define shrub
  group quads
    scale 2.5 2.5 5
    scale 0.5 0.5 0.5
    matref shrub
  end
enddef

define treeleaves
  group quadsX
    scale 15 15 -30
    shift 0 0 30
    matref treeleaves
  end
enddef

define treetrunk
  group trifan
    scale 0.8 0.8 38
    matref treetrunk
  end
enddef