user: Provide the full official documentation entry for Settings, preserving all code examples.

assistant: # Settings

The domain object contains the entire simulation. Fluid simulations cannot leave the domain,
it will either collide with the edge or disappear, depending on the domain’s settings.

Keep in mind that large domains need higher resolutions and longer bake times.
You will want to make it just large enough that the simulation will fit inside it,
but not so large that it takes too long to compute the simulation.

To create a domain, add a cube and transform it until it encloses the area where you want
the simulation to take place. Translation, rotation, and scaling are all allowed.
To turn it into a fluid domain, click *Fluid* in the Properties ‣ Physics tab,
then select *Domain* as the fluid *Type*.

Domain Type
:   A fluid domain can control either liquid or gas flows. Liquid domains take all liquid flow objects
    that intersect with the domain into consideration. Gas domains consider all
    intersecting *Smoke*, *Fire*, and *Smoke & Fire* flow objects. It is not possible to change
    the domain type dynamically.

Resolution Divisions
:   The fluid domain is subdivided into many “cells” called [Voxels](../../../../glossary/index.html#term-Voxel)
    which make up “pixels” of fluid. This setting controls the number of subdivisions in the domain.
    Higher numbers of subdivisions are one way of creating higher resolution fluids.

    Since the resolution is defined in terms of “subdivisions”,
    larger domains will need more divisions to get an equivalent resolution to a small domain.
    For example, a one meter cube with 64 *Resolution Divisions* will need 128 divisions to match a 2 meter cube.
    The dimension used as the base division is the longest dimension of the objects bounding box.
    To help visualize the voxel size, the *Resolution Divisions* can be previewed with a small cube
    shown in the 3D Viewport, to show the size of these divisions.

Time Scale
:   Controls the speed of the simulation. Low values result in a “slow motion” simulation,
    while higher values can be used to advance the simulation faster
    (good for generating fluids to be used in still renders).

Adaptive Time Steps
:   Lets the solver automatically decide when to perform multiple simulation steps per frame.
    It takes into account the maximum and minimum number of time steps,
    the current *Frame Rate*, and the *Time Scale*.

CFL Number
:   Determines the maximum velocity per grid cell and is measured in grid cells per time step.
    Fluid is only allowed to move up to this velocity in one time step. If this threshold is
    exceeded the solver will subdivide the simulation step.

    In general, greater CFL
    ([Courant–Friedrichs–Lewy](https://en.wikipedia.org/wiki/Courant%E2%80%93Friedrichs%E2%80%93Lewy_condition))
    numbers will minimize the number of simulation steps and the computation time.
    Yet it will yield less physically accurate behavior for fast fluid flows.
    Smaller CFL numbers result in more simulation steps per frame, longer simulation times
    but more accurate behavior at high velocities (e.g. fast fluid flow colliding
    with obstacle).

Timesteps Maximum
:   Maximum number of allowed time steps per frame. If needed, the solver will divide
    a simulation step up to this number of sub-steps.

Timesteps Minimum
:   Minimum number of allowed time steps per frame. The solver will always perform at least
    this number of simulation steps per frame.

Gravity
:   By default the fluid solver will use the global scene gravity. This behavior can be disabled
    in the scene settings. Disabling the global gravity will enable the fluid gravity options.

Empty Space Gas Only
:   Voxels with values under this value are considered empty space.
    More empty space optimizes rendering. With OpenVDB caching it also reduces cache sizes.

Delete in Obstacle
:   Remover any volume of fluid that intersects with an obstacle inside the domain.