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• Bukkit inventory saving: crashing somewhere

  - by HcgRandon

  I'm working on a command for a bukkit plugin that lets you transfer worlds. In the section about saving the player's inventory, I'm getting a runtime error. My question is: Why is the error happening, and how can I prevent it? The plugin code public void savePlayerInv(Player p, World w){ File playerInvConfigFile = new File(plugin.getDataFolder() + File.separator + "players" + File.separator + p.getName(), "inventory.yml"); FileConfiguration pInv = YamlConfiguration.loadConfiguration(playerInvConfigFile); PlayerInventory inv = p.getInventory(); int i = 0; for (ItemStack stack : inv.getContents()) { //increment integer i++; String startInventory = w.getName() + ".inv." + Integer.toString(i); //save inv pInv.set(startInventory + ".amount", stack.getAmount()); pInv.set(startInventory + ".durability", Short.toString(stack.getDurability())); pInv.set(startInventory + ".type", stack.getTypeId()); //pInv.set(startInventory + ".enchantment", stack.getEnchantments()); //TODO add enchant saveing } i = 0; for (ItemStack armor : inv.getArmorContents()){ i++; String startArmor = w.getName() + ".armor." + Integer.toString(i); //save armor pInv.set(startArmor + ".amount", armor.getAmount()); pInv.set(startArmor + ".durability", armor.getDurability()); pInv.set(startArmor + ".type", armor.getTypeId()); //pInv.set(startArmor + ".enchantment", armor.getEnchantments()); } //save exp if (p.getExp() != 0) { pInv.set(w.getName() + ".exp", p.getExp()); } } The offending line The stack trace complains about line 130, which is this line. pInv.set(startInventory + ".amount", stack.getAmount()); The stack trace 2012-03-21 13:23:25 [SEVERE] null org.bukkit.command.CommandException: Unhandled exception executing command 'wtp' in plugin Needs v1.0 at org.bukkit.command.PluginCommand.execute(PluginCommand.java:42) at org.bukkit.command.SimpleCommandMap.dispatch(SimpleCommandMap.java:166) at org.bukkit.craftbukkit.CraftServer.dispatchCommand(CraftServer.java:461) at net.minecraft.server.NetServerHandler.handleCommand(NetServerHandler.java:818) at net.minecraft.server.NetServerHandler.chat(NetServerHandler.java:778) at net.minecraft.server.NetServerHandler.a(NetServerHandler.java:761) at net.minecraft.server.Packet3Chat.handle(Packet3Chat.java:33) at net.minecraft.server.NetworkManager.b(NetworkManager.java:229) at net.minecraft.server.NetServerHandler.a(NetServerHandler.java:112) at net.minecraft.server.NetworkListenThread.a(NetworkListenThread.java:78) at net.minecraft.server.MinecraftServer.w(MinecraftServer.java:554) at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:452) at net.minecraft.server.ThreadServerApplication.run(SourceFile:490) Caused by: java.lang.NullPointerException at com.devoverflow.improved.needs.commands.CommandWorldtp.savePlayerInv(CommandWorldtp.java:130) at com.devoverflow.improved.needs.commands.CommandWorldtp.onCommand(CommandWorldtp.java:60) at org.bukkit.command.PluginCommand.execute(PluginCommand.java:40) ... 12 more

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• Setting density for Android game

  - by Asghar

  I am developing an Android game, in which a ball (bitmap) translates( is in motion). So I have provided motion equations for the ball. I have checked my app on Samsung galaxy S2 whose actual density is roundly 252 dpi, and It works fine on that. So my question is that Does these motions of bitmaps in surfaceView, depends on actual density of phone( i.e 252 dpi for S2) or generalized density(i.e 240 dpi). I am confused whether if I run this app on 235 dpi smartphone, So will it have the same performance of motion as it is on Galaxy S2( with 252 dpi) or it would be little slow ? Any help will be appreciated.

