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  • Circle to Circle collision, checking each circle against all others

    - by user14861
    I'm currently coding a little circle to circle collision demo but I've got a little stuck. I think I currently have the code to detect collision but I'm not sure how to loop through my list of circles and check them off against one another. Collision check code: public static Vector2 GetIntersectionDepth(Circle a, Circle b) { float xValue = a.Center.X - b.Center.X; float yValue = a.Center.Y - b.Center.Y; Vector2 depth = Vector2.Zero; float distance = Vector2.Distance(a.Center, b.Center); if (a.Radius + b.Radius > distance) { float result = (a.Radius + b.Radius) - distance; depth.X = (float)Math.Cos(result); depth.Y = (float)Math.Sin(result); } return depth; } Loop through code: Vector2 depth = Vector2.Zero; for (int i = 0; i < bounds.Count; i++) for (int j = i+1; j < bounds.Count; j++) { depth = CircleToCircleIntersection.GetIntersectionDepth(bounds[i], bounds[j]); } Clearly I'm a complete newbie, wondering if anyone can give any suggestions or point out my errors, thanks in advance. :)

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  • Matrix.CreateBillboard centre rotation problem

    - by Chris88
    I'm having an issue with Matrix.CreateBillboard and a textured Quad where the center axis seems to be positioned incorrectly to the quad object which is rotating around a center point: Using: BasicEffect quadEffect; Drawing the quad shape: Left = Vector3.Cross(Normal, Up); Vector3 uppercenter = (Up * height / 2) + origin; LowerLeft = uppercenter + (Left * width / 2); LowerRight = uppercenter - (Left * width / 2); UpperLeft = LowerLeft - (Up * height); UpperRight = LowerRight - (Up * height); Where height and width are float values passed in (it draws a square) Draw method: quadEffect.View = camera.view; quadEffect.Projection = camera.projection; quadEffect.World = Matrix.CreateBillboard(Origin, camera.cameraPosition, Vector3.Up, camera.cameraDirection); GraphicsDevice.BlendState = BlendState.Additive; foreach (EffectPass pass in quadEffect.CurrentTechnique.Passes) { pass.Apply(); GraphicsDevice.DrawUserIndexedPrimitives <VertexPositionNormalTexture>( PrimitiveType.TriangleList, Vertices, 0, 4, Indexes, 0, 2); } GraphicsDevice.BlendState = BlendState.Opaque; In the screenshots below i draw the image at Vector3(32f, 0f, 32f) The screenshots below show you the position of the quad in relation to the red cross. The red cross shows where it should be drawn http://i.imgur.com/YwRYj.jpg http://i.imgur.com/ZtoHL.jpg It rotates around the red cross position

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  • How do I pass an object location into a vertex shader?

    - by Greg Kassapidis
    I am using Blender Game Engine. I want to create a large flat plane, and deform it locally near a moving object. So far (despite being a beginner at shaders) I've written a vertex shader for the plane which moves the vertices to their correct positions (constant positions, for now). I cannot find a way to swap that constant location with an object's location updated every frame, while the shader is running. I am not even sure if it's possible. I only want to access a specific object's center from the shader.

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  • Units issue when exporting from 3DS Max to XNA

    - by miguelSantirso
    I am working on a XNA game where we have defined that 1 XNA unit equals to 1 meter. Then, I set meters as system unit in 3DS Max and set to meters the units in the FBX exporter. However, when I export my models, they are much bigger in the game. Am I missing something? What should I do to avoid problems with my units? Investigating the FBX file, I noticed that I it has two values called UnitScaleFactor and OriginalUnitScaleFactor. They both are 100 when I export the files... And if I manually change UnitScaleFactor to 1, it works fine :S

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  • What makes puzzle games addictive?

    - by Bryan Denny
    I'm currently developing a puzzle game for Android that is sort of along the lines of Alchemy. I was wondering what makes games like Alchemy or Bejeweled so addicting? How do I keep players interested in the game to want to play it over and over? Is it the scores? Level advancement? The challenges? What should I be doing to try and keep a player engaged with a puzzle game since they are often quite repetitive?

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  • Can I use PBOs for textures in iOS?

