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  • Bullet Physic: Transform body after adding

    - by Mathias Hölzl
    I would like to transform a rigidbody after adding it to the btDiscreteDynamicsWorld. When I use the CF_KINEMATIC_OBJECT flag I am able to transform it but it's static (no collision response/gravity). When I don't use the CF_KINEMATIC_OBJECT flag the transform doesn't gets applied. So how to I transform non-static objects in bullet? DemoCode: btBoxShape* colShape = new btBoxShape(btVector3(SCALING*1,SCALING*1,SCALING*1)); /// Create Dynamic Objects btTransform startTransform; startTransform.setIdentity(); btScalar mass(1.f); //rigidbody is dynamic if and only if mass is non zero, otherwise static bool isDynamic = (mass != 0.f); btVector3 localInertia(0,0,0); if (isDynamic) colShape->calculateLocalInertia(mass,localInertia); btDefaultMotionState* myMotionState = new btDefaultMotionState(); btRigidBody::btRigidBodyConstructionInfo rbInfo(mass,myMotionState,colShape,localInertia); btRigidBody* body = new btRigidBody(rbInfo); body->setCollisionFlags(body->getCollisionFlags()|btCollisionObject::CF_KINEMATIC_OBJECT); body->setActivationState(DISABLE_DEACTIVATION); m_dynamicsWorld->addRigidBody(body); startTransform.setOrigin(SCALING*btVector3( btScalar(0), btScalar(20), btScalar(0) )); body->getMotionState()->setWorldTransform(startTransform);

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  • What kinds of demos are good to make for a software engineer job

    - by user23012
    I have created my cv site and sent out my demos for a while now, but most of my demos are either from my course or games related since my course was a games programming course, I was wondering what kind of demos are good to show off my skills in programming in general. These are what i already have Pennies:just a simple game first coursework i did. Compiler:coursework for compiler writing module Pongout: basic a pong game in 68k using colour detection Snake: snake in 68k same thing as the pong Game Cube Maze: gamecube work BeatmyBot: basic Ai Basic plat-former game: 2d game with different types of collision Turing Lambda Simulation: my dissertation Turing machine simulated in Miranda. alpha and Beta reduction,and SKI calculus simulated in the Turing machine. What I am asking here is what kind of demos are good to add or have, i have been looking and have hit a tough spot I cant think of anything to make more than games. so for a general graduate software engineer what types would be good examples? EDIT: since responding to the comments bellow well for what languages well my main one would be C++, followed by Java, Erlang and abit of Haskell

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  • Game-a-Week One

    - by Matt Christian
    Anyone who chats with me on a semi-regular basis knows I am absolutely horrible at completing something from beginnning to end.  Often times I'll begin something, lose interest at some point, and end up moving onto the next thing.  For example, I have 1/2 a full game created, 1/3 of a novel written, and half of a model set created.  Needless to say, unless I have some sort of pressure to finish something I don't stick to it. Recently however one of my online buddies challenged me to create a simple game.  The start date was last Thursday and the final game needed to be delivered by this next Sunday (giving me just over a week).  However, I am going out of town this Friday so will need to deliver it by Thursday, giving me exactly 1 week to develop a game.  Here is what the game needed to include: The player should be able to shoot Shooting things should score points Sounds very simple, but given a single week to produce all art assets plus the game isn't an easy task.  So far I've developed: An animated Main Menu that loads via script files, allows the user to start a new game or exit the game The game is 3D and the player can move around the play area with an 'over-the-shoulder' camera HUD elements are drawn to display the player's current score When the player presses Esc they are shown a pause menu where they can resume the game by pressing Esc again, or quit the game by pressing Space There are also 2 items implemented that don't work perfectly: JigLibX physics library implementation On the main menu there is an arrow symbol that rotates to always point at your mouse I've got 2 days of development left so hopefully I can get collision working, some of the art cleaned up, and some more of the camera functionality working.  Also, I'll need to take some time to package the game up which hopefully shouldn't take too long.

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  • What is a currently a good game stack for simple Javascript 2D multiplatform game?

