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DelphiAegis posted:Nah, generally physics system freak outs like that are due to models clipping into one another. The collision system attempts to separate them by imparting force in a direction to one of the objects. This force is then applied but the objects don't separate because they're still connected or the collision system models another collision, which reduces the force on one, imparting it to the other object so now they're moving together. Another thing that can cause problems is when two things are connected by a joint but they also intersect each other. The physics system will attempt to push one of the objects out so they aren't colliding, but the movement of that object imparts force on the object it's connected to, oftentimes retaining the collision. This clip is an example of intentional abuse of similar physics glitches. The player (PJ DiCesare, a fairly well-known speedrunner and breaker of games) made a "vehicle" that's a loop of four components connected by flexible joints. It has no motive force -- no engines, sails, etc., but after being allowed to exist for a bit, it builds up a feedback loop between its components and starts to spin like mad. He uses this to complete a "long jump" challenge where you have to move the protagonist as far as possible -- not end-to-end, but total movement even if it backtracks. He just jumps off the end of the skijump and vibrates for awhile.
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Jun 4, 2020 17:30
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Cardiovorax posted:I always kind of assumed that they just calculate everything through momentum, but thinking about it, I really have no idea how much fidelity goes into modern physics engines. Anyone here familiar enough with the subject who could tell me how much of that kind of thing they usually even bother keeping track of? Amateur game developer here. Most 3D games these days use "rigid bodies" for their physics simulations. Each one has mass and velocity, a shape (which may or may not accurately reflect the visuals; the shape typically is composed of one or more convex shapes like boxes, capsules, and spheres), and perhaps attributes like bounce elasticity (how much energy is lost in a collision) and friction and so on. When two rigid bodies intersect, the game will calculate the energy of the collision based on their velocities, masses, and the degree of intersection, and then attempt to force the two apart again. However, there isn't necessarily any effort made to ensure that the energy in a system is conserved -- that expulsion force can cause there to be more energy in the system than there was before the collision. If it also then doesn't actually succeed in removing the intersection between the two rigid bodies (perhaps because it removed the intersection in one area but added a different intersection in another area), then on the following frame even more energy is added to attempt to remove the collision... You have to also couple this with the fact that the physics engine is expensive to run, so it doesn't usually update every frame. A 60FPS game might only have a 30FPS or 20FPS physics engine; the frames without physics updates draw things at their predicted locations based on their velocities and how much time has passed since the last update. But the less frequently the physics engine runs, and the faster things can move, the more they can get embedded in each other before the physics engine has a chance to notice and try to expel them. Videogame physics works best with slow-moving objects, and the faster things go, the more likely they are to need to cheat somehow. Bullets are not physics objects, for example. Even in games that simulate projectile travel time, ballistic drop, etc. they're much too fast for the physics engine to reliably detect when they hit something.
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Jun 7, 2020 14:42
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LifeSunDeath posted:Thanks for the writeup. My dumb rear end sees game glitches and just goes "why can't they just not let objects clip into each other, problem solved" but I know from experience, it's way more complicated than that, and lots of things have to clip together to make it look right, so weird things happen sometimes. Yeah, things clipping is...I wouldn't say it's unavoidable, but you're sharply limited on what you can do if you make it a rule that things are never allowed to intersect. The underlying issue for a lot of this is that game time isn't continuous, but occurs in (typically) 1/60th of a second increments. Consequently, game physics doesn't actually move objects around, it teleports them. On one frame you're at X position, on the next you're at X+1 position, without having occupied any of the space in-between. If there's a wall at X+.5 then whoops, you're slightly embedded into it. It's possible to avoid this, but it's expensive and complicated. Let's say your object is a box. That means that each frame, the game checks a rectangular shape to see if it's overlapping something. What you can do instead is "sweep" the box along its movement vector, for a length equal to the amount of distance the box moves each frame. This creates a new shape that covers all of the space the box would occupy during its movement, if time were continuous. You can then blap that shape down and check for collisions, and if you find one, do a bunch of math to figure out exactly when "during" that frame the collision occurred, and stop the box just short of collision. Similar swept collision detection also exists for 3D games (Unity has them for boxes, spheres, and capsules, for example). The problem is that they're sufficiently expensive that nobody I know of uses swept collision detection for standard physics behaviors. Instead they're reserved for things like "is there enough land in front of this unit for it to keep walking forward" -- stuff where if you just did a raycast (draw a line from point A to point B) you might get false positives.
