Houdini 20.5 Nodes Geometry nodes

MPM Container 1.0 geometry node

Defines the simulation resolution, start frame, and domain limits of a MPM simulation.

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Since 20.5

Overview

The MPM Container defines the resolution and start frame of the MPM simulation. For this reason, it must be known by all MPM nodes involved in the solve. The MPM Source, MPM Collider, and MPM Solver all have an input to be connected to this node. You can optionally add boundaries to the simulation container. By default the container is unbounded, but it can be useful to define some limits where material particles are bounced or deleted on contact.

Tip

You can optionally use node references to prevent the network from being cluttered with wires.

Inputs

Domain Geometry

Geometry to use as container.

Parameters

Start Frame

The frame that marks the start of the simulation.

Geometry Type

The type of geometry to define the simulation domain limits.

Axis-Aligned BBox

Uses the axis-aligned bounding box of the input geometry or the size and position defined in the Domain tab to define the container.

Convex Geometry

Uses the provided geometry as convex domain. This allows containers to not be axis aligned or even use the camera frustum to delete material points going outside of the camera view.

Note

Each polygon from the input will represent an infinite plane in 3d space, so high polygon counts could lead to poor performance. Using a static MPM Collider is recommended over complex domain shapes.

Tip

You can either set all the boundary walls to behave the same using the All parameter from the Boundaries tab or control each of the boundary planes individually by setting the boundtype string primitive attribute to opened closed, or delete.

Resolution

Particle Separation

The global particle separation used to drive the resolution of the whole simulation. This parameter is used by all MPM Sources and MPM Colliders that are not overriding it.

Grid Scale

Multiplies the Particle Separation to define the voxel width dx of the background grid. The default of 2 will pack 8 particles per voxel on average.

Domain

Size

Dimensions of the simulation domain.

Note

Since the MPM Solver is sparse, defining a domain size has no impact on the simulation if the boundaries are all set to opened, which is the default.

Center

Position of the simulation domain.

Friction

Amount of friction applied from the container walls to the material in contact.

Sticky

Allows projection of the material velocity even when moving away from the boundary walls. This prevents the material from detaching from the surface, making it sticky if friction is high enough. If the dot product between the boundary wall’s normal vector and the velocity of the material is smaller than this value, the velocity of the material gets projected onto the boundary walls.

Boundaries

All

Defines the collision response of the container boundaries all at once.

Opened

The material will ignore the boundaries.

Closed

The material will be bounced or stopped when hitting the boundaries.

Delete

The material will be deleted when hitting the boundaries.

+X

Defines the collision response of the positive X wall.

-X

Defines the collision response of the negative X wall.

+Y

Defines the collision response of the positive Y wall.

-Y

Defines the collision response of the negative Y wall.

+Z

Defines the collision response of the positive Z wall.

-Z

Defines the collision response of the negative Z wall.

See also

Geometry nodes