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• How can I implement 2D cel shading in XNA?

  - by Artii

  So I was just wondering on how to give a scene I am rendering a hand drawn look (like say Crayon Physics). I don't really want to preprocess the sprites and was thinking of using a shader. Cel shading supplies the effect I want to achieve, but I am only aware of the 3D instances for it. So I wanted to ask if anyone knew a way to get this effect in 2D, or if cel shading would work just as fine on 2D scenes?

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• How is this lighting effect done?

  - by Mike

  This is the most beautiful 2d lighting I have ever seen. Does anyone know how he went about doing it? http://www.youtube.com/watch?v=BIQRhOFkvQY http://www.youtube.com/watch?v=tnTYXPuecMs http://www.youtube.com/watch?v=rhC_jVM8IYU http://www.youtube.com/watch?v=_Aw5BdjWqqU Or download it here: http://grantkot.com/PollutedPlanet/publish.htm edit: I am not asking how the particles are simulated; I don't care about the physics.

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• Current trends in Random Access Memory

  - by Nutel

  As I know for now because of laws of Physics there will be not any tangible improvements in CPU cycles per second for the nearest future. However because of Von Neumann bottleneck it seems to not be an issue for non-server applications. So what about RAM, is there any upcoming technologies that promise to improve memory speed or we are stack with the current situation till quantum computers will come out from labs?

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• Friday Fun: Liquid

  - by Asian Angel

  In this week’s game you will need a mix of patience, timing, and a touch of strategy in order to achieve victory in this physics puzzler. Can you successfully control all of the liquid while moving it towards a victorious finish or will it all ‘go down the drain’? How to Use an Xbox 360 Controller On Your Windows PC Download the Official How-To Geek Trivia App for Windows 8 How to Banish Duplicate Photos with VisiPic

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• Learn Linux, 101: RPM and YUM package management

  <b>IBM Developerworks:</b> "This article focuses on the Red Hat Package Manager (RPM) developed by Red Hat, as well as the Yellowdog Updater Modified (YUM) originally developed to manage Red Hat Linux systems at Duke University's Physics department."

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• Best Frameworks/libraries/engines for 2D multiplayer C# Webbased RPG

  - by Thirlan

  Title is a mouthful but important because I'm looking to meet a specific criteria and it's complex enough that I need a lot of help in finding what I'm looking for. I really want people's suggestions because I trust it a lot more than anything else, so I just need to clearly define what it is I want heh : P Game is a 2D RPG. Think of Secret of Mana. Game is online multiplayer, but not MMO sized. Game must be webbased! I'm looking to the future and want to hit as many platforms as possible. I'm leaning to Webgl because of this, but still looking around. Since the users are seeing the game through the webbrowser the front-end should be mainly responsible for drawing, taking input and some basic checking such as preliminary collision detection. This is important because it means the game engine is NOT on the client's machine. The server should be responsible for the game engine and all the calculations. This means the server is doing all the work and the client is mostly a dumb terminal. Server language is c# I'm looking for fast project execution so I want to use as many pre-existing tools as possible. This would make sense because I'm making a game here, not an engine. I'm not creating some new revolutionary graphics or pushing the physics engines to the next level. Preference for commercially supported tools. For game mechanics reasons and for reasons 4 and 5, don't think I can use existing 2D rpg engines. I've seen them out there and I fear that if I try and use them they will have too many restrictions, but will be happy to hear out suggestions. So all this means I need a game engine on the server, or maybe just a physics engine, and then I need another engine/library to draw everything that the server is sending to the client on the webbrowser. Maybe this is how 50% of games work on the web and there are plenty of frameworks that support this! I wouldn't actually don't know : ( but my gut is telling me that most webgames are single player and 90% of the game is running on the client. So... any suggestions?

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• How to properly do weapon cool-down reload timer in multi-player laggy environment?

