forked from g3n/engine
/
body.go
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/
body.go
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// Copyright 2016 The G3N Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package object
import (
"github.com/g3n/engine/graphic"
"github.com/g3n/engine/math32"
"github.com/g3n/engine/material"
"github.com/g3n/engine/experimental/collision/shape"
)
// Body represents a physics-driven body.
type Body struct {
*graphic.Graphic // TODO future - embed core.Node instead and calculate properties recursively
material *material.Material // Physics material specifying friction and restitution
index int
name string
// Mass properties
mass float32 // Total mass
invMass float32
invMassEff float32 // Effective inverse mass
// Rotational inertia and related properties
rotInertia *math32.Matrix3 // Angular mass i.e. moment of inertia in local coordinates
invRotInertia *math32.Matrix3 // Inverse rotational inertia in local coordinates
invRotInertiaEff *math32.Matrix3 // Effective inverse rotational inertia in local coordinates
invRotInertiaWorld *math32.Matrix3 // Inverse rotational inertia in world coordinates
invRotInertiaWorldEff *math32.Matrix3 // Effective rotational inertia in world coordinates
fixedRotation bool // Set to true if you don't want the body to rotate. Make sure to run .updateMassProperties() after changing this.
// Position
position *math32.Vector3 // World position of the center of gravity (World space position of the body.)
initPosition *math32.Vector3 // Initial position of the body.
prevPosition *math32.Vector3 // Previous position
interpPosition *math32.Vector3 // Interpolated position of the body.
// Rotation
quaternion *math32.Quaternion // World space orientation of the body.
initQuaternion *math32.Quaternion
prevQuaternion *math32.Quaternion
interpQuaternion *math32.Quaternion // Interpolated orientation of the body.
// Linear and angular velocities
velocity *math32.Vector3 // Linear velocity (World space velocity of the body.)
initVelocity *math32.Vector3 // Initial linear velocity (World space velocity of the body.)
angularVelocity *math32.Vector3 // Angular velocity of the body, in world space. Think of the angular velocity as a vector, which the body rotates around. The length of this vector determines how fast (in radians per second) the body rotates.
initAngularVelocity *math32.Vector3
// Force and torque
force *math32.Vector3 // Linear force on the body in world space.
torque *math32.Vector3 // World space rotational force on the body, around center of mass.
// Damping and factors
linearDamping float32
angularDamping float32
linearFactor *math32.Vector3 // Use this property to limit the motion along any world axis. (1,1,1) will allow motion along all axes while (0,0,0) allows none.
angularFactor *math32.Vector3 // Use this property to limit the rotational motion along any world axis. (1,1,1) will allow rotation along all axes while (0,0,0) allows none.
// Body type and sleep settings
bodyType BodyType
sleepState BodySleepState // Current sleep state.
allowSleep bool // If true, the body will automatically fall to sleep.
sleepSpeedLimit float32 // If the speed (the norm of the velocity) is smaller than this value, the body is considered sleepy.
sleepTimeLimit float32 // If the body has been sleepy for this sleepTimeLimit seconds, it is considered sleeping.
timeLastSleepy float32
wakeUpAfterNarrowphase bool
// Collision settings
colFilterGroup int // Collision filter group
colFilterMask int // Collision filter mask
colResponse bool // Whether to produce contact forces when in contact with other bodies. Note that contacts will be generated, but they will be disabled.
aabb *math32.Box3 // World space bounding box of the body and its shapes.
aabbNeedsUpdate bool // Indicates if the AABB needs to be updated before use.
boundingRadius float32 // Total bounding radius of the body (TODO including its shapes, relative to body.position.)
// Cached geometry properties
faces [][3]math32.Vector3
faceNormals []math32.Vector3
worldFaceNormals []math32.Vector3
uniqueEdges []math32.Vector3
worldUniqueEdges []math32.Vector3
shape shape.IShape
// TODO future (for now a body is a single graphic with a single geometry)
// shapes []*Shape
// shapeOffsets []float32 // Position of each Shape in the body, given in local Body space.
