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  • How to make an object fly out of a slingshot?

    - by Deza
    At the moment I'm improvising a slingshot, the user can click and drag the projectile and let go. The force on the object is calculated by getting the distance between the vector of the slingshots two forks and the vector between where the user pulled it. However this will always result in a positive number and will not take into account the angle of the object relative to that of the slingshot. How can I make it fly out of the slingshot correctly?

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  • Farseer circle hangs where it's spawned

    - by necrosmash
    I'm currently trying to simply spawn a circle in Farseer. However, it's stuck wherever I spawn it! The game is updating fine, as I can see the circle spinning in place when I spawn it because of how I currently have gravity set up (following code from Game1.cs): // Initialise the screen center for use with // the Level class screenCenter = new Vector2(graphics.GraphicsDevice.Viewport.Width / 2f, graphics.GraphicsDevice.Viewport.Height / 2f); world = new World(new Vector2(20, 20)); currentLevel = new Level1(screenCenter, circleSprite, groundSprite, ref world); Level1 constructor: public Level1(Vector2 screenCenter, Texture2D circleSprite, Texture2D groundSprite, ref World world) { player = new Player(ref world, screenCenter, circleSprite); ground = new Ground(ref world, screenCenter, groundSprite); listLevelItems = new List<LevelItem>(); listLevelItems.Add(player); listLevelItems.Add(ground); } Player constructor: public Player(ref World world, Vector2 screenCenter, Texture2D sprite) { setSprite(sprite); setPosition((screenCenter / MeterInPixels) + new Vector2(0f, 0f)); playerBody = BodyFactory.CreateCircle(world, 96f / (2f * MeterInPixels), 1f, playerPosition); getBody().BodyType = BodyType.Dynamic; // Ball bounce and friction getBody().Restitution = 0.3f; getBody().Friction = 0.5f; } If I use a breakpoint and change the playerBody position while the game is halted, the ball does move, but stays fixed in its new location. Any help would be greatly appreciated.

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  • Elastic Collision Formula in Java

    - by Shijima
    I'm trying to write a Java formula based on this tutorial: 2-D elastic collisions without Trigonometry. I am in the section "Elastic Collisions in 2 Dimensions". In step 1, it mentions "Next, find the unit vector of n, which we will call un. This is done by dividing by the magnitude of n". My below code represents the normal vector of 2 objects (I'm using a simple array to represent the normal vector), but I am not really sure what the tutorial means by dividing the magnitude of n to get the un. int[] normal = new int[2]; normal[0] = ball2.x - ball1.x; normal[1] = ball2.y - ball1.y; Can anyone please explain what un is, and how I can calculate it with my array in Java?

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  • Simulating water droplets on a window

    - by skyuzo
    How do I simulate water droplets realistically falling, gathering, and flowing down a window? For example, see http://www.youtube.com/watch?v=4jaGyv0KRPw. In particular, I want to simulate how smaller droplets merge together to form larger droplets that have enough weight to oppose the surface tension and flow downward, leaving a trail of water. I'm aware of fluid simulation, but how would it be applied in this situation?

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  • How to determine which thrusters to turn on to rotate the ship?

    - by migimunz
    The configuration of the ship changes dynamically, so I have to determine which thruster to turn on when I want to rotate the ship clockwise or counter clockwise. The thrusters are always axis aligned with the ship (never at an angle) and are either on or off. Here's one of the possible setups: What I've tried so far is to visualize the firing vector and the direction vector to the center of mass of the ship: Unfortunately, I didn't get very far with that.

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  • Collider2D and Rigidbody2D, how do they work?

    - by user42646
    I have been learning JavaScript and Unity for a week now. I learned how to make Cube as a Ground and another Cube as a player and I used this code to make the Player Cube move forward and backward and jumping var walkspeed: float = 5.0; var jumpheight: float = 250.0; var grounded = false; function Update() { rigidbody.freezeRotation = true; if (Input.GetKey("a")) transform.Translate(Vector3(-1, 0, 0) * Time.deltaTime * walkspeed); if (Input.GetKey("d")) transform.Translate(Vector3(1, 0, 0) * Time.deltaTime * walkspeed); if (Input.GetButton("Jump")) { Jump(); } } function OnCollisionEnter(hit: Collision) { grounded = true; } function Jump() { if (grounded == true) { rigidbody.AddForce(Vector3.up * jumpheight); grounded = false; } } I also learned how to make a character hit box. how to make a sprite and animation. pretty much the basic stuff. Couple of days ago I created simple ground in Photoshop and a simple character and imported them to Unity3D. Whenever I use my code above the character keeps falling from the scene. Like the character has nothing to stand on. After thinking about it it make sense because I really didn't make anything to make the player character understand that he should stand on something so I started reading about this issue and I realized that there is something called Collider2D and Rigidbody2D. Now I'm really stuck here I just don't know what to do. I applied the rigibody2d to my character picture and the Collider2D to the ground picture but whenever I play the project the gravity makes my character falls down. This is my question: How can I make the rigibody2d object realize that it shouldn't fall if there is a Collider2D object under it? So when I jump it's going to jump and the gravity going to bring it back to the ground.

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  • How do I convert a partially transparent image into polygons?

    - by user82779
    I'm using GLEE2D, a level editor allowing me to import images, scale them, rotate them, and position them onto layers and export the data into XML format. However, it does not tell me objects' boundaries. I can calculate them, but only given the original image's polygons. How do I get polygons of objects in a transparent image? An example object (I outlined it): How would I turn the object, knowing the scaled size of the image, into polygons? Is there an algorithm for this? I'll use OpenGL to draw them.

