Pixel masks for screen-door transparency
Jurriaan D. Mulder, Frans C. A. Groen, Jarke J. van Wijk · Centrum Wiskunde & Informatica (CWI), the national research institute for mathematics and computer science in the Netherlands · 1998
Rendering objects transparently gives additional insight in complex and overlapping structures. However, traditional techniques for the rendering of transparent objects such as alpha blending are not very well suited for the rendering of multiple transparent objects in dynamic scenes. Screen-door transparency is a technique to render transparent objects in a simple and efficient way: No sorting is required and intersecting polygons can be handled without further preprocessing. With this technique, polygons are rendered through a mask: Only where the mask is present, pixels are set. However, artifacts such as incorrect opacities and distracting patterns can easily occur if the masks are not carefully designed. In this paper, first the requirements on the masks are considered. Next, three algorithms are presented for the generation of pixel masks. One algorithm is designed for the creation of small (e.g. 4 \\Theta 4) masks. The other two algorithms can be used for the creation of larger masks (e.g. 32 \\Theta 32). For each of these algorithms results are presented and discussed. CR Categories and Subject Descriptors: I.3.3 [Computer Graphics ]: Picture/Image Generation - Display Algorithms; I.3.6 [Computer Graphics]: Three-Dimensional Graphics and Realism - Visible Line/Surface Algorithms. Additional Keywords: Screen-Door Transparency 1