  - by John Murdoch

  I want to handle weapon cool-down timers in a fair and predictable way on both client on server. Situation: Multiple clients connected to server, which is doing hit detection / physics Clients have different latency for their connections to server ranging from 50ms to 500ms. They want to shoot weapons with fairly long reload/cool-down times (assume exactly 10 seconds) It is important that they get to shoot these weapons close to the cool-down time, as if some clients manage to shoot sooner than others (either because they are "early" or the others are "late") they gain a significant advantage. I need to show time remaining for reload on player's screen Clients can have clocks which are flat-out wrong (bad timezones, etc.) What I'm currently doing to deal with latency: Client collects server side state in a history, tagged with server timestamps Client assesses his time difference with server time: behindServerTimeNs = (behindServerTimeNs + (System.nanoTime() - receivedState.getServerTimeNs())) / 2 Client renders all state received from server 200 ms behind from his current time, adjusted by what he believes his time difference with server time is (whether due to wrong clocks, or lag). If he has server states on both sides of that calculated time, he (mostly LERP) interpolates between them, if not then he (LERP) extrapolates. No other client-side prediction of movement, e.g., to make his vehicle seem more responsive is done so far, but maybe will be added later So how do I properly add weapon reload timers? My first idea would be for the server to send each player the time when his reload will be done with each world state update, the client then adjusts it for the clock difference and thus can estimate when the reload will be finished in client-time (perhaps considering also for latency that the shoot message from client to server will take as well?), and if the user mashes the "shoot" button after (or perhaps even slightly before?) that time, send the shoot event. The server would get the shoot event and consider the time shot was made as the server time when it was received. It would then discard it if it is nowhere near reload time, execute it immediately if it is past reload time, and hold it for a few physics cycles until reload is done in case if it was received a bit early. It does all seem a bit convoluted, and I'm wondering whether it will work (e.g., whether it won't be the case that players with lower ping get better reload rates), and whether there are more elegant solutions to this problem.

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• Box2D blocky map. Body, Fixtures a huge map and performance

