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There are several MPM Configure examples available through the tab menu. These are similar to shelf tools that put down networks of nodes for learning purposes. The MPM Configure Rolling Snowball example illustrates the use of the “chunky” Snow material type.
It puts down a simple network of nodes to simulate a snowball rolling down a slope.
Important nodes ¶
snowball
This is the MPM Source that uses the Snow material preset. The main differences are two parameter changes from the default. The Density has been increased to 900, to make sure that the snowball has enough weight to sink into the snow of the slope. Additionally, the Stiffness has been increased to 28, to make sure that the snowball does not collapse on itself and preserves its shape while it’s rolling down the slope. There is also some initial Velocity added to the snowball to push it down the hill.
snow_slope
This is another 
MPM Source, which uses the basic Snow material preset.
static_slope
This is the 
MPM Collider, which uses the default Static collider type.
mpmcontainer
This setup uses a default 
MPM Container, which defines the resolution of the simulation using the Particle Separation parameter, and can sets limits on whether particles should be deleted or bounce on contact with the boundary.
mpmsolver
This setup uses a default 
MPM Solver, which does the work of solving the scene.
build_sdf
The 
MPM Surface will generate a signed distance field (SDF) representation of the snow’s surface, which is required by multiple downstream tasks. Some Filtering options are used to make the surface smoother and more representative of the underlying material.
build_density
This MPM Surface will generate the density representation of the snow that is suitable for rendering. It takes the MPM particles as the first input to rasterize the points to a density grid and uses the precomputed SDF as a mask to clip some of the fuzzy details at the surface and add low frequency structures to the snow surface.
secondary_emission
This 
MPM Debris Source will generate the source points used to drive a secondary simulation to add high frequency details to the MPM simulation. Both Replicate Points parameters have been reduced to limit the amount of points to be emitted per frame.
secondary_sim
This 
DOP Network is a simple POP network using the SDF representation of the MPM simulation as a deforming collider.
build_secondaries_density
This MPM Surface will rasterize the secondary simulation to a density grid using the same resolution as the build_density node through an expression added to the Voxel Size parameter.
combine_vdbs
Both density VDBs are combined into a single VDB for efficient rendering.
Learning from this example ¶
| To... | Do this |
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Make the snowball break apart as it rolls down the hill |
Decrease the Stiffness parameters on the |