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  • how to stop enemies from moving to one point when lots of them are chasing one object [duplicate]

    - by BBgun
    This question already has an answer here: Is there a simple way to stop enemies standing in the same spot? 8 answers i am making a top down game which lots of enemies are chasing one guy. then,enemies would move to one point without any collision,they just overlay each other. so ,is there any simple way to make them feel more real? make them not overlay with each other? ================================= i have tried the solution using boundbox to check collision, but i still very puzzled about what to do with the collision. i have a bad solution.it doesn't work well. my solution in simple: foreach(around_enemy_arr in other) { vector a = normalize(self.positionvector - other.positionvector); self.move_vector = self.move_vector + a; } this can work,but when plenty of enemies come very close to each other,they would shake. i am sooooo confused. please help.

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  • UIPageControl bug: showing one bullet first and then showing everything

    - by user313551
    I have some strange behavior using a UIPageControl: First it appears showing only one bullet, then when I move the scroll view all the bullets appear correctly. Is there something I'm missing before I add it as a subview? Here is my code imageScrollView.h : @interface ImageScrollView : UIView <UIScrollViewDelegate> { NSMutableDictionary *photos; BOOL *pageControlIsChangingPage; UIPageControl *pageControl; } @property (nonatomic, copy) NSMutableDictionary *photos; @property (nonatomic, copy) UIPageControl *pageControl; @end Here is the code for imageScrollView.m: #import "ImageScrollView.h" @implementation ImageScrollView @synthesize photos, pageControl; - (id)initWithFrame:(CGRect)frame { if ((self = [super initWithFrame:frame])) { // Initialization code NSLog(@"%@",pageControl); } return self; } - (void) drawRect:(CGRect)rect { [self removeAllSubviews]; UIScrollView *scroller = [[UIScrollView alloc] initWithFrame:CGRectMake(0,0,self.frame.size.width,self.frame.size.height)]; [scroller setDelegate:self]; [scroller setBackgroundColor:[UIColor grayColor]]; [scroller setShowsHorizontalScrollIndicator:NO]; [scroller setPagingEnabled:YES]; NSUInteger nimages = 0; CGFloat cx= 0; for (NSDictionary *myDictionaryObject in photos) { if (![myDictionaryObject isKindOfClass:[NSNull class]]) { NSString *photo =[NSString stringWithFormat:@"http://www.techbase.com.mx/blog/%@", [myDictionaryObject objectForKey:@"filepath"]]; NSDictionary *data = [myDictionaryObject objectForKey:@"data"]; UIView *imageContainer = [[UIView alloc] initWithFrame:CGRectMake(0, 0, self.frame.size.width, self.frame.size.height - 30)]; TTImageView *imageView = [[TTImageView alloc] initWithFrame:CGRectMake(0, 0, self.frame.size.width, self.frame.size.height - 30)]; imageView.urlPath=photo; [imageContainer addSubview:imageView]; UILabel *caption = [[UILabel alloc] initWithFrame:CGRectMake(0,imageView.frame.size.height,imageView.frame.size.width,10)]; [caption setText:[NSString stringWithFormat:@"%@",[data objectForKey:@"description"]]]; [caption setBackgroundColor:[UIColor grayColor]]; [caption setTextColor:[UIColor whiteColor]]; [caption setLineBreakMode:UILineBreakModeWordWrap]; [caption setNumberOfLines:0]; [caption sizeToFit]; [caption setFont:[UIFont fontWithName:@"Georgia" size:10.0]]; [imageContainer addSubview:caption]; CGRect rect = imageContainer.frame; rect.size.height = imageContainer.size.height; rect.size.width = imageContainer.size.width; rect.origin.x = ((scroller.frame.size.width - scroller.size.width) / 2) + cx; rect.origin.y = ((scroller.frame.size.height - scroller.size.height) / 2); imageContainer.frame=rect; [scroller addSubview:imageContainer]; [imageView release]; [imageContainer release]; [caption release]; nimages++; cx +=scroller.frame.size.width; } } [scroller setContentSize:CGSizeMake(nimages * self.frame.size.width, self.frame.size.height)]; [self addSubview:scroller]; pageControl = [[UIPageControl alloc] initWithFrame:CGRectMake(self.frame.size.width/2, self.frame.size.height -20, (self.frame.size.width/nimages)/2, 20)]; pageControl.numberOfPages=nimages; [self addSubview:pageControl]; [scroller release]; } -(void)dealloc { [pageControl release]; [super dealloc]; } -(void)scrollViewDidScroll:(UIScrollView *)_scrollView{ if(pageControlIsChangingPage){ return; } CGFloat pageWidth = _scrollView.frame.size.width; int page = floor((_scrollView.contentOffset.x - pageWidth /2) / pageWidth) + 1; pageControl.currentPage = page; } -(void)scrollViewDidEndDecelerating:(UIScrollView *)_scrollView{ pageControlIsChangingPage = NO; } @end

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  • Car physics in Chipmunk

    - by Richard Caetano
    Has anyone had experience with implementing car physics in chipmunk? Here's an example in Box2d: http://www.emanueleferonato.com/2009/04/06/two-ways-to-make-box2d-cars/ I'd like to port that over to chipmunk.

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  • How to implement "bullet time" in a multiplayer game?

