With the release of Houdini 20.5, there comes an addition of a new solver. The MPM Solver simulates various materials in a multi-physics context.
Materials are defined using the MPM Source, while colliders come from the MPM Collider, both of which are connected to an MPM solver node.
One thing you might have noticed when using the MPM solver is that the output that it generates is a bunch of spheres. There is not much really that we can do with these spheres, and hence we need to use a point deform to conform the spheres to our original mesh.
To do this let's do a simple MPM simulation in Houdini -
To start I am going to drop down an MPM configure Jello Party in my geo1 context. The point deform technique will work with any kind of MPM simulation, so you can use another type of MPM configuration and the steps would still apply the same.
As we see, the output from the MPM solver is in the form of points that have spheres copied onto them. The simulation as it currently stands is unusable to render, we will need to deform our existing cube mesh to follow the animation of the MPM solver output.
2. Using a Point Deform - Drop down a retime, connect to the MPM solver output, and freeze the frame at 1.
Drop and connect a rest node to the retime node. It is imperative to store the position of the simulated mesh at rest on the first frame, we will need to feed this rest attribute to the point deform node so that it knows what the mesh looks like when it starts deforming.
Drop a point deform node and connect the rest nodes' output to the middle input (rest point lattice) of the pointdeform1 node.
3. Connect the output of the MPM solver to the third input (deformed point lattice) of pointdeform1.
Now connect the original cube geo to the first input (mesh to deform) of pointdeform1.
At this point, we have everything that we need, and now you should see the original mesh being deformed according to the solver output.
To increase the fidelity of the original geo, consider adding a remesh to increase the resolution of the original geo to see the finer details.
The final output should look something like this -
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