Re: Question about large worlds and foating point precision.

It's most often solved by transforming the origin. Increasing precision is
*not* the answer; it simply delays the inevitable a little longer (while at
the same time halving your VPU throughput). Of course, at the last second,
you might be able to do intermediate host computations in increased
precision, but at the end of the day, your graphics hardware is rendering
with 32-bit floats (at most). 

 

This is a well-known problem with well-understood solutions in practice.
That said, you can't just use (for example) the GPG4 solution in one system,
without your entire game engine using it. So "messy" is a relative term; if
you are developing a large-world game, chances are you are using a
large-world game engine. If not, you've probably licensed the wrong engine
for your game.  

 

Floating-point precision issues are also well-defined (from a computer
science perspective), but often not really fully understood by most
programmers (myself included). The most commonly cited work is David
Goldberg's paper for ACM (1991). An edited version is here: 

 

http://www.cse.msu.edu/~cse320/Documents/FloatingPoint.pdf

 

The original is here:

 

http://portal.acm.org/citation.cfm?id=103163


Greg

 

From: [email protected]
[mailto:[email protected]] On Behalf Of Juan
Linietsky
Sent: Tuesday, June 21, 2011 8:12 PM
To: [email protected]
Subject: [Sweng-Gamedev] Question about large worlds and foating point
precision.

 

Here's a doubt i've been having for a while. When developing games based on
large worlds (like Elder Scrolls, GTA, etc), i can imagine that physics and
rendering become more jittery the further away the camera moves from the
origin (due to floating point precision loss). Is this really a problem? If
so, how is this solved? I can imagine that increasing floating point
precision to doubles helps a enormously, but i'm not sure if that's enough
and if it's worth the extra processing/bandwidth cost. 
  Transforming the world to local coordinates (so the camera is always at
the origin) also seems to me like a solution, but sounds like a lot more
work and messy code.
So, how is this solved in most cases?

cheers!

Juan

_______________________________________________
Sweng-Gamedev mailing list
[email protected]
http://lists.midnightryder.com/listinfo.cgi/sweng-gamedev-midnightryder.com