Sim Settings Menu

This menu displays a large number of settings that affect the entire simulation. The menu can be opened by clicking the arrow in the upper right of the Sim menu in the bottom bar.

The menu occupies the Simulation tab of the Settings menu, which also includes a View tab containing the View Settings Menu. The Simulation tab includes settings related to the underlying physics simulation.

## Time

### Time Zone

Allows the user to change the Time Zone of the date and time display.

### Average Simulation Speed

Displays the Average Simulation Speed of the simulation.

### Target Simulation Speed

Controls the Target Simulation Speed of the simulation.

## Gravity

### Enable Gravity

#### Gravitational Constant

Controls the strength of the Gravitational Constant.

#### Gravity Between Objects

Determines whether objects will be able to attract each other gravitationally in the N-body simulation. This is the same setting controlled by the Gravity button in the Sim menu in the bottom bar.

#### Self-Gravity

Enables gravity for other simulation features that depend on gravity, such as: volatile evaporation, spin fragmentation, and surface phase changes.

## Gravity Simulation Accuracy

### Auto Limit Simulation Speed

When this setting is on, Universe Sandbox will automatically limit the maximum possible Simulation Speed of a simulation to maintain a certain level of accuracy. When this setting is off, the user can set the Simulation Speed to any value, potentially reducing the accuracy of the simulation enough to prevent any realistic orbits.

### Gravity Tree Calculations

Enables an experimental gravity calculation method, which greatly improves performance in simulations with a large number of objects, but may decrease performance in simulations with a small number of objects. The gravity tree uses the following settings:

* Tree Cell Distance Ratio
	+ Represents the resolution of the gravity tree algorithm. A higher ratio may allow a faster computation, but could also produce more inaccuracy.
* Tree Work Ratio
	+ A read-only value that shows the reduction in calculation that the gravity tree method requires, compared to the previous method.

### Integrator

Changes the type of *N*-body integrator used to simulate gravity. There are six integrators available:

* Euler Explicit
* Euler Semi-Implicit
* Velocity Verlet
* RK2
* Forest-Ruth
* PEFRL

The default integrator is PEFRL.

#### Limit Multiplier

The value of this setting will scale the allowed maximum Simulation Speed relative to the Simulation Speed of the Balanced tuning profile. For example, when Limit Multiplier is set to 2, the maxmimum allowed Simulation Speed will be twice the size of the allowed Simulation Speed of the Balanced Profile.

The Accuracy profile has a Limit Multiplier of 0.1, and the Performance profile has a Limit Multiplier of 10.

#### Gravity Substeps

Displays the current number of substeps calculated within each time step. This setting is **read-only** and is automatically calculated by Universe Sandbox.

#### Performance Limiting Object

The maximum allowed Simulation Speed is automatically limited based on the orbital error in the simulation. This setting displays which object in the simulation is currently the source of the maximum orbital error, and therefore the object responsible for limiting the maximum Simulation Speed. This is often the object with the smallest orbit.

This setting is **read-only** and is automatically calculated by Universe Sandbox. If the Auto Limit Simulation Speed setting is off, this setting will display None, as there will be no performance limit on the Simulation Speed.

## Collisions

### Detect Collisions

If this setting is turned off, objects will pass through one another rather than colliding.

### Collision Heating

If this setting is turned off, collisions will not heat objects.

### Pause on Collision

When this setting is turned on, the simulation will automatically pause at the point when the next object collision occurs.

## Fragment Creation

### Create Fragments

Toggling off Create Fragments will turn off all of the following settings.

* Collision Fragmentation
	+ When turned off, objects involved in collisions will not fragment.
* Roche Fragmentation
	+ When turned off, objects will not experience Roche fragmentation.
* Friction Fragmentation
	+ When turned off, object will not experience friction fragmentation.
* Volatiles
	+ When turned off, objects will not produce volatiles, and all of the following settings will be turned off:
	+ Gas Loss
		- When turned off, objects will not produce volatiles via evaporation.
	+ Solar Wind Loss
		- When turned off, objects will not produce volatiles due to solar wind.
	+ Volatile Acceleration
		- Scales the acceleration with which volatiles are released
	+ Volatile Speed Multiplier
		- Scales the speed at which volatiles are released
	+ Mass Loss Multiplier
		- Scales the amount of an object's mass that is converted to volatiles

## Thermodynamics

### Temperature Simulation

When turned off, object temperatures will not change due to heating and cooling, and heat will not spread across the surface of an object. These processes can also be toggled on and off individually with the following settings:

* Heating and Cooling: allows object surfaces to gain or lose heat
	+ Stellar Heating: allows heating via Stellar Power
	+ Supernova Heating: allows heating via Supernova Power
	+ Atmosphere Heating: allows heating via Atmosphere Power
	+ Tidal Heating: allows heating via Tidal Power
	+ Gas Drag Heating: allows heating via Gas Drag Power
	+ Laser Heating: allows heating via Laser Power
	+ Collision Heating: allows heating via Impact Power
* Surface Heat Flow: allows heat to flow across the surface of an object
	+ Heat Diffusion Rate: the speed at which heat will flow across the surface of an object

## Surface Materials

### Phase Changes

Allows water on the surface of an object to change between solid, liquid, and gas phases based on environmental conditions.

### Liquid Flow

Allows liquid water to flow across the surface of an object.

### Gas Flow

Allows water vapor to flow across the surface of an object.

### Gas Loss

Allows objects to lose water vapor from their surfaces due to evaporation.

### Water Transfer

Allows impacts to transfer water between objects.

## Stellar Prominences

### Stellar Prominences

When turned off, stars will not experience stellar prominences, and the following settings will be **read-only**:

* Prominence Frequency
	+ Scales how often stellar prominences occur
* Prominence Duration
	+ Scales how long stellar prominences last