structs

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 Go to latest Published: Feb 5, 2019 License: GPL-3.0 Imports: 7 Imported by: 4

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structs

All of the structures used in the GalaxySimulator.

Documentation

Index

Examples

Constants

This section is empty.

Variables

This section is empty.

Functions

This section is empty.

Types

type BoundingBox 

type BoundingBox struct {
	Center Vec2    // Center of the box
	Width  float64 // Width of the box
}

BoundingBox is a struct defining the spatial outreach of a box

func NewBoundingBox 

func NewBoundingBox(center Vec2, width float64) BoundingBox

NewBoundingBox returns a new Bounding Box using the centerpoint and the width given by the function parameters

type Node 

type Node struct {
	Boundary     BoundingBox // Spatial outreach of the quadtree
	CenterOfMass Vec2        // Center of mass of the cell
	TotalMass    float64     // Total mass of all the stars in the cell
	Depth        int         // Depth of the cell in the tree

	Star Star2D // The actual star

	// NW, NE, SW, SE
	Subtrees [4]*Node // The child subtrees
}

Node defines a node in the tree storing the galaxy

func NewNode 

func NewNode(bounadry BoundingBox) *Node

NewNode creates a new new node using the given bounding box

Example

The example below creates a new node using the given bounding box 

newNode := NewNode(BoundingBox{
	Center: Vec2{
		X: 25,
		Y: 25,
	},
	Width: 50,
})
fmt.Printf("%v\n", newNode)

Output:

&{{{25 25} 50} {0 0} 0 0 {{0 0} {0 0} 0} [<nil> <nil> <nil> <nil>]}

func NewRoot 

func NewRoot(BoundingBoxWidth float64) *Node

NewRoot returns a pointer to a node defined as a root node. It taks the with of the BoundingBox as an argument resulting in a node that should (in theory) fit the whole galaxy if defined correctly.

Example

The example below creates a new root node at (0, 0) with the given width. The width given in this case is 100. 

root := NewRoot(100)
fmt.Printf("%v\n", root)

Output:

&{{{0 0} 100} {0 0} 0 0 {{0 0} {0 0} 0} [<nil> <nil> <nil> <nil>]}

func (Node) CalcAllForces 

func (n Node) CalcAllForces(star Star2D, theta float64) Vec2

CalcAllForces calculates the force acting in between the given star and all the other stars using the given theta. It gets all the other stars from the root node it is called on

Example

func (*Node) CalcCenterOfMass 

func (n *Node) CalcCenterOfMass() Vec2

CalcCenterOfMass calculates the center of mass for every node in the tree

Example

CalcCenterOfMass calculates the center of mass of the node it is called on. In the example below, the Tree contains two stars with equal mass (10): (20, 30) and (-20, -30). 

root := NewRoot(100)

root.Subdivide()

star1 := NewStar2D(Vec2{0, 0}, Vec2{0, 0}, 10)
star2 := NewStar2D(Vec2{3, 3}, Vec2{0, 0}, 10)

// Insert the stars into the tree
// There will be no error handling here, we'll assume that everything goes right..
_ = root.Insert(star1)
_ = root.Insert(star2)

root.CalcTotalMass()

centerOfMass := root.CalcCenterOfMass()
fmt.Println(centerOfMass)

func (*Node) CalcTotalMass 

func (n *Node) CalcTotalMass() float64

CalcTotalMass calculates the total mass for every node in the tree

Example

func (Node) DrawTreeLaTeX 

func (n Node) DrawTreeLaTeX(outpath string)

DrawTreeLaTeX writes the tree it is called on to a texfile defined by the outpath parameter and calls lualatex to build the tex-file

Example

Draws the tree to a pdf using lualatex for building the pdf. (Luatex is used, because pdflatex apparently cannot handle such deep recursion depths) 

// create a new root node
root := NewRoot(100)

// write the LaTeX to out.tex and build the tex using luatex
root.DrawTreeLaTeX("out.tex")

func (Node) GenForestTree 

func (n Node) GenForestTree(node *Node) string

GenForestTree draws the subtree it is called on. If there is a star inside of the root node, the node is drawn The method returns a string depicting the tree in latex forest structure

Example

Generate a tree using the LaTeX forest tree notation This is a minimal example using only a root node 

{ // Create a new root
	root := NewRoot(100)
	root.Star = Star2D{
		C: Vec2{
			X: 10,
			Y: 20,
		},
		V: Vec2{
			X: 0,
			Y: 0,
		},
		M: 20,
	}

	// generate the tree
	forestTree := root.GenForestTree(root)
	fmt.Println(forestTree)
	

Output:

[10 20[][][][]]
Example (DeepTree)

Generate a tree using the LaTeX forest tree notation. This is an example displaying a bigger tree. 