  - by Solom

  Right now I'm still in the planning phase of a my very first game. I'm creating a "Minecraft"-like game in 2D that features blocks that can be destroyed as well as players moving around the map. For creating the map I chose a 2D-Array of Integers that represent the Block ID. For testing purposes I created a huge map (16348 * 256) and in my prototype that didn't use Box2D everything worked like a charm. I only rendered those blocks that where within the bounds of my camera and got 60 fps straight. The problem started when I decided to use an existing physics-solution rather than implementing my own one. What I had was basically simple hitboxes around the blocks and then I had to manually check if the player collided with any of those in his neighborhood. For more advanced physics as well as the collision detection I want to switch over to Box2D. The problem I have right now is ... how to go about the bodies? I mean, the blocks are of a static bodytype. They don't move on their own, they just are there to be collided with. But as far as I can see it, every block needs his own body with a rectangular fixture attached to it, so as to be destroyable. But for a huge map such as mine, this turns out to be a real performance bottle-neck. (In fact even a rather small map [compared to the other] of 1024*256 is unplayable.) I mean I create thousands of thousands of blocks. Even if I just render those that are in my immediate neighborhood there are hundreds of them and (at least with the debugRenderer) I drop to 1 fps really quickly (on my own "monster machine"). I thought about strategies like creating just one body, attaching multiple fixtures and only if a fixture got hit, separate it from the body, create a new one and destroy it, but this didn't turn out quite as successful as hoped. (In fact the core just dumps. Ah hello C! I really missed you :X) Here is the code: public class Box2DGameScreen implements Screen { private World world; private Box2DDebugRenderer debugRenderer; private OrthographicCamera camera; private final float TIMESTEP = 1 / 60f; // 1/60 of a second -> 1 frame per second private final int VELOCITYITERATIONS = 8; private final int POSITIONITERATIONS = 3; private Map map; private BodyDef blockBodyDef; private FixtureDef blockFixtureDef; private BodyDef groundDef; private Body ground; private PolygonShape rectangleShape; @Override public void show() { world = new World(new Vector2(0, -9.81f), true); debugRenderer = new Box2DDebugRenderer(); camera = new OrthographicCamera(); // Pixel:Meter = 16:1 // Body definition BodyDef ballDef = new BodyDef(); ballDef.type = BodyDef.BodyType.DynamicBody; ballDef.position.set(0, 1); // Fixture definition FixtureDef ballFixtureDef = new FixtureDef(); ballFixtureDef.shape = new CircleShape(); ballFixtureDef.shape.setRadius(.5f); // 0,5 meter ballFixtureDef.restitution = 0.75f; // between 0 (not jumping up at all) and 1 (jumping up the same amount as it fell down) ballFixtureDef.density = 2.5f; // kg / m² ballFixtureDef.friction = 0.25f; // between 0 (sliding like ice) and 1 (not sliding) // world.createBody(ballDef).createFixture(ballFixtureDef); groundDef = new BodyDef(); groundDef.type = BodyDef.BodyType.StaticBody; groundDef.position.set(0, 0); ground = world.createBody(groundDef); this.map = new Map(20, 20); rectangleShape = new PolygonShape(); // rectangleShape.setAsBox(1, 1); blockFixtureDef = new FixtureDef(); // blockFixtureDef.shape = rectangleShape; blockFixtureDef.restitution = 0.1f; blockFixtureDef.density = 10f; blockFixtureDef.friction = 0.9f; } @Override public void render(float delta) { Gdx.gl.glClearColor(1, 1, 1, 1); Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT); debugRenderer.render(world, camera.combined); drawMap(); world.step(TIMESTEP, VELOCITYITERATIONS, POSITIONITERATIONS); } private void drawMap() { for(int a = 0; a < map.getHeight(); a++) { /* if(camera.position.y - (camera.viewportHeight/2) > a) continue; if(camera.position.y - (camera.viewportHeight/2) < a) break; */ for(int b = 0; b < map.getWidth(); b++) { /* if(camera.position.x - (camera.viewportWidth/2) > b) continue; if(camera.position.x - (camera.viewportWidth/2) < b) break; */ /* blockBodyDef = new BodyDef(); blockBodyDef.type = BodyDef.BodyType.StaticBody; blockBodyDef.position.set(b, a); world.createBody(blockBodyDef).createFixture(blockFixtureDef); */ PolygonShape rectangleShape = new PolygonShape(); rectangleShape.setAsBox(1, 1, new Vector2(b, a), 0); blockFixtureDef.shape = rectangleShape; ground.createFixture(blockFixtureDef); rectangleShape.dispose(); } } } @Override public void resize(int width, int height) { camera.viewportWidth = width / 16; camera.viewportHeight = height / 16; camera.update(); } @Override public void hide() { dispose(); } @Override public void pause() { } @Override public void resume() { } @Override public void dispose() { world.dispose(); debugRenderer.dispose(); } } As you can see I'm facing multiple problems here. I'm not quite sure how to check for the bounds but also if the map is bigger than 24*24 like 1024*256 Java just crashes -.-. And with 24*24 I get like 9 fps. So I'm doing something really terrible here, it seems and I assume that there most be a (much more performant) way, even with Box2D's awesome physics. Any other ideas? Thanks in advance!

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• How to set density for each shape in PhysX 3.1

  - by hywei

  I'm using PhysX 3.1 as my game's physics engine. One requirement is that I need set different density for each shape(there are server shapes for my single rigid actor). I know that the shape's density can be set by NxShapeDesc::density in PhysX 2.8, but I can't find such interface in PhysX 3.1. I know that the mass properties can be set in PhysX 3.1 just as the snowman example in the SDK, but I don't know whether there exists a direct interface to set density for each shape.

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• Different bounding volumes for culling and collision detection

  - by Serthy

  Should an object in a 3D-engine use different bounding volumes for collision-detection (broad-phase) and culling? Basically class renderBounds and class physBounds versus class boundingVolume? Each of this classes then could either contain the same type of volumes (AABB's, kDOP's, sphere's etc.) or a special fitting one for the particular object. (note: without considering of using an external physics engine)

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• How to type all the math, stat, greek, equations EFFICIENTLY in libreoffice?

  - by kernel_panic

  i am preparing a report related to physics which is full of greek, stat and calculus things, i know there is this question how to insert a greek symbol, but my problem is i cant fiddle with a drop down/ scroll list for for every symbol(my paper in FULL of those), is there a way to do something with my keyboard layout, and turn it into something like the one Tony Stark uses in Ironman(i am not kidding please). i am literally tired for this fiddle-work for half of the day and have completed just 2 sheets, hmmm.

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• How to add energy ball which disappears when touched by player in UDK?

