"Does IBL work by setting up a sphere of lights in accordance to the pixel layout on the 2D light probe (image)? If so, it's fairly clever, saving the user from arranging all those lights. But it also means the user cannot control the number of lights, nor each light individually." Close. In Poser, it creates "virtual" lights at rendertime that work in much the same way, reducing the overhead. however, the purpose of it is to allow the duplication of a "real world" lighting set up for compositing. In short, it was created to allow Filmmakers to more seamless blend digital creation and real world by providing a method for duplicating the subtle lighting levels of the real world setting in the digital space. Side benefit is much more apparently realistic lighting without the need for massive, system killing lightsets. Rather cool, isn't it?