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Jun 7, 2020 19:46
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SubponticatePoster posted:I've been having fun (sometimes) with the AI in Mafia 3. I'll kill a dude off by himself with a silenced gun, and somehow some rear end in a top hat on the other side of the map "sees" it and puts the whole area on alert. This has happened through walls, floors, ceilings, etc. And no matter where I am on the map they will always make a beeline to me. It does get hilarious when they come in a slow conga line and I just kill them from around the corner one after the other and end up with a huge pile of bodies in a stairwell or whatnot. Reminds me of playing a Splinter Cell game (I forget which, the one where Sam starts out as a civilian and gradually acquires his old kit over the course of the game). There's a bit with a well that comes out in the middle of a large open area with a fair number of guards wandering around. One of your ways to kill enemies is to lure them into poking their heads over an area where you're hanging, and you just grab them with one hand and yank them down to their deaths. I piled up at least a half-dozen guards at the bottom of that well.
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Jun 9, 2020 02:04
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I'm working on adding dazzle camouflage to my ship game. To get the right look, everything on the ship needs to be camouflaged, except I got a little overzealous with "everything". https://twitter.com/byobattleship/status/1273697781824098304 Bonus: when the ship moves, the texture...doesn't. https://i.imgur.com/gO4VjkW.mp4
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Jun 18, 2020 20:48
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Now I'm gonna have to have a random island in one of the missions be just covered in monkeys.
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Jun 29, 2020 19:15
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https://twitter.com/mike_ducker/status/1284511736209571840 Not a game glitch, per se, but it's in the right space.
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Jul 18, 2020 20:53
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Plenty of modern games will strive mightily to avoid crashes as well. Sometimes when things break, it's hard to tell if the thing that broke was as minor as "the game stops drawing grass" or as major as "the game stops drawing all terrain". You hope that your game's QA is good enough to catch the latter, and you don't really care about the former, so if suddenly your code can't draw stuff...just, kinda, hope things work out and keep going! Well, in an ideal world, you'd crash, then during the dev process you'd get these weird crashes and figure out "oh hey, the grass isn't drawing, lemme fix that". But gamedev is a complicated and hard process and there's never enough resources to do everything perfectly. So you settle for just logging a warning and continuing, and then right before launch someone will go through and turn off all the "log a warning" statements that nobody ever followed up on. In most serious software, in contrast, you have a very good idea of how important a given failure is, and most failures are mission-critical. So crashing is used more freely.
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Jul 21, 2020 19:17
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Those archers are really on the ball. I think I saw only one arrow miss.
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Jul 31, 2020 00:10
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So what exactly happened there? The helicopter got hit and was displaying as damaged, but still had control until it didn't?
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Aug 16, 2020 12:11
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Yeah, the sheer scope of the game means that stuff is gonna slip through. I'm sure they have a horde of folks tracking down and fixing bugs now that they have a big enough QA team (a.k.a. the customers) to actually find and report these issues.
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Aug 22, 2020 17:39
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Cardiovorax posted:What kind of unit were you using for velocity that the physics simulation could hit the maximum value for a signed 64-bit integer without already having reached the speed of light and refusing to accelerate any further anyway? The issue isn't hitting the maximum value for a float64, it's that floats don't provide continuous coverage of the number line, and that coverage gets spottier and spottier the further you get from 0. So if you have a large value X that can be represented with float64s, and you add a small acceleration Y to it, you get a speed of X back, because (X+Y) is closer to X than it is to the next representable float64 value. For reference, (c in meters per second) / (maximum value represented by a float64) is about 1e-300, so I recommend using units of "planck units per lifetimes of the universe".
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Aug 28, 2020 23:14
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Korremar posted:since y'all are explaining the technicalities of stuff like this, can someone break down why the Super Scope only works on CRTs? I heard a pretty nonspecific mumbling about refresh rates and color values or something but also I'm dumb as hell and could be absolutely misremembering The Super Scope requires a display that uses a scanning electron gun, which is how CRTs work. The electron gun fires electrons at phosphors in the screen, causing them to emit light; they then continue to glow for a bit before decaying and going dark. It does this by scanning horizontally across the screen, one row at a time, very quickly. By continually refreshing the phosphors (pixels), you get a display that's stable to human eyes but kind of flickery if you have a decent sensor. The sensor on the scope is able to detect the momentary increase in brightness that represents the electron gun scanning across the part of the screen that the scope is pointed at. When the player pulls the trigger and the sensor sees the electron gun, the scope sends a signal to the game saying "I saw the electron gun", and the game is able to look at which row of pixels it was painting, and specifically where in that row it was painting, to figure out what the gun was pointing at. This is waaaay more pleasant to use than the NES lightgun, which required visibly flickering the screen so the gun could report what colors it sees. But it's also a bit fiddly and relies on fairly precise timing, so you generally need to calibrate it for it to work properly.
