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fixture.go
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fixture.go
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package box2d
/// This holds contact filtering data.
type Filter struct {
/// The collision category bits. Normally you would just set one bit.
CategoryBits uint16
/// The collision mask bits. This states the categories that this
/// shape would accept for collision.
MaskBits uint16
/// Collision groups allow a certain group of objects to never collide (negative)
/// or always collide (positive). Zero means no collision group. Non-zero group
/// filtering always wins against the mask bits.
GroupIndex int16
}
func MakeFilter() Filter {
return Filter{
CategoryBits: 0x0001,
MaskBits: 0xFFFF,
GroupIndex: 0,
}
}
/// A fixture definition is used to create a fixture. This class defines an
/// abstract fixture definition. You can reuse fixture definitions safely.
type FixtureDef struct {
/// The shape, this must be set. The shape will be cloned, so you
/// can create the shape on the stack.
Shape ShapeInterface
/// Use this to store application specific fixture data.
UserData interface{}
/// The friction coefficient, usually in the range [0,1].
Friction float64
/// The restitution (elasticity) usually in the range [0,1].
Restitution float64
/// The density, usually in kg/m^2.
Density float64
/// A sensor shape collects contact information but never generates a collision
/// response.
IsSensor bool
/// Contact filtering data.
Filter Filter
}
/// The constructor sets the default fixture definition values.
func MakeFixtureDef() FixtureDef {
return FixtureDef{
Shape: nil,
UserData: nil,
Friction: 0.2,
Restitution: 0.0,
Density: 0.0,
IsSensor: false,
}
}
/// This proxy is used internally to connect fixtures to the broad-phase.
type FixtureProxy struct {
Aabb AABB
Fixture *Fixture
ChildIndex int
ProxyId int
}
// /// A fixture is used to attach a shape to a body for collision detection. A fixture
// /// inherits its transform from its parent. Fixtures hold additional non-geometric data
// /// such as friction, collision filters, etc.
// /// Fixtures are created via b2Body::CreateFixture.
// /// @warning you cannot reuse fixtures.
type Fixture struct {
Density float64
Next *Fixture
Body *Body
Shape ShapeInterface
Friction float64
Restitution float64
Proxies []FixtureProxy
ProxyCount int
Filter Filter
IsSensor bool
UserData interface{}
}
func NewFixture() *Fixture {
return &Fixture{
Next: nil,
Body: nil,
Filter: MakeFilter(),
}
}
func (fix Fixture) GetType() ShapeType {
return fix.Shape.GetType()
}
func (fix Fixture) GetShape() ShapeInterface {
return fix.Shape
}
func (fix Fixture) GetFilterData() Filter {
return fix.Filter
}
func (fix Fixture) GetUserData() interface{} {
return fix.UserData
}
func (fix *Fixture) SetUserData(data interface{}) {
fix.UserData = data
}
func (fix Fixture) GetBody() *Body {
return fix.Body
}
func (fix Fixture) GetNext() *Fixture {
return fix.Next
}
func (fix *Fixture) SetDensity(density float64) {
fix.Density = density
}
func (fix Fixture) GetDensity() float64 {
return fix.Density
}
func (fix Fixture) GetFriction() float64 {
return fix.Friction
}
func (fix *Fixture) SetFriction(friction float64) {
fix.Friction = friction
}
func (fix Fixture) GetRestitution() float64 {
return fix.Restitution
}
func (fix *Fixture) SetRestitution(restitution float64) {
fix.Restitution = restitution
}
func (fix Fixture) TestPoint(p Point) bool {
return fix.Shape.TestPoint(fix.Body.GetTransform(), p)
}
func (fix Fixture) RayCast(output *RayCastOutput, input RayCastInput, childIndex int) bool {
