Car wheel track

Blitz3D Forums/Blitz3D Programming/Car wheel track
Mike0101
(Posted 2009) [#1]
Here is a small sample of wheel track. Easy code
If you can make better, feel free.

; With a transparent background texture the paralell wheeltrack is perfect, this sample has no texture
; structure for wheeltruck
Type wheeltrack
  Field trail_mesh%, trail_surf%, trail_vert%
  Field timer%
  Field add_cnt%, add_flag%
End Type

Global k.wheeltrack

Graphics3D 800,600,32,0


;plane with a simple texture
grid_tex=CreateTexture( 32,32,8 )
ScaleTexture grid_tex,10,10
SetBuffer TextureBuffer( grid_tex )
Color 0,64,64:Rect 0,0,32,32
Color 0,255,255:Rect 0,0,32,32,False
SetBuffer BackBuffer()

grid_plane=CreatePlane()
EntityTexture grid_plane,grid_tex
EntityBlend grid_plane,1
EntityFX grid_plane,1



Global trail_mesh
Global trail_brush, trail_surf, trial_vert


; a global brush for wheeltrack mesh
trail_brush=CreateBrush()
BrushAlpha trail_brush,.51
; here you can apply a texture


; the vehicle
bike=CreateCube()
ScaleMesh bike,1.2,1,2
PositionEntity bike,20,1,20

; the camera target for chase cam.
target=CreatePivot( bike )
PositionEntity target,0,5,-12


create_wheeltrack(20,1,20,0,0,0)


camera=CreateCamera()


; main cycle
While Not KeyHit(1)
  
	If KeyHit(17)
		wire=Not wire
		WireFrame wire
	EndIf
	
	
	turn=0
	If KeyDown(203) turn=3
	If KeyDown(205) turn=-3
	
	If turn
		TurnEntity bike,0,turn,0
	EndIf
	
	MoveEntity bike,0,0,.5


      update_wheeltrack(bike%)

	
	UpdateWorld
	
	; the chasecam update
 	dx#=EntityX( target,True )-EntityX( camera )
	dy#=EntityY( target,True )-EntityY( camera )
	dz#=EntityZ( target,True )-EntityZ( camera )
	TranslateEntity camera,dx*.1,dy*.1,dz*.1
	PointEntity camera,bike
	
	RenderWorld
	Flip

Wend
End


Function update_wheeltrack(bike%)

	k\add_cnt=k\add_cnt+1
			If k\add_cnt>=4
				k\add_cnt=0
				k\add_flag=True
			Else
				k\add_flag=False
			EndIf
          If k\add_flag

        TFormPoint 1,0,0,bike,0
 		AddVertex k\trail_surf,TFormedX(),0.1,TFormedZ() ,0,0
         TFormPoint -1,0,0,bike,0
		AddVertex k\trail_surf,TFormedX(),0.1,TFormedZ() ,0,1

		AddTriangle k\trail_surf,k\trail_vert,k\trail_vert+2,k\trail_vert+3
		AddTriangle k\trail_surf,k\trail_vert,k\trail_vert+3,k\trail_vert+1
		AddTriangle k\trail_surf,k\trail_vert,k\trail_vert+3,k\trail_vert+2
		AddTriangle k\trail_surf,k\trail_vert,k\trail_vert+1,k\trail_vert+3
		k\trail_vert=k\trail_vert+2

      EndIf


         ; clear and remake
      If k\timer < MilliSecs() 
             FreeEntity  k\trail_mesh
                      Delete k
             create_wheeltrack(EntityX(bike,1), EntityY(bike,1),EntityZ(bike,1), EntityPitch(bike,1),EntityYaw(bike,1), EntityRoll(bike,1))
      EndIf


End Function

Function create_wheeltrack(x#,y#,z#, rx#,ry#,rz#)
  k.wheeltrack=New wheeltrack
 k\trail_mesh=CreateMesh()
 PositionMesh k\trail_mesh,x,y,z
  RotateMesh k\trail_mesh,rx,ry,rz
 k\trail_surf=CreateSurface( k\trail_mesh,trail_brush )
 AddVertex k\trail_surf,x+2,0.1, z , 0,0
 AddVertex k\trail_surf,  x,   0.1, z,  0,1
 AddVertex k\trail_surf, x+2,0.1, z, 0,0
 AddVertex k\trail_surf,  x,    0.1, z, 0,1
 AddTriangle k\trail_surf,0,2,3
 AddTriangle k\trail_surf,0,3,1
 AddTriangle k\trail_surf,0,3,2
 AddTriangle k\trail_surf,0,1,3
 k\trail_vert=2
 ; this is important,  each 4 seconds the wheeltrack is clear and create a new because of lower polygon number
  k\timer=MilliSecs() + 4000
End Function