Collision detection functions

Author: tomas-novotny

collision.go

@@ -0,0 +1,40 @@
+package geom
+
+// CollisionRectangles checks if the given rectangles collide.
+func CollisionRectangles[T Number](r1 Rectangle[T], r2 Rectangle[T]) bool {
+	// TODO: support rotation
+
+	min1, max1 := r1.Min(), r1.Max()
+	min2, max2 := r2.Min(), r2.Max()
+
+	return min1.X <= max2.X && min2.X <= max1.X && min1.Y <= max2.Y && min2.Y <= max1.Y
+}
+
+// CollisionRectangleCircle checks if the given rectangle and circle collide.
+func CollisionRectangleCircle[T Number](r Rectangle[T], c Circle[T]) bool {
+	// TODO: support rotation
+
+	distance := c.Center.Subtract(r.Center).Abs()
+	extends := r.Size.Scale(0.5).ToVector()
+
+	// circle center is more than size outside rectangle borders
+	if distance.X > extends.X+c.Radius || distance.Y > extends.Y+c.Radius {
+		return false
+	}
+
+	// circle center is in rectangle
+	if distance.X <= extends.X || distance.Y <= extends.Y {
+		return true
+	}
+
+	// circle center is less than its size outside nearest border
+	return distance.Subtract(extends).Less(c.Radius)
+}
+
+// CollisionCircles checks if the given circles collide.
+func CollisionCircles[T Number](c1 Circle[T], c2 Circle[T]) bool {
+	distance := c1.Center.Subtract(c2.Center)
+	threshold := c1.Radius + c2.Radius
+
+	return distance.Less(threshold)
+}

size.go

@@ -75,6 +75,11 @@ func (s Size[T]) XY() (T, T) {
 	return s.Width, s.Height
 }
 
+// ToVector converts the size to a Vector.
+func (s Size[T]) ToVector() Vector[T] {
+	return Vector[T]{s.Width, s.Height}
+}
+
 // String returns a string in the form "WxH" using the underlying number formatting.
 func (s Size[T]) String() string {
 	return fmt.Sprintf("%sx%s", ToString(s.Width), ToString(s.Height))