MPM Debris Source geometry node

Extracts points of potential emission for secondary simulations derived from a primary MPM simulation.

On this page	Overview Inputs Parameters Prune Points Replicate Points Stretching Based Speed Based Attribute Edits
Since	21.0

Overview ¶

The MPM Debris Source extracts points of potential emission for secondary simulations derived from a primary MPM simulation. It detects material stretch and creates source points where the material is breaking to emit secondary simulations such as debris. The output of this node will usually be passed to a POP Solver to perform the secondary simulation using an SDF representation of the MPM simulation as a collider.

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

Inputs ¶

MPM Particles

The output of the MPM Solver.

MPM Surface and Vel

A VDB representation of the primary MPM simulation to act as a collider. This could be the output of the MPM Surface.

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.

Time Scale

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

Only Emit on Integer Frames

Prevent particles from being emitted on substeps.

Prune Points ¶

Min Stretching

The minimum stretching variation (time derivative of Jp) a particle must reach for it to be selected as potential emission.

Min Speed

The minimum speed at which a particle should be traveling for it to be selected as potential emission.

Max Dist to Surface

The maximum distance a point can be from the MPM surface for it to be selected as potential emission. This parameter is a multiplier on the particle separation__ of the MPM simulation, so it does not require adjustments when you change the scale of your scene.

Ratio to Keep

The proportion of points to keep for emission.

Replicate Points ¶

Stretching Based ¶

Points per Point

Scales the point replication based on the points' stretching variation (time derivative of Jp).

Remap Stretching

Remap the points' stretching variation before it is used to drive the point replication.

Input stretching variation range.

Out

Output stretching variation range.

Speed Based ¶

Points per Point

Scales the point replication based on the points' speed.

Remap Speed

Remap the points' speed before it is used to drive the point replication.

Input speed range.

Out

Output speed range.

Spread Points Along Velocity

Distribute the emission points along the velocity vector to cover the distance traveled between two frames. This ensures no stepping artifacts will be visible during the simulation.

Attribute Edits ¶

Attributes to Delete

Delete point attributes that are no longer required to minimize the footprint of the point cloud in memory and on disk.

Particle Scale

Scale the pscale attribute of the secondary points such that they are smaller than the MPM points. This will add high frequency details when combined with the primary MPM simulation.

Initialize Random Orient

Generate a random orient point attribute on the output points so that geometry can be instanced on them more naturally.