    - by JacobusR
    I'm looking for advice from someone can help me avoid common pitfalls in developing light weight, quick-to-market games. Yeah, I've heard of Google ;-), but a trip down Google lane does not beat solid experience from someone who has been down this path. I'm looking for advice from someone who works alone, or in a small team, and has developed some 2D games for mobile. My game ideas don't require intensive graphics, just simple arcade style glyphs and collision detection. My experience is mostly with Scala, Java and web technologies (Javascript, CSS, SVG, HTML, etc). My question is: Is there a nice stack that someone can suggest that will be a good fit for my skillset? I'm considering Javascript for simple 2D shooter games with simple multiplayer games being supported with a Scala server-side written on Spray. Is this silly? Should I rather look into things such as Unity 3D, and use it in 2D mode? For the actual game engine, something like the Sparrow Framework would be great, but it needs to be multiplatform.

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  • GetContactList stops reporting collisions on welded bodies

    - by Henrique Jung
    I have some strange problem with my game which uses Box2D as physics engine and I'm out of ideas on what I can do to solve it. My game is a class assignment where I need to build a simple game where the main character moves in a 2D environment while square blocks comes from below him. Each time a collision occurs, that block is attached to the character using a weld joint, when three blocks of the same colors are together, they annihilate themselves(an effect similar to Bejeweled). I'm using a recursive function to iterate through all the attached blocks of a given block to see if there are enough blocks for them to be deleted. I'm using GetContactList function to iterate through the list of contacts to see which blocks are adjacent to each other. The results are quite disappointing, the blocks only get annihilated in few cases. After a lot of debugging, I found the issue, but I still don't know how to solve. My issue is: after some time, GetContactList STOPS returning contacts (return NULL) to blocks that were already attached for some time. I spent some time reading the Box2D manual as well as some tutorials and still didn't find any clue of what is happening. Below there's some simplified version of the code that I wrote. for(int a = 0; a < blocksList.size(); a++) { blocksList[a].BuildConnections(); } And on BuildConnections b2ContactEdge* edge = body->GetContactList(); while(edge != NULL) { if (long_check_to_see_if_there's_a_block_nearby) { // add itself to the list to be anihilated globalList.push_back(this); //if there's, call BuildConnections again on the adjacent block adjacentBody->GetUserData()->BuildConnections; } edge = edge->next; } I know that there's another issue related to circular inclusions, but I fairly sure that this problem isn't causing the problem with the collisions. You can download my entire code from this page if you'd like http://code.google.com/p/fellz/source/list

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  • 2D/Isometric map algorithm

    - by Icarus Cocksson
    First of all, I don't have much experience on game development but I do have experience on development. I do know how to make a map, but I don't know if my solution is a normal or a hacky solution. I don't want to waste my time coding things, and realise they're utterly crap and lose my motivation. Let's imagine the following map. (2D - top view - A square) X: 0 to 500 Y: 0 to 500 My character currently stands at X:250,Y:400, somewhere near center of 100px above bottom and I can control him with my keyboard buttons. LEFT button does X--, UP button does Y-- etc. This one is kid's play. I'm asking this because I know there are some engines that automate this task. For example, games like Diablo 3 uses an engine. You can pretty much drag drop a rock to map, and it is automatically being placed here - making player unable to pass through/detect the collision. But what the engine exactly does in the background? Generates a map like mine, places a rock at the center, and checks it like: unmovableObjects = array('50,50'); //we placed a rock at 50,50 location if(Map.hasUnmovableObject(CurrentPlayerX, CurrentPlayerY)) { //unable to move } else { //able to move } My question is: Is this how 2D/Isometric maps are being generated or there is a different and more complex logic behind them?

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  • Doing powerups in a component-based system

    - by deft_code
    I'm just starting really getting my head around component based design. I don't know what the "right" way to do this is. Here's the scenario. The player can equip a shield. The the shield is drawn as bubble around the player, it has a separate collision shape, and reduces the damage the player receives from area effects. How is such a shield architected in a component based game? Where I get confused is that the shield obviously has three components associated with it. Damage reduction / filtering A sprite A collider. To make it worse different shield variations could have even more behaviors, all of which could be components: boost player maximum health health regen projectile deflection etc Am I overthinking this? Should the shield just be a super component? I really think this is wrong answer. So if you think this is the way to go please explain. Should the shield be its own entity that tracks the location of the player? That might make it hard to implement the damage filtering. It also kinda blurs the lines between attached components and entities. Should the shield be a component that houses other components? I've never seen or heard of anything like this, but maybe it's common and I'm just not deep enough yet. Should the shield just be a set of components that get added to the player? Possibly with an extra component to manage the others, e.g. so they can all be removed as a group. (accidentally leave behind the damage reduction component, now that would be fun). Something else that's obvious to someone with more component experience?

