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  • How can I pass an external instance to the constructor of an object that's being created using the default XNA XML content loader?

    - by Michael
    I'm trying to understand how to use the XNA XML content importer to instantiate non-trivial objects that are more than a collection of basic properties (e.g., a class that inherits from DrawableGameObject or GameObject and requires other things to be passed into its constructor). Is it possible to pass existing external instances (e.g., an instance of the current Game) to the constructor of an object that's being created using the default XNA XML content loader? For example, imagine that I have the following class, inheriting from DrawableGameComponent: public class Character : DrawableGameComponent { public string Name { get; set; } public Character(Game game) : base(game) { } public override void Update(GameTime gameTime) { } public override void Draw(GameTime gameTime) { } } If I had a simple class that did not need other parameters in its constructor (i.e., the Game instance), then I could simply use this XML: <XnaContent> <Asset Type="MyNamespace.Character"> <Name>John Doe</Name> </Asset> </XnaContent> ...and then create an instance of Character using this code: var character = Content.Load<Character>("MyXmlAssetName"); But that won't work because I need to pass the need to pass the Game into the constructor. What's the best way to handle this situation? Is there a way to pass in things like the current Game using the default XNA XML content loader? Do I need to write my own XML loader? (If so, how?) Is there a better object-oriented design that I should be using for my classes? Note: Although I used Game in this example, I'm really just asking how to pass any type of existing instance to my constructors. (For example, I'm using the Farseer Physics Engine, and some of my classes also need a reference to the Farseer World object too.) Thanks in advance.

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  • Trouble using Ray.Intersect method on bounding boxes in a 2D XNA game

    - by getsauce
    I am trying to use a ray and bounding box to determine if a box is between the player and the mouse pointer in 2D space. When I try testing the code, the collision will return true when pointed at the box but it also returns true under other circumstances where it shouldn't. For instance. If I have a player on the left and a box directly to the right, I can put the mouse pointer a few hundred pixels above the box or a few hundred below and it will still return true. Also, I can put my mouse pointer to the left of the player and in a certain area it will still return true. Does anyone have any idea what might cause this? I have left out definitions for some of my members and properties just to make this code sample easier to read. The position property is just a Vector2 for where each object is located. ray = new Ray(new Vector3(player.Position, 0), new Vector3(mouse.Position, 0); box = new BoundingBox(new Vector3(box.Position, 0), new Vector3( new Vector2(box.Position + box.Width, box.Position + box.Height), 0); if (ray.Intersects(box) != null) collision = true; else collision = false;

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  • Alternatives to multiple sprite batches for achieving 2D particle system depth

    - by Ergwun
    In my 2D XNA game, I render all my sprites with a single sprite batch using SpriteSortMode.BackToFront and BlendState.AlphaBlend. I'm adding a particle system based on the App Hub particles sample. Since this uses SpriteSortMode.Deferred and BlendState.Additive, I will need to have two SpriteBatch.Begin / SpriteBatch.End pairs: one for 'regular' sprites, and one for particles. In my top-down shooter, If I want to have explosions appear under planes, but above the ground, then I believe I will have to have three Begin/End pairs, first to draw everything under the explosions, then to draw the explosions, then to draw everything above the explosions. If I want to have particle effects at multiple different depths, then I'm going to need even more Begin/Endpairs. This is all easy to code, but I'm wondering if there is an alternative way to handle this?

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  • converting 2d grid of squares to polygon nav mesh

    - by Roflha
    I haven't actually started programming for this one yet, but I wanted to see how I would go about doing this anyway. Say I have a 2D matrix of squares, all of the same size, some traversable and some not. How would I go about creating a navigation mesh of polygons from this grid. Is there any reading I can look at until I get a chance to get to my computer or should I just give it a go. My idea was to take the non-traversable squares out and extend lines from there edges to make polygons.. that's all I have got so far. Any advice?

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  • Per-pixel collision detection - why does XNA transform matrix return NaN when adding scaling?

