<!-- MHonArc v2.4.4 --> <!--X-Subject: q-tree stuff --> <!--X-From-R13: ptNnzv-pt.UenlEntr.Sqzbagba.OP.QO (Quevf Uenl) --> <!--X-Date: from babe.globecomm.net [207.51.48.8] by mx01.ny.us.ibm.net id 857333989.128579-1 Sun Mar 2 20:19:49 1997 --> <!--X-Message-Id: 9703021924.7ujd@ami-cg.GraySage.Edmonton.AB.CA --> <!--X-Content-Type: text/plain --> <!--X-Head-End--> <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2//EN"> <html> <head> <title>MUD-Dev message, q-tree stuff</title> <!-- meta name="robots" content="noindex,nofollow" --> <link rev="made" href="mailto:cg#ami-cg,GraySage.Edmonton.AB.CA"> </head> <body background="/backgrounds/paperback.gif" bgcolor="#ffffff" text="#000000" link="#0000FF" alink="#FF0000" vlink="#006000"> <font size="+4" color="#804040"> <strong><em>MUD-Dev<br>mailing list archive</em></strong> </font> <br> [ <a href="../">Other Periods</a> | <a href="../../">Other mailing lists</a> | <a href="/search.php3">Search</a> ] <br clear=all><hr> <!--X-Body-Begin--> <!--X-User-Header--> <!--X-User-Header-End--> <!--X-TopPNI--> Date: [ <a href="msg00040.html">Previous</a> | <a href="msg00042.html">Next</a> ] Thread: [ <a href="msg00149.html">Previous</a> | <a href="msg00043.html">Next</a> ] Index: [ <A HREF="author.html#00041">Author</A> | <A HREF="#00041">Date</A> | <A HREF="thread.html#00041">Thread</A> ] <!--X-TopPNI-End--> <!--X-MsgBody--> <!--X-Subject-Header-Begin--> <H1>q-tree stuff</H1> <HR> <!--X-Subject-Header-End--> <!--X-Head-of-Message--> <UL> <LI><em>To</em>: <A HREF="mailto:mud-dev#null,net">mud-dev#null,net</A></LI> <LI><em>Subject</em>: q-tree stuff</LI> <LI><em>From</em>: <A HREF="mailto:cg#ami-cg,GraySage.Edmonton.AB.CA">cg#ami-cg,GraySage.Edmonton.AB.CA</A> (Chris Gray)</LI> <LI><em>Date</em>: Sun, 2 Mar 97 12:24:15 MST</LI> </UL> <!--X-Head-of-Message-End--> <!--X-Head-Body-Sep-Begin--> <HR> <!--X-Head-Body-Sep-End--> <!--X-Body-of-Message--> <PRE> Thanks Todd! The picture came out fine on my Amiga, so it must have worked on PC's, right? :-) To summarize my understanding here (you never know, I could have missed it altogether!), objects are stored in B-trees, in which the index is the Morton code (or some other similar function) of the co-ordinates of the object. Objects that are "nearby" in the co-ordinate space are nearby in the B-tree, so searching for them is much faster than any kind of linear scan of the whole set of objects. This works well in a setup where there isn't a specific data structure for each location in the world, on which to hang the object list, and on which to hang pointers to nearby locations. Given a co-ordinate, it is fairly quick to find what would be there, and keeping track of the B-tree search path lets you find the nearest objects easily too. I did a game system for CP/M, which was kinda like the old Ultima games. I had "grids" representing tile-based surface maps, and "mazes" representing the underground 3D view areas (line-drawing only - this *was* on a 1 Mhz 8080 with 64K RAM, including the graphics card). I had a global linked list of all objects in the grid or maze, and simply did a linear scan, checking the co-ordinates, in order to find things. This worked since I was in a small world with only a few dozen objects (if that!), but it sure wouldn't have worked in a big world with hundred's of objects. To follow on to that, I'll mention how I did "special" things. I used something like 6 bits to select the terrain for each location in a grid. The terrain value gave me the tile, and the monster-set. One value said "special". When I found that, I would search for that location in the grid's list of special terrains. That gave me a new tile and/or monster set. The Morton-indexed B-trees could be used for these terrain things in a bigger world. The final tree entry could be a pointer to a database entry giving detailed information for that special location. Similarly, for 3-D maze areas, the basic entry in the description array