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• jBullet Collision/Physics not working as expected

  - by Kenneth Bray

  Below is the code for one of my objects in the game I am creating (yes although this is a cube, I am not making anything remotely like MineCraft), and my issue is I while the cube will display and is does follow the physics if the cube falls, it does not interact with any other objects in the game. If I was to have multiple cubes in screen at once they all just sit there, or shoot off in all directions never stopping. Anyway, I am new to jBullet, and any help would be appreciated. // Constructor public Cube(float pX, float pY, float pZ, float pSize) { posX = pX; posY = pY; posZ = pZ; size = pSize; rotX = 0; rotY = 0; rotZ = 0; // physics stuff fallMotionState = new DefaultMotionState(new Transform(new Matrix4f(new Quat4f(0, 0, 0, 1), new Vector3f(posX, posY, posZ), 1))); fallRigidBodyCI = new RigidBodyConstructionInfo(mass, fallMotionState, fallShape, fallInertia); fallRigidBody = new RigidBody(fallRigidBodyCI); }

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• Lerping to a center point while in motion

  - by Fibericon

  I have an enemy that initially flies in a circular motion, while facing away from the center point. This is how I achieve that: position.Y = (float)(Math.Cos(timeAlive * MathHelper.PiOver4) * radius + origin.Y); position.X = (float)(Math.Sin(timeAlive * MathHelper.PiOver4) * radius + origin.X); if (timeAlive < 5) { angle = (float)Math.Atan((0 - position.X) / (0 - position.Y)); if (0 < position.Y) RotationMatrix = Matrix.CreateRotationX(MathHelper.PiOver2) * Matrix.CreateRotationZ(-1 * angle); else RotationMatrix = Matrix.CreateRotationX(MathHelper.PiOver2) * Matrix.CreateRotationZ(MathHelper.Pi - angle); } That part works just fine. After five seconds of this, I want the enemy to turn inward, facing the center point. However, I've been trying to lerp to that point, since I don't want it to simply jump to the new rotation. Here's my code for trying to do that: else { float newAngle = -1 * (float)Math.Atan((0 - position.X) / (0 - position.Y)); angle = MathHelper.Lerp(angle, newAngle, (float)gameTime.ElapsedGameTime.Milliseconds / 1000); if (0 < position.Y) RotationMatrix = Matrix.CreateRotationX(MathHelper.PiOver2) * Matrix.CreateRotationZ(MathHelper.Pi - angle); else RotationMatrix = Matrix.CreateRotationX(MathHelper.PiOver2) * Matrix.CreateRotationZ(-1 * angle); } That doesn't work so fine. It seems like it's going to at first, but then it just sort of skips around. How can I achieve what I want here?

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• Camera Shake in Unreal Engine 4?

  - by The415

  Just to be straightforward, I am completely new to many aspects of coding and am searching for different specs and guidelines to aid me on my journey to crafting a wonderful game in Epic Games' Unreal Engine 4. I was wanting to know how to implement a third-person camera shake into my game, for use of the player sprinting, or crouching, etc. All I need is some tips on setting it up. I can figure the rest out.

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• Using components in the XNA Game State Management example?

  - by Zolomon

  In the game state management example at the App Hub, they say that if you want to use components in the example you can extend the GameScreen to host other components inside itself. I'm having a very hard time trying to tie this up. I tried extending the GameScreen class by adding a public property of public List<DrawableGameCompnent> components { get; set; } and then add my components to that list when I initialize the current screen as well as looping over the components in the LoadContent, Update and Draw methods. However, this doesn't feel like the correct way to go - mainly because it doesn't work when I get to the implementation of my GameplayScreen. Any thoughts?

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• want to build a replica of chartgame.com

  - by raj

  I want to develop a trading simulator based on technical analysis. my ideal application would exactly be chartgame.com currently chartgame.com doesnt have historical data for stocks beyond the year 2008 and I would like to have data until 2012 and have the capability to extend beyond if needed. what are the fundamentals to build an application like chartgame.com. If anyone here is willing to help I can arrange for the finances.let me know.

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• Dynamic Jump spot

  - by Pasquale Sada

  I have an initial velocity V(Vx,Vy,VZ) and a spot where he stands still at S(Sx,Sy,Sz). What I'm trying to achieve is a jump on a spot E(Ex,Ey,Ez) where you have clicked on(only lower or higher spot, because I've in place a simple steering behavior for even terrains). There are no obstacle around. I've implemented a formula that can make him jump in a precise way on a spot but you need to declare an angle: the problem arise when the selected spot is straight above your head. It' pretty lame that the char hang there and can reach a thing that is 1cm above is head. I'll share the code I'm using: Vector3 dir = target - transform.position; // get target direction float h = dir.y; // get height difference dir.y = 0; // retain only the horizontal direction float dist = dir.magnitude ; // get horizontal distance float a = angle * Mathf.Deg2Rad; // convert angle to radians dir.y = dist * Mathf.Tan(a); // set dir to the elevation angle dist += h / Mathf.Tan(a); // correct for small height differences // calculate the velocity magnitude float vel = Mathf.Sqrt(dist * Physics.gravity.magnitude / Mathf.Sin(2 *a)); return vel * dir.normalized;