    - by JasperS
    I looked at the TransformCollision sample on MSDN and added the Matrix.CreateTranslation part to a property in my collision detection code but I wanted to add scaling. The code works fine when I leave scaling commented out but when I add it and then do a Matrix.Invert() on the created translation matrix the result is NaN ({NaN,NaN,NaN},{NaN,NaN,NaN},...) Can anyone tell me why this is happening please? Here's the code from the sample: // Build the block's transform Matrix blockTransform = Matrix.CreateTranslation(new Vector3(-blockOrigin, 0.0f)) * // Matrix.CreateScale(block.Scale) * would go here Matrix.CreateRotationZ(blocks[i].Rotation) * Matrix.CreateTranslation(new Vector3(blocks[i].Position, 0.0f)); public static bool IntersectPixels( Matrix transformA, int widthA, int heightA, Color[] dataA, Matrix transformB, int widthB, int heightB, Color[] dataB) { // Calculate a matrix which transforms from A's local space into // world space and then into B's local space Matrix transformAToB = transformA * Matrix.Invert(transformB); // When a point moves in A's local space, it moves in B's local space with a // fixed direction and distance proportional to the movement in A. // This algorithm steps through A one pixel at a time along A's X and Y axes // Calculate the analogous steps in B: Vector2 stepX = Vector2.TransformNormal(Vector2.UnitX, transformAToB); Vector2 stepY = Vector2.TransformNormal(Vector2.UnitY, transformAToB); // Calculate the top left corner of A in B's local space // This variable will be reused to keep track of the start of each row Vector2 yPosInB = Vector2.Transform(Vector2.Zero, transformAToB); // For each row of pixels in A for (int yA = 0; yA < heightA; yA++) { // Start at the beginning of the row Vector2 posInB = yPosInB; // For each pixel in this row for (int xA = 0; xA < widthA; xA++) { // Round to the nearest pixel int xB = (int)Math.Round(posInB.X); int yB = (int)Math.Round(posInB.Y); // If the pixel lies within the bounds of B if (0 <= xB && xB < widthB && 0 <= yB && yB < heightB) { // Get the colors of the overlapping pixels Color colorA = dataA[xA + yA * widthA]; Color colorB = dataB[xB + yB * widthB]; // If both pixels are not completely transparent, if (colorA.A != 0 && colorB.A != 0) { // then an intersection has been found return true; } } // Move to the next pixel in the row posInB += stepX; } // Move to the next row yPosInB += stepY; } // No intersection found return false; }

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  • How much to pay for artwork in an indie game?

    - by f20k
    I am an indie developer and I need some detailed artwork. How much is reasonable to pay an artist for say 20 character designs? I know it depends on the artist's skills, etc, but I am wondering what to expect so that I can budget it. Edit: Let's say cartoon-ish art (Example - not necessarily in that level of detail but that kind of cartoony-art style). No 3-d modelling - The art will be used as still images in game and for promotional reasons. I'd provide a base sprite design for them to expand on and detail. Also, some numbers would be nice - I like numbers. Even a range is helpful. Like: expect to spend $x2 ~ $x1 for top-notch and $y2 ~ $y1 for decent quality. I understand I can ask at some indie-help site but, if an artist says something like $1000 for 20 designs, I wouldn't have any idea if it's reasonable / good deal / bad idea etc.

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  • libgdx collision detection / bounding the object

