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• OpenGL 2D Rasterization Sub-Pixel Translations

  - by Armin Ronacher

  I have a tile based 2D engine where the projection matrix is an orthographic view of the world without any scaling applied. Thus: one pixel texture is drawn on the screen in the same size. That all works well and looks nice but if the camera makes a sub-pixel movement small lines appear between the tiles. I can tell you in advance what does not fix the problem: GL_NEAREST texture interpolation GL_CLAMP_TO_EDGE What does “fix” the problem is anchoring the camera to the nearest pixel instead of doing a sub-pixel translation. I can live with that, but the camera movement becomes jerky. Any ideas how to fix that problem without resorting to the rounding trick I do currently?

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• Implementing Circle Physics in Java

  - by Shijima

  I am working on a simple physics based game where 2 balls bounce off each other. I am following a tutorial, 2-Dimensional Elastic Collisions Without Trigonometry, for the collision reactions. I am using Vector2 from the LIBGDX library to handle vectors. I am a bit confused on how to implement step 6 in Java from the tutorial. Below is my current code, please note that the code strictly follows the tutorial and there are redundant pieces of code which I plan to refactor later. Note: refrences to this refer to ball 1, and ball refers to ball 2. /* * Step 1 * * Find the Normal, Unit Normal and Unit Tangential vectors */ Vector2 n = new Vector2(this.position[0] - ball.position[0], this.position[1] - ball.position[1]); Vector2 un = n.normalize(); Vector2 ut = new Vector2(-un.y, un.x); /* * Step 2 * * Create the initial (before collision) velocity vectors */ Vector2 v1 = this.velocity; Vector2 v2 = ball.velocity; /* * Step 3 * * Resolve the velocity vectors into normal and tangential components */ float v1n = un.dot(v1); float v1t = ut.dot(v1); float v2n = un.dot(v2); float v2t = ut.dot(v2); /* * Step 4 * * Find the new tangential Velocities after collision */ float v1tPrime = v1t; float v2tPrime = v2t; /* * Step 5 * * Find the new normal velocities */ float v1nPrime = v1n * (this.mass - ball.mass) + (2 * ball.mass * v2n) / (this.mass + ball.mass); float v2nPrime = v2n * (ball.mass - this.mass) + (2 * this.mass * v1n) / (this.mass + ball.mass); /* * Step 6 * * Convert the scalar normal and tangential velocities into vectors??? */

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• determine collision angle on a rotating body

  - by jorb

  update: new diagram and updated description I have a contact listener set up to try and determine the side that a collision happened at relative to the a bodies rotation. One way to solve this is to find the value of the yellow angle between the red and blue vectors drawn above. The angle can be found by taking the arc cosine of the dot product of the two vectors (Evan pointed this out). One of my points of confusion is the difference in domain of the atan2 function html canvas coordinates and the Box2d rotation information. I know I have to account for this somehow... SS below questions: Does Box2D provide these angles more directly in the collision information? Am I even on the right track? If so, any hints? I have the following javascript so far: Ship.prototype.onCollide = function (other_ent,cx,cy) { var pos = this.body.GetPosition(); //collision position relative to body var d_cx = pos.x - cx; var d_cy = pos.y - cy; //length of initial vector var len = Math.sqrt(Math.pow(pos.x -cx,2) + Math.pow(pos.y-cy,2)); //body angle - can over rotate hence mod 2*Pi var ang = this.body.GetAngle() % (Math.PI * 2); //vector representing body's angle - same magnitude as the first var b_vx = len * Math.cos(ang); var b_vy = len * Math.sin(ang); //dot product of the two vectors var dot_prod = d_cx * b_vx + d_cy * b_vy; //new calculation of difference in angle - NOT WORKING! var d_ang = Math.acos(dot_prod); var side; if (Math.abs(d_ang) < Math.PI/2 ) side = "front"; else side = "back"; console.log("length",len); console.log("pos:",pos.x,pos.y); console.log("offs:",d_cx,d_cy); console.log("body vec",b_vx,b_vy); console.log("body angle:",ang); console.log("dot product",dot_prod); console.log("result:",d_ang); console.log("side",side); console.log("------------------------"); }

