High speed image drawing apparatus for displaying three dimensional images

A three-dimensional image drawing apparatus comprising:

• a frame buffer for storing display data corresponding to a display apparatus display screen;
• a two-dimensional drawing circuit for performing coordinate operations in order to draw specific two-dimensional images to said frame buffer;
• a Z buffer for storing depth data for performing three-dimensional drawing to said frame buffer;
• a three-dimensional straight line drawing circuit for performing three-dimensional drawing to said frame buffer based on said depth data stored in said Z buffer;
• a memory control circuit for controlling access to the buffers;
• and
• a bit number altering circuit for altering the number of bits per pixel in coordinate operations in said two-dimensional drawing circuit either to a number of bits corresponding to drawing data in said frame buffer or to a number of bits corresponding to depth data in said Z buffer;
• wherein:
• areas of said frame buffer and Z buffer are established in same physical memory;
• and
• said bit number altering circuit selectively performs drawing to said frame buffer and setting of depth data to said Z buffer by coordinate operations of said two-dimensional drawing circuit, by altering the number of bits per pixel in the coordinate operations of said two-dimensional drawing circuit.