expression refering to the number of
polygons in a
three-dimensional image, which effects how
smooth the image appears to be, how quickly it can be
rendered, and how long it will take the computer to
redraw it, as part of a game or other
interactive application. usually, the polygons are
triangles, since this is the most
flexible type (you can make a square out of two triangles, but it would take a lot of little squares to make a convincing triangle).
polygon count is generally lower for objects with
flat surfaces than it is for objects with
curved surfaces (see
nurbs for more information about creating
organic shapes). this is because a curve is approximated by
subdividing triangles, creating a lot of small triangles for the
application to keep track of. it's a pretty simple concept (illustrated in
2d because i don't have the patience to try and approximate
3d in ascii):
/\ /\
/ \ /__\
/ \ /\ /\
/______\ /__\/__\
triangle.. subdivided.
so in a 2d example, polygon count increases by a factor of 4. of course, it increases much more quickly in
three dimensions.
whether the emphasis is on
low polygon count or
smoothness depends on the purpose of the
graphics being created. it is a trade-off and finding a happy medium can be a complicated task. anyone who has used
vrml or any
virtual reality application has probably seen that objects tend to be more
jagged than in a sophisticated 3d
computer game, and anyone who has seen
gerrie's game or other 3d film will have noticed how incomperable the graphics in games are to the graphics in a movie. obviously, how
complex an object can be depends on how quickly graphics need to be rendered. in an
interactive game where users can move
objects around, the computer may be asked to redraw any object, from any
angle, at any scale. in a game with
fixed graphics, the user will approach objects, but other than the
scale their appearance will remain more or less the same. for a movie, the only 'users' can take quite a bit of time
waiting for objects to be rendered, making a low polygon count much less important.