Blitz3D+ Command Reference

CollisionNZ# ( entity,collision_index )

Parameters

entity - entity handle
collision_index - index of the collision, from 1 to CountCollisions( entity )

Description

Returns the z component of the normal of one of an entity's collisions.

The normal is a unit-length vector pointing directly away from the surface the entity hit in collision number collision_index of the last UpdateWorld. Together the three components tell you which way the touched face points - reflect the entity's velocity off it for a bounce, or feed it to AlignToVector to tilt a vehicle to the ground it landed on.

In debug mode an index outside 1...CountCollisions( entity ) is a runtime error.

See also: CollisionNX, CollisionNY, CollisionZ, CountCollisions, AlignToVector.

Example

; CollisionNZ Example
; -------------------

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

; Collision type ids
type_player=1
type_scenery=2

; NOTE: fixed overhead camera - the arrow keys steer the PLAYER, not the camera
camera=CreateCamera()
PositionEntity camera,0,13,-13
RotateEntity camera,45,0,0

light=CreateLight()
RotateEntity light,60,30,0

floor=CreatePlane()
EntityColor floor,70,110,70

; The player ball is the collision SOURCE, so it needs an ellipsoid radius
player=CreateSphere()
EntityColor player,220,60,60
PositionEntity player,0,1,0
EntityRadius player,1
EntityType player,type_player

; Two walls meeting in a corner, plus a crate
wall1=CreateCube()
ScaleEntity wall1,7,1.5,0.5
PositionEntity wall1,0,1.5,7
EntityColor wall1,150,150,160
EntityType wall1,type_scenery

wall2=CreateCube()
ScaleEntity wall2,0.5,1.5,7
PositionEntity wall2,7,1.5,0
EntityColor wall2,150,150,160
EntityType wall2,type_scenery

crate=CreateCube()
ScaleEntity crate,1.2,1.2,1.2
PositionEntity crate,-4,1.2,3
EntityColor crate,200,160,60
EntityType crate,type_scenery

; Ellipsoid-to-polygon collisions with a sliding response
Collisions type_player,type_scenery,2,2

While Not KeyDown(1)

    ; Arrow keys steer the player ball
    If KeyDown(200) Then MoveEntity player,0,0,0.1
    If KeyDown(208) Then MoveEntity player,0,0,-0.1
    If KeyDown(203) Then MoveEntity player,-0.1,0,0
    If KeyDown(205) Then MoveEntity player,0.1,0,0

    ; UpdateWorld performs the collision checks and the slide response
    UpdateWorld

    RenderWorld

    Text 0,0,"Arrow keys: drive the ball into the walls and crate   Esc: exit"
    ; CollisionNZ is the z part of the collision normal - it points back at the ball
    If CountCollisions(player)>0
        Text 0,20,"CollisionNZ(player,1) = "+CollisionNZ(player,1)
        Text 0,40,"(CollisionNX: "+CollisionNX(player,1)+"   CollisionNY: "+CollisionNY(player,1)+")"
        Text 0,60,"The back wall gives NZ = -1; the side wall gives NZ = 0"
    Else
        Text 0,20,"CollisionNZ: no collisions this frame - push against something"
    EndIf

    Flip

Wend

End

Index