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  • Can Google Employees See My Saved Google Chrome Passwords?

    - by Jason Fitzpatrick
    Storing your passwords in your web browser seems like a great time saver, but are the passwords secure and inaccessible to others (even employees of the browser company) when squirreled away? Today’s Question & Answer session comes to us courtesy of SuperUser—a subdivision of Stack Exchange, a community-driven grouping of Q&A web sites. The Question SuperUser reader MMA is curious if Google employees have (or could have) access to the passwords he stores in Google Chrome: I understand that we are really tempted to save our passwords in Google Chrome. The likely benefit is two fold, You don’t need to (memorize and) input those long and cryptic passwords. These are available wherever you are once you log in to your Google account. The last point sparked my doubt. Since the password is available anywhere, the storage must in some central location, and this should be at Google. Now, my simple question is, can a Google employee see my passwords? Searching over the Internet revealed several articles/messages. Do you save passwords in Chrome? Maybe you should reconsider: Talks about your passwords being stolen by someone who has access to your computer account. Nothing mentioned about the central storage security and vulnerability. There is even a response from Chrome browser security tech lead about the first issue. Chrome’s insane password security strategy: Mostly along the same line. You can steal password from somebody if you have access to the computer account. How to Steal Passwords Saved in Google Chrome in 5 Simple Steps: Teaches you how to actually perform the act mentioned in the previous two when you have access to somebody else’s account. There are many more (including this one at this site), mostly along the same line, points, counter-points, huge debates. I refrain from mentioning them here, simply carry a search if you want to find them. Coming back to my original query, can a Google employee see my password? Since I can view the password using a simple button, definitely they can be unhashed (decrypted) even if encrypted. This is very different from the passwords saved in Unix-like OS’s where the saved password can never be seen in plain text. They use a one-way encryption algorithm to encrypt your passwords. This encrypted password is then stored in the passwd or shadow file. When you attempt to login, the password you type in is encrypted again and compared with the entry in the file that stores your passwords. If they match, it must be the same password, and you are allowed access. Thus, a superuser can change my password, can block my account, but he can never see my password. So are his concerns well founded or will a little insight dispel his worry? The Answer SuperUser contributor Zeel helps put his mind at ease: Short answer: No* Passwords stored on your local machine can be decrypted by Chrome, as long as your OS user account is logged in. And then you can view those in plain text. At first this seems horrible, but how did you think auto-fill worked? When that password field gets filled in, Chrome must insert the real password into the HTML form element – or else the page wouldn’t work right, and you could not submit the form. And if the connection to the website is not over HTTPS, the plain text is then sent over the internet. In other words, if chrome can’t get the plain text passwords, then they are totally useless. A one way hash is no good, because we need to use them. Now the passwords are in fact encrypted, the only way to get them back to plain text is to have the decryption key. That key is your Google password, or a secondary key you can set up. When you sign into Chrome and sync the Google servers will transmit the encrypted passwords, settings, bookmarks, auto-fill, etc, to your local machine. Here Chrome will decrypt the information and be able to use it. On Google’s end all that info is stored in its encrpyted state, and they do not have the key to decrypt it. Your account password is checked against a hash to log in to Google, and even if you let chrome remember it, that encrypted version is hidden in the same bundle as the other passwords, impossible to access. So an employee could probably grab a dump of the encrypted data, but it wouldn’t do them any good, since they would have no way to use it.* So no, Google employees can not** access your passwords, since they are encrypted on their servers. * However, do not forget that any system that can be accessed by an authorized user can be accessed by an unauthorized user. Some systems are easier to break than other, but none are fail-proof. . . That being said, I think I will trust Google and the millions they spend on security systems, over any other password storage solution. And heck, I’m a wimpy nerd, it would be easier to beat the passwords out of me than break Google’s encryption. ** I am also assuming that there isn’t a person who just happens to work for Google gaining access to your local machine. In that case you are screwed, but employment at Google isn’t actually a factor any more. Moral: Hit Win + L before leaving machine. While we agree with zeel that it’s a pretty safe bet (as long as your computer is not compromised) that your passwords are in fact safe while stored in Chrome, we prefer to encrypt all our logins and passwords in a LastPass vault. Have something to add to the explanation? Sound off in the the comments. Want to read more answers from other tech-savvy Stack Exchange users? Check out the full discussion thread here.     

