anchor.diff:    (glutil:with-transform (matrix-stack)
         :scale 1.0 trunk-height 1.0
         :translate 0.0 0.5 0.0 ;; check out the z-fighting when y = 1.0 !
  -
         ;; TODO: write with-program-data macro?
         (gl:use-program (the-program *uniform-color-tint*))
         (gl:uniform-matrix (model-to-world-matrix-unif *uniform-color-tint*) 4
  
positive.code:       (%gl:uniform-4f (base-color-unif *uniform-color-tint*) 0.0 1.0 0.0 1.0)
        (framework:render *cone-mesh*)))
  
  (defparameter *tree-data*
    '((-45.0 -40.0 2.0 3.0)
      (-42.0 -35.0 2.0 3.0) 
      (-39.0 -29.0 2.0 4.0) 
  
negative.code: 	;; this gotta be a pernicious bug, swapping the z-axis so that the winding order is
  	;; always clock-wise?
  	(gl:enable :cull-face)
  	(%gl:cull-face :back)
  	(%gl:front-face :cw) 
  
  	(gl:viewport 0 0 500 500)
  