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Aug 29, 2020 14:59
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I have no idea why this happens but it's great. https://twitter.com/SilverSoul164/status/1299877627960979459
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Aug 30, 2020 04:57
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Pretty good posted:(jump to 1:14 bc I can't figure out how to do that automatically with the way SA handles youtube embeds) You can add "&t=1m14s" to the end of the URL to get it to jump to a specific time. Read as "And set the time to 1 minute and 14 seconds".
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Sep 7, 2020 14:15
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https://www.youtube.com/watch?v=Xc5rB-0ZBcI
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Sep 17, 2020 19:16
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One of the playtesters for my game turned up a fun one: if you kill multiple ships in very rapid succession, sometimes the death explosion becomes gigantic. I need to figure out some way to leave this in while also making it harder to trigger accidentally...
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Sep 26, 2020 04:10
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Oh, I figured out the bug and fixed it. I have a pool of explosions, and when I destroy a ship it pulls an explosion from the pool, multiplies its scale according to the size of the ship, and then plays it. Note that it doesn't first verify that the explosion's scale is set to 1; it just blithely assumes. Something about killing things in rapid succession makes it so that the ship is more likely to get an explosion that's already large, so effectively the size gets squared and you end up with a scale of, say, 900 instead of 30. Anyway, the point is that having gigantic explosions sometimes is fun. It just needs to not look quite so much like a bug.
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Sep 26, 2020 04:26
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Ahh, I gotcha. That might work. At the moment none of the dying ships know about each other, but that can be changed. Thanks for the suggestion! 
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Sep 26, 2020 04:37
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Triarii posted:The funny thing is that I've since realized that a normal fall from walking off of a ledge that high (instead of dramatically swan diving onto your face) does barely any damage, so I just ignore ladders and break my knees constantly now. Reminds me of Starfox Adventure. One of the dungeons in that game is a big vertical climb, and when you get to the top, you need to go back to the bottom. I'd wager that at least 90% of the players just jumped off the closest ledge, fell like 20 stories, and took the half-heart of resulting falling damage, rather than actually retrace their steps safely.
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Oct 21, 2020 22:00
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Triarii posted:They got those advanced finger-pointing techniques in Night City Good trigger discipline though
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Dec 13, 2020 15:44
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Your bike got the zoomies. You should play with it more often.
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Dec 16, 2020 16:24
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Grey Fox posted:boat physics in games seem hard Remember this classic? https://www.youtube.com/watch?v=9pQ_ZozZIio
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Dec 17, 2020 05:22
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Cardiovorax posted:Thanks, I actually didn't know that. Learn something new every day. American measurement systems are the real game glitch.
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Jan 18, 2021 02:22
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I've been replaying Transcendence lately. It's a spacefaring roguelike game -- gate into a new system, blow up the hostile stations and their guardians, loot the wrecks, sell the loot, upgrade your ship. As the game progresses, enemies get more dangerous, and their loot gets more valuable. It...can break down a bit towards the endgame though. I just destroyed a Gaian Processor, basically a giant nanoassembler with a bunch of thermonuclear cannons on it, that roams around, blowing up everything it encounters and eating the resulting matter to help maintain itself. In the wreck was, among other things, 25 plasma cannons. This in a game where you can typically only use 1 primary and 1 secondary weapon at a time.  On the plus side, my money problems are solved!  I've also found stations with 30 segments of diamond lattice armor, one of the best armors in the game...and even the largest playership can only use 6 segments of armor.
