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  • Help needed throwing a ball in AS3

    - by Opoe
    I'm working on a flash game, coding on the time line. What I'm trying to accomplish is the following: With the mouse you swing and throw/release a ball which bounces against the walls and eventualy comes to point where it lays still (like a real ball). I allmost had it working, but now the ball sticks to the mouse, in stead of being released, my question to you is: Can you help me make this work and explain to me what I did wrong? You can simply preview my code by making a movieclip named 'circle' on a 550x400 stage. stage.addEventListener(Event.ENTER_FRAME, circle_update); var previousPostionX:Number; var previousPostionY:Number; var throwSpeedX:Number; var throwSpeedY:Number; var isItDown:Boolean; var xSpeed:Number = 0; var ySpeed:Number = 0; var friction:Number = 0.96; var offsetX:Number = 0; var offsetY:Number = 0; var newY:Number = 0; var oldY:Number = 0; var newX:Number = 0; var oldX:Number = 0; var dragging:Boolean; circle.buttonMode = true; circle.addEventListener(MouseEvent.MOUSE_DOWN, mouseDownHandler); circle.addEventListener(Event.ENTER_FRAME, throwcircle); circle.addEventListener(MouseEvent.MOUSE_DOWN, clicked); circle.addEventListener(MouseEvent.MOUSE_UP, released); function mouseDownHandler(e:MouseEvent):void { dragging = true; stage.addEventListener(MouseEvent.MOUSE_UP, mouseUpHandler); offsetX = mouseX - circle.x; offsetY = mouseY - circle.y; } function mouseUpHandler(e:MouseEvent):void { dragging = false; } function throwcircle(e:Event) { circle.x += xSpeed; circle.y += ySpeed; xSpeed *= friction; ySpeed *= friction; } function changeFriction(e:Event):void { friction = e.target.value; trace(e.target.value); } function circle_update(e:Event){ if ( dragging == true ) { circle.x = mouseX - offsetX; circle.y = mouseY - offsetY; } if(circle.x + (circle.width * 0.50) >= 550){ circle.x = 550 - circle.width * 0.50; } if(circle.x - (circle.width * 0.50) <= 0){ circle.x = circle.width * 0.50; } if(circle.y + (circle.width * 0.50) >= 400){ circle.y = 400 - circle.height * 0.50; } if(circle.y - (circle.width * 0.50) <= 0){ circle.y = circle.height * 0.50; } } function clicked(theEvent:Event) { isItDown =true; addEventListener(Event.ENTER_FRAME, updateView); } function released(theEvent:Event) { isItDown =false; } function updateView(theEvent:Event) { if (isItDown==true){ throwSpeedX = mouseX - previousPostionX; throwSpeedY = mouseY - previousPostionY; circle.x = mouseX; circle.y = mouseY; } else{ circle.x += throwSpeedX; circle.y += throwSpeedY; throwSpeedX *=0.9; throwSpeedY *=0.9; } previousPostionX= circle.x; previousPostionY= circle.y; }

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

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

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  • Questions about game states

    - by MrPlow
    I'm trying to make a framework for a game I've wanted to do for quite a while. The first thing that I decided to implement was a state system for game states. When my "original" idea of having a doubly linked list of game states failed I found This blog and liked the idea of a stack based game state manager. However there were a few things I found weird: Instead of RAII two class methods are used to initialize and destroy the state Every game state class is a singleton(and singletons are bad aren't they?) Every GameState object is static So I took the idea and altered a few things and got this: GameState.h class GameState { private: bool m_paused; protected: StateManager& m_manager; public: GameState(StateManager& manager) : m_manager(manager), m_paused(false){} virtual ~GameState() {} virtual void update() = 0; virtual void draw() = 0; virtual void handleEvents() = 0; void pause() { m_paused = true; } void resume() { m_paused = false; } void changeState(std::unique_ptr<GameState> state) { m_manager.changeState(std::move(state)); } }; StateManager.h class GameState; class StateManager { private: std::vector< std::unique_ptr<GameState> > m_gameStates; public: StateManager(); void changeState(std::unique_ptr<GameState> state); void StateManager::pushState(std::unique_ptr<GameState> state); void popState(); void update(); void draw(); void handleEvents(); }; StateManager.cpp StateManager::StateManager() {} void StateManager::changeState( std::unique_ptr<GameState> state ) { if(!m_gameStates.empty()) { m_gameStates.pop_back(); } m_gameStates.push_back( std::move(state) ); } void StateManager::pushState(std::unique_ptr<GameState> state) { if(!m_gameStates.empty()) { m_gameStates.back()->pause(); } m_gameStates.push_back( std::move(state) ); } void StateManager::popState() { if(!m_gameStates.empty()) m_gameStates.pop_back(); } void StateManager::update() { if(!m_gameStates.empty()) m_gameStates.back()->update(); } void StateManager::draw() { if(!m_gameStates.empty()) m_gameStates.back()->draw(); } void StateManager::handleEvents() { if(!m_gameStates.empty()) m_gameStates.back()->handleEvents(); } And it's used like this: main.cpp StateManager states; states.changeState( std::unique_ptr<GameState>(new GameStateIntro(states)) ); while(gamewindow::gameWindow.isOpen()) { states.handleEvents(); states.update(); states.draw(); } Constructors/Destructors are used to create/destroy states instead of specialized class methods, state objects are no longer static but

