Abstract: A three-dimensional display apparatus approximates a three-dimensional object by planes and expresses each of the planes by pixels on a plurality of scan lines, thereby to acquire a display image. A designation circuit designates a plurality of pixels on a target scan line, a depth data generator generates depth data of the designated pixels, and a luminance data generator generates luminance data thereof. Depth memory stores depth data. Luminance memory stores luminance data. A comparator reads out the depth data of designated pixels from the depth memory. Upon reception of depth data of the pixels generated from the depth data generator, the comparator compares the read depth data with the received depth data with respect to the same pixel.

Abstract: A system has circuitry for reading out a graphic data string from a source area of a graphic memory, starting from a start address storing the graphic data string, by continuously counting the start address of the graphic memory. The graphic data string read out by this circuitry is stored in a buffer memory. When storage of the graphic data string in the buffer memory is completed, the graphic data string is continuously read out from the buffer memory. The readout graphic data string is written in a destination area, starting from a start address thereof, by continuously counting the start address of the destination area in the graphic memory.

Abstract: A start point (x'.sub.0,y'.sub.0) and an end point (x'.sub.m,y'.sub.m) of a sub-line are obtained from a start point (x.sub.0,y.sub.0) and an end point (x.sub.m,y.sub.m) of a main line, and coordinate data of the start point (x'.sub.0,y'.sub.0) and the end point (x'.sub.m,y'.sub.m) are supplied to a DDA, so that a point array of the sub-line can be generated from the DDA. The main line is shifted along the x- or y-axis by one dot to obtain the sub-line. Intensity information from an intensity modulation circuit is noninverted/inverted in accordance with the main line/sub-line mode so as to provide a complementary relationship between the main line and the sub-line.A vector direction from the start point (x.sub.0,y.sub.0) to the end point (x.sub.m,y.sub.m) is detected to belong to one of the four areas obtained by dividing the x-y coordinate plane by lines y=x and y=-x when the start point (x.sub.0,y.sub.0) is defined as the origin of the coordinate system.