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Jan 19, 2021 05:28
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SubNat posted:The Just Cause series has a very strange and terrible glitch throughout all games in the series, where none of them have functioning co-op/multiplayer. Multiplayer is loving complicated*. And there's a huge difference in expected quality between a mod and a first-party system. If you're playing with mods, then you expect a certain amount of jank and brokenness, and moreover you expect that things will stay broken until the mod creator, who is only doing this in their spare time as a hobby, is able to get around to working on it again. If you're playing a game with first-party multiplayer, then you expect that multiplayer to work, everywhere, and if at any point there's jank, odds are you'll think less of the developers for shipping a "lovely product" (never mind that it's a miracle most games work anywhere near as well as they do). And the longer they go without fixing it, the worse your opinion of them will be. Not to mention that if a modder offered to add multiplayer to my singleplayer game, for free, without any extra effort on my part? I'd probably be thrilled to step back and let them at it. More power to you, buddy! But if I want to implement that multiplayer myself, that's a ton of work that I have to do, and I need to allocate my scarce gamedev resources wisely or I'll go broke and have to get a real job again. * I want to emphasize this point because a lot of gamers don't understand just how hard multiplayer is to add to games. It needs to be a priority feature from day one, and it easily doubles the scope of most games to have it. And multiplayer anything with physics? Ha ha ha, good luck, there's a reason why Fall Guys is getting lauded for having clean multiplayer with physics and that's because it's a goddamn miracle that it works.
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Feb 10, 2021 21:49
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I don't know that this is my favorite game glitch, but it sure was a weird one. https://i.imgur.com/82Y1b8d.mp4 Finally got it sorted out today after like 4-6 hours of debugging, thanks to a chance comment by fellow indie dev StealthyMoose.
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Mar 19, 2021 04:14
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dialhforhero posted:Are you working with Game-Labs to develop Ultimate Admiral: Dreadnoughts? Way back when I was first getting rolling on this project (I forget, maybe six months in?), they announced their game, and I had an immediate crisis of "someone ate my lunch before I even had a chance." One of the devs reached out though and we had a nice chat. They actually enquired if I was interested in working on the project, but certainly at the time I was much more interested in having full creative control over what I made. I also wanted to make a different kind of game. Like, we're both doing design-your-own-ship naval combat simulators, but theirs is way more grounded and realistic, and mine is much more arcadey. So while their game puts emphasis on things like how well-armored your citadel is, or how up-to-date the fuzes are on your shells, mine is more "how many guns can I fit onto this patch of real estate?  " They're both totally legitimate styles of game, but I'm pretty sure I'm a lot happier doing my game instead of their game, simply because I don't have the depth of interest in naval combat mechanics that they do.
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Mar 22, 2021 17:51
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alexandriao posted:Huh! How are projectiles simulated? I always figured it was a raytrace and stepping but the stepsize in the one game I play (that seemingly handles thousands of projectile) seems too discrete for it to handle that many (Bearing in mind the game is a mod of Jedi Academy, so it's quite an old engine and the resulting game can run on some pretty low powered machines) I can only speak to the game I've worked on (which has a free demo out until Tuesday at 10AM Pacific time, and enters Early Access in July!), but yes, it uses raycasts for bullets. I actually have a 60Hz physics update rate*, but because I do the bullets "manually", I can get away with running them at 30Hz instead. They still draw at your display refresh rate, they just don't detect collisions every frame, because detecting collisions is expensive. It's cheaper to just fire a longer ray when the bullet does get to detect collisions. Old games often scale very well in terms of the number of objects they can handle, because they have highly-optimized code and only need to handle very constrained situations. For example, it wouldn't surprise me if in Jedi Academy, each character (of which there aren't very many at a time) only has one or two colliders, maybe plus one per lightsaber. And the terrain mesh is low-detail, and there aren't many other objects that can be collided with. All of that combines to make each raycast very cheap. Take that engine and run it on more recent hardware, and it has plenty of spare overhead to run thousands of projectiles. For similar reasons, there's a Doom wad out there which has a huge open arena with like 10000 revenants, and it runs just fine on modern computers because Doom is super highly optimized. On mid-90's hardware, that same wad would be unplayable. * I'd intended to have a 30Hz physics update rate, but Unity ties how smoothly particles can move to how quickly the physics tick, and I use a lot of particles that need to draw at 60Hz
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Jun 20, 2021 17:37
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Dareon posted:I could picture that working two ways: My first thought was the bullet fires a ray both backwards and forwards along its flight path to see if it hit anything in the previous tick or will next tick, then I realized that would be kinda dumb and it probably fires a ray two steps ahead to see if it will hit anything in the distant future. There's potential for some interesting shenaningans with the first model. quote:I do love this kind of stuff, because you generally know how the physics you want to use would work in the real world, but you can't actually do that virtually yet, so you solve the problem of, say, how an enemy detects the player by having the player constantly firing an invisible gun from their eyes that alerts the enemy when it hits them. Physics engines get abused for this kind of thing all the time. Like, in my game the player has a big sphere that follows them around, and when bullets hit that sphere, they make a "whoosh" sound. Because you don't want every bullet everywhere to constantly be making sounds, only the ones that get close enough that you can hear them. This also means that every bullet has a "hasWhooshed" property so I don't play the sound twice, and also that every weapon type has a "bulletWhooshes" property that indicates if it makes noise. Because e.g. torpedoes shouldn't make a sound like a supersonic projectile just zipped past you.
