I was thinking of implementing PBR in my engine and so I went about researching it. I haven’t found it the easiest thing to comprehend but I’ve seen a few papers that explain it pretty well but I’ve noticed that a lot of the time they combine direct and indirect lighting models, I.e. diffuse and specular lighting plus image-based lighting.
My question is, isn‘t image based lighting all you need for PBR? It feels to me (in my non-maths-expert-brain), that having both would introduce unrealistic results. In my mind, you just need an environment map …