Buffer Areas Required For Z-Buffer Algorithm
For applying z-buffer algorithm, we need two buffer areas or two 2-Dimentional arrays:
1) Depth-buffer [i,j], to save the depth-value of the visible surface for all pixel in the view plane, and
2) Refresh-buffer [i,j], to save the pixel intensities of the visible surfaces.
A. In contrast to z/depth-buffer method, Scan-line method deals along with numerous surfaces. Since it processes each scan-line at one time, all polygons intersected through such scan-line are examined to find out that surfaces are visible. The visibility test engages the comparison of depths of each overlapping surfaces to find out one is nearer to the view plane. If it is determines so, then it is declared like a visible surface and the intensity values at the positions beside the scan-line are entered in the refresh-buffer.
B. Area-subdivision method is fundamentally an image-space method but utilizes object- space computations for reordering of surfaces as per to depth. The method makes utilization of area coherence in a scene by collecting those areas which form part of a particular surface. In this method, we successively subdivide the whole viewing area in small rectangles till each small area is the projection of part of a particular visible surface or no surface in any way.