What is the difference between a true HDRi and the conversion you provide in IRender?
In order to make a “true HDRi” you take three pictures of the same scene – One normal, one under exposed and one over exposed. The normal, under exposed and over exposed versions are then used to determine which parts of these scene create the light. This light intensity factor is stored in the .HDR file, along with the RGB (red, blue and green) values for each pixel. We are able to use that factor to provide illumination for the rendered scene. When we do the conversion ourselves, we “guess”, based on whether you tell us we are looking at a daytime image or a nighttime image which pixels are the light source. Here is a scene captured with three levels of exposure. The routine which combines these three scenes into a .HDR file is able to determine that the sky and some of the windows are illuminating the scene.