    - by Radu
    As far as I can see, there is no GL_PIXEL_UNPACK_BUFFER. Also, the OpenGL ES 2.0 specification (and as far as I know, no iOS device currently supports OpenGL ES 2.0) states that glMapBufferOES() can only use GL_ARRAY_BUFFER as a target, yet glTexImage2D() and glTexSubImage2D() only seem to use PBOs if GL_PIXEL_UNPACK_BUFFER is bound. The OpenGL documentation for glBindBuffer() also states that: GL_PIXEL_PACK_BUFFER and GL_PIXEL_UNPACK_BUFFER are available only if the GL version is 2.1 or greater. So, can I use PBOs for textures? Am I missing something obvious?

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  • Level and Player objects - which should contain which?

    - by Thane Brimhall
    I've been working on a several simple games, and I've always come to a decision point where I have to choose whether to have the Level object as an attribute of the Player class or the Player as an attribute of the Level class. I can see arguments for both: The Level should contain the player because it also contains every other entity. In fact it just makes sense this way: "John is in the room." It makes it a bit more difficult to move the player to a new level, however, because then each level has to pass its player object to an upcoming level. On the other hand, it makes programming sense to me to leave the player as the top-level object that is persistent between levels, and the environment changes because the player decides to change his level and location. It becomes very easy to change levels, because all I have to do is replace the level variable on the player. What's the most common practice here? Or better yet, is there a "right" way to architecture this relationship?

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  • Accelerating 2d object collision with other objects [on hold]

    - by Silent Cave
    Making my very first attempt at game programming with SDL/OpenGL. So I made an object Actor witch can move in all four sides with acceleration. And there are bunch of other rectangles to collide to. the image Movement and collision detection alghorythms work just fine by itself, but when combined to prevent the green rectangle from crossing black rectangles, it gives me a kind of funny resault. Let me show you the code first: from Actor.h class Actor{ public: SDL_Rect * dim; alphaColor * col; float speed; float xlGrav, xrGrav, yuGrav, ydGrav; float acceleration; bool left,right,up,down; Actor(SDL_Rect * dim,alphaColor * col, float speed, float acceleration); bool colides(const SDL_Rect & rect); bool check_for_collisions(const std::vector<SDL_Rect*> & gameObjects ); }; from actor.cpp bool Actor::colides(const SDL_Rect & rect){ if (dim->x + dim->w < rect.x) return false; if (dim->x > rect.x + rect.w) return false; if (dim->y + dim->h < rect.y) return false; if (dim->y > rect.y + rect.h) return false; return true; } movement logic from main.cpp if (actor->left){ if(actor->xlGrav < actor->speed){ actor->xlGrav += actor->speed*actor->acceleration; }else actor->xlGrav = actor->speed; actor->dim->x -= actor->xlGrav; if(actor->check_for_collisions(gameObjects)){ actor->dim->x += actor->xlGrav; actor->xlGrav = 0; } } if (!actor->left){ if(actor->xlGrav - actor->speed*actor->acceleration > 0){ actor->xlGrav -= actor->speed*actor->acceleration; }else actor->xlGrav = 0; actor->dim->x -= actor->xlGrav; if(actor->check_for_collisions(gameObjects)){ actor->dim->x += actor->xlGrav; actor->xlGrav = 0; } } if (actor->right){ if(actor->xrGrav < actor->speed){ actor->xrGrav += actor->speed*actor->acceleration; }else actor->xrGrav = actor->speed; actor->dim->x += actor->xrGrav; if(actor->check_for_collisions(gameObjects)){ actor->dim->x -= actor->xrGrav; actor->xrGrav = 0; } } if (!actor->right){ if(actor->xrGrav - actor->speed*actor->acceleration > 0){ actor->xrGrav -= actor->speed*actor->acceleration; }else actor->xrGrav = 0; actor->dim->x += actor->xrGrav; if(actor->check_for_collisions(gameObjects)){ actor->dim->x -= actor->xrGrav; actor->xrGrav = 0; } } if (actor->up){ if(actor->yuGrav < actor->speed){ actor->yuGrav += actor->speed*actor->acceleration; }else actor->yuGrav = actor->speed; actor->dim->y -= actor->yuGrav; if(actor->check_for_collisions(gameObjects)){ actor->dim->y += actor->yuGrav; actor->yuGrav = 0; } } if (!actor->up){ if(actor->yuGrav - actor->speed*actor->acceleration > 0){ actor->yuGrav -= actor->speed*actor->acceleration; }else actor->yuGrav = 0; actor->dim->y -= actor->yuGrav; if(actor->check_for_collisions(gameObjects)){ actor->dim->y += actor->yuGrav; actor->yuGrav = 0; } } if (actor->down){ if(actor->ydGrav < actor->speed){ actor->ydGrav += actor->speed*actor->acceleration; }else actor->ydGrav = actor->speed; actor->dim->y += actor->ydGrav; if(actor->check_for_collisions(gameObjects)){ actor->dim->y -= actor->ydGrav; actor->ydGrav = 0; } } if (!actor->down){ if(actor->ydGrav - actor->speed*actor->acceleration > 0){ actor->ydGrav -= actor->speed*actor->acceleration; }else actor->ydGrav = 0; actor->dim->y += actor->ydGrav; if(actor->check_for_collisions(gameObjects)){ actor->dim->y -= actor->ydGrav; actor->ydGrav = 0; } } So, if the green box approaches an obstacle from up or left, everything goes as planned - object stops, and it's acceleration drops to zero. But if it comes from bottom or right, it enters into obstacles inner space and starts strangely dance, I'd rather say move in inverted controls. What do I fail to see?