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  • GLSL Shader Effects: How to do motion blur, etc?

    - by DevilWithin
    I am not sure how right it is to ask this question, but still here it goes. I have a full 2D environment, with sprites going around as landscape, characters, etc And to make it more state-of-art looking, i want to implement a motion blur effect, similar to modern FPS's (i.e. crysis) blur when moving fast the camera. In a sidescroller, the desired effect is having this slight blur appearing to give the idea of fast movement, when the camera is moving. If anyone could give me some tips on doing this, im assuming in a pixel shader, i'd be grate. Also, if anyone has other good tips on cool pixel shader effects for 2D games it would be awesome, like some stylizing post fx, such as previous Prince of Persia illustrative style. Thanks

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  • Pre game loading time vs. in game loading time

    - by Keeper
    I'm developing a game in which a random maze is included. There are some AI creatures, lurking the maze. And I want them to go in some path according to the mazes shape. Now there are two possibilities for me to implement that, the first way (which I used) is by calculating several wanted lurking paths once the maze is created. The second, is by calculating a path once needed to be calculated, when a creature starts lurking it. My main concern is loading times. If I calculate many paths at the creating of the maze, the pre loading time is a bit long, so I thought about calculating them when needed. At the moment the game is not 'heavy' so calculating paths in mid game is not noticeable, but I'm afraid it will once it will get more complicated. Any suggestions, comments, opinions, will be of help. Edit: As for now, let p be the number of pre-calculated paths, a creatures has the probability of 1/p to take a new path (which means a path calculation) instead of an existing one. A creature does not start its patrol until the path is fully calculated of course, so no need to worry about him getting killed in the process.

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  • Resultant Vector Algorithm for 2D Collisions

    - by John
    I am making a Pong based game where a puck hits a paddle and bounces off. Both the puck and the paddles are Circles. I came up with an algorithm to calculate the resultant vector of the puck once it meets a paddle. The game seems to function correctly but I'm not entirely sure my algorithm is correct. Here are my variables for the algorithm: Given: velocity = the magnitude of the initial velocity of the puck before the collision x = the x coordinate of the puck y = the y coordinate of the puck moveX = the horizontal speed of the puck moveY = the vertical speed of the puck otherX = the x coordinate of the paddle otherY = the y coordinate of the paddle piece.horizontalMomentum = the horizontal speed of the paddle before it hits the puck piece.verticalMomentum = the vertical speed of the paddle before it hits the puck slope = the direction, in radians, of the puck's velocity distX = the horizontal distance between the center of the puck and the center of the paddle distY = the vertical distance between the center of the puck and the center of the paddle Algorithm solves for: impactAngle = the angle, in radians, of the angle of impact. newSpeedX = the speed of the resultant vector in the X direction newSpeedY = the speed of the resultant vector in the Y direction Here is the code for my algorithm: int otherX = piece.x; int otherY = piece.y; double velocity = Math.sqrt((moveX * moveX) + (moveY * moveY)); double slope = Math.atan(moveX / moveY); int distX = x - otherX; int distY = y - otherY; double impactAngle = Math.atan(distX / distY); double newAngle = impactAngle + slope; int newSpeedX = (int)(velocity * Math.sin(newAngle)) + piece.horizontalMomentum; int newSpeedY = (int)(velocity * Math.cos(newAngle)) + piece.verticalMomentum; for those who are not program savvy here is it simplified: velocity = v(moveX² + moveY²) slope = arctan(moveX / moveY) distX = x - otherX distY = y - otherY impactAngle = arctan(distX / distY) newAngle = impactAngle + slope newSpeedX = velocity * sin(newAngle) + piece.horizontalMomentum newSpeedY = velocity * cos(newAngle) + piece.verticalMomentum My Question: Is this algorithm correct? Is there an easier/simpler way to do what I'm trying to do?