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  • Doing powerups in a component-based system

    - by deft_code
    I'm just starting really getting my head around component based design. I don't know what the "right" way to do this is. Here's the scenario. The player can equip a shield. The the shield is drawn as bubble around the player, it has a separate collision shape, and reduces the damage the player receives from area effects. How is such a shield architected in a component based game? Where I get confused is that the shield obviously has three components associated with it. Damage reduction / filtering A sprite A collider. To make it worse different shield variations could have even more behaviors, all of which could be components: boost player maximum health health regen projectile deflection etc Am I overthinking this? Should the shield just be a super component? I really think this is wrong answer. So if you think this is the way to go please explain. Should the shield be its own entity that tracks the location of the player? That might make it hard to implement the damage filtering. It also kinda blurs the lines between attached components and entities. Should the shield be a component that houses other components? I've never seen or heard of anything like this, but maybe it's common and I'm just not deep enough yet. Should the shield just be a set of components that get added to the player? Possibly with an extra component to manage the others, e.g. so they can all be removed as a group. (accidentally leave behind the damage reduction component, now that would be fun). Something else that's obvious to someone with more component experience?

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  • What is the best way to check if there is overlap between player and static, non-collidable items in bullet physic engine

    - by tigrou
    I'd like to add non collidable objects (eg: power ups, items, ...) in a game world using Bullet Physics Engine and to know if there is collision between player and them. Some info : there is a lot of items ( 1000), all are box shapes and they don't overlap. Here is things i have tried : btDbvt* bvtItems = new btDbvt(); //btDbvt is a hierachical AABB tree, used by Bullet foreach(var item ...) { btDbvtVolume volume = ... //compute item AABB; bvtItems->insert(volume, (void*)someExtraData); } Then, to find collisions between items and player : playerRigidBody->getAabb(min, max); btDbvtVolume playervolume = ... //compute player AABB bvtItems->collideTV(bvtItems->m_root, playervolume, *someCollisionHandler); This works fairly well (and its very fast), however, there is a problem : it only check items AABB against player AABB. That loss of precision is acceptable for items but not for player which is not a box. It would actually need another check to make sure player really collide with item but i don't know how to do this in Bullet. It would have been nice to have a function like this : playerRigidBody->checkCollisionWithAABB(); After doing trying that, I discovered that a btGhostObject exist and seems to have been made for that. I changed my code like this : foreach(var item...) { btCollisionObject* ghostObject = new btGhostObject(); ghostObject->setCollisionShape(boxShape); ghostObject->setCollisionFlags(ghostObject->getCollisionFlags() | btCollisionObject::CF_NO_CONTACT_RESPONSE); startTransform.setOrigin(...); //item position ghostObject->setWorldTransform(startTransform); dynamicsWorld->addCollisionObject(ghostObject, btBroadphaseProxy::SensorTrigger, btBroadphaseProxy:: CharacterFilter); } It also works ok, but there is a huge fps drop (almost ten times slower) which is not acceptable. Maybe there is something missing (forget set a flag) and Bullet is doing extra job for nothing or maybe all that ghostObjects are polluting broad phase and ghostObject is not the right thing for that. Any help would be appreciated.

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  • How do I prevent other dynamic bodies from affecting the player's velocity with Box2D?

    - by Milo
    I'm working on my player object for my game. PhysicsBodyDef def; def.fixedRotation = true; def.density = 1.0f; def.position = Vec2(200.0f, 200.0f); def.isDynamic = true; def.size = Vec2(50.0f,200.0f); m_player.init(def,&m_physicsEngine.getWorld()); This is how he moves: b2Vec2 vel = getBody()->GetLinearVelocity(); float desiredVel = 0; if (m_keys[ALLEGRO_KEY_A] || m_keys[ALLEGRO_KEY_LEFT]) { desiredVel = -5; } else if (m_keys[ALLEGRO_KEY_D] || m_keys[ALLEGRO_KEY_RIGHT]) { desiredVel = 5; } else { desiredVel = 0; } float velChange = desiredVel - vel.x; float impulse = getBody()->GetMass() * velChange; //disregard time factor getBody()->ApplyLinearImpulse( b2Vec2(impulse,0), getBody()->GetWorldCenter(),true); This creates a few problems. First, to move the player at a constant speed he must be given a high velocity. The problem with this is if he just comes in contact with a small box, he makes it move a lot. Now, I can fix this by lowering his density, but then comes my main issue: I need other objects to be able to run into him, but when they do, he should be like a static wall and not move. I'm not sure how to do that without high density. I cannot use collision groups since I still need him to be solid toward other dynamic things. How can this be done? Essentially, how do I prevent other dynamic bodies from affecting the player's velocity?

