In this tab, you can control all the settings that drive the look of your sim.
Controls are separated into two sections. At the top, you have a list of sliders and toggles that let you enable and change the strength of the various settings.
Below you have extra settings tabs for each of the settings. Some settings are simple enough that all they need is a strength slider. Some are more advanced and have many additional options.
What algorithm to use when particle velocities are converted to grid velocities and then back to particle velocities. Velocities need to be converted to grids because the way Paradigm and most solvers preserve the incompressibility of a fluid only work on grids.
Simply copies the grid velocity to the particles. This makes the particles velocity very smooth as it completely replaces any uniqueness the particle velocities had before as the velocities were effectively averaged when converted to grids.
Copies back only the differences in the grid velocities before and after project non-divergent. This allows for more particle uniqueness in their velocities. You may sometime see this referred to as “splashiness” in other solvers and tools. There is a blend parameters that allows for some of the pure sampled velocity value to be mixed in as full FLIP does appear very noisy when used at full strength.
To prevent the particles from collapsing in on themselves project non-divergent tries to maintain velocities that would prevent this but that traditionally requires higher iterations that are expensive and even then it’s imperfect and uses re-seeding to maintain an even particle spread.
Paradigm instead borrows concepts from SPH to try and maintain an even spread without expensive project-non divergent iterations and re-seeding. It can be thought of as a hybrid solver.
Artificially adds divergence to regions where particles start to collapse so that the project non-divergent step will create velocities that later separate them during advection. This is sometimes called “stiffness” in other solvers. The higher the values the stronger the effect. Be careful not to make it too high as particles tend to explode.
Separates the particles spatially seeking to maintain the target division size. However this is not a velocity based force. It is relaxing particle positions per time step but does not maintain momentum. Pressure alone should give you a good result on its own.