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• OpenGL ES, orthopgraphics projection and viewport

  - by DarkDeny

  I want to make some simple 2D game on iOS to familiarize myself with OpenGL ES. I started with Ray Wenderlich tutorial (How To Create A Simple 2D iPhone Game with OpenGL ES 2.0 and GLKit). That tutorial is quite good, but I miss some parts of a puzzle. Ray creates orthographic projection using some magic numbers like 480 and 320. It is not clear to me why did he take these numbers, and as far as I can see - sprite is not mapped to the ipad simulator screen one-to-one pixel. I tried to play with parameters with which ortho matrix is created, but I cannot figure out what math is here. How can I calculate numbers (bottom, top, left, right, close, far) which will be parameters to orthographic projection matrix creation and have sprite on the screen shown in its original size?

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• Simple 3D Physics engine as a part of graduation project [on hold]

  - by Eugene Kolesnikov

  I am working on my graduation project and one part of it is to simulate the motion of a rigid body in 3D space. I can use either already written physics engine or to write it myself. It's quite an interesting challenge for me, so I would like to do it myself. I am able to use either C++ or Java for programming (prefer C++). I am using Mac OS X and Debian 7. Could you suggest any guides or tutorials how to do it, can't find it anywhere... More precisely, I need a very simple engine, without collision detection, and many other things that I do not know, I just need to calculate the forces and move my body, depending on the resultant force. If you think that this task is still very difficult or there is no such tutorial, please suggest me some good and simple engine.

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• Does SFML render graphics outside the window?

  - by ThePlan

  While working on a tile-based map I figured it would be a good idea if I would only render what the player sees on the game window, but then it occurred to me that SFML could already be optimized enough to know when it doesn't have to render those things. Let's say I draw a 30x30 squared maps (A medium one) but the player only sees a bunch of them, not entirely. Would SFML automatically hide what the player doesn't see, or should I hide it myself?

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• How to remove a box2d body when collision happens?

  - by Ayham

  I’m still new to java and android programming and I am having so much trouble Removing an object when collision happens. I looked around the web and found that I should never handle removing BOX2D bodies during collision detection (a contact listener) and I should add my objects to an arraylist and set a variable in the User Data section of the body to delete or not and handle the removing action in an update handler. So I did this: First I define two ArrayLists one for the faces and one for the bodies: ArrayList<Sprite> myFaces = new ArrayList<Sprite>(); ArrayList<Body> myBodies = new ArrayList<Body>(); Then when I create a face and connect that face to its body I add them to their ArrayLists like this: face = new AnimatedSprite(pX, pY, pWidth, pHeight, this.mBoxFaceTextureRegion); Body BoxBody = PhysicsFactory.createBoxBody(mPhysicsWorld, face, BodyType.DynamicBody, objectFixtureDef); mPhysicsWorld.registerPhysicsConnector(new PhysicsConnector(face, BoxBody, true, true)); myFaces.add(face); myBodies.add(BoxBody); now I add a contact listener and an update handler in the onloadscene like this: this.mPhysicsWorld.setContactListener(new ContactListener() { private AnimatedSprite face2; @Override public void beginContact(final Contact pContact) { } @Override public void endContact(final Contact pContact) { } @Override public void preSolve(Contact contact,Manifold oldManifold) { } @Override public void postSolve(Contact contact,ContactImpulse impulse) { } }); scene.registerUpdateHandler(new IUpdateHandler() { @Override public void reset() { } @Override public void onUpdate(final float pSecondsElapsed) { } }); My plan is to detect which two bodies collided in the contact listener by checking a variable from the user data section of the body, get their numbers in the array list and finally use the update handler to remove these bodies. The questions are: Am I using the arraylist correctly? How to add a variable to the User Data (the code please). I tried removing a body in this update handler but it still throws me NullPointerException , so what is the right way to add an update handler and where should I add it. Any other advices to do this would be great. Thanks in advance.

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• Where can I find "magic numbers" for classic game play mechanics?