  - by OliveOne

  I am new to UDK and learning game development. I want to know about how to add a ball to the game world with the following effects/actions: Glowing effect Physics-like object (just having gravity) Particles when touched by player-avatar Disappears in 1-2 seconds after touch Score updates based on different colors of ball I know little about this can be done by kismet, cascade and content creation, but do not know where to start. Please tell me the steps for this. I am trying this weekend in depth.

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• Help decide HTML5 library or framework

  - by aoi

  I need a library or framework for small html5 contents and animation centric softwares. My priority isn't things like physics or network. I need fast rendering speed, support for touch event and most of all maximum compatibility across various platforms, including ios and android. I am pondering upon sprite js, crafty js, and kinetic js. But i can't really test the platform compatibilities, so can someone please tell me which one covers the maximum number of platforms, and if there are any better free alternatives?

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• Resources for Game Development in iPhone for beginners [closed]

  - by Volatil3

  Possible Duplicate: What are the best iPhone game development resources? Hi I'm a programmer but I have never worked on Game programming so have no idea about OpenGL and all that. I am more interested to get into physics based games like Angry Birds and want to implement fewer ideas. Can you recommend me some good books which not only teach the concept of game programming but also practical implementation in iPhone platform? Thanks in advance

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• Best system for creating a 2d racing track

  - by tesselode

  I am working a 2D racing game and I'm trying to figure out what is the best way to define the track. At the very least, I need to be able to create a closed circuit with any amount of turns at any angle, and I need vehicles to collide with the edges of the track. I also want the following things to be true if possible (but they are optional): The code is simple and free of funky workarounds and extras I can define all of the parts of the track (such as turns) relative to the previous parts I can predict the exact position of the road at a certain point (that way I can easily and cleanly make closed circuits) Here are my options: Use a set of points. This is my current system. I have a set of turns and width changes that the track is supposed to make over time. I have a point which I transform according to these instructions, and I place a point every 5 steps or so, depending on how precise I want the track to be. These points make up the track. The main problem with this is the discrepancy between the collisions and the way the track is drawn. I won't get into too much detail, but the picture below shows what is happening (although it is exaggerated a bit). The blue lines are what is drawn, the red lines are what the vehicle collides with. I could work around this, but I'd rather avoid funky workaround code. Beizer curves. These seem cool, but my first impression of them is that they'll be a little daunting to learn and are probably too complicated for my needs. Some other kind of curve? I have heard of some other kinds of curves; maybe those are more applicable. Use Box2D or another physics engine. Instead of defining the center of the track, I could use a physics engine to define shapes that make up the road. The downside to this, however, is that I have to put in a little more work to place the checkpoints. Something completely different. Basically, what is the simplest system for generating a race track that would allow me to create closed circuits cleanly, handle collisions, and not have a ton of weird code?

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• Andengine. Put bullet to pool, when it leaves screen

