The research presented in this thesis pursues two goals, pushing the state-of-the art in watercolor rendering of 3D objects and animation in real-time, while at the same time providing an enhanced, interactive and art-directed control over the stylization.
Towards these goals, the field of expressive, non-photorealistic rendering is introduced, together with an introduction to the watercolor painting medium and its traditional/digital uses in animation. A literature survey follows, breaking down previous research and approaches towards a watercolor synthesis.
The contribution begins addressing existing limitations by introducing a custom painterly 3D material that brings colors to the foreground of shading control and enables dilution of colors and cangiante illumination. More importantly, this material embeds the locally art-directed and procedural stylization parameters that drive the future watercolor effects in a spatially coherent manner.
The watercolor stylization is then addressed, by extending and improving upon the palette of watercolor effects, introducing different methods and algorithms to synthesize pigment-, edge-, substrate- and abstraction-based watercolor effects. These include novel approaches towards art-directed color bleeding, dry-brush, gaps & overlaps and dilution in object-space. Together with enhanced and optimized approaches to produce controllable and robust gradient edge darkening, depth aware substrate distortion, substrate granulation and deferred substrate lighting.
The contribution is then complemented by presenting the real-time art-direction throughout the interaction spectrum, which is generalized through style control semantics that allow art-directed results to be visualized in different styles within a direct stylization pipeline. This endeavour was implemented in a widely used digital content creation software, which enabled the opportunity to perform two different user-studies involving professional computer graphics artists. The user studies substantiated and validated the contribution of this work, which can be applied in many professional fields that require art-directed 3D graphics.