LBP Showcase / Reviews / Recommendations #1
4 Player Sneak Tracker
Archive: 27 posts
| Today, while thinking about bob is named bob's thread about 4 player tracking (https://lbpcentral.lbp-hub.com/index.php?t=34033-Tracking-4-players), I had an idea for a different approach to player tracking. The principle behind it is that in stead of moving trackers around to follow players, you sweep the area to scan the player locations. I've built a working prototype: Level name: 4 Player Sneak Tracker PSN: Dexillion It's a bit crude, not optimized, and probably needs some more tweaking, but it proves the principle. All the logic is visible (though some of it very briefly), and I've added some visual and audio feedback, so I'm hoping people are able to figure out what's going on. Here's how it's made: There are two scanner blocks on flip-in pistons, scanning the area once per second. One of the pistons is delayed 0.5s so it's scanning halfway behind (or in front of) the other, like this: http://www.lbpcentral.com/forums/attachment.php?attachmentid=23393 When a scanner sees a player below it, it turns on a zero-period (infinite-frequency) emitter (from the MGS bubble dispenser), which emits marker objects with 0.9s lifetime. Each of the two blocks emits a different marker object, one of these two: http://www.lbpcentral.com/forums/attachment.php?attachmentid=23391 The markers emitted from the upper scanner have green magnetic keys and yellow magnetic switches, the markers emitted from the lower scanner have yellow magnetic keys and green magnetic switches. When a marker does not detect a magnetic key from the other scanner's markers (the other color magkey), it knows that there was no player near this position when the other scanner passed 0.5 seconds ago. This indicates a running player, so it emits an alert object. Below is a picture of a few markers being emitted above a player. http://www.lbpcentral.com/forums/attachment.php?attachmentid=23392 An alert object is a dark matter block with whatever you fancy; mine has a sound, a giant laser (so it's easy to see where you triggered it), and a red magnetic key (so the alert can be detected from off the side). The picture below shows a player triggering the alerts. You can see the alert objects appear above some of the markers, but unfortunately the laser beam doesn't show in in-game pictures. http://www.lbpcentral.com/forums/attachment.php?attachmentid=23390 To prevent the alert going off when the markers from the other scanner disappear after their 0.9s lifetime, the magnetic switch part of the marker dissolves itself immediately after being emitted. At the beginning and end of the scanned area is some darkmatter with yellow and green keys on them to surpress any alert when first moving into the area. You can see them in the first picture. If there's anything about this you don't understand, have a look at the level to see if that helps, or post your questions here. I made the level copyable so you can also experiment with it in create mode. Everybody's free to use the concept, but I would appreciate it if you let me know in this thread if you do.  http://lbp.me/v/t8pspb Edit: Forgot to mention that I haven't actually tested with 4 players, but the principle should apply for any number of players. Edit 2: Added some pictures. Edit 3: Added lbp.me info. | 2010-08-25 22:12:00 Author: Rogar  Posts: 2284 |
Sounds cool even if I'm completely confuzzled since I know nothing about logic and that stuff but it's great to see new amazing htings made. Great job  | 2010-08-25 23:42:00 Author: Dragonvarsity  Posts: 5208 |
| An interesting approach. The theory sounds good. Have you tested it with four players yet? You might even be able to refine it to the point where it can identify the offending sackboy specifically and kill him (though there might be problems with overlapping players). Are you gonna' have a showcase level? | 2010-08-25 23:58:00 Author: Sehven  Posts: 2188 |
Oh yeah, forgot to mention, I only have two controllers, and no friends.  It works with two players passing eachother, and the principle should allow for any number of players. It would be nice if someone with four controllers or buddies actually tests this to confirm, though. Showcase level? Like the one I mention in the post? It's really not hard to find on my moon, you know.  Or do you mean a complete level featuring this tech? Probably not, not for a while anyway. I always intended to make a Metal Gear level, but that won't happen before LBP2, and then this will probably be obsolete.I'm afraid killing the offender will not be so easy. I see some room for refinement (what was the sensor angle at which it starts missing people? I went for 30 to be safe), but with the current implementation, the player is long gone when the laser beam appears at the offending position. Also, because of the direction of the flipping pistons, the accuracy is different when you walk right-to-left, and you can make it running from halfway in. I tried non-flipping pistons, but that was a mess. This was before I but in the MGS emitters, though... | 2010-08-26 00:17:00 Author: Rogar Posts: 2284 |
