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

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

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  • 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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  • Physics not synchronizing correctly over the network when using Bullet

    - by Lucas
    I'm trying to implement a client/server physics system using Bullet however I'm having problems getting things to sync up. I've implemented a custom motion state which reads and write the transform from my game objects and it works locally but I've tried two different approaches for networked games: Dynamic objects on the client that are also on the server (eg not random debris and other unimportant stuff) are made kinematic. This works correctly but the objects don't move very smoothly Objects are dynamic on both but after each message from the server that the object has moved I set the linear and angular velocity to the values from the server and call btRigidBody::proceedToTransform with the transform on the server. I also call btCollisionObject::activate(true); to force the object to update. My intent with method 2 was to basically do method 1 but hijacking Bullet to do a poor-man's prediction instead of doing my own to smooth out method 1, but this doesn't seem to work (for reasons that are not 100% clear to me even stepping through Bullet) and the objects sometimes end up in different places. Am I heading in the right direction? Bullet seems to have it's own interpolation code built-in. Can that help me make method 1 work better? Or is my method 2 code not working because I am accidentally stomping that?

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  • Issues with shooting in a HTML5 platformer game

    - by fnx
    I'm coding a 2D sidescroller using only JavaScript and HTML5 canvas, and in my game I have two problems with shooting: 1) Player shoots continous stream of bullets. I want that player can shoot only a single bullet even though the shoot-button is being held down. 2) Also, I get an error "Uncaught TypeError: Cannot call method 'draw' of undefined" when all the bullets are removed. My shooting code goes like this: When player shoots, I do game.bullets.push(new Bullet(this, this.scale)); and after that: function Bullet(source, dir) { this.id = "bullet"; this.width = 10; this.height = 3; this.dir = dir; if (this.dir == 1) { this.x = source.x + source.width - 5; this.y = source.y + 16; } if (this.dir == -1) { this.x = source.x; this.y = source.y + 16; } } Bullet.prototype.update = function() { if (this.dir == 1) this.x += 8; if (this.dir == -1) this.x -= 8; for (var i in game.enemies) { checkCollisions(this, game.enemies[i]); } // Check if bullet leaves the viewport if (this.x < game.viewX * 32 || this.x > (game.viewX + game.tilesX) * 32) { removeFromList(game.bullets, this); } } Bullet.prototype.draw = function() { // bullet flipping uses orientation of the player var posX = game.player.scale == 1 ? this.x : (this.x + this.width) * -1; game.ctx.scale(game.player.scale, 1); game.ctx.drawImage(gameData.getGfx("bullet"), posX, this.y); } I handle removing with this function: function removeFromList(list, object) { for (i in list) { if (object == list[i]) { list.splice(i, 1); break; } } } And finally, in the main game loop I have this: for (var i in game.bullets) { game.bullets[i].update(); game.bullets[i].draw(); } I have tried adding if (game.bullets.length > 0) to the main game loop before the above draw&update calls, but I still get the same error.

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  • Is it ok to initialize an RB_ConstraintActor in PostBeginPlay?