    - by Tom
    I have never seen such a feature before, but it should provide an interesting gameplay opportunity. So yes, in a multiplayer/real-time environment (imagine FPS), how could I implement a slow motion/bullet time effect? Something like an illusion for the player that's currently slo-mo'ed. So everybody sees him "real-time", but he sees everything slowed down. Update A sidenote: keep in mind that a FPS game has to be balanced in order for it to be fun. So yes, this bullet time feature has to be solid, giving a small advantage to the "player", while not taking away from other players. Plus, there is a possibility that two players could activate their bullet time at the same time. Furthermore: I'm going to implement this in the future no matter what it takes. And, the idea is to build a whole new game engine for all this. If that gives new options, I'm more then interested in hearing the ideas. Meanwhile, here with my team we're thinking about this too, when our theory will be crafted, I'm going to share it here. Is this even possible? So, the question on "is this even possible" has been answered, now it's time to find the best solution. I'm keeping the "answer" until something exceptionally good comes up, like a prototype theory with something close to working pseudo code.

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  • Flash AS3 Mysterious Blinking MovieClip

    - by Ben
    This is the strangest problem I've faced in flash so far. I have no idea what's causing it. I can provide a .swf if someone wants to actually see it, but I'll describe it as best I can. I'm creating bullets for a tank object to shoot. The tank is a child of the document class. The way I am creating the bullet is: var bullet:Bullet = new Bullet(); (parent as MovieClip).addChild(bullet); The bullet itself simply moves itself in a direction using code like this.x += 5; The problem is the bullets will trace for their creation and destruction at the correct times, however the bullet is sometimes not visible until half way across the screen, sometimes not at all, and sometimes for the whole traversal. Oddly removing the timer I have on bullet creation seems to solve this. The timer is implemented as such: if(shot_timer == 0) { shoot(); // This contains the aforementioned bullet creation method shot_timer = 10; My enter frame handler for the tank object controls the timer and decrements it every frame if it is greater than zero. Can anyone suggest why this could be happening? EDIT: As requested, full code: Bullet.as package { import flash.display.MovieClip; import flash.events.Event; public class Bullet extends MovieClip { public var facing:int; private var speed:int; public function Bullet():void { trace("created"); speed = 10; addEventListener(Event.ADDED_TO_STAGE,addedHandler); } private function addedHandler(e:Event):void { addEventListener(Event.ENTER_FRAME,enterFrameHandler); removeEventListener(Event.ADDED_TO_STAGE,addedHandler); } private function enterFrameHandler(e:Event):void { //0 - up, 1 - left, 2 - down, 3 - right if(this.x > 720 || this.x < 0 || this.y < 0 || this.y > 480) { removeEventListener(Event.ENTER_FRAME,enterFrameHandler); trace("destroyed"); (parent as MovieClip).removeChild(this); return; } switch(facing) { case 0: this.y -= speed; break; case 1: this.x -= speed; break; case 2: this.y += speed; break; case 3: this.x += speed; break; } } } } Tank.as: package { import flash.display.MovieClip; import flash.events.KeyboardEvent; import flash.events.Event; import flash.ui.Keyboard; public class Tank extends MovieClip { private var right:Boolean = false; private var left:Boolean = false; private var up:Boolean = false; private var down:Boolean = false; private var facing:int = 0; //0 - up, 1 - left, 2 - down, 3 - right private var horAllowed:Boolean = true; private var vertAllowed:Boolean = true; private const GRID_SIZE:int = 100; private var shooting:Boolean = false; private var shot_timer:int = 0; private var speed:int = 2; public function Tank():void { addEventListener(Event.ADDED_TO_STAGE,stageAddHandler); addEventListener(Event.ENTER_FRAME, enterFrameHandler); } private function stageAddHandler(e:Event):void { stage.addEventListener(KeyboardEvent.KEY_DOWN,checkKeys); stage.addEventListener(KeyboardEvent.KEY_UP,keyUps); removeEventListener(Event.ADDED_TO_STAGE,stageAddHandler); } public function checkKeys(event:KeyboardEvent):void { if(event.keyCode == 32) { //trace("Spacebar is down"); shooting = true; } if(event.keyCode == 39) { //trace("Right key is down"); right = true; } if(event.keyCode == 38) { //trace("Up key is down"); // lol up = true; } if(event.keyCode == 37) { //trace("Left key is down"); left = true; } if(event.keyCode == 40) { //trace("Down key is down"); down = true; } } public function keyUps(event:KeyboardEvent):void { if(event.keyCode == 32) { event.keyCode = 0; shooting = false; //trace("Spacebar is not down"); } if(event.keyCode == 39) { event.keyCode = 0; right = false; //trace("Right key is not down"); } if(event.keyCode == 38) { event.keyCode = 0; up = false; //trace("Up key is not down"); } if(event.keyCode == 37) { event.keyCode = 0; left = false; //trace("Left key is not down"); } if(event.keyCode == 40) { event.keyCode = 0; down = false; //trace("Down key is not down") // O.o } } public function checkDirectionPermissions(): void { if(this.y % GRID_SIZE < 5 || GRID_SIZE - this.y % GRID_SIZE < 5) { horAllowed = true; } else { horAllowed = false; } if(this.x % GRID_SIZE < 5 || GRID_SIZE - this.x % GRID_SIZE < 5) { vertAllowed = true; } else { vertAllowed = false; } if(!horAllowed && !vertAllowed) { realign(); } } public function realign():void { if(!horAllowed) { if(this.x % GRID_SIZE < GRID_SIZE / 2) { this.x -= this.x % GRID_SIZE; } else { this.x += (GRID_SIZE - this.x % GRID_SIZE); } } if(!vertAllowed) { if(this.y % GRID_SIZE < GRID_SIZE / 2) { this.y -= this.y % GRID_SIZE; } else { this.y += (GRID_SIZE - this.y % GRID_SIZE); } } } public function enterFrameHandler(Event):void { //trace(shot_timer); if(shot_timer > 0) { shot_timer--; } movement(); firing(); } public function firing():void { if(shooting) { if(shot_timer == 0) { shoot(); shot_timer = 10; } } } public function shoot():void { var bullet = new Bullet(); bullet.facing = facing; //0 - up, 1 - left, 2 - down, 3 - right switch(facing) { case 0: bullet.x = this.x; bullet.y = this.y - this.height / 2; break; case 1: bullet.x = this.x - this.width / 2; bullet.y = this.y; break; case 2: bullet.x = this.x; bullet.y = this.y + this.height / 2; break; case 3: bullet.x = this.x + this.width / 2; bullet.y = this.y; break; } (parent as MovieClip).addChild(bullet); } public function movement():void { //0 - up, 1 - left, 2 - down, 3 - right checkDirectionPermissions(); if(horAllowed) { if(right) { orient(3); realign(); this.x += speed; } if(left) { orient(1); realign(); this.x -= speed; } } if(vertAllowed) { if(up) { orient(0); realign(); this.y -= speed; } if(down) { orient(2); realign(); this.y += speed; } } } public function orient(dest:int):void { //trace("facing: " + facing); //trace("dest: " + dest); var angle = facing - dest; this.rotation += (90 * angle); facing = dest; } } }