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  • How to correctly export UV coordinates from Blender

    - by KlashnikovKid
    Alright, so I'm just now getting around to texturing some assets. After much trial and error I feel I'm pretty good at UV unwrapping now and my work looks good in Blender. However, either I'm using the UV data incorrectly (I really doubt it) or Blender doesn't seem to export the correct UV coordinates into the obj file because the texture is mapped differently in my game engine. And in Blender I've played with the texture panel and it's mapping options and have noticed it doesn't appear to affect the exported obj file's uv coordinates. So I guess my question is, is there something I need to do prior to exporting in order to bake the correct UV coordinates into the obj file? Or something else that needs to be done to massage the texture coordinates for sampling. Or any thoughts at all of what could be going wrong? (Also here is a screen shot of my diffused texture in blender and the game engine. As you can see in the image, I have the same problem with a simple test cube not getting correct uv's either) http://www.digitalinception.net/blenderSS.png http://www.digitalinception.net/gameSS.png

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  • Android Touch Event Collision Detection

    - by chrissb
    I'm relatively new to both Java and Android, so hopefully the problem I'm having is stemming from something pretty minor that I've overlooked. I've got a (very early stage) game that I've started working on, for Android using Java. At this stage, when the user touches the screen, if they touched a point at which there is an enemy, the enemies health is decreased and they become immobile (for the current implementation at least). The issue that I'm having is that the touch detection doesn't always seem to work. I've got a testing sprite set up that goes to the eventX and eventY coordinates of the touch down event, and it always seems to collide with the enemy object. Yet, the enemy doesn't always register as being hit, and sometimes a hit is registered when the sprite indicates the touch coordinates were outside of the enemies bounding box. I realise that this probably doesn't mean much without any code, so here's what I've got so far. Be gentle, as this is literally my first attempt at something more than basic movement etc. First off, the MainGamePanel class registers the touch event, and informs the levelmanager class (which is what I set up to monitor/handle enemies) public boolean onTouchEvent(MotionEvent event) { if (event.getAction() == MotionEvent.ACTION_DOWN){ levelManager.handleActionDown((int)event.getX(), (int)event.getY()); targetX=event.getX(); targetY=event.getY(); } if (event.getAction() == MotionEvent.ACTION_MOVE) { //the gestures } if (event.getAction() == MotionEvent.ACTION_UP) { //touch was released } return true; } From there, in the levelmanager class the touch event is passed on to all of the enemies within a list array: public static void handleActionDown(int eventX,int eventY){ hit=false; for (enemy1 en : enemy1array){ en.handleActionDown(eventX, eventY); } } The rest of the collision code is handled within the enemies handleActionDown function: public void handleActionDown(int eventX, int eventY) { if(eventX>this.x-enemy1bitmap.getWidth() && eventX<this.x+enemy1bitmap.getWidth() && eventY>this.y-enemy1bitmap.getHeight() && eventY<this.x+enemy1bitmap.getHeight()){ takeDamage(1); levelmanager.setHit(); } } I should probably be using getWidth()/2 and getHeight()/2 for it to be more accurate, but I expanded the area to test this - although I've noticed no improvement. At this stage, the games detection over whether or not the enemy is hit is spotty at best. Generally it takes two or three attempts before a collision is successfully registered, even though the sprite that is being used for testing and set to the eventX and eventY coordinates always indicates that the collision should have worked. Hopefully someone can steer me in the right direction here, and if more information is needed, ask away! Cheers, -Chris

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  • Help with this optimization