    - by Almo
    I have a KActorSpawnable subclass that acts weird. In PostBeginPlay, I initialize an RB_ConstraintActor; the default is not to allow rotation. If I create one in the editor, it's fine, and won't rotate. If I spawn one, it rotates. Here's the class: class QuadForceKActor extends KActorSpawnable placeable; var(Behavior) bool bConstrainRotation; var(Behavior) bool bConstrainX; var(Behavior) bool bConstrainY; var(Behavior) bool bConstrainZ; var RB_ConstraintActor PhysicsConstraintActor; simulated event PostBeginPlay() { Super.PostBeginPlay(); PhysicsConstraintActor = Spawn(class'RB_ConstraintActorSpawnable', self, '', Location, rot(0, 0, 0)); if(bConstrainRotation) { PhysicsConstraintActor.ConstraintSetup.bSwingLimited = true; PhysicsConstraintActor.ConstraintSetup.bTwistLimited = true; } SetLinearConstraints(bConstrainX, bConstrainY, bConstrainZ); PhysicsConstraintActor.InitConstraint(self, None); } function SetLinearConstraints(bool InConstrainX, bool InConstrainY, bool InConstrainZ) { if(InConstrainX) { PhysicsConstraintActor.ConstraintSetup.LinearXSetup.bLimited = 1; } else { PhysicsConstraintActor.ConstraintSetup.LinearXSetup.bLimited = 0; } if(InConstrainY) { PhysicsConstraintActor.ConstraintSetup.LinearYSetup.bLimited = 1; } else { PhysicsConstraintActor.ConstraintSetup.LinearYSetup.bLimited = 0; } if(InConstrainZ) { PhysicsConstraintActor.ConstraintSetup.LinearZSetup.bLimited = 1; } else { PhysicsConstraintActor.ConstraintSetup.LinearZSetup.bLimited = 0; } } DefaultProperties { bConstrainRotation=true bConstrainX=false bConstrainY=false bConstrainZ=false bSafeBaseIfAsleep=false bNoEncroachCheck=false } Here's the code I use to spawn one. It's a subclass of the one above, but it doesn't reference the constraint at all. local QuadForceKCreateBlock BlockActor; BlockActor = spawn(class'QuadForceKCreateBlock', none, 'PowerCreate_Block', BlockLocation(), m_PreparedRotation, , false); BlockActor.SetDuration(m_BlockDuration); BlockActor.StaticMeshComponent.SetNotifyRigidBodyCollision(true); BlockActor.StaticMeshComponent.ScriptRigidBodyCollisionThreshold = 0.001; BlockActor.StaticMeshComponent.SetStaticMesh(m_ValidCreationBlock.StaticMesh); BlockActor.StaticMeshComponent.AddImpulse(m_InitialVelocity); I used to initialize an RB_ConstraintActor where I spawned it from the outside. This worked, which is why I'm pretty sure it has nothing to do with the other code in QuadForceKCreateBlock. I then added the internal constraint in QuadForceKActor for other purposes. When I realized I had two constraints on the CreateBlock doing the same thing, I removed the constraint code from the place where I spawn it. Then it started rotating. Is there a reason I should not be initializing an RB_ConstraintActor in PostBeginPlay? I feel like there's some basic thing about how the engine works that I'm missing.

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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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  • Fastest bit-blit in C# ?

    - by AttackingHobo
    I know there is Unity, and XNA that both use C#, but I am don't know what else I could use. The reason I say C# is that the syntax and style is similar to AS3, which I am familiar with, and I want to choose the correct framework to start learning with. What should I use to be able to do the most possible bit-blit(direct pixel copy) objects per frame. EDIT: I should not need to add this, but I am looking for the most possible amount of objects per frame because I am making a few Bullet-Hell SHMUPS. I need thousands and thousands of bullets, particles, and hundreds of enemies on the screen at once. I am looking for a solution to do as many bit-blit operations per frame, I am not looking for a general purpose engine. EDIT2: I want bit-blitting because I do not want to exclude people who have lower end video cards but a fast processor from playing my games.

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  • Sprite Animation in Android with OpenGL ES

    - by lijo john
    How to do a sprite animation in android using OpenGL ES? What i have done : Now I am able to draw a rectangle and apply my texture(Spritesheet) to it What I need to know : Now the rectangle shows the whole sprite sheet as a whole How to show a single action from sprite sheet at a time and make the animation It will be very help full if anyone can share any idea's , links to tutorials and suggestions. Advanced Thanks to All

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  • Assets.getBytes returns null in test environment

    - by ashes999
    I'm using the latest Haxe (2.10), NME (3.4.3), and MUnit. I've written some unit tests that need to fetch bitmap data from SWF symbols. The first step is to actually load the SWF data. To do this, I use NME's getByteArray along with the swf library, like so: var blah:SWF = new SWF(Assets.getBytes("assets/swf/test.swf")); The call to Assets.getBytes returns null when I'm running this under MUnit. When running my actual game code, I'm able to get the byte array (and consequentially, instantiate the SWF class). Am I doing something wrong? What am I missing? Edit: My directory structure is: . (root .\assets .\assets\*.png (other images) .\assets\swf\*.swf (SWFs) .\Source\*.hx (source code) .\Test\*.hx (tests)

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  • Interpolating between two networked states?