    - by johnny-b
    i am trying to get collision detection so i am drawing a red rectangle to see if it is working, and when i do the code below in the update method. to check if it is going to work. the position is not in the right place. the red rectangle starts from the middle and not at the x and y point?Huh so it draws it wrong. i also have a getter method so nothing wrong there. bullet.set(getX(), getY(), getOriginX(), getOriginY()); this is for the render shapeRenderer.begin(ShapeType.Filled); shapeRenderer.setColor(Color.RED); shapeRenderer.rect(bullet.getX(), bullet.getY(), bullet.getOriginX(), bullet.getOriginY(), 15, 5, bullet.getRotation()); shapeRenderer.end(); i have tried to do it with a circle but the circle draws in the middle and i want it to be at the tip of the bullet. at the front of the bullet. x, y point. boundingCircle.set(getX() + getOriginX(), getY() + getOriginY(), 4.0f); shapeRenderer.begin(ShapeType.Filled); shapeRenderer.setColor(Color.RED); shapeRenderer.circle(bullet.getBoundingCircle().x, bullet.getBoundingCircle().y, bullet.getBoundingCircle().radius); shapeRenderer.end(); thank you need it to be of the x and y as the bullet is in the middle of the sprite when drawn originally via paint.

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  • Can I use copyrighted images and music in my game? [duplicate]

    - by Aman Grover
    This question already has an answer here: Using modified copyrighted music in non-commercial games 3 answers I am working on my first ever project , and I have used some copyrighted images(images taken from some other well recognized games). Is it even possible that I edit the images a little bit and then use them as royalty free images? If not, then can anyone tell me some web links from where I can get royalty free images?

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  • Many sources of movement in an entity system

    - by Sticky
    I'm fairly new to the idea of entity systems, having read a bunch of stuff (most usefully, this great blog and this answer). Though I'm having a little trouble understanding how something as simple as being able to manipualate the position of an object by an undefined number of sources. That is, I have my entity, which has a position component. I then have some event in the game which tells this entity to move a given distance, in a given time. These events can happen at any time, and will have different values for position and time. The result is that they'd be compounded together. In a traditional OO solution, I'd have some sort of MoveBy class, that contains the distance/time, and an array of those inside my game object class. Each frame, I'd iterate through all the MoveBy, and apply it to the position. If a MoveBy has reached its finish time, remove it from the array. With the entity system, I'm a little confused as how I should replicate this sort of behavior. If there were just one of these at a time, instead of being able to compound them together, it'd be fairly straightforward (I believe) and look something like this: PositionComponent containing x, y MoveByComponent containing x, y, time Entity which has both a PositionComponent and a MoveByComponent MoveBySystem that looks for an entity with both these components, and adds the value of MoveByComponent to the PositionComponent. When the time is reached, it removes the component from that entity. I'm a bit confused as to how I'd do the same thing with many move by's. My initial thoughts are that I would have: PositionComponent, MoveByComponent the same as above MoveByCollectionComponent which contains an array of MoveByComponents MoveByCollectionSystem that looks for an entity with a PositionComponent and a MoveByCollectionComponent, iterating through the MoveByComponents inside it, applying/removing as necessary. I guess this is a more general problem, of having many of the same component, and wanting a corresponding system to act on each one. My entities contain their components inside a hash of component type - component, so strictly have only 1 component of a particular type per entity. Is this the right way to be looking at this? Should an entity only ever have one component of a given type at all times?

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  • Updating sprite location with controls

    - by iQue
    So ive got a character in a 2D game using surfaceView that I want to be able to move using a button(eventually a joystick), but my game crashes as soon as I try to move my sprite. This is my onTouch-method for my steering button: public void handleActionDown(int eventX, int eventY) { if (eventX >= (x - bitmap.getWidth() / 2) && (eventX <= (x + bitmap.getWidth()/2))) { if (eventY >= (y - bitmap.getHeight() / 2) && (y <= (y + bitmap.getHeight() / 2))) { setTouched(true); } else { setTouched(false); } } else { setTouched(false); } and if I try to put this in my update-method: public void update() { x += (speed.getXv() * speed.getxDirection()); y += (speed.getYv() * speed.getyDirection()); } the sprite moves on its own just fine, but as soon as I add: public void update() { if(steering.isTouched()){ x += (speed.getXv() * speed.getxDirection()); y += (speed.getYv() * speed.getyDirection()); } the game crashes. Does any1 know why this is or how to fix it? I cannot figure it out. Im using MotionEvent.ACTION_DOWN to check if the user if pressing the screen. }

