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  • One True Event Loop

    - by CyberShadow
    Simple programs that collect data from only one system need only one event loop. For example, Windows applications have the message loop, POSIX network programs usually have a select/epoll/etc. loop at their core, pure SDL games use SDL's event loop. But what if you need to collect events from several subsystems? Such as an SDL game which doesn't use SDL_net for networking. I can think of several solutions: Polling (ugh) Put each event loop in its own thread, and: Send messages to the main thread, which collects and processes the events, or Place the event-processing code of each thread in a critical section, so that the threads can wait for events asynchronously but process them synchronously Choose one subsystem for the main event loop, and pass events from other subsystems via that subsystem as custom messages (for example, the Windows message loop and custom messages, or a socket select() loop and passing events via a loopback connection). Option 2.1 is more interesting on platforms where message-passing is a well-developed threading primitive (e.g. in the D programming language), but 2.2 looks like the best option to me.

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  • Proper updating of GeoClipMaps

    - by thr
    I have been working on an implementation of gpu-based geo clip maps, but there is a section of the GPU Gems 2 article that i just can't seem to understand, specifically this paragraph and more precisely the bolded part: The choice of grid size n = 2k-1 has the further advantage that the finer level is never exactly centered with respect to its parent next-coarser level. In other words, it is always offset by 1 grid unit either left or right, as well as either top or bottom (see Figure 2-4), depending on the position of the viewpoint. In fact, it is necessary to allow a finer level to shift while its next-coarser level stays fixed, and therefore the finer level must sometimes be off-center with respect to the next-coarser level. An alternative choice of grid size, such as n = 2k-3, would provide the possibility for exact centering Let's take an example image from the article: My "understanding" of the way the clip maps were update was that you floor the position of the viewpoint to an int, and such get the center vertex point if this is not the same as the previous center point, you update the entire map. Now, this obviously is not the case - but what I am failing to understand is this: If you look at the image above, if the viewpoint was to move one unit to the right, then the inner ring (the one just around the view point + white center square) would end up getting a 1 unit space on both the left and right side of itself. But there is nothing in the paper that deals with this, what i mean is that it would end up looking like this (excuse my crummy cut-and-paste editing of the above image): This is obviously not a valid state of the. So, would the solution be that a clip ring (layer) can only move in increments of the ring/layer it's contained within? Wouldn't this end up being very restrictive? I feel like I am missing some crucial understanding of parts of the algorithm, but I have been over both this paper and the original paper from 2004 and I just can't see what I am not getting.

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  • 2D Car Simulation with Throttle Linear Physics

    - by James
    I'm trying to make a simulation game for an automatic cruise control system. The system simulates a car on varying inclinations and throttle speeds. I've coded up to the car physics but these do note make sense. The dynamics of the simulation are specified as follows: a = V' - V T = (k1)V + ?(k2) + ma V' = (1 - (k1 / m) V) + T - ( k2 / m) * ? Where T = throttle position k1 = viscous friction V = speed V' = next speed ? = angle of incline k2 = m g sin ? a = acceleration m = mass Notice that the angle of incline in the equation is not chopped up by sin or cos. Even the equation for acceleration isn't right. Can anyone correct them or am I misinterpreting the physics?

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  • Markup format or script for data files?

    - by Aaron
    The game I'm designing will be mainly written in a high level scripting language (leaning towards either Lua or Squirrel) with a C++ core. In addition to scripts I'm also going to need different data files. Many data files will be for static information such as graphical assets and monster types. I'd also want to create and update data files at runtime for user information like option settings and game saves. Can I get away with using plain script files (i.e. .lua or .nut files) for my data files, or is it better to use dedicated markup formats like XML or YAML? If I use script files, loaded separately from my true scripts, then I wouldn't need an extra library to read those files. Scripting languages like Lua also have table syntax that lend themselves towards data definition. On the other hand I'd have to write my own schema check code. These languages also don't seem to support serialization "out of the box" like the markup format libraries do.