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  • What is a technique for 2D ray-box intersection that is suitable for old console hardware?

    - by DJCouchyCouch
    I'm working on a Sega Genesis homebrew game (it has a 7mhz 68000 CPU). I'm looking for a way to find the intersection between a particle sprite and a background tile. Particles are represented as a point with a movement vector. Background tiles are 8 x 8 pixels, with an (X,Y) position that is always located at a multiple of 8. So, really, I need to find the intersection point for a ray-box collision; I need to find out where along the edge of the tile the ray/particle hits. I have these two hard constraints: I'm working with pixel locations (integers). Floating point is too expensive. It doesn't have to be super exact, just close enough. Multiplications, divisions, dot products, et cetera, are incredibly expensive and are to be avoided. So I'm looking for an efficient algorithm that would fit those constraints. Any ideas? I'm writing it in C, so that would work, but assembly should be good as well.

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  • How do I draw anti-aliased holes in a bitmap

    - by gyozo kudor
    I have an artillery game (hobby-learning project) and when the projectile hits it leaves a hole in the ground. I want this hole to have antialiased edges. I'm using System.Drawing for this. I've tried with clipping paths, and drawing with a transparent color using gfx.CompositingMode = CompositingMode.SourceCopy, but it gives me the same result. If I draw a circle with a solid color it works fine, but I need a hole, a circle with 0 alpha values. I have enabled these but they work only with solid colors: gfx.CompositingQuality = CompositingQuality.HighQuality; gfx.InterpolationMode = InterpolationMode.HighQualityBicubic; gfx.SmoothingMode = SmoothingMode.AntiAlias; In the two pictures consider black as being transparent. This is what I have (zoomed in): And what I need is something like this (made with photoshop): This will be just a visual effect, in code for collision detection I still treat everything with alpha 128 as solid. Edit: I'm usink OpenTK for this game. But for this question I think it doesn't really matter probably it is gdi+ related.

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  • Running multiple box2D world objects on a server

    - by CharbelAbdo
    I'm creating a multiplayer game using LibGdx (with Box2d) and Kryonet. Since this is the first time I work on multiplayer games, I read a bit about server - client implementations, and it turns out that the server should handle important tasks like collision detection, hits, characters dying etc... Based on some articles (like the excellent Gabriel Gambetta Fast paced multiplayer series), I also know that the client should work in parallel to avoid the lag while the server responds to commands. Physics wise, each game will have 2 players, and any projectiles fired. What I'm thinking of doing is the following: Create a physics world on the client When the game is signaled to start, I create the same physics world on the server (without any rendering obviously). Whenever the player issues a command (move or fire), I send the command to the server and immediately start processing it on the client. When the server receives the command, it applies it on the server's world (set velocity etc...) Each 100ms, the server sends the new state to the client which corrects what was calculated locally. Any critical action (hit, death, level up) is calculated only on the server and sent to the client. Essentially, I would have a Box2d World object running on the server for each game in progress, in sync with the worlds running on the clients. The alternative would be to do my own calculations on the server instead of relying on Box2D to do them for me, but I'm trying to avoid that. My question is: Is it wise to have, for example, 1000 instances of the World object running and executing steps on the server? Tomcat used around 750 MBytes of memory when trying it without any object added to the world. Anybody tried that before? If not, is there any alternative? Google did not help me, are there any guidelines to use when you want to have physics on both the client and the server? Thanks for any help.

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  • How to build a "traffic AI"?

    - by Lunikon
    A project I am working on right now features a lot of "traffic" in the sense of cars moving along roads, aircraft moving aroun an apron etc. As of now the available paths are precalculated, so nodes are generated automatically for crossings which themselves are interconnected by edges. When a character/agent spawns into the world it starts at some node and finds a path to a target node by means of a simply A* algorithm. The agent follows the path and ultimately reaches its destination. No problem so far. Now I need to enable the agents to avoid collisions and to handle complex traffic situations. Since I'm new to the field of AI I looked up several papers/articles on steering behavior but found them to be too low-level. My problem consists less of the actual collision avoidance (which is rather simple in this case because the agents follow strictly defined paths) but of situations like one agent leaving a dead-end while another one wants to enter exactly the same one. Or two agents meeting at a bottleneck which only allows one agent to pass at a time but both need to pass it (according to the optimal route found before) and they need to find a way to let the other one pass first. So basically the main aspect of the problem would be predicting traffic movement to avoid dead-locks. Difficult to describe, but I guess you get what I mean. Do you have any recommendations for me on where to start looking? Any papers, sample projects or similar things that could get me started? I appreciate your help!