| no friends. sad Showcase level? Like the one I mention in the post? Wow. I'm really observant today. I think I was a bit incredulous when I started reading your post so I skipped down to the bullets and then I forgot to go back up and read the rest. Sorry about that. I'll try to get around to checking it out soon: sounds intriguing. I'm not sure what the necessary angle would be: I suppose it would depend how far away from the sensor they are. As for the killing thing, yeah, it might not be possible. It would need to fire when it detects a sackboy without detecting one of the keys... but that would require a logic gate, which would add a bit of lag and, at the speed your sensor thing is moving, would probably mean it'd miss him. Anyway, great idea. I'll try to get on with all 3 of my controllers and/or a friend or two and see how it works, but it sounds like it should work just fine. The only thing is, if two sackboys were standing on the same spot when it came through for a sweep and then one took off at a run, he wouldn't be detected until the next full sweep because the other sackboy would still be there to satisfy the sensor... but that wouldn't be a huge issue: it's not like the players will see the sneak sensor in an actual level so they won't be able to time it, and it would only give him about a second of head start before being detected. | 2010-08-26 04:08:00 Author: Sehven Posts: 2188 |
Pics???? | 2010-08-26 04:11:00 Author: shadow3596  Posts: 2442 |
| I agree with shadow, everything sounds great but it would be cool if you could show us some pics to to give us a better idea of what you're talking about. | 2010-08-26 04:19:00 Author: ShamgarBlade  Posts: 1010 |
| Thanks. I really should be working on my LBL 4 in 1 entry, but maybe I'll put up some pictures later. Meanwhile, have a look at the level and see the real thing. | 2010-08-26 10:09:00 Author: Rogar Posts: 2284 |
| This level made me think two things: 1. Great-sounding piece of tech! 2. Gah, I still haven't played rogar's run! | 2010-08-26 17:17:00 Author: chimpskylark  Posts: 335 |
| Heh, I believe that's Rohar's Run. | 2010-08-26 18:05:00 Author: Rogar Posts: 2284 |
| The concept seems to make sense to me, actually. It basically just scans an area repeatedly for sackboys and how quickly they move. Unfortunately, it sounds like it can only report the sackboy's position and speed in regular intervals (the time it takes for the scanners to cover the entire distance and return), rather than give a constant signal on sack's whereabouts, so it couldn't be easily used for tracking. Simply triggering an alarm due to running too fast, however, sounds like it could initiate a whole series of gameplay elements designed to kill sackboy (like an evil lair's security system, of sorts, where the entire evil lair and its minions are alerted of your presence and try to search for you). It kind of reminds me of those radar scanners with the circular green computer screen and the scanner rotating around to reveal a bunch of white dots. | 2010-08-31 22:23:00 Author: Rhombohedron  Posts: 25 |
| Currently positions are measured twice per second, I don't know how fast you can get by tweaking. I suppose it depends on the area you're scanning, too. I think the faster your scanner moves, the coarser-grained the markers will be, so the higher the speed threshold becomes. But no matter how much tweaking, there will be some things this tracker is better at (tracking "teleportation", i.e. death), and some things the traditional player tracker is better at (like having something visible follow a player). Like I said in one of the Help threads asking for multiplayer trackers, the best solution depends on what you want to do with the tracker. Besides sneak detection I haven't really thought of any other applications for this one yet, but displaying the results on a radar sounds pretty cool. | 2010-09-01 00:03:00 Author: Rogar Posts: 2284 |