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  • Character jump animation is not working when i hit the space bar

    - by muzzy
    i am having an issue with my game in XNA. My jump sprite sheet for my character does not trigger when i hit the space bar. I cant seem to find the problem. Please help me. I am also put the code below to make things easier. namespace WindowsGame4 { public class Game1 : Microsoft.Xna.Framework.Game { GraphicsDeviceManager graphics; SpriteBatch spriteBatch; // start of new code Texture2D playerWalk; // sprite sheet of walk cycle (14 frames) Texture2D idle; // idle animation Texture2D jump; // jump animation Vector2 playerPos; // to hold x and y position info for the player Point frameDimensions; // to hold width and height values for the frames int presentFrame; // to record which frame we are on at any given time int noOfFrames; // to hold the total number of frames in the spritesheet int elapsedTime; // to know how long each frame has been shown int frameDuration; // to hold info about how long each frame should be shown SpriteEffects flipDirection; // SpriteEffects object int speed; //rate of movement int upMovement; int downMovement; int rightMovement; int leftMovement; int jumpApex; string state; //this is going to be "idle","walking" or "jumping". KeyboardState previousKeyboardState; Vector2 originalPlayerPos; Vector2 movementDirection; Vector2 movementSpeed; public Game1() { graphics = new GraphicsDeviceManager(this); Content.RootDirectory = "Content"; } protected override void Initialize() { // textures will be defined in the LoadContent() method playerPos = new Vector2(0, 200); // starting position for the player is at the left of the screen, and a Y position of 200 frameDimensions = new Point(55, 65); // each frame in the idle sprite sheet is 55 wide by 65 high presentFrame = 0; // start at frame 0 noOfFrames = 5; // there are 5 frames in the idle cycle elapsedTime = 0; // set elapsed time to start at 0 frameDuration = 80; // 80 milliseconds is how long each frame will show for (the higher the number, the slower the animation) flipDirection = SpriteEffects.None; // set the value of flipDirection to none speed = 200; upMovement = -2; downMovement = 2; rightMovement = 1; leftMovement = -1; jumpApex = 100; state = "idle"; previousKeyboardState = Keyboard.GetState(); originalPlayerPos = Vector2.Zero; movementDirection = Vector2.Zero; movementSpeed = Vector2.Zero; base.Initialize(); } protected override void LoadContent() { spriteBatch = new SpriteBatch(GraphicsDevice); playerWalk = Content.Load<Texture2D>("sprites/walkSmall"); // load the walk cycle spritesheet idle = Content.Load<Texture2D>("sprites/idleCycle"); // load the idle cycle sprite sheet jump = Content.Load<Texture2D>("sprites/jump"); // load the jump cycle sprite sheet } protected override void UnloadContent() // we're not using this method at the moment { } protected override void Update(GameTime gameTime) // Update method - used it to call a number of other methods { if (Keyboard.GetState().IsKeyDown(Keys.Escape)) { this.Exit(); // Exit the game if the Escape key is pressed } KeyboardState presentKeyboardState = Keyboard.GetState(); UpdateMovement(presentKeyboardState, gameTime); UpdateIdle(presentKeyboardState, gameTime); UpdateJump(presentKeyboardState); UpdateAnimation(gameTime); playerPos += movementDirection * movementSpeed * (float)gameTime.ElapsedGameTime.TotalSeconds; previousKeyboardState = presentKeyboardState; base.Update(gameTime); } private void UpdateAnimation(GameTime gameTime) { elapsedTime += gameTime.ElapsedGameTime.Milliseconds; if (elapsedTime > frameDuration) { elapsedTime -= frameDuration; elapsedTime = elapsedTime - frameDuration; presentFrame++; if (presentFrame > noOfFrames) if (state != "jumping") { presentFrame = 0; } else { presentFrame = 8; } } } protected void UpdateMovement(KeyboardState presentKeyboardState, GameTime gameTime) { if (state == "idle") { movementSpeed = Vector2.Zero; movementDirection = Vector2.Zero; if (presentKeyboardState.IsKeyDown(Keys.Left)) { state = "walking"; movementSpeed.X = speed; movementDirection.X = leftMovement; flipDirection = SpriteEffects.FlipHorizontally; } if (presentKeyboardState.IsKeyDown(Keys.Right)) { state = "walking"; movementSpeed.X = speed; movementDirection.X = rightMovement; flipDirection = SpriteEffects.None; } } } private void UpdateIdle(KeyboardState presentKeyboardState, GameTime gameTime) { if ((presentKeyboardState.IsKeyUp(Keys.Left) && previousKeyboardState.IsKeyDown(Keys.Left) || presentKeyboardState.IsKeyUp(Keys.Right) && previousKeyboardState.IsKeyDown(Keys.Right) && state != "jumping")) { state = "idle"; } } private void UpdateJump(KeyboardState presentKeyboardState) { if (state == "walking" || state == "idle") { if (presentKeyboardState.IsKeyDown(Keys.Space) && !presentKeyboardState.IsKeyDown(Keys.Space)) { presentFrame = 1; DoJump(); } } if (state == "jumping") { if (originalPlayerPos.Y - playerPos.Y > jumpApex) { movementDirection.Y = downMovement; } if (playerPos.Y > originalPlayerPos.Y) { playerPos.Y = originalPlayerPos.Y; state = "idle"; movementDirection = Vector2.Zero; } } } private void DoJump() { if (state != "jumping") { state = "jumping"; originalPlayerPos = playerPos; movementDirection.Y = upMovement; movementSpeed = new Vector2(speed, speed); } } protected override void Draw(GameTime gameTime) // Draw method { GraphicsDevice.Clear(Color.CornflowerBlue); spriteBatch.Begin(); // begin the spritebatch if (state == "walking") { noOfFrames = 14; frameDimensions = new Point(55, 65); Vector2 playerWalkPos = new Vector2(playerPos.X, playerPos.Y - 28); spriteBatch.Draw(playerWalk, playerWalkPos, new Rectangle((presentFrame * frameDimensions.X), 0, frameDimensions.X, frameDimensions.Y), Color.White, 0, Vector2.Zero, 1, flipDirection, 0); } if (state == "idle") { noOfFrames = 5; frameDimensions = new Point(55, 65); Vector2 idlePos = new Vector2(playerPos.X, playerPos.Y - 28); spriteBatch.Draw(idle, idlePos, new Rectangle((presentFrame * frameDimensions.X), 0, frameDimensions.X, frameDimensions.Y), Color.White, 0, Vector2.Zero, 1, flipDirection, 0); } if (state == "jumping") { noOfFrames = 9; frameDimensions = new Point(55, 92); Vector2 jumpPos = new Vector2(playerPos.X, playerPos.Y - 28); spriteBatch.Draw(jump, jumpPos, new Rectangle((presentFrame * frameDimensions.X), 0, frameDimensions.X, frameDimensions.Y), Color.White, 0, Vector2.Zero, 1, flipDirection, 0); } spriteBatch.End(); // end the spritebatch commands base.Draw(gameTime); } } }

