anchor.diff:  
               return V4d(v.c.XYZ * diffuse, v.c.W)
           }
  +           
  +    type InstanceVertex = { 
  +        [<Position>] pos : V4d 
  +        [<Semantic("ZZZInstanceTrafo")>] trafo : M44d
  +    }
  +
  +    let instanceTrafo (v : InstanceVertex) =
  +        vertex {
  +            return { v with pos = v.trafo * v.pos }
  +        }
                
   module Shadows = 
   
  
positive.code: 
      let win = openWindow()
  
      let shadowMapSize = Mod.init (V2i(1024, 1024))
  
      let shadowCam = CameraView.lookAt (V3d.III * 2.5) V3d.Zero V3d.OOI
      let shadowProj = Frustum.perspective 60.0 0.1 10.0 1.0
  
negative.code:     let rotation =
          controller {
              let! dt = differentiate Mod.time
              return fun f -> f + dt.TotalSeconds * 0.6
          }
      let angle = AFun.integrate rotation 0.0
      let lightSpaceView =
  