could give bits describing the walls/floor/ceiling. "Special" entries could be used for things like hidden doors, traps, monster triggers, etc. in a similar way. If your "grids" get *very* big, so that having an array for them is not practical, then you do as Todd said - just have quad-trees representing the various properties that are needed to describe the location (terrain type, monster sets, weather, temperature, etc.) You can layer the whole thing - if you need smaller regions within your large world that are too varied for efficient storage using quadtrees, then you can have a B-tree entry for them that points to an array-based description, which in turn can point at a few special single-location descriptions. Note that in some cases you may be able to use a simple function on the co-ordinates to calculate some properties, rather than having to store it is a quadtree. Pseudo-random number generators, seeded by the co-ordinates, are something I've always had in mind for this. I did it once in a little CRT-based system (curses/termcap), and it worked OK, but not super. -- Chris Gray cg#ami-cg,GraySage.Edmonton.AB.CA </PRE> <!--X-Body-of-Message-End--> <!--X-MsgBody-End--> <!--X-Follow-Ups--> <HR> <!--X-Follow-Ups-End--> <!--X-References--> <!--X-References-End--> <!--X-BotPNI--> <UL> <LI>Prev by Date: <STRONG><A HREF="msg00040.html">Re: Quadtrees?</A></STRONG> </LI> <LI>Next by Date: <STRONG><A HREF="msg00042.html">Re: Just a bit of musing</A></STRONG> </LI> <LI>Prev by thread: <STRONG><A HREF="msg00149.html">Re: Issues from the digests and Wout's list</A></STRONG> </LI> <LI>Next by thread: <STRONG><A HREF="msg00043.html">Re: q-tree stuff</A></STRONG> </LI> <LI>Index(es): <UL> <LI><A HREF="index.html#00041"><STRONG>Date</STRONG></A></LI> <LI><A HREF="thread.html#00041"><STRONG>Thread</STRONG></A></LI> </UL> </LI> </UL> <!--X-BotPNI-End--> <!--X-User-Footer--> <!--X-User-Footer-End--> <ul><li>Thread context: <BLOCKQUOTE><UL> <LI><strong><A NAME="00044" HREF="msg00044.html">Issues from the digests and Wout's list</A></strong>, Alex Oren <a href="mailto:alexo#europa,com">alexo#europa,com</a>, Mon 03 Mar 1997, 20:08 GMT <UL> <LI><strong><A NAME="00047" HREF="msg00047.html">Re: Issues from the digests and Wout's list</A></strong>, coder <a href="mailto:coder#ibm,net">coder#ibm,net</a>, Tue 04 Mar 1997, 13:29 GMT </LI> </UL> <UL> <li><Possible follow-up(s)><br> <LI><strong><A NAME="00148" HREF="msg00148.html">Re: Issues from the digests and Wout's list</A></strong>, coder <a href="mailto:coder#ibm,net">coder#ibm,net</a>, Thu 20 Mar 1997, 13:05 GMT </LI> <LI><strong><A NAME="00149" HREF="msg00149.html">Re: Issues from the digests and Wout's list</A></strong>, coder <a href="mailto:coder#ibm,net">coder#ibm,net</a>, Thu 20 Mar 1997, 13:21 GMT </LI> </UL> </LI> <LI><strong><A NAME="00041" HREF="msg00041.html">q-tree stuff</A></strong>, Chris Gray <a href="mailto:cg#ami-cg,GraySage.Edmonton.AB.CA">cg#ami-cg,GraySage.Edmonton.AB.CA</a>, Mon 03 Mar 1997, 04:19 GMT <UL> <li><Possible follow-up(s)><br> <LI><strong><A NAME="00043" HREF="msg00043.html">Re: q-tree stuff</A></strong>, Carter T Shock <a href="mailto:ctso#umiacs,umd.edu">ctso#umiacs,umd.edu</a>, Mon 03 Mar 1997, 14:05 GMT </LI> <LI><strong><A NAME="00070" HREF="msg00070.html">Re: q-tree stuff</A></strong>, coder <a href="mailto:coder#ibm,net">coder#ibm,net</a>, Sat 08 Mar 1997, 11:54 GMT </LI> </UL> </LI> <LI><strong><A NAME="00033" HREF="msg00033.html">Linear Quadtrees</A></strong>, Carter T Shock <a href="mailto:ctso#umiacs,umd.edu">ctso#umiacs,umd.edu</a>, Sun 02 Mar 1997, 20:35 GMT <LI><strong><A NAME="00018" HREF="msg00018.html">Quadtrees?</A></strong>, Wout Mertens <a href="mailto:Wout.Mertens#rug,ac.be">Wout.Mertens#rug,ac.be</a>, Fri 28 Feb 1997, 10:54 GMT </LI> </UL></BLOCKQUOTE> </ul> <hr> <center> [ <a href="../">Other Periods</a> | <a href="../../">Other mailing lists</a> | <a href="/search.php3">Search</a> ] </center> <hr> </body> </html>