An Interactive Non-Photorealistic Canvas

Within the area of non-photorealistic rendering, many techniques have been developed to simulate a wide variety of different styles. However, these styles are usually globally applied to some form of model that is provided as input and specific local interaction is often not possible. This thesis explores the application of the paradigm of modeling with rendering primitives to enable users to fully influence the creation of digital imagery in various artistic styles. The application of this paradigm offers a more flexible and more interactive way of working with image components. The implemented system provides tools for the manipulation of a large number of primitives at once. The thesis and the implementation described aim at enabling new possibilities of interacting with digital paintings that allow more local control and artistic freedom within the creation process of digital imagery. As such the approach is a hybrid technique. It combines the advantages of visually rich but inflexible pixel graphics on the one hand and visually less rich but more flexible vector graphics on the other hand, and adds new possibilities to allow fluid interaction. To realize this concept, image components have been used that are easy to manipulate by offering many of the flexibilities of vector primitives while still maintaining the visual quality of pixel graphics. The interaction is facilitated by employing a buffer approach that retains a responsive interaction even with a large number of these primitives. In addition, a user interface has been developed that combines all the functionality on one compact widget. It is also applicable to large, interactive displays where features such as click-less interfaces are necessary. The presented system allows the users to create non-photorealistic images without being constrained by an encapsulated algorithm. Also, it provides a new way to explore painting by permitting a high degree of local control while still maintaining some degree of algorithmic support. This enables users to easily create expressive images and interesting effects.