Initial commit.

quadtree/quadtree.go

@@ -0,0 +1,192 @@
+package quadtree
+
+import (
+	"fluids/colliders"
+	"fluids/gamedata"
+)
+
+const (
+	QuadtreeMaxColliders = 10
+)
+
+type Quadrant struct {
+	Position   gamedata.Vector
+	Dimensions gamedata.Vector
+}
+
+type Quadtree struct {
+	quadrant  Quadrant
+	children  []*Quadtree
+	colliders []colliders.Collider
+}
+
+func New(quadrant Quadrant) *Quadtree {
+	qt := &Quadtree{
+		quadrant: quadrant,
+	}
+	return qt
+}
+
+func (q *Quadtree) Insert(obj colliders.Collider) bool {
+
+	var result bool = false
+	//check that object meets containment criteria
+	if q.ContainsPoint(obj.GetPosition()) {
+
+		//if we have children, we go deeper
+		if len(q.children) > 0 {
+			for _, node := range q.children {
+				if node.Insert(obj) {
+					result = true
+					break
+				}
+			}
+		} else if len(q.colliders) < QuadtreeMaxColliders {
+			//otherwise, if we have space, add
+			q.colliders = append(q.colliders, obj)
+			result = true
+		} else {
+			//otherwise we have to subdivide, reorganize, and add
+			result = q.SubdivideAndInsert(obj)
+		}
+	}
+	return result
+}
+
+func (q *Quadtree) ContainsPoint(p gamedata.Vector) bool {
+	var result bool = false
+	if (q.quadrant.Position.X-q.quadrant.Dimensions.X/2) <= p.X &&
+		p.X <= (q.quadrant.Position.X+q.quadrant.Dimensions.X/2) &&
+		(q.quadrant.Position.Y-q.quadrant.Dimensions.Y/2) <= p.Y &&
+		p.Y <= (q.quadrant.Position.Y+q.quadrant.Dimensions.Y/2) {
+		result = true
+	}
+	return result
+}
+
+func (q *Quadtree) Remove(obj colliders.Collider) bool {
+	var result bool = false
+
+	if q.ContainsPoint(obj.GetPosition()) {
+
+		if len(q.colliders) > 0 {
+			//examine existing colliders
+			var collection []colliders.Collider
+			for _, node := range q.colliders {
+				if node == obj {
+					result = true
+				} else {
+					collection = append(collection, node)
+				}
+			}
+			q.colliders = collection
+		} else {
+			//need to check children
+			for _, child := range q.children {
+				if child.Remove(obj) {
+					result = true
+					break
+				}
+			}
+		}
+	}
+
+	return result
+}
+
+func (q *Quadtree) SubdivideAndInsert(obj colliders.Collider) bool {
+
+	var result bool = false
+
+	//initialize up children
+	q.children = q.children[:0]
+	q.children = append(q.children, New(Quadrant{Position: gamedata.Vector{X: q.quadrant.Position.X - q.quadrant.Dimensions.X/4, Y: q.quadrant.Position.Y - q.quadrant.Dimensions.Y/4}, Dimensions: gamedata.Vector{X: q.quadrant.Dimensions.X / 2, Y: q.quadrant.Dimensions.Y / 2}}))
+	q.children = append(q.children, New(Quadrant{Position: gamedata.Vector{X: q.quadrant.Position.X + q.quadrant.Dimensions.X/4, Y: q.quadrant.Position.Y - q.quadrant.Dimensions.Y/4}, Dimensions: gamedata.Vector{X: q.quadrant.Dimensions.X / 2, Y: q.quadrant.Dimensions.Y / 2}}))
+	q.children = append(q.children, New(Quadrant{Position: gamedata.Vector{X: q.quadrant.Position.X - q.quadrant.Dimensions.X/4, Y: q.quadrant.Position.Y + q.quadrant.Dimensions.Y/4}, Dimensions: gamedata.Vector{X: q.quadrant.Dimensions.X / 2, Y: q.quadrant.Dimensions.Y / 2}}))
+	q.children = append(q.children, New(Quadrant{Position: gamedata.Vector{X: q.quadrant.Position.X + q.quadrant.Dimensions.X/4, Y: q.quadrant.Position.Y + q.quadrant.Dimensions.Y/4}, Dimensions: gamedata.Vector{X: q.quadrant.Dimensions.X / 2, Y: q.quadrant.Dimensions.Y / 2}}))
+
+	//move colliders into child nodes
+	var failed bool = false
+	for _, collider := range q.colliders {
+		var added bool = false
+		for _, node := range q.children {
+			if node.Insert(collider) {
+				added = true
+				break
+			}
+		}
+
+		//couldn't add collider into any subdivided node; failure
+		if !added {
+			failed = true
+			break
+		}
+	}
+
+	//if all went well:
+	// a. need to wipe colliders from current node
+	// b. need to now insert new collider into one of the children
+	if !failed {
+		q.colliders = q.colliders[:0]
+
+		for _, node := range q.children {
+			if node.Insert(obj) {
+				result = true
+				break
+			}
+		}
+	}
+
+	return result
+}
+
+func (q *Quadtree) Clear() {
+	q.colliders = q.colliders[:0]
+	q.children = q.children[:0]
+}
+
+func (q *Quadtree) GetQuadrants() []Quadrant {
+	var result []Quadrant
+
+	//if we have children, traverse and add their quadrants
+	if len(q.children) > 0 {
+		for _, child := range q.children {
+			result = append(result, child.GetQuadrants()...)
+		}
+	}
+
+	result = append(result, q.quadrant)
+
+	return result
+}
+
+// find and retrieve all colliders in given quadrant
+func (q *Quadtree) FindAll(quadrant Quadrant) []colliders.Collider {
+	var result []colliders.Collider
+
+	//search coordinates
+	sx0 := quadrant.Position.X - quadrant.Dimensions.X/2
+	sx1 := quadrant.Position.X + quadrant.Dimensions.X/2
+	sy0 := quadrant.Position.Y - quadrant.Dimensions.Y/2
+	sy1 := quadrant.Position.Y + quadrant.Dimensions.Y/2
+
+	//quadtree coordinates
+	qx0 := q.quadrant.Position.X - q.quadrant.Dimensions.X/2
+	qx1 := q.quadrant.Position.X + q.quadrant.Dimensions.X/2
+	qy0 := q.quadrant.Position.Y - q.quadrant.Dimensions.Y/2
+	qy1 := q.quadrant.Position.Y + q.quadrant.Dimensions.Y/2
+
+	//AABB check
+	if sx0 < qx1 && sx1 > qx0 &&
+		sy0 < qy1 && sy1 > qy0 {
+
+		//if we have children, check each of those
+		for _, node := range q.children {
+			result = append(result, node.FindAll(quadrant)...)
+		}
+
+		result = append(result, q.colliders...)
+	}
+
+	return result
+}