    - by Vaughan Hilts
    I have many entities on the client side that are simulated (their velocities are added to their positions on a per frame basis) and I let them dead reckon themselves. They send updates about where they were last seen and their velocity changes. This works great and other players see this work find. However, after a while these players begin to desync after some time. This is because of latency. I'd like to know how I can interpolate between states so they appear to be in the correct position. I know where the player was LAST seen and their current velocity but interpolating to the last seen state causes the player to actually move -backwards-. I could not use velocity at all for other clients and simply 'lerp' them towards the appropriate direction but I feel this would cause jaggy movement. What are the alternatives?

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  • Implementing Circle Physics in Java

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

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  • 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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  • Using two joysticks in Cocos2D

    - by Blade
    Here is what I am trying to do: With the left joystick the player can steer the figure and with the right joystick it can attack. Problem is that the left joystick seems to get all the input, the right one does not even register anything. I enabled multipletouch after the eagleView and gone thoroughly over the code. But I seem to miss something. I initiliaze both sticks and it shows me both of them in game, but like I said, only the left one works. I initialize them both. From the h. file: SneakyJoystick *joystick; SneakyJoystick *joystickRight; And in m.file I synthesize, deallocate and initialize them. In order to use one for controlling and the other for attacking I put this: -(void)updateStateWithDeltaTime:(ccTime)deltaTime andListOfGameObjects:(CCArray*)listOfGameObjects { if ((self.characterState == kStateIdle) || (self.characterState == kStateWalkingBack) || (self.characterState == kStateWalkingLeft) || (self.characterState == kStateWalkingRight)|| (self.characterState == kStateWalkingFront) || (self.characterState == kStateAttackingFront) || (self.characterState == kStateAttackingBack)|| (self.characterState == kStateAttackingRight)|| (self.characterState == kStateAttackingLeft)) { if (joystick.degrees > 60 && joystick.degrees < 120) { if (self.characterState != kStateWalkingBack) [self changeState:kStateWalkingBack]; }else if (joystick.degrees > 1 && joystick.degrees < 59) { if (self.characterState != kStateWalkingRight) [self changeState:kStateWalkingRight]; } else if (joystick.degrees > 211 && joystick.degrees < 300) { if (self.characterState != kStateWalkingFront) [self changeState:kStateWalkingFront]; } else if (joystick.degrees > 301 && joystick.degrees < 360){ if (self.characterState != kStateWalkingRight) [self changeState:kStateWalkingRight]; } else if (joystick.degrees > 121 && joystick.degrees < 210) { if (self.characterState != kStateWalkingLeft) [self changeState:kStateWalkingLeft]; } if (joystickRight.degrees > 60 && joystickRight.degrees < 120) { if (self.characterState != kStateAttackingBack) [self changeState:kStateAttackingBack]; }else if (joystickRight.degrees > 1 && joystickRight.degrees < 59) { if (self.characterState != kStateAttackingRight) [self changeState:kStateAttackingRight]; } else if (joystickRight.degrees > 211 && joystickRight.degrees < 300) { if (self.characterState != kStateAttackingFront) [self changeState:kStateAttackingFront]; } else if (joystickRight.degrees > 301 && joystickRight.degrees < 360){ if (self.characterState != kStateAttackingRight) [self changeState:kStateAttackingRight]; } else if (joystickRight.degrees > 121 && joystickRight.degrees < 210) { if (self.characterState != kStateAttackingLeft) [self changeState:kStateAttackingLeft]; } [self applyJoystick:joystick forTimeDelta:deltaTime]; [self applyJoystick:joystickRight forTimeDelta:deltaTime]; } Maybe it has something to do with putting them both to time delta? I tried working around it, but it did not work. So I am thankful for any input you guys can give me :)

