Amid a clang and clamor of activity, Vaidyanatha Selvanathan Sthapati sits on the floor of his family pattarai, or workshop, in Chennai. All around him, men in dhotis and vests are engrossed in cutting, sculpting, and finishing gray granite. They chip and chisel and hammer away, slowly bringing to life an intricately carved pillar destined to adorn a Hindu temple. The scene is familiar to Selvanathan, 57. He says he grew up in the pattarai of his uncle, who taught him to be curious and observant, as nature was the…