I'm using Houdini HDK, and trying to write my own advect node like below.
density->advect(velocity, timestep, nullptr, SIM_ADVECT_MIDPOINT, 1.0f);
However, when I set the velocity field to constant (0, -9.8, 0), the actual moving direction of smoke is upwards... When I use GAS_Advect node and GAS_Advect_Field node, the moving direction of smoke is downward, which is correct behavior.
So, I want to know why `SIM_ScalarField::advect()` didn't give the right result?
Looking forward to any help