// shapeOrientations [] ?
}
// BodyType specifies how the body is affected during the simulation.
type BodyType int
const (
// A static body does not move during simulation and behaves as if it has infinite mass.
// Static bodies can be moved manually by setting the position of the body.
// The velocity of a static body is always zero.
// Static bodies do not collide with other static or kinematic bodies.
Static = BodyType(iota)
// A kinematic body moves under simulation according to its velocity.
// They do not respond to forces.
// They can be moved manually, but normally a kinematic body is moved by setting its velocity.
// A kinematic body behaves as if it has infinite mass.
// Kinematic bodies do not collide with other static or kinematic bodies.
Kinematic
// A dynamic body is fully simulated.
// Can be moved manually by the user, but normally they move according to forces.
// A dynamic body can collide with all body types.
// A dynamic body always has finite, non-zero mass.
Dynamic
)
// TODO Update simulation checks for BodyType to use bitwise operators ?
// BodyStatus specifies
type BodySleepState int
const (
Awake = BodySleepState(iota)
Sleepy
Sleeping
)
// Events
const (
SleepyEvent = "physics.SleepyEvent" // Dispatched after a body has gone in to the sleepy state.
SleepEvent = "physics.SleepEvent" // Dispatched after a body has fallen asleep.
WakeUpEvent = "physics.WakeUpEvent" // Dispatched after a sleeping body has woken up.
CollideEvent = "physics.CollideEvent" // Dispatched after two bodies collide. This event is dispatched on each of the two bodies involved in the collision.
)
// TODO
type HullType int
const (
Sphere = HullType(iota)
Capsule
Mesh // use mesh itself
)
// NewBody creates and returns a pointer to a new RigidBody.
// The igraphic's geometry *must* be convex.
func NewBody(igraphic graphic.IGraphic) *Body {
b := new(Body)
b.Graphic = igraphic.GetGraphic()
b.bodyType = Dynamic
// Rotational inertia and related properties
b.rotInertia = math32.NewMatrix3()
b.invRotInertia = math32.NewMatrix3()
b.invRotInertiaEff = math32.NewMatrix3()
b.invRotInertiaWorld = math32.NewMatrix3()
b.invRotInertiaWorldEff = math32.NewMatrix3()
// Position
pos := b.GetNode().Position()
b.position = pos.Clone()
b.prevPosition = pos.Clone()
b.interpPosition = pos.Clone()
b.initPosition = pos.Clone()
// Rotation
quat := b.GetNode().Quaternion()
b.quaternion = quat.Clone()
b.prevQuaternion = quat.Clone()
b.interpQuaternion = quat.Clone()
b.initQuaternion = quat.Clone()
// Linear and angular velocities
b.velocity = math32.NewVec3()
b.initVelocity = math32.NewVec3()
b.angularVelocity = math32.NewVec3()
b.initAngularVelocity = math32.NewVec3()
// Force and torque
b.force = math32.NewVec3()
b.torque = math32.NewVec3()
// Damping and factors
b.linearDamping = 0.01
b.angularDamping = 0.01
b.linearFactor = math32.NewVector3(1, 1, 1)
b.angularFactor = math32.NewVector3(1, 1, 1)
// Sleep settings
b.allowSleep = true
b.sleepState = Awake
b.sleepSpeedLimit = 0.1
b.sleepTimeLimit = 1
b.timeLastSleepy = 0
// Collision filtering
b.colFilterGroup = 1
b.colFilterMask = -1
//b.fixedRotation = true
b.wakeUpAfterNarrowphase = false
b.SetShape(shape.NewConvexHull(b.GetGeometry()))
b.SetMass(1)
b.UpdateMassProperties()
b.UpdateEffectiveMassProperties()
return b
}
// TODO future: modify this to be "AddShape" and keep track of list of shapes, their positions and orientations
// For now each body can only be a single shape or a single geometry
func (b *Body) SetShape(shape shape.IShape) {
b.shape = shape
}
func (b *Body) Shape() shape.IShape {
return b.shape
}
func (b *Body) BoundingBox() math32.Box3 {
// TODO future allow multiple shapes