  - by Ashot

  i'm creating a bullet with physics body. Bullet class (extends Sprite class) has die() method, which unregister physics connector, hide sprite and put it in pool public void die() { Log.d("bulletDie", "See you in hell!"); if (this.isVisible()) { this.setVisible(false); mPhysicsWorld.unregisterPhysicsConnector(physicsConnector); physicsConnector.setUpdatePosition(false); body.setActive(false); this.setIgnoreUpdate(true); bulletsPool.recyclePoolItem(this); } } in onUpdate method of PhysicsConnector i executes die method, when sprite leaves screen physicsConnector = new PhysicsConnector(this,body,true,false) { @Override public void onUpdate(final float pSecondsElapsed) { super.onUpdate(pSecondsElapsed); if (!camera.isRectangularShapeVisible(_bullet)) { Log.d("bulletDie","Dead?"); _bullet.die(); } } }; it works as i expected, but _bullet.die() executes TWICE. what i`m doing wrong and is it right way to hide sprites? here is full code of Bullet class (it is inner class of class that represents player) private class Bullet extends Sprite implements PhysicsConstants { private final Body body; private final PhysicsConnector physicsConnector; private final Bullet _bullet; private int id; public Bullet(float x, float y, ITextureRegion texture, VertexBufferObjectManager vertexBufferObjectManager) { super(x,y,texture,vertexBufferObjectManager); _bullet = this; id = bulletId++; body = PhysicsFactory.createCircleBody(mPhysicsWorld, this, BodyDef.BodyType.DynamicBody, bulletFixture); physicsConnector = new PhysicsConnector(this,body,true,false) { @Override public void onUpdate(final float pSecondsElapsed) { super.onUpdate(pSecondsElapsed); if (!camera.isRectangularShapeVisible(_bullet)) { Log.d("bulletDie","Dead?"); Log.d("bulletDie",id+""); _bullet.die(); } } }; mPhysicsWorld.registerPhysicsConnector(physicsConnector); $this.getParent().attachChild(this); } public void reset() { final float angle = canon.getRotation(); final float x = (float) ((Math.cos(MathUtils.degToRad(angle))*radius) + centerX) / PIXEL_TO_METER_RATIO_DEFAULT; final float y = (float) ((Math.sin(MathUtils.degToRad(angle))*radius) + centerY) / PIXEL_TO_METER_RATIO_DEFAULT; this.setVisible(true); this.setIgnoreUpdate(false); body.setActive(true); mPhysicsWorld.registerPhysicsConnector(physicsConnector); body.setTransform(new Vector2(x,y),0); } public Body getBody() { return body; } public void setLinearVelocity(Vector2 velocity) { body.setLinearVelocity(velocity); } public void die() { Log.d("bulletDie", "See you in hell!"); if (this.isVisible()) { this.setVisible(false); mPhysicsWorld.unregisterPhysicsConnector(physicsConnector); physicsConnector.setUpdatePosition(false); body.setActive(false); this.setIgnoreUpdate(true); bulletsPool.recyclePoolItem(this); } } }

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• How to decompose a rectangular shape in a Voronoi diagram, only generating convex shapes?

  - by DevilWithin

  I think this is a very straighforward question, lets say i have a building in 2D, a rectangle shape. Now i want to decompose that area in a lot of convex shapes, as seen in a voronoi diagram, or closely like it, just so I can add those shapes to the physics engine, and have a realistic destruction. Bonus: Possible suggestions on how to make the effect more dynamic and interesting. Please keep in mind we re talking about realtime calculations..

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• Your Dental Web Site Development and the Clients You'll Get

  Dental web site development isn't nuclear physics. At least, it shouldn't be. The key factors that you have to consider are clear enough to know.

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• IIS Logfile Visualization with XNA

  - by BobPalmer

  In my office, I have a wall mounted monitor who's whole purpose in life is to display perfmon stats from our various servers.  And on a fairly regular basis, I have folks walk by asking what the lines mean.    After providing the requisite explaination about CPU utilization, disk I/O bottlenecks, etc. this is usually followed by some blank stares from the user in question, and a distillation of all of our engineering wizardry down to the phrase 'So when the red line goes up that's bad then?'   This of course would not do.  So I talked to my friends and our network admin about an option to show something more eye catching and visual, with which we could catch at a glance a feel for what was up with our site.    He initially pointed me out to a video showing GLTail and Chipmunk done in Ruby.  Realizing this was both awesome, and that I needed an excuse to do something in XNA, I decided to knock out a proof of concept for something very similar, but with a few tweaks.   Here's a link to a video of the current prototype:   http://www.youtube.com/watch?v=jM_PWZbtH2I   Essentially this app opens up a log file (even an active one) and begins pulling out the lines of text.  (Here's a good Code Project link that covers how to do tail reading from an active text file: http://www.codeproject.com/KB/files/tail.aspx).   As new data is added, a bubble is generated in the application - a GET statement comes from the left, and a POST from the right.  I then run it through a series of expression checkers, and based on the kind of statement and the pattern, a bubble of an appropriate color is generated.   For example, if I get a 500, a huge red bubble pops out.  Others are based on the part of the system the page is from - i.e. green bubbles are from our claims management subsystem, and blue bubbles are from the pages our scheduling staff use to schedule patients.  Others include the purple bubbles for security and login, and yellow bubbles for some miscellaneous pages.   The little grey bubbles represent things like images, JS, CSS, etc - and their small size makes them work like grease to keep the larger page bubbles moving.   The app is also smart enough that if it is starting to bog down with handling the physics and interactions, it will suspend new bubbles until enough have dropped off that performance can resume (you can see this slight stuttering in the sample video).   The net result is that anyone will be able to look up on the wall monitor, and instantly get a quick feel for how things are going on the floor.  Website slow?  You can get a feel for both volume and utilized modules with one glance.  Website crashing?  Look for a wall of giant red bubbles.  No activity at all?  Maybe the site is down.  Now couple this with utilization within a farm, and cross referenced with a second app showing the same kind of data from your SQL database...   As for the app itself, it's a windows XNA project with the code in C#.   The physics are handled by the Farseer physicis eingine for XNA (http://www.codeplex.com/FarseerPhysics) which is just pure goodness.  The samples are great, and I had the app up and working in two evenings (half of that was fine tuning, and the other was me coding with a kid in my lap).   My next steps include wiring this to SQL (I have some ideas...), and adding a nice configuration module.  For example, you could use polygons, etc to tie to your regex - or more entertaining things like having a little human ragdoll to represent a user login.     Once that's wrapped up and I have a chance to complete some hardening, I will be releasing the whole thing into the wild as opensource.     Feel free to ping me if you have any questions! -Bob