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  • Order independent transparency in particle system

    - by Stepan Zastupov
    I'm writing a particle system and would like to find a trick to achieve proper alpha blending without sorting particles because: Each particle is a point sprite in a single mesh and I can't use scene graph ability to sort transparent nodes. The system node should be properly sorted, though. Particle position is computed on shader from initial velocity, acceleration and time. In order to sort the system I would have to perform all this computations on CPU, which is something I want to avoid. Sorting hundreds of particles against camera position and uploading it on GPU each frame seams to be quiet heavy operation. Alpha testing seems to be fast enough on GLES 2.0 and works fine for non-transparent but "masked" textures. Still, it's not enough for semi-transparent particles. How would you handle this?

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  • Designing a flexible tile-based engine

    - by Vee
    I'm trying to create a flexible tile-based game engine to make all sorts of non-realtime puzzle games, just as Bejeweled, Civilization, Sokoban, and so on. The first approach I had was to have a 2D array of Tile objects, and then have classes inheriting from Tile that represented the game objects. Unfortunately that way I couldn't stack more game elements on the same Tile without having a 3D array. Then I did something different: I still had the 2D array of Tile objects, but every Tile object contained a List where I put and different entities. This worked fine until 20 minutes ago, when I realized that it's too expensive to do many things, look at this example: I have a Wall entity. Every update I have to check the 8 adjacent Tiles, then check all of the entities in the Tile's List, check if any of those entities is a Wall, then finally draw the correct sprite. (This is done to draw walls that are next to each other seamlessly) The only solution I see now is having a 3D array, with many layers, that could suit every situation. But that way I can't stack two entities that share the same layer on the same tile. Whenever I want to do that I have to create a new layer. Is there a better solution? What would you do?

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  • Unable to use Maya animation with scripts when imported to Unity

    - by keshk
    I am testing to import Maya animation over to Unity. I set up a simple cylinder with 2 bones and an IK handle. Made a simple animation where the cylinder bends and goes back to straight position over 24 frames. Following that, I selected everything and baked, all bones,ik,(animation by selecting all at the graph editor) and even the cylinder. I saved the scene and then select all and export as FBX with animation and bake checked. In unity imported it and at the preview able to see the animation. When I load the model into scene and play (after assigning the controller), able to see animation too. But now when I try to script it and control the animation, nothing happens. Even to test, I tried the following under the Update method. if(animation.isPlaying) Debug.Log("Animation Works"); else Debug.Log("Animation not working"); The bool doesn't even return true nor false. My animation is called "bend", thus just for try I did the following and nothing happens. animation.Play("bend"); Can please advice based on my steps, am I missing something. Do I need to add the controller or is that an unnecessary step? Did I screw up on the Maya part or the Unity part. Thanks for help.

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  • How do I create a camera?

    - by Morphex
    I am trying to create a generic camera class for a game engine, which works for different types of cameras (Orbital, GDoF, FPS), but I have no idea how to go about it. I have read about quaternions and matrices, but I do not understand how to implement it. Particularly, it seems you need "Up", "Forward" and "Right" vectors, a Quaternion for rotations, and View and Projection matrices. For example, an FPS camera only rotates around the World Y and the Right Axis of the camera; the 6DoF rotates always around its own axis, and the orbital is just translating for a set distance and making it look always at a fixed target point. The concepts are there; implementing this is not trivial for me. SharpDX seems to have has already Matrices and Quaternions implemented, but I don't know how to use them to create a camera. Can anyone point me on what am I missing, what I got wrong? I would really enjoy if you could give a tutorial, some piece of code, or just plain explanation of the concepts.

