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From: Steve Baker <sbaker@link.com>
To: "Curtis L. Olson" <curt@me.umn.edu>
Subject: Re: Question
Date: Tue, 26 May 1998 07:54:04 -0500 (CDT)

On Fri, 22 May 1998, Curtis L. Olson wrote:

> I'm running into floating point problems again where my scenery tiles
> sometimes have a pixel gap between them.  I was wondering if you had
> any ideas ...
 
It's a problem that plagues us too.

I can't say that I have a magic solution.

One thing I have *considered* is to do everything in integers (for
the terrain skin at least).

This sounds counter-intuitive - but the source data for your
terrain is certainly not accurate to better than a meter - and
integers have the huge advantage that they don't suffer from
roundoff error providing all you do is add and subtract them.

However, I havn't had the nerve to try this yet - right now, we
kludge the edges of each terrain tile to make it a teeny-tiny bit
too big. The resulting overlap is very small - but enough to get
rid of the cracks.

> Anyways, what this forces me to do is for each tile I must
> glTranslate() by center_of_tile_to_be_drawn - center_of_tile_I'm_in.
> But, up until this point everything was done in double's so I was
> hoping the final translate about which is on the order of 20,000 -
> 30,000 meters would be ok.
 
But that translate could be done in integer meters. 

> Anyways, I just thought I'd see if you had any brilliant thoughts on
> the subject.

Nope - it's a continual problem for me too.

Steve Baker                (817)619-8776 (Vox/Vox-Mail)
Raytheon Systems Inc.      (817)619-4028 (Fax)
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