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• Using normals in DirectX 10

  - by Dave

  I've got a working OBJ loader that loads vertices, indices, texture coordinates, and normals. As of right now it doesn't process texture coordinates or normals but it stores them in arrays and creates a valid mesh with the vertices and indices. Now I am trying to figure out how can I make the shader use the correct normal in the array for the current vertex if I can't setnormals() to my mesh. If I were to just use an index in my array of normals corresponding to the index in the vertices, how would I retrieve the current index the shader is processing? BTW: I am trying to write a blinn-phong shader technique. Also when I create the input layout and I've added the semantic NORMAL to it, how would I list the multiple semantics in that single parameter? Would I just separate it with a space? PS: If you need to see any code, just let me know.

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• Setting a leader from a sprite array

  - by Craig

  I'm looking to set a leader from an array of sprites, I keep on getting a NullReferenceException was unhandled error from within my main game class when calling the UpdateMouse Method. What have I dont wrong here? class MouseSprite { Random random = new Random(); private MouseSprite leader; public void UpdateBoundaryBox() { mouseBounds.X = (int)mousePosition.X - mouseTexture.Width / 2; mouseBounds.Y = (int)mousePosition.Y - mouseTexture.Height / 2; } public void UpdateMouse(Vector2 position, MouseSprite [] mice, int numberMice, int index) { Vector2 catPosition = position; int enemies = numberMice; this.alive = true; mice[random.Next(0, mice.Length)] = leader;

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• Bounding Box Collision Glitching Problem (Pygame)

  - by Ericson Willians

  So far the "Bounding Box" method is the only one that I know. It's efficient enough to deal with simple games. Nevertheless, the game I'm developing is not that simple anymore and for that reason, I've made a simplified example of the problem. (It's worth noticing that I don't have rotating sprites on my game or anything like that. After showing the code, I'll explain better). Here's the whole code: from pygame import * DONE = False screen = display.set_mode((1024,768)) class Thing(): def __init__(self,x,y,w,h,s,c): self.x = x self.y = y self.w = w self.h = h self.s = s self.sur = Surface((64,48)) draw.rect(self.sur,c,(self.x,self.y,w,h),1) self.sur.fill(c) def draw(self): screen.blit(self.sur,(self.x,self.y)) def move(self,x): if key.get_pressed()[K_w] or key.get_pressed()[K_UP]: if x == 1: self.y -= self.s else: self.y += self.s if key.get_pressed()[K_s] or key.get_pressed()[K_DOWN]: if x == 1: self.y += self.s else: self.y -= self.s if key.get_pressed()[K_a] or key.get_pressed()[K_LEFT]: if x == 1: self.x -= self.s else: self.x += self.s if key.get_pressed()[K_d] or key.get_pressed()[K_RIGHT]: if x == 1: self.x += self.s else: self.x -= self.s def warp(self): if self.y < -48: self.y = 768 if self.y > 768 + 48: self.y = 0 if self.x < -64: self.x = 1024 + 64 if self.x > 1024 + 64: self.x = -64 r1 = Thing(0,0,64,48,1,(0,255,0)) r2 = Thing(6*64,6*48,64,48,1,(255,0,0)) while not DONE: screen.fill((0,0,0)) r2.draw() r1.draw() # If not intersecting, then moves, else, it moves in the opposite direction. if not ((((r1.x + r1.w) > (r2.x - r1.s)) and (r1.x < ((r2.x + r2.w) + r1.s))) and (((r1.y + r1.h) > (r2.y - r1.s)) and (r1.y < ((r2.y + r2.h) + r1.s)))): r1.move(1) else: r1.move(0) r1.warp() if key.get_pressed()[K_ESCAPE]: DONE = True for ev in event.get(): if ev.type == QUIT: DONE = True display.update() quit() The problem: In my actual game, the grid is fixed and each tile has 64 by 48 pixels. I know how to deal with collision perfectly if I moved by that size. Nevertheless, obviously, the player moves really fast. In the example, the collision is detected pretty well (Just as I see in many examples throughout the internet). The problem is that if I put the player to move WHEN IS NOT intersecting, then, when it touches the obstacle, it does not move anymore. Giving that problem, I began switching the directions, but then, when it touches and I press the opposite key, it "glitches through". My actual game has many walls, and the player will touch them many times, and I can't afford letting the player go through them. The code-problem illustrated: When the player goes towards the wall (Fine). When the player goes towards the wall and press the opposite direction. (It glitches through). Here is the logic I've designed before implementing it: I don't know any other method, and I really just want to have walls fixed in a grid, but move by 1 or 2 or 3 pixels (Slowly) and have perfect collision without glitching-possibilities. What do you suggest?

