Shadow Catcher: A Vision Based Illumination Condition Sensor using ARToolKit

Computing the correct illumination of virtual scenes is a well-explored area today. Most commonly used 3d graphic libraries like OpenGL or DirectX/Direct3d contain functions for these tasks. Within the field of real time mixed reality, the problem of correct illumination (i.e. consistent with the real illumination conditions) has not been considered much, because there where, and still are, more severe tasks to cope with, like for instance commonly usable tracking solutions or conveniently usable end user devices. But one of the main reasons for this is that the properties of the real light source cannot be determined in real time. There are some approaches like [1] and [2] that try to overcome this problem by conventionally tracking the position of the light source, or by using projectors as light source, which also project shadowing effects. This approach works perfectly for well controllable in-door setups but it fails for out-door applications.