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This node demonstrates a good network for doing a fracture/crumble simulation in LOPs. It ensures the simulated geometry is placed in the same hierarchy it originated from or below, so as to preserve material bindings and other primvar inheritance.
You can dive into the SOP network inside this node to see how the effect works and how it is exported to the parent network as USD. You can use this node as a starting point for doing more elaborate simulations in LOPs.
A space separated list of USD geometry prims to fracture.
What frame to grab the destruction geometry at. The default is
$RFSTART, the fractional first frame of the current frame range.
A space separated list of USD geometry prims that the fractured geometry can collide with.
What frame to grab the collision geometry at. The default is
$FF, the current fractional frame number, allowing the collision geometry to be animated.
What type of prim(s) to create in the USD to represent the fractured pieces.
Create individual USD geometry prims for each fractured piece as children of the original USD geometry. Transforms are authored as animated attributes on their parent XForm prim while the mesh topology itself remains static. This yields the best results for disk space consumption and motion blur.
Create USD instances referencing the fractured geometry.
Create a USD point instancer node that copies the fractured geometry onto points representing the position/rotation of each piece.
Replace the USD geometry prims with a deforming representation of the fractured mesh where the mesh deforms at each timestep to depict the simulated pieces.
When Output Type is Point Instancer, create the point instancer prim at this path.
Create Simulation Proxy
When fracturing the geometry, this node can author the proxy geometry as
simproxy geometry, a more lightweight representation of the high resolution render geometry. This can be used by other tools such as the Edit LOP for better performance when using Edit’s physics-based layout option.
Block Geometry Properties
When Output Type is Transforms or Native Instances, the node puts the fractured geometry in child prims under the original USD geometry prims. Without this option, the original source geometry will still exist in the scene with the fractured pieces. Turn this on to author blocks on the geometry properties of the original prims to hide the source geometry.
Bind Geometry Subset Materials
When fracturing geometry, this node creates geometry subsets containing the newly exposed “internal” faces of the fractured geometry. Turn this on to bind the materials from the original source primitives to these geometry subsets.
The frame at which to create the output. The default is
$FF, the current fractional frame number.