// undine docs
Emitters
An emitter is an object that generates fluid particles during the simulation.
Emitters sit at the boundary between scene setup and the numerical system because they define how liquid enters the simulation.
Emitter role in the workflow
After scene configuration, emitters generate the fluid particles that represent the simulated liquid.
That makes emitters a core part of the handoff between scene design and simulation execution.
The Objects tab can show an emitter object field and an Add / Volume control, which indicates that volume-style sources are part of the intended workflow.
| Emitter check | Expected result | Why it matters |
|---|---|---|
| Tagged role | The source object is tagged as Emitter. | The solver only treats tagged objects as liquid sources. |
| Scene count | Tagged in Scene reports the expected emitter count. | A zero emitter count usually means no liquid can be generated. |
| Domain overlap | The emitter is inside or intersects the domain. | Emitters outside the active domain may be clipped or ignored. |
| Volume interpretation | Volume-style emitters are added through the visible Add / Volume workflow when needed. | Volume sources can define initial liquid regions or filled shapes more directly than surface-only sources. |
Particle density from emitters
Emitter output is affected by global particle distribution and density settings. If an emitter looks sparse, produces holes, or creates too many particles, check particle-per-cell, reseeding, density strength, and viewport limits before changing the emitter object itself.
Practical setup notes
Before pressing Run
- Apply or confirm object transforms when scale matters for the emitter volume.
- Keep initial liquid sources inside the domain unless the intended effect is a source entering from outside.
- Use a short frame range while testing emitter density and solver cost.
- Watch POINTS in the Actions tab to confirm particle count is in the expected range.
How this page can expand
Future versions of this chapter can document emitter-specific controls, scene preparation notes, and example setups without changing the overall documentation structure.