| I suppose it's not exactly on topic for what you're talking about here, but I've been toying with the idea of a radar, but haven't really settled on anything yet. I tried making a large grid with mag switches each tied to an emitter on a smaller grid that would emit little markers showing where enemies were. It seemed to work alright until I stuck it on a 4way player tracker: then the movement of the player and tracker made it kinda' go nuts. I suppose it was still semi-accurate, but one enemy would end up looking like he was in four places at once--the four places were close together, but still it was messy enough to be confusing. Maybe I'll have to give some thought to some sort of sweeper type tracker like what you're using here: I could have a large sweeper for the sensor and a small one for the display, and whenever the large sweeper detects an enemy, it outputs a blip to the small one. It'd be just like an actual radar. I'll have to experiment with that. | 2010-09-01 19:42:00 Author: Sehven Posts: 2188 |
| It's on-topic enough for me! Such a radar would be really cool with a flying mecha type of game. The only challenge I see is making the blip appear further off center the further it is from your sensor (which, though not strictly necessary, would look a lot better). I find converting a speed setting to a position isn't easy, at least not in LBP1. | 2010-09-01 20:08:00 Author: Rogar Posts: 2284 |
| Hmm...in theory, you could combine two of these guys, have them scan at the same intervals, and you would get a full-fledged, horizontal and vertical radar/scanner. Applying this in an actual level, however, might be more difficult. It might be possible to use a small cardboard square with an LED and create the pistons to move in the same intervals as well, but on a much smaller scale. When one of the scanners (either X-axis or Y-axis) detect a sackboy or enemy, it tells the corresponding X or Y-axis piston to stop there briefly while waiting for the next axis to find the sackboy/enemy. Un fortunately, stopping the LED would cause it to go out of sync with the scanner, so there would have to be some sort of syncing logic involved too. Perhaps making it pause for the same amount of time the scanner does one complete scan, so as to resume right where it left off? Sounds tricky though. Would there be any possibility of a copyable showcase level with the working prototype you've got now? I kind of want to make a radar now. | 2010-09-01 23:29:00 Author: Rhombohedron Posts: 25 |
| Nah, it doesn't need to be that complicated. Just slowly rotate a flipper piston. Set it to spin about once every two seconds or so (slow enough that piston sag isn't a problem) and have the piston flip out and return with about a .3s or so cycle. It'll cross the same target multiple times, which will result in overlapping blips, but it could actually be a good thing: if your ship or the enemy's is moving, the movement will show on the radar. Of course, you'll have to wait about a second and a half between radar blips, but it'll be like those old radars on movies and stuff. The only reason I need a radar is to give the player a general idea of where enemies are anyway: they can be in attacking position when they're slightly off screen, but if the player knows to look up, that'll be good enough to remove the cheapness from the enemy attacks. Oh, and if it wasn't already clear, the radar display would just be a scaled down version of the big radar but with an emitter to spit out the blips. They'd have to be synced perfectly which might actually be tougher than it sounds (piston sag or other drag might end up affecting one more than the other and would need to be compensated for), but it wouldn't be too tough. I'll have to experiment with it the next time I play lbp. | 2010-09-02 18:30:00 Author: Sehven Posts: 2188 |
| I will have to check it out later tonight. Recently there has been a lot of use of speed, jump, and sneak trackers and all of them have been different! The radar sounds like it would work but latency would be horrible, unless of course you need the pause. I bet you could achieve more latency with rocket cheetah logic! | 2010-09-02 19:41:00 Author: tanrockstan34  Posts: 1076 |
| Heh. Yeah, there'd be some latency, but you've seen those old radar displays, haven't you? The one where the thing sweeps around a circle at about one rotation per second and refreshes the blip each time it passes. I only need it to keep the player from getting completely blind-sided by an enemy that's just barely off-screen (especially since I've made enemies who deliberately try to blindside you from offscreen). Ideally, they should show up on the radar well before they become a threat. | 2010-09-02 20:00:00 Author: Sehven Posts: 2188 |
| sounds good, but all a little bit puzzling for me | 2010-09-02 20:48:00 Author: Pattington_Bear  Posts: 777 |
| That does sound a lot better, Sehven. And it matches the real-life method quite well. This actually sounds like a better idea for LBP2, when HUDs will be much easier to create. At any rate, that's the excuse I'm using to convince myself not to build one right this moment. | 2010-09-02 23:07:00 Author: Rhombohedron Posts: 25 |