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  • Finding closest object to a location within a specific perpendicular distance to direction vector

    - by Sniper
    I have a location and a direction vector indicating facing, I want to find the closest object to that location that is within some tolerance distance (perpendicular distance) to the ray formed by the location and direction vector. Basically I want to get the object that is being aimed at. I have thought about finding all objects within a box and then finding the closest object to my vector from them results, but I am sure that there is a more efficient way. The Z axis is optional, the objects are most likely within a few meters of the search vector.

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  • What sort of leaderboard for my game?

    - by Martin
    I recently published a word game for Windows Phone and I am really happy to have some players. The game is entirely offline and at the end of a game, the player's score is published to a server. I'm collecting the scores to build a leaderboard. Right now, I don't believe that the leaderboard I offer to my users is appropriate. I essentially accumulate the score of all the games of a user for a given day and that becomes their score. So if Player 1 plays 3 games and gets 100, 150 and 200 points, its score for the day is 450 points. I would like to get your ideas and opinion. How do I keep my game challenging and engaging with a good leaderboard? Should I continue accumulating the score for a day? Should I just keep the best score? Thanks!

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  • OpenGL sprites and point size limitation

    - by Srdan
    I'm developing a simple particle system that should be able to perform on mobile devices (iOS, Andorid). My plan was to use GL_POINT_SPRITE/GL_PROGRAM_POINT_SIZE method because of it's efficiency (GL_POINTS are enough), but after some experimenting, I found myself in a trouble. Sprite size is limited (to usually 64 pixels). I'm calculating size using this formula gl_PointSize = in_point_size * some_factor / distance_to_camera to make particle sizes proportional to distance to camera. But at some point, when camera is close enough, problem with size limitation emerges and whole system starts looking unrealistic. Is there a way to avoid this problem? If no, what's alternative? I was thinking of manually generating billboard quad for each particle. Now, I have some questions about that approach. I guess minimum geometry data would be four vertices per particle and index array to make quads from these vertices (with GL_TRIANGLE_STRIP). Additionally, for each vertex I need a color and texture coordinate. I would put all that in an interleaved vertex array. But as you can see, there is much redundancy. All vertices of same particle share same color value, and four texture coordinates are same for all particles. Because of how glDrawArrays/Elements works, I see no way to optimise this. Do you know of a better approach on how to organise per-particle data? Should I use buffers or vertex arrays, or there is no difference because each time I have to update all particles' data. About particles simulation... Where to do it? On CPU or on a vertex processors? Something tells me that mobile's CPU would do it faster than it's vertex unit (at least today in 2012 :). So, any advice on how to make a simple and efficient particle system without particle size limitation, for mobile device, would be appreciated. (animation of camera passing through particles should be realistic)

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  • Simple Math Multiplayer game - is Ajax sufficient?

