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  • How can I implement collision detection for these tiles?

    - by Fiona
    I am wondering how this would be possible, if at all. In the image below: http://i.stack.imgur.com/d8cO3.png The light brows tiles are ground, while the dark brown is background, so the player can pass over those tiles. Here's the for loops that draws the level: float scale = 1f; for (row = 0; row < currentLevel.Rows; row++) { for (column = 0; column < currentLevel.Columns; column++) { Tile tile = (Tile)currentLevel.GetTile(row, column); if (tile == null) { continue; } Texture2D texture = tile.Texture; spriteBatch.Draw(texture, new Microsoft.Xna.Framework.Rectangle( (int)(column * currentLevel.CellSize.X * scale), (int)(row * currentLevel.CellSize.Y * scale), (int)(currentLevel.CellSize.X * scale), (int)(currentLevel.CellSize.Y * scale)), Microsoft.Xna.Framework.Color.White); } } Here's what I have so far to determine where to create a Rectangle: Microsoft.Xna.Framework.Rectangle[,,,] groundBounds = new Microsoft.Xna.Framework.Rectangle[?, ?, ?, ?]; int tileSize = 20; int screenSizeInTiles = 30; var tilePositions = new System.Drawing.Point[screenSizeInTiles, screenSizeInTiles]; for (int x = 0; x < screenSizeInTiles; x++) { for (int y = 0; y < screenSizeInTiles; y++) { tilePositions[x, y] = new System.Drawing.Point(x * tileSize, y * tileSize); groundBounds[x, y, tileSize, tileSize] = new Microsoft.Xna.Framework.Rectangle(x, y, 20, 20); } } First off, I'm not sure how to initialize the array groundBounds (I don't know how big to make it). Also, I'm not entirely sure how to go about adding information to groundBounds. I want to add a Rectangle for each tile in the level. Preferably I'd only make a Rectangle for those tiles accessible by the player, and not background tiles, but that's for a different day. FYI, the map was made with a freeware program called Realm Factory.

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  • vector collision on polygon in 3d space detection/testing?

    - by LRFLEW
    In the 3d fps in java I'm working on, I need a bullet to be fired and to tell if it hit someone. All visual objects in the game are defined through OpenGL, so the object it can be colliding with can be any drawable polygon (although they will most likely be triangles and rectangles anyways). The bullet is not an object, but will be treated as a vector that instantaneously moves all the way across the map (like the snipper riffle in Halo). What's the best way to detect/test collisions with the polygon and the vector. I have access to OpenCL, however I have absolutely no experience with it. I am very early in the developmental stage, so if you think there's a better way of going about this, feel free to tell me (I barley have a player model to collide with anyways, so I'm flexible with it). Thanks

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  • How to find collision detection side between two objects?

    - by user2362369
    I am using box2D and I have two objects, one is bouncy ball and the other one is block. I'd like to find which side of the block is collided with, so I can only make the ball bounce when it hits the top. I tried to implement many things like fixture data and by detecting position, using manifold but not get the accurate result. I also tried to calculate distance between two object but all went wrong.

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  • Only Integrating Box2D collision detection in my 2d engine?

    - by Mr.Gando
    I have integrated box2d in my engine, ( Debug Draw, etc. ) and with a world I can throw in some 2d squares/rectangles etc. I saw this post, where the user is basically not using a world for collision detection, however the user doesn't explain anything about how he's using the manifold (b2Manifold), etc. Another post, is in the cocos2d forum, ( scroll down to the user Lam in the third reply ) Could anyone help me a bit with this?, basically want to add collision detection without the need of using b2World ,etc etc. Thanks a lot!

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  • Calculate angle of moving ball after collision with angled or sloped wall that is a 2D line segment

    - by Ben Mc
    If you have a "ball" inside a 2D polygon, made up of say, 4 line segments that act as bounding walls, how do you calculate the angle of the ball after the collision with the irregularly sloped wall? I know how to make the ball bounce if the wall is horizontal, vertical, or at a 45 degree angle. I also have my code setup to detect a collision with the wall. I've read about dot products and normals, but I cannot figure out how to implement these in Java / Android. I'm completely stumped and feel like I've looked up everything 10 pages deep in Google 10 times now. I'm burned out trying to figure this out, I hope someone can help.