    - by Milo
    Here is what I do: I have bitmaps which I draw into another bitmap. The coordinates are from the center of the bitmap, thus on a 256 by 256 bitmap, an object at 0.0,0.0 would be drawn at 128,128 on the bitmap. I also found the furthest extent and made the bitmap size 2 times the extent. So if the furthest extent is 200,200 pixels, then the bitmap's size is 400,400. Unfortunately this is a bit inefficient. If a bitmap needs to be drawn at 500,500 and the other one at 300,300, then the target bitmap only needs to be 200,200 in size. I cannot seem to find a correct way to draw in the components correctly with a reduced size. I figure out the target bitmap size like this: float AvatarComposite::getFloatWidth(float& remainder) const { float widest = 0.0f; float widestNeg = 0.0f; for(size_t i = 0; i < m_components.size(); ++i) { if(m_components[i].getSprite() == NULL) { continue; } float w = m_components[i].getX() + ( ((m_components[i].getSprite()->getWidth() / 2.0f) * m_components[i].getScale()) / getWidthToFloat()); float wn = m_components[i].getX() - ( ((m_components[i].getSprite()->getWidth() / 2.0f) * m_components[i].getScale()) / getWidthToFloat()); if(w > widest) { widest = w; } if(wn > widest) { widest = wn; } if(w < widestNeg) { widestNeg = w; } if(wn < widestNeg) { widestNeg = wn; } } remainder = (2 * widest) - (widest - widestNeg); return widest - widestNeg; } And here is how I position and draw the bitmaps: int dw = m_components[i].getSprite()->getWidth() * m_components[i].getScale(); int dh = m_components[i].getSprite()->getHeight() * m_components[i].getScale(); int cx = (getWidth() + (m_remainderX * getWidthToFloat())) / 2; int cy = (getHeight() + (m_remainderY * getHeightToFloat())) / 2; cx -= m_remainderX * getWidthToFloat(); cy -= m_remainderY * getHeightToFloat(); int dx = cx + (m_components[i].getX() * getWidthToFloat()) - (dw / 2); int dy = cy + (m_components[i].getY() * getHeightToFloat()) - (dh / 2); g->drawScaledSprite(m_components[i].getSprite(),0.0f,0.0f, m_components[i].getSprite()->getWidth(),m_components[i].getSprite()->getHeight(),dx,dy, dw,dh,0); I basically store the difference between the original 2 * longest extent bitmap and the new optimized one, then I translate by that much which I would think would cause me to draw correctly but then some of the components look cut off. Any insight would help. Thanks

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  • Terrain sqaure loading

    - by AndroidXTr3meN
    Games like Skyrim, Morrowind, and more are using quads or sqaure to divide the terrain if im correct. The player is always at #5 1 | 2 | 3 4 | 5 | 6 7 | 8 | 9 So whenever you cross the border you unload and load the new "areas" But if the user goes just over the edge and then the second after goes back previous area a lot of uneccessary loading and unloading is done. Is there a general approach to this becuase I dont think games like skyrim have this issue? Cheers!

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  • Best Game Engine/Framework and Language for 2D actor/sprite intensive game

    - by Grungetastic
    I'm new to the game dev world. I have a rather large project in mind (I learn by setting myself challenges :P ) and I'm wondering what the best engine/framework/language is for a 2D game with thousands of sprites/actors on screen at a time. Bare metal type stuff. I need to still be able to zoom in and out with that many actors at once. This game will have no 3D elements. Any thoughts? Suggestions?

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  • Initializing OpenFeint for Android outside the main Application

    - by Ef Es
    I am trying to create a generic C++ bridge to use OpenFeint with Cocos2d-x, which is supposed to be just "add and run" but I am finding problems. OpenFeint is very exquisite when initializing, it requires a Context parameter that MUST be the main Application, in the onCreate method, never the constructor. Also, the main Apps name must be edited into the manifest. I am trying to fix this. So far I have tried to create a new Application that calls my Application to test if just the type is needed, but you do really need the main Android application. I also tried using a handler for a static initialization but I found pretty much the same problem. Has anybody been able to do it? This is my working-but-not-as-intended code snippet public class DerpHurr extends Application{ @Override public void onCreate() { super.onCreate(); initializeOpenFeint("TestApp", "edthedthedthedth", "aeyaetyet", "65462"); } public void initializeOpenFeint(String appname, String key, String secret, String id){ Map<String, Object> options = new HashMap<String, Object>(); options.put(OpenFeintSettings.SettingCloudStorageCompressionStrategy, OpenFeintSettings.CloudStorageCompressionStrategyDefault); OpenFeintSettings settings = new OpenFeintSettings(appname, key, secret, id, options); //RIGHT HERE OpenFeint.initialize(***this***, settings, new OpenFeintDelegate() { }); System.out.println("OpenFeint Started"); } } Manifest <application android:debuggable="true" android:label="@string/app_name" android:name=".DerpHurr">

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  • Is there any hueristic to polygonize a closed 2d-raster shape with n triangles?