    - by Christian Strang
    I'm planning to create a simple math multiplayer game and I plan to just use Ajax for the server/client communication but I'm not sure if this is sufficient or if I need a socket server. The game will look like this: 2-4 users all get a simple math task (like: "37 + 14") they have to solve it as fast as possible first user who solves it is the winner I will track the time for each user, since the game started, on the client side and everytime a user gives an answer, the answer and the passed time will be send to the server. Additionally I'll add a function which will check every 3 seconds if the other users finished, how much time they needed and who won. Do you think this is possible just using Ajax? What alternatives are there?

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  • Bitmap Font Displays in Center Always Without Coding it Manually (Fix Coordinate Problem onText)

    - by David Dimalanta
    Is there a way on how to stay the texts in center without manually coding it or something, especially when making an update? I'm making a display for the highest score. Let's say that the score is 9. However, if the score is 9,999,999, the text displays still only at the fixed X and Y coordinate. Is there really a way to stay the text in center especially when there is changes when a player beats the new world record? Here's my code inside Sprite Batch: font.setScale(1.5f); font.draw(batch, "HIGHEST SCORE:", (900/10)*1 + 60, (1280/16)*10); font.draw(batch, "" + 9999999 + "", (900/10)*4, (1280/16)*8); batch.draw(grid_guide, 0, 0, 900, 1280); // --> For testing purpose only. // Where 9999999 is a new record score for example. Here's the image shown as example. I add it some red grid so that I could check if the display of score when updated will always display on center no matter how many digits takes place in. However, it is fixed, so I have to figure it out how to display it automatically on center regardless of the number of digits while updating for the new highscore. I have used the LibGDX preferences very well though to save and load records for the highscore.

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  • Beginner question about vertex arrays in OpenGL

    - by MrDatabase
    Is there a special order in which vertices are entered into a vertex array? Currently I'm drawing single textures like this: glBindTexture(GL_TEXTURE_2D, texName); glVertexPointer(2, GL_FLOAT, 0, vertices); glTexCoordPointer(2, GL_FLOAT, 0, coordinates); glDrawArrays(GL_TRIANGLE_STRIP, 0, 4); where vertices has four "xy pairs". This is working fine. As a test I doubled the sizes of the vertices and coordinates arrays and changed the last line above to: glDrawArrays(GL_TRIANGLE_STRIP, 0, 8); since vertices now contains eight "xy pairs". I do see two textures (the second is intentionally offset from the first). However the textures are now distorted. I've tried passing GL_TRIANGLES to glDrawArrays instead of GL_TRIANGLE_STRIP but this doesn't work either. I'm so new to OpenGL that I thought it's best to just ask here :-) Cheers!

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  • backface culling error (in world space)

    - by acrilige
    I write simple software renderer. In my pipeline i have stage of backface culling. But looks like it has some error (see picture). I perform culling right after world transformation (is it correct?). (i can't insert picture in post coz i don't have enough points, so i just upload it (cube model): http://imageshack.us/photo/my-images/705/bcerror.png/) Vector3F view_dir(0.0f, 0.0f, 1.0f); std::vector<Triangle> to_remove; for (Triangle &t : m_triangles) { Vector4F e1 = t.v2 - t.v1; Vector4F e2 = t.v3 - t.v1; Vector3F normal( e1.y * e2.z - e1.z * e2.y, e1.z * e2.x - e1.x * e2.z, e1.x * e2.y - e1.y * e2.x ); normal.Normalize(); float dot = Dot(view_dir, normal); if (dot <= 0) to_remove.push_back(t); } for (Triangle& t : to_remove) m_triangles.erase(std::remove(m_triangles.begin(), m_triangles.end(), t), m_triangles.end()); Camera sits in origin and points in screen (RH). What is the reason? For better explanation i upload picture with cube rotation screenshots: http://imageshack.us/photo/my-images/842/bcmove.png/ UPDATED: The error occurs only when triangle has non-zero offset from origin UPDATED 2: If i process backface culling in clip space (after transforming all vertices with view and projection matrix), and just check z coordinate of triangle normal - it works perfect... Can i perform culing RIGHT BEFORE view/proj transforms? In this case looks like culling will not depends of projection and it's not right?.. UPDATED 3: I found answer and will post it in two hours - again coz of reputation lack.

