Why is there a gap between the particles and the collision object?
To be able to speed up the simulation, and especially to be able to simulate fast on the GPU, we use a RealFlow | Cinema 4D uses an internal proxy representation of a collision object – the so-called collision geometry. This proxy representation is based on Signed Distance Fields (SDF) from a cell-based representation of the geometry. The smaller the cell size, the more accurate representation, and smaller the gap. Of course, smaller cells will take more time to compute the SDF. In order to refine this proxy object you have to add a → "Volume " tag and decrease → "Cell Size" or choose a higher → "Collision Geometry Detail" option. You can also control the shape and look of the poxy through the → "Collider" tag's "Show Collision Geometry" option.
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.
Why are simulations with point level animated objects (PLA) slow?
With PLA-enabled objects, RealFlow | Cinema 4D has to recalculate the internal collision geometry with every single simulation step. Especially with small → "Cell Size" values PLA might can be a simulation's bottleneck.
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