...
in computer graphics and Image processing overlap, the
amas
am
concerned with fundamentally different operations.
In
computer
graphics, a computer is used to create a pichue.
Image
processing, ... focusing, deflection of the electron beam can be controlled either
with electric fields or with magnetic fields. Cathode-ray tubes are now commonl!.
constructed with magnetic defle...
... device inter-
face methods is given
in
the Computer Graphics Interface (CGI) system. And
the Computer Graphics Metafile (CGM) system specifies standards for archiv-
ing and transporting pictures. ... by scan con-
verting the basic geometric-structure specifications into pixel patterns. Typically,
graphics programming packages provide functions to describe a scene in terms
of...
...
discussed in Section
3 -10 ,
we can set the radii for the concentric boundary
arcs
at
r
=
14
and
r
=
17 .
Although this method
is
accurate for generating thick circles,
in general, ... the fill color. This occurs because the algo-
rithm checks next pixels both for boundary color and for fill color. Encountering
a pixel with the
fill
color can cause a recursive branch to te...
... lines arc then processed through the intersection calculations,
which must solve simultaneous circle-line equations
Splitting
Concave
Polygons
We can identify a concave polygon by calculating ...
Area Clipping (polygons)
Curve Clipping
Text Clipp~ng
Line and polygon clipping routines
are
standard components of graphics pack-
ages, but many packages accommodate curved objects, pa...
... track of
which surface section is visible on each scan line. This works only
if
surfaces do
not cut through or otherwise cyclically overlap each other (Fig.
13 -11 ).
If
any kind
of cyclic ...
in
Chapter 14 .
13 -1
1
CURVED
SURFACES
Effective methods for determining visibilit$ for objects with curved surfaces in-
clude ray-casting and octree methods. With ray casting, we ca...
... Object-Intersection Calculations
Raysurface intersection calculations can account for as much as
95
percent of the
processing time in a ray tracer. For a scene with many objects, most of the pro-
cessing ... to reduce intersection calculations, is to use space-subdivision meth-
ods. We can enclose a scene within
a
cube, then we successively subdivide the
cube until each subregion (ce...
...
and science had to rely on expensive and cumbersome equipment, advances
in
computer technology have made interactive computer graphics a practical tool.
Today,
we
find computer graphics used ...
F'I~~II~
1
-
I
Examples
of
computer
graphics applications.
(Courtesy
of
DICOMED
Corpora!
ion.)
Chapter
1
A
Survey
of
Computer
Graphics
Figure
1- 10
Vie...