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• best way to compute vertex normals from a Triangle's list

  - by nkint

  hi i'm a complete newbie in computergraphics so sorry if it's a stupid answer. i'm trying to make a simple 3d engine from scratch, more for educational purpose than for real use. i have a Surface object with inside a Triangle's list. For now i compute normals inside Triangle class, in this way: triangle.computeFaceNormals() { Vec3D u = v1.sub(v3) Vec3D v = v1.sub(v2) Vec3D normal = Vec3D.cross(u,v) normal.normalized() this.n1 = this.n2 = this.n3 = normal } and when building surface: t = new Triangle(v1,v2,v3).computeFaceNormals() surface.addTriangle(t) and i think this is the best way to do that.. isn't it? now.. what about for vertex normals? i've found this simple algorithm: flipcode vertex normal but.. hei this algorithm has.. exponential complexity? (if my memory doesn't fail my computer science background..) (bytheway.. it has 3 nested loops.. i don't think it's the best way to do it..) any suggestion?

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• Open Source AI Bot interfaces

  - by David Young

  What are some open source AI Bot interfaces? Similar to Pogamut 3 GameBots2004 for custom Unreal Tournament bots or Brood Wars API for Starcraft bots etc. If you could please post one AI bot interface per answer (make sure to provide a link) and give a brief summary as to the content of the blog posts. Please include what type of bot interface structure it is, client/server, server/server, etc e.g. BWAPI is client/server which emulates a real player

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• Ball bouncing at a certain angle and efficiency computations

