Hierarchical Data Structures.pdf

Computer graphics  applications require  the manip- 
ulation of  two distinct  data  formats:  vector  and  raster (see 
Figure  1). The  raster  format enables the  modeling of  a 
graphics  image  as a collection  of  square cells of  uniform 
size  (called pixels]. A  color is  associated  with each pixel. 
To attain  maximum flexibility,  an attempt  is  made to 
model directly the  addressability  of  the phosphors on the 
display screen  so that each pixel corresponds to a  phos- 
phor. This format has  also proven useful  in computer 
vision, since it  corresponds to the  digitized  output  of  a 
television camera.  In contrast,  instead of  modeling the 
display screen  directly,  the  vector  format models the