gamnit :: Mesh :: center
# Center coordinates of all the vertices var center = new Point3d[Float]((min.x+max.x)/2.0, (min.y+max.y)/2.0, (min.z+max.z)/2.0) is lazy, writable
redef var center = new Point3d[Float](0.0, 0.0, 0.0) is lazy