Since the 8.1 update, Cinema 4D supports HDR (High Dynamic Range) images. They can be used as realistic light source to illuminate a scene with radiosity. We will explore this new feature. Besides imaged-based illumination with HDRI, we will also explain how to integrate a fake floor in the scene. However, it only makes senses with high-resolution HDRI. As HDRI is already explained in details elsewhere, it will be presented briefly here.
As they have an extended color depth, HDRI can store the light intensity of natural environments. On a normal 24 bit RGB image, the brightest color is pure white, no matter whether this brightness represents a small lamp or the sun. The HDR method goes further: with its higher bit depth it can record the brightness of a light source, this illumination data will then be used by the radiosity rendering engine. Moreover this illumination will also affect reflections: highlights - in the shape of the illumination source - will appear on objects with reflective materials. An example would be a white surface with a luminance of 1000%. If a reflective object is illuminated by it, the white surface will be strongly reflected on it, producing the same effect as if a square spot light was used.