    - by Arthur Wulf White
    Lets say we have a 2d image black on white that shows a closed geometric shape. Is there any (not naive brute force) algorithm that approximates that shape as closely as possible with n triangles? If you want a formal definition for as closely as possible: Approximate the shape with a polygon that when rendered into a new 2d image will match the largest number of pixels possible with the original image.

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  • Java - Tile engine changing number in array not changing texture

    - by Corey
    I draw my map from a txt file. Would I have to write to the text file to notice the changes I made? Right now it changes the number in the array but the tile texture doesn't change. Do I have to do more than just change the number in the array? public class Tiles { public Image[] tiles = new Image[5]; public int[][] map = new int[64][64]; private Image grass, dirt, fence, mound; private SpriteSheet tileSheet; public int tileWidth = 32; public int tileHeight = 32; Player player = new Player(); public void init() throws IOException, SlickException { tileSheet = new SpriteSheet("assets/tiles.png", tileWidth, tileHeight); grass = tileSheet.getSprite(0, 0); dirt = tileSheet.getSprite(7, 7); fence = tileSheet.getSprite(2, 0); mound = tileSheet.getSprite(2, 6); tiles[0] = grass; tiles[1] = dirt; tiles[2] = fence; tiles[3] = mound; int x=0, y=0; BufferedReader in = new BufferedReader(new FileReader("assets/map.dat")); String line; while ((line = in.readLine()) != null) { String[] values = line.split(","); for (String str : values) { int str_int = Integer.parseInt(str); map[x][y]=str_int; //System.out.print(map[x][y] + " "); y=y+1; } //System.out.println(""); x=x+1; y = 0; } in.close(); } public void update(GameContainer gc) { } public void render(GameContainer gc) { for(int x = 0; x < map.length; x++) { for(int y = 0; y < map.length; y ++) { int textureIndex = map[y][x]; Image texture = tiles[textureIndex]; texture.draw(x*tileWidth,y*tileHeight); } } } Mouse picking public void checkDistance(GameContainer gc) { Input input = gc.getInput(); float mouseX = input.getMouseX(); float mouseY = input.getMouseY(); double mousetileX = Math.floor((double)mouseX/tiles.tileWidth); double mousetileY = Math.floor((double)mouseY/tiles.tileHeight); double playertileX = Math.floor(playerX/tiles.tileWidth); double playertileY = Math.floor(playerY/tiles.tileHeight); double lengthX = Math.abs((float)playertileX - mousetileX); double lengthY = Math.abs((float)playertileY - mousetileY); double distance = Math.sqrt((lengthX*lengthX)+(lengthY*lengthY)); if(input.isMousePressed(Input.MOUSE_LEFT_BUTTON) && distance < 4) { System.out.println("Clicked"); if(tiles.map[(int)mousetileX][(int)mousetileY] == 1) { tiles.map[(int)mousetileX][(int)mousetileY] = 0; } } System.out.println(tiles.map[(int)mousetileX][(int)mousetileY]); }

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  • What is the correct and most efficient approach of streaming vertex data?

    - by Martijn Courteaux
    Usually, I do this in my current OpenGL ES project (for iOS): Initialization: Create two VBO's and one IndexBuffer (since I will use the same indices), same size. Create two VAO's and configure them, both bound to the same Index Buffer. Each frame: Choose a VBO/VAO couple. (Different from the previous frame, so I'm alternating.) Bind that VBO Upload new data using glBufferSubData(GL_ARRAY_BUFFER, ...). Bind the VAO Render my stuff using glDrawElements(GL_***, ...); Unbind the VAO However, someone told me to avoid uploading data (step 3) and render immediately the new data (step 5). I should avoid this, because the glDrawElements call will stall until the buffer is effectively uploaded to VRAM. So he suggested to draw all my geometry I uploaded the previous frame and upload in the current frame what will be drawn in the next frame. Thus, everything is rendered with the delay of one frame. Is this true or am I using the good approach to work with streaming vertex data? (I do know that the pipeline will stall the other way around. Ie: when you draw and immediately try to change the buffer data. But I'm not doing that, since I implemented double buffering.)