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  • Collision detection on sub views contained in 2 separate parent UIViews?

    - by Chris
    Hi All, I originally setup some conditions using CGRectIntersectsRect for some collision detection which worked fine. In the greater scale of things I only need part of the view to be detected. So originally within the ViewController it was comparing 2 UIviews. Now what I need to do is collision detection of subViews within 2 different UIViews that are contained in a view in which the view controller does the logic. My script is no longer working as I suspect CGRectIntersectsRect only compares frames within the same view? I'll keep digging to confirm this. Any ways around this? Is it possible for example to get the x and y pos of the sub view in relation to the main view that's performing the logic?

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  • Optimizing multiple dispatch notification algorithm in C#?

    - by Robert Fraser
    Sorry about the title, I couldn't think of a better way to describe the problem. Basically, I'm trying to implement a collision system in a game. I want to be able to register a "collision handler" that handles any collision of two objects (given in either order) that can be cast to particular types. So if Player : Ship : Entity and Laser : Particle : Entity, and handlers for (Ship, Particle) and (Laser, Entity) are registered than for a collision of (Laser, Player), both handlers should be notified, with the arguments in the correct order, and a collision of (Laser, Laser) should notify only the second handler. A code snippet says a thousand words, so here's what I'm doing right now (naieve method): public IObservable<Collision<T1, T2>> onCollisionsOf<T1, T2>() where T1 : Entity where T2 : Entity { Type t1 = typeof(T1); Type t2 = typeof(T2); Subject<Collision<T1, T2>> obs = new Subject<Collision<T1, T2>>(); _onCollisionInternal += delegate(Entity obj1, Entity obj2) { if (t1.IsAssignableFrom(obj1.GetType()) && t2.IsAssignableFrom(obj2.GetType())) obs.OnNext(new Collision<T1, T2>((T1) obj1, (T2) obj2)); else if (t1.IsAssignableFrom(obj2.GetType()) && t2.IsAssignableFrom(obj1.GetType())) obs.OnNext(new Collision<T1, T2>((T1) obj2, (T2) obj1)); }; return obs; } However, this method is quite slow (measurable; I lost ~2 FPS after implementing this), so I'm looking for a way to shave a couple cycles/allocation off this. I thought about (as in, spent an hour implementing then slammed my head against a wall for being such an idiot) a method that put the types in an order based on their hash code, then put them into a dictionary, with each entry being a linked list of handlers for pairs of that type with a boolean indication whether the handler wanted the order of arguments reversed. Unfortunately, this doesn't work for derived types, since if a derived type is passed in, it won't notify a subscriber for the base type. Can anyone think of a way better than checking every type pair (twice) to see if it matches? Thanks, Robert

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  • What is the best way to solve an Objective-C namespace collision?

    - by Mecki
    Objective-C has no namespaces; it's much like C, everything is within one global namespace. Common practice is to prefix classes with initials, e.g. if you are working at IBM, you could prefix them with "IBM"; if you work for Microsoft, you could use "MS"; and so on. Sometimes the initials refer to the project, e.g. Adium prefixes classes with "AI" (as there is no company behind it of that you could take the initials). Apple prefixes classes with NS and says this prefix is reserved for Apple only. So far so well. But appending 2 to 4 letters to a class name in front is a very, very limited namespace. E.g. MS or AI could have an entirely different meanings (AI could be Artificial Intelligence for example) and some other developer might decide to use them and create an equally named class. Bang, namespace collision. Okay, if this is a collision between one of your own classes and one of an external framework you are using, you can easily change the naming of your class, no big deal. But what if you use two external frameworks, both frameworks that you don't have the source to and that you can't change? Your application links with both of them and you get name conflicts. How would you go about solving these? What is the best way to work around them in such a way that you can still use both classes? In C you can work around these by not linking directly to the library, instead you load the library at runtime, using dlopen(), then find the symbol you are looking for using dlsym() and assign it to a global symbol (that you can name any way you like) and then access it through this global symbol. E.g. if you have a conflict because some C library has a function named open(), you could define a variable named myOpen and have it point to the open() function of the library, thus when you want to use the system open(), you just use open() and when you want to use the other one, you access it via the myOpen identifier. Is something similar possible in Objective-C and if not, is there any other clever, tricky solution you can use resolve namespace conflicts? Any ideas? Update: Just to clarify this: answers that suggest how to avoid namespace collisions in advance or how to create a better namespace are certainly welcome; however, I will not accept them as the answer since they don't solve my problem. I have two libraries and their class names collide. I can't change them; I don't have the source of either one. The collision is already there and tips on how it could have been avoided in advance won't help anymore. I can forward them to the developers of these frameworks and hope they choose a better namespace in the future, but for the time being I'm searching a solution to work with the frameworks right now within a single application. Any solutions to make this possible?