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  • Drawing an animation over an already drawn screen

    - by Chandan Pednekar
    I am working on a XNA WP7 card game whose basic prototype is complete. In game screen, 6 cards are displayed at a time (3 for each of the two players say 1,2 and 3). If player A attacks one of player B's card then I want to show an animation over player B's card i.e the victim card(say a claw scratch for e.g.) My question is how do I approach with the animation system so that I can draw an animation over a card upon certain events e.g. dead, fire, claw attack etc. I have an attack function which detects which type of card is attacking which type of card. Depending on the type of attacker card I want to display the animation on the victim card. Can I call animation classes function for different animations in the attack function itself without actually having to call separate draw and update functions. If so, how? Also how do I play sound at the same time when the animation is going on?

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  • Resources on expected behaviour when manipulating 3D objects with the mouse

    - by sebf
    Hello, In my animation editor, I have a 3D gizmo that sits on the origin of a bone; the user drags the mesh around to rotate the bone. I've found that translating the 2D movements of the mouse into sensible 3D transforms is not near as simple as i'd hoped. For example what is intuitively 'up' or 'down'? How should the magnitude of rotations change with respect to dX/dY? How to implement this? What happens when the gizmo changes position or orientation with respect to the camera? ect. So far with trial and error i've written something (very) simple that works 70% of the time. I could probably continue to hack at it until I made something that works 99% of the time, but there must be someone who needed the same thing, and spent the time coming up with a much more elegant solution. Does anyone know of one?

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  • Java applet game design no keyboard focus

    - by Sri Harsha Chilakapati
    THIS IS PROBABLY THE WRONG PLACE. POSTED ITHERE (STACKOVERFLOW) I'm making an applet game and it is rendering, the game loop is running, the animations are updating, but the keyboard input is not working. Here's an SSCCE. public class Game extends JApplet implements Runnable { public void init(){ // Initialize the game when called by browser setFocusable(true); requestFocus(); requestFocusInWindow(); // Always returning false GInput.install(this); // Install the input manager for this class new Thread(this).start(); } public void run(){ startGameLoop(); } } And Here's the GInput class. public class GInput implements KeyListener { public static void install(Component c){ new GInput(c); } public GInput(Component c){ c.addKeyListener(this); } public void keyPressed(KeyEvent e){ System.out.println("A key has been pressed"); } ...... } This is my GInput class. When run as an applet, it doesn't work and when I add the Game class to a frame, it works properly. Thanks

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  • Correct order of tasks in each frame for a Physics simulation

    - by Johny
    I'm playing a bit around with 2D physics. I created now some physic blocks which should collide with each other. This works fine "mostly" but sometimes one of the blocks does not react to a collision and i think that's because of my order of tasks done in each frame. At the moment it looks something like this: function GameFrame(){ foreach physicObject do AddVelocityToPosition(); DoCollisionStuff(); // Only for this object not to forget! AddGravitationToVelocity(); end RedrawScene(); } Is this the correct order of tasks in each frame?