  - by MrDatabase

  I'd like to find some "magic numbers" for the classic helicopter game. For example the numbers that determine how fast the helicopter accelerates up and down. Also perhaps the "randomness" of the obstacles (uniformly distributed? Gaussian?). Where can I find these numbers? p.s. I don't care about the particular platform... Flash on the desktop browser is just as good as some implementation on a mobile device.

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• Getting isometric grid coordinates from standard X,Y coordinates

  - by RoryHarvey

  I'm currently trying to add sprites to an isometric Tiled TMX map using Objects in cocos2d. The problem is the X and Y metadata from TMX object are in standard 2d format (pixels x, pixels y), instead of isometric grid X and Y format. Usually you would just divide them by the tile size, but isometric needs some sort of transform. For example on a 64x32 isometric tilemap of size 40 tiles by 40 tiles an object at (20,21)'s coordinates come out as (640,584) So the question really is what formula gets (20,21) from (640,584)?

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• Which game logic should run when doing prediction for PNP state updates

  - by spaceOwl

  We are writing a multiplayer game, where each game client (player) is responsible for sending state updates regarding its "owned" objects to other players. Each message that arrives to other (remote) clients is processed as such: Figure out when the message was sent. Create a diff between NOW and that time. Run game specific logic to bring the received state to "current" time. I am wondering which sort of logic should execute as part of step #3 ? Our game is composed of a physical update (position, speed, acceleration, etc) and many other components that can update an object's state and occur regularly (locally). There's a trade off here - Getting the new state quickly or remaining "faithful" to the true state representation and executing the whole thing to predict the "true" state when receiving state updates from remote clients. Which one is recommended to be used? and why?

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• cocos2d event handler not fired when reentering scene

  - by Adam Freund

  I am encountering a very strange problem with my cocos2d app. I add a sprite to the page and have an event handler linked to it which replaces the scene with another scene. On that page I have another button to take me back to the original scene. When I am back on the original scene, the eventHandler doesn't get fired when I click on the sprite. Below is the relevant code. Thanks for any help! CCMenuItemImage *backBtnImg = [CCMenuItemImage itemWithNormalImage:@"btn_back.png" selectedImage:@"btn_back_pressed.png" target:self selector:@selector(backButtonTapped:)]; backBtnImg.position = ccp(45, 286); CCMenu *backBtn = [CCMenu menuWithItems:backBtnImg, nil]; backBtn.position = CGPointZero; [self addChild:backBtn]; EventHandler method (doesn't get called when the scene is re-entered). (void)backButtonTapped:(id)sender { NSLog(@"backButtonTapped\n"); CCMenuItemImage *backButton = (CCMenuItemImage *)sender; [backButton setNormalImage:[CCSprite spriteWithFile:@"btn_back_pressed.png"]]; [[CCDirector sharedDirector] replaceScene:[CCTransitionFade transitionWithDuration:.25 scene:[MenuView scene] withColor:ccBLACK]]; }

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• Path tables or real time searching for AI?

  - by SirYakalot

  What is the more common practice in commercial games; path lookup tables or real time searches? I've read that in many games path lookup tables are pre-calculated and baked into each map, so to speak, then steering behaviour is used to handle dynamic obstacles. or is it better practice to use optimised hierarchical A* searches? I understand the pro's and cons of each, I'm just curious as to what is most often used in the industry.

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• Applying prerecorded animations to models with the same skeleton

  - by Jeremias Pflaumbaum

  well my question sounds a bit like, how do I apply mo-cap animations to my model, but thats not really it I guess. Animations and model share the same skeleton, but the models vary in size and proportion, but I still want to be able to apply any animation to any model. I think this should be possible since the models got the same skeleton bone structure and the bones are always in the same area only their position varies from model to model. In particular Im trying to apply this to 2D characters that got 2arm, 2legs, a head and a body, but if you got anything related to that topic even if its 3D related or keywords, articles, books whatever Im gratefull for everything cause Im a bit stuck at the moment. cheers Jery

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• how can i get rotation vector from matrix4x4 in xna?

