FAQ : Fluids and Objects

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 proxy representation of the 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. 

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 be a simulation's bottleneck.

I can see particles going through my collision object. What has happened?

With fast moving particles and/or a very small number of simulation steps per frame it might happen that a particle in a starting position goes to a final position in the next simulation step that is at the other side of the collision geometry:

  • To avoid this, activate the → "Collider" tag's "Continuous Collision Detection". 
  • By default the auto mode is enabled, and RealFlow | Cinema 4D will decide automatically, if the collision object requires "Continuous Collision Detection". 
  • Collision detection is computationally more intensive, and simulation take longer.
  • In some cases the automatic detection fails, and you have to disable enable "Continuous Collision Detection" manually.
I have enabled "Continuous Collision Detection", but there are still particles going through my collision object. Why?

If this is the case the problem can be fixed by increasing the number of → simulation steps (aka "substeps").

Why I can see the wetmap in the render, but not in the viewport?

Open the → material panel and go to the "Editor" section. Then enable "Animate Preview...".

I have activated the "Animate Preview..." option, but still I cannot see the wetmap. Why?

→ Wetmaps require an UVW Tag attached to the object. You will get this tag automatically when you make your object editable.

The wet map is distorted, mirrored or repeated. How can I fix this?

→ Wetmaps require proper UVW coordinates and this is within your responsibility. RealFlow | Cinema 4D does not perform any changes on UVWs or plausibility checks.

I have applied an object to the "Object" emitter, but there is no emission. What's wrong?

When the body's polygons are very small it might happen that you will not get any particle emission. To fix this, increase the "Fluid" container's → "Resolution" to create more particles. You may need very high settings (> 100 or more).

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