Function mtrr(tsix,tsiz,timg)
  mesh = CreateMesh()
  brus = CreateBrush()
  BrushTexture brus,tex
  surf = CreateSurface(mesh,brus)

  SetBuffer ImageBuffer(timg)
  LockBuffer ImageBuffer(timg)
  For z = 0 To (tsiz)
    For x = 0 To (tsix)
      rgb = ReadPixelFast(x,z)
      y# = Float((rgb And $FF0000) / $10000)
      y# = y# * (4.0/255.0)

      terrmap(x,z,0) = AddVertex(surf, x,y#,z)
      terrmap(x,z,1) = AddVertex(surf, x,y#,z)

      If (x>0) And (z>0) Then
        AddTriangle(surf, terrmap(x, z, 0), terrmap(x-1, z, 0), terrmap(x-1, z-1, 0))
        AddTriangle(surf, terrmap(x, z, 1), terrmap(x, z-1, 1), terrmap(x-1, z-1, 1))
      EndIf
    Next
  Next
  UnlockBuffer ImageBuffer(timg)
  SetBuffer BackBuffer()

  UpdateNormals mesh
  FlipMesh mesh
  ScaleMesh mesh, 0.25,1,0.25

  EntityFX mesh,16
  EntityPickMode mesh, 2
  Return mesh
End Function

Graphics3D 800,600,32,2

Global GameSpeed%=60
Global Screenwidth%=GraphicsWidth()
Global Screenheight%=GraphicsHeight()
Global FramePeriod%=1000/GameSpeed
Global FrameTime%=MilliSecs()-FramePeriod
Global DeltaTimeOld%

hm=LoadImage("heightmap.bmp")
tx=LoadTexture("grass.png")

mesh=CreatePatch(32,hm,tx)
ScaleMesh mesh,16,16,16
EntityFX mesh,2
light=CreateLight(1)

cam=CreateCamera()
MoveEntity cam,8,8,-2
CameraRange cam,0.1,1000
CameraClsColor cam,150,200,255

MoveMouse 400,300

While Not KeyHit(1)
   
   ; Frametween calculation
   Local FrameElapsed%,FrameTicks%,FrameTween#,t%
   Repeat FrameElapsed=MilliSecs()-FrameTime Until FrameElapsed
   FrameTicks=FrameElapsed/FramePeriod
   FrameTween=Float(FrameElapsed Mod FramePeriod)/Float(FramePeriod)
   
   ; Frametween loop
   For t=1 To FrameTicks
      
      ; Frametween Captureworld
      FrameTime=FrameTime+FramePeriod : If t=FrameTicks Then CaptureWorld
      
      If KeyHit(57) Then wf=1-wf : WireFrame wf
      
      FreeCam(cam,85,0.1)
      
   Next
   
   RenderWorld
   
   Flip 0
   
Wend

End


Function CreatePatch(size%=32,heightmap%,tex%)
   
   Local x%,z%,h%,c%
   Local vx#,vz#,u#,v#,vertex%
   Local v0%,v1%,v2%,v3%
   
   Local mesh%=CreateMesh()
   Local brush%=CreateBrush() : BrushTexture brush,tex
   Local surf%=CreateSurface(mesh,brush)
   Local buffer%=ImageBuffer(heightmap)
   
   LockBuffer buffer
   
   For z=0 To size
      
      For x=0 To size
         
         ; calculate vertex coordinates / texture coordinates
         vx=1.0/size*x
         vz=1.0/size*z
         u=x*1.0/size
         v=z*1.0/size
         
         h=(ReadPixelFast(x,z,buffer) And $ff0000)/$10000
         
         
         ; place vertex
         vertex=AddVertex(surf,vx,h/512.0,vz,u,v)
         
         ; set vertex color and texture coordinates
         VertexColor surf,vertex,255,255,255,1
         
         ; set triangles
         If z<size And x<size Then
            
            v0=x+((size+1)*z)
            v1=x+((size+1)*z)+(size+1)
            v2=(x+1)+((size+1)*z)
            v3=(x+1)+((size+1)*z)+(size+1)
            
            AddTriangle(surf,v0,v1,v2)
            AddTriangle(surf,v2,v1,v3)
            
         EndIf
         
      Next
      
   Next
   
   UnlockBuffer buffer
   
   UpdateNormals mesh
   
   Return mesh
   
End Function

Function FreeCam(camera%,maxpitch#=85.0,movespeed#,rotspeed#=16.666,rotfloat#=8.0)
   
   Local movex#,movez#,dx#,dy#,dk#,dt%,t%
   Local pitch#
   
   ; Arrows = Move
   movex=KeyDown(205)-KeyDown(203)
   movez=KeyDown(200)-KeyDown(208)
   
   ; smooth movement
   t=MilliSecs() : dt=t-DeltaTimeOld : DeltaTimeOld=t : dk=Float(dt)/rotspeed
   dx=(Screenwidth/2-MouseX())*0.01*dk : dy=(Screenheight/2-MouseY())*0.01*dk
   TurnEntity camera,-dy,dx*0.1*dk*rotfloat,0
   
   ; limit pitch
   pitch=EntityPitch(camera,1) : If pitch>maxpitch Then pitch=maxpitch Else If pitch<-maxpitch Then pitch=-maxpitch
   
   ; rotate and move
   RotateEntity camera,pitch,EntityYaw(camera,1),0,1   
   MoveEntity camera,movex*movespeed,0,movez*movespeed
   
End Function