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  • Implementing a wheeled character controller

    - by Lazlo
    I'm trying to implement Boxycraft's character controller in XNA (with Farseer), as Bryan Dysmas did (minus the jumping part, yet). My current implementation seems to sometimes glitch in between two parallel planes, and fails to climb 45 degree slopes. (YouTube videos in links, plane glitch is subtle). How can I fix it? From the textual description, I seem to be doing it right. Here is my implementation (it seems like a huge wall of text, but it's easy to read. I wish I could simplify and isolate the problem more, but I can't): public Body TorsoBody { get; private set; } public PolygonShape TorsoShape { get; private set; } public Body LegsBody { get; private set; } public Shape LegsShape { get; private set; } public RevoluteJoint Hips { get; private set; } public FixedAngleJoint FixedAngleJoint { get; private set; } public AngleJoint AngleJoint { get; private set; } ... this.TorsoBody = BodyFactory.CreateRectangle(this.World, 1, 1.5f, 1); this.TorsoShape = new PolygonShape(1); this.TorsoShape.SetAsBox(0.5f, 0.75f); this.TorsoBody.CreateFixture(this.TorsoShape); this.TorsoBody.IsStatic = false; this.LegsBody = BodyFactory.CreateCircle(this.World, 0.5f, 1); this.LegsShape = new CircleShape(0.5f, 1); this.LegsBody.CreateFixture(this.LegsShape); this.LegsBody.Position -= 0.75f * Vector2.UnitY; this.LegsBody.IsStatic = false; this.Hips = JointFactory.CreateRevoluteJoint(this.TorsoBody, this.LegsBody, Vector2.Zero); this.Hips.MotorEnabled = true; this.AngleJoint = new AngleJoint(this.TorsoBody, this.LegsBody); this.FixedAngleJoint = new FixedAngleJoint(this.TorsoBody); this.Hips.MaxMotorTorque = float.PositiveInfinity; this.World.AddJoint(this.Hips); this.World.AddJoint(this.AngleJoint); this.World.AddJoint(this.FixedAngleJoint); ... public void Move(float m) // -1, 0, +1 { this.Hips.MotorSpeed = 0.5f * m; }

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  • rotate player based off of joystick

    - by pengume
    Hey everyone I have this game that i am making in android and I have a touch screen joystick that moves the player around based on the joysticks position. I cant figure out how to also get the player to rotate at the same angle of the joystick. so when the joystick is to the left the players bitmap is rotated to the left as well. Maybe someone here has some sample code I could look at here is the joysticks class that I am using. `public class GameControls implements OnTouchListener { public float initx = DroidzActivity.screenWidth - 45; //255; // 320 og 425 public float inity = DroidzActivity.screenHeight - 45;//425; // 480 og 267 public Point _touchingPoint = new Point( DroidzActivity.screenWidth - 45, DroidzActivity.screenHeight - 45); public Point _pointerPosition = new Point(DroidzActivity.screenWidth - 100, DroidzActivity.screenHeight - 100); // ogx 220 ogy 150 private Boolean _dragging = false; private boolean attackMode = false; @Override public boolean onTouch(View v, MotionEvent event) { update(event); return true; } private MotionEvent lastEvent; public boolean ControlDragged; private static double angle; public void update(MotionEvent event) { if (event == null && lastEvent == null) { return; } else if (event == null && lastEvent != null) { event = lastEvent; } else { lastEvent = event; } // drag drop if (event.getAction() == MotionEvent.ACTION_DOWN) { if ((int) event.getX() > 0 && (int) event.getX() < 50 && (int) event.getY() > DroidzActivity.screenHeight - 160 && (int) event.getY() < DroidzActivity.screenHeight - 0) { setAttackMode(true); } else { _dragging = true; } } else if (event.getAction() == MotionEvent.ACTION_UP) { if(isAttackMode()){ setAttackMode(false); } _dragging = false; } if (_dragging) { ControlDragged = true; // get the pos _touchingPoint.x = (int) event.getX(); _touchingPoint.y = (int) event.getY(); // Log.d("GameControls", "x = " + _touchingPoint.x + " y = " //+ _touchingPoint.y); // bound to a box if (_touchingPoint.x < DroidzActivity.screenWidth - 75) { // og 400 _touchingPoint.x = DroidzActivity.screenWidth - 75; } if (_touchingPoint.x > DroidzActivity.screenWidth - 15) {// og 450 _touchingPoint.x = DroidzActivity.screenWidth - 15; } if (_touchingPoint.y < DroidzActivity.screenHeight - 75) {// og 240 _touchingPoint.y = DroidzActivity.screenHeight - 75; } if (_touchingPoint.y > DroidzActivity.screenHeight - 15) {// og 290 _touchingPoint.y = DroidzActivity.screenHeight - 15; } // get the angle setAngle(Math.atan2(_touchingPoint.y - inity, _touchingPoint.x - initx) / (Math.PI / 180)); // Move the ninja in proportion to how far // the joystick is dragged from its center _pointerPosition.y += Math.sin(getAngle() * (Math.PI / 180)) * (_touchingPoint.x / 70); // og 180 70 _pointerPosition.x += Math.cos(getAngle() * (Math.PI / 180)) * (_touchingPoint.x / 70); // make the pointer go thru if (_pointerPosition.x > DroidzActivity.screenWidth) { _pointerPosition.x = 0; } if (_pointerPosition.x < 0) { _pointerPosition.x = DroidzActivity.screenWidth; } if (_pointerPosition.y > DroidzActivity.screenHeight) { _pointerPosition.y = 0; } if (_pointerPosition.y < 0) { _pointerPosition.y = DroidzActivity.screenHeight; } } else if (!_dragging) { ControlDragged = false; // Snap back to center when the joystick is released _touchingPoint.x = (int) initx; _touchingPoint.y = (int) inity; // shaft.alpha = 0; } } public void setAttackMode(boolean attackMode) { this.attackMode = attackMode; } public boolean isAttackMode() { return attackMode; } public void setAngle(double angle) { this.angle = angle; } public static double getAngle() { return angle; } }` I should also note that the player has animations based on when he is moving or attacking.

