Compressed Multisampling for Efficient Hardware Edge Antialiasing

摘要

Today's hardware graphics accelerators incorporate techniques to antialias edges and minimize geometry-related sampling artifacts. Two such techniques, brute force su-persampling and multisampling, increase the sampling rate by rasterizing the triangles in a larger antialiasing buffer that is then filtered down to the size of the frame-buffer. The sampling rate is proportional to the number of subsamples in the antialiasing buffer and, when no compression is used, to the memory it occupies. In turn, a larger antialiasing buffer implies an increase in bandwidth, one of the limiting resources for today's applications. In this paper we propose a mechanism to compress the antialiasing buffer and limit the bandwidth requirements while maintaining higher sampling rates. The usual framebuffer-related functions of OpenGL are supported: alpha blending, stenciling, color operations, and color masking. The technique is scalable, allowing for user-specified maximal and minimal sampling rates. The compression scheme includes a mechanism to nicely degrade the quality when too much information would be required. A lower bound on the quality of the resulting image is also available since the sampling rate will never be less than the user-specified minimal rate. The compression scheme is simple enough to be incorporated into standard hardware graphics accelerators. Software simulations show that, for a given bandwidth, our technique offers improved visual results over multisampling schemes.