When Material Type is set to Metal, the surface is fractured using a Voronoi pattern. By default, Treat Geometry As is set to Surface, which performs thin shell fracturing and then extrudes the pieces to create thickness for simulation. If your input geometry is already modeled with thickness, you can change Treat Geometry As to Solid. In this mode, the geometry is fractured as a solid object, interior faces are created along the cuts, and the extrusion step is skipped.

To...	Do this
Control the number of metal pieces	Adjust Cell Points. You can drive the fracture using Density, specify a fixed Point Count, or provide custom input points.
Control the look of cut edges	Increase Noise Height to introduce irregular, torn-looking edges. A value of 0 produces straight cuts. You can also use Noise Element Size to control the scale of the noise pattern.
Prepare geometry for bending	Ensure the fracture produces pieces that are large enough to bend, but small enough to provide deformation detail.

The simulation runs on proxy geometry generated internally by the Metal material. The proxy geometry drives the simulation. Deformation is transferred back to the high-resolution geometry after the solve.

Each thin Voronoi piece is thickened using a PolyExtrude operation, and simplified using PolyReduce to keep simulation costs manageable.

The Constraints tab sets up glue constraints that hold the structure together until broken. After breaking, the system transitions to soft constraints. By default, soft constraints use Angular Plasticity, which allows the metal to bend and maintain its deformed shape instead of springing back.

Secondary Fracture subdivides each primary piece (Level 1) into smaller pieces (Level 2). This increases simulation resolution and improves the quality of bending deformation. Secondary fracturing applies only to the proxy geometry. It does not subdivide the high-resolution render mesh.

When using Secondary Fracture, deformation must be transferred correctly to the high-resolution geometry. In the RBD Deform Pieces SOP, turn on Match Proxy by Attribute and set Name Attribute to parentpiece. This option uses the parentpiece attribute created during secondary fracturing so that all Level 2 proxy pieces collectively deform their corresponding Level 1 high-resolution piece. Without Match Proxy by Attribute turned on, secondary fractured pieces will not correctly drive deformation.

The RBD Deform Pieces SOP transfers bending and tearing from the proxy simulation back to the high-resolution geometry. For smooth results, the high-resolution geometry must contain enough points to support the deformation. Low-resolution geometry will not deform well, even if the proxy simulation behaves correctly.

The Secondary Fracture tab has a Refine Geometry option with built-in methods for adding surface detail. This can be used to increase geometric resolution for deformation without manually modifying the original input mesh.

Tearing is achieved by allowing constraints to break in the Bullet Solver SOP. The primary fracture creates Level 1 pieces, and Secondary Fracture creates Level 2 pieces. Breaking constraints between the smaller Level 2 pieces can result in stretching or melting artifacts in the high-resolution geometry. Without Secondary Fracture, tearing produces larger, more rigid chunks with limited bending.

In the Bullet Solver Constraints tab, you can control which constraints are allowed to break by using the Group parameter. The constraints created by the Metal fracture include a constraint_tag attribute that identifies the fracture level. For example, to allow breaking only the primary (Level 1) constraints, you can set the0__ Group__ parameter to @constraint_tag=metal_fracture1. This limits breaking to the larger pieces and helps prevent stretching artifacts caused by breaking smaller secondary constraints.

• Use RBD Deform Pieces SOP to transfer deformation.

• Ensure sufficient high-resolution geometry for bending.

• Use Secondary Fracture for detailed deformation.

• Adjust Glue Strength and Stiffness for more immediate crumpling.

• Adjust PolyReduce settings to prevent proxy distortion.