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  • Texture2D.GetData fails to return pixel colour data

    - by Chris Charabaruk
    Because I'm using sprite sheets instead of an individual texture per sprite, I need to pass in a Rectangle when calling Texture2D.GetData() in my collision detection for per-pixel tests. Unfortunately, without fail I get an ArgumentException percolated down from an internal method inside the Texture (not Texture2D) class. My code for getting the texture data looks like this: public override Color[] GetPixelData() { Color[] data = new Color[(int)size.Product()]; Rectangle rect = new Rectangle(hframe * (int)size.X, vframe * (int)size.Y, (int)size.X, (int)size.Y); #if DEBUG if (sprite.Bounds.Contains(rect) && sprite.Format == SurfaceFormat.Color) #endif sprite.GetData(0, rect, data, 0, 1); return data; } Even with the check to ensure I'm grabbing a valid rectangle and that the texture format matches what I'm trying to get, I still get that exception, claiming "The size of the data passed in is too large or too small for this resource." Unfortunately, the debugger won't let me check the locals within the Texture.ValidateTotalSize() method where the exception originates. Has anyone else had this problem and knows how to fix it? I'm relying on AABB testing only for now, but that doesn't really work for some of my game's entities due to odd shapes, rotation and scaling.

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  • Should I use an interface when methods are only similar?

    - by Joshua Harris
    I was posed with the idea of creating an object that checks if a point will collide with a line: public class PointAndLineSegmentCollisionDetector { public void Collides(Point p, LineSegment s) { // ... } } This made me think that if I decided to create a Box object, then I would need a PointAndBoxCollisionDetector and a LineSegmentAndBoxCollisionDetector. I might even realize that I should have a BoxAndBoxCollisionDetector and a LineSegmentAndLineSegmentCollisionDetector. And, when I add new objects that can collide I would need to add even more of these. But, they all have a Collides method, so everything I learned about abstraction is telling me, "Make an interface." public interface CollisionDetector { public void Collides(Spatial s1, Spatial s2); } But now I have a function that only detects some abstract class or interface that is used by Point, LineSegment, Box, etc.. So if I did this then each implementation would have to to a type check to make sure that the types are the appropriate type because the collision algorithm is different for each different type match up. Another solution could be this: public class CollisionDetector { public void Collides(Point p, LineSegment s) { ... } public void Collides(LineSegment s, Box b) { ... } public void Collides(Point p, Box b) { ... } // ... } But, this could end up being a huge class that seems unwieldy, although it would have simplicity in that it is only a bunch of Collide methods. This is similar to C#'s Convert class. Which is nice because it is large, but it is simple to understand how it works. This seems to be the better solution, but I thought I should open it for discussion as a wiki to get other opinions.

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  • Security in Robots and Automated Systems

    - by Roger Brinkley
    Alex Dropplinger posted a Freescale blog on Securing Robotics and Automated Systems where she asks the question,“How should we secure robotics and automated systems?”.My first thought on this was duh, make sure your robot is running Java. Java's built-in services for authentication, authorization, encryption/confidentiality, and the like can be leveraged and benefit robotic or autonomous implementations. Leveraging these built-in services and pluggable encryption models of Java makes adding security to an exist bot implementation much easier. But then I thought I should ask an expert on robotics so I fired the question off to Paul Perrone of Perrone Robotics. Paul's build automated vehicles and other forms of embedded devices like auto monitoring of commercial vehicles on highways.He says that most of the works that robots do now are autonomous so it isn't a problem in the short term. But long term projects like collision avoidance technology in automobiles are going to require it.Some of the work he's doing with his Java-based MAX, set of software building blocks containing a wide range of low level and higher level software modules that developers can use to build simple to complex robot and automation applications faster and cheaper, already provide some support for JAUS compliance and because their based on Java, access to standards based security APIs.But, as Paul explained to me, "the bottom line is…it depends on the criticality level of the bot, it's network connectivity, and whether or not a standards compliance is required."