return fix.Shape.RayCast(output, input, fix.Body.GetTransform(), childIndex)
}
func (fix Fixture) GetMassData(massData *MassData) {
fix.Shape.ComputeMass(massData, fix.Density)
}
func (fix Fixture) GetAABB(childIndex int) AABB {
return fix.Proxies[childIndex].Aabb
}
///////////////////////////////////////////////////////////////////////////////
///////////////////////////////////////////////////////////////////////////////
///////////////////////////////////////////////////////////////////////////////
// Fixture.cpp
///////////////////////////////////////////////////////////////////////////////
///////////////////////////////////////////////////////////////////////////////
///////////////////////////////////////////////////////////////////////////////
func MakeFixture() Fixture {
return Fixture{
UserData: nil,
Body: nil,
Next: nil,
Proxies: nil,
ProxyCount: 0,
Shape: nil,
Density: 0.0,
}
}
func (fix *Fixture) Create(body *Body, def *FixtureDef) {
fix.UserData = def.UserData
fix.Friction = def.Friction
fix.Restitution = def.Restitution
fix.Body = body
fix.Next = nil
fix.Filter = def.Filter
fix.IsSensor = def.IsSensor
fix.Shape = def.Shape.Clone()
// Reserve proxy space
childCount := fix.Shape.GetChildCount()
fix.Proxies = make([]FixtureProxy, childCount)
for i := 0; i < childCount; i++ {
fix.Proxies[i].Fixture = nil
fix.Proxies[i].ProxyId = nullProxyID
}
fix.ProxyCount = 0
fix.Density = def.Density
}
func (fix *Fixture) Destroy() {
// The proxies must be destroyed before calling this.
fix.Proxies = nil
fix.Shape = nil
}
func (fix *Fixture) CreateProxies(broadPhase *BroadPhase, xf Transform) {
// Create proxies in the broad-phase.
fix.ProxyCount = fix.Shape.GetChildCount()
for i := 0; i < fix.ProxyCount; i++ {
proxy := &fix.Proxies[i]
fix.Shape.ComputeAABB(&proxy.Aabb, xf, i)
proxy.ProxyId = broadPhase.CreateProxy(proxy.Aabb, proxy)
proxy.Fixture = fix
proxy.ChildIndex = i
}
}
func (fix *Fixture) DestroyProxies(broadPhase *BroadPhase) {
// Destroy proxies in the broad-phase.
for i := 0; i < fix.ProxyCount; i++ {
proxy := &fix.Proxies[i]
broadPhase.DestroyProxy(proxy.ProxyId)
proxy.ProxyId = nullProxyID
}
fix.ProxyCount = 0
}
func (fix *Fixture) Synchronize(broadPhase *BroadPhase, transform1 Transform, transform2 Transform) {
if fix.ProxyCount == 0 {
return
}
for i := 0; i < fix.ProxyCount; i++ {
proxy := &fix.Proxies[i]
// Compute an AABB that covers the swept shape (may miss some rotation effect).
aabb1 := AABB{}
aabb2 := AABB{}
fix.Shape.ComputeAABB(&aabb1, transform1, proxy.ChildIndex)
fix.Shape.ComputeAABB(&aabb2, transform2, proxy.ChildIndex)
proxy.Aabb.CombineTwoInPlace(aabb1, aabb2)
displacement := PointSub(transform2.P, transform1.P)
broadPhase.MoveProxy(proxy.ProxyId, proxy.Aabb, displacement)
}
}
func (fix *Fixture) SetFilterData(filter Filter) {
fix.Filter = filter
fix.Refilter()
}
func (fix *Fixture) Refilter() {
if fix.Body == nil {
return
}
// Flag associated contacts for filtering.
edge := fix.Body.GetContactList()
for edge != nil {
contact := edge.Contact.Data()
fixtureA := contact.GetFixtureA()
fixtureB := contact.GetFixtureB()
if fixtureA == fix || fixtureB == fix {
contact.FlagForFiltering()
}
edge = edge.Next
}
world := fix.Body.GetWorld()
if world == nil {
return
}
// Touch each proxy so that new pairs may be created
broadPhase := &world.ContactManager.BroadPhase
for i := 0; i < fix.ProxyCount; i++ {
broadPhase.TouchProxy(fix.Proxies[i].ProxyId)
}
}
func (fix *Fixture) SetSensor(sensor bool) {
if sensor != fix.IsSensor {
fix.Body.SetAwake(true)
fix.IsSensor = sensor
}
}