You can emit fluid into the volume of selected geometry. For example, you can select a modeled polygon object and fill its volume with fluid.

To fill geometry with fluid
- Complete the steps to emit fluid from objects.
- Select the fluid, then click the fluidEmitter tab in the Attribute Editor.
- Expand the Basic Emitter Attributes section.
- Turn on Fill Object.
Fluid emits into the volume of the object rather than from its surface.