Preprint B39/2010
NormalShop: Modeling surface mesostructure
Luiz Velho | Pereira, Thiago
Keywords: Geometric Modeling | normal maps | RGBN image | details | base surface | filtering | warping | texture synthesis | orthogonal chart
Normals have been used in geometry acquisition and rendering for years. However, modeling with normals is rather limited because of the lack of formally defined operations. We present a variety of formal surface normal operations built on two key ingredients. First, a separation of models in a base surface and details, while the base surface is represented by positions in a mesh, the details are only represented through normals in a parametric space. Our operations can process the detail normals, while guaranteeing that the base surface remains unchanged. In this way, we do not require a reconstruction step. Second, all our editing operations are performed in an orthogonal projection. Besides being more intuitive for the user, normals in an orthogonal mapping are in fact an RGBN image. This lets us define normal operations including combination, sketching features, filtering, warping and texture synthesis. Furthermore, we present an interactive system that implements these operations using a texture atlas for storing geometric detail as normals. This solution works with high resolution models and imposes no restrictions on surface topology. In particular, our system uses point-based graphics to build custom orthogonal charts. Next, it processes the normals and updates the texture atlas. By using a temporary orthogonal editing chart, our system presents the user with a transparent representation. It is not restricted to processing in the original charts.