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  • Viewport / Camera Calculation in 2D Game

    - by Dave
    we have a 2D game with some sprites and tiles and some kind of camera/viewport, that "moves" around the scene. so far so good, if we wouldn't had some special behaviour for your camera/viewport translation. normally you could stick the camera to your player figure and center it, resulting in a very cheap, undergraduate, translation equation, like : vec_translation -/+= speed (depending in what keys are pressed. WASD as default.) buuuuuuuuuut, we want our player figure be able to actually reach the bounds, when the viewport/camera has reached a maximum translation. we came up with the following solution (only keys a and d are the shown here, the rest is just adaption of calculation or maybe YOUR super-cool and elegant solution :) ): if(keys[A]) { playerX -= speed; if(playerScreenX <= width / 2 && tx < 0) { playerScreenX = width / 2; tx += speed; } else if(playerScreenX <= width / 2 && (tx) >= 0) { playerScreenX -= speed; tx = 0; if(playerScreenX < 0) playerScreenX = 0; } else if(playerScreenX >= width / 2 && (tx) < 0) { playerScreenX -= speed; } } if(keys[D]) { playerX += speed; if(playerScreenX >= width / 2 && (-tx + width) < sceneWidth) { playerScreenX = width / 2; tx -= speed; } if(playerScreenX >= width / 2 && (-tx + width) >= sceneWidth) { playerScreenX += speed; tx = -(sceneWidth - width); if(playerScreenX >= width - player.width) playerScreenX = width - player.width; } if(playerScreenX <= width / 2 && (-tx + width) < sceneWidth) { playerScreenX += speed; } } i think the code is rather self explaining: keys is a flag container for currently active keys, playerX/-Y is the position of the player according to world origin, tx/ty are the translation components vital to background / npc / item offset calculation, playerOnScreenX/-Y is the actual position of the player figure (sprite) on screen and width/height are the dimensions of the camera/viewport. this all looks quite nice and works well, but there is a very small and nasty calculation error, which in turn sums up to some visible effect. let's consider following piece of code: if(playerScreenX <= width / 2 && tx < 0) { playerScreenX = width / 2; tx += speed; } it can be translated into plain english as : if the x position of your player figure on screen is less or equal the half of your display / camera / viewport size AND there is enough space left LEFT of your viewport/camera then set players x position on screen to width half, increase translation (because we subtract the translation from something we want to move). easy, right?! doing this will create a small delta between playerX and playerScreenX. after so much talking, my question appears now here at the bottom of this document: how do I stick the calculation of my player-on-screen to the actual position of the player AND having a viewport that is not always centered aroung the players figure? here is a small test-case in processing: http://pastebin.com/bFaTauaa thank you for reading until now and thank you in advance for probably answering my question.

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  • Checking whether a specific key was pressed in enchantJS

    - by MxyL
    I am using enchantJS and would like to use the letters and numbers as well as numpad on a keyboard to do different things (eg: hotkeys). From this page http://users.csc.calpoly.edu/~foaad/enchant/guide/playerInput.html By default, enchant.js provides input listeners for six buttons: UP, DOWN, LEFT, RIGHT, A, and B. By default, the directions are bound to the arrow keys. Any of the six buttons may also be bound to any key with an ASCII value. We’ll address that later. So enchant provides the ability to bind keys to different input such as up, down, left, right...but how can I simply check whether the D or X key was pressed, and if so, perform certain actions based on that event?