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• XNA - 3D AABB collision detection and response

  - by fastinvsqrt

  I've been fiddling around with 3D AABB collision in my voxel engine for the last couple of days, and every method I've come up with thus far has been almost correct, but each one never quite worked exactly the way I hoped it would. Currently what I do is get two bounding boxes for my entity, one modified by the X translation component and the other by the Z component, and check if each collides with any of the surrounding chunks (chunks have their own octrees that are populated only with blocks that support collision). If there is a collision, then I cast out rays into that chunk to get the shortest collision distance, and set the translation component to that distance if the component is greater than the distance. The problem is that sometimes collisions aren't even registered. Here's a video on YouTube that I created showing what I mean. I suspect the problem may be with the rays that I cast to get the collision distance not being where I think they are, but I'm not entirely sure what would be wrong with them if they are indeed the problem. Here is my code for collision detection and response in the X direction (the Z direction is basically the same): // create the XZ offset vector Vector3 offsXZ = new Vector3( ( _translation.X > 0.0f ) ? SizeX / 2.0f : ( _translation.X < 0.0f ) ? -SizeX / 2.0f : 0.0f, 0.0f, ( _translation.Z > 0.0f ) ? SizeZ / 2.0f : ( _translation.Z < 0.0f ) ? -SizeZ / 2.0f : 0.0f ); // X physics BoundingBox boxx = GetBounds( _translation.X, 0.0f, 0.0f ); if ( _translation.X > 0.0f ) { foreach ( Chunk chunk in surrounding ) { if ( chunk.Collides( boxx ) ) { float dist = GetShortestCollisionDistance( chunk, Vector3.Right, offsXZ ) - 0.0001f; if ( dist < _translation.X ) { _translation.X = dist; } } } } else if ( _translation.X < 0.0f ) { foreach ( Chunk chunk in surrounding ) { if ( chunk.Collides( boxx ) ) { float dist = GetShortestCollisionDistance( chunk, Vector3.Left, offsXZ ) - 0.0001f; if ( dist < -_translation.X ) { _translation.X = -dist; } } } } And here is my implementation for GetShortestCollisionDistance: private float GetShortestCollisionDistance( Chunk chunk, Vector3 rayDir, Vector3 offs ) { int startY = (int)( -SizeY / 2.0f ); int endY = (int)( SizeY / 2.0f ); int incY = (int)Cube.Size; float dist = Chunk.Size; for ( int y = startY; y <= endY; y += incY ) { // Position is the center of the entity's bounding box Ray ray = new Ray( new Vector3( Position.X + offs.X, Position.Y + offs.Y + y, Position.Z + offs.Z ), rayDir ); // Chunk.GetIntersections(Ray) returns Dictionary<Block, float?> foreach ( var pair in chunk.GetIntersections( ray ) ) { if ( pair.Value.HasValue && pair.Value.Value < dist ) { dist = pair.Value.Value; } } } return dist; } I realize some of this code can be consolidated to help with speed, but my main concern right now is to get this bit of physics programming to actually work.