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  • Sprite transparency not effected libGDX

    - by Aon GoltzCrank
    I am making a game using libGDX and Tween Universal Engine. My problem is as follows: I have 2 screens so fars, a splash screen with the logo, and a second one which is the main menu. In the splash screen I use a SpriteBatch and a Sprite with the Texture of the image I want (which goes through some scaling.) Now I use the Tween engine, along with a created SpriteAccessor to control the alpha of the sprite. I fade the picture in, then fade it out, then change it to the next screen. In the next screen I have a single sprite, and a single, 3 slot, sprite array. In this screen I also use the tween engine, I fade the single sprite into the screen (it's the background image) then I try to, using the same method, (Tween.to) to change the alpah of the sprite array (each sprite by itself.), I first set it to 0 using Tween.set, then using the method I change it. This didn't work, after some tests I tried setting the alpha of a single sprite from the array to 0, and that didn't work. It's like the program is ignoring the alpha value, I even printed out the alpha value, it saying 0, but the sprite is visible. How can I fix this, or why might it be caused?

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  • Elliptical orbit modeling

    - by Nathon
    I'm playing with orbits in a simple 2-d game where a ship flies around in space and is attracted to massive things. The ship's velocity is stored in a vector and acceleration is applied to it every frame as appropriate given Newton's law of universal gravitation. The point masses don't move (there's only 1 right now) so I would expect an elliptical orbit. Instead, I see this: I've tried with nearly circular orbits, and I've tried making the masses vastly different (a factor of a million) but I always get this rotated orbit. Here's some (D) code, for context: void accelerate(Vector delta) { velocity = velocity + delta; // Velocity is a member of the ship class. } // This function is called every frame with the fixed mass. It's a // method of the ship's. void fall(Well well) { // f=(m1 * m2)/(r**2) // a=f/m // Ship mass is 1, so a = f. float mass = 1; Vector delta = well.position - loc; float rSquared = delta.magSquared; float force = well.mass/rSquared; accelerate(delta * force * mass); }

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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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  • how to transform child elements position into a world position

    - by MrGreg
    So Im making a 2d space game and I have a bunch of spaceships that have turrets. Objects have a position and orientation, the ships being in world coordinates while the turrets are children and coordinates are relative to their parents. How do I efficiently calculate the position of a turret in world coordinates (i.e. when it fires and I need to know where to place a bullet in the world)? Calculating the turrets orientation is trivial - I just add the turrets relative angle to its parents. For position though, I guess I could do a bunch of trigonometry but this MUST be a common problem with a good/fast general solution? Should I be relearning how to do matrix math again? :) btw - Im creating the game in javascript+canvas but its the math/algorithm im interested in here Cheers, Greg

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  • Trouble with SAT style vector projection in C#/XNA

    - by ssb
    Simply put I'm having a hard time working out how to work with XNA's Vector2 types while maintaining spatial considerations. I'm working with separating axis theorem and trying to project vectors onto an arbitrary axis to check if those projections overlap, but the severe lack of XNA-specific help online combined with pseudo code everywhere that omits key parts of the algorithm, googling has left me little help. I'm aware of HOW to project a vector, but the way that I know of doing it involves the two vectors starting from the same point. Particularly here: http://www.metanetsoftware.com/technique/tutorialA.html So let's say I have a simple rectangle, and I store each of its corners in a list of Vector2s. How would I go about projecting that onto an arbitrary axis? The crux of my problem is that taking the dot product of say, a vector2 of (1, 0) and a vector2 of (50, 50) won't get me the dot product I'm looking for.. or will it? Because that (50, 50) won't be the vector of the polygon's vertex but from whatever XNA calculates. It's getting the calculation from the right starting point that's throwing me off. I'm sorry if this is unclear, but my brain is fried from trying to think about this. I need a better understanding of how XNA calculates Vector2s as actual vectors and not just as random points.

