Photorealistic visualization techniques for using spatial augmented reality in the design process

The automotive industry uses virtual content and corresponding real objects for designing, developing and assessing new components of a car. It is also possible to use projectors to display the virtual content directly on the real object. This technique is called spatial augmented reality and is especially interesting for the design process, because in contrast to a visualization with traditional virtual reality techniques the designer has a more realistic impression of the virtual content. Since many different virtual contents can be projected onto the shape of one basic real object, this procedure can significantly reduce the number of design iterations as well as the overall design time. If spatial augmented reality is used in the design process, it is important that the virtual content is projected onto the real object with a very high visual quality, because design decisions are made based on this projection. It is especially important that the visualized colors on the real object are not distinguishable from corresponding real reference colors and the virtual content lies on the correct positions on the real object. In this thesis, new approaches for the augmentation of real objects are presented which are able to match these requirements and are also applicable to other industrial areas. A new method is presented for evaluating the overlay accuracy achieved by current and extended geometric registration techniques. To account for the visual requirements, a new rendering method with ray tracing is presented which increases the visual quality of the projected images in comparison to existing methods. The desired colors of these images have further to be adjusted to compensate for the material, the ambient light and the projector pose. For this purpose, a physically-based computation is developed which exactly determines the corresponding RGB values for these colors by using threedimensional lookup tables at every projector pixel. Since not all of the desired colors can be represented with an RGB value of the projector, an adjustment has to be computed for these colors. Therefore, a new adjustment method for such values is proposed, resulting from a study using design experts from the automotive industry. Furthermore, an efficient implementation of the radiometric compensation is proposed which is able to compute the adjustment for the RGB values for varying projector positions at interactive rates. Since the range of projectable colors not only depends on the material and the ambient light, but also on the projector pose, the proposed method can be used to interactively adjust this range when moving the projector to arbitrary positions around the real object. All proposed methods are evaluated in a number of experiments and are compared to existing approaches.