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  • Creating nested bullet list in powerpoint 2007

    - by SuperBloup
    We're trying to create a powerpoint slide programmaticaly. We can obtain bullets on a single level, but playing with tabs and line returns doesn't work for nested enumerations. For now we got : text 1     subtext1     subtext2 text 2 And what we want is : text 1 subtext1 subtext2 text 2 Is there a way to control these using C# or VBA?

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  • Object array updates one instance repeatedly [on hold]

    - by MGN001
    I'm making a 2D shooter, and the player object holds an array of bullets that represent how many shots the player can have on screen at once. At least, this is what I'm trying for. What's happening is that each time any of the objects in the array is called, it seems to update a single object in memory. So, if I fire and then fire again, the object "starts over" from where I shot from and moves twice as fast. I've spent weeks trying to fix this and I've managed nothing. Hopefully another pair of eyes will see something I've missed. Player.cpp #include "Player.h" const int startLives = 3; const int maxHealth = 2; const float speed = 1; const int maxVelocity = 500; const int topBound = WINDOW_HEIGHT / 5 * 3; const int slowRate = 500; const int accRate = 1000; const int maxBullets = 5; const float spriteWidth = 99; const float spriteHeight = 75; const Vector2f startPosition = { (WINDOW_WIDTH / 2) - (spriteWidth / 2), (WINDOW_HEIGHT / 4 * 3) - (spriteHeight / 2) }; Bullet bullets[maxBullets]; Bullet * bulletPointers[maxBullets]; SDL_Texture * playerHealthy; SDL_Texture * playerDamaged; SDL_Texture * currentSprite; SDL_Rect * rect; Vector2f position; Vector2f velocity; int Health; int Lives; Player::Player() { rect = new SDL_Rect(); } Player::~Player() { SDL_DestroyTexture(playerHealthy); SDL_DestroyTexture(playerDamaged); SDL_DestroyTexture(currentSprite); rect = NULL; } void Player::Initialize(SDL_Renderer * renderer) { SDL_Surface * temp; temp = IMG_Load(".\\Sprites\\player.png"); if (temp == NULL) { printf("Initialization Error: %s\n", IMG_GetError()); exit(PLAYER_INITIALIZATION_ERROR); } playerHealthy = SDL_CreateTextureFromSurface(renderer, temp); temp = IMG_Load(".\\Sprites\\playerDamaged.png"); if (temp == NULL) { printf("Initialization Error: %s\n", IMG_GetError()); exit(PLAYER_INITIALIZATION_ERROR); } playerDamaged = SDL_CreateTextureFromSurface(renderer, temp); temp = IMG_Load(".\\Sprites\\laserGreen.png"); if (temp == NULL) { printf("Initialization Error: %s\n", IMG_GetError()); exit(PLAYER_INITIALIZATION_ERROR); } SDL_Texture * bullet = SDL_CreateTextureFromSurface(renderer, temp); temp = IMG_Load(".\\Sprites\\laserGreenShot.png"); if (temp == NULL) { printf("Initialization Error: %s\n", IMG_GetError()); exit(PLAYER_INITIALIZATION_ERROR); } SDL_Texture * explosion = SDL_CreateTextureFromSurface(renderer, temp); for (int i = 0; i < maxBullets; i++) { bullets[i].Initialize(renderer, bullet, explosion); bulletPointers[i] = NULL; } temp = NULL; rect->h = spriteHeight; rect->w = spriteWidth; Reset(); } void Player::Update(Input input, float deltaTime) { if (abs(velocity.x) < slowRate * deltaTime) { velocity.x = 0; } else if (velocity.x > 0) { velocity.x -= slowRate * deltaTime; } else if (velocity.x < 0) { velocity.x += slowRate * deltaTime; } if (abs(velocity.y) < slowRate * deltaTime) { velocity.y = 0; } if (velocity.y > 0) { velocity.y -= slowRate * deltaTime; } else if (velocity.y < 0) { velocity.y += slowRate * deltaTime; } if (Health <= 0) { --Lives; Spawn(); } velocity.x += UnitVector(input.InputNew.movement).x * accRate * deltaTime; velocity.y += UnitVector(input.InputNew.movement).y * accRate * deltaTime; if (Magnitude(velocity) > maxVelocity) { velocity.x = UnitVector(velocity).x * maxVelocity; velocity.y = UnitVector(velocity).y * maxVelocity; } position.x += velocity.x * deltaTime * speed; position.y += velocity.y * deltaTime * speed; if (input.InputNew.JumpLeft && !input.InputOld.JumpLeft) { position.x -= spriteWidth; } if (input.InputNew.JumpRight && !input.InputOld.JumpRight) { position.x += spriteWidth; } Boundaries(); rect->x = position.x; rect->y = position.y; if (input.InputNew.Fire && !input.InputOld.Fire) { Fire(); } for (int i = 0; i < maxBullets; ++i) { if (bulletPointers[i] != NULL) { bullets[i].Update(deltaTime); if (bullets[i].getPosition().y < -33) { bulletPointers[i] = NULL; } } } } void Player::Draw(SDL_Renderer * renderer) { for (int i = 0; i < maxBullets; ++i) { if (bulletPointers[i] != NULL) { bullets[i].Draw(renderer); } } SDL_RenderCopy(renderer, currentSprite, NULL, rect); } void Player::Spawn() { position = startPosition; Health = maxHealth; currentSprite = playerHealthy; rect->x = position.x; rect->y = position.y; } void Player::Boundaries() { if (position.x < 0) { position.x = 0; velocity.x *= -1; } else if (position.x > WINDOW_WIDTH - spriteWidth) { position.x = WINDOW_WIDTH - spriteWidth; velocity.x *= -1; } if (position.y < topBound) { position.y = topBound; velocity.y *= -1; } else if (position.y > WINDOW_HEIGHT - spriteHeight) { position.y = WINDOW_HEIGHT - spriteHeight; velocity.y *= -1; } } int Player::getLives() { return Lives; } void Player::Reset() { Lives = startLives; Spawn(); } void Player::Fire() { for (int i = 0; i < maxBullets; ++i) { if (bulletPointers[i] == NULL) { bulletPointers[i] = &bullets[i]; bullets[i].Fire(position,velocity.x/2); break; } } } Bullet.cpp #include "Bullet.h" const int speed = 500; Vector2f bulletVelocity; float ExplosionMax = 0.5f; float ExplosionTimer; const Vector2f fireOffset = { 45.5f, 10.0f }; const Vector2f explosionOffset = { 23.5f, -27.0f }; const Vector2i bulletSize = { 9, 33 }; const Vector2i explosionSize = { 56, 54 }; Vector2f bulletPosition; SDL_Texture * bulletSprite; SDL_Texture * explosionSprite; SDL_Texture * bulletCurrentSprite; SDL_Rect * bulletRect; Bullet::Bullet() { } Bullet::~Bullet() { } void Bullet::Initialize(SDL_Renderer * renderer, SDL_Texture * bullet, SDL_Texture * explosion) { bulletSprite = bullet; explosionSprite = explosion; bulletRect = new SDL_Rect(); } void Bullet::Update(float deltaTime) { bulletPosition.y -= bulletVelocity.y * deltaTime; bulletPosition.x += bulletVelocity.x * deltaTime; bulletRect->x = static_cast<int>(bulletPosition.x); bulletRect->y = static_cast<int>(bulletPosition.y); } void Bullet::Draw(SDL_Renderer * renderer) { SDL_RenderCopy(renderer, bulletCurrentSprite, NULL, bulletRect); } void Bullet::Fire(Vector2f pos, float xSpeed) { bulletPosition.x = pos.x + fireOffset.x; bulletPosition.y = pos.y + fireOffset.y; bulletVelocity.x = xSpeed; bulletVelocity.y = speed; bulletCurrentSprite = bulletSprite; bulletRect->h = bulletSize.y; bulletRect->w = bulletSize.x; bulletRect->x = static_cast<int>(bulletPosition.x); bulletRect->y = static_cast<int>(bulletPosition.y); } Vector2f Bullet::getPosition() { return bulletPosition; } void Bullet::Hit() { bulletCurrentSprite = explosionSprite; bulletVelocity = { 0.0f, 0.0f }; ExplosionTimer = ExplosionMax; bulletPosition.x += explosionOffset.x; bulletPosition.y += explosionOffset.y; bulletRect->w = explosionSize.x; bulletRect->h = explosionSize.y; }

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  • Why does the heat production increase as the clockrate of a CPU increases?

    - by Nils
    This is probably a bit off-topic, but the whole multi-core debate got me thinking. It's much easier to produce two cores (in one package) then speeding up one core by a factor of two. Why exactly is this? I googled a bit, but found mostly very imprecise answers from over clocking boards which do not explain the underlying Physics. The voltage seems to have the most impact (quadratic), but do I need to run a CPU at higher voltage if I want a faster clock rate? Also I like to know why exactly (and how much) heat a semiconductor circuit produces when it runs at a certain clock speed.

