https://gregoriuspineo.com/categories/10/products/8 

* At medium and far angles to speed up rendering turn off Displace
* When using OBJ apply MeshSmoth with 2-3 iterations.
* Those who work in V-Ray versions below 3.1 be careful in the materials in the BRDF section there is Microfaset GTR (GGX) if you have a version below 3.1 then the BRDF field will be empty. Choose Blinn Phong or Ward – whichever suits you best