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  • Java 2D Rectangle Collision? [on hold]

    - by Andreas Elia
    I am just wanting to know of another (longer OR shorter) way of getting 100% effective collisions on a 2D plat-former. The current collision system that is in place works from coords on the level and does not always work reliably. Thank you in advance for any help/support. The current system draws a rectangle and is checking to see if any two points collide. From testing, the system can sometimes "glitch" and allow the player to collide into walls etc. Player Class http://pastebin.com/2zE8vz8R Main Class http://pastebin.com/A6Utb3ti

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  • Controlling a GameObject from another GameObject's script component

    - by OhMrBigshot
    I'm creating a game where when starting the game, a Cube is duplicated GridSize * GridSize times when the game starts. Now, after the cubes are duplicated I want to attach a variable to them, say "Flag" which is a bool, from another script component (let's say I have a Prefab that generates the cloned cubes). In short, I have something like this: CreateTiles.cs : Attached to Prefab void Start() { createMyTiles(); // a function that clones the tiles flagRandomTiles(); // a function that (what I'm trying to do) "Flags" 10 random cubes } CubeBehavior.cs : Attached to each Cube public bool hasFlag; // other stuff Now, I want flagRandomTiles() to set a Cube's hasFlag property via code, assuming I have access to them via a GameObject[] array. Here's what I've tried: Cubes[x].hasFlag = true; - No access. Making a function such as Cubes[x].setHasFlag(true) - still no access. Initializing Cubes as a CubeBehavior object array, then doing the above - GameObjects can't be converted to CubeBehaviors - I get this error when I try to assign the Cubes into the array. How do I do this?

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  • difference equations in MATLAB - why the need to switch signs?

    - by jefflovejapan
    Perhaps this is more of a math question than a MATLAB one, not really sure. I'm using MATLAB to compute an economic model - the New Hybrid ISLM model - and there's a confusing step where the author switches the sign of the solution. First, the author declares symbolic variables and sets up a system of difference equations. Note that the suffixes "a" and "2t" both mean "time t+1", "2a" means "time t+2" and "t" means "time t": %% --------------------------[2] MODEL proc-----------------------------%% % Define endogenous vars ('a' denotes t+1 values) syms y2a pi2a ya pia va y2t pi2t yt pit vt ; % Monetary policy rule ia = q1*ya+q2*pia; % ia = q1*(ya-yt)+q2*pia; %%option speed limit policy % Model equations IS = rho*y2a+(1-rho)yt-sigma(ia-pi2a)-ya; AS = beta*pi2a+(1-beta)*pit+alpha*ya-pia+va; dum1 = ya-y2t; dum2 = pia-pi2t; MPs = phi*vt-va; optcon = [IS ; AS ; dum1 ; dum2; MPs]; He then computes the matrix A: %% ------------------ [3] Linearization proc ------------------------%% % Differentiation xx = [y2a pi2a ya pia va y2t pi2t yt pit vt] ; % define vars jopt = jacobian(optcon,xx); % Define Linear Coefficients coef = eval(jopt); B = [ -coef(:,1:5) ] ; C = [ coef(:,6:10) ] ; % B[c(t+1) l(t+1) k(t+1) z(t+1)] = C[c(t) l(t) k(t) z(t)] A = inv(C)*B ; %(Linearized reduced form ) As far as I understand, this A is the solution to the system. It's the matrix that turns time t+1 and t+2 variables into t and t+1 variables (it's a forward-looking model). My question is essentially why is it necessary to reverse the signs of all the partial derivatives in B in order to get this solution? I'm talking about this step: B = [ -coef(:,1:5) ] ; Reversing the sign here obviously reverses the sign of every component of A, but I don't have a clear understanding of why it's necessary. My apologies if the question is unclear or if this isn't the best place to ask.

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  • How do I implement collision detection with a sprite walking up a rocky-terrain hill?

    - by detectivecalcite
    I'm working in SDL and have bounding rectangles for collisions set up for each frame of the sprite's animation. However, I recently stumbled upon the issue of putting together collisions for characters walking up and down hills/slopes with irregularly curved or rocky terrain - what's a good way to do collisions for that type of situation? Per-pixel? Loading up the points of the incline and doing player-line collision checking? Should I use bounding rectangles in general or circle collision detection?

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  • Pixel alignment algorithm

    - by user42325
    I have a set of square blocks, I want to draw them in a window. I am sure the coordinates calculation is correct. But on the screen, some squares' edge overlap with other, some are not. I remember the problem is caused by accuracy of pixels. I remember there's a specific topic related to this kind of problem in 2D image rendering. But I don't remember what exactly it is, and how to solve it. Look at this screenshot. Each block should have a fixed width margin. But in the image, the vertical white line have different width.Though, the horizontal lines looks fine.

