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• Add a "Fill" emitter and drag the object, meant to be filled, to the emitter's "Body" slot.
• Set the emitter's "Fill Mode" to "Fill non Solid Volume".
• Check, if "Fill Volume" is enabled.

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• Add "Collision" and "Volume" tags to the object.
• Set Volume" tag > Volume Mode to "Solid Outside".

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The result: a "Cone" object, filled with particles.

It also possible to create particles around the object

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• Volume tag > Cell size.
• Smaller values create a better representation, but they will also allocate more memory.
• If you do not want to estimate an appropriate "Cell Size" value just choose a quality level from "Collision Geometry Detail" and let RealFlow | Cinema 4D do this work for you.

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