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Jun 21, 2021 01:01
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OK, non-supercavitating torpedoes shouldn't make that sound. I haven't gotten the tech tree progressed enough to introduce the supercavitating kind
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Jun 21, 2021 01:23
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https://twitter.com/yaoilowell/status/1412777806405148686 (There's some speculation as to potential causes in this Twitter thread, but no confirmation yet)
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Jul 9, 2021 01:52
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I would hazard a guess that what happened here is the techbros that Amazon put in charge figured they could launch with a minimum viable product and then iterate towards a workable solution. This approach kind of works in industry tech, so long as your customers are prepared to put up with a lovely product while they do large-scale QA for you. In games, though, there's plenty of other games that people can play, so you have no real reason why gamers should play your game. And while gamers are probably more willing to put up with barely-functioning wads of code than most people, they also have no particular reason to stay with your product if it stops being fun. Contrast that to productivity or commerce tech, where your product can be where all of their working data is or their only source for a good they need. Couple that with the devs having to work with a tech stack that really wasn't intended to be used for MMOs...
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Oct 29, 2021 19:21
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The Lone Badger posted:Amazon will start buying successful game companies and mandating that they have to follow Amazon management procedures and use Amazon tech. It's basically even odds whether a tech giant will look at an endeavour they just dropped $500 million* on and say "this was stupid, we're never doing it again" or "we need to double down and spend even more". * number made up, I have no idea how much Amazon has spent on gaming so far
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Nov 4, 2021 00:33
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Dareon posted:Railroads Online is a train simulator game that requires you to build all your own tracks from station to station. Naturally, derailing is a constant concern. Imagine if the engine had landed on those other tracks and continued merrily on its way. Further imagine if the rest of the train cars did the same thing, linking up with the engine as they landed.
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Nov 6, 2021 16:59
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Hackers film 1995 posted:ok for real. i cant stop laughing at this gta 7 to 9 jersey. does anyone know how this could happen? At a guess, they had a bump map and an albedo (color) map, and they did two separate OCR+upscale passes on them instead of doing just one. And then the passes returned different text.
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Nov 13, 2021 16:41
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I had to fix the exact same bug in my game -- when you go into binoculars mode, your ship has to disappear, as do things like the indentation the ship makes in the water. Along similar lines, there's what happens to Jensen's model when he goes into a vent: 
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Nov 16, 2021 00:48
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I'm working on walking tripods for my game. Normally, they look like this: However, they're not actually capable of turning around, and if they spawn facing the wrong way, then they get confused about where their legs should go, and end up looking like this:  Poor guy needs to use the bathroom
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Nov 23, 2021 05:31
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Neito posted:This reminds me of how TF2 handled decapitating characters with the Eyelander when that came out all those years ago. I guess Source can't handle severing models or something, so what it did was scale the head like .00001% and spawned a head gib. Cutting meshes in half is not particularly trivial, and can make resource management trickier (i.e. you can't just re-use the old character mesh when the character respawns), so it's really not surprising that tricks like this are used instead. Perhaps my favorite of these kinds of bugs is that Twinrova, the boss in Ocarina of Time, isn't actually "killed" when you beat her; she's just made invisible and told to go wait in the corner for 9999 frames. There's no reason to stick around in the boss arena after the ending cutscene plays out, so this isn't generally a problem. But if you wait out that timer, then she'll become active again, and you can fight her (while she's still invisible), beat her, and get another ending cutscene and heart container.
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Dec 1, 2021 22:00
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haveblue posted:I don't know what game that was originally from either but I've seen speedrunners do that to glitch through Control It's a fairly common glitch. If the player can stand on physics objects, and they can pick up physics objects, then odds are good that they can fly by surfing a physics object that they're holding. I've seen it in Half Life 2 and Banjo-Kazooie Nuts & Bolts, for example. It's also the kind of glitch that I think gamedevs mostly aren't too fussed about fixing, because it doesn't really interfere with regular gameplay. And who cares if some folks use it to fly?
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Dec 3, 2021 20:29
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