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  • Ball to Ball Collision - Detection and Handling

    - by Simucal
    With the help of the Stack Overflow community I've written a pretty basic-but fun physics simulator. You click and drag the mouse to launch a ball. It will bounce around and eventually stop on the "floor". My next big feature I want to add in is ball to ball collision. The ball's movement is broken up into a x and y speed vector. I have gravity (small reduction of the y vector each step), I have friction (small reduction of both vectors each collision with a wall). The balls honestly move around in a surprisingly realistic way. I guess my question has two parts: What is the best method to detect ball to ball collision? Do I just have an O(n^2) loop that iterates over each ball and checks every other ball to see if it's radius overlaps? What equations do I use to handle the ball to ball collisions? Physics 101 How does it effect the two balls speed x/y vectors? What is the resulting direction the two balls head off in? How do I apply this to each ball? Handling the collision detection of the "walls" and the resulting vector changes were easy but I see more complications with ball-ball collisions. With walls I simply had to take the negative of the appropriate x or y vector and off it would go in the correct direction. With balls I don't think it is that way. Some quick clarifications: for simplicity I'm ok with a perfectly elastic collision for now, also all my balls have the same mass right now, but I might change that in the future. In case anyone is interested in playing with the simulator I have made so far, I've uploaded the source here (EDIT: Check the updated source below). Edit: Resources I have found useful 2d Ball physics with vectors: 2-Dimensional Collisions Without Trigonometry.pdf 2d Ball collision detection example: Adding Collision Detection Success! I have the ball collision detection and response working great! Relevant code: Collision Detection: for (int i = 0; i < ballCount; i++) { for (int j = i + 1; j < ballCount; j++) { if (balls[i].colliding(balls[j])) { balls[i].resolveCollision(balls[j]); } } } This will check for collisions between every ball but skip redundant checks (if you have to check if ball 1 collides with ball 2 then you don't need to check if ball 2 collides with ball 1. Also, it skips checking for collisions with itself). Then, in my ball class I have my colliding() and resolveCollision() methods: public boolean colliding(Ball ball) { float xd = position.getX() - ball.position.getX(); float yd = position.getY() - ball.position.getY(); float sumRadius = getRadius() + ball.getRadius(); float sqrRadius = sumRadius * sumRadius; float distSqr = (xd * xd) + (yd * yd); if (distSqr <= sqrRadius) { return true; } return false; } public void resolveCollision(Ball ball) { // get the mtd Vector2d delta = (position.subtract(ball.position)); float d = delta.getLength(); // minimum translation distance to push balls apart after intersecting Vector2d mtd = delta.multiply(((getRadius() + ball.getRadius())-d)/d); // resolve intersection -- // inverse mass quantities float im1 = 1 / getMass(); float im2 = 1 / ball.getMass(); // push-pull them apart based off their mass position = position.add(mtd.multiply(im1 / (im1 + im2))); ball.position = ball.position.subtract(mtd.multiply(im2 / (im1 + im2))); // impact speed Vector2d v = (this.velocity.subtract(ball.velocity)); float vn = v.dot(mtd.normalize()); // sphere intersecting but moving away from each other already if (vn > 0.0f) return; // collision impulse float i = (-(1.0f + Constants.restitution) * vn) / (im1 + im2); Vector2d impulse = mtd.multiply(i); // change in momentum this.velocity = this.velocity.add(impulse.multiply(im1)); ball.velocity = ball.velocity.subtract(impulse.multiply(im2)); } Source Code: Complete source for ball to ball collider. Binary: Compiled binary in case you just want to try bouncing some balls around. If anyone has some suggestions for how to improve this basic physics simulator let me know! One thing I have yet to add is angular momentum so the balls will roll more realistically. Any other suggestions? Leave a comment!

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  • PhysX for massive performance via GPU ?

    - by devdude
    I recently compared some of the physics engine out there for simulation and game development. Some are free, some are opensource, some are commercial (1 is even very commercial $$$$). Havok, Ode, Newton (aka oxNewton), Bullet, PhysX and "raw" build-in physics in some 3D engines. At some stage I came to conclusion or question: Why should I use anything but NVidia PhysX if I can make use of its amazing performance (if I need it) due to GPU processing ? With future NVidia cards I can expect further improvement independent of the regular CPU generation steps. The SDK is free and it is available for Linux as well. Of course it is a bit of vendor lock-in and it is not opensource. Whats your view or experience ? If you would start right now with development, would you agree with the above ? cheers

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  • AndEngine Physics Editor loading level

