Variable viscosity

we don’t want to break the backward compatibility, and actually there is no need to do this. the old solver remains, and the new one is also able to export its content as grid. this gives us many advantages. first, the grid content can be compressed much better than the particles, second you can render it without having frost, using the tools that we already have.

couldnt age be a factor in viscosity?
if the viscosity is mappable, any value can be a factor. tn our grid based solver this is currently impossible.