Path: chuka.playstation.co.uk!news
From: "John \( QuietBloke \)" <quietbloke@btinternet.com>
Newsgroups: scee.yaroze.freetalk.english
Subject: Re: Quadtrees - am I missing something
Date: Sat, 17 Feb 2001 20:01:37 -0000
Organization: PlayStation Net Yaroze (SCEE)
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References: <96kfp8$rfo1@www.netyaroze-europe.com>
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Its all making a little more sense I think... still getting my brain used to
all this 3d stuff...
What was puzzling me last night and still a little today is wouldnt it be
easier to just to perform a translate / rotate on the camera and then see
what grid pos it is in... from there I would have thought you could quite
quickly figure out what cells are within view. Everyone cant possibly be
wrong so I guess its quicker to rotate / transform each quadrant down until
you get to leaf level.

I also nipped over to the gamasutra articles Peter mentioned and am now
wading through that... I'm going on the theory of keep reading everything
and eventually it'll all click into place and make sense !

Anyway.. thanks to you all for you help.. I may be asking more questions
real soon <grin>

PS. If anyone else has any good articles on just about any 3d related
subject Id be most grateful if you let me know it. That goes for good books
too :)
Cheers
John
"John ( QuietBloke )" <quietbloke@btinternet.com> wrote in message
news:96kfp8$rfo1@www.netyaroze-europe.com...
> OK.. I've just been looking into Quadtrees today. Part of my 3d self
> training course. I can see its a very simple concept but I must be being
> real dim tonight because I cant see the point of them.
>
> Reason...
> OK.. the main example I saw was a small example terrain of a 16x16 grid.
The
> reasoning was you dont want to draw the whole terrain just the bit the
> camera can see.
> This is the bit I dont get.. the tutorial then goes through how with a
> quadtree you start from the root and check the camera in the four quarters
> and eliminate the ones its not in.. then sub divide again etc etc and
> eventually you end up with just the leaf(s) that the camera is in and the
> leafs point to triangle data to draw the scene.
> Thats all fine and dandy but if its a grid then surely you can just do a
> quick calculation to figure out which leaf the camera is in...
>
> ie.. the camera x and y position will tell you exactly what cell the
camera
> is in.
>
> So what has this tutorial missed out ?... anyone ?.. why would I need to
use
> an quadtree when drawing a terrain ?
>
> Also... what happens next ?.. I know what leaf the camera is in but how do
> you decide what cells are visible going out to the horizon ( or a fair
> distance at least ) ?
>
> Im sure some of you have done this and its obvious and sorry for being dim
> but this really is all new to me and from what I've discovered I have a
> awful lot to learn !
>
> Ahhh who knows.. by tommorow morning I may have it figured out.
>
> Cheers
> John
>
>