  - by mr.Smyle

  i want to get rotation vector from matrix to realize some parent-children system for models. Matrix bonePos = link.Bone.Transform * World; Matrix m = Matrix.CreateTranslation(link.Offset) * Matrix.CreateScale(link.gameObj.Scale.X, link.gameObj.Scale.Y, link.gameObj.Scale.Z) * Matrix.CreateFromYawPitchRoll(MathHelper.ToRadians(link.gameObj.Rotation.Y), MathHelper.ToRadians(link.gameObj.Rotation.X), MathHelper.ToRadians(link.gameObj.Rotation.Z)) //need rotation vector from bone matrix here (now it's global model rotation vector) * Matrix.CreateFromYawPitchRoll(MathHelper.ToRadians(Rotation.Y), MathHelper.ToRadians(Rotation.X), MathHelper.ToRadians(Rotation.Z)) * Matrix.CreateTranslation(bonePos.Translation); link.gameObj.World = m; where : link - struct with children model settings, like position, rotation etc. And link.Bone - Parent Bone

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• Slick 2d scrolling off screen

  - by Peter

  I have something scrolling in and out of the screen. Now when it goes off screen, I want it to scroll into the screen at another location. What I do is I grab the last pixels at the screens edge using g.copyArea and then g.drawImage on the edge of the screen. And then I do a g.translate to create room for the next row which is next render cycle. My problem is that I get a single pixel row, which is not copied onto the canvas. Where as I want each row to be added and then translated, so that the image that scrolled off screen is recreated on the other side of the screen. Here is my code, maybe there is a better way of doing this, open to any suggests, cause I'm totally stuck @Override public void render(GameContainer gc, Graphics g) throws SlickException { //g.setClip(0, 0, 300, gc.getHeight()); g.translate(0, y); g.drawImage(image,0,200); g.resetTransform(); //g.clearClip(); g.copyArea(rightImage, 0, gc.getHeight() - 1); g.drawImage(rightImage, 300, 0); g.translate(0, y); y=y+3; }

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• Using SVN post-commit hook to update only files that have been commited

  - by fondie

  I am using an SVN repository for my web development work. I have a development site set up which holds a checkout of the repository. I have set up an SVN post-commit hook so that whenever a commit is made to the repository the development site is updated: cd /home/www/dev_ssl /usr/bin/svn up This works fine but due to the size of the repository the updates take a long time (approx. 3 minutes) which is rather frustrating when making regular commits. What I'd like is to change the post-commit hook to only update those files/directories that have been committed but I don't know how to go about doing this. Updating the "lowest common directory" would probably be the best solution, e.g. If committing the follow files: /branches/feature_x/images/logo.jpg /branches/feature_x/css/screen.css It would update the directory: /branches/feature_x/ Can anyone help me create a solution that achieves this please? Thanks! Update: The repository and development site are located on the same server so network issues shouldn't be involved. CPU usage is very low, and I/O should be ok (it's running on hi-spec dedicated server) The development site is approx. 7.5GB in size and contains approx. 600,000 items, this is mainly due to having multiple branches/tags

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• Suggestions to start a cross-platform project

  - by Gabriele

  I have a big project in my head, it should be cross-platform (Win, Max and Linux), online (Client - Server) and with 3D graphics. I would like some suggestions to start with the right things. Currently I'm a PHP/MySQL coder, I used to code in C and Pascal on DOS ages (Borland Times ;)), my C knowlegde need a refresh but it's ok. I guess C++ it's the right language. What platform and what i should use to code? I can choose from all three platforms. My idea was to use Visual Studio 2010 C++, but i'm not sure if it support Native code. What kind of libraries should i use? I guessed OpenSSL for the login, OpenGL for graphics part. For the Audio or the GUI? Any other suggestions are well accepted. I know it's a "BIG DEAL" but I have no rush and it'll be a free-time project, only for my pleasure. Thank you in advance.