    - by Khawar Raza
    I have created a .pes file using PhysicsEditor and imported as xml and have added to my project. When I parsed it and created bodies, it is showing strange behavior. The mapping of bodies that I created in PhysicsEditor is totally different what I see in my application means the shapes I draw in PhysicsEditor are rendering differently in my app. Here is my xml and code to parse and add bodies to scene. PhysicsEditor XML file: <?xml version="1.0" encoding="UTF-8"?> <!-- created with http://www.physicseditor.de --> <bodydef version="1.0"> <bodies numBodies="1"> <body name="car_path" dynamic="false" numFixtures="1"> <fixture density="2" friction="1" restitution="0" filter_categoryBits="1" filter_groupIndex="0" filter_maskBits="65535" isSensor="false" type="POLYGON" numPolygons="20" > <polygon numVertexes="6"> <vertex x="277.0000" y="152.0000" /> <vertex x="356.0000" y="172.0000" /> <vertex x="413.0000" y="194.0000" /> <vertex x="476.0000" y="223.0000" /> <vertex x="173.0000" y="232.0000" /> <vertex x="174.0000" y="148.0000" /> </polygon> <polygon numVertexes="4"> <vertex x="1556.0000" y="221.0000" /> <vertex x="1142.0000" y="94.0000" /> <vertex x="1255.0000" y="-15.0000" /> <vertex x="1554.0000" y="-14.0000" /> </polygon> <polygon numVertexes="3"> <vertex x="-192.0000" y="177.0000" /> <vertex x="-888.0000" y="139.0000" /> <vertex x="-549.0000" y="-125.0000" /> </polygon> <polygon numVertexes="6"> <vertex x="1762.0000" y="24.0000" /> <vertex x="1862.0000" y="27.0000" /> <vertex x="1927.0000" y="68.0000" /> <vertex x="2078.0000" y="222.0000" /> <vertex x="1643.0000" y="212.0000" /> <vertex x="1642.0000" y="38.0000" /> </polygon> <polygon numVertexes="3"> <vertex x="-1150.0000" y="146.0000" /> <vertex x="-1776.0000" y="140.0000" /> <vertex x="-1476.0000" y="-25.0000" /> </polygon> <polygon numVertexes="4"> <vertex x="-2799.0000" y="103.0000" /> <vertex x="-2684.0000" y="223.0000" /> <vertex x="-3112.0000" y="256.0000" /> <vertex x="-3108.0000" y="98.0000" /> </polygon> <polygon numVertexes="3"> <vertex x="3112.0000" y="255.0000" /> <vertex x="2422.0000" y="222.0000" /> <vertex x="3120.0000" y="-71.0000" /> </polygon> <polygon numVertexes="4"> <vertex x="1142.0000" y="94.0000" /> <vertex x="1556.0000" y="221.0000" /> <vertex x="709.0000" y="226.0000" /> <vertex x="911.0000" y="93.0000" /> </polygon> <polygon numVertexes="6"> <vertex x="-2111.0000" y="89.0000" /> <vertex x="-2067.0000" y="94.0000" /> <vertex x="-2002.0000" y="139.0000" /> <vertex x="-2344.0000" y="223.0000" /> <vertex x="-2196.0000" y="112.0000" /> <vertex x="-2153.0000" y="91.0000" /> </polygon> <polygon numVertexes="4"> <vertex x="105.0000" y="233.0000" /> <vertex x="-94.0000" y="178.0000" /> <vertex x="69.0000" y="106.0000" /> <vertex x="91.0000" y="104.0000" /> </polygon> <polygon numVertexes="3"> <vertex x="-2002.0000" y="139.0000" /> <vertex x="-2067.0000" y="94.0000" /> <vertex x="-2032.0000" y="110.0000" /> </polygon> <polygon numVertexes="4"> <vertex x="-1150.0000" y="146.0000" /> <vertex x="105.0000" y="233.0000" /> <vertex x="-2344.0000" y="223.0000" /> <vertex x="-2002.0000" y="139.0000" /> </polygon> <polygon numVertexes="3"> <vertex x="413.0000" y="194.0000" /> <vertex x="356.0000" y="172.0000" /> <vertex x="376.0000" y="176.0000" /> </polygon> <polygon numVertexes="3"> <vertex x="105.0000" y="233.0000" /> <vertex x="-192.0000" y="177.0000" /> <vertex x="-94.0000" y="178.0000" /> </polygon> <polygon numVertexes="4"> <vertex x="105.0000" y="233.0000" /> <vertex x="-1150.0000" y="146.0000" /> <vertex x="-888.0000" y="139.0000" /> <vertex x="-192.0000" y="177.0000" /> </polygon> <polygon numVertexes="3"> <vertex x="3112.0000" y="255.0000" /> <vertex x="-3112.0000" y="256.0000" /> <vertex x="-2684.0000" y="223.0000" /> </polygon> <polygon numVertexes="3"> <vertex x="3112.0000" y="255.0000" /> <vertex x="1556.0000" y="221.0000" /> <vertex x="1643.0000" y="212.0000" /> </polygon> <polygon numVertexes="3"> <vertex x="709.0000" y="226.0000" /> <vertex x="173.0000" y="232.0000" /> <vertex x="476.0000" y="223.0000" /> </polygon> <polygon numVertexes="3"> <vertex x="3112.0000" y="255.0000" /> <vertex x="2078.0000" y="222.0000" /> <vertex x="2422.0000" y="222.0000" /> </polygon> <polygon numVertexes="3"> <vertex x="3112.0000" y="255.0000" /> <vertex x="105.0000" y="233.0000" /> <vertex x="173.0000" y="232.0000" /> </polygon> </fixture> </body> </bodies> <metadata> <format>1</format> <ptm_ratio></ptm_ratio> </metadata> </bodydef> And here is my code: private void loadLevel() { // TODO Auto-generated method stub AssetManager assetManager = getAssets(); try { InputStream stream = assetManager.open("tmx/path1.xml"); if(stream != null) { try { DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance(); dbf.setValidating(false); dbf.setIgnoringComments(false); dbf.setIgnoringElementContentWhitespace(true); dbf.setNamespaceAware(true); DocumentBuilder db = null; db = dbf.newDocumentBuilder(); Document document = db.parse(stream); Element root = document.getDocumentElement(); NodeList bodiesNodeList = root.getElementsByTagName("bodies"); for(int i = 0; i < bodiesNodeList.getLength(); i++) { BodyDef bodyDef = new BodyDef(); bodyDef.type = BodyType.StaticBody; bodyDef.fixedRotation = true; Element bodiesElement = (Element)bodiesNodeList.item(i); NodeList bodyList = bodiesElement.getElementsByTagName("body"); for(int j = 0; j < bodyList.getLength(); j++) { Element bodyElement = (Element)bodyList.item(j); Body body = mPhysicsWorld.createBody(bodyDef); NodeList fixtureList = bodyElement.getElementsByTagName("fixture"); for(int k = 0; k < fixtureList.getLength(); k++) { Element fixtureElement = (Element)fixtureList.item(k); FixtureDef fixtureDef = new FixtureDef(); if(fixtureElement != null) { String density = fixtureElement.getAttribute("density"); String friction = fixtureElement.getAttribute("friction"); String restitution = fixtureElement.getAttribute("restitution"); fixtureDef = PhysicsFactory.createFixtureDef(Float.parseFloat(density), Float.parseFloat(friction), Float.parseFloat(restitution)); } NodeList polygonList = fixtureElement.getElementsByTagName("polygon"); if(polygonList != null && polygonList.getLength() > 0) { for(int m = 0; m < polygonList.getLength(); m++) { PolygonShape polyShape = new PolygonShape(); Element polygonElement = (Element)polygonList.item(m); NodeList vertexList = polygonElement.getElementsByTagName("vertex"); if(vertexList != null && vertexList.getLength() > 0) { Vector2 [] vectors = new Vector2[vertexList.getLength()]; for(int n = 0; n < vertexList.getLength(); n++) { Element vertexElement = (Element)vertexList.item(n); if(vertexElement != null) { float x = Float.parseFloat(vertexElement.getAttribute("x")); float y = Float.parseFloat(vertexElement.getAttribute("y")); vectors[n] = new Vector2(x/PIXEL_TO_METER_RATIO_DEFAULT, y/PIXEL_TO_METER_RATIO_DEFAULT); } } polyShape.set(vectors); fixtureDef.shape = polyShape; } body.createFixture(fixtureDef); } } } mScene.attachChild(bgSprite); mPhysicsWorld.registerPhysicsConnector(new PhysicsConnector(bgSprite, body, false, false)); } } } catch(Exception e) { e.printStackTrace(); } } } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } Any idea where I am going wrong?