mat4 := math32.NewMatrix4().Compose(b.position, b.quaternion, math32.NewVector3(1,1,1))
localBB := b.shape.BoundingBox()
worldBB := localBB.ApplyMatrix4(mat4)
return *worldBB
}
func (b *Body) SetMass(mass float32) {
// Do nothing if current mass is already the specified mass
if mass == b.mass {
return
}
// Set mass and update inverse mass
b.mass = mass
if b.mass > 0 {
b.invMass = 1.0 / b.mass
} else {
// Body mass is zero - this means that the body is static
b.invMass = 0
b.bodyType = Static
}
b.UpdateMassProperties()
}
func (b *Body) SetIndex(i int) {
b.index = i
}
func (b *Body) SetName(name string) {
b.name = name
}
func (b *Body) Name() string {
return b.name
}
func (b *Body) Index() int {
return b.index
}
func (b *Body) Material() *material.Material {
return b.material
}
func (b *Body) SetAllowSleep(state bool) {
b.allowSleep = state
}
func (b *Body) AllowSleep() bool {
return b.allowSleep
}
func (b *Body) SleepSpeedLimit() float32 {
return b.sleepSpeedLimit
}
func (b *Body) SleepState() BodySleepState {
return b.sleepState
}
// SetBodyType sets the body type.
func (b *Body) SetBodyType(bodyType BodyType) {
// Do nothing if body is already of the specified bodyType
if b.bodyType == bodyType {
return
}
// If we want the body to be static we need to zero its mass
if bodyType == Static {
b.mass = 0
}
// Temporarily save original body type and update current body type
origBodyType := b.bodyType
b.bodyType = bodyType
// If changed body type to or from Static then we need to update mass properties
if origBodyType == Static || b.bodyType == Static {
b.UpdateMassProperties()
}
}
func (b *Body) BodyType() BodyType {
return b. bodyType
}
func (b *Body) SetWakeUpAfterNarrowphase(state bool) {
b.wakeUpAfterNarrowphase = state
}
func (b *Body) WakeUpAfterNarrowphase() bool {
return b.wakeUpAfterNarrowphase
}
// ApplyVelocityDeltas adds the specified deltas to the body's linear and angular velocities.
func (b *Body) ApplyVelocityDeltas(linearD, angularD *math32.Vector3) {
b.velocity.Add(linearD.Multiply(b.linearFactor))
b.angularVelocity.Add(angularD.Multiply(b.angularFactor))
}
// ClearForces clears all forces on the body.
func (b *Body) ClearForces() {
b.force.Zero()
b.torque.Zero()
}
func (b *Body) InvMassEff() float32 {
return b.invMassEff
}
func (b *Body) InvRotInertiaWorldEff() *math32.Matrix3 {
return b.invRotInertiaWorldEff
}
func (b *Body) Position() math32.Vector3 {
return *b.position
}
func (b *Body) Quaternion() *math32.Quaternion {
return b.quaternion.Clone()
}
func (b *Body) SetVelocity(vel *math32.Vector3) {
b.velocity = vel
}
func (b *Body) Velocity() math32.Vector3 {
return *b.velocity
}
func (b *Body) SetAngularVelocity(vel *math32.Vector3) {
b.angularVelocity = vel
}
func (b *Body) AngularVelocity() math32.Vector3 {
return *b.angularVelocity
}
func (b *Body) Force() math32.Vector3 {
return *b.force
}
func (b *Body) Torque() math32.Vector3 {
return *b.torque
}
func (b *Body) SetLinearDamping(d float32) {
b.linearDamping = d
}
func (b *Body) LinearDamping() float32 {
return b.linearDamping
}
func (b *Body) SetAngularDamping(d float32) {
b.angularDamping = d
}
func (b *Body) AngularDamping() float32 {
return b.angularDamping
}
func (b *Body) ApplyDamping(dt float32) {
b.velocity.MultiplyScalar(math32.Pow(1.0 - b.linearDamping, dt))
b.angularVelocity.MultiplyScalar(math32.Pow(1.0 - b.angularDamping, dt))
}
func (b *Body) SetLinearFactor(factor *math32.Vector3) {
b.linearFactor = factor
}
func (b *Body) LinearFactor() math32.Vector3 {
return *b.linearFactor
}
func (b *Body) SetAngularFactor(factor *math32.Vector3) {
b.angularFactor = factor
}
func (b *Body) AngularFactor() math32.Vector3 {
return *b.angularFactor
}
// SetFixedRotation specifies whether the body should rotate.
