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package structs
// Definition of a quadtree and it's nodes recursively
type Quadtree struct {
boundary BoundingBox // Spatial outreach of the quadtree
centerOfMass Vec2 // Center of mass of the cell
totalMass float64 // Total mass of the cell
depth int // Depth of the cell in the quadtree
star Star2D // Star inside the cell
// NW, NE, SW, SE
quadrants []*Quadtree // List of quadtrees representing individual quadrants
// Quadrants
//northWest *Quadtree
//northEast *Quadtree
//southWest *Quadtree
//southEast *Quadtree
}
// CenterOfMass is a getter method for quadtrees.
// It returns the Center of mass of the quadtree it is applied on
func (q *Quadtree) CenterOfMass() Vec2 {
return q.centerOfMass
}
// SetCenterOfMass is a setter method for quadtrees.
// It sets the centerOfMass of the quadtree to the given value
func (q *Quadtree) SetCenterOfMass(centerOfMass Vec2) {
q.centerOfMass = centerOfMass
}
// CalcCenterOfMass is a calculator method for quadtrees.
// It recursively walks through the quadtree and calculates it's center of mass.
// The calculated center of mass is then inserted into the centerOfMass variable.
func (q *Quadtree) CalcCenterOfMass() (Vec2, float64) {
var totalMass float64 = 0
var x float64 = 0
var y float64 = 0
// If the Node is a leaf
if q.IsLeaf() == true {
// update the values needed to calculate the center of mass
totalMass += q.star.M
x += q.star.C.X * q.star.M
y += q.star.C.X * q.star.M
return (Vec2{x, y}, totalMass)
} else {
// Iterate over all the quadrants
for _, element := range q.quadrants {
// Calculate the center of mass for each quadrant
centerOfMass, totalMass := element.CalcCenterOfMass()
// Update the overall centerOfMass for the individual quadtree
q.centerOfMass.X += centerOfMass.X
q.centerOfMass.Y += centerOfMass.Y
q.totalMass += totalMass
}
}
// Return the original centerOfMass and totalMass
return (q.centerOfMass, q.totalMass)
}
// IsLeaf is a method for quadtrees returning true if the node is a leaf (has no children)
// or returning false if the node is nor a leaf (has children).
func (q *Quadtree) IsLeaf() bool {
for _, element := range q.quadrants {
if element == nil {
return true
}
}
return false
}
// NewQuadtree generates a new root node.
func NewQuadtree(boundary BoundingBox) *Quadtree {
return &Quadtree{boundary: boundary}
}
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