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• Trouble with AABB collision response and physics

  - by WCM

  I have been racking my brain trying to figure out a problem I am having with physics and basic AABB collision response. I am fairly close as the physics are mostly right. Gravity feels good and movement is solid. The issue I am running into is that when I land on the test block in my project, I can jump off of it most of the time. If I repeatedly jump in place, I will eventually get stuck one or two pixels below the surface of the test block. If I try to jump, I can become free of the other block, but it will happen again a few jumps later. I feel like I am missing something really obvious with this. I have two functions that support the detection and function to return a vector for the overlap of the two rectangle bounding boxes. I have a single update method that is processing the physics and collision for the entity. I feel like I am missing something very simple, like an ordering of the physics vs. collision response handling. Any thoughts or help can be appreciated. I apologize for the format of the code, tis prototype code mostly. The collision detection function: public static bool Collides(Rectangle source, Rectangle target) { if (source.Right < target.Left || source.Bottom < target.Top || source.Left > target.Right || source.Top > target.Bottom) { return false; } return true; } The overlap function: public static Vector2 GetMinimumTranslation(Rectangle source, Rectangle target) { Vector2 mtd = new Vector2(); Vector2 amin = source.Min(); Vector2 amax = source.Max(); Vector2 bmin = target.Min(); Vector2 bmax = target.Max(); float left = (bmin.X - amax.X); float right = (bmax.X - amin.X); float top = (bmin.Y - amax.Y); float bottom = (bmax.Y - amin.Y); if (left > 0 || right < 0) return Vector2.Zero; if (top > 0 || bottom < 0) return Vector2.Zero; if (Math.Abs(left) < right) mtd.X = left; else mtd.X = right; if (Math.Abs(top) < bottom) mtd.Y = top; else mtd.Y = bottom; // 0 the axis with the largest mtd value. if (Math.Abs(mtd.X) < Math.Abs(mtd.Y)) mtd.Y = 0; else mtd.X = 0; return mtd; } The update routine (gravity = 0.001f, jumpHeight = 0.35f, moveAmount = 0.15f): public void Update(GameTime gameTime) { Acceleration.Y = gravity; Position += new Vector2((float)(movement * moveAmount * gameTime.ElapsedGameTime.TotalMilliseconds), (float)(Velocity.Y * gameTime.ElapsedGameTime.TotalMilliseconds)); Velocity.Y += Acceleration.Y; Vector2 previousPosition = new Vector2((int)Position.X, (int)Position.Y); KeyboardState keyboard = Keyboard.GetState(); movement = 0; if (keyboard.IsKeyDown(Keys.Left)) { movement -= 1; } if (keyboard.IsKeyDown(Keys.Right)) { movement += 1; } if (Position.Y + 16 > GameClass.Instance.GraphicsDevice.Viewport.Height) { Velocity.Y = 0; Position = new Vector2(Position.X, GameClass.Instance.GraphicsDevice.Viewport.Height - 16); IsOnSurface = true; } if (Collision.Collides(BoundingBox, GameClass.Instance.block.BoundingBox)) { Vector2 mtd = Collision.GetMinimumTranslation(BoundingBox, GameClass.Instance.block.BoundingBox); Position += mtd; Velocity.Y = 0; IsOnSurface = true; } if (keyboard.IsKeyDown(Keys.Space) && !previousKeyboard.IsKeyDown(Keys.Space)) { if (IsOnSurface) { Velocity.Y = -jumpHeight; IsOnSurface = false; } } previousKeyboard = keyboard; } This is also a full download to the project. https://www.box.com/s/3rkdtbso3xgfgc2asawy P.S. I know that I could do this with the XNA Platformer Starter Kit algo, but it has some deep flaws that I am going to try to live without. I'd rather go the route of collision response via an overlay function. Thanks for any and all insight!

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• How to calculate vertext normals for a mesh in Java in OpenGL ES application?

  - by alan mc

  Can some one point me to Java code ( in Java not C or C++) that calculates all the normals for all the vertices of a mesh for OpenGL ES application. I need this for lighting. Lets say I have a cube with following vertices and indices: float vertices[] = { -width, -height, -depth, // 0 width, -height, -depth, // 1 width, height, -depth, // 2 -width, height, -depth, // 3 -width, -height, depth, // 4 width, -height, depth, // 5 width, height, depth, // 6 -width, height, depth // 7 }; short indices[] = { 0, 2, 1, 0, 3, 2, 1,2,6, 6,5,1, 4,5,6, 6,7,4, 2,3,6, 6,3,7, 0,7,3, 0,4,7, 0,1,5, 0,5,4 }; In above specific example how many normals we need ?

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• How to code Time Stop or Bullet Time in a game?

