Abstract: The present invention provides apparatus and methods which are most advantageously used in conjunction with a computer display system incorporating the use of a Z-buffer to provide three dimensional hidden surface elimination. A buffer memory is provided which is sufficiently large such that each display element (pixel) on the display is represented by a 16-bit Z value. The Z value corresponds to the Z axis depth of the object at the particular point corresponding to the pixel. The buffer comprises a plurality of dynamic random access memories (D-RAMs) having two operation modes: Normal and Read-Modify-Write (RMW). A counter/pointer register is provided which successively addresses values in the buffer representing successive pixels along scan lines of the display. A graphics processor is provided with coordinates defining a three dimensional image to be displayed and, for each point of the object, computes a current Z.sub.c value beginning at an initial coordinate address in memory.