On the mobile devices using real time lighting is not a good idea. Obviously we needed to go for light backing. Baking of 300 MB model was too much time consuming. We had to switch to external baking used mental ray to produce occlusion map per object. To give the final output, we combined lighting map involved directional light with Photoshop. Legacy light mapped shaders were used for each material. Result of entire process was not great. We again restarted standard Unity baking process to achieve light mapping with tweaking few options which was lengthening the baking process. Much optimised rendering was achieved after disabling final gathering phase.