Gravity Sim

Information

• Author: BinarySemaphore
• Version: 0.9.8
• Description: N-Body Simulation

Published Builds

• Windows: Release
• WebGL: Play.Unity

Controls

Movement

Key	Action
W	Forward
S	Backward
A	Left
D	Right
Shift	Up
Ctrl	Down

Movement is relative to the orientation of the camera

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Movement speed is relative to zoom (further out is faster)

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Movement is disabled if camera is in Tracking Mode

Camera

With Left Click Down:

Cursor Movement	Action
Horizontal	Rotate camera about Y axis
Vertical	Rotate camera about X+Z axis (Pitch)

Rotation is plane-aligned with the x and z axis; y axis is always vertical to perspective

Mouse Wheel	Action
Scroll Down	Zoom In
Scroll Up	Zoom Out

Zoom is logarithmic

Modes

1. Free Mode: Free to use movement to position camera focus anywhere
2. Tracking Mode: Track an object

Key	Action
R	Reset focus to starting position
F	Enable Free Mode
-	Cycle Tracking Mode previous object
=	Cycle Tracking Mode next object
1-9	Set Tracking Mode on object by mass

Tracking with 1-9, targets objects with the current highest masses (1: most mass; 9: 9th most mass)

Other

Key	Action
Comma	Decrease time factor
Period	Increase time factor
Escape	Open Menu or Resume
Q	While in menu; quit program

Time factors are 1, 2, 4, 8, and 16; Larger time factors reduce accuracy

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The Menu will pause the simulation until you resume

Menu

1. Exit Game: Quit the program.
2. Reset: Reset simulation to original or loaded universe settings
3. Load: Bring up load game sub-menu
4. Save: Bring up save game sub-menu
5. Action View: Hide menu and use normal free/tracking mode camera; Escape or Space to return to Main Menu
6. Resume: Resume simulation

Configuration

Configuration can be set in a JSON file labeled universe.json existing in the same directory as the EXE.

Reference

Label	Default	Limits	Description
massTransferRate	25	1 to Infinity	The mass transfer coefficient to mass difference transfer rate. Higher values means smaller objects are consumed by larger objects at a faster rate.
massTransferRestriction	50000	1 to Infinity	Restrict mass transfer due to relative velocity at contact. Higher values means less mass can transfer while there is relative moment between two or more colliding objects. Implies grouped objects must settle before forming into a unified object.
heatScale	0.1	0.0 to 1.0	Heat coefficient applied between two or more particles during mass transfer. Higher values means less mass transfer to produce heat (faster red coloring effect).
tailEmissionByRate	8.0	0.0 to 50.0	Number of tail particle effects to produce per 1 meter per second of object/particle's velocity.
gravConst	0.0006674	0 to Infinity	Gravitational Constant.
particleDensity	990.0	1.0 to Infinity	Density used to calculate volume of the objects by mass. Lower density values means larger volume
particleCount	50	0 to Many	Initial Particle/Object count.
initialRadius	550	10 to Infinity	Boundary for randomly setting initial starting points of particles/objects.
initialDistribution	[2, 1, 1, 1, 1]	0 to 500 Each	Distribution of initial locations of objects inside initialRadius boundary
initialMass.min	100	1 to Infinity	Lower bounds for random initial mass given to objects/particles.
initialMass.max	500	1 to Infinity	Upper bounds for random initial mass given to objects/particles.

All values are floats/decimal values

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The massTransferRate and massTransferRestriction are inversely proportional to one another; to keep ratio, if both must increase by same amount

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For heatScale, Heat is not currently dissipated. Any heat (red coloring) an object picks up, it will keep

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The tailEmissionByRate can affect performance, zero disables tail effect

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The gravConst is the G coefficient in the equation Force = G * (mass1 * mass2) / distance^2. Default value is accurate to real life except by a factor of 1*10^6 (to speed things up)

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The particleDensity default is water on average between 0c and 90c.

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Currently N-Body simulation is partial brute force with O(n!), not Quad-tree, so large numbers of particalCount can kill performance

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The initialDistribution sets random weights from origin of the radius, initialRadius, of a sphere by random ranges [0% to 100%, 0% to 80%, 0% to 60%, 0% to 40%, 0% to 20%, 0% to 1%]. Suggest not messing with this.

Example

{
    "massTransferRate": 25.0,
    "massTransferRestriction": 50000.0,
    "heatScale": 0.01,
    "tailEmissionRate": 8.0,
    "gravConst": 0.0006674,
    "particleDensity": 990.0,
    "particleCount": 50,
    "initialRadius": 100.0,
    "initialDistribution": [
        2, 1, 1, 1, 1
    ],
    "initialMass": {
        "min": 100.0,
        "max": 500.0
    }
}