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  • Rope Colliding with a Rectangle

    - by Colton
    I have my rope, and I have my rectangles. The rope is similar to the implementation found here: http://nehe.gamedev.net/tutorial/rope_physics/17006/ Now, I want to make the rope properly collide with the rectangle such that the rope will not pass through a rectangle, and wrap around the rectangle and all that good stuff. Currently, I have it set so no rope node can pass through a rect (successfully), however, this means a rope segment can still pass through a block. Ex: So the question is, what can I do to fix this? What I have tried: I create a rectangle between two nodes of a rope, calculate rotation between the nodes, and get myself a transformed rectangle. I can successfully detect a collision between rope segments and a (non-transformed) rectangle. Create a new node or pivot point around the corner of the block, and rearrange nodes to point to the corner node. Trouble is determining what corner the rope segment is passing through. And then the current rope setup goes wonky (based on verlet integration, so a sudden change in position causes the rope to wiggle like a seismograph during a magnitude 8 earth quake.) Among other issues that might be solvable, but its turning into a case by case thing, which doesn't seem right. I think the best answer here would just be a link to a tutorial (I simply can't find any, most lead to box2D or farseer, but I want to at least learn how it works before I hide behind an engine).

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  • Class Design - Space Simulator

    - by Peteyslatts
    I have pretty much taught myself everything I know about programming, so while I know how to teach myself (books, internet and reading API's), I'm finding that there hasn't been a whole lot in the way of good programming. So I have two questions: First the broad one: Does anyone have suggestions as to sources for learning about good programming habits and techniques? I'd prefer it if the resource wasn't a 5000 page tome. The more I can read it in installments the better. More specifically: I am finishing up learning the basics of XNA and I want to create a space simulator to test my knowledge. This isn't a full scale simulator, but just something that covers everything I learned. It's also going to be modular so I can build on it, after I get the basics down. One of the early features I want to implement is AI. And I want to take this into account as I'm designing my classes so I can minimize rewriting code. So my question: How should I design ship classes so that both the player and AI can use them? The only idea I have so far is: Create a ship class that contains stats, models, textures, collision data etc. The player and AI would then have the data for position, rotation, health, etc and would base their status off of the ship stats.

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  • andEngine dynamic sprites

    - by Blucreation
    Ive just started with andEngine the past week and i only started learning java/android 3 weeks. I can use a for loop to add multiple sprites to the screen but when i try to check collisions on them it only does it to one and not the rest. I want to be able to add a specific number for sprites made from the same texture to the scene, add collision detection to them and also make them slide across the screen (im making a game where you avoid the obstacles). My simple code: private void createobstacle(float pX, float pY) { obstacle = new AnimatedSprite(pX, pY, this.mObjTextureRegion.deepCopy(), getVertexBufferObjectManager()); obstacle.setScale(MathUtils.random(0.5f, 3f)); scene.attachChild(obstacle); } private void createobstacle(int num) { for(int i=0; i<=num; i++ ) { final float xPos = MathUtils.random(30.0f, (CAMERA_WIDTH - 30.0f)); final float yPos = MathUtils.random(30.0f, (CAMERA_HEIGHT - 30.0f)); createobstacle(xPos, yPos); } } Ive read about arrays but i cannot find any tutorials about anything im stuck with. Any help would be great!

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  • How do I apply 2 rotations about different points to a single primitive using OpenGL

    - by Fenoec
    I'm working on a 2D top-down shooter game that has a rotation feature like Realm Of The Mad God such that if you press e the camera rotates around the character in a clockwise direction and q rotates the camera around the character in a counterclockwise direction. I have this working with my floors and walls by translating to the character, doing the screen rotation, and drawing everything with the character as the origin. The problem arises when I shoot projectiles which need to both rotate around the character and rotate around themselves (shooting uses the mouse cursor so I can shoot at any angle). For example, if the screen is not rotated and I'm shooting rectangular projectiles, I want them to face in the direction I'm shooting (rotation around themselves). However if I only do this rotation, when I then rotate the screen the projectiles will always shoot at the same position because my cursor position does not change. Therefore I need to also either rotate the projectiles around the character or rotate the mouse cursor position to get the correct position (which would then totally screw up all of the collision detection). Likewise if I only do the screen rotation on projectiles, the rectangles will always be facing the same way and they would only look correct if I were shooting straight up or straight down. So my question is, how can I perform 2 rotations on a primitive around 2 different points? The only way I can think of is to translate to the character and do the screen rotation, then somehow calculate the translation required to move back to the middle of the projectile (seeing as how my axes are now rotated) and do its rotation. Or am I thinking about this in the wrong way and there is a different solution to accomplishing this effect?