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  • proper way to creation multiple similiar buttons/panels

    - by JayAvon
    I have the below Code which i tried to do, but it only shows(the minus/plus button) on the last GirdLayout (Intelligence stat): JButton plusButton = new JButton("+"); JButton minusButton = new JButton("-"); statStrengthGridPanel = new JPanel(new GridLayout(1,3)); statStrengthGridPanel.add(minusButton); statStrengthGridPanel.add(new JLabel("10")); statStrengthGridPanel.add(plusButton); statConstitutionGridPanel = new JPanel(new GridLayout(1,3)); statConstitutionGridPanel.add(minusButton); statConstitutionGridPanel.add(new JLabel("10")); statConstitutionGridPanel.add(plusButton); statDexterityGridPanel = new JPanel(new GridLayout(1,3)); statDexterityGridPanel.add(minusButton); statDexterityGridPanel.add(new JLabel("10")); statDexterityGridPanel.add(plusButton); statIntelligenceGridPanel = new JPanel(new GridLayout(1,3)); statIntelligenceGridPanel.add(minusButton); statIntelligenceGridPanel.add(new JLabel("10")); statIntelligenceGridPanel.add(plusButton); I know I can do something like I did for the Panel names(have multiple ones), but I did not want to do that for the Panels in the first place. I am trying to use best practice and not have my code be repetitive. Any suggestions?? The goal is to have 4 stats, to assign points to, with decrement and increment buttons(I decided against sliders). Eventually I will have them have upper and lower limits, decrement the "unused" label, and all of that good stuff, but I just want to not be repetitive. Thanks for any help.

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  • XNA - Use Mouse To Rotate & Arrow Keys To Scroll A Linearly Wrapped Texture:

    - by The Thing
    Using XNA I'm working on my first, relatively simple, videogame for the PC. At the moment my game window is 1024 X 768 and I have a 'Starfield' linearly wrapped background texture 1280 X 1280 in size whose origin has been set to its center point (width / 2, height / 2). This texture is drawn onscreen using (graphics.PreferredBackBufferWidth / 2, graphics.PreferredBackBufferHeight / 2) to place the origin in the center of the window. I want to be able to use the horizontal movement of the mouse to rotate my texture left or right and use the arrow keys to scroll the texture in four directions. From my own related coding experiments I have found that once I rotate the texture it no longer scrolls in the direction I want, it's as if somehow the XNA framework's 'sense of direction' has been 'rotated' along with the texture. As an example of what I've described above lets say I rotate the texture 45 degrees to the right, then pressing the up arrow key results in the texture scrolling diagonally from top-right to bottom-left. This is not what I want, regardless of the degree or direction of rotation I want my texture to scroll straight up, straight down, or to the left or right depending on which arrow key was pressed. How do I go about accomplishing this? Any help or guidance is appreciated. To finish up there are two points I'd like to clarify: [1] The reason I'm using linear wrapping on my starfield texture is that it gives a nice impression of an endless starfield. [2] Using a texture at least 1280 X 1280 in conjunction with a game window of 1024 X 768 means that at no point in it's rotation will the edges of the texture become visible. Thanks for reading..... Update # 1 - as requested by RCIX: The code below is what I was referring to earlier when I mentioned 'related coding experiments'. As you can see I am scrolling a linearly wrapped texture in the direction I've moved the mouse relative to the center of the screen. This works perfectly if I don't rotate the texture, but once I do rotate it the direction of the scrolling gets messed up for some reason. public class Game1 : Microsoft.Xna.Framework.Game { GraphicsDeviceManager graphics; SpriteBatch spriteBatch; int x; int y; float z = 250f; Texture2D Overlay; Texture2D RotatingBackground; Rectangle? sourceRectangle; Color color; float rotation; Vector2 ScreenCenter; Vector2 Origin; Vector2 scale; Vector2 Direction; SpriteEffects effects; float layerDepth; public Game1() { graphics = new GraphicsDeviceManager(this); Content.RootDirectory = "Content"; } protected override void Initialize() { graphics.PreferredBackBufferWidth = 1024; graphics.PreferredBackBufferHeight = 768; graphics.ApplyChanges(); Direction = Vector2.Zero; IsMouseVisible = true; ScreenCenter = new Vector2(graphics.PreferredBackBufferWidth / 2, graphics.PreferredBackBufferHeight / 2); Mouse.SetPosition((int)graphics.PreferredBackBufferWidth / 2, (int)graphics.PreferredBackBufferHeight / 2); sourceRectangle = null; color = Color.White; rotation = 0.0f; scale = new Vector2(1.0f, 1.0f); effects = SpriteEffects.None; layerDepth = 1.0f; base.Initialize(); } protected override void LoadContent() { spriteBatch = new SpriteBatch(GraphicsDevice); Overlay = Content.Load<Texture2D>("Overlay"); RotatingBackground = Content.Load<Texture2D>("Background"); Origin = new Vector2((int)RotatingBackground.Width / 2, (int)RotatingBackground.Height / 2); } protected override void UnloadContent() { } protected override void Update(GameTime gameTime) { float timePassed = (float)gameTime.ElapsedGameTime.TotalSeconds; MouseState ms = Mouse.GetState(); Vector2 MousePosition = new Vector2(ms.X, ms.Y); Direction = ScreenCenter - MousePosition; if (Direction != Vector2.Zero) { Direction.Normalize(); } x += (int)(Direction.X * z * timePassed); y += (int)(Direction.Y * z * timePassed); //No rotation = texture scrolls as intended, With rotation = texture no longer scrolls in the direction of the mouse. My update method needs to somehow compensate for this. //rotation += 0.01f; base.Update(gameTime); } protected override void Draw(GameTime gameTime) { spriteBatch.Begin(SpriteSortMode.Deferred, null, SamplerState.LinearWrap, null, null); spriteBatch.Draw(RotatingBackground, ScreenCenter, new Rectangle(x, y, RotatingBackground.Width, RotatingBackground.Height), color, rotation, Origin, scale, effects, layerDepth); spriteBatch.Draw(Overlay, Vector2.Zero, Color.White); spriteBatch.End(); base.Draw(gameTime); } }

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  • Best way to go for simple online multi-player games?

    - by Mr_CryptoPrime
    I want to create a trivia game for my website. The graphic design does not have to be too fancy, probably no more advanced than a typical flash game. It needs to be secure because I want users to be able to play for real money. It also needs to run fast so users don't spend their time frustrated with game freezing. Compatibility, as with almost all online products, is key because of the large target market. I am most acquainted with Java programming, but I don't want to do it in Java if there is something much better. I am assuming I will have to utilize a variety of different languages in order for everything to come together. If someone could point out the main structure of everything so I could get a good start that would be great! 1) Language choice for simple secure online multiplayer games? 2) Perhaps use a database like MySQL, stored on a secure server for the trivia questions? 3) Free educational resources and even simpler projects to practice? Any ideas or suggestions would be helpful...Thanks!

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  • Frame Buffer Objects vs calling TexCoord2f?

    - by sensae
    I'm learning the basics of OpenGL with lwjgl currently, and following a guide I've got textured quads that can move around a scene. I've been reading about Frame Buffer Objects, and I'm not really clear on their purpose and their benefit. My understanding is that I'll create a FBO with the texture I'd like, load the FBO, draw a quad, then unload the FBO. What would the technique I'm currently doing for texture management be called, and how does it differ from using FBOs? What are the benefits to using FBOs? How does it fit into the grand rendering scheme of things?

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  • Well-tested libraries for player ratings?