  - by X Y

  I would like to make a pong game with a small twist (for now). Every time the ball bounces off one of the paddles i want it to be under a certain angle (between a min and a max). I simply can't wrap my head around how to actually do it (i have some thoughts and such but i simply cannot implement them properly - i feel i'm overcomplicating things). Here's an image with a small explanation . One other problem would be that the conditions for bouncing have to be different for every edge. For example, in the picture, on the two small horizontal edges i do not want a perfectly vertical bounce when in the middle of the edge but rather a constant angle (pi/4 maybe) in either direction depending on the collision point (before the middle of the edge, or after). All of my collisions are done with the Separating Axes Theorem (and seem to work fine). I'm looking for something efficient because i want to add a lot of things later on (maybe polygons with many edges and such). So i need to keep to a minimum the amount of checking done every frame. The collision algorithm begins testing whenever the bounding boxes of the paddle and the ball intersect. Is there something better to test for possible collisions every frame? (more efficient in the long run,with many more objects etc, not necessarily easy to code). I'm going to post the code for my game: Paddle Class public class Paddle : Microsoft.Xna.Framework.DrawableGameComponent { #region Private Members private SpriteBatch spriteBatch; private ContentManager contentManager; private bool keybEnabled; private bool isLeftPaddle; private Texture2D paddleSprite; private Vector2 paddlePosition; private float paddleSpeedY; private Vector2 paddleScale = new Vector2(1f, 1f); private const float DEFAULT_Y_SPEED = 150; private Vector2[] Normals2Edges; private Vector2[] Vertices = new Vector2[4]; private List<Vector2> lst = new List<Vector2>(); private Vector2 Edge; #endregion #region Properties public float Speed { get {return paddleSpeedY; } set { paddleSpeedY = value; } } public Vector2[] Normal2EdgesVector { get { NormalsToEdges(this.isLeftPaddle); return Normals2Edges; } } public Vector2[] VertexVector { get { return Vertices; } } public Vector2 Scale { get { return paddleScale; } set { paddleScale = value; NormalsToEdges(this.isLeftPaddle); } } public float X { get { return paddlePosition.X; } set { paddlePosition.X = value; } } public float Y { get { return paddlePosition.Y; } set { paddlePosition.Y = value; } } public float Width { get { return (Scale.X == 1f ? (float)paddleSprite.Width : paddleSprite.Width * Scale.X); } } public float Height { get { return ( Scale.Y==1f ? (float)paddleSprite.Height : paddleSprite.Height*Scale.Y ); } } public Texture2D GetSprite { get { return paddleSprite; } } public Rectangle Boundary { get { return new Rectangle((int)paddlePosition.X, (int)paddlePosition.Y, (int)this.Width, (int)this.Height); } } public bool KeyboardEnabled { get { return keybEnabled; } } #endregion private void NormalsToEdges(bool isLeftPaddle) { Normals2Edges = null; Edge = Vector2.Zero; lst.Clear(); for (int i = 0; i < Vertices.Length; i++) { Edge = Vertices[i + 1 == Vertices.Length ? 0 : i + 1] - Vertices[i]; if (Edge != Vector2.Zero) { Edge.Normalize(); //outer normal to edge !! (origin in top-left) lst.Add(new Vector2(Edge.Y, -Edge.X)); } } Normals2Edges = lst.ToArray(); } public float[] ProjectPaddle(Vector2 axis) { if (Vertices.Length == 0 || axis == Vector2.Zero) return (new float[2] { 0, 0 }); float min, max; min = Vector2.Dot(axis, Vertices[0]); max = min; for (int i = 1; i < Vertices.Length; i++) { float p = Vector2.Dot(axis, Vertices[i]); if (p < min) min = p; else if (p > max) max = p; } return (new float[2] { min, max }); } public Paddle(Game game, bool isLeftPaddle, bool enableKeyboard = true) : base(game) { contentManager = new ContentManager(game.Services); keybEnabled = enableKeyboard; this.isLeftPaddle = isLeftPaddle; } public void setPosition(Vector2 newPos) { X = newPos.X; Y = newPos.Y; } public override void Initialize() { base.Initialize(); this.Speed = DEFAULT_Y_SPEED; X = 0; Y = 0; NormalsToEdges(this.isLeftPaddle); } protected override void LoadContent() { spriteBatch = new SpriteBatch(GraphicsDevice); paddleSprite = contentManager.Load<Texture2D>(@"Content\pongBar"); } public override void Update(GameTime gameTime) { //vertices array Vertices[0] = this.paddlePosition; Vertices[1] = this.paddlePosition + new Vector2(this.Width, 0); Vertices[2] = this.paddlePosition + new Vector2(this.Width, this.Height); Vertices[3] = this.paddlePosition + new Vector2(0, this.Height); // Move paddle, but don't allow movement off the screen if (KeyboardEnabled) { float moveDistance = Speed * (float)gameTime.ElapsedGameTime.TotalSeconds; KeyboardState newKeyState = Keyboard.GetState(); if (newKeyState.IsKeyDown(Keys.Down) && Y + paddleSprite.Height + moveDistance <= Game.GraphicsDevice.Viewport.Height) { Y += moveDistance; } else if (newKeyState.IsKeyDown(Keys.Up) && Y - moveDistance >= 0) { Y -= moveDistance; } } else { if (this.Y + this.Height > this.GraphicsDevice.Viewport.Height) { this.Y = this.Game.GraphicsDevice.Viewport.Height - this.Height - 1; } } base.Update(gameTime); } public override void Draw(GameTime gameTime) { spriteBatch.Begin(SpriteSortMode.Texture,null); spriteBatch.Draw(paddleSprite, paddlePosition, null, Color.White, 0f, Vector2.Zero, Scale, SpriteEffects.None, 0); spriteBatch.End(); base.Draw(gameTime); } } Ball Class public class Ball : Microsoft.Xna.Framework.DrawableGameComponent { #region Private Members private SpriteBatch spriteBatch; private ContentManager contentManager; private const float DEFAULT_SPEED = 50; private float speedIncrement = 0; private Vector2 ballScale = new Vector2(1f, 1f); private const float INCREASE_SPEED = 50; private Texture2D ballSprite; //initial texture private Vector2 ballPosition; //position private Vector2 centerOfBall; //center coords private Vector2 ballSpeed = new Vector2(DEFAULT_SPEED, DEFAULT_SPEED); //speed #endregion #region Properties public float DEFAULTSPEED { get { return DEFAULT_SPEED; } } public Vector2 ballCenter { get { return centerOfBall; } } public Vector2 Scale { get { return ballScale; } set { ballScale = value; } } public float SpeedX { get { return ballSpeed.X; } set { ballSpeed.X = value; } } public float SpeedY { get { return ballSpeed.Y; } set { ballSpeed.Y = value; } } public float X { get { return ballPosition.X; } set { ballPosition.X = value; } } public float Y { get { return ballPosition.Y; } set { ballPosition.Y = value; } } public Texture2D GetSprite { get { return ballSprite; } } public float Width { get { return (Scale.X == 1f ? (float)ballSprite.Width : ballSprite.Width * Scale.X); } } public float Height { get { return (Scale.Y == 1f ? (float)ballSprite.Height : ballSprite.Height * Scale.Y); } } public float SpeedIncreaseIncrement { get { return speedIncrement; } set { speedIncrement = value; } } public Rectangle Boundary { get { return new Rectangle((int)ballPosition.X, (int)ballPosition.Y, (int)this.Width, (int)this.Height); } } #endregion public Ball(Game game) : base(game) { contentManager = new ContentManager(game.Services); } public void Reset() { ballSpeed.X = DEFAULT_SPEED; ballSpeed.Y = DEFAULT_SPEED; ballPosition.X = Game.GraphicsDevice.Viewport.Width / 2 - ballSprite.Width / 2; ballPosition.Y = Game.GraphicsDevice.Viewport.Height / 2 - ballSprite.Height / 2; } public void SpeedUp() { if (ballSpeed.Y < 0) ballSpeed.Y -= (INCREASE_SPEED + speedIncrement); else ballSpeed.Y += (INCREASE_SPEED + speedIncrement); if (ballSpeed.X < 0) ballSpeed.X -= (INCREASE_SPEED + speedIncrement); else ballSpeed.X += (INCREASE_SPEED + speedIncrement); } public float[] ProjectBall(Vector2 axis) { if (axis == Vector2.Zero) return (new float[2] { 0, 0 }); float min, max; min = Vector2.Dot(axis, this.ballCenter) - this.Width/2; //center - radius max = min + this.Width; //center + radius return (new float[2] { min, max }); } public void ChangeHorzDirection() { ballSpeed.X *= -1; } public void ChangeVertDirection() { ballSpeed.Y *= -1; } public override void Initialize() { base.Initialize(); ballPosition.X = Game.GraphicsDevice.Viewport.Width / 2 - ballSprite.Width / 2; ballPosition.Y = Game.GraphicsDevice.Viewport.Height / 2 - ballSprite.Height / 2; } protected override void LoadContent() { spriteBatch = new SpriteBatch(GraphicsDevice); ballSprite = contentManager.Load<Texture2D>(@"Content\ball"); } public override void Update(GameTime gameTime) { if (this.Y < 1 || this.Y > GraphicsDevice.Viewport.Height - this.Height - 1) this.ChangeVertDirection(); centerOfBall = new Vector2(ballPosition.X + this.Width / 2, ballPosition.Y + this.Height / 2); base.Update(gameTime); } public override void Draw(GameTime gameTime) { spriteBatch.Begin(); spriteBatch.Draw(ballSprite, ballPosition, null, Color.White, 0f, Vector2.Zero, Scale, SpriteEffects.None, 0); spriteBatch.End(); base.Draw(gameTime); } } Main game class public class gameStart : Microsoft.Xna.Framework.Game { GraphicsDeviceManager graphics; SpriteBatch spriteBatch; public gameStart() { graphics = new GraphicsDeviceManager(this); Content.RootDirectory = "Content"; this.Window.Title = "Pong game"; } protected override void Initialize() { ball = new Ball(this); paddleLeft = new Paddle(this,true,false); paddleRight = new Paddle(this,false,true); Components.Add(ball); Components.Add(paddleLeft); Components.Add(paddleRight); this.Window.AllowUserResizing = false; this.IsMouseVisible = true; this.IsFixedTimeStep = false; this.isColliding = false; base.Initialize(); } #region MyPrivateStuff private Ball ball; private Paddle paddleLeft, paddleRight; private int[] bit = { -1, 1 }; private Random rnd = new Random(); private int updates = 0; enum nrPaddle { None, Left, Right }; private nrPaddle PongBar = nrPaddle.None; private ArrayList Axes = new ArrayList(); private Vector2 MTV; //minimum translation vector private bool isColliding; private float overlap; //smallest distance after projections private Vector2 overlapAxis; //axis of overlap #endregion protected override void LoadContent() { spriteBatch = new SpriteBatch(GraphicsDevice); paddleLeft.setPosition(new Vector2(0, this.GraphicsDevice.Viewport.Height / 2 - paddleLeft.Height / 2)); paddleRight.setPosition(new Vector2(this.GraphicsDevice.Viewport.Width - paddleRight.Width, this.GraphicsDevice.Viewport.Height / 2 - paddleRight.Height / 2)); paddleLeft.Scale = new Vector2(1f, 2f); //scale left paddle } private bool ShapesIntersect(Paddle paddle, Ball ball) { overlap = 1000000f; //large value overlapAxis = Vector2.Zero; MTV = Vector2.Zero; foreach (Vector2 ax in Axes) { float[] pad = paddle.ProjectPaddle(ax); //pad0 = min, pad1 = max float[] circle = ball.ProjectBall(ax); //circle0 = min, circle1 = max if (pad[1] <= circle[0] || circle[1] <= pad[0]) { return false; } if (pad[1] - circle[0] < circle[1] - pad[0]) { if (Math.Abs(overlap) > Math.Abs(-pad[1] + circle[0])) { overlap = -pad[1] + circle[0]; overlapAxis = ax; } } else { if (Math.Abs(overlap) > Math.Abs(circle[1] - pad[0])) { overlap = circle[1] - pad[0]; overlapAxis = ax; } } } if (overlapAxis != Vector2.Zero) { MTV = overlapAxis * overlap; } return true; } protected override void Update(GameTime gameTime) { updates += 1; float ftime = 5 * (float)gameTime.ElapsedGameTime.TotalSeconds; if (updates == 1) { isColliding = false; int Xrnd = bit[Convert.ToInt32(rnd.Next(0, 2))]; int Yrnd = bit[Convert.ToInt32(rnd.Next(0, 2))]; ball.SpeedX = Xrnd * ball.SpeedX; ball.SpeedY = Yrnd * ball.SpeedY; ball.X += ftime * ball.SpeedX; ball.Y += ftime * ball.SpeedY; } else { updates = 100; ball.X += ftime * ball.SpeedX; ball.Y += ftime * ball.SpeedY; } //autorun :) paddleLeft.Y = ball.Y; //collision detection PongBar = nrPaddle.None; if (ball.Boundary.Intersects(paddleLeft.Boundary)) { PongBar = nrPaddle.Left; if (!isColliding) { Axes.Clear(); Axes.AddRange(paddleLeft.Normal2EdgesVector); //axis from nearest vertex to ball's center Axes.Add(FORMULAS.NormAxisFromCircle2ClosestVertex(paddleLeft.VertexVector, ball.ballCenter)); } } else if (ball.Boundary.Intersects(paddleRight.Boundary)) { PongBar = nrPaddle.Right; if (!isColliding) { Axes.Clear(); Axes.AddRange(paddleRight.Normal2EdgesVector); //axis from nearest vertex to ball's center Axes.Add(FORMULAS.NormAxisFromCircle2ClosestVertex(paddleRight.VertexVector, ball.ballCenter)); } } if (PongBar != nrPaddle.None && !isColliding) switch (PongBar) { case nrPaddle.Left: if (ShapesIntersect(paddleLeft, ball)) { isColliding = true; if (MTV != Vector2.Zero) ball.X += MTV.X; ball.Y += MTV.Y; ball.ChangeHorzDirection(); } break; case nrPaddle.Right: if (ShapesIntersect(paddleRight, ball)) { isColliding = true; if (MTV != Vector2.Zero) ball.X += MTV.X; ball.Y += MTV.Y; ball.ChangeHorzDirection(); } break; default: break; } if (!ShapesIntersect(paddleRight, ball) && !ShapesIntersect(paddleLeft, ball)) isColliding = false; ball.X += ftime * ball.SpeedX; ball.Y += ftime * ball.SpeedY; //check ball movement if (ball.X > paddleRight.X + paddleRight.Width + 2) { //IncreaseScore(Left); ball.Reset(); updates = 0; return; } else if (ball.X < paddleLeft.X - 2) { //IncreaseScore(Right); ball.Reset(); updates = 0; return; } base.Update(gameTime); } protected override void Draw(GameTime gameTime) { GraphicsDevice.Clear(Color.Aquamarine); spriteBatch.Begin(SpriteSortMode.BackToFront, BlendState.AlphaBlend); spriteBatch.End(); base.Draw(gameTime); } } And one method i've used: public static Vector2 NormAxisFromCircle2ClosestVertex(Vector2[] vertices, Vector2 circle) { Vector2 temp = Vector2.Zero; if (vertices.Length > 0) { float dist = (circle.X - vertices[0].X) * (circle.X - vertices[0].X) + (circle.Y - vertices[0].Y) * (circle.Y - vertices[0].Y); for (int i = 1; i < vertices.Length;i++) { if (dist > (circle.X - vertices[i].X) * (circle.X - vertices[i].X) + (circle.Y - vertices[i].Y) * (circle.Y - vertices[i].Y)) { temp = vertices[i]; //memorize the closest vertex dist = (circle.X - vertices[i].X) * (circle.X - vertices[i].X) + (circle.Y - vertices[i].Y) * (circle.Y - vertices[i].Y); } } temp = circle - temp; temp.Normalize(); } return temp; } Thanks in advance for any tips on the 4 issues. EDIT1: Something isn't working properly. The collision axis doesn't come out right and the interpolation also seems to have no effect. I've changed the code a bit: private bool ShapesIntersect(Paddle paddle, Ball ball) { overlap = 1000000f; //large value overlapAxis = Vector2.Zero; MTV = Vector2.Zero; foreach (Vector2 ax in Axes) { float[] pad = paddle.ProjectPaddle(ax); //pad0 = min, pad1 = max float[] circle = ball.ProjectBall(ax); //circle0 = min, circle1 = max if (pad[1] < circle[0] || circle[1] < pad[0]) { return false; } if (Math.Abs(pad[1] - circle[0]) < Math.Abs(circle[1] - pad[0])) { if (Math.Abs(overlap) > Math.Abs(-pad[1] + circle[0])) { overlap = -pad[1] + circle[0]; overlapAxis = ax * (-1); } //to get the proper axis } else { if (Math.Abs(overlap) > Math.Abs(circle[1] - pad[0])) { overlap = circle[1] - pad[0]; overlapAxis = ax; } } } if (overlapAxis != Vector2.Zero) { MTV = overlapAxis * Math.Abs(overlap); } return true; } And part of the Update method: if (ShapesIntersect(paddleRight, ball)) { isColliding = true; if (MTV != Vector2.Zero) { ball.X += MTV.X; ball.Y += MTV.Y; } //test if (overlapAxis.X == 0) //collision with horizontal edge { } else if (overlapAxis.Y == 0) //collision with vertical edge { float factor = Math.Abs(ball.ballCenter.Y - paddleRight.Y) / paddleRight.Height; if (factor > 1) factor = 1f; if (overlapAxis.X < 0) //left edge? ball.Speed = ball.DEFAULTSPEED * Vector2.Normalize(Vector2.Reflect(ball.Speed, (Vector2.Lerp(new Vector2(-1, -3), new Vector2(-1, 3), factor)))); else //right edge? ball.Speed = ball.DEFAULTSPEED * Vector2.Normalize(Vector2.Reflect(ball.Speed, (Vector2.Lerp(new Vector2(1, -3), new Vector2(1, 3), factor)))); } else //vertex collision??? { ball.Speed = -ball.Speed; } } What seems to happen is that "overlapAxis" doesn't always return the right one. So instead of (-1,0) i get the (1,0) (this happened even before i multiplied with -1 there). Sometimes there isn't even a collision registered even though the ball passes through the paddle... The interpolation also seems to have no effect as the angles barely change (or the overlapAxis is almost never (-1,0) or (1,0) but something like (0.9783473, 0.02743843)... ). What am i missing here? :(