// Create a new root
root := NewRoot(100)

// Subdivide the root multiple times
root.Subdivide()
root.Subtrees[1].Subdivide()

// Insert a star into the tree
root.Subtrees[1].Star = Star2D{
	C: Vec2{
		X: 20,
		Y: 30,
	},
	V: Vec2{
		X: 0,
		Y: 0,
	},
	M: 20,
}

// Generate the tree
forestTree := root.GenForestTree(root)
fmt.Println(forestTree)

Output:

[[[][][][]][20 30[[][][][]][[][][][]][[][][][]][[][][][]]][[][][][]][[][][][]]]

func (Node) GetAllStars 

func (n Node) GetAllStars() []Star2D

GetAllStars returns all the stars in the tree it is called on in an array

Example

GetAllStars gets all the stars from a selected tree. In the example below, an empty node is generated, subdivided and two stars are inserted into it. Then, a list of all stars (the two that were previously inserted) gets generated and printed. 

// Define a new root node
root := NewRoot(100)

// Subdivide the root
root.Subdivide()

// Insert two stars into the tree
root.Subtrees[1].Star = Star2D{
	C: Vec2{
		X: 10,
		Y: 20,
	},
	V: Vec2{
		X: 0,
		Y: 0,
	},
	M: 0,
}
root.Subtrees[3].Star = Star2D{
	C: Vec2{
		X: 30,
		Y: 40,
	},
	V: Vec2{
		X: 0,
		Y: 0,
	},
	M: 0,
}

// Get the stars from the tree
starsList := root.GetAllStars()

// Print all the stars in the list
for _, star := range starsList {
	fmt.Println(star)
}

Output:

{{10 20} {0 0} 0}
{{30 40} {0 0} 0}

func (*Node) Insert 

func (n *Node) Insert(star Star2D) error

Insert inserts the given star into the Node or the tree it is called on

Example

Insert a star into a tree. If the star cannot be inserted (e.g. recursion depth too deep), Insert() returns an error 

// Initialize a tree and a star
root := NewRoot(100)
star := Star2D{
	C: Vec2{
		X: 12,
		Y: 34,
	},
	V: Vec2{
		X: 0,
		Y: 0,
	},
	M: 0,
}

// insert the star into the tree
err := root.Insert(star)

// handle potential errors
if err != nil {
	panic(err)
}

fmt.Printf("%v", root)

Output:

Direct insert of (12.000000, 34.000000)
&{{{0 0} 100} {0 0} 0 0 {{12 34} {0 0} 0} [<nil> <nil> <nil> <nil>]}
Example (Error)

Insert two stars that are very close to each other into the tree. A problem arises: the tree has to be subdivided so often, that the insert function raises a recursion depth error 

// Initialize a tree and two
root := NewRoot(100)
star1 := Star2D{
	C: Vec2{
		X: 5,
		Y: 5,
	},
	V: Vec2{
		X: 0,
		Y: 0,
	},
	M: 0,
}
star2 := Star2D{
	C: Vec2{
		X: 5.000000000000001,
		Y: 5.000000000000001,
	},
	V: Vec2{
		X: 0,
		Y: 0,
	},
	M: 0,
}

// insert the first star into the tree
err := root.Insert(star1)
// handle potential errors
if err != nil {
	panic(err)
}

// insert the second star into the tree
err = root.Insert(star2)
// handle potential errors
if err != nil {
	panic(err)
}

Output:

Direct insert of (5.000000, 5.000000)
Direct insert of (5.000000, 5.000000)
Direct insert of (5.000000, 5.000000)
Direct insert of (5.000000, 5.000000)
Direct insert of (5.000000, 5.000000)
Direct insert of (5.000000, 5.000000)
Direct insert of (5.000000, 5.000000)
Direct insert of (5.000000, 5.000000)
Direct insert of (5.000000, 5.000000)
Direct insert of (5.000000, 5.000000)
Direct insert of (5.000000, 5.000000)
Direct insert of (5.000000, 5.000000)
Direct insert of (5.000000, 5.000000)
Direct insert of (5.000000, 5.000000)
Direct insert of (5.000000, 5.000000)
Direct insert of (5.000000, 5.000000)
Direct insert of (5.000000, 5.000000)
Direct insert of (5.000000, 5.000000)
Direct insert of (5.000000, 5.000000)
Direct insert of (5.000000, 5.000000)
Direct insert of (5.000000, 5.000000)
Direct insert of (5.000000, 5.000000)
Direct insert of (5.000000, 5.000000)
Direct insert of (5.000000, 5.000000)
Direct insert of (5.000000, 5.000000)
Direct insert of (5.000000, 5.000000)
Direct insert of (5.000000, 5.000000)
Direct insert of (5.000000, 5.000000)
Direct insert of (5.000000, 5.000000)
Direct insert of (5.000000, 5.000000)
Direct insert of (5.000000, 5.000000)
Direct insert of (5.000000, 5.000000)
Direct insert of (5.000000, 5.000000)
Direct insert of (5.000000, 5.000000)
Direct insert of (5.000000, 5.000000)
Direct insert of (5.000000, 5.000000)
Direct insert of (5.000000, 5.000000)
Direct insert of (5.000000, 5.000000)
Direct insert of (5.000000, 5.000000)
Direct insert of (5.000000, 5.000000)
Direct insert of (5.000000, 5.000000)
Direct insert of (5.000000, 5.000000)
Direct insert of (5.000000, 5.000000)
Direct insert of (5.000000, 5.000000)
Direct insert of (5.000000, 5.000000)
Direct insert of (5.000000, 5.000000)
Direct insert of (5.000000, 5.000000)
Direct insert of (5.000000, 5.000000)
Direct insert of (5.000000, 5.000000)
Direct insert of (5.000000, 5.000000)
Could not insert star (5.000000, 5.000000) (recursion limit reached)

