Graphics Reference
In-Depth Information
T
able 7.7.1
The x-scan data at scan line y for Figure 7.9(c).
Label
polyCount
spanLeft
spanRight
ABC.active
DEF.active
LA
0
0
a
F
F
LB
1
0
a
F
T
LA
1
a
b
F
T
LB
2
a
b
T
T
LA
2
b
c
T
T
LB
1
b
c
F
T
LA
1
c
d
F
T
LB
0
c
d
F
F
Figure 7.10.
The Watkins scan line algorithm with
penetrating objects.
T
able 7.7.2
The x-scan data at scan line y for Figure 7.10.
Label
polyCount
spanLeft
spanRight
ABC.active
DEF.active
spanStack
LA
0
0
a
F
F
nil
LB
1
0
a
F
T
nil
LA
1
a
b
F
T
nil
LB
2
a
b
T
T
nil
LA
2
b
c
T
T
nil
LC
2
b
x
I
T
T
c
LD
2
x
I
c
T
T
nil
LB
1
x
I
c
F
T
nil
LA
1
c
d
F
T
nil
LB
0
c
d
F
F
nil
7.9
Octree Algorithms
Because of the regular geometric structure underlying octrees, it is fairly easy to devise
list priority visible surface algorithms for objects represented in this way if one is
using a parallel projection. One lists the voxels in a back-to-front order. For example,