  - by David Miler

  I am developing a single-player RPG platformer in XNA 4.0. I would like to add an ability that would make the time "stop" or slow down, and have only the player character move at the original speed(similar to the Time Stop spell from the Baldur's Gate series). I am not looking for an exact implementation, rather some general ideas and design-patterns. EDIT: Thanks all for the great input. I have come up with the following solution public void Update(GameTime gameTime) { GameTime newGameTime = new GameTime(gameTime.TotalGameTime, new TimeSpan(gameTime.ElapsedGameTime.Ticks / DESIRED_TIME_MODIFIER)); gameTime = newGameTime; or something along these lines. This way I can set a different time for the player component and different for the rest. It certainly is not universal enough to work for a game where warping time like this would be a central element, but I hope it should work for this case. I kinda dislike the fact that it litters the main Update loop, but it certainly is the easiest way to implement it. I guess that is essentialy the same as tesselode suggested, so I'm going to give him the green tick :)

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• What data should be cached in a multiplayer server, relative to AI and players?

  - by DevilWithin

  In a virtual place, fully network driven, with an arbitrary number of players and an arbitrary number of enemies, what data should be cached in the server memory, in order to optimize smooth AI simulation? Trying to explain, lets say player A sees player B to E, and enemy A to G. Each of those players, see player A, but not necessarily each other. Same applies to enemies. Think of this question from a topdown perspective please. In many cases, for example, when a player shoots his gun, the server handles the sound as a radial "signal" that every other entity within reach "hear" and react upon. Doing these searches all the time for a whole area, containing possibly a lot of unrelated players and enemies, seems to be an issue, when the budget for each AI agent is so small. Should every entity cache whatever enters and exits from its radius of awareness? Is there a great way to trace the entities close by without flooding the memory with such caches? What about other AI related problems that may arise, after assuming the previous one works well? We're talking about environments with possibly hundreds of enemies, a swarm.

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• Procedurally generated 2d terrain for side scroller on Sega Genesis hardware?

  - by DJCouchyCouch

  I'm working on the Sega Genesis that has a 8mhz Motorola 68000 CPU. Any ideas on how to generate fast and decent 2d tile terrain for a side scroller in real time? The game would generate new columns or rows depending on the direction the player is scrolling in. The generation would have to be deterministic. The same seed value would generate the same terrain. I'm looking for algorithms that would satisfy the memory and CPU constraints of the hardware.

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• Displaying and updating score in Android (OpenGL ES 2)

  - by user16547

  I'm using a FrameLayout where I have a GLSurfaceView at the bottom and a few Views on top of it. One of those Views is a TextView that displays the current score. Here's how I'm updating the score TextView based on what happens in my game loop: whenever an event happens that increases the score, I call activity.runOnUiThread(updater), where activity is the activity that has the above FrameLayout (my main game activity) and updater is just a Runnable that increments the score. From my understanding, using runOnUiThread() from the OpenGL thread is standard practice - otherwise you'll get an exception, I can't remember its name. The problem is that there's a very noticeable lag between the event and the score update. For example the character gets a coin, but the coin count is not updated quickly. I tried summing all the score events from my game loop and calling runOnUiThread() only once per loop, but it doesn't seem to make much of a difference - the lag is still noticeable. How can I improve my design to avoid this lag?

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• Is this technique for stat tracking without a database workable?

  - by baptzmoffire

  If I wanted to create a chess game, for iOS, that tracked both player moves (for retracing the progression of a game and for player stats), what would be the simplest route to take? To clarify, I want to track not only the moves a player has made in a particular game, but how often that player has made that move in past games. For example I want to be able to track: How many times a given player has opened by moving the king pawn up two squares (e4) as white, on move number one. What is the percentage of time the player responds to white's e4 opening move, with moving his own king pawn to e5? What percentage of time does he respond by moving his queenside bishop pawn to c5? And so on. If it's not clear, the stat tracking system should also be able to report how many times this player, as black, move his queen to h1, on move number 30. I'm using Parse.com for my back-end as a server (BaaS) service. If I were to create a class that writes strings that identify move number, player color, moved piece, algebraic notation of the square (e.g. "d8") to a file, locally in the file system saves the file to Parse, and deletes the temporary file from file system upon opening the same game in my tableview (a la a "With Friends" game), download this file from Parse, parse through it and retrieve all stats/history, assign all relevant values to variables Is this plan viable, or is there an easier way?