    - by Lucky
    It's common in games to implement some sort of numerical ranking system -- the ELO system is usually used in chess. I could implement this system naively using Wikipedia's descriptions, but I suspect that this would open up a whole box of problems that have already been solved: rating inflation, etc -- for instance, the ELO system has a K constant that's 'fudged' according to rating, duration, pairings, statistics, ... What are some libraries (I'm looking at Python, but anything is okay) that implements rating systems? It also doesn't have to be ELO.

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  • What should I worry about when changing OpenGL origin to upper left of screen?

    - by derivative
    For self education, I'm writing a 2D platformer engine in C++ using SDL / OpenGL. I initially began with pure SDL using the tutorials on sdltutorials.com and lazyfoo.net, but I'm now rendering in an OpenGL context (specifically immediate mode but I'm learning about VAOs/VBOs) and using SDL for interface, audio, etc. SDL uses a coordinate system with the origin in the upper left of the screen and the positive y-axis pointing down. It's easy to set up my orthographic projection in OpenGL to mirror this. I know that texture coordinates are a right-hand system with values from 0 to 1 -- flipping the texture vertically before rendering (well, flip the file before loading) yields textures that render correctly... which is fine if I'm drawing the entire texture, but ultimately I'll be using tilesets and can imagine problems. What should I be concerned about in terms of rendering when I do this? If anybody has any advice or they've done this themselves and can point out future pitfalls, that would be great, but really any thoughts would be appreciated.

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  • Fast determination of whether objects are onscreen in 2D

    - by Ben Ezard
    So currently, I have this in each object's renderer's update method: float a = transform.position.x * Main.scale; float b = transform.position.y * Main.scale; float c = Camera.main.transform.position.x * Main.scale; float d = Camera.main.transform.position.y * Main.scale; onscreen = a + width - c > 0 && a - c < GameView.width && b + height - d > 0 && b - d < GameView.height; transform.position is a 2D vector containing the game engine's definition of where the object is - this is then multiplied by Main.scale to translate that coordinate into actual screen space Similarly, Camera.main.transform.position is the in-engine representation of where the main camera is, and this is also multiplied by Main.scale The problem is, as my game is tile-based, thousands of these updates get called every frame, just to determine whether or not each object should be drawn - how can I improve this please?

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  • C++: Checking if an object faces a point (within a certain range)

    - by bojoradarial
    I have been working on a shooter game in C++, and am trying to add a feature whereby missiles shot must be within 90 degrees (PI/2 radians) of the direction the ship is facing. The missiles will be shot towards the mouse. My idea is that the ship's angle of rotation is compared with the angle between the ship and the mouse (std::atan2(mouseY - shipY, mouseX - shipX)), and if the difference is less than PI/4 (45 degrees) then the missile can be fired. However, I can't seem to get this to work. The ship's angle of rotation is increased and decreased with the A and D keys, so it is possible that it isn't between 0 and 2*PI, hence the use of fmod() below. Code: float userRotation = std::fmod(user->Angle(), 6.28318f); if (std::abs(userRotation - missileAngle) > 0.78f) return; Any help would be appreciated. Thanks!

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  • Knowing state of game in real time

    - by evthim
    I'm trying to code a tic tac toe game in java and I need help figuring out how to efficiently and without freezing the program check if someone won the game. I'm only in the design stages now, I haven't started programming anything but I'm wondering how would I know at all times the state of the game and exactly when someone wins? Response to MarkR: (note: had to place comment here, it was too long for comment section) It's not a homework problem, I'm trying to get more practice programming GUI's which I've only done once as a freshman in my second introductory programming course. I understand I'll have a 2D array. I plan to have a 2D integer array where x would equal 1 and o would equal 0. However, won't it take too much time if I check after every move if someone won the game? Is there a way or a data structure or algorithm I can use so that the program will know the state (when I say state I mean not just knowing every position on the board, the int array will take care of that, I mean knowing that user 1 will win if he places x on this block) of the game at all times and thus can know automatically when someone won?

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  • Random Position between ranges.

