Reciprocal shading for mixed reality

Reciprocal shading for mixed reality aims to integrate virtual objects into real environments in a way that they are in the ideal case indistinguishable from real objects. It is therefore an attractive technology for architectural visualizations, product visualizations and for cultural heritage sites, where virtual objects should be seamlessly merged with real ones. Due to the improved performance of recent graphics hardware, real-time global illumination algorithms are feasible for mixed-reality applications, and thus more and more researchers address realistic rendering for mixed reality. The goal of this thesis is to provide algorithms which improve the visual plausibility of virtual objects in mixed-reality applications. Our contributions are as follows: First, we present five methods to reconstruct the real surrounding environment. In particular, we present two methods for geometry reconstruction, a method for material estimation at interactive frame rates and two methods to reconstruct the color mapping characteristics of the video see-through camera. Second, we present two methods to improve the visual appearance of virtual objects. The first, called differential instant radiosity, combines differential rendering with a global illumination method called instant radiosity to simulate reciprocal shading effects such as shadowing and indirect illumination between real and virtual objects. The second method focuses on the visual plausible rendering of reflective and refractive objects. The high-frequency lighting effects caused by these objects are also simulated with our method. The third part of this thesis presents two user studies which evaluate the influence of the presented rendering methods on human perception. The first user study measured task performance with respect to the rendering mode, and the second user study was set up as a web survey where participants had to choose which of two presented images, showing mixed-reality scenes, they preferred.