This chapter collects the findings of the research on the cellular automaton-based shading systems (CASS) for building envelopes. CASS is based on congruent modular units, thus it has the potential of being inexpensive and robust. Two approaches for the realization of CASS are presented: based on the liquid crystal technology, and based on the rotation of polarized film elements. Several optimization methods of CASS are presented. The optimization criteria include: the “grayness” monotonicity, and cellular automaton (CA) pattern distribution error which represent: the level of control over the CA pattern, and its uniformity over entire array of cells, respectively. The robustness of CASS for various types of failure is discussed.