Seamless: seam erasure and seam-aware decoupling of shape from mesh resolution

A parameterization decouples the resolution of a signal on a surface from the resolution of the surface geometry. In practice, parameterized signals are conveniently and efficiently stored as texture images. Unfortunately, seams are inevitable when parametrizing most surfaces. Their visual artifacts are well known for color signals, but become even more egregious when geometry or displacement signals are used: cracks or gaps may appear in the surface. To make matters worse, parameterizations and their seams are frequently ignored during mesh processing. Carefully accounting for seams in one phase may be nullified by the next. The existing literature on seam-elimination requires non-standard rendering algorithms or else overly restricts the parameterization and signal.

We present seam-aware mesh processing techniques. For a given fixed mesh, we analytically characterize the space of seam-free textures as the null space of a linear operator. Assuming seam-free textures, we describe topological and geometric conditions for seam-free edge-collapse operations. Our algorithms eliminate seam artifacts in parameterized signals and decimate a mesh---including its seams---while preserving its parameterization and seam-free appearance. This allows the artifact-free display of surface signals---color, normals, positions, displacements, linear blend skinning weights---with the standard GPU rendering pipeline. In particular, our techniques enable crack-free use of the tessellation stage of modern GPU's for dynamic level-of-detail. This decouples the shape signal from mesh resolution in a manner compatible with existing workflows.