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• Changes to myApp.js files are reverted back to normal when the project is build - Cocos2dx

  - by Mansoor

  I am trying to do some changes to my myApp.js file of coco2dx project for android in eclipse but I am not able to do it. I am actually trying to change the default background image of my app. But when I run my project all the changes goes back to before values For Eg: This is the default line wer we are setting our background image this.sprite = cc.Sprite.create("res/HelloWorld.png"); I am changing it to the following line: this.sprite = cc.Sprite.create("res/CloseNormal.png"); But when I run my project CloseNormal.png goes back to HelloWorld.png I am using: OS: Win7 Cocos2d Ver: cocos2dx 2.2.2 Why is this happening. Can anybody help me?

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• Equation / formula to determine an objects position on an ellipitcal path

  - by David Murphy

  I'm making a space game, as such I need objects to follow an elliptical path (orbit). I've worked out how to calculate all the important aspects of my orbits, the only remaining thing is how to have an object follow it. My Orbit class contains the major, minor (and by extension semi-major,semi-minor) lengths. The focii radius, area and circumference even. What is the equation to determine an objects x/y position (only need 2D) on an ellipse with a certain speed after a period of time. Basically, every frame I want to update the position based on the amount of elapsed time. I would like to have the speed along the path speed up and slow down according to the distance from the object it's orbiting, but not sure how to factor this in to the above given that at any point in time the speed has changed from it's previous speed. EDIT I can't answer my own question. But I found the question and answer is already on stackexchange: Kepler orbit : get position on the orbit over time

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• 2D Polygon Triangulation

  - by BleedObsidian

  I am creating a game engine using the JBox2D physics engine. It only allows you to create polygon fixtures up to 8 vertices, To create a body with more than 8 vertices, you need to create multiple fixtures for the body. My question is, How can I split the polygons a user creates into smaller polygons for JBox2D? Also, what topology should I use when splitting the polygons and why? (If JBox2D can have up to 8 vertices, why not split polygons into 8 per polygon)

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• Cutting out smaller rectangles from a larger rectangle

  - by Mauro Destro

  The world is initially a rectangle. The player can move on the world border and then "cut" the world via orthogonal paths (not oblique). When the player reaches the border again I have a list of path segments they just made. I'm trying to calculate and compare the two areas created by the path cut and select the smaller one to remove it from world. After the first iteration, the world is no longer a rectangle and player must move on border of this new shape. How can I do this? Is it possible to have a non rectangular path? How can I move the player character only on path? EDIT Here you see an example of what I'm trying to achieve: Initial screen layout. Character moves inside the world and than reaches the border again. Segment of the border present in the smaller area is deleted and last path becomes part of the world border. Character moves again inside the world. Segments of border present in the smaller area are deleted etc.

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• Save Zone Implementation in Asteroids

  - by Moaz

  I would like to implement a safe zone for asteroids so that when the ship gets destroyed, it shouldn't be there unless it is safe from other asteroids. I tried to check the distance between each asteroid and the ship, and if it is above threshold, it sets a flag to the ship that's a safe zone, but sometimes it work and sometimes it doesn't for (list<Asteroid>::iterator itr_astroid = asteroids.begin(); itr_astroid!=asteroids.end(); ) { if(currentShip.m_state == Ship::Ship_Dead) { float distance = itr_astroid->getCenter().distance(Vec2f(getWindowWidth()/2,getWindowHeight()/2)); if( distance>200) { currentShip.m_saveField = true; break; } else { currentShip.m_saveField = false; itr_astroid++; } } else { itr_astroid++; } }

