Path: chuka.playstation.co.uk!news From: "John \( QuietBloke \)" Newsgroups: scee.yaroze.freetalk.english Subject: Quadtrees - am I missing something Date: Sat, 17 Feb 2001 00:17:01 -0000 Organization: PlayStation Net Yaroze (SCEE) Lines: 36 Message-ID: <96kfp8$rfo1@www.netyaroze-europe.com> NNTP-Posting-Host: host213-122-11-145.btinternet.com X-Priority: 3 X-MSMail-Priority: Normal X-Newsreader: Microsoft Outlook Express 5.50.4522.1200 X-MimeOLE: Produced By Microsoft MimeOLE V5.50.4522.1200 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