Differentiate between z-buffer method and scan-line method. What is the visibility test made in these methods?

Solution: In depth buffer algorithm every pixel location on the projection plane is identified for determining the visibility of surfaces regarding this pixel. Conversely, in scan-line method all surfaces intersected through a scan line are studied for visibility. The visibility test in depth-buffer method engages the comparison of depths of surfaces regarding a pixel on the projection plane. The surface closest to the pixel position is seemed visible. The visibility test in scan-line method which compares depth computations, for each overlapping surface to find out which surface is nearest to the view-plane hence it is declared as visible