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• (CanvsEngine) Collission problem ( TypeError: this._polygon[this._frame] is undefined) [on hold]

  - by user2127102

  How can i fix this error TypeError: this._polygon[this._frame] is undefined Heres my code: html: <!DOCTYPE Html> <head> <meta charset="utf-8"> <title>Project</title> <link href="css/style.css" rel="stylesheet"> <script src="http://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js" type="text/javascript"></script> <script src="js/canvasengine-1.3.0.all.min.js"></script> <script src="js/extends/Input.js"></script> <script src="main.js"></script> </head> <body> <canvas id="window"></canvas> </body> main.js: var canvas = CE.defines("window"). extend(Input). ready(function() { canvas.Scene.call("Game"); }); canvas.Scene.new({ name: "Game", materials: { images: { player: "img/character.png", Wall: "img/TestWall.png" } }, ready: function(stage) { var _canvas = this.getCanvas(); _canvas.setSize("browser", "strech"); this.Player = Class.new("Entity", [stage]); this.Player.el.drawImage("player"); stage.append(this.Player.el); this.Wall = Class.new("Entity", [stage]); this.Wall.el.drawImage("Wall"); this.Wall.position(300, 0); stage.append(this.Wall.el); }, render: function(stage) { //Controls ====== //Control calculations var self = this; this.Mover_A; this.Mover_D; this.Mover_W; this.Mover_S; canvas.Input.keyDown(Input.A, function(e) { self.Mover_A = true; }); canvas.Input.keyDown(Input.D, function(e) { self.Mover_D = true; }); canvas.Input.keyDown(Input.W, function(e) { self.Mover_W = true; }); canvas.Input.keyDown(Input.S, function(e) { self.Mover_S = true; console.log(self.Mover_S); }); canvas.Input.keyUp(Input.A, function(e) { self.Mover_A = false; }); canvas.Input.keyUp(Input.D, function(e) { self.Mover_D = false; }); canvas.Input.keyUp(Input.W, function(e) { self.Mover_W = false; }); canvas.Input.keyUp(Input.S, function(e) { self.Mover_S = false; }); x = 0; y = 0; if(this.Mover_A)x -= 1.5; //A if(this.Mover_D)x += 1.5;//D if(this.Mover_W)y -= 1.5;//W if(this.Mover_S)y += 1.5; //S this.Player.move(x, y); this.Player.hit("over", [this.Wall], function(state, el) { this.Player.move(x * -1, y * -1); }); //End Controls ===== stage.refresh(); } });

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• What are my tool options to prototype a 2D multiplayer game?

  - by Asher Einhorn

  I'm looking for the best tool to allow me to quickly put together a 2D game that relies largely on networking. It's extremely likely that this game will require a server side program to constantly run. I have little experience with these things and since it's a prototype i'd like the easiest options for achieving this. I am looking to make this game for the web and mobile devices, although at present I only have access to ios hardware, (no android etc). I just want to get the bare bones of this set up so I can test it from the earliest opportunity to see if it's fun.

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• how to get started with a game engine [closed]

  - by user19343

  I'm a 3rd year Computer Science student and I would like to get started with building a game engine or at least tinkering with making one. I am curious if there are any good resources to use to get started. I get the idea behind different pieces in the engine, but I'm not really sure about how they fit together. Is there anything out there to help teach me the skeleton of a game engine? So far I've been playing with the idea of a game engine that uses modules built in a circular linked list so that each can do it's computing and then pass move to the next piece of the engine to work.

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• How can I change this isometric engine to make it so that you could distinguish between blocks that are on different planes?

  - by l5p4ngl312

  I have been working on an isometric minecraft-esque game engine for a strategy game I plan on making. As you can see, it really needs some sort of shading. It is difficult to distinguish between separate elevations when the camera is facing away from the slope because everything is the same shade. So my question is: can I shade just a specific section of a sprite? All of those blocks are just sprites, so if I shaded the entire image, it would shade the whole block. I am using LWJGL. Are there any other approaches to take? Heres a link to a screenshot from the engine: http://i44.tinypic.com/qxqlix.jpg

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• Weird appearance for a 3D XNA ground