    - by blakey87
    Does anyone have a good algorithm for generating a random y position for spawning a block, which takes into account a minimum and maximum height, allowing player to to jump on the block. Blocks will continually be spawned, so the player must always be able to jump onto the next block, bearing in mind the minimum position which would be the ground, and the maximum which would the players jump height bearing in mind the ceiling

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  • How should I load level data in java?

    - by Matthew G.
    I'm setting up my engine for a certain action/arcade game to have a set of commands that would look something like this. Set landscape to grass Create rocks at ... Create player at X, Y Set goal to "Get to point X Y" Spawn enemy at X, Y I'd then have each object knowing what it has to do, and acting on its own. I've been thinking about how to store this data. External data files could be parsed by a level class, and certain objects can be spawned through that. I could also create a base level class and extend it for each level, but that'd create a large amount of classes. Another idea is to have one level parser class, but have a case for each level. This would be extremely silly and bulky, but I mention it because I found that I did this at 2 AM last night. I'm finally getting why I have to plan out my inheritances, though. RIP project. I might be completely missing another option.

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  • How to track many in-game statistics

    - by Alex Schearer
    I am looking to track many in-game events, e.g. the score of each move, how many moves are taken, what types of moves, etc. A lot of stats can simply be tracked with a counter. In some cases I need to aggregate data in order to calculate the value (e.g. most common move). How are you tracking in-game stats for your games? How do you avoid creating a class with tens or hundreds of fields? How do you avoid littering the code with tracking invocations? How do you abstract the aggregate data so as to avoid rewriting it for each scenario?

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  • How to shift a vector based on the rotation of another vector?

    - by bpierre
    I’m learning 2D programming, so excuse my approximations, and please, don’t hesitate to correct me. I am just trying to fire a bullet from a player. I’m using HTML canvas (top left origin). Here is a representation of my problem: The black vector represent the position of the player (the grey square). The green vector represent its direction. The red disc represents the target. The red vector represents the direction of a bullet, which will move in the direction of the target (red and dotted line). The blue cross represents the point from where I really want to fire the bullet (and the blue and dotted line represents its movement). This is how I draw the player (this is the player object. Position, direction and dimensions are 2D vectors): ctx.save(); ctx.translate(this.position.x, this.position.y); ctx.rotate(this.direction.getAngle()); ctx.drawImage(this.image, Math.round(-this.dimensions.x/2), Math.round(-this.dimensions.y/2), this.dimensions.x, this.dimensions.y); ctx.restore(); This is how I instanciate a new bullet: var bulletPosition = playerPosition.clone(); // Copy of the player position var bulletDirection = Vector2D.substract(targetPosition, playerPosition).normalize(); // Difference between the player and the target, normalized new Bullet(bulletPosition, bulletDirection); This is how I move the bullet (this is the bullet object): var speed = 5; this.position.add(Vector2D.multiply(this.direction, speed)); And this is how I draw the bullet (this is the bullet object): ctx.save(); ctx.translate(this.position.x, this.position.y); ctx.rotate(this.direction.getAngle()); ctx.fillRect(0, 0, 3, 3); ctx.restore(); How can I change the direction and position vectors of the bullet to ensure it is on the blue dotted line? I think I should represent the shift with a vector, but I can’t see how to use it.

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  • Triangle Picking Picking Back faces