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  • Inverse projection: question about w coordinate

    - by fayeWilly
    I have to perform in shader an inverse projection from a u/v of a render target. What I do is: Get NDC as 2*(u,v,depth) - 1 Then world space as tmp = (P*V)^-1 * (NDC,1.0); world space = tmp/tmp.w; This apparently works, but I am confused about the w division there. Why this work? Shouldn't be a multiplication by a w somewhere (as in the "forward" pipeline there is the perpsective division?) Thank you, Faye

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  • Increasing speed of circle over time as linear with Box2d

    - by Whispered
    Assume that there is a circle and it can be moved by using keyboard arrows.Is required that increasing speed over time like increasing car speed. For example; max speed is 25 and time to reach max speed shall be 5 sec. Over 5 sec the speed will reach to max speed. Does Box2d handle that situation?. I tried setting linear valocity but it seems to make the circle have constant speed instead of increased speed over time. Thank You! Note: I'm using Box2DWeb Javascript port of Box2D.

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  • Break the object body

    - by Siddharth
    In my game, I want to break the object body creating slicing effect. After research I found that I have to use ray casting but I don't know how to use it. If some one know how to break the physics body then please provide information to me. EDIT : I don't have any logic how to do that in andengine. Only I have some link to do slicing http://www.emanueleferonato.com/2012/03/05/breaking-objects-with-box2d-the-realistic-way/ Yes I have to slice physics body into two parts. My physics body have 2d objects.

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  • Where to start learning OpenGL with C++?

    - by NERDcustard
    I'm 16 years old and my name is Norbert. I have learnt C++ and made some cool text based games and such but I would love to start graphic's programming. I'm a decent artiest (I will have some of my work bellow) I know the base of C++ but I really would like to get into OpenGL. I need someone to show me some good tutorials for OpenGl with C++ so I can really get into game dev. My goal is to be able to program a simple 2d game by the end of the year and I have lots of time to do so. I'm en-rolled in a game dev next year and really need some help with starting off. http://imgur.com/QZjKX http://imgur.com/3CZy7

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  • How to design a separated tutorial mode?

    - by Sylpheed
    I'm working on a "social" game that's about 90% completion. One of the remaining features is the tutorial mode. Basically, the tutorial mode will restrict the user to access some parts of UI and limit the features (like store items). The tutorial will only progress if a certain event is triggered, specifically following the tutorial. The code is ready and we already have an "almost" working game. The problem is I haven't foreseen the tutorial mode while I was doing those 90%. My requirement is there shouldn't be any loading/transition from tutorial mode to normal mode. This means I have to pick up the progress from the tutorial (no re-rendering of assets and stuff). How should I design this in a way where I won't touch anything from my old code? I want it to be as easy as just plugging it in. I don't want to jam the tutorial in my old code since this will lead to many bugs.

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  • 2D camera perspective projection from 3D coordinates -- HOW?

    - by Jack
    I am developing a camera for a 2D game with a top-down view that has depth. It's almost a 3D camera. Basically, every object has a Z even though it is in 2D, and similarly to parallax layers their position, scale and rotation speed vary based on their Z. I guess this would be a perspective projection. But I am having trouble converting the objects' 3D coordinates into the 2D space of the screen so that everything has correct perspective and scale. I never learned matrices though I did dig the topic a bit today. I tried without using matrices thanks to this article but every attempt gave awkward results. I'm using ActionScript 3 and Flash 11+ (Starling), where the screen coordinates work like this: Left-handed coordinates system illustration I can explain further what I did if you want to help me sort out what's wrong, or you can directly tell me how you would do it properly. In case you prefer the former, read on. These are images showing the formulas I used: upload.wikimedia.org/math/1/c/8/1c89722619b756d05adb4ea38ee6f62b.png upload.wikimedia.org/math/d/4/0/d4069770c68cb8f1aa4b5cfc57e81bc3.png (Sorry new users can't post images, but both are from the wikipedia article linked above, section "Perspective projection". That's where you'll find what all variables mean, too) The long formula is greatly simplified because I believe a normal top-down 2D camera has no X/Y/Z rotation values (correct ?). Then it becomes d = a - c. Still, I can't get it to work. Maybe you could explain what numbers I should put in a(xyz), c(xyz), theta(xyz), and particularly, e(xyz) ? I don't quite get how e is different than c in my case. c.z is also an issue to me. If the Z of the camera's target object is 0, should the camera's Z be something like -600 ? ( = focal length of 600) Whatever I do, it's wrong. I only got it to work when I used arbitrary calculations that "looked" right, like most cameras with parallax layers seem to do, but that's fake! ;) If I want objects to travel between Z layers I might as well do it right. :) Thanks a lot for your help!

