anchor.diff:  
   (defvar *camera-uset* (make-instance 'camera))
   (defvar *model-uset* (make-instance 'model))
  +(defvar *light-uset* (make-instance 'light))
   
   (defun draw-window (win)
     (when (exposed win)
  
positive.code:                            :shaders (list (make-instance 'lpsg:shader
                                                           :shader-type :vertex-shader
                                                           :source *vertex-shader-source*
                                                           :usets '(camera model))
                                            (make-instance 'lpsg:shader
                                                           :shader-type :fragment-shader
                                                           :source *fragment-shader-source*
  
negative.code:   // add a temporary model and view transform
    vec4 modelPos = cameraMatrix * modelMatrix * in_Position;
    gl_Position = projectionMatrix * modelPos;
    float intense = max(dot(in_Normal, -lightDir.xyz), 0.0);
    theColor = intense * in_Color;
  }
  ")
  