Phong Tessellation

Abstract

Modern 3D engines used in real-time applications provide shading that hides the lack of higher order continuity inside the shapes using modulated normals, textures, and tone-mapping -artifacts remain only on interior contours and silhouettes if the surface geometry is not smooth. The basic idea in this paper is to apply a purely local refinement strategy that inflates the geometry enough to avoid these artifacts. Our technique is a geometric version of Phong normal interpolation, not applied on normals but on the vertex positions. We call this strategy Phong Tessellation.

GPU-based smooth free-form deformation with sharp feature awareness

“…There are many successive studies regarding FFD. Most of these studies focus on improving the interactive means of FFD (Coquillart, 1990;Hui, 2002;MacCracken and Joy, 1996;McDonnell et al, 2007;Xu et al, 2013). Gain and Bechmann (2008) provided a detailed survey of these methods.…”

“…The PN-triangle method (Vlachos et al, 2001) decouples the linear geometry and normal information of a polygonal object to achieve visually plausible smooth geometry and shading, in which it adopts cubic and quadratic triangular Bézier surfaces to represent the geometry and normal, respectively. Phong tessellation (Boubekeur and Alexa, 2008) proposed by Boubekeur et al uses scalar tags to solve the sharp edge problem.…”

“…3 is smooth except for the geometry artifacts, i.e., the unsmooth silhouettes and patch boundaries. Various solutions can be used to alleviate the artifacts for the Phong shading of polygonal objects (Vlachos et al, 2001;Boubekeur and Alexa, 2008). A method inspired by the PN-triangles (Vlachos et al, 2001) is proposed to improve the silhouettes, patch boundaries, and keep the sharp edges.…”

“…For example, Phong shading can achieve smooth shading effect at a low computational cost via linear normal interpolation across a triangle. To alleviate the unsmooth silhouette problem in Phong shading, the PN-triangle (Vlachos et al, 2001) method and Phong tessellation (Boubekeur and Alexa, 2008) method alter the linear geometry of a triangle as a curved geometry according to the related normal field.…”

Synthesizing Subdivision Meshes Using Real Time Tessellation

“…A number of subdivision surface approximations [19], [20], [21] have been proposed following a similar strategy. Simpler operators such as Phong Tessellation [22] can also offer an economic way to get rid of most of the typical visual artifacts stemming from coarse meshes. Although all of those methods produce smoother high-resolution versions of the input mesh, none of them can reproduce the high quality of a true subdivision surface.…”