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  • How do you resolve the common naming collision between type and object?

    - by Catskul
    Since the standard c# convention is to capitalize the first letter of public properties, the old c++ convention of initial capital for type names, and initial lowercase for non-type names does not prevent the classic name collision where the most obvious object name matches the type name: class FooManager { public BarManager BarManager { get; set; } // Feels very wrong. // Recommended naming convention? public int DoIt() { // 1st and 2nd Bar Manager are different symbols return BarManager.Blarb + BarManager.StaticBlarb; } } class BarManager { public int Blarb { get; set; } public static int StaticBlarb { get; set; } } It seems to compile, but feels so wrong. Is there a recommend naming convention to avoid this?

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  • Entity Type specific updates in entity component system

    - by Nathan
    I am currently familiarizing myself with the entity component paradigm. For an example, take a collision system, that detects if entities collide and if they do let them explode. So the collision system has to test collision based on the position component and then set the state of those entities to exploding. But what if the "effect" (setting the state to exploding) is different for different entities? For example, a ship fades out while for an asteroid a particle system must be created. Since entities and components are only data, this must happen in some system. The collision system could do it, but then it must switch over the entity type, which in my opinion is a cumbersome and difficult to extend solution. So how do I trigger "entity type dependend" updates on an entity?

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  • C++ and SDL resource management for 2D game

    - by KuruptedMagi
    My first question is about stateManagers. I do not use the singleton pattern (read many random posts with various reasons not to use it), I have gameStateManager which runs the pointer cCurrentGameState-render(), etc. I want to make a transitioning game, this engine should ideally cover both a platformer and a bird's eye RPG (with some recoding, I just mean the base engine), both of which will load different levels and events, such as world map, dungeon, shops, etc. So I then thought, rather then having to store all this data within all the states, I would break the engine into gameStates, and playStates... when gameState reaches gameStatePlay(), gameStatePlay simply runs the usual handleInput, logic, and render for the playStates, just as the low level gameStateManager does. This lets me store all the player data within the base playstate class without storing useless data in the gameStates. Now I have added a seperate mapEditor, which uses editorStates from gameStateEditor. Is this too much usage of the gameState concept? It seems to work pretty well for me, so I was wondering if I am too far off a common implementation of this. My second question is on image resources. I have my sprite class with nothing but static members, mainly loadImage, applySurface, and my screen pointer. I also have a map pairing imageName enums with actual SDL_Surface pointers, and one pairing clipNumber enums with a wrapper class for a vector of clips, so that each reference in the map can have different amounts of clips with different sizes. I thought it would be better to store all these images, and screen within one static body, since 20 different goblins all use the same sprite sheet, and all need to print to the same screen, and of course, this way I do not need to pass my screen reference to every little entity. The imageMap seems to work very well, I can even add the ability to search through the map at creation of entity type to see if a particular image at creation, creating if it doesnt exist, and destroying the image if the last entity that needs it was just destroyed. The vectored clip map however, seems to take too long to initialize, so if i run past the state that initializes them to fast, the game crashes <. Plus, the clip map call is half of this line =P SPRITE::applySurface( cEditorMap.cTiles[x][y].iX, cEditorMap.cTiles[x][y].iY, SPRITE::mImages[ IMAGE_TILEMAP ], SPRITE::screen, SPRITE::mImageClips[IMAGE_TILEMAP]->clips.at( cEditorMap.cTiles[x][y].iTileType ) ); Again, do I have the right idea? I like the imageMap, but am I better off with each entity storing its own clips? My last question is about collision detection. I only grasp the basics, will look at per-pixel and circular soon, but how can I determine which side the collision comes from with just the basic square collision detection, I tried breaking each entity into 4 collision zones, but that just gave me problems with walking through walls and the like <. Also, is per-pixel color collision a good way to decide what collision just occured, or is checking multiple colors for multiple entities too taxing each cycle?