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  • Drawing a random x,y grid of objects within a prespective

    - by T Reddy
    I'm wrapping my head around OpenGL ES 2.0 and I think I'm trying to do something very simple, but I think the math may be eluding me. I created a simple, flat-ish cylinder in Blender that is 2 units in diameter. I want to create an arbitrary grid of these edge to edge (think of a checker board). I'm using a 3D perspective with GLKit: CGSize size = [[self view] bounds].size; _projectionMatrix = GLKMatrix4MakePerspective(GLKMathDegreesToRadians(45.0f), size.width/size.height, 0.1f, 100.0f); So, I managed to manually get all of these cylinders drawn on the screen just fine. However, I would like to understand how I can programmatically "fit" all of these cylinders on the screen at the same time given the camera location, screen size, cylinder diameter, and the number of rows/columns. So the net effect is that for small grids (i.e., 5x5) the objects are closer to the camera, but for large grids (i.e., 30x30) the objects are farther away. In either case, all of the cylinders are visible.

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  • dynamic 2d texture creation in unity from script

    - by gman
    I'm coming from HTML5 and I'm used to having the 2D Canvas API I can use to generate textures. Is there anything similar in Unity3D? For example, let's say at runtime I want to render a circle, put 3 initials in the middle and then take the result and put that in a texture. In HTML5 I'd do this var initials = "GAT"; var textureWidth = 256; var textureHeight = 256; // create a canvas var c = document.createElement("canvas"); c.width = textureWidth; c.height = textureHeight; var ctx = c.getContext("2d"); // Set the origin to the center of the canvas ctx.translate(textureWidth / 2, textureHeight / 2); // Draw a yellow circle ctx.fillStyle = "rgb(255,255,0)"; // yellow ctx.beginPath(); var radius = (Math.min(textureWidth, textureHeight) - 2) / 2; ctx.arc(0, 0, radius, 0, Math.PI * 2, true); ctx.fill(); // Draw some black initials in the middle. ctx.fillStyle = "rgb(0,0,0)"; ctx.font = "60pt Arial"; ctx.textAlign = "center"; ctx.fillText(initials, 0, 30); // now I can make a texture from that var tex = gl.createTexture(); gl.bindTexture(gl.TEXTURE_2D, tex); gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, gl.RGBA, gl.UNSIGNED_BYTE, c); gl.generateMipmap(gl.TEXTURE_2D); I know I can edit individual pixels in a Unity texture but is there any higher level API for drawing to texture in unity?

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  • Isometric algorithm producing tiles in wrong draw order

    - by David
    I've been toying with isometric and I just cant get the tiles to be in the right order. I'm probably missing something obvious and I just can't see it. Even at the risk of looking stupid, here's my code: for (int i = 0; i < Tile.MapSize; i++) { for (int j = 0; j < Tile.MapSize; j++) { spriteBatch.Draw( Tile.TileSetTexture, new Rectangle( (-j * Tile.TileWidth / 2) + (i * Tile.TileWidth / 2), (i * (Tile.TileHeight - 9) / 2) - (-j * (Tile.TileHeight - 9) / 2), Tile.TileWidth, Tile.TileHeight), Tile.GetSourceRectangle(tileID), Color.White, 0.0f, new Vector2(-350, -60), SpriteEffects.None, 1.0f); } } And here's what I end up with: messed up map Yep, bit of an issue. If anyone could help, I'd appreciate it.

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  • Collision with CCSprite

    - by Coder404
    I'm making an iOS app based off the code from here In the .m file of the tutorial is this: -(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]; } if (targetsToDelete.count > 0) { [projectilesToDelete addObject:projectile]; } [targetsToDelete release]; } for (CCSprite *projectile in projectilesToDelete) { [_projectiles removeObject:projectile]; [self removeChild:projectile cleanup:YES]; } [projectilesToDelete release]; } I am trying to take away the projectiles and have the app know when the CCSprite "Player" and the targets collide. Could someone help me with this? Thanks

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  • In esenthel engine how can I remove some object from Gui class?

    - by Gajet
    I know many people in this site may not know esenthel engine at all and my question may be better answered at engine forum but I'm putting it here to share the name of a real easy to code gameengine with all of you: you can easily add a Button for example to your GUI class (gui is it's shared instance) with Gui += buttonInstance.create("click on me") but I'm just wondering how can you remove an on object from from Gui members. as far as I know there is no such a method as removeChild or getChildren or anything similar.

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  • how to generate random bubbles from array of sprites in cocos2d?

