an improved method and apparatus for rendering curved surfaces in a graphics system . the appearance of a curved surface is created by varying color shades across an object . the graphics systems represents each primary color with fewer than eight bits . the present invention maintains smooth transaction between color shades despite using fewer than eight bits to represent color . an eight bit color shade value is truncated , with the most significant bits being saved and used as a color value . the least significant bits that are truncated are used to determine which of the adjacent color values to use to render pixels . thus , if five bits are saved and used to represent a color , the three least significant truncated bits are used to determine the appropriate mix of the closest five bit shades . the three truncated bits are used to select an entry from a ramp table and a control signal from a look - up table selects a bit from the selected ramp table entry . the selected bit is used to determine which of the closest five bit shades to use for rendering a pixel .