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  • Why am I getting a return value of zero from my position computation function?

    - by Hussain Murtaza
    Ok I have a Function int x(), which is used in new Rectangle(x(),a,a,a); in DrawMethod in XNA but when I use it I get x() = 0 as as the answer.Here is my CODE: int x() { int px = (128 * 5); int xx = 0; for (int i = 0; i < 6; i++) { if (Mouse.GetState().X > px) { //xx = Mouse.GetState().X; xx = px; break; } else { px -= 128; } } return xx; } Here is the DrawMethod Code: if (set) { spriteBatch.Draw(texture, new Rectangle(x(), y(), texture.Width, texture.Height), Color.White); textpositionX = x(); textpositionY = y(); set = false; select = false; place = true; } else if(select) { spriteBatch.Draw(texture, new Rectangle(Mouse.GetState().X - texture.Width / 2, Mouse.GetState().Y-texture.Height / 2, texture.Width, texture.Height), Color.White); } else if (place) { spriteBatch.Draw(texture, new Rectangle(textpositionX, textpositionY, texture.Width, texture.Height), Color.White); select = false; set = false; }

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  • Ray Intersecting Plane Formula in C++/DirectX

    - by user4585
    I'm developing a picking system that will use rays that intersect volumes and I'm having trouble with ray intersection versus a plane. I was able to figure out spheres fairly easily, but planes are giving me trouble. I've tried to understand various sources and get hung up on some of the variables used within their explanations. Here is a snippet of my code: bool Picking() { D3DXVECTOR3 vec; D3DXVECTOR3 vRayDir; D3DXVECTOR3 vRayOrig; D3DXVECTOR3 vROO, vROD; // vect ray obj orig, vec ray obj dir D3DXMATRIX m; D3DXMATRIX mInverse; D3DXMATRIX worldMat; // Obtain project matrix D3DXMATRIX pMatProj = CDirectXRenderer::GetInstance()->Director()->Proj(); // Obtain mouse position D3DXVECTOR3 pos = CGUIManager::GetInstance()->GUIObjectList.front().pos; // Get window width & height float w = CDirectXRenderer::GetInstance()->GetWidth(); float h = CDirectXRenderer::GetInstance()->GetHeight(); // Transform vector from screen to 3D space vec.x = (((2.0f * pos.x) / w) - 1.0f) / pMatProj._11; vec.y = -(((2.0f * pos.y) / h) - 1.0f) / pMatProj._22; vec.z = 1.0f; // Create a view inverse matrix D3DXMatrixInverse(&m, NULL, &CDirectXRenderer::GetInstance()->Director()->View()); // Determine our ray's direction vRayDir.x = vec.x * m._11 + vec.y * m._21 + vec.z * m._31; vRayDir.y = vec.x * m._12 + vec.y * m._22 + vec.z * m._32; vRayDir.z = vec.x * m._13 + vec.y * m._23 + vec.z * m._33; // Determine our ray's origin vRayOrig.x = m._41; vRayOrig.y = m._42; vRayOrig.z = m._43; D3DXMatrixIdentity(&worldMat); //worldMat = aliveActors[0]->GetTrans(); D3DXMatrixInverse(&mInverse, NULL, &worldMat); D3DXVec3TransformCoord(&vROO, &vRayOrig, &mInverse); D3DXVec3TransformNormal(&vROD, &vRayDir, &mInverse); D3DXVec3Normalize(&vROD, &vROD); When using this code I'm able to detect a ray intersection via a sphere, but I have questions when determining an intersection via a plane. First off should I be using my vRayOrig & vRayDir variables for the plane intersection tests or should I be using the new vectors that are created for use in object space? When looking at a site like this for example: http://www.tar.hu/gamealgorithms/ch22lev1sec2.html I'm curious as to what D is in the equation AX + BY + CZ + D = 0 and how does it factor in to determining a plane intersection? Any help will be appreciated, thanks.

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  • Constrained/penalized distance function

    - by sigma.z.1980
    Assume a character is located on a n by n grid and has to reach a certain entry on that grid. Its current position is (x1,y1). Also on the same grid is an enemy with coordinates (x2,y2). Each step algorithm randomly generates new candidate locations for the hero (if there are k candidates then there is a kx2 matrix of new potential locations. What I need is some distance objective function to compare the candidates. I'm currently using d1 - c * d2, where d1 is distance to the objective (measure in terms of number of pixels for each axis), d2 is distance to the enemy and c is some coefficient (this is very much like a set-up for Lagrangian). It's not working very well though. I'd be quite keen to learn how what constrained distance function are used for similar cases. Any suggestions are very much appreciated.

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