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• How to convert pitch and yaw to x, y, z rotations?

  - by Aaron Anodide

  I'm a beginner using XNA to try and make a 3D Asteroids game. I'm really close to having my space ship drive around as if it had thrusters for pitch and yaw. The problem is I can't quite figure out how to translate the rotations, for instance, when I pitch forward 45 degrees and then start to turn - in this case there should be rotation being applied to all three directions to get the "diagonal yaw" - right? I thought I had it right with the calculations below, but they cause a partly pitched forward ship to wobble instead of turn.... :( So my quesiton is: how do you calculate the X, Y, and Z rotations for an object in terms of pitch and yaw? Here's current (almost working) calculations for the Rotation acceleration: float accel = .75f; // Thrust +Y / Forward if (currentKeyboardState.IsKeyDown(Keys.I)) { this.ship.AccelerationY += (float)Math.Cos(this.ship.RotationZ) * accel; this.ship.AccelerationX += (float)Math.Sin(this.ship.RotationZ) * -accel; this.ship.AccelerationZ += (float)Math.Sin(this.ship.RotationX) * accel; } // Rotation +Z / Yaw if (currentKeyboardState.IsKeyDown(Keys.J)) { this.ship.RotationAccelerationZ += (float)Math.Cos(this.ship.RotationX) * accel; this.ship.RotationAccelerationY += (float)Math.Sin(this.ship.RotationX) * accel; this.ship.RotationAccelerationX += (float)Math.Sin(this.ship.RotationY) * accel; } // Rotation -Z / Yaw if (currentKeyboardState.IsKeyDown(Keys.K)) { this.ship.RotationAccelerationZ += (float)Math.Cos(this.ship.RotationX) * -accel; this.ship.RotationAccelerationY += (float)Math.Sin(this.ship.RotationX) * -accel; this.ship.RotationAccelerationX += (float)Math.Sin(this.ship.RotationY) * -accel; } // Rotation +X / Pitch if (currentKeyboardState.IsKeyDown(Keys.F)) { this.ship.RotationAccelerationX += accel; } // Rotation -X / Pitch if (currentKeyboardState.IsKeyDown(Keys.D)) { this.ship.RotationAccelerationX -= accel; } I'm combining that with drawing code that does a rotation to the model: public void Draw(Matrix world, Matrix view, Matrix projection, TimeSpan elsapsedTime) { float seconds = (float)elsapsedTime.TotalSeconds; // update velocity based on acceleration this.VelocityX += this.AccelerationX * seconds; this.VelocityY += this.AccelerationY * seconds; this.VelocityZ += this.AccelerationZ * seconds; // update position based on velocity this.PositionX += this.VelocityX * seconds; this.PositionY += this.VelocityY * seconds; this.PositionZ += this.VelocityZ * seconds; // update rotational velocity based on rotational acceleration this.RotationVelocityX += this.RotationAccelerationX * seconds; this.RotationVelocityY += this.RotationAccelerationY * seconds; this.RotationVelocityZ += this.RotationAccelerationZ * seconds; // update rotation based on rotational velocity this.RotationX += this.RotationVelocityX * seconds; this.RotationY += this.RotationVelocityY * seconds; this.RotationZ += this.RotationVelocityZ * seconds; Matrix translation = Matrix.CreateTranslation(PositionX, PositionY, PositionZ); Matrix rotation = Matrix.CreateRotationX(RotationX) * Matrix.CreateRotationY(RotationY) * Matrix.CreateRotationZ(RotationZ); model.Root.Transform = rotation * translation * world; model.CopyAbsoluteBoneTransformsTo(boneTransforms); foreach (ModelMesh mesh in model.Meshes) { foreach (BasicEffect effect in mesh.Effects) { effect.World = boneTransforms[mesh.ParentBone.Index]; effect.View = view; effect.Projection = projection; effect.EnableDefaultLighting(); } mesh.Draw(); } }

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