  - by Belos

  I wanted to add a ground so I can know the position of a helicopter in the world. But the ground appeared in a weird way: http://i.stack.imgur.com/yTSuW.jpg The ground had the following texture: http://i.stack.imgur.com/pdpxB.png EDIT: Sorry, I forgot to post the code: public class ImportModel { public Vector3 Position { get; set; } public Vector3 Rotation { get; set; } public Vector3 Scale { get; set; } Model Model; Matrix[] modeltransforms; GraphicsDevice GraphicDevice; ContentManager Content; BoundingSphere sphere; bool boundingimplemented = false; public ImportModel(string model, GraphicsDevice gd, ContentManager cm, Vector3 position, Vector3 rot, Vector3 sca) { GraphicDevice = gd; Content = cm; Position = position; Rotation = rot; Scale = sca; Model = Content.Load<Model>(model); modeltransforms = new Matrix[Model.Bones.Count]; Model.CopyAbsoluteBoneTransformsTo(modeltransforms); } public void Draw(Camera camera) { Matrix baseworld = Matrix.CreateScale(Scale) * Matrix.CreateFromYawPitchRoll(Rotation.Y, Rotation.X, Rotation.Z) * Matrix.CreateTranslation(Position); foreach (ModelMesh mesh in Model.Meshes) { Matrix localworld = modeltransforms[mesh.ParentBone.Index] * baseworld; foreach (ModelMeshPart meshpart in mesh.MeshParts) { BasicEffect effect = (BasicEffect)meshpart.Effect; effect.World = localworld; effect.View = camera.View; effect.Projection = camera.Projection; effect.EnableDefaultLighting(); } mesh.Draw(); } } public BoundingSphere BoundingSphere { get { if (!boundingimplemented) { foreach (ModelMesh mesh in Model.Meshes) { BoundingSphere transformed = mesh.BoundingSphere.Transform( modeltransforms[mesh.ParentBone.Index]); sphere = BoundingSphere.CreateMerged(sphere, transformed); } Matrix worldTransform = Matrix.CreateScale(Scale) * Matrix.CreateTranslation(Position); BoundingSphere transforme = sphere; transforme = transforme.Transform(worldTransform); return transforme; } else { Matrix worldTransform = Matrix.CreateScale(Scale) * Matrix.CreateTranslation(Position); BoundingSphere transformed = sphere; transformed = transformed.Transform(worldTransform); return transformed; } } } } Then I call the class from the Game1 class: ImportModel ground = new ImportModel("ground", GraphicsDevice, Content, Vector3.Zero, Vector3.Zero, new Vector3(20f)); EDIT2:This is how the scene looks from top: i.stack.imgur.com/Hs983.jpg

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• Bouncing ball isssue

  - by user

  I am currently working on the 2D Bouncing ball physics that bounces the ball up and down. The physics behaviour works fine but at the end the velocity keep +3 then 0 non-stop even the ball has stopped bouncing. How should I modify the code to fix this issue? ballPos = D3DXVECTOR2( 50, 100 ); velocity = 0; accelaration = 3.0f; isBallUp = false; void GameClass::Update() { velocity += accelaration; ballPos.y += velocity; if ( ballPos.y >= 590 ) isBallUp = true; else isBallUp = false; if ( isBallUp ) { ballPos.y = 590; velocity *= -1; } // Graphics Rendering m_Graphics.BeginFrame(); ComposeFrame(); m_Graphics.EndFrame(); }

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• Bending of track in a racing game

  - by caius

  I am trying to create a small racing game in which the track would be modeled using a BSpline curve for the path's center line and directional vectors to define the 'bending' of the track at each point. My problem is that I don't know how to calculate the correct bending / slope of the curve, in such a way that it would be optimal or at least visually nice for a car to 'bend in the corner'. My idea was to use the direction of the 2nd derivatives of the curve, however while this approach looks fine for most of the track, there are points in which the 2nd derivative makes sharp 'twists' / very quick 180 degree flips. I also read about 'knots' of bsplines, but I don't know if such 'twist' in 2nd derivatives is a knot or knots are something else. Can you tell me that using a BSpline: 1. How could I calculate a visually nice bending of a track for a racing game? 2. Is it possible to do this by using some simple calculations of centripertal force / gravity? 3. Is it possible to do this by using 1st, 2nd and 3rd derivatives of the BSpline curve? I am not looking for the 'physically correct' bending angle for the track, I would just like to create something which is visually pleasing in a simple game. I am using a framework which has a built-in class for BSpline, including support for 1st, 2nd and 3rd derivatives of the curve.