    - by Tangeleno
    I'm having a bit of trouble with 3D picking, at first I thought my ray was inaccurate but it turns out that the picking is happening on faces facing the camera and faces facing away from the camera which I'm currently culling. Here's my ray creation code, I'm pretty sure the problem isn't here but I've been wrong before. private uint Pick() { Ray cursorRay = CalculateCursorRay(); Vector3? point = Control.Mesh.RayCast(cursorRay); if (point != null) { Tile hitTile = Control.TileMesh.GetTileAtPoint(point); return hitTile == null ? uint.MaxValue : (uint)(hitTile.X + hitTile.Y * Control.Generator.TilesWide); } return uint.MaxValue; } private Ray CalculateCursorRay() { Vector3 nearPoint = Control.Camera.Unproject(new Vector3(Cursor.Position.X, Control.ClientRectangle.Height - Cursor.Position.Y, 0f)); Vector3 farPoint = Control.Camera.Unproject(new Vector3(Cursor.Position.X, Control.ClientRectangle.Height - Cursor.Position.Y, 1f)); Vector3 direction = farPoint - nearPoint; direction.Normalize(); return new Ray(nearPoint, direction); } public Vector3 Camera.Unproject(Vector3 source) { Vector4 result; result.X = (source.X - _control.ClientRectangle.X) * 2 / _control.ClientRectangle.Width - 1; result.Y = (source.Y - _control.ClientRectangle.Y) * 2 / _control.ClientRectangle.Height - 1; result.Z = source.Z - 1; if (_farPlane - 1 == 0) result.Z = 0; else result.Z = result.Z / (_farPlane - 1); result.W = 1f; result = Vector4.Transform(result, Matrix4.Invert(ProjectionMatrix)); result = Vector4.Transform(result, Matrix4.Invert(ViewMatrix)); result = Vector4.Transform(result, Matrix4.Invert(_world)); result = Vector4.Divide(result, result.W); return new Vector3(result.X, result.Y, result.Z); } And my triangle intersection code. Ripped mainly from the XNA picking sample. public float? Intersects(Ray ray) { float? closestHit = Bounds.Intersects(ray); if (closestHit != null && Vertices.Length == 3) { Vector3 e1, e2; Vector3.Subtract(ref Vertices[1].Position, ref Vertices[0].Position, out e1); Vector3.Subtract(ref Vertices[2].Position, ref Vertices[0].Position, out e2); Vector3 directionCrossEdge2; Vector3.Cross(ref ray.Direction, ref e2, out directionCrossEdge2); float determinant; Vector3.Dot(ref e1, ref directionCrossEdge2, out determinant); if (determinant > -float.Epsilon && determinant < float.Epsilon) return null; float inverseDeterminant = 1.0f/determinant; Vector3 distanceVector; Vector3.Subtract(ref ray.Position, ref Vertices[0].Position, out distanceVector); float triangleU; Vector3.Dot(ref distanceVector, ref directionCrossEdge2, out triangleU); triangleU *= inverseDeterminant; if (triangleU < 0 || triangleU > 1) return null; Vector3 distanceCrossEdge1; Vector3.Cross(ref distanceVector, ref e1, out distanceCrossEdge1); float triangleV; Vector3.Dot(ref ray.Direction, ref distanceCrossEdge1, out triangleV); triangleV *= inverseDeterminant; if (triangleV < 0 || triangleU + triangleV > 1) return null; float rayDistance; Vector3.Dot(ref e2, ref distanceCrossEdge1, out rayDistance); rayDistance *= inverseDeterminant; if (rayDistance < 0) return null; return rayDistance; } return closestHit; } I'll admit I don't fully understand all of the math behind the intersection and that is something I'm working on, but my understanding was that if rayDistance was less than 0 the face was facing away from the camera, and shouldn't be counted as a hit. So my question is, is there an issue with my intersection or ray creation code, or is there another check I need to perform to tell if the face is facing away from the camera, and if so any hints on what that check might contain would be appreciated.

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  • How do I prevent a KActor from changing the orientation of its Z-Axis?

    - by Almo
    So I have an object that inherits from KActor that I would like to behave as a dynamic physics object, but I want its Z-Axis to remain upright, but very stiffly. I've tried the bStayUpright that triggers the "Stay Upright Spring". The problem is, it's a spring, and the object in question oscillates into position when I want it to remain oriented properly without wobbling. In the image above, the yellow block has fallen onto the gray box, and it is currently pivoting about the contact point as it tries to right itself. Should I be tweaking the StayUprightMaxTorque and StayUprightTorqueFactor parameters, or should I be using a Constraint of some sort?

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