func (b *Body) SetFixedRotation(state bool) {
// Do nothing if the fixedRotation flag already has the specified value
if b.fixedRotation == state {
return
}
// Set the fixedRotation flag and update mass properties
b.fixedRotation = state
b.UpdateMassProperties()
}
// WakeUp wakes the body up.
func (b *Body) WakeUp() {
state := b.sleepState
b.sleepState = Awake
b.wakeUpAfterNarrowphase = false
if state == Sleeping {
b.Dispatch(WakeUpEvent, nil)
}
}
// Sleep forces the body to sleep.
func (b *Body) Sleep() {
b.sleepState = Sleeping
b.velocity.Set(0, 0, 0)
b.angularVelocity.Set(0, 0, 0)
b.wakeUpAfterNarrowphase = false
}
// Called every timestep to update internal sleep timer and change sleep state if needed.
// time: The world time in seconds
func (b *Body) SleepTick(time float32) {
if b.allowSleep {
speedSquared := b.velocity.LengthSq() + b.angularVelocity.LengthSq()
speedLimitSquared := math32.Pow(b.sleepSpeedLimit, 2)
if b.sleepState == Awake && speedSquared < speedLimitSquared {
b.sleepState = Sleepy
b.timeLastSleepy = time
b.Dispatch(SleepyEvent, nil)
} else if b.sleepState == Sleepy && speedSquared > speedLimitSquared {
b.WakeUp() // Wake up
} else if b.sleepState == Sleepy && (time-b.timeLastSleepy) > b.sleepTimeLimit {
b.Sleep() // Sleeping
b.Dispatch(SleepEvent, nil)
}
}
}
// If checkSleeping is true then returns false if both bodies are currently sleeping.
func (b *Body) Sleeping() bool {
return b.sleepState == Sleeping
}
// CollidableWith returns whether the body can collide with the specified body.
func (b *Body) CollidableWith(other *Body) bool {
if (b.colFilterGroup & other.colFilterMask == 0) ||
(other.colFilterGroup & b.colFilterMask == 0) ||
(b.bodyType == Static) && (other.bodyType == Static) {
return false
}
return true
}
func (b *Body) CollisionResponse() bool {
return b.colResponse
}
// PointToLocal converts a world point to local body frame. TODO maybe move to Node
func (b *Body) PointToLocal(worldPoint *math32.Vector3) math32.Vector3 {
return *worldPoint.Clone().Sub(b.position).ApplyQuaternion(b.quaternion.Conjugate())
}
// VectorToLocal converts a world vector to local body frame. TODO maybe move to Node
func (b *Body) VectorToLocal(worldVector *math32.Vector3) math32.Vector3 {
return *worldVector.Clone().ApplyQuaternion(b.quaternion.Conjugate())
}
// PointToWorld converts a local point to world frame. TODO maybe move to Node
func (b *Body) PointToWorld(localPoint *math32.Vector3) math32.Vector3 {
return *localPoint.Clone().ApplyQuaternion(b.quaternion).Add(b.position)
}
// VectorToWorld converts a local vector to world frame. TODO maybe move to Node
func (b *Body) VectorToWorld(localVector *math32.Vector3) math32.Vector3 {
return *localVector.Clone().ApplyQuaternion(b.quaternion)
}
// UpdateEffectiveMassProperties
// If the body is sleeping, it should be immovable and thus have infinite mass during solve.