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  • Question regarding CGRectIntersectsRect and rotated rectangular image

    - by user309030
    Hi guys, I've got a long rectangular image which is rotated at different kind of angles. However the frame of the rectangular image does not rotate along with the image and instead, the rotation causes the frame to to become larger to fit the rotated image. So when I used CGRectIntersectsRect, the collision detection is totally off because the other image colliding with the rectangular image will collide before it even reaches the visible area of the rect image. In case you don't really know what I'm talking about, have a look at the ascii drawing: normal rectangular image frame, O - pixels, |, – - frame |----------| |OOOOOOOOOO| |----------| after rotation |----------| |O | | O | | O | | O | | O | | O | | O | | O | | O | |----------| I've read through some of the collision articles but all of them are talking about collision with a normal straight rectangle and what I really want is collision with a slanted image, preferably pixel collision detection. TIA for any suggestions made.

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  • When is it safe to use a broken hash function?

    - by The Rook
    It is trivial to use a secure hash function like SHA256 and continuing to use md5 is reckless behavior. However, there are some complexities to hash function vulnerabilities that I would like to better understand. Collisions have been generated for md4 and md5. According to NIST md5() is not a secure hash function. It only takes 2^39th operations to generate a collision and should never be used for passwords. However SHA1 is vulnerable to a similar collision attack in which a collision can be found in 2^69 operations, where as brute force is 2^80th. No one has generated a sha1 collision and NIST still lists sha1 as a secure message digest function. So when is it safe to use a broken hash function? Even though a function is broken it can still be "big enough". According to Schneier a hash function vulnerable to a collsion attack can still be used as an HMAC. I believe this is because the security of an HMAC is Dependant on its secret key and a collision cannot be found until this key is obtained. Once you have the key used in a HMAC its already broken, so its a moot point. What hash function vulnerabilities would undermine the security of an HMAC? Lets take this property a bit further. Does it then become safe to use a very weak message digest like md4 for passwords if a salt is perpended to the password? Keep in mind the md4 and md5 attacks are prefixing attacks, and if a salt is perpended then an attacker cannot control the prefix of the message. If the salt is truly a secret, and isn't known to the attacker, then does it matter if its a appended to the end of the password? Is it safe to assume that an attacker cannot generate a collision until the entire message has been obtained? Do you know of other cases where a broken hash function can be used in a security context without introducing a vulnerability? (Please post supporting evidence because it is awesome!)

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  • In a 2D platform game, how to ensure the player moves smoothly over sloping ground?

    - by Kovsa
    See image: http://i41.tinypic.com/huis13.jpg I'm developing a physics engine for a 2D platform game. I'm using the separating axis theorem for collision detection. The ground surface is constructed from oriented bounding boxes, with the player as an axis aligned bounding box. (Specifically, I'm using the algorithm from the book "Realtime Collision Detection" which performs swept collision detection for OBBs using SAT). I'm using a fairly small (close to zero) restitution coefficient in the collision response, to ensure that the dynamic objects don't penetrate the environment. The engine mostly works fine, it's just that I'm concerned about some edge cases that could possibly occur. For example, in the diagram, A, B and C are the ground surface. The player is heading left along B towards A. It seems to me that due to inaccuracy, the player box could be slightly below the box B as it continues up and left. When it reaches A, therefore, the bottom left corner of the player might then collide with the right side of A, which would be undesirable (as the intention is for the player to move smoothly over the top of A). It seems like a similar problem could happen when the player is on top of box C, moving left towards B - the most extreme point of B could collide with the left side of the player, instead of the player's bottom left corner sliding up and left above B. Box2D seems to handle this problem by storing connectivity information for its edge shapes, but I'm not really sure how it uses this information to solve the problem, and after looking at the code I don't really grasp what it's doing. Any suggestions would be greatly appreciated.