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  • Chipmunk physics: Velocity question

    - by Johannes Jensen
    I'm making an iPhone game where the main actor is a ball that rolls depending on the device's accelerometer rotation. I haven't started on this part of the coding yet, but I was wondering if you guys had a nice way of solving this: I tried looking a little into chipmunk, and I noticed that bodies have the property v, which is a point containing x and y velocities. I was thinking it'd be a bad idea to just do like: playerBody->v = ccp(accelerometer.x * 5, playerBody->v.y); because it'd just roll up of walls and stuff, is there a better solution to do this?

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  • Using Accelerometer in Wiimote for Physics Practicals

    - by Omar
    I have to develop some software in my school to utilize the accelerometer in the Wiimote for recording data from experiments, for example finding the acceleration and velocity of a moving object. I understand how the accelerometer values will be used but I am sort of stuck on the programming front. There is a set of things that I would like to do: Live streaming of data from the Wiimote via bluetooth Use the accelerometer values to find velocity and displacment via integration Plot a set of results Avoid the use of the infrared sensor on the Wiimote Please can anyone give me their thoughts on how to go about this. Also it would be great if people could direct me to existing projects that utizlise the wiimote. Also can someone suggest what would be the best programming language to use for this. My current bet is on using Visual basic. Any sort of help is greatly appretiated.

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  • Solve Physics exercise by brute force approach..

    - by Nils
    Being unable to reproduce a given result. (either because it's wrong or because I was doing something wrong) I was asking myself if it would be easy to just write a small program which takes all the constants and given number and permutes it with a possible operators (* / - + exp(..)) etc) until the result is found. Permutations of n distinct objects with repetition allowed is n^r. At least as long as r is small I think you should be able to do this. I wonder if anybody did something similar here..

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  • Word 2003: Bullet style renamed; is there some way to reverse this?

    - by Margaret
    I have a machine that seems to have had its bullet style permanently changed - I previously was creating a document which had a question/answer format, where the answers were bullet points, so I created a style for them. The problem is, it seems to have stuck. If you click the "Bullet" button, the paragraph is formatted in the style. I've tried deleting the style in Normal.dot, and even deleting the Normal.dot file in the entirely - neither seems to fix the problem. Anyone have any other bright ideas on how to fix it?

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  • How do you make a bullet ricochet off a vertical wall?

    - by Bagofsheep
    First things first. I am using C# with XNA. My game is top-down and the player can shoot bullets. I've managed to get the bullets to ricochet correctly off horizontal walls. Yet, despite using similar methods (e.g. http://stackoverflow.com/questions/3203952/mirroring-an-angle) and reading other answered questions about this subject I have not been able to get the bullets to ricochet off a vertical wall correctly. Any method I've tried has failed and sometimes made ricocheting off a horizontal wall buggy. Here is the collision code that calls the ricochet method: //Loop through returned tile rectangles from quad tree to test for wall collision. If a collision occurs perform collision logic. for (int r = 0; r < returnObjects.Count; r++) if (Bullets[i].BoundingRectangle.Intersects(returnObjects[r])) Bullets[i].doCollision(returnObjects[r]); Now here is the code for the doCollision method. public void doCollision(Rectangle surface) { if (Ricochet) doRicochet(surface); else Trash = true; } Finally, here is the code for the doRicochet method. public void doRicochet(Rectangle surface) { if (Position.X > surface.Left && Position.X < surface.Right) { //Mirror the bullet's angle. Rotation = -1 * Rotation; //Moves the bullet in the direction of its rotation by given amount. moveFaceDirection(Sprite.Width * BulletScale.X); } else if (Position.Y > surface.Top && Position.Y < surface.Bottom) { } } Since I am only dealing with vertical and horizontal walls at the moment, the if statements simply determine if the object is colliding from the right or left, or from the top or bottom. If the object's X position is within the boundaries of the tile's X boundaries (left and right sides), it must be colliding from the top, and vice verse. As you can see, the else if statement is empty and is where the correct code needs to go.

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