// This is solved by having a separate "effective mass" and other "effective" properties
func (b *Body) UpdateEffectiveMassProperties() {
if b.sleepState == Sleeping || b.bodyType == Kinematic {
b.invMassEff = 0
b.invRotInertiaEff.Zero()
b.invRotInertiaWorldEff.Zero()
} else {
b.invMassEff = b.invMass
b.invRotInertiaEff.Copy(b.invRotInertia)
b.invRotInertiaWorldEff.Copy(b.invRotInertiaWorld)
}
}
// UpdateMassProperties
// Should be called whenever you change the body shape or mass.
func (b *Body) UpdateMassProperties() {
if b.mass > 0 {
b.invMass = 1.0 / b.mass
} else {
b.invMass = 0
}
if b.fixedRotation || b.bodyType == Static {
b.rotInertia.Zero()
b.invRotInertia.Zero()
} else {
*b.rotInertia = b.GetGeometry().RotationalInertia(b.mass)
b.rotInertia.MultiplyScalar(10) // multiply by high density // TODO remove this ?
b.invRotInertia.GetInverse(b.rotInertia) // Note: rotInertia is always positive definite and thus always invertible
}
b.UpdateInertiaWorld(true)
}
// Update .inertiaWorld and .invRotInertiaWorld
func (b *Body) UpdateInertiaWorld(force bool) {
iRI := b.invRotInertia
// If rotational inertia M = s*I, where I is identity and s a scalar, then
// R*M*R' = R*(s*I)*R' = s*R*I*R' = s*R*R' = s*I = M
// where R is the rotation matrix.
// In other words, we don't have to do the transformation if all diagonal entries are equal.
if iRI[0] != iRI[4] || iRI[4] != iRI[8] || force {
// iRIW = R * iRI * R'
m1 := math32.NewMatrix3().MakeRotationFromQuaternion(b.quaternion)
m2 := m1.Clone().Transpose()
m2.Multiply(iRI)
b.invRotInertiaWorld.MultiplyMatrices(m2, m1)
}
}
// Forces from a force field need to be multiplied by mass.
func (b *Body) ApplyForceField(force *math32.Vector3) {
b.force.Add(force.MultiplyScalar(b.mass))
}
// Apply force to a world point.
// This could for example be a point on the Body surface.
// Applying force this way will add to Body.force and Body.torque.
// relativePoint: A point relative to the center of mass to apply the force on.
func (b *Body) ApplyForce(force, relativePoint *math32.Vector3) {
if b.bodyType != Dynamic { // Needed?
return
}
// Add linear force
b.force.Add(force) // TODO shouldn't rotational momentum be subtracted from linear momentum?
// Add rotational force
b.torque.Add(math32.NewVec3().CrossVectors(relativePoint, force))
}
// Apply force to a local point in the body.
// force: The force vector to apply, defined locally in the body frame.
// localPoint: A local point in the body to apply the force on.
func (b *Body) ApplyLocalForce(localForce, localPoint *math32.Vector3) {
if b.bodyType != Dynamic {
return
}
// Transform the force vector to world space
worldForce := b.VectorToWorld(localForce)
relativePointWorld := b.VectorToWorld(localPoint)
b.ApplyForce(&worldForce, &relativePointWorld)
}
// Apply impulse to a world point.
// This could for example be a point on the Body surface.
// An impulse is a force added to a body during a short period of time (impulse = force * time).
// Impulses will be added to Body.velocity and Body.angularVelocity.
// impulse: The amount of impulse to add.
// relativePoint: A point relative to the center of mass to apply the force on.
func (b *Body) ApplyImpulse(impulse, relativePoint *math32.Vector3) {
if b.bodyType != Dynamic {
return
}
// Compute point position relative to the body center
r := relativePoint
// Compute produced central impulse velocity
velo := impulse.Clone().MultiplyScalar(b.invMass)
// Add linear impulse
b.velocity.Add(velo)
// Compute produced rotational impulse velocity
rotVelo := math32.NewVec3().CrossVectors(r, impulse)
rotVelo.ApplyMatrix3(b.invRotInertiaWorld)
// Add rotational Impulse
b.angularVelocity.Add(rotVelo)
}
// Apply locally-defined impulse to a local point in the body.
