Mumbai university > Comp > SEM 4 > Computer Graphics

Marks: 5M

Year: May 2015

1. The area-subdivision method takes advantage by locating those view areas that represent part of a single surface.

2. Divide the total viewing area into smaller and smaller rectangles until each small area is the projection of part of a single visible surface or no surface at all.

3. Continue this process until the subdivisions are easily analyzed as belonging to a single surface or until they are reduced to the size of a single pixel.

4. An easy way to do this is to successively divide the area into four equal parts at each step. There are four possible relationships that a surface can have with a specified area boundary.

   • Surrounding surface: One that completely encloses the area.

   • Overlapping surface: One that is partly inside and partly outside the area.

   • Inside surface: One that is completely inside the area.

   • Outside surface: One that is completely outside the area.

1. The tests for determining surface visibility within an area can be stated in terms of these four classifications.

2. No further subdivisions of a specified area are needed if one of the following conditions is true:

   • All surfaces are outside surfaces with respect to the area.

   • Only one inside, overlapping or surrounding surface is in the area.

   • A surrounding surface obscures all other surfaces within the area boundaries.