Blitz3D+ Command Reference

PhysicsQueryFraction# ( query,index )

Parameters

query - query handle

index - one-based hit index

Description

Returns how far along a ray or sweep a hit occurred, from 0 to 1.

Returns the copied collision fraction along the requested ray/sweep translation, between 0 and 1. Multiply it by translation length to obtain travel distance; it is not time in seconds. Zero-fraction native hits are excluded by these cast commands. Overlap/AABB hits have no fraction and raise an error.

Results are copied. They survive StepPhysics and other queries until this query runs successfully again or is freed. Failed runs preserve the previous results. Freeing the owning world frees its queries. Invalid/stale/wrong-kind handles and invalid hit indices raise runtime errors.


See also: CreatePhysicsQuery, PhysicsQueryFilter, PhysicsQueryTarget, QueryPhysicsRay, QueryPhysicsSphere, PhysicsQueryLimit.

Example

; PhysicsQueryFraction Example
; ----------------------------

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

Const PHYSICS_STATIC=0
Const PHYSICS_DYNAMIC=2

camera=CreateCamera()
PositionEntity camera,0,7,-8
RotateEntity camera,40,0,0

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 ring of crates to aim at
For i=1 To 8
    crate=CreateCube()
    ScaleEntity crate,0.5,0.5,0.5
    PositionEntity crate,Cos(i*45)*4,0.5,Sin(i*45)*4
    EntityColor crate,255,120,70
    crate_body=CreatePhysicsBody(world,crate,PHYSICS_STATIC)
    crate_shape=PhysicsBodyBox(crate_body,1,1,1)
Next

; A query object runs searches and keeps a copy of their results
query=CreatePhysicsQuery(world)

; Start aimed at a crate
angle#=45

While Not KeyDown(1)

    ; A and D sweep the ray around the centre
    If KeyDown(30) Then angle=angle+1.5
    If KeyDown(32) Then angle=angle-1.5
    dx#=Cos(angle)*6
    dz#=Sin(angle)*6

    StepPhysics world,1.0/60.0,4

    ; Cast a ray 6 m out from the centre, half a metre above the floor
    hits=QueryPhysicsRay(query,0,0.5,0,dx,0,dz)

    ; 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

    ; Draw the ray from the centre to the first hit, or to its full length
    CameraProject camera,0,0.5,0
    start_x=ProjectedX()
    start_y=ProjectedY()
    If hits>0
        CameraProject camera,PhysicsQueryX(query,1),PhysicsQueryY(query,1),PhysicsQueryZ(query,1)
    Else
        CameraProject camera,dx,0.5,dz
    EndIf
    Line start_x,start_y,ProjectedX(),ProjectedY()

    Text 0,0,"Arrow keys: move camera   A / D: sweep the ray   Esc: exit"
    If hits>0
        Text 0,20+0,"PhysicsQueryFraction(query,1) = "+PhysicsQueryFraction(query,1)
        Text 0,20+20,"The hit is "+PhysicsQueryFraction(query,1)*6+" m along the 6 m ray"
    Else
        Text 0,20,"The ray hits nothing"
    EndIf

    Flip

Wend

FreePhysicsWorld world
End

Index