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  • Can't read .cso files but I can read their .hlsl versions?

    - by Jader J Rivera
    Well I've been trying to read a .cso file to use as a shader for a DirectX program I'm currently making. Problem is no matter how I implemented a way to read the file it never worked. And after fidgeting around I discover that it's only the .cso files I can't read. I can read anything else (which means it works) even their .hlsl files. Which is strange because the .hlsl (high level shader language) files are supposed to turn into .cso (compiled shader object) files. What I'm currently doing is: vector<byte> Read(string File){ vector<byte> Text; fstream file(File, ios::in | ios::ate | ios::binary); if(file.is_open()){ Text.resize(file.tellg()); file.seekg(0 , ios::beg); file.read(reinterpret_cast<char*>(&Text[0]), Text.size()); file.close(); } return Text; }; If I then implement it. Read("VertexShader.hlsl"); //Works Read("VertexShader.cso"); //Doesn't Works?!?! And I need the .cso version of the shader to draw my sexy triangles. Without it my life and application will never continue and I have no idea what could be wrong. (I've also asked this at stack overflow but still no answers.)

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  • Bitmap to Texture2D problem with colors

    - by xnaNewbie89
    I have a small problem with converting a bitmap to a Texture2D. The resulted image of the conversion has the red channel switched with the blue channel :/ I don't know why, because the pixel formats are the same. If someone can help me I will be very happy :) System.Drawing.Image image = System.Drawing.Bitmap.FromFile(ImageFileLoader.filename); System.Drawing.Bitmap bitmap = new System.Drawing.Bitmap(image); Texture2D mapTexture = new Texture2D(Screen.Game.GraphicsDevice, bitmap.Width, bitmap.Height,false,SurfaceFormat.Color); System.Drawing.Imaging.BitmapData data = bitmap.LockBits(new System.Drawing.Rectangle( 0, 0, bitmap.Width, bitmap.Height), System.Drawing.Imaging.ImageLockMode.ReadOnly,System.Drawing.Imaging.PixelFormat.Format32bppArgb); byte[] bytes = new byte[data.Height * data.Width*4]; System.Runtime.InteropServices.Marshal.Copy(data.Scan0, bytes, 0, bytes.Length); mapTexture.SetData<byte>(bytes, 0, data.Height * data.Width * 4); bitmap.UnlockBits(data); bitmap.Dispose(); image.Dispose();

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  • What's a good entity hierarchy for a 2D game?

    - by futlib
    I'm in the process of building a new 2D game out of some code I wrote a while ago. The object hierarchy for entities is like this: Scene (e.g. MainMenu): Contains multiple entities and delegates update()/draw() to each Entity: Base class for all things in a scene (e.g. MenuItem or Alien) Sprite: Base class for all entities that just draw a texture, i.e. don't have their own drawing logic Does it make sense to split up entities and sprites up like that? I think in a 2D game, the terms entity and sprite are somewhat synonymous, right? But I do believe that I need some base class for entities that just draw a texture, as opposed to drawing themselves, to avoid duplication. Most entities are like that. One weird case is my Text class: It derives from Sprite, which accepts either the path of an image or an already loaded texture in its constructor. Text loads a texture in its constructor and passes that to Sprite. Can you outline a design that makes more sense? Or point me to a good object-oriented reference code base for a 2D game? I could only find 3D engine code bases of decent code quality, e.g. Doom 3 and HPL1Engine.

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  • how to retain the animated position in opengl es 2.0