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• How to create array with unique sprites? in cocos2d iphone

  - by prakash s

  I write the code like this. This displays only one sprite (red colour bubble) with number of times and moving down, but actually I want to display different sprites (different colour bubble) every time and moving down. I also add no of .png images in resource folder of my project. Here I used only 3.png, but I need to display all *.png images (different colour bubbles) in my project but I don't know how to get this. Please help me Thank you. Here is the code: -(void)addTarget { CCSprite *target = [CCSprite spriteWithFile:@"3.png" rect:CGRectMake(0, 0, 256, 256)]; CGSize winSize = [[CCDirector sharedDirector] winSize]; int minY = target.contentSize.height/2; int maxY = winSize.height - target.contentSize.height/2; int rangeY = maxY - minY; int actualY = (arc4random() % rangeY) + minY; // Create the target slightly off-screen along the right edge, // and along a random position along the Y axis as calculated above target.position = ccp(winSize.width + (target.contentSize.width/2), actualY); [self addChild:target]; // Determine speed of the target int minDuration = 4.0; int maxDuration = 12.0; int rangeDuration = maxDuration - minDuration; int actualDuration = (arc4random() % rangeDuration) + minDuration; // Create the actions id actionMove = [CCMoveTo actionWithDuration:actualDuration position:ccp(-target.contentSize.width/2,actualY)]; id actionMoveDone = [CCCallFuncN actionWithTarget:self selector:@selector(spriteMoveFinished:)]; [target runAction:[CCSequence actions:actionMove, actionMoveDone, nil]]; // Add to targets array target.tag = 2; [_targets addObject:target]; } -(void)gameLogic:(ccTime)dt { [self addTarget]; } -(id) init { if( (self=[super initWithColor:ccc4(255,255,255,255)] )) { // Enable touch events self.isTouchEnabled = YES; // Initialize arrays _targets = [[NSMutableArray alloc] init]; _projectiles = [[NSMutableArray alloc] init]; // Get the dimensions of the window for calculation purposes CGSize winSize = [[CCDirector sharedDirector] winSize]; [self schedule:@selector(gameLogic:) interval:1.0]; [self schedule:@selector(update:)]; } return self; } - (void)update:(ccTime)dt { NSMutableArray *projectilesToDelete = [[NSMutableArray alloc] init]; for (CCSprite *projectile in _projectiles) { CGRect projectileRect = CGRectMake(projectile.position.x - (projectile.contentSize.width/2), projectile.position.y - (projectile.contentSize.height/2), projectile.contentSize.width, projectile.contentSize.height); NSMutableArray *targetsToDelete = [[NSMutableArray alloc] init]; for (CCSprite *target in _targets) { CGRect targetRect = CGRectMake(target.position.x - (target.contentSize.width/2), target.position.y - (target.contentSize.height/2), target.contentSize.width, target.contentSize.height); if (CGRectIntersectsRect(projectileRect, targetRect)) { [targetsToDelete addObject:target]; } } for (CCSprite *target in targetsToDelete) { [_targets removeObject:target]; [self removeChild:target cleanup:YES]; _projectilesDestroyed++; if (_projectilesDestroyed > 30) { //GameOverScene *gameOverScene = [GameOverScene node]; // [gameOverScene.layer.label setString:@"You Win!"]; // [[CCDirector sharedDirector] replaceScene:gameOverScene]; } } if (targetsToDelete.count > 0) { [projectilesToDelete addObject:projectile]; } [targetsToDelete release]; } for (CCSprite *projectile in projectilesToDelete) { [_projectiles removeObject:projectile]; [self removeChild:projectile cleanup:YES]; } [projectilesToDelete release]; }

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• Transform 3D vectors between coordinate systems

  - by Nir Cig

  I've got 6 points in 3D space: A,B,C,D,E,F, that represent 4 vectors. AB is perpendicular to AC and DE is perpendicular to DF. I need to find a transformation matrix M, that transforms AB to DE and AC to DF. In other words: M·AB=DE, M·AC=DF If no scaling was involved, this could be solved with a simple rotation matrix. But since the ratios |AB|/|DE|, |AC|/|DF| might be different, I'm not sure how to proceed.

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• Any reliable polygon normal calculation code?

  - by Jenko

  Do you have any reliable face normal calculation code? I'm using this but it fails when faces are 90 degrees upright or similar. // the normal point var x:Number = 0; var y:Number = 0; var z:Number = 0; // if is a triangle with 3 points if (points.length == 3) { // read vertices of triangle var Ax:Number, Bx:Number, Cx:Number; var Ay:Number, By:Number, Cy:Number; var Az:Number, Bz:Number, Cz:Number; Ax = points[0].x; Bx = points[1].x; Cx = points[2].x; Ay = points[0].y; By = points[1].y; Cy = points[2].y; Az = points[0].z; Bz = points[1].z; Cz = points[2].z; // calculate normal of a triangle x = (By - Ay) * (Cz - Az) - (Bz - Az) * (Cy - Ay); y = (Bz - Az) * (Cx - Ax) - (Bx - Ax) * (Cz - Az); z = (Bx - Ax) * (Cy - Ay) - (By - Ay) * (Cx - Ax); // if is a polygon with 4+ points }else if (points.length > 3){ // calculate normal of a polygon using all points var n:int = points.length; x = 0; y = 0; z = 0 // ensure all points above 0 var minx:Number = 0, miny:Number = 0, minz:Number = 0; for (var p:int = 0, pl:int = points.length; p < pl; p++) { var po:_Point3D = points[p] = points[p].clone(); if (po.x < minx) { minx = po.x; } if (po.y < miny) { miny = po.y; } if (po.z < minz) { minz = po.z; } } if (minx > 0 || miny > 0 || minz > 0){ for (p = 0; p < pl; p++) { po = points[p]; po.x -= minx; po.y -= miny; po.z -= minz; } } var cur:int = 1, prev:int = 0, next:int = 2; for (var i:int = 1; i <= n; i++) { // using Newell method x += points[cur].y * (points[next].z - points[prev].z); y += points[cur].z * (points[next].x - points[prev].x); z += points[cur].x * (points[next].y - points[prev].y); cur = (cur+1) % n; next = (next+1) % n; prev = (prev+1) % n; } } // length of the normal var length:Number = Math.sqrt(x * x + y * y + z * z); // if area is 0 if (length == 0) { return null; }else{ // turn large values into a unit vector x = x / length; y = y / length; z = z / length; }

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• Scene Graph as Object Container?

  - by Bunkai.Satori

  Scene graph contains game nodes representing game objects. At a first glance, it might seem practical to use Scene Graph as physical container for in game objects, instead of std::vector< for example. My question is, is it practical to use Scene Graph to contain the game objects, or should it be used only to define scene objects/nodes linkages, while keepig the objects stored in separate container, such as std::vector<?

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• RTS game diplomacy heuristics

  - by kd304

  I'm reimplementing an old 4X space-rts game which has diplomacy options. The original was based on a relation scoring system (0..100) and a set of negotiation options (improve relations, alliance, declare war, etc.) The AI player usually had 3 options: yes, maybe and no; each adding or removing some amount to the relation score. How should the AI chose between the options? How does the diplomacy work in other games and how are they imlemented? Any good books/articles on the subject? (Googling the term diplomacy yields the game Diplomacy, which is unhelpful.)