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  • FBX Importer - Texture Name

    - by CmasterG
    I have a problem with the FBX SDK. I read in the data for the vertex position and the uv coordinates. It works fine, but now I want to read for each polygon to which texture it belongs, so that I can have models with multiple textures. Can anyone tell me how I can get the texture name (file name) for my polygon. My code to read in vertex position and uv coordinates is the following: int i, j, lPolygonCount = pMesh->GetPolygonCount(); FbxVector4* lControlPoints = pMesh->GetControlPoints(); int vertexId = 0; for (i = 0; i < lPolygonCount; i++) { int lPolygonSize = pMesh->GetPolygonSize(i); for (j = 0; j < lPolygonSize; j++) { int lControlPointIndex = pMesh->GetPolygonVertex(i, j); FbxVector4 pos = lControlPoints[lControlPointIndex]; current_model[vertex_index].x = pos.mData[0] - pivot_offset[0]; current_model[vertex_index].y = pos.mData[1] - pivot_offset[1]; current_model[vertex_index].z = pos.mData[2]- pivot_offset[2]; FbxVector4 vertex_normal; pMesh->GetPolygonVertexNormal(i,j, vertex_normal); current_model[vertex_index].nx = vertex_normal.mData[0]; current_model[vertex_index].ny = vertex_normal.mData[1]; current_model[vertex_index].nz = vertex_normal.mData[2]; //read in UV data FbxStringList lUVSetNameList; pMesh->GetUVSetNames(lUVSetNameList); //get lUVSetIndex-th uv set const char* lUVSetName = lUVSetNameList.GetStringAt(0); const FbxGeometryElementUV* lUVElement = pMesh->GetElementUV(lUVSetName); if(!lUVElement) continue; // only support mapping mode eByPolygonVertex and eByControlPoint if( lUVElement->GetMappingMode() != FbxGeometryElement::eByPolygonVertex && lUVElement->GetMappingMode() != FbxGeometryElement::eByControlPoint ) return; //index array, where holds the index referenced to the uv data const bool lUseIndex = lUVElement->GetReferenceMode() != FbxGeometryElement::eDirect; const int lIndexCount= (lUseIndex) ? lUVElement->GetIndexArray().GetCount() : 0; FbxVector2 lUVValue; //get the index of the current vertex in control points array int lPolyVertIndex = pMesh->GetPolygonVertex(i,j); //the UV index depends on the reference mode //int lUVIndex = lUseIndex ? lUVElement->GetIndexArray().GetAt(lPolyVertIndex) : lPolyVertIndex; int lUVIndex = pMesh->GetTextureUVIndex(i, j); lUVValue = lUVElement->GetDirectArray().GetAt(lUVIndex); current_model[vertex_index].tu = (float)lUVValue.mData[0]; current_model[vertex_index].tv = (float)lUVValue.mData[1]; vertex_index ++; } } float v1[3], v2[3], v3[3]; v1[0] = current_model[vertex_index - 3].x; v1[1] = current_model[vertex_index - 3].y; v1[2] = current_model[vertex_index - 3].z; v2[0] = current_model[vertex_index - 2].x; v2[1] = current_model[vertex_index - 2].y; v2[2] = current_model[vertex_index - 2].z; v3[0] = current_model[vertex_index - 1].x; v3[1] = current_model[vertex_index - 1].y; v3[2] = current_model[vertex_index - 1].z; collision_model->addTriangle(v1,v2,v3);

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

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

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  • Calculate the intersection depth between a rectangle and a right triangle

    - by Celarix
    all. I'm working on a 2D platformer built in C#/XNA, and I'm having a lot of problems calculating the intersection depth between a standard rectangle (used for sprites) and a right triangle (used for sloping tiles). Ideally, the rectangle will collide with the solid edges of the triangle, and its bottom-center point will collide with the sloped edge. I've been fighting with this for a couple of days now, and I can't make sense of it. So far, the method detects intersections (somewhat), but it reports wildly wrong depths. How does one properly calculate the depth? Is there something I'm missing? Thanks!

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