Chasing inside the fireplace with geometry (geometric Displace + Optimize). Grate «Fireguard» consists of elements Instance, elucidated the path of «Fireplace Fireguard Path». Who will insert FBX, fling to the model «Fireplace.mat», export material is not correct 100%. Green marble fireplace (yes, in reality marble texture is very large) is transparent and SSS. Perhaps it makes sense to turn off transparency in saturated interior details.