PBR Based Specular Reflection

Demo: When a light hit on the surface of an object, it could be separate into three parts: a. Specular reflection; b. Diffuse reflection; c. Absorbed by the surface.  Specular and diffuse refl...

How to calculate ∫ 1 / sqrt (x ^ 2 + 1) dx

A friend who is preparing for her exam asked me such question. I thought it for quite a long time and finally I did it ! P.S. I think the point is using the sec ! t = √(u ^ 2  + 1) dx =...