    - by prakash s
    I am devoloping the bubble shooter game in cocos2d how to generate random bubbles from array of sprites here is my code (void)addTarget { CGSize winSize = [[CCDirector sharedDirector] winSize]; //CCSprite *target = [CCSprite spriteWithFile:@"3.png" rect:CGRectMake(0, 0, 256, 256)]; NSMutableArray * movableSprites = [[NSMutableArray alloc] init]; NSArray *images = [NSArray arrayWithObjects:@"1.png", @"2.png", @"3.png", @"4.png",@"5.png",@"1.png",@"5.png", @"3.png", nil]; for(int i = 0; i < images.count; ++i) { NSString *image = [images objectAtIndex:i]; // generate random number based on size of array (array size is larger than 10) CCSprite*target = [CCSprite spriteWithFile:image]; float offsetFraction = ((float)(i+1))/(images.count+1); target.position = ccp(winSize.width*offsetFraction, winSize.height/2); target.position = ccp(350*offsetFraction, 460); [self addChild:target]; [movableSprites addObject:target]; //[target runAction:]; id actionMove = [CCMoveTo actionWithDuration:10 position:ccp(winSize.width/2,winSize. height/2)]; This code generating bubbles with *.png colour bubbles but i want to generate randomly because for shooting the bubbles by shooter class help me please id actionMoveDone = [CCCallFuncN actionWithTarget:self selector:@selector(spriteMoveFinished:)]; [target runAction:[CCSequence actions:actionMove, actionMoveDone, nil]]; } }

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  • Playing part of a sfx audio file in HTML5 using WebAudio

    - by Matthew James Davis
    I have compiled all of my sound effects into one sequenced .ogg file. I have the start and stop times for each sound effect. How do I play the individual effects? That is, how do I play part of an audio file. More specificially, I've created a dictionary { 'sword_hit': { src: 'sfx.ogg', start: 265, // ms length: 212 // ms } } that my play_sound() function can use to look up 'sword_hit' and play the correct audio file at the correct start time for the correct duration. I simply need to know how to tell the WebAudio API to start playing at start ms and only play for length ms.

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  • Lock mouse in center of screen, and still use to move camera Unity

    - by Flotolk
    I am making a program from 1st person point of view. I would like the camera to be moved using the mouse, preferably using simple code, like from XNA var center = this.Window.ClientBounds; MouseState newState = Mouse.GetState(); if (Keyboard.GetState().IsKeyUp(Keys.Escape)) { Mouse.SetPosition((int)center.X, (int)center.Y); camera.Rotation -= (newState.X - center.X) * 0.005f; camera.UpDown += (newState.Y - center.Y) * 0.005f; } Is there any code that lets me do this in Unity, since Unity does not support XNA, I need a new library to use, and a new way to collect this input. this is also a little tougher, since I want one object to go up and down based on if you move it the mouse up and down, and another object to be the one turning left and right. I am also very concerned about clamping the mouse to the center of the screen, since you will be selecting items, and it is easiest to have a simple cross-hairs in the center of the screen for this purpose. Here is the code I am using to move right now: using UnityEngine; using System.Collections; [AddComponentMenu("Camera-Control/Mouse Look")] public class MouseLook : MonoBehaviour { public enum RotationAxes { MouseXAndY = 0, MouseX = 1, MouseY = 2 } public RotationAxes axes = RotationAxes.MouseXAndY; public float sensitivityX = 15F; public float sensitivityY = 15F; public float minimumX = -360F; public float maximumX = 360F; public float minimumY = -60F; public float maximumY = 60F; float rotationY = 0F; void Update () { if (axes == RotationAxes.MouseXAndY) { float rotationX = transform.localEulerAngles.y + Input.GetAxis("Mouse X") * sensitivityX; rotationY += Input.GetAxis("Mouse Y") * sensitivityY; rotationY = Mathf.Clamp (rotationY, minimumY, maximumY); transform.localEulerAngles = new Vector3(-rotationY, rotationX, 0); } else if (axes == RotationAxes.MouseX) { transform.Rotate(0, Input.GetAxis("Mouse X") * sensitivityX, 0); } else { rotationY += Input.GetAxis("Mouse Y") * sensitivityY; rotationY = Mathf.Clamp (rotationY, minimumY, maximumY); transform.localEulerAngles = new Vector3(-rotationY, transform.localEulerAngles.y, 0); } while (Input.GetKeyDown(KeyCode.Space) == true) { Screen.lockCursor = true; } } void Start () { // Make the rigid body not change rotation if (GetComponent<Rigidbody>()) GetComponent<Rigidbody>().freezeRotation = true; } } This code does everything except lock the mouse to the center of the screen. Screen.lockCursor = true; does not work though, since then the camera no longer moves, and the cursor does not allow you to click anything else either.

