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- Newsgroups: comp.graphics
- Path: sparky!uunet!pipex!slxsys!dircon!uad1077
- From: uad1077@dircon.co.uk (Ian Kemmish)
- Subject: Re: Z Buffer Precision and Homogeneous Coordinates
- Date: Tue, 15 Dec 1992 19:10:33 GMT
- Message-ID: <1992Dec15.191033.17861@dircon.co.uk>
- References: <78173@hydra.gatech.EDU>
- Lines: 34
-
- gg10@prism.gatech.EDU (GALLOWAY) writes:
-
-
- >transform into planes." The depth value gets normalized from the range
- >[near, far] to [0, 1].
- >
- >If the viewing transformation matrix consists of only linear operations,
- >translation, rotation, and scaling, then this appears to degrade the
- >precision of the depth value. In my current Z buffer-based renderer my
- >Z buffer is an array of 32 bit floats. I preform clipping in the 3D view
- >space (or eye space) before perspective projection.
- >
- >
- >Greg Galloway
- >gg10@prism.gatech.edu
- >
- >
- You're essentially trading accuracy for range. If you can only
- afford integers for depth values (either becasue you only have 16
- bits or because you can't wait for all those floating compare
- operations), then you definitely don't want to risk them
- overflowing and/or wrapping round. On the other hand, if you are
- already using float with no problemsn, then you have little
- incentive to change (basically, all you need is a number system that
- can represent infinity:->) - in fact, unless you are happy at
- visualising and doing mental arithmetic with homogeneous co-ordinates
- in your head, you will find debugging takes a lot longer if you *do*
- change.....
-
- --
- Ian D. Kemmish Tel. +44 767 601 361
- 18 Durham Close uad1077@dircon.co.uk
- Biggleswade uknet!dircon!uad1077
- Beds SG18 8HZ United Kingdom
-