A Z-Buffer is added to a Row Addressable Graphics Memory With Flash Fill so that a Z (or Depth) value is supplied with each Start and End address. The Z value is calculated for each pixel between the Start and End address. This value is compared to the existing Z value for that pixel stored in the Z-Buffer....http://www.google.ca/patents/US5933156?utm_source=gb-gplus-sharePatent US5933156 - Z-Buffer for row addressable graphics memory with flash fill