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• Playing a Song causing WP7 to crash on phone, but not on emulator

  - by Michael Zehnich

  Hi there, I am trying to implement a song into a game that begins playing and continually loops on Windows Phone 7 via XNA 4.0. On the emulator, this works fine, however when deployed to a phone, it simply gives a black screen before going back to the home screen. Here is the rogue code in question, and commenting this code out makes the app run fine on the phone: // in the constructor fields private Song song; // in the LoadContent() method song = Content.Load<Song>("song"); // in the Update() method if (MediaPlayer.GameHasControl && MediaPlayer.State != MediaState.Playing) { MediaPlayer.Play(song); } The song file itself is a 2:53 long, 2.28mb .wma file at 106kbps bitrate. Again this works perfectly on emulator but does not run at all on phone. Thanks for any help you can provide!

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• Create dynamic buffer SharpDX

  - by fedab

  I want to set a buffer that is updated every frame but can't figure it out, what i have to do. The only working thing i have is this: mdexcription = new BufferDescription(Matrix.SizeInBytes * Matrices.Length, ResourceUsage.Dynamic, BindFlags.VertexBuffer, CpuAccessFlags.Write, ResourceOptionFlags.None, 0); instanceBuffer = SharpDX.Direct3D11.Buffer.Create(Device, Matrices, mdexcription); vBB = new VertexBufferBinding(instanceBuffer, Matrix.SizeInBytes, 0); DeviceContext.InputAssembler.SetVertexBuffers(1, vBB); Draw: //Change Matrices (Matrix[]) every frame... instanceBuffer.Dispose(); instanceBuffer = SharpDX.Direct3D11.Buffer.Create(Device, Matrices, mdexcription); vBB = new VertexBufferBinding(instanceBuffer, Matrix.SizeInBytes, 0); DeviceContext.InputAssembler.SetVertexBuffers(1, vBB); I guess Dispose() and creating a new buffer is slow and can be done much faster. I've read about DataStream but i do not know, how to set this up properly. What steps do i have to do to set up a DataStream to achieve fast every-frame update?

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• Combine Two Shader Program

  - by Siddharth

  For my android application, I want to apply brightness and contrast shader on same image. At present I am using gpuimage plugin. In that I found two separate program for brightness and contrast as per the following. Contrast shader: varying highp vec2 textureCoordinate; uniform sampler2D inputImageTexture; uniform lowp float contrast; void main() { lowp vec4 textureColor = texture2D(inputImageTexture, textureCoordinate); gl_FragColor = vec4(((textureColor.rgb - vec3(0.5)) * contrast + vec3(0.5)), textureColor.w); } Brightness shader: varying highp vec2 textureCoordinate; uniform sampler2D inputImageTexture; uniform lowp float brightness; void main() { lowp vec4 textureColor = texture2D(inputImageTexture, textureCoordinate); gl_FragColor = vec4((textureColor.rgb + vec3(brightness)), textureColor.w); } Now applying both of the effects I write following code varying highp vec2 textureCoordinate; uniform sampler2D inputImageTexture; varying highp vec2 textureCoordinate2; uniform sampler2D inputImageTexture2; uniform lowp float contrast; uniform lowp float brightness; void main() { lowp vec4 textureColorForContrast = texture2D(inputImageTexture, textureCoordinate); lowp vec4 contastVec4 = vec4(((textureColorForContrast.rgb - vec3(0.5)) * contrast + vec3(0.5)), textureColorForContrast.w); lowp vec4 textureColorForBrightness = texture2D(inputImageTexture2, textureCoordinate2); lowp vec4 brightnessVec4 = vec4((textureColorForBrightness.rgb + vec3(brightness)), textureColorForBrightness.w); gl_FragColor = contastVec4 + brightnessVec4; } Doesn't able to get desire result. I can't able to figure out what I have to do next? So please friends help me in this. What program I have to write?

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• How to implement a stack of game states in C++

  - by Lisandro Vaccaro

  I'm new to C++ and as a college proyect I'm building a 2D platformer with some classmates, I recently read that it's a good idea to have a stack of gamestates instead of a single global variable with the game state (which is what I have now) but I'm not sure how to do it. Currently this is my implementation: class GameState { public: virtual ~GameState(){}; virtual void handle_events() = 0; virtual void logic() = 0; virtual void render() = 0; }; class Menu : public GameState { public: Menu(); ~Menu(); void handle_events(); void logic(); void render(); }; Then I have a global variable of type GameState: GameState *currentState = NULL; And in my Main I define the currentState and call it's methods: int main(){ currentState = new Menu(); currentState.handle_events(); } How can I implement a stack or something similar to go from that to something like this: int main(){ statesStack.push(new Menu()); statesStack.getTop().handle_events(); }

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• Entity component system -> handling components that depend on one another

  - by jtedit

  I really like the idea of an entity component system and feel it has great flexibility, but have a question. How should dependent components be handled? I'm not talking about how components should communicate with other components they depend on, I have that sorted, but rather how to ensure components are present. For example, an entity cannot have a "velocity" component if it doesn't have a "position" component, in the same way it cant have an "acceleration" component if it doesn't have a "velocity" component. My first idea was every component class overrides an "onAddedToEntity(Entity ent)" function. Then in that function it checks that prerequisite components are also added to the entity, eg: struct EntCompVelocity() : public EntityComponent{ //member variables here void onAddedToEntity(Entity ent){ if(!ent.hasComponent(EntCompPosition::Id)){ ent.addComponent(new EntCompPosition()); } } } This has the nice property that if the acceleration component adds the velocity component, the velocity component will itself add the position component to the entity so dependency "trees" will sort themselves out. However my concern is if I do this components will silently be added with default values and, in the example of adding position, many entities will appear at the origin. Another idea was to simple have the "Entity.addComponent();" function return false if the component's prerequisite components aren't already on the entity, this would force you to manually add the position component and set its value before adding the velocity component. Finally I could simply not ensure a components prerequisite components are added, the "UpdatePosition" system only deals with entities with both a position and velocity component, so therefore adding a velocity component without having a position component wont be a problem (it wont cause crashes due to null pointer/etc), but it does mean entities will carry useless unused data if you add components but not their prerequisite components. Does anyone have experience with this problem and/or any of these methods to solve it? How did you solve the problem?