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  • Adjusting the rate of movement of different objects on the same timer

    - by theUg
    I have a series of objects moving along the straight lines. I want to implement slight changes of velocity of each of the object. Constraint is existing model of animation. I am new to this, and not sure if it is the best way to accommodate varying speeds, but what do I know? It is a Java application that repaints the panel every time the timer expires. Timer is set via swing.Timer object that is set by timer delay constant. Every time the game is stepped objects’ coordinates advanced by an increment constant. Most of the objects are of the same class. Is there fairly easy way to refactor existing system to allow changing velocity for an individual object? Is there some obvious common solution I am not aware about? Idea I am having right now is to set timer delay fairly small, and only move objects every so many cycles of animation so that the apparent speed can be adjusted by varying how often they get moved. But that seems fairly involved, and I do not think it is the most elegant solution in terms of performance what with repainting the whole frame every 3-5 milliseconds. Can it be done by advancing the objects so many (varying) times during the certain interval (let’s say 35ms for something like 28fps), and use repaint() method to redraw just individual object? Do I need to mess with pausing animation for smoothness at higher redraw rates? Is it common practise to check for collision at larger step interval, but draw animation a lot more frequently?

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  • Solving &ldquo;XmlSchemaException: The global element '&lt;elementName&gt;' has already been declare

    - by ChrisD
    I recently encountered this error when I attempted to consume a new hosted WCF service.  The service used the Request/Response model and had been properly decorated.  The response and request objects were marked as DataContracts and had a specified namespace.   My WCF service interface was marked as a ServiceContract and shared the namespace attribute value.   Everything should have been fine, right? [ServiceContract(Namespace = "http://schemas.myclient.com/09/12")] public interface IProductActivationService { [OperationContract] ActivateSoftwareResponse ActivateSoftware(ActivateSoftwareRequest request); } well, not exactly.  Apparently the WSDL generator was having an issue: System.Xml.Schema.XmlSchemaException: The global element 'http://schemas.myclient.com/09/12:ActivateSoftwareResponse' has already been declared. After digging I’ve found the problem; the WSDL generator has some reserved suffixes for its entities, including Response, Request, Solicit (see http://msdn.microsoft.com/en-us/library/ms731045.aspx).  The error message is actually the result of a naming conflict.  The WSDL generator uses the namespace of the service to build its reserved types.  The service contract and data contract share a namespace, which coupled with the response/request name suffixes I was using in my class names, resulted in the SchemaException. The Fix: Two options: Rename my data contract entities to use a non-reserved keyword suffix (i.e.  change ActivateSoftwareResponse to ActivateSoftwareResp). or; Change the namespace of the data contracts to differ from the service contract namespace. I chose option 2 and changed all my data contracts to use a “http://schemas.myclient.com/09/12/data” namespace value. This avoided a name collision and I was able to produce my WSDL and consume my service.

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  • How to achieve selection of a tile from a tile sheet based on an ID?

    - by Bugster
    Let's say I have a tile sheet that contains 8 sprites per sheet. Each sprite is a tile of 30x30. I wrote my own custom map parser/map loader however I'm having trouble extracting a certain tile sprite from the file. I'll describe my problem better in order for everyone to understand. I wrote an enum of materials, each material has a value according to it's location relative to the tile sheet. For example void is 1, grass is 2, rock is 3, etc. So in my tile sheet they are represented as such: +---+---+---+---+---+ | 1 | 2 | 3 | 4 | 5 | +---+---+---+---+---+ Which is equivalent to: +------+-------+-------+ | void | grass | stone | +------+-------+-------+ Basically when rendering, I created a tile class, each tile has 2 coordinates: X and Y (They are calculated automatically) and a material which can be represented either as a number, either as a value (ID). When rendering, I have a vector of sprites which are all taken from 1 file called tilesheet.png, however each of them must only draw a certain portion of the tile sheet, for example say I have something like this: tile coordinateBounds(topLeftX, topLeftY, tileWidth, tileHeight); During the initialization of the map I calculate an array of tiles, and I give each of them their position, their materials based on the values in a map file and a few other variables such as collision. I need to apply the coordinateBounds to each of them according to their material value. For example if the material is grass it should only take the grass sprite from the tilesheet. I must also mention I'm using SFML, and there are no borders or spacing between the tiles.

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