| Tried it and it basically works. I had to set it to run reeeeeeeaaaaaalllly slow to get it to catch every mag key, though. I'm using pistons the run from 30-300 units in .5 seconds. Any faster than .5 and it misses some keys. Then I had to turn down the speed of the spinner to .5 to keep it from missing anything. That's way too slow to do any good as a radar, so to really make it work, I'll need 24 piston/sensors arrayed evenly around a circle if I want detections at 1s intervals (I'd probably settle for 2s intervals and use 12 sensors). Anyway, the display is identical to the sensor except that the pistons have emitters on the ends instead of mag switches, and I turned the max lengths down to 60 (you know, 'cuz the display area is smaller than the detection area). I also had to hook all the pistons to a timer, 'cuz their sync wasn't accurate enough if I let the game handle it: they all run off a directional switch that's triggered twice a second for a quarter of a second at a time. Anyway, it's pretty darn accurate with the radar blips showing up at the correct proportional distances and at the correct angles from the center of the display so that they match the sensors. I'll have to experiment a bit more to see if it's practical to actually use on the level I'm working on (sticking it on a moving tracker might give wierd results), but at least it's more thermo efficient than making a grid of mag switches and another grid of emitters. | 2010-09-03 05:08:00 Author: Sehven Posts: 2188 |
| Could that radar be made of spinning piece of thin gas with mag keys? That would work for moving radar. | 2010-09-03 06:07:00 Author: waD_Delma  Posts: 282 |
| Not sure what you mean. You couldn't make both ends of the piston thin gas or it would have no strength (since the piston's strength is dependent on the mass of the objects it connects), but in my test, I used thin gas for the flipper parts. Or did you mean to just get rid of the the pistons and use an array of mag switches on a spinner? That might actually work better and be more thermo efficient than a dozen flippers. The resolution will be slightly less since it'll have to be broken into zones rather than a mag switch that sweeps up and down, but that's not really a problem. It would also eliminate the double and triple blips being created from a single object being caught by the sweeper multiple times. | 2010-09-03 10:26:00 Author: Sehven Posts: 2188 |
| Yes, that is the idea but I'm not sure will it work. | 2010-09-03 14:39:00 Author: waD_Delma Posts: 282 |
| Yeah, it will. It's much simpler, more reliable, and more thermo efficient than having 12 flippers: even if it takes 12 mag switches, it'll still save on pistons and moving parts, and because the only speed you'd need to worry about is the rotation speed, it can go faster without missing detections. Now I feel stupid for experimenting with that super complicated mess, when a much simpler solution is so much better. All that's left is figuring out how best to display the results. I'm thinking tiny leds glued to dark matter can emit as the radar blips. I'll need to give it a pretty quick refresh rate, since the vehicle along with the radar display will be moving, and I'll need to make sure that there's nothing in the same layer that can collide with the leds. It'll be tricky to dress it up so that it looks good while keeping it from colliding with anything in the level, but it should be doable. Sorry for the complete thread hi-jack, Rogar. I probably shoulda' just started my own thread in the help section. [edit] Just built the radar and Tanrockstan stopped by and helped build the screen. It works great in the non-moving tests. Soon I'll stick it on a tracker and see if it suits the purpose I built it for. | 2010-09-03 19:43:00 Author: Sehven Posts: 2188 |
| No problem, the concept's the same, it just rotates instead. I'd like to see it. By the way, I made my level copyable in case someone wants to experiment with it. Beyond the scoreboard are the originals of the various emitted parts. Also added some pictures to the original post, as requested. | 2010-09-04 00:53:00 Author: Rogar Posts: 2284 |
| Well cool, I guess. Still feels a bit wierd going on about it here, but oh well. I stuck it on a tracker and tested it.... it didn't go well. Turns out that 1s refresh rate is murder when you move the screen and all the radar blips stay behind: it makes it very hard to tell where the blips are actually showing up, so you have to stop to see. I might just have to build an led display instead of using emitters... or drop the idea of adding a radar to my ship and go with something simpler. | 2010-09-04 08:32:00 Author: Sehven Posts: 2188 |
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