; TFormedZ Example
; ----------------

; The TForm commands (TFormPoint, TFormVector, TFormNormal) store
; their result internally; TFormedZ reads back the z component.
; Here TFormPoint tracks the muzzle tip of a spinning turret, and
; TFormedZ supplies the marker's world z coordinate.

Graphics3D 640,480
SetBuffer BackBuffer()

camera=CreateCamera()
PositionEntity camera,0,3,-6
RotateEntity camera,20,0,0

light=CreateLight()
RotateEntity light,30,40,0

; A base and a long turret barrel on top of it
base=CreateCylinder()
ScaleEntity base,1,0.4,1
EntityColor base,110,110,130

turret=CreateCube()
ScaleMesh turret,0.25,0.25,1.5 ; barrel runs from local z -1.5 to 1.5
PositionEntity turret,0,1,0
EntityColor turret,90,180,90

; The marker lives in WORLD space and follows the muzzle tip
marker=CreateSphere()
ScaleEntity marker,0.15,0.15,0.15
EntityColor marker,255,255,0
EntityFX marker,1

While Not KeyDown(1)

    TurnEntity turret,0,1.5,0

    ; Transform the local muzzle point (0,0,1.5) into world space
    TFormPoint 0,0,1.5,turret,0

    ; Read back the result - TFormedZ is the documented command
    z#=TFormedZ()
    PositionEntity marker,TFormedX(),TFormedY(),z

    ; 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   Esc: exit"
    Text 0,20,"TFormedZ() = "+z
    Text 0,40,"The marker's world z swings as the turret spins"

    Flip

Wend

End