Game Development Reference
In-Depth Information
simulator game that caches in architecture as the plane gets close. If the game attempts
to draw a building that hasn
'
t been cached in, then the building simply won
'
tshowup.
Think for a moment what is more important to the player: a piece of architecture that
will likely show up in 100ms or so anyway, or a frustrating pause in the action?
Not All Resources Are Equally Important
It
s a good idea to associate a priority with each resource. Some resources
are so important to the game that it must suffer a cache miss rather than fail
to render it. This is critical for sound effects, which must often be timed
exactly with visual events, such as explosions.
'
The really tough open-map problems are those games that add a level of detail on
top of an open-map design. This approach is common with flight simulators and
action adventure games. Each map segment has multiple levels of detail for static
and dynamic objects. It
s not a horrible problem to figure out how to create different
levels of detail for each segment. The problem is how to switch from one level of
detail to another without the player noticing. This is much easier in action/adventure
games where the player is on the ground and most objects are obscured from view
when they flip to a new level of detail.
Flight simulators don
'
t have that luxury. Players want the experience of flying high
enough to see the mountains on the horizon and diving low enough to see individual
trees and ground clutter whiz by at Mach 1. This requires a delicate balance between the
resource cache and the renderer, and it is one of the most difficult problems in modern
flight simulators that provide a truly realistic experience with supersonic aircraft.
This subject is way beyond the scope of this topic, but I won
'
t leave you hanging.
There is some amazing work done in this area, not the least of which was published
in Level of Detail for 3D Graphics by D. Luebke, M. Reddy, J. Cohen, A. Varshney, B.
Watson, and R. Huebner. They also have a website at
http://lodbook.com.
'
Smart game programmers realize early on that some problems are harder than
others. If you thought that creating a good flight simulator was a piece of cake, I
'
d
tell you that the hard part isn
t simulating the airplane but simulating the ground
and everything on it. The newbie game programmer could spend all his time creating
a great flight model, and when he started the enormous task of representing undulat-
ing terrain with smooth detail levels, he would fold like laundry.
'
