Piecewise Smooth Surfaces with Features.
详细信息
文摘
The creation, manipulation and display of piecewise smooth surfaces has been a fundamental topic in computer graphics since its inception. The applications range from highest-quality surfaces for manufacturing in CAD to believable animations of virtual creatures in special effects, to virtual worlds rendered in real-time in computer games. Our focus is on improving the a) mathematical representation and b) automatic construction of such surfaces from finely sampled meshes in the presence of features. Features can be areas of higher geometric detail in an otherwise smooth area of the mesh or sharp creases that contrast with the overall smooth appearance of an object. In the first part, we build on techniques that define piecewise smooth surfaces to improve their quality in the presence of features. We present a crease technique suitable for real-time applications that increases the perceived visual detail of objects while maintaining a compact representation and efficient evaluation. We then introduce a new subdivision scheme that allows the use of T-junctions for better local refinement. It thus reduces the need for extraordinary vertices, which can cause surface artifacts especially on animated objects. In the second part, we consider the problem of building the control meshes of piecewise smooth surfaces so that the resulting surface closely approximates an existing data set such as a 3D range scan), particularly in the presence of features. To this end, we introduce a simple modification that can be applied to a wide range of parameterization techniques to obtain an anisotropic parameterization. We show that a resulting quadrangulation can indeed better approximate the original surface. Finally, we present a quadrangulation scheme that turns a data set into a quad mesh with T-junctions, which we then use as a T-Spline control mesh to obtain a smooth surface.