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MPM ¶
MPM stands for material point method and is an extension of the FLIP Solver to solid mechanics. It allows the simulation of multiple materials such as snow, soil, mud, concrete, metal, jello, rubber, water, honey, and sand. The implementation is based on OpenCL to leverage the powerful GPUs present in most machines. The background grid uses NanoVDB, which is sparse by default.
MPM makes dynamic fracturing realistic and easy, but everything can eventually break. It can use multiphysics (provided all things are MPM), and is really good at simulating clumpy/chunky materials. It uses a -SOP-based workflow, with the option of user defined forces with a dive target. The typical node tree is made up of the following parts. You can use the tab menu to put down an MPM Configure for an example of a simple setup.
Defines the material points to be injected in the MPM simulation. This node creates points and sets material point attributes that can be manipulated to add variation on a per-point basis before going into the 
MPM Solver. It expects a mesh or volume as input, and fills the object with particles holding the material attributes. Many MPM Sources can be merged together before they are passed to the MPM Solver.
Defines colliders to be used in the simulation. Only VDB colliders are supported. This node can create the VDB representation from a mesh or be provided with a VDB directly. Three types of colliders are supported: static, transformed, and deforming. Many MPM Colliders can be merged together before they are passed to the MPM Solver.
MPM ContainerDefines 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.
Does the actual work of solving the scene based on the sources and colliders passed to its first and second inputs respectively. It can simulate many material types in a multi-physic context. MPM is an extension of FLIP to solid mechanics that was first introduced to graphics to simulate snow. It is particularly efficient at solving elastoplastic “chunky” materials where large chunks are expected to stick together, such as snow and soil. It is also possible to simulate complex interactions like water carrying large chunks of soil or concrete.
Note
Although MPM is in SOPs, you need DOP level permissions to use it. This means that MPM is available in Houdini FX, Houdini Apprentice, Houdini Indie, and Houdini Education. It is not available in Houdini Core.
MPM materials ¶
Other dynamics ¶
The 
POP Curve Incompressible Flow node computes an incompressible velocity field, given velocities, angular velocities, or both, along the control curve and sets the velocity and the angular velocity for the particles.