Seamster: Inconspicuous Low-Distortion Texture Seam Layout Alla Sheffer ∗ Department of Computer Science Technion I.I.T, Haifa, Israel John C. Hart † Department of Computer Science University of Illinois at Urbana-Champaign (a) (b) (c) Figure 1: Seamster efficiently figures out where to cut an object to flatten it. Figure (a) shows that the seam (in blue) sneaks through low visibility regions of the model (in red) to cut into high curvature vertices, reducing the distortion of the flattening (b) and texturing (c). ABSTRACT Surface texturing aids the visualization of polygonal meshes by pro- viding additional surface orientation cues and feature annotations. Such texturing is usually implemented via texture mapping, which is easier and more effective when the distortion of the mapping from the surface to the texture map is kept small. We have previously shown that distortion occurs when areas of high surface curvature are flattened into the texture map. By cutting the surface in these areas one can reduce texture map distortion at the expense of additional seam artifacts. This paper describes a faster technique for guiding a texture map seam through high distortion regions, while restricting the seam to regions of low visibility. This results in distortion reducing seams that are less visually distracting and take less time to compute. We have also observed that visibility considerations improve the speed of a recent method that adds cuts to reduce a surface genus. CR Categories: I.3.7 [Computer Graphics]: Three-Dimensional Graphics and Realism—Color, shading, shadowing, and texture. Keywords: Texture Mapping, Visibility Classification 1 I NTRODUCTION Texture mapping is a useful tool in the visualization of surfaces. Texturing capitalizes on the perceptual cue of size constancy to aid ∗ sheffa@cs.technion.ac.il † jch@uiuc.edu the user in perceiving depth. The higher the spatial frequency of a texture, the farther away the surface appears. Texturing can also be used to annotate a surface, with grid lines, text, markers, glyphs or other features. Texture mapping requires the assignment of texture coordinates to a meshed surface, but meshes in visualization applications are of- ten unparameterized and unstructured. A variety of techniques have been devised to automatically generate texture coordinates for such meshes. Many of these techniques strive to minimize the distortion of the texture mapping, preserving the proportions of features in the texture as they are mapped to the object surface. A majority of these techniques generate the texture by mapping the surface into the plane and using it as a two dimensional texture map. These techniques assume that the surface mesh has already been cut into a simply connected two-dimensional manifold-with- boundary. Once such a cut has been performed, the mesh can be flattened into the domain of the texture map. The selection of this cut is often either arbitrary or left to the intuition of the user. The cut results in a texture seam, which can appear as a dis- continuity in the appearance of the texture on the object surface. Hence cuts should be made judiciously and kept short when possi- ble. Users often hide the seam by placing it in an area of the model that is least seen. For example, texture maps for animals typically have their seam along the underbelly. The layout of a two-dimensional texture map onto the surface of a given three-dimensional object inevitably creates distortion in all but special cases. It is a well-known differential geometry re- sult that for a general surface patch there is no distance-preserving (isometric) parameterization in the plane [1]. Distance-preserving parameterizations exist only for developable surfaces, i.e. surfaces with zero Gaussian curvature such as the cylinder. The strategic placement of seams can reduce this distortion. Cut- ting a seam through areas of high Gaussian curvature can relieve