The thermal step on the CPU reference (the GPU runs the same in MPMLava): lava particles scatter mass and
m·T into the grid (fixed point, as P2G), then each cools by
lavaCoolingRate with its exposure (from the fill) and ground contact, and relaxes towards the grid's
mass-weighted temperature at rate 4κ/Δx² (exact exponential, so any dt is stable). Writes ref.data.temperature.
The thermal step on the CPU reference (the GPU runs the same in MPMLava): lava particles scatter mass and m·T into the grid (fixed point, as P2G), then each cools by lavaCoolingRate with its exposure (from the fill) and ground contact, and relaxes towards the grid's mass-weighted temperature at rate 4κ/Δx² (exact exponential, so any
dtis stable). Writesref.data.temperature.