// force: The force vector to apply, defined locally in the body frame.
// localPoint: A local point in the body to apply the force on.
func (b *Body) ApplyLocalImpulse(localImpulse, localPoint *math32.Vector3) {
if b.bodyType != Dynamic {
return
}
// Transform the force vector to world space
worldImpulse := b.VectorToWorld(localImpulse)
relativePointWorld := b.VectorToWorld(localPoint)
b.ApplyImpulse(&worldImpulse, &relativePointWorld)
}
// Get world velocity of a point in the body.
func (b *Body) GetVelocityAtWorldPoint(worldPoint *math32.Vector3) *math32.Vector3 {
r := math32.NewVec3().SubVectors(worldPoint, b.position)
r.CrossVectors(b.angularVelocity, r)
r.Add(b.velocity)
return r
}
// Move the body forward in time.
// dt: Time step
// quatNormalize: Set to true to normalize the body quaternion
// quatNormalizeFast: If the quaternion should be normalized using "fast" quaternion normalization
func (b *Body) Integrate(dt float32, quatNormalize, quatNormalizeFast bool) {
// Save previous position and rotation
b.prevPosition.Copy(b.position)
b.prevQuaternion.Copy(b.quaternion)
// If static or sleeping - skip
if !(b.bodyType == Dynamic || b.bodyType == Kinematic) || b.sleepState == Sleeping {
return
}
// Integrate force over mass (acceleration) to obtain estimate for instantaneous velocities
iMdt := b.invMass * dt
b.velocity.X += b.force.X * iMdt * b.linearFactor.X
b.velocity.Y += b.force.Y * iMdt * b.linearFactor.Y
b.velocity.Z += b.force.Z * iMdt * b.linearFactor.Z
// Integrate inverse angular mass times torque to obtain estimate for instantaneous angular velocities
e := b.invRotInertiaWorld
tx := b.torque.X * b.angularFactor.X
ty := b.torque.Y * b.angularFactor.Y
tz := b.torque.Z * b.angularFactor.Z
b.angularVelocity.X += dt * (e[0]*tx + e[3]*ty + e[6]*tz)
b.angularVelocity.Y += dt * (e[1]*tx + e[4]*ty + e[7]*tz)
b.angularVelocity.Z += dt * (e[2]*tx + e[5]*ty + e[8]*tz)
// Integrate velocity to obtain estimate for position
b.position.X += b.velocity.X * dt
b.position.Y += b.velocity.Y * dt
b.position.Z += b.velocity.Z * dt
// Integrate angular velocity to obtain estimate for rotation
ax := b.angularVelocity.X * b.angularFactor.X
ay := b.angularVelocity.Y * b.angularFactor.Y
az := b.angularVelocity.Z * b.angularFactor.Z
bx := b.quaternion.X
by := b.quaternion.Y
bz := b.quaternion.Z
bw := b.quaternion.W
halfDt := dt * 0.5
b.quaternion.X += halfDt * (ax*bw + ay*bz - az*by)
b.quaternion.Y += halfDt * (ay*bw + az*bx - ax*bz)
b.quaternion.Z += halfDt * (az*bw + ax*by - ay*bx)
b.quaternion.W += halfDt * (-ax*bx - ay*by - az*bz)
// Normalize quaternion
b.quaternion.Normalize()
//if quatNormalize { // TODO future
// if quatNormalizeFast {
// b.quaternion.NormalizeFast()
// } else {
// b.quaternion.Normalize()
// }
//}
// Update position and rotation of Node (containing visual representation of the body)
b.GetNode().SetPositionVec(b.position)
b.GetNode().SetRotationQuat(b.quaternion)
b.aabbNeedsUpdate = true
// Update world inertia
b.UpdateInertiaWorld(false)
}