Blitz3D+ Command Reference

PhysicsBodyEventTag ( world,index )

Parameters

world - world handle

index - one-based body-event index

Description

Returns the signed application body tag captured at the event step.

Later tag edits or body deletion do not change it. Body event capture is opt-in per world. The copied batch is replaced after each StepPhysics; it is independent of held query snapshots. Awake dynamic and kinematic bodies can emit entries, including zero-motion awake bodies; static bodies do not. A fell-asleep entry marks that transition, and sleeping bodies normally leave the stream. Entries are sorted by wrapper body handle, not creation order. Tags and final native world poses are copied after continuous-collision correction; after deletion live body/entity getters return zero. Event indices belong to one step. A kinematic native pose can differ from its authored entity target while integration approaches it.

Invalid/stale/wrong-kind handles, invalid indices or unavailable payload fields raise runtime errors.

Requires Extended mode.

See also: QueryPhysicsBodyContacts, QueryPhysicsShapeContacts, QueryPhysicsSensor, CountPhysicsQueryManifolds, PhysicsBodyEvents.

Example

; PhysicsBodyEventTag Example
; ---------------------------
; Requires Extended mode.

Graphics3D 640,480,0,2
SetBuffer BackBuffer()

Const PHYSICS_STATIC=0
Const PHYSICS_DYNAMIC=2
Const CRATE_COUNT=12

SeedRnd MilliSecs()

camera=CreateCamera()
PositionEntity camera,0,6,-12
RotateEntity camera,20,0,0

light=CreateLight()
RotateEntity light,45,-30,0
AmbientLight 60,60,60

; An independent Box3D world with standard gravity
world=CreatePhysicsWorld()

; Blue static floor
ground=CreateCube()
ScaleEntity ground,6,0.5,6
PositionEntity ground,0,-0.5,0
EntityColor ground,80,160,255
ground_body=CreatePhysicsBody(world,ground,PHYSICS_STATIC)
ground_shape=PhysicsBodyBox(ground_body,12,1,12)

; A pile of crates, dropped from random heights
Dim crates(CRATE_COUNT)
Dim crate_bodies(CRATE_COUNT)
For i=1 To CRATE_COUNT
    crates(i)=CreateCube()
    ScaleEntity crates(i),0.5,0.5,0.5
    crate_bodies(i)=CreatePhysicsBody(world,crates(i),PHYSICS_DYNAMIC)
    crate_shape=PhysicsBodyBox(crate_bodies(i),1,1,1)

    ; Number each crate with a body tag
    SetPhysicsBodyTag crate_bodies(i),i
Next
DropPile()

; Copy body movement and sleep events after every step
PhysicsBodyEvents world,True

; A yellow marker points at the crate the events pick out
marker=CreateCone(8)
ScaleEntity marker,0.3,0.4,0.3
RotateEntity marker,180,0,0
EntityColor marker,255,230,60
HideEntity marker

While Not KeyDown(1)

    ; R drops the pile again
    If KeyHit(19) Then DropPile()

    StepPhysics world,1.0/60.0,4

    ; The event keeps the tag the body had when the event happened
    For e=1 To CountPhysicsBodyEvents(world)
        If PhysicsBodyEventFellAsleep(world,e)
            news$="Crate "+PhysicsBodyEventTag(world,e)+" fell asleep"
            sleeper_entity=PhysicsBodyEventEntity(world,e)
        EndIf
    Next
    If sleeper_entity
        PositionEntity marker,EntityX(sleeper_entity),EntityY(sleeper_entity)+1.2,EntityZ(sleeper_entity)
        ShowEntity marker
    EndIf

    ; Orange crates are awake, grey crates are asleep
    For i=1 To CRATE_COUNT
        If PhysicsBodyIsAwake(crate_bodies(i))
            EntityColor crates(i),255,120,70
        Else
            EntityColor crates(i),150,150,150
        EndIf
    Next

    ; Arrow keys move the camera
    If KeyDown(200) Then MoveEntity camera,0,0,0.1
    If KeyDown(208) Then MoveEntity camera,0,0,-0.1
    If KeyDown(203) Then TurnEntity camera,0,1,0
    If KeyDown(205) Then TurnEntity camera,0,-1,0

    RenderWorld

    Text 0,0,"Arrow keys: move camera   R: drop again   Esc: exit"
    Text 0,20,"PhysicsBodyEventTag: "+news

    Flip

Wend

FreePhysicsWorld world
End

Function DropPile()
    For i=1 To CRATE_COUNT
        ResetPhysicsBody crate_bodies(i),Rnd(-1.5,1.5),2+i*0.8,Rnd(-1.5,1.5),0,Rnd(Pi),0
    Next
End Function

Index