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• I need help with 2D collision response (of stacking rotating polygons, with friction and gravity, for a game)

  - by Register Sole

  Hi I am looking for suggestions on how to write a collision response for game programming purpose (so not a scientific simulation). I am dealing with 2D polygons that are rotating, and I want them to be able to stack. I also want friction and gravity. I have a detection mechanism that returns the separating axis, how long the polygons are overlapping, and up to 2 points of contact. For the response, I am currently using an impulse-based response, which main idea is: find the separating axis, length of overlap, and the point of contact (if there are two, pick a random point between to simulate averaged force. i believe there are better ways than this) separate the object (modifying their positions, taking into account of their masses. i do not separate them completely though, to keep track that they are colliding to reduce jitter) calculate normal force based on the coefficient of restitution as if there is no friction. calculate friction, as if there is no normal force. I also assume that the direction of the friction is the same throughout the collision. apply the two forces (which result in a rather inaccurate result, since each force is calculated as if the other is not present. for non-rotating bodies though, this method is exact) I am aware that this method requires the coefficient of friction to be sufficiently small due to the assumption that the direction of friction stays the same in a collision. Also, the result is visually satisfying if gravity is not present. However, when there is gravity, objects on ground jitter and drift (even with zero coefficient of restitution)! It also happens for stacking objects. Larger coefficient of restitution and gravity increase the jittering. I hope you can help me with this. Some things i would like to know more about is how to handle collision with two point of contacts (how to end up having an object sitting still on the ground?), how to reduce, and prevent if possible, jitter and drift (do people use the most accurate method possible, or is there a trick to overcome this?), and how to handle multiple objects collision (for example, in the case of stacking objects, how do I check collisions between all of them and keep them all stable at every frame so they don't jitter?). A total reformulation of my algorithm is also welcomed, as long as it works. Another thing to note is that I am not making a Physics game, so I only need a visually satisfying response (though a realistic response is preferable, if it is not performance-heavy). But surely jittering and drifting objects on flat ground are not at all acceptable. In addition, I am a Physics student, so feel free to talk about impulse and whatever needed. Finally, I'm sorry for the long post. I tried to be as concise as I can. Thank you for reading it! EDIT It seems what I didn't manage to come up all this time is to separate resting contact as a class of its own and how to solve them. Currently reading the paper suggested by Jedediah. More suggestions on the topic are welcome :) CASE CLOSED After reading various papers referenced in the paper, successfully implemented simultaneous impulse method (referring to the original paper by Erin Catto, [Catt05]). Thanks maaaan!! The paper is wonderful. The current system is visibly much better than the previous. Still haven't separated resting contact as a class of its own though, which brings me to my next question. Love you all! Haha (sorry, I'm just so happy thanks to you).

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• How do you make a static sprite be a child of another sprite in cocos2D while using SpaceManager

  - by JJBigThoughts

  I have two static (STATIC_MASS) SpaceManager sprites. One is a child of the other - by which I mean that one sort of builds up the other one, but although the child's images shows up in the right place, the child doesn't seem to exists in the chipmunk physics engine, like I would expect. In my case, I have a backboard (rectangular sprite) and a hoop (a circular sprite). Since I might want to move the backboard, I'd like to attach the hoop to backboard so that the hoop automatically moves right along with the backboard. Here, we see a rotating backboard with attached hoop. It looks OK on the screen, but other objects only bounce off the backboard but pass right through the hoop (in a bad sense of the term). What doesn't my child sprite seem to exist in the physics engine? // Add Backboard cpShape *shapeRect = [smgr addRectAt:cpvWinCenter mass:STATIC_MASS width:200 height:10 rotation:0.0f ];// We're upgrading this cpCCSprite * cccrsRect = [cpCCSprite spriteWithShape:shapeRect file:@"rect_200x10.png"]; [self addChild:cccrsRect]; // Spin the static backboard: http://stackoverflow.com/questions/2691589/how-do-you-make-a-sprite-rotate-in-cocos2d-while-using-spacemanager // Make static object update moves in chipmunk // Since Backboard is static, and since we're going to move it, it needs to know about spacemanager so its position gets updated inside chipmunk. // Setting this would make the smgr recalculate all static shapes positions every step // cccrsRect.integrationDt = smgr.constantDt; // cccrsRect.spaceManager = smgr; // Alternative method: smgr.rehashStaticEveryStep = YES; smgr.rehashStaticEveryStep = YES; // Spin the backboard [cccrsRect runAction:[CCRepeatForever actionWithAction: [CCSequence actions: [CCRotateTo actionWithDuration:2 angle:180], [CCRotateTo actionWithDuration:2 angle:360], nil] ]]; // Add the hoop cpShape *shapeHoop = [smgr addCircleAt:ccp(100,-45) mass:STATIC_MASS radius: 50 ]; cpCCSprite * cccrsHoop = [cpCCSprite spriteWithShape:shapeHoop file:@"hoop_100x100.png"]; [cccrsRect addChild:cccrsHoop]; This is only half working for me. Note: SpaceManager is a toolkit for working with cocos2D-iphone