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  • Having troubles with LibNoise.XNA and generating tileable maps

    - by Jon
    Following up on my previous post, I found a wonderful port of LibNoise for XNA. I've been working with it for about 8 hours straight and I'm tearing my hair out - I just can not get maps to tile, I can't figure out how to do this. Here's my attempt: Perlin perlin = new Perlin(1.2, 1.95, 0.56, 12, 2353, QualityMode.Medium); RiggedMultifractal rigged = new RiggedMultifractal(); Add add = new Add(perlin, rigged); // Initialize the noise map int mapSize = 64; this.m_noiseMap = new Noise2D(mapSize, perlin); //this.m_noiseMap.GeneratePlanar(0, 1, -1, 1); // Generate the textures this.m_noiseMap.GeneratePlanar(-1,1,-1,1); this.m_textures[0] = this.m_noiseMap.GetTexture(this.graphics.GraphicsDevice, Gradient.Grayscale); this.m_noiseMap.GeneratePlanar(mapSize, mapSize * 2, mapSize, mapSize * 2); this.m_textures[1] = this.m_noiseMap.GetTexture(this.graphics.GraphicsDevice, Gradient.Grayscale); this.m_noiseMap.GeneratePlanar(-1, 1, -1, 1); this.m_textures[2] = this.m_noiseMap.GetTexture(this.graphics.GraphicsDevice, Gradient.Grayscale); The first and third ones generate fine, they create a perlin noise map - however the middle one, which I wanted to be a continuation of the first (As per my original post), is just a bunch of static. How exactly do I get this to generate maps that connect to each other, by entering in the mapsize * tile, using the same seed, settings, etc.?

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  • SWF file not playing after being published

    - by rsquare
    I'm trying to run the "connector" example that comes bundled with the SmartFoxServer 2X downloads.. There it connects to the server and loads the correct configuration file. When I run it in Adobe Flash Professional 5, it runs correctly and connects to the server but after being published as SWF movie, it doesnt work. It loads the configuration file but can't connect and gives an error connection failure: ERROR 2048. This is the example I'm talking about.

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  • Sharing VBO with multiple objects and fixed size buffer data

    - by Mark Ingram
    I'm just messing around with OpenGL and getting some basic structures in place and my first attempt resulted in each SceneObject class (just contains vertex information right now) having it's own VBO inside it, however I've read that it might be better to share VBOs across multiple objects. Also, I read that you should avoid resizing a VBO (repeated calls to glBufferData with different size parameters), and instead choose a fixed size for a VBO, and just try a range from the buffer. I don't think changing the size of the buffer data would happen too often, but surely it would be better to only allocate the data you need? Choosing an arbitrary value seems risky. I'm looking for some advice on working with individual objects in a scene and their associated buffer data.

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  • Why do we use Pythagoras in game physics?

