segments smaller than the tolerance value are joined.
The default value is ideal for unit-sized geometry. However, if the geometry generated by the break has twigs or gaps, try tweaking this value.
Check for Full Enclosure
Enables a specific test to determine whether disconnected polygons are inside or outside the cutting surface.
Turn this option off when using open surfaces and on when using closed surfaces.
Assume Input is Closed
Enables an additional test of the inside/outside boundaries of the cutting surface.
Try turning this option on if the output pieces are being connected improperly.
Enables jitter on the cutting surface. Jitter causes small, random changes to the cutting plane during the break.
Jitter can be used to cause very fine changes in the output geometry.
Trying various jitter values can help to correct the output if the break generates any bad geometry in the inside faces.
Random number seed for jitter.
Amount of jitter
Scale of the jitter.
Polygons to Break
The polygonal geometry that will be cut by the cutting surface.
Optional Cutting Object
If geometry is wired into the second input it will be used as the cutting surface, overriding the Cutting Surface setting. The object will be translated, but not deformed.
The following examples include this node.
This example actually includes eight examples of ways that you can use voronoi fracturing in Houdini. In particular, it shows how you can use the Voronoi Fracture Solver and the Voronoi Fracture Configure Object nodes in your fracture simulations. Turn on the display flags for these examples one at a time to play the animation and dive down into each example to examine the setup.