Pool buffers: position xyz (local to object), velocity xyz and w > 0 when alive; optionally a state with a tag in z,
and the solver's grid (w: node mass) with its resolution, which tells spray from bulk water.
Pool size.
The object the positions are local to.
cellSize sets the particle spacing (Δx/2).
OptionalresolutionGrid nodes along x, y, z (with buffers.grid).
What a FluidSurface draws: an
MPMSolver(or anything with its pool buffers).