    - by Arun AC
    I am doing frame based animation for 300 frames in opengl es 2.0 I want a rectangle to translate by +200 pixels in X axis and also scaled up by double (2 units) in the first 100 frames Then, the animated rectangle has to stay there for the next 100 frames. Then, I want the same animated rectangle to translate by +200 pixels in X axis and also scaled down by half (0.5 units) in the last 100 frames. I am using simple linear interpolation to calculate the delta-animation value for each frame. Pseudo code: The below drawFrame() is executed for 300 times (300 frames) in a loop. float RectMVMatrix[4][4] = {1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1 }; // identity matrix int totalframes = 300; float translate-delta; // interpolated translation value for each frame float scale-delta; // interpolated scale value for each frame // The usual code for draw is: void drawFrame(int iCurrentFrame) { // mySetIdentity(RectMVMatrix); // comment this line to retain the animated position. mytranslate(RectMVMatrix, translate-delta, X_AXIS); // to translate the mv matrix in x axis by translate-delta value myscale(RectMVMatrix, scale-delta); // to scale the mv matrix by scale-delta value ... // opengl calls glDrawArrays(...); eglswapbuffers(...); } The above code will work fine for first 100 frames. in order to retain the animated rectangle during the frames 101 to 200, i removed the "mySetIdentity(RectMVMatrix);" in the above drawFrame(). Now on entering the drawFrame() for the 2nd frame, the RectMVMatrix will have the animated value of first frame e.g. RectMVMatrix[4][4] = { 1.01, 0, 0, 2, 0, 1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1 };// 2 pixels translation and 1.01 units scaling after first frame This RectMVMatrix is used for mytranslate() in 2nd frame. The translate function will affect the value of "RectMVMatrix[0][0]". Thus translation affects the scaling values also. Eventually output is getting wrong. How to retain the animated position without affecting the current ModelView matrix? =========================================== I got the solution... Thanks to Sergio. I created separate matrices for translation and scaling. e.g.CurrentTranslateMatrix[4][4], CurrentScaleMatrix[4][4]. Then for every frame, I reset 'CurrentTranslateMatrix' to identity and call mytranslate( CurrentTranslateMatrix, translate-delta, X_AXIS) function. I reset 'CurrentScaleMatrix' to identity and call myscale(CurrentScaleMatrix, scale-delta) function. Then, I multiplied these 'CurrentTranslateMatrix' and 'CurrentScaleMatrix' to get the final 'RectMVMatrix' Matrix for the frame. Pseudo Code: float RectMVMatrix[4][4] = {0}; float CurrentTranslateMatrix[4][4] = {0}; float CurrentScaleMatrix[4][4] = {0}; int iTotalFrames = 300; int iAnimationFrames = 100; int iTranslate_X = 200.0f; // in pixels float fScale_X = 2.0f; float scaleDelta; float translateDelta_X; void DrawRect(int iTotalFrames) { mySetIdentity(RectMVMatrix); for (int i = 0; i< iTotalFrames; i++) { DrawFrame(int iCurrentFrame); } } void getInterpolatedValue(int iStartFrame, int iEndFrame, int iTotalFrame, int iCurrentFrame, float *scaleDelta, float *translateDelta_X) { float fDelta = float ( (iCurrentFrame - iStartFrame) / (iEndFrame - iStartFrame)) float fStartX = 0.0f; float fEndX = ConvertPixelsToOpenGLUnit(iTranslate_X); *translateDelta_X = fStartX + fDelta * (fEndX - fStartX); float fStartScaleX = 1.0f; float fEndScaleX = fScale_X; *scaleDelta = fStartScaleX + fDelta * (fEndScaleX - fStartScaleX); } void DrawFrame(int iCurrentFrame) { getInterpolatedValue(0, iAnimationFrames, iTotalFrames, iCurrentFrame, &scaleDelta, &translateDelta_X) mySetIdentity(CurrentTranslateMatrix); myTranslate(RectMVMatrix, translateDelta_X, X_AXIS); // to translate the mv matrix in x axis by translate-delta value mySetIdentity(CurrentScaleMatrix); myScale(RectMVMatrix, scaleDelta); // to scale the mv matrix by scale-delta value myMultiplyMatrix(RectMVMatrix, CurrentTranslateMatrix, CurrentScaleMatrix);// RectMVMatrix = CurrentTranslateMatrix*CurrentScaleMatrix; ... // opengl calls glDrawArrays(...); eglswapbuffers(...); } I maintained this 'RectMVMatrix' value, if there is no animation for the current frame (e.g. 101th frame onwards). Thanks, Arun AC

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  • Solving 2D Collision Detection Issues with Relative Velocities

    - by Jengerer
    Imagine you have a situation where two objects are moving parallel to one-another and are both within range to collide with a static wall, like this: A common method used in dynamic collision detection is to loop through all objects in arbitrary order, solve for pair-wise collision detection using relative velocities, and then move the object to the nearest collision, if any. However, in this case, if the red object is checked first against the blue one, it would see that the relative velocity to the blue object is -20 m/s (and would thereby not collide this time frame). Then it would see that the red object would collide with the static wall, and the solution would be: And the red object passes through the blue one. So it appears to be a matter of choosing the right order in which you check collisions; but how can you determine which order is correct? How can this passing through of objects be avoided? Is ignoring relative velocity and considering every object as static during pair-wise checks a better idea for this reason?

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