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  • Storing large array of tiles, but allowing easy access to data

    - by Cyral
    I've been thinking about this for a while. I have a 2D tile bases platformer in XNA with a large array of tile data, I've been running into memory problems with large maps. (I will add chunks soon!) Currently, Each tile contains an Item along with other properties like how its rotated, if it has forground / background, etc. An Item is static and has properties like the name, tooltip, type of item, how much light it emits, the collision it does to player, etc. Examples: public class Item { public static List<Item> Items; public Collision blockCollisionType; public string nameOfItem; public bool someOtherVariable,etc,etc public static Item Air public static Item Stone; public static Item Dirt; static Item() { Items = new List<Item>() { (Stone = new Item() { nameOfItem = "Stone", blockCollisionType = Collision.Solid, }), (Air = new Item() { nameOfItem = "Air", blockCollisionType = Collision.Passable, }), }; } } Would be an Item, The array of Tiles would contain a Tile for each point, public class Tile { public Item item; //What type it is public bool onBackground; public int someOtherVariables,etc,etc } Now, Most would probably use an enum, or a form of ID to identify blocks. Well my system is really nice just to find out about an item. I can simply do tiles[x,y].item.Name To get the name for example. I realized my Item property of the tile is over 1000 Bytes! Wow! What I'm looking for is a way to use an ID (Int or byte depending on how many items) instead of an Item but still have a method for retreiving data about the type of item a tile contains.

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  • How can I create and animate 2D skeletons for HTML5 Javascript games? [on hold]

    - by user414209
    I'm trying to make a 2D fighting game in HTML5(somewhat like street fighter). So basically there are two players, one AI and one Human. The players need to have animations for the body movements. Also, there needs to be some collision detection system. I'm using createjs for coding but to design models/objects/animations, I need some other software. So I'm looking for a software that can: easily make custom animation of 2d objects. The objects structure(skeleton etc.) will be same once defined but need to be defined once. Can export the animations and models in a js readable format(preferably json) Collision detection can be done easily after the exported format is loaded in a game engine. For point 1, I'm looking for some generic skeleton based animation. Sprite-sheet based animations will be difficult for collision detection.

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  • How display path ball will bounce?

    - by boolean
    I'm trying to figure out a way to show the path a ball will travel, so that the player can line up a shot before they fire the ball. I can't think of a way to calculate this path in advance and show it to the player, especially if it involves collision detection. At first I thought I would run the game at a super high speed for one update, plot the path with some dotted lines where the ball bounced, and then in the next frame hide the 'tracer' ball. This seems to have two issues - Calculating collision detection without actually updating the frames and collision detection getting less reliable at high speeds. If they were straight lines I think I could figure this out in a while loop, but trying to take into account the speed of the ball, the curve of the path, the reflecting from other objects..it all seems a bit much. I'm not looking for any code and this isn't a platform specific question, more just help trying to figure out conceptually how this would work. Can this be done? Are there techniques to achieve this?

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  • Physics for moving blocks

    - by Gabson
    I'm working on a 2D game for windows phone where the player moves blocks around to bounce a laser beams. I need to create some simple physics for moving the blocks. For the moment I have a simple collision class, telling me if two rectangles collide. But that's not enough because when I'm moving a block the rectangle/rectangle function doesn't work. By Doesn't work i mean,I manage the collision but I don't how to stop the block mooving while the user sliding the block. The collision response for the block I want is if the user tries to slide it on another object, the block should slide up against the other object and not overlap. How would I go about implementing this functionality?

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  • how to stop enemies from moving to one point when lots of them are chasing one object [duplicate]

    - by BBgun
    This question already has an answer here: Is there a simple way to stop enemies standing in the same spot? 8 answers i am making a top down game which lots of enemies are chasing one guy. then,enemies would move to one point without any collision,they just overlay each other. so ,is there any simple way to make them feel more real? make them not overlay with each other? ================================= i have tried the solution using boundbox to check collision, but i still very puzzled about what to do with the collision. i have a bad solution.it doesn't work well. my solution in simple: foreach(around_enemy_arr in other) { vector a = normalize(self.positionvector - other.positionvector); self.move_vector = self.move_vector + a; } this can work,but when plenty of enemies come very close to each other,they would shake. i am sooooo confused. please help.

