rectangle.go

package cirno

import "fmt"

// Rectangle represents an oriented euclidian rectangle.
type Rectangle struct {
	center  Vector
	extents Vector
	xAxis   Vector
	yAxis   Vector
	angle   float64
	tag
	data
	domain
}

// TypeName returns the name of the shape type.
func (r *Rectangle) TypeName() string {
	return "Rectangle"
}

// Center returns the coordinates of the center of the rectangle.
func (r *Rectangle) Center() Vector {
	return r.center
}

// Move moves the rectangle in the specified direction; returns its new position.
func (r *Rectangle) Move(direction Vector) Vector {
	r.center = r.center.Add(direction)

	return r.center
}

// SetPosition sets the position of the rectangle to the given coordinates.
func (r *Rectangle) SetPosition(pos Vector) Vector {
	r.center = pos

	return r.center
}

// SetAngle sets the angle of the rectangle to the
// given value (in degrees).
func (r *Rectangle) SetAngle(angle float64) float64 {
	return r.Rotate(angle - r.angle)
}

// SetAngleRadians sets the angle of the rectangle to the
// given value (in radians).
func (r *Rectangle) SetAngleRadians(angle float64) float64 {
	return r.RotateRadians(angle - r.angle)
}

// ContainsPoint detects if the given point is inside the rectangle.
func (r *Rectangle) ContainsPoint(point Vector) bool {
	localPoint := point.Subtract(r.center)
	theta := -r.angle
	localPoint = localPoint.Rotate(theta)
	localRect := &aabb{
		min: NewVector(-r.extents.X, -r.extents.Y),
		max: NewVector(r.extents.X, r.extents.Y),
	}

	return localRect.containsPoint(localPoint)
}

// Width returns the width of the rectangle.
func (r *Rectangle) Width() float64 {
	return r.extents.X * 2
}

// Height returns the height of the rectangle.
func (r *Rectangle) Height() float64 {
	return r.extents.Y * 2
}

// Angle returns the angle of the rectangle (in degrees).
func (r *Rectangle) Angle() float64 {
	return r.angle
}

// AngleRadians returns the angle of the rectangle (in radians).
func (r *Rectangle) AngleRadians() float64 {
	return r.angle * DegToRad
}

// Rotate rotates the whole rectangle at the specified angle (in degrees).
//
// Returns the new angle of the rectangle (in degrees).
func (r *Rectangle) Rotate(angle float64) float64 {
	r.xAxis = r.xAxis.Rotate(angle)
	r.yAxis = r.yAxis.Rotate(angle)

	r.angle += angle
	r.angle = AdjustAngle(r.angle)

	return r.angle
}

// RotateRadians rotates the whole rectangle at the specified angle (in radians).
//
// Returns the new angle of the rectangle (in radians).
func (r *Rectangle) RotateRadians(angle float64) float64 {
	return r.Rotate(angle*RadToDeg) * DegToRad
}

// RotateAround rotates the rectangle around the specified base point.
func (r *Rectangle) RotateAround(angle float64, base Vector) Vector {
	r.center = r.center.RotateAround(angle, base)

	return r.center
}

// RotateAroundRadians rotates the rectangle around the specified base point
// at the angle in radians.
func (r *Rectangle) RotateAroundRadians(angle float64, base Vector) Vector {
	r.center = r.center.RotateAroundRadians(angle, base)

	return r.center
}

// Max returns the upper right point of the rectangle with no rotation.
func (r *Rectangle) Max() Vector {
	return r.center.Add(r.xAxis.MultiplyByScalar(r.extents.X).
		Add(r.yAxis.MultiplyByScalar(r.extents.Y)))
}

// Min returns the lower left point of the rectangle with no rotation.
func (r *Rectangle) Min() Vector {
	return r.center.Subtract(r.xAxis.MultiplyByScalar(r.extents.X).
		Add(r.yAxis.MultiplyByScalar(r.extents.Y)))
}

// Vertices returns the array of the rectangle vertices.
func (r *Rectangle) Vertices() [4]Vector {
	// Rectangle vertices.
	a := r.center.Add(r.xAxis.MultiplyByScalar(-r.extents.X).
		Add(r.yAxis.MultiplyByScalar(-r.extents.Y)))
	b := r.center.Add(r.xAxis.MultiplyByScalar(-r.extents.X).
		Add(r.yAxis.MultiplyByScalar(r.extents.Y)))
	c := r.center.Add(r.xAxis.MultiplyByScalar(r.extents.X).
		Add(r.yAxis.MultiplyByScalar(r.extents.Y)))
	d := r.center.Add(r.xAxis.MultiplyByScalar(r.extents.X).
		Add(r.yAxis.MultiplyByScalar(-r.extents.Y)))

	return [4]Vector{a, b, c, d}
}

// NewRectangle returns a new rectangle with specified parameters.
func NewRectangle(position Vector, width, height, angle float64) (*Rectangle, error) {
	if width <= 0.0 {
		return nil, fmt.Errorf(
			"the length of the rectangle must be positive")
	}

	if height <= 0.0 {
		return nil, fmt.Errorf(
			"the height of the rectangle must be positive")
	}

	rect := &Rectangle{}

	rect.center = position
	rect.extents = NewVector(width/2.0, height/2.0)
	rect.xAxis = NewVector(1, 0)
	rect.yAxis = NewVector(0, 1)
	rect.Rotate(angle)
	rect.treeNodes = []*quadTreeNode{}

	return rect, nil
}