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• Gamemaker: Making a bullet Spawn at the enemy it was called from

  - by Strokes

  I'm making a gamemaker game with gml. In this game I have multiple enemies (same object) on screen at the same time. I want them to all spawn a bullet at their location. But instead each enemy spawns a bullet at one single enemy. They all shoot but the bullets appear in the wrong location. I want the bullet to spawn at the location of the instance is was called for. How do I do this? Thank you for reading my question. Code: obj_carrier is the enemy I want to spawn from. obj_carrier_bullet is the bullet I want to spawn at location of the carrier There are multiple carriers around the stage. In the step event of the carrier following an if statement: instance_create(obj_carrier.x, obj_carrier.y, obj_carrier_bullet)

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• Clojure agents consuming from a queue

  - by erikcw

  I'm trying to figure out the best way to use agents to consume items from a Message Queue (Amazon SQS). Right now I have a function (process-queue-item) that grabs an items from the queue, and processes it. I want to process these items concurrently, but I can't wrap my head around how to control the agents. Basically I want to keep all of the agents busy as much as possible without pulling to many items from the Queue and developing a backlog (I'll have this running on a couple of machines, so items need to be left in the queue until they are really needed). Can anyone give me some pointers on improving my implementation? (def active-agents (ref 0)) (defn process-queue-item [_] (dosync (alter active-agents inc)) ;retrieve item from Message Queue (Amazon SQS) and process (dosync (alter active-agents dec))) (defn -main [] (def agents (for [x (range 20)] (agent x))) (loop [loop-count 0] (if (< @active-agents 20) (doseq [agent agents] (if (agent-errors agent) (clear-agent-errors agent)) ;should skip this agent until later if it is still busy processing (not sure how) (send-off agent process-queue-item))) ;(apply await-for (* 10 1000) agents) (Thread/sleep 10000) (logging/info (str "ACTIVE AGENTS " @active-agents)) (if (> 10 loop-count) (do (logging/info (str "done, let's cleanup " count)) (doseq [agent agents] (if (agent-errors agent) (clear-agent-errors agent))) (apply await agents) (shutdown-agents)) (recur (inc count)))))

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• XNA - Error while rendering a texture to a 2D render target via SpriteBatch

  - by Jared B

  I've got this simple code that uses SpriteBatch to draw a texture onto a RenderTarget2D: private void drawScene(GameTime g) { GraphicsDevice.Clear(skyColor); GraphicsDevice.SetRenderTarget(targetScene); drawSunAndMoon(); effect.Fog = true; GraphicsDevice.SetVertexBuffer(line); effect.MainEffect.CurrentTechnique.Passes[0].Apply(); GraphicsDevice.DrawPrimitives(PrimitiveType.TriangleStrip, 0, 2); GraphicsDevice.SetRenderTarget(null); SceneTexture = targetScene; } private void drawPostProcessing(GameTime g) { effect.SceneTexture = SceneTexture; GraphicsDevice.SetRenderTarget(targetBloom); spriteBatch.Begin(SpriteSortMode.Immediate, BlendState.Opaque, null, null, null); { if (Bloom) effect.BlurEffect.CurrentTechnique.Passes[0].Apply(); spriteBatch.Draw( targetScene, new Rectangle(0, 0, Window.ClientBounds.Width, Window.ClientBounds.Height), Color.White); } spriteBatch.End(); BloomTexture = targetBloom; GraphicsDevice.SetRenderTarget(null); } Both methods are called from my Draw(GameTime gameTime) function. First drawScene is called, then drawPostProcessing is called. The thing is, when I run this code I get an error on the spriteBatch.Draw call: The render target must not be set on the device when it is used as a texture. I already found the solution, which is to draw the actual render target (targetScene) to the texture so it doesn't create a reference to the loaded render target. However, to my knowledge, the only way of doing this is to write: GraphicsDevice.SetRenderTarget(outputTarget) SpriteBatch.Draw(inputTarget, ...) GraphicsDevice.SetRenderTarget(null) Which encounters the same exact problem I'm having right now. So, the question I'm asking is: how would I render inputTarget to outputTarget without reference issues?

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• Small adventure game

  - by Nick Rosencrantz

  I'm making a small adventure game where the player can walk through Dungeons and meet scary characters: The whole thing is 20 java classes and I'm making this a standalone frame while it could very well be an applet I don't want to make another applet since I might want to recode this in C/C++ if the game or game engine turns out a success. The engine is the most interesting part of the game, it controls players and computer-controlled characters such as Zombies, Reptile Warriors, Trolls, Necromancers, and other Persons. These persons can sleep or walk around in the game and also pick up and move things. I didn't add many things so I suppose that is the next thing to do is to add things that can get used now that I already added many different types of walking persons. What do you think I should add and do with things in the game? The things I have so far is: package adventure; /** * The data type for things. Subclasses will be create that takes part of the story */ public class Thing { /** * The name of the Thing. */ public String name; /** * @param name The name of the Thing. */ Thing( String name ) { this.name = name; } } public class Scroll extends Thing { Scroll (String name) { super(name); } } class Key extends Thing { Key (String name) { super(name); } } The key is the way to win the game if you figure our that you should give it to a certain person and the scroll can protect you from necromancers and trolls. If I make this game more Dungeons and Dragons-inspired, do you think will be any good? Any other ideas that you think I could use here? The Threadwhich steps time forward and wakes up persons is called simulation. Do you think I could do something more advanced with this class? package adventure; class Simulation extends Thread { private PriorityQueue Eventqueue; Simulation() { Eventqueue = new PriorityQueue(); start(); } public void wakeMeAfter(Wakeable SleepingObject, double time) { Eventqueue.enqueue(SleepingObject, System.currentTimeMillis()+time); } public void run() { while(true) { try { sleep(5); //Sov i en halv sekund if (Eventqueue.getFirstTime() <= System.currentTimeMillis()) { ((Wakeable)Eventqueue.getFirst()).wakeup(); Eventqueue.dequeue(); } } catch (InterruptedException e ) { } } } } And here is the class that makes up the actual world: package adventure; import java.awt.*; import java.net.URL; /** * Subklass to World that builds up the Dungeon World. */ public class DungeonWorld extends World { /** * * @param a Reference to adventure game. * */ public DungeonWorld(Adventure a) { super ( a ); // Create all places createPlace( "Himlen" ); createPlace( "Stairs3" ); createPlace( "IPLab" ); createPlace( "Dungeon3" ); createPlace( "Stairs5" ); createPlace( "C2M2" ); createPlace( "SANS" ); createPlace( "Macsal" ); createPlace( "Stairs4" ); createPlace( "Dungeon2" ); createPlace( "Datorsalen" ); createPlace( "Dungeon");//, "Ljushallen.gif" ); createPlace( "Cola-automaten", "ColaAutomat.gif" ); createPlace( "Stairs2" ); createPlace( "Fable1" ); createPlace( "Dungeon1" ); createPlace( "Kulverten" ); // Create all connections between places connect( "Stairs3", "Stairs5", "Down", "Up" ); connect( "Dungeon3", "SANS", "Down", "Up" ); connect( "Dungeon3", "IPLab", "West", "East" ); connect( "IPLab", "Stairs3", "West", "East" ); connect( "Stairs5", "Stairs4", "Down", "Up" ); connect( "Macsal", "Stairs5", "South", "Norr" ); connect( "C2M2", "Stairs5", "West", "East" ); connect( "SANS", "C2M2", "West", "East" ); connect( "Stairs4", "Dungeon", "Down", "Up" ); connect( "Datorsalen", "Stairs4", "South", "Noth" ); connect( "Dungeon2", "Stairs4", "West", "East" ); connect( "Dungeon", "Stairs2", "Down", "Up" ); connect( "Dungeon", "Cola-automaten", "South", "North" ); connect( "Stairs2", "Kulverten", "Down", "Up" ); connect( "Stairs2", "Fable1", "East", "West" ); connect( "Fable1", "Dungeon1", "South", "North" ); // Add things // --- Add new things here --- getPlace("Cola-automaten").addThing(new CocaCola("Ljummen cola")); getPlace("Cola-automaten").addThing(new CocaCola("Avslagen Cola")); getPlace("Cola-automaten").addThing(new CocaCola("Iskall Cola")); getPlace("Cola-automaten").addThing(new CocaCola("Cola Light")); getPlace("Cola-automaten").addThing(new CocaCola("Cuba Cola")); getPlace("Stairs4").addThing(new Scroll("Scroll")); getPlace("Dungeon3").addThing(new Key("Key")); Simulation sim = new Simulation(); // Load images to be used as appearance-parameter for persons Image studAppearance = owner.loadPicture( "Person.gif" ); Image asseAppearance = owner.loadPicture( "Asse.gif" ); Image trollAppearance = owner.loadPicture( "Loke.gif" ); Image necromancerAppearance = owner.loadPicture( "Necromancer.gif" ); Image skeletonAppearance = owner.loadPicture( "Reptilewarrior.gif" ); Image reptileAppearance = owner.loadPicture( "Skeleton.gif" ); Image zombieAppearance = owner.loadPicture( "Zombie.gif" ); // --- Add new persons here --- new WalkingPerson(sim, this, "Peter", studAppearance); new WalkingPerson(sim, this, "Zombie", zombieAppearance ); new WalkingPerson(sim, this, "Zombie", zombieAppearance ); new WalkingPerson(sim, this, "Skeleton", skeletonAppearance ); new WalkingPerson(sim, this, "John", studAppearance ); new WalkingPerson(sim, this, "Skeleton", skeletonAppearance ); new WalkingPerson(sim, this, "Skeleton", skeletonAppearance ); new WalkingPerson(sim, this, "Skeleton", skeletonAppearance ); new WalkingPerson(sim, this, "Sean", studAppearance ); new WalkingPerson(sim, this, "Reptile", reptileAppearance ); new LabAssistant(sim, this, "Kate", asseAppearance); new LabAssistant(sim, this, "Jenna", asseAppearance); new Troll(sim, this, "Troll", trollAppearance); new Necromancer(sim, this, "Necromancer", necromancerAppearance); } /** * * The place where persons are placed by default * *@return The default place. * */ public Place defaultPlace() { return getPlace( "Datorsalen" ); } private void connect( String p1, String p2, String door1, String door2) { Place place1 = getPlace( p1 ); Place place2 = getPlace( p2 ); place1.addExit( door1, place2 ); place2.addExit( door2, place1 ); } } Thanks

