...
- Add "Collider" and "Volume" tags to the mask objects – the "Collider" tag tells RealFlow | Cinema 4D that there is an interacting object.
- Select the "Volume" tags. If the "Volume Mode" has not been recognited automatically set the option to "Solid Inside".
- Reset the scene (go to thr the last frame, then back to 0). You will see that the volumes of the three remaining cubes have been used as a mask to clip the particles. This way it is possible to create complex shapes without having to model an appropriate container.
...