My simulation is slower when animated objects are involved. Why?
RealFlow | Cinema 4D creates an internal collision geometry from the object for the interaction with particles. When the base object is static, this geometry has to be built once only, but when it's animated the collision geometry has to be recalculated with every frame. And, depending on the complexity of the base object, this takes some time and slows down the simulation. The most effective workaround is to reduce the number of polygons as far as possible or use low-res proxy objects.
The quality of the collision geometry also plays a role and you can adjust in the → "Volume" tag's parameters. → "Cell Size" and → "Surface Offset" are the crucial parameters. And when you click on → Collider > Display > Show Collision Geometry you can see the internal object.
Why is there a gap between the particles and the collision object?
...
If your object is an open, single-sided shell then you will always see a more or less small gap between the object's surface and the fluid. The reason is that RealFlow | Cinema 4D creates a layer around such an object to make it watertight. The thickness of this layer is Cell Size * 3 on each side of the polygon shell.
Why are simulations with point level animated objects (PLA) slow?
...