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• Alternative to Game State System?

  - by Ricket

  As far as I can tell, most games have some sort of "game state system" which switches between the different game states; these might be things like "Intro", "MainMenu", "CharacterSelect", "Loading", and "Game". On the one hand, it totally makes sense to separate these into a state system. After all, they are disparate and would otherwise need to be in a large switch statement, which is obviously messy; and they certainly are well represented by a state system. But at the same time, I look at the "Game" state and wonder if there's something wrong about this state system approach. Because it's like the elephant in the room; it's HUGE and obvious but nobody questions the game state system approach. It seems silly to me that "Game" is put on the same level as "Main Menu". Yet there isn't a way to break up the "Game" state. Is a game state system the best way to go? Is there some different, better technique to managing, well, the "game state"? Is it okay to have an intro state which draws a movie and listens for enter, and then a loading state which loops on the resource manager, and then the game state which does practically everything? Doesn't this seem sort of unbalanced to you, too? Am I missing something?

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• Resolution independence - resize on the fly or ship all sizes?

  - by RecursiveCall

  My game relies heavily on textures of various sizes with some being full-screen. The game is targeted for multiple resolutions. I found that resizing textures (downsizing) works quite well for this game’s art type (it’s not Pixel Art or anything like that). I asked my artist to ensure that all textures at the edges of the screen to be created in such a way that they can safely “overflow” off screen; this means that aspect ratio is not an issue. So with no aspect ratio issues, I figured that I would simply ask my artist to create assets in very high resolution, and then resize them down to the appropriate screen resolution. The question is, when and how do I do that? Do I pre-resize everything to common resolutions in Photoshop and package all assets in the final product (increasing the size download that the user has to deal with) and then select the appropriate asset based on the detected resolution? Or do I ship with the largest set of Textures, detect the resolution on load, set a render target and draw all downsized assets to it and use that? Or for the latter, do I use some sort of a CPU-sided algorithm to resize on game load?

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• Slick2D + LWJGL collision system

  - by Connor W

  So I've been learning java for a while and have explored slick and lwjgl before but went away from using Slick for a while. But I've recently gone back to using it (as I'm making a platformer and Tiled will be really helpful). But here's where my problems begin: collision. I have a player polygon and I check to see if it's colliding with my tiled map with this method: public static boolean playerCollisionWith() { for(int i = 0; i < Blockmap.entities.size(); i++) { Block entity1 = (Block) Blockmap.entities.get(i); if(playerPoly.intersects(entity1.poly)) { return true; } } return false; } This would work normally but I'm using a different method for movement. Instead of just adding a speed variable to the player's x axis. I move like this: if(Keyboard.isKeyDown(Keyboard.KEY_RIGHT)) { speedX = Math.min(5, speedX + 1); moving = true; playerPoly.setX(x); if(playerCollisionWith()) { speedX = -5; playerPoly.setX(x); } } That Math.min call is what is messing me up =. I can't just call speedX = -5, because when I do the player "bounces" when the right mouse button is down and it's colliding. Bounces as in flashes back and forth REALLY quickly. But I don't really know how I would make it so that collisions on the y axis would work either, whether the player is jumping or not. So if I could get some help with how to fix this problem that would be great. Thank you for the help!

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• With 2 superposed cameras at different depths and switching their culling masks between layers to implement object-selective antialising:

  - by user36845

  We superposed two cameras, one of which uses AA as post-processing effect (AA filtering is cancelled). The camera with the AA effect has depth 0 and the camera with no effect has depth 1 as can be seen in the 5th and 6th Picture. The objects seen on the left are in layer 1 and the ones on the right are in layer 2. We then wrote a script that switches the culling masks of the cameras between the two layers at the push of buttons 1 and 2 respectively, and accomplishes object-selective antialiasing as seen in the first the three pictures. (The way two cameras separately switch culling masks between layers is illustrated in pictures 7,8 & 9.) HOWEVER, after making the environment 3D (see pictures 1-4), by parenting the 2 cameras under First-Person Controller, we started moving around in the environment and stumbled upon a big issue: When we look at the objects from such an angle as in the 4th Picture and we want to apply antialiasing to the first object (object on the left) which stands closer to our cameras now, the culling mask of 1st camera which is at depth 0, has to be switched to that object’s layer while the second object has to be in the culling mask of the 2nd camera at depth 1. And since the two image outputs of two superposed cameras are laid on top of one another; we obtain the erroneous/unrealistic result of the object farther in the back appearing closer to the camera than the front object (see 4th Picture). We already tried switching depths of cameras so that the 1st camera –with AA- now has depth 1 and the second has depth 0; BUT the camera with the AA effect Works in such a way that it applies the AA effect to its full view. So; the camera with the AA effect always has to remain at the lowest depth and the layer of the object to be antialiased has to be then assigned to the culling mask of the AA camera; otherwise all objects in the AA camera’s view (the two cubes in our case) become antialised, which we don’t want. So; how can we resolve this? The pictures are below and in the comments since each post can have 2 pics: Pic 1. No button is pushed: Both objects seem aliased. Pic 2. Button 1 is pushed: Left (1st) object is antialiased. 2nd object remains aliased. Pic 3. Button 2 is pushed: Right (2nd) object is antialiased. 1st object remains aliased. Pic 4. The problematic result in 3D, when using two superposed cameras with different depths Pic 5. Camera 1’s properties can be seen: using AA post-processing and its depth is 0 Pic 6. Camera 2’s properties can be seen: NOT using AA post-processing and its depth is 1 Pic 7. When no button is pushed, both objects are in the culling mask of Camera 2 and are aliased Pic 8. When pushed 1, camera 1 (bottom) shows the 1st object and camera 2 (top) shows the 2nd Pic 9. When pushed 2, camera 1 (bottom) shows the 2nd object and camera 2 (top) shows the 1st

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• Parabolic throw with set Height and range (libgdx)

  - by Tauboga

  Currently i'm working on a minigame for android where you have a rotating ball in the center of the display which jumps when touched in the direction of his current angle. I'm simply using a gravity vector and a velocity vector in this way: positionBall = positionBall.add(velocity); velocity = velocity.add(gravity); and velocity.x = (float) Math.cos(angle) * 12; /* 12 to amplify the velocity */ velocity.y = (float) Math.sin(angle) * 15; /* 15 to amplify the velocity */ That works fine. Here comes the problem: I want to make the jump look the same on all possible resolutions. The velocity needs to be scaled in a way that when the ball is thrown straight upwards it will touch the upper display border. When thrown directly left or right the range shall be exactly long enough to touch the left/right display border. Which formula(s) do I need to use and how to implement them correctly? Thanks in advance!

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• How to prevent 2D camera rotation if it would violate the bounds of the camera?

  - by Andrew Price

  I'm working on a Camera class and I have a rectangle field named Bounds that determines the bounds of the camera. I have it working for zooming and moving the camera so that the camera cannot exit its bounds. However, I'm a bit confused on how to do the same for rotation. Currently I allow rotating of the camera's Z-axis. However, if sufficiently zoomed out, upon rotating the camera, areas of the screen outside the camera's bounds can be shown. I'd like to deny the rotation assuming it meant that the newly rotated camera would expose areas outside the camera's bounds, but I'm not quite sure how. I'm still new to Matrix and Vector math and I'm not quite sure how to model if the newly rotated camera sees outside of its bounds, undo the rotation. Here's an image showing the problem: http://i.stack.imgur.com/NqprC.png The red is out of bounds and as a result, the camera should never be allowed to rotate itself like this. This seems like it would be a problem with all rotated values, but this is not the case when the camera is zoomed in enough. Here are the current member variables for the Camera class: private Vector2 _position = Vector2.Zero; private Vector2 _origin = Vector2.Zero; private Rectangle? _bounds = Rectangle.Empty; private float _rotation = 0.0f; private float _zoom = 1.0f; Is this possible to do? If so, could someone give me some guidance on how to accomplish this? Thanks. EDIT: I forgot to mention I am using a transformation matrix style camera that I input in to SpriteBatch.Begin. I am using the same transformation matrix from this tutorial.

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• Android device - C++ OpenGL 2: eglCreateWindowSurface invalid

  - by ThreaderSlash

  I am trying to debug and run OGLES on Native C++ in my Android device in order to implement a native 3D game for mobile smart phones. The point is that I got an error and see no reason for that. Here is the line from the code that the debugger complains: mSurface = eglCreateWindowSurface(mDisplay, lConfig, mApplication->window, NULL); And this is the error message: Invalid arguments ' Candidates are: void * eglCreateWindowSurface(void *, void *, unsigned long int, const int *) ' --x-- Here is the declaration: android_app* mApplication; EGLDisplay mDisplay; EGLint lFormat, lNumConfigs, lErrorResult; EGLConfig lConfig; // Defines display requirements. 16bits mode here. const EGLint lAttributes[] = { EGL_RENDERABLE_TYPE, EGL_OPENGL_ES2_BIT, EGL_BLUE_SIZE, 5, EGL_GREEN_SIZE, 6, EGL_RED_SIZE, 5, EGL_SURFACE_TYPE, EGL_WINDOW_BIT, EGL_RENDER_BUFFER, EGL_BACK_BUFFER, EGL_NONE }; // Retrieves a display connection and initializes it. packt_Log_debug("Connecting to the display."); mDisplay = eglGetDisplay(EGL_DEFAULT_DISPLAY); if (mDisplay == EGL_NO_DISPLAY) goto ERROR; if (!eglInitialize(mDisplay, NULL, NULL)) goto ERROR; // Selects the first OpenGL configuration found. packt_Log_debug("Selecting a display config."); if(!eglChooseConfig(mDisplay, lAttributes, &lConfig, 1, &lNumConfigs) || (lNumConfigs <= 0)) goto ERROR; // Reconfigures the Android window with the EGL format. packt_Log_debug("Configuring window format."); if (!eglGetConfigAttrib(mDisplay, lConfig, EGL_NATIVE_VISUAL_ID, &lFormat)) goto ERROR; ANativeWindow_setBuffersGeometry(mApplication->window, 0, 0, lFormat); // Creates the display surface. packt_Log_debug("Initializing the display."); mSurface = eglCreateWindowSurface(mDisplay, lConfig, mApplication->window, NULL); --x-- Hope someone here can shed some light on it.

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• How to make game sessions like "with friends" games?

  - by Miguel lugo

  I want to make a game like "words with friends" or "chess with friends" or "Draw Something" or any of the other online multiplayer type games that are based around friends having game sessions with each other. I have made one app before that had no online features so I know the basics of objective-C and xCode. I looked up facebook connect so I know how to make friends find other friends to play with through Facebook. Just not how to make the gaming session. I only need my game to send a small array (or XML if it's better) of strings and integers from one iPhone to the other as each iPhone takes a turn. I'm NOT sending some complex video or anything like in "Draw Something." I was hoping someone could point me in the right direction (whether link to website or book or just a general idea) for how to do gaming sessions between two iPhones. I read this tutorial http://www.raywenderlich.com/3932/how-to-create-a-socket-based-iphone-app-and-server but it seems to be more about having two iPhones communicate over a server on a laptop or through the same wifi, not how to have iPhones game together over any Internet connection like in "with friends" games. I've tried to research this in other places but I'm never quite sure if what the articles I find are talking about is related to what I want or not. Someone please just point me in the right direction or give me a general outline of what to do. I will look up the specifics on my own once I know what to look for. Thank you.

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