**7. Discussion**

Through the previous paragraphs, we have readily made available an ample scope of possibilities for sustainable lighting in the heritage of East Asia. New principles proposed by the authors have been devised and incorporated to facilitate the simulation process of many curvilinear geometries. Such innovative formulations are difficult to obtain, but still, due to their mathematical exactitude, the radiative transfer procedures are significantly clarified and valuable computational time is reduced to

a mere fraction in comparison with previous analysis. The complex issue of inter-reflections in curved volumes has been completed with perfect ease and this is an important novelty.

Regarding the monuments presented as case studies, some of them have been rebuilt (Seokguram) and the Nantang Cathedral is no longer extant. Therefore, we cannot monitor them properly to check the hypothesis is validated. We have to trust in other studies that the authors conducted in European heritage. For example, the Guarini Church in Torino (Italy), the Jesuit novitiate of San Luis (Seville), or the research initiated at the Egyptian Hall of Thutmose III in Luxor. We feel that perhaps more detailed work should still be done on the less complex aspect of the issue: the artificial lighting of such precincts. However, this is resolved in most cases by national consultants with little or no intervention of foreign experts and techniques. We would like to stress that all the methods hereby presented are suitable for immediate application to every kind of fixture or luminaire, and is especially appropriate for Light Emitting Diodes (LED systems, which tend to become surface distributed sources of low intensity and energy consumption.

Our unceasing effort to bring light to the darkest depths appears to be similar to the myth exposed in the Platonic cave. Nonetheless, we still believe that lighting design and predictions are a valuable resort for the qualification of the space and of heritage in this fashion. We only strive to provide a foremost advance in the scientific knowledge of design sources for natural light and issue clear expedients of how the prediction of the dynamic (radiant) energy and climate response of very resilient architectural structures has produced real sustainability through the ages.

The findings hereby reveal, for instance, to what extreme cross-cultural relationships influenced the development of the so-called Baroque Reason, which extends from Mathematics and Geometry to Art and Design. Adopting the architectural point of view, the lessons that we are to learn relate with adequacy to the climate and harmonious sustainable coexistence between the environment and civilization. A superb weapon for the fight against climate change.

Not in vain, the Swiss architectural historian, Sigfried Giedion once stated: "it is light that induces the sensation of space. Space is annihilated by darkness. If light is eliminated, the emotional content of space disappears, becomes impossible to apprehend. In the dark there is no difference between the emotional evaluation of a chasm and of a highly modeled interior." [17], p. 495.

Decades have passed since this wise dictum was pronounced and ye<sup>t</sup> architecture, in a word, does not seem fit to sustain life on our menaced planet.

A sad paradox, as it is clear that if we can neither separate history from climate nor climate from history, then, how are we to live?

The Chinese sage Zhuangzi suggested, "Be Infinite like space and the four directions—they are boundless and form no enclosures. Sustain all things in your love."

**Author Contributions:** I.R.-C. and J.M.C.-L. were helpful in conceptualizing the scope and issues. F.S.A. brought the instrumentation and the structural software as well as the momentum at low tide epochs. J.M.C.-L. developed the software for radiative simulation and created algorithms that sustained the whole process. I.R.-C. was instrumental in visualizing the cultural and artistic implications of our work.

**Funding:** This research received no external funding.

**Acknowledgments:** Francisco Salguero Andujar appreciates the kindness and help of Juhyung Lee and all the personnel at Seokguram. Inmaculada Rodriguez Cunill desires to honor the memory of Antonia Cunill Aragon by virtue of her contribution. Ioseph Cabeza-Lainez would like to dedicate this article to Jose Cuadrado Moreno for his continuous support and endurance. Ana, Rocio, and Humphrey Ojeda are well remembered.

**Conflicts of Interest:** The authors declare no conflict of interest.
