anchor.diff:  open TweakBarGuiViewModel
   open System.Reactive.Linq
   open System.Linq
  +open LOD
  +open LODCache
  +open Terrain
   
   //let transferMesh (m:mesh) =
   //    let vbos = Array.zeroCreate<int> 2
  
positive.code:         let projectionMatrix = Matrix4.CreatePerspectiveFieldOfView(2.0f, float32 aspectRatio, 0.1f, 1000.0f)
          let cameraMatrix = Matrix4.LookAt(cameraPosition, Vector3.Zero, Vector3.UnitY)
  
          let blinnMaterial = vm.BlinnMaterial
  
          let staticRenderContext = {
  
negative.code:         SpecularColor = new Vector3(1.0f, 1.0f, 1.0f); 
          SpecularExp = 150.0 }
      let defaultVm = { IntegrationSpeed = 1.0; BlinnMaterial = defaultBlinnMaterial }
      let tree = makeTerrainLodTree
      let nodeCache = makeCache allocate
  
      let mutable vm : ViewModel = defaultVm
      let mutable cameraPosition : Vector3 = new Vector3(0.0f, 100.0f, 50.0f)
  