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• How to split up levels? (cocos2d,box2d,iphone) to save CPU and memory?

  - by cocos2dbeginner

  Hi, so I'm going to create large levels. But there's a problem: There's much unseen space (it's a jump'n run like mario bros.) and this will use memory + cpu. so how could I split up my levels? I'm using Box2D+ cocos2d for iphone. Any ideas? Mayby just set the visible property to NO? But it would be still in the memory :(. But what with the box2d bodies? Destroy and recreate them would be to heavy for the FPS, because I have physics built in which should not be recreated. Should I make fix points where i want to split the level up, than if the player is 200 px away it should preload it. and if the player is 200 px away from the last part of the level I unload it. But there would be the problem with the physics, because on the start of the level it has a unique movement and later if i destroy and recreate it it would do the same. but i don't want that. other ideas?

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• Weird stuttering issues not related to GC.

  - by Smills

  I am getting some odd stuttering issues with my game even though my FPS never seems to drop below 30. About every 5 seconds my game stutters. I was originally getting stuttering every 1-2 seconds due to my garbage collection issues, but I have sorted those and will often go 15-20 seconds without a garbage collection. Despite this, my game still stutters periodically even when there is no GC listed in logcat anywhere near the stutter. Even when I take out most of my code and simply make my "physics" code the below code I get this weird slowdown issue. I feel that I am missing something or overlooking something. Shouldn't that "elapsed" code that I put in stop any variance in the speed of the main character related to changes in FPS? Any input/theories would be awesome. Physics: private void updatePhysics() { //get current time long now = System.currentTimeMillis(); //added this to see if I could speed it up, it made no difference Thread myThread = Thread.currentThread(); myThread.setPriority(Thread.MAX_PRIORITY); //work out elapsed time since last frame in seconds double elapsed = (now - mLastTime2) / 1000.0; mLastTime2 = now; //measures FPS and displays in logcat once every 30 frames fps+=1/elapsed; fpscount+=1; if (fpscount==30) { fps=fps/fpscount; Log.i("myActivity","FPS: "+fps+" Touch: "+touch); fpscount=0; } //this should make the main character (theoretically) move upwards at a steady pace mY-=100*elapsed; //increase amount I translate the draw to = main characters Y //location if the main character goes upwards if (mY<=viewY) { viewY=mY; } }

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• How much is too much memory allocation in NDK?

  - by Maximus

  The NDK download page notes that, "Typical good candidates for the NDK are self-contained, CPU-intensive operations that don't allocate much memory, such as signal processing, physics simulation, and so on." I came from a C background and was excited to try to use the NDK to operate most of my OpenGL ES functions and any native functions related to physics, animation of vertices, etc... I'm finding that I'm relying quite a bit on Native code and wondering if I may be making some mistakes. I've had no trouble with testing at this point, but I'm curious if I may run into problems in the future. For example, I have game struct defined (somewhat like is seen in the San-Angeles example). I'm loading vertex information for objects dynamically (just what is needed for an active game area) so there's quite a bit of memory allocation happening for vertices, normals, texture coordinates, indices and texture graphic data... just to name the essentials. I'm quite careful about freeing what is allocated between game areas. Would I be safer setting some caps on array sizes or should I charge bravely forward as I'm going now?

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