shape.go

package box2d

/// This holds the mass data computed for a shape.
type MassData struct {
	/// The mass of the shape, usually in kilograms.
	Mass float64

	/// The position of the shape's centroid relative to the shape's origin.
	Center Point

	/// The rotational inertia of the shape about the local origin.
	I float64
}

func NewMassData() *MassData {
	return &MassData{}
}

/// A shape is used for collision detection. You can create a shape however you like.
/// Shapes used for simulation in World are created automatically when a Fixture
/// is created. Shapes may encapsulate a one or more child shapes.

type ShapeType uint8

const (
	ShapeTypeEdge      ShapeType = 0
	ShapeTypePolygon   ShapeType = 1
	ShapeTypeTypeCount ShapeType = 2
)

type ShapeInterface interface {
	/// Clone the concrete shape using the provided allocator.
	Clone() ShapeInterface

	/// Get the type of this shape. You can use this to down cast to the concrete shape.
	/// @return the shape type.
	GetType() ShapeType

	/// Get the type of this shape. You can use this to down cast to the concrete shape.
	/// @return the shape type.
	GetRadius() float64

	/// Get the number of child primitives.
	GetChildCount() int

	/// Test a point for containment in this shape. This only works for convex shapes.
	/// @param xf the shape world transform.
	/// @param p a point in world coordinates.
	TestPoint(xf Transform, p Point) bool

	/// Cast a ray against a child shape.
	/// @param output the ray-cast results.
	/// @param input the ray-cast input parameters.
	/// @param transform the transform to be applied to the shape.
	/// @param childIndex the child shape index
	RayCast(output *RayCastOutput, input RayCastInput, transform Transform, childIndex int) bool

	/// Given a transform, compute the associated axis aligned bounding box for a child shape.
	/// @param aabb returns the axis aligned box.
	/// @param xf the world transform of the shape.
	/// @param childIndex the child shape
	ComputeAABB(aabb *AABB, xf Transform, childIndex int)

	/// Compute the mass properties of this shape using its dimensions and density.
	/// The inertia tensor is computed about the local origin.
	/// @param massData returns the mass data for this shape.
	/// @param density the density in kilograms per meter squared.
	ComputeMass(massData *MassData, density float64)
}

type Shape struct {
	Type ShapeType

	/// Radius of a shape. For polygonal shapes this must be _polygonRadius. There is no support for
	/// making rounded polygons.
	Radius float64
}

func (shape Shape) GetType() ShapeType {
	return shape.Type
}

func (shape Shape) GetRadius() float64 {
	return shape.Radius
}

//@addedgo
func (shape *Shape) SetRadius(r float64) {
	shape.Radius = r
}