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  • RTS Movement + Navigation + Destination

    - by Oliver Jones
    I'm looking into building my own simple RTS game, and I'm trying to get my head around the movement of single, and multi selected units. (Developing in Unity) After much research, I now know that its a bigger task than I thought. So I need to break it down. I already have an A* navigation system with static obstacles taken into account. I don't want to worry about dynamic local avoidance right now. So I guess my first break down question would be: How would I go about moving mutli units to the same location. Right now - my units move to the location, but because they're all told to go to the same location, they start to 'fight' over one another to get there. I think theres two paths to go down: 1) Give each individual unit a separate destination point that is close to the 'master' destination point - and get the units to move to that. 2) Group my selected units in a flock formation, and move that entire flock group towards the destination point. Question about each path: 1a) How can I go about finding a suitable destination point that is close to the master destination? What happens if there isn't a suitable destination point? 1b) Would this be more CPU heavy? As it has to compute a path for each unit? (40 unit count). 2a) Is this a good idea? Not giving the units themselves a destination, but instead the flock (which holds the units within). The units within the flock could then maintain a formation (local avoidance) - though, again local avoidance is not an issue at this current time. 2b) Not sure what results I would get if I have a flock of 5 units, or a flock of 40 units, as the radius would be greater - which might mess up my A* navigation system. In other words: A flock of 2 units will be able to move down an alleyway, but a flock of 40 wont. But my nav system won't take that into account. I would appreciate any feedback. Kind regards, Ollie Jones

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  • How can you deflect a direction/magnitude vector based on a direction/magnitude vector and a collided triangle?

    - by JeanOTF
    So, I have a Triangle-AABB collision algorithm and I have it returning the triangle that the AABB collided with. I was hoping with the 3 vectors of the triangle and the direction/magnitude of the movement would let me determine a deflected vector so that when you run against the wall at an angle you move slower, depending on the angle of collision, but along side the wall. This would remove the sticky collision problem with only moving when there is not a collision. Any suggestions or references would be greatly appreciated! Thanks.

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  • What technologies to use for a particle system with enormous calculation demand?

    - by Amir Rezaei
    I have a particle system with X particles. Each particle tests for collision with other particles. This gives X*X = X^2 collision tests per frame. For 60f/s, this corresponds to 60*X^2 collision detection per second. What is the best technological approach for these intensive calculations? Should I use F#, C, C++ or C#, or something else? The following are constraints The code is written in C# with the latest XNA Multi-threaded may be considered No special algorithm that tests the collision with the nearest neighbors or that reduces the problem The last constraint may be strange, so let me explain. Regardless constraint 3, given a problem with enormous computational requirement what would be the best approach to solve the problem. An algorithm reduces the problem; still the same algorithm may behave different depending on technology. Consider pros and cons of CLR vs native C.

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  • hash fragments and collisions cont.

    - by Mark
    For this application I've mine I feel like I can get away with a 40 bit hash key, which seems awfully low, but see if you can confirm my reasoning (I want a small key because I want a small filename and the key will be converted to a filename): (Note: only accidental collisions a concern - no security issues.) A key point here is that the population in question is divided into groups, and a collision is only relevant if it occurs within the same group. A "group" is a directory on a user's system (the contents of files are hashed and a collision is only relevant if it occurs for files within the same directory). So with speculating roughly 100,000 potential users, say 2^17, that corresponds to 2^18 "groups" assuming 2 directories per user on average. So with a 40 bit key I can expect 2^(20+9) files created (among all users) before a collision occurs for some user somewhere. (Or IOW 2^((40+18)/2), due to the "birthday effect".) That's an average 4096 unique files created per user, for 2^17 users, before a single collision occurs for some user somewhere. And then that long again before another collision occurs somewhere (right?)

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