Could not insert star (5.000000, 5.000000) (recursion limit reached)

func (*Node) Subdivide 

func (n *Node) Subdivide()

Subdivide the tree

Example

The example below subdivides the node it is called on. The function inserts four pointers pointing to other nodes into the subtree array representing the quadrants.

The Code below prints the four subtrees that where generated: 

root := NewRoot(100)
root.Subdivide()
for i := 0; i < 4; i++ {
	fmt.Printf("%v\n", root.Subtrees[i])
}

Output:

&{{{-25 25} 50} {0 0} 0 0 {{0 0} {0 0} 0} [<nil> <nil> <nil> <nil>]}
&{{{25 25} 50} {0 0} 0 0 {{0 0} {0 0} 0} [<nil> <nil> <nil> <nil>]}
&{{{-25 -25} 50} {0 0} 0 0 {{0 0} {0 0} 0} [<nil> <nil> <nil> <nil>]}
&{{{25 -25} 50} {0 0} 0 0 {{0 0} {0 0} 0} [<nil> <nil> <nil> <nil>]}

type Star2D 

type Star2D struct {
	C Vec2    `json:"C"` // coordinates of the star
	V Vec2    `json:"V"` // velocity    of the star
	M float64 `json:"M"` // mass        of the star
}

Star2D defines a struct storing essential star information such as it's coordinate, velocity and mass

func NewStar2D 

func NewStar2D(c Vec2, v Vec2, m float64) Star2D

NewStar2D returns a new star using the given arguments as values for the Star

func (*Star2D) Accelerate 

func (star *Star2D) Accelerate(a Vec2, t float64)

Accelerate and move the star with it's velocity and the acceleration a for the time t This changes the position and the velocity of the star.

func (*Star2D) AccelerateVelocity 

func (star *Star2D) AccelerateVelocity(a Vec2, t float64)

AccelerateVelocity accelerates the star with the acceleration a for the time t. This changes the velocity of the star.

func (*Star2D) CalcNewPos 

func (star *Star2D) CalcNewPos(force Vec2, timestep float64)

CalcNewPos calculates the new position of a star using the force acting on it

func (*Star2D) Copy 

func (star *Star2D) Copy() Star2D

Copy Return a copy of the star by returning a star struct with the same values.

func (Star2D) InsideOf 

func (star Star2D) InsideOf(boundary BoundingBox) bool

InsideOf is a method that tests if the star it is applied on is in or outside of the given BoundingBox. It returns true if the star is inside of the BoundingBox and false if it isn't.

func (*Star2D) Move 

func (star *Star2D) Move(t float64)

Move the star with it's velocity for the time t. This changes the Position of the star.

type Stargalaxy 

type Stargalaxy struct {
	Star  Star2D
	Index int64
}

Stargalaxy is a struct bundling the star and the galaxy index it comes from

type Vec2 

type Vec2 struct {
	X float64 `json:"X"`
	Y float64 `json:"Y"`
}

Vec2 defines a vector

func CalcForce 

func CalcForce(s1 Star2D, s2 Star2D) Vec2

CalcForce calculates the force exerted on s1 by s2 and returns a vector representing that force

Example

func NewVec2 

func NewVec2(x float64, y float64) Vec2

NewVec2 returns a new Vec2 using the given coordinates

func (*Vec2) Add 

func (v *Vec2) Add(v2 Vec2) Vec2

Add returns the sum of this vector and the vector v2

func (*Vec2) Copy 

func (v *Vec2) Copy() Vec2

Copy creates a copy of the vector

func (*Vec2) Multiply 

func (v *Vec2) Multiply(s float64) Vec2

Multiply returns the product of the vector and a scalar s

Source Files

  • boundingBox.go
  • quadtree.go
  • star.go
  • stargalaxy.go
  • vector2D.go

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