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• Bullet Physics implementing custom MotionState class

  - by Arosboro

  I'm trying to make my engine's camera a kinematic rigid body that can collide into other rigid bodies. I've overridden the btMotionState class and implemented setKinematicPos which updates the motion state's tranform. I use the overridden class when creating my kinematic body, but the collision detection fails. I'm doing this for fun trying to add collision detection and physics to Sean O' Neil's Procedural Universe I referred to the bullet wiki on MotionStates for my CPhysicsMotionState class. If it helps I can add the code for the Planetary rigid bodies, but I didn't want to clutter the post. Here is my motion state class: class CPhysicsMotionState: public btMotionState { protected: // This is the transform with position and rotation of the camera CSRTTransform* m_srtTransform; btTransform m_btPos1; public: CPhysicsMotionState(const btTransform &initialpos, CSRTTransform* srtTransform) { m_srtTransform = srtTransform; m_btPos1 = initialpos; } virtual ~CPhysicsMotionState() { // TODO Auto-generated destructor stub } virtual void getWorldTransform(btTransform &worldTrans) const { worldTrans = m_btPos1; } void setKinematicPos(btQuaternion &rot, btVector3 &pos) { m_btPos1.setRotation(rot); m_btPos1.setOrigin(pos); } virtual void setWorldTransform(const btTransform &worldTrans) { btQuaternion rot = worldTrans.getRotation(); btVector3 pos = worldTrans.getOrigin(); m_srtTransform->m_qRotate = CQuaternion(rot.x(), rot.y(), rot.z(), rot.w()); m_srtTransform->SetPosition(CVector(pos.x(), pos.y(), pos.z())); m_btPos1 = worldTrans; } }; I add a rigid body for the camera: // Create rigid body for camera btCollisionShape* cameraShape = new btSphereShape(btScalar(5.0f)); btTransform startTransform; startTransform.setIdentity(); // forgot to add this line CVector vCamera = m_srtCamera.GetPosition(); startTransform.setOrigin(btVector3(vCamera.x, vCamera.y, vCamera.z)); m_msCamera = new CPhysicsMotionState(startTransform, &m_srtCamera); btScalar tMass(80.7f); bool isDynamic = (tMass != 0.f); btVector3 localInertia(0,0,0); if (isDynamic) cameraShape->calculateLocalInertia(tMass,localInertia); btRigidBody::btRigidBodyConstructionInfo rbInfo(tMass, m_msCamera, cameraShape, localInertia); m_rigidBody = new btRigidBody(rbInfo); m_rigidBody->setCollisionFlags(m_rigidBody->getCollisionFlags() | btCollisionObject::CF_KINEMATIC_OBJECT); m_rigidBody->setActivationState(DISABLE_DEACTIVATION); This is the code in Update() that runs each frame: CSRTTransform srtCamera = CCameraTask::GetPtr()->GetCamera(); Quaternion qRotate = srtCamera.m_qRotate; btQuaternion rot = btQuaternion(qRotate.x, qRotate.y, qRotate.z, qRotate.w); CVector vCamera = CCameraTask::GetPtr()->GetPosition(); btVector3 pos = btVector3(vCamera.x, vCamera.y, vCamera.z); CPhysicsMotionState* cameraMotionState = CCameraTask::GetPtr()->GetMotionState(); cameraMotionState->setKinematicPos(rot, pos);

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• Rotate object Up/Down/Left/Right in any orientation

  - by George Duckett

  I'm rendering model at the origin with a fixed camera looking at it positioned on the z axis. I want to be able to rotate the model up/down and left/right. Currently I have 2 variables, HorizontalRotation and VerticalRotation. When calculating the world matrix I rotate about the Y axis by HorizontalRotation and about the X axis by VerticalRotation. The ..Rotation variables are controlled by pressing up/down/left/right arrow keys. The problem I'm having is that the rotations are happening relative to the object. Lets say it's a model of the world. Pressing Up a bit would let me look at the north pole. Currently when i press right the earth spins infront of the camera on its axis; I'm still looking at the north pole. How can i get it so that no matter what rotations are currently applied i can always rotate my model relative to the camera/world axis?

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