Just realized that I left out few details. First I ASSuME you are using a texture that includes bump maps(otherwise you probably wouldn't have this problem. So go to Materials room and make sure the bump is plugged into a node (either gradient bump or as described in previous post) Second, if you are using bumps then you probably want to have diplacement maps enabled. And finally try turning on raytracing also. Try that first, if you want to refine it and if you have a really good computer with lots of resources you can improve the look of most textures by turning up the value on the minimum shading rate (if your computer can handle pixel samples setting of 6 you could probably turn up the shading rate above 1 also.)