| 摘要 |
PURPOSE:To decide drawing using information even with a small number of pins by storing a Z-buffer memory with both information obtained by compressing plural Z-coordinate data and uncompressed information. CONSTITUTION:One Zo memory and one Zflag memory are assigned for four display memories and four Z memories. The Zo memory can store pieces of information as compressible ones under the condition that pieces of Z information in the display memories 1, 2, 3, and 4 are 16 or more. When four data to be drawn are not within the range of the Z0 information, a display/nondisplay decision can be made without reading out data at each detailed point. Namely. difference between the maximum and minimum values of plural pieces of Z information are compared and when the difference is less than a specific value, it is considered that compression can be done and the mean value of the respective pieces of Z information, the pieces of Z coordinates in respective coordinates, and information showing that the information can be compressed, are stored in the Z-buffer. Then, a drawing decision is made by using only the compressed information when the compressed information is usable. |