    - by Starkers
    I've recently learned that we use Pythagoras a lot in our physics calculations and I'm afraid I don't really get the point. Here's an example from a book to make sure an object doesn't travel faster than a MAXIMUM_VELOCITY constant in the horizontal plane: MAXIMUM_VELOCITY = <any number>; SQUARED_MAXIMUM_VELOCITY = MAXIMUM_VELOCITY * MAXIMUM_VELOCITY; function animate(){ var squared_horizontal_velocity = (x_velocity * x_velocity) + (z_velocity * z_velocity); if( squared_horizontal_velocity <= SQUARED_MAXIMUM_VELOCITY ){ scalar = squared_horizontal_velocity / SQUARED_MAXIMUM_VELOCITY; x_velocity = x_velocity / scalar; z_velocity = x_velocity / scalar; } } Let's try this with some numbers: An object is attempting to move 5 units in x and 5 units in z. It should only be able to move 5 units horizontally in total! MAXIMUM_VELOCITY = 5; SQUARED_MAXIMUM_VELOCITY = 5 * 5; SQUARED_MAXIMUM_VELOCITY = 25; function animate(){ var x_velocity = 5; var z_velocity = 5; var squared_horizontal_velocity = (x_velocity * x_velocity) + (z_velocity * z_velocity); var squared_horizontal_velocity = 5 * 5 + 5 * 5; var squared_horizontal_velocity = 25 + 25; var squared_horizontal_velocity = 50; // if( squared_horizontal_velocity <= SQUARED_MAXIMUM_VELOCITY ){ if( 50 <= 25 ){ scalar = squared_horizontal_velocity / SQUARED_MAXIMUM_VELOCITY; scalar = 50 / 25; scalar = 2.0; x_velocity = x_velocity / scalar; x_velocity = 5 / 2.0; x_velocity = 2.5; z_velocity = z_velocity / scalar; z_velocity = 5 / 2.0; z_velocity = 2.5; // new_horizontal_velocity = x_velocity + z_velocity // new_horizontal_velocity = 2.5 + 2.5 // new_horizontal_velocity = 5 } } Now this works well, but we can do the same thing without Pythagoras: MAXIMUM_VELOCITY = 5; function animate(){ var x_velocity = 5; var z_velocity = 5; var horizontal_velocity = x_velocity + z_velocity; var horizontal_velocity = 5 + 5; var horizontal_velocity = 10; // if( horizontal_velocity >= MAXIMUM_VELOCITY ){ if( 10 >= 5 ){ scalar = horizontal_velocity / MAXIMUM_VELOCITY; scalar = 10 / 5; scalar = 2.0; x_velocity = x_velocity / scalar; x_velocity = 5 / 2.0; x_velocity = 2.5; z_velocity = z_velocity / scalar; z_velocity = 5 / 2.0; z_velocity = 2.5; // new_horizontal_velocity = x_velocity + z_velocity // new_horizontal_velocity = 2.5 + 2.5 // new_horizontal_velocity = 5 } } Benefits of doing it without Pythagoras: Less lines Within those lines, it's easier to read what's going on ...and it takes less time to compute, as there are less multiplications Seems to me like computers and humans get a better deal without Pythagoras! However, I'm sure I'm wrong as I've seen Pythagoras' theorem in a number of reputable places, so I'd like someone to explain me the benefit of using Pythagoras to a maths newbie. Does this have anything to do with unit vectors? To me a unit vector is when we normalize a vector and turn it into a fraction. We do this by dividing the vector by a larger constant. I'm not sure what constant it is. The total size of the graph? Anyway, because it's a fraction, I take it, a unit vector is basically a graph that can fit inside a 3D grid with the x-axis running from -1 to 1, z-axis running from -1 to 1, and the y-axis running from -1 to 1. That's literally everything I know about unit vectors... not much :P And I fail to see their usefulness. Also, we're not really creating a unit vector in the above examples. Should I be determining the scalar like this: // a mathematical work-around of my own invention. There may be a cleverer way to do this! I've also made up my own terms such as 'divisive_scalar' so don't bother googling var divisive_scalar = (squared_horizontal_velocity / SQUARED_MAXIMUM_VELOCITY); var divisive_scalar = ( 50 / 25 ); var divisive_scalar = 2; var multiplicative_scalar = (divisive_scalar / (2*divisive_scalar)); var multiplicative_scalar = (2 / (2*2)); var multiplicative_scalar = (2 / 4); var multiplicative_scalar = 0.5; x_velocity = x_velocity * multiplicative_scalar x_velocity = 5 * 0.5 x_velocity = 2.5 Again, I can't see why this is better, but it's more "unit-vector-y" because the multiplicative_scalar is a unit_vector? As you can see, I use words such as "unit-vector-y" so I'm really not a maths whiz! Also aware that unit vectors might have nothing to do with Pythagoras so ignore all of this if I'm barking up the wrong tree. I'm a very visual person (3D modeller and concept artist by trade!) and I find diagrams and graphs really, really helpful so as many as humanely possible please!

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  • Math > Logic for a Logarithmic Score Meter

    - by oodavid
    I'm trying to implement a score meter whereby I specify a maximum value (say 15,000) and I can render values on it in a logarithmic manner ie: +------+---+--+-++ +------+---+--+-++ |== | |====== | +------+---+--+-++ +------+---+--+-++ 200 pts 1,000 pts +------+---+--+-++ +------+---+--+-++ |============= | |================| +------+---+--+-++ +------+---+--+-++ 5,000 pts 15,000 pts + The upper bound needs to be variable, and need to be able to convert a score to a percentage, using the above mockup as an example: score2pct(15000, 200) = 0.2 score2pct(15000, 1000) = 0.4 score2pct(15000, 5000) = 0.8 score2pct(15000, 15000) = 1 Does anyone have any pointers for me?

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