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  • Rotating a cube using jBullet collisions

    - by Kenneth Bray
    How would one go about rotating/flipping a cube with the physics of jBullet? Here is my Draw method for my cube object: public void Draw() { // center point posX, posY, posZ float radius = .25f;//size / 2; glPushMatrix(); glBegin(GL_QUADS); //top { glColor3f(5.0f,1.0f,5.0f); // white glVertex3f(posX + radius, posY + radius, posZ - radius); glVertex3f(posX - radius, posY + radius, posZ - radius); glVertex3f(posX - radius, posY + radius, posZ + radius); glVertex3f(posX + radius, posY + radius, posZ + radius); } //bottom { glColor3f(1.0f,1.0f,0.0f); // ?? color glVertex3f(posX + radius, posY - radius, posZ + radius); glVertex3f(posX - radius, posY - radius, posZ + radius); glVertex3f(posX - radius, posY - radius, posZ - radius); glVertex3f(posX + radius, posY - radius, posZ - radius); } //right side { glColor3f(1.0f,0.0f,1.0f); // ?? color glVertex3f(posX + radius, posY + radius, posZ + radius); glVertex3f(posX + radius, posY - radius, posZ + radius); glVertex3f(posX + radius, posY - radius, posZ - radius); glVertex3f(posX + radius, posY + radius, posZ - radius); } //left side { glColor3f(0.0f,1.0f,1.0f); // ?? color glVertex3f(posX - radius, posY + radius, posZ - radius); glVertex3f(posX - radius, posY - radius, posZ - radius); glVertex3f(posX - radius, posY - radius, posZ + radius); glVertex3f(posX - radius, posY + radius, posZ + radius); } //front side { glColor3f(0.0f,0.0f,1.0f); // blue glVertex3f(posX + radius, posY + radius, posZ + radius); glVertex3f(posX - radius, posY + radius, posZ + radius); glVertex3f(posX - radius, posY - radius, posZ + radius); glVertex3f(posX + radius, posY - radius, posZ + radius); } //back side { glColor3f(0.0f,1.0f,0.0f); // green glVertex3f(posX + radius, posY - radius, posZ - radius); glVertex3f(posX - radius, posY - radius, posZ - radius); glVertex3f(posX - radius, posY + radius, posZ - radius); glVertex3f(posX + radius, posY + radius, posZ - radius); } glEnd(); glPopMatrix(); Update(); } This is my update method for the cube position: public void Update() { Transform trans = new Transform(); cubeRigidBody.getMotionState().getWorldTransform(trans); posX = trans.origin.x; posY = trans.origin.y; posZ = trans.origin.z; Quat4f outRot = new Quat4f(); trans.getRotation(outRot); rotX = outRot.x; rotY = outRot.y; rotZ = outRot.z; rotW = outRot.w; } I am assuming I need to use glrotatef, but it does not seem to work at all when I try that.. this is how I have tried to rotate the cubes: GL11.glRotatef(rotW, rotX, 0.0f, 0.0f); GL11.glRotatef(rotW, 0.0f, rotY, 0.0f); GL11.glRotatef(rotW, 0.0f, 0.0f, rotZ);

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  • What is the cost of custom made 2D game sprites? [closed]

    - by Michael Harroun
    Possible Duplicate: How much to pay for artwork in an indie game? I am looking for sprites similar in style to those of Final fantasy Tactics, but with a much higher resolution that will work well for both a browser and an iPhone. In terms of animations: Walking in 4 directions Swinging with 1 hand Some sort of "casting animation" (depending on cost I may use the 1 hand swing with a wand). Taking a hit Kneeling Fallen How much would something like that cost per sprite?

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  • Java Slick2d - Mouse picking how to take into account camera

    - by Corey
    When I move it it obviously changes the viewport so my mouse picking is off. My camera is just a float x and y and I use g.translate(-cam.cameraX+400, -cam.cameraY+300); to translate the graphics. I have the numbers hard coded just for testing purposes. How would I take into account the camera so my mouse picking works correctly. double mousetileX = Math.floor((double)mouseX/tiles.tileWidth); double mousetileY = Math.floor((double)mouseY/tiles.tileHeight); double playertileX = Math.floor(playerX/tiles.tileWidth); double playertileY = Math.floor(playerY/tiles.tileHeight); double lengthX = Math.abs((float)playertileX - mousetileX); double lengthY = Math.abs((float)playertileY - mousetileY); double distance = Math.sqrt((lengthX*lengthX)+(lengthY*lengthY)); if(input.isMousePressed(Input.MOUSE_LEFT_BUTTON) && distance < 4) { if(tiles.map[(int)mousetileX][(int)mousetileY] == 1) { tiles.map[(int)mousetileX][(int)mousetileY] = 0; } } That is my mouse picking code

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  • Splitting a texture atlas into seperate images

    - by bigtunacan
    I'm doing a port of an existing game and the designer no longer has all of the original art; he only has the resulting texture atlases he used when developing for iPad. The tool I'm using won't support these files so I need to break them back out into separate PNG files. I'm hoping someone knows of a software tool that does this. PC software would be preferred in this case, but Mac would suffice.

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  • Scaling along an arbitrary axis (Dealing with non-uniform scale)

    - by Jon
    I'm trying to build my own little engine to get more familiar with the concepts of 3D programming. I have a transform class that on each frame it creates a Scaling Matrix (S), a Rotation Matrix from a Quaternion (R) and concatenates them together (S*R). Once i have SR, I insert the translation values into the bottom of the three columns. So i end up with a transformation matrix that looks like: [SR SR SR 0] [SR SR SR 0] [SR SR SR 0] [tx ty tz 1] This works perfectly in all cases except when rotating an object that has a non-uniform scale. For example a unit cube with ScaleX = 4, ScaleY = 2, ScaleZ = 1 will give me a rectangular box that is 4 times as wide as the depth and twice as high as the depth. If i then translate this around, the box stays the same and looks normal. The problem happens whenever I try to rotate this scaled box. The shape itself becomes distorted and it appears as though the Scale factors are affecting the object on the World X,Y,Z axis rather than the local X,Y,Z axis of the object. I've done some pretty extensive research through a variety of textbooks (Eberly, Moller/Hoffman, Phar etc) and there isn't a ton there to go off of. Online, most of the answers say to avoid non-uniform scaling which I understand the desire to avoid it, but I'd still like to figure out how to support it. The only thing I can think off is that when constructing a Scale Matrix: [sx 0 0 0] [0 sy 0 0] [0 0 sz 0] [0 0 0 1] This is scaling along the World Axis instead of the object's local Direction, Up and Right vectors or it's local Z, Y, X axis. Does anyone have any tips or ideas on how to handle construction a transformation matrix that allows for non-uniform scaling and rotation? Thanks!

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  • GAME MAKER Problem with sprites! Can't see the sprite after mouse action

    - by user46882
    I have got a problem in Game Maker Pro: http://www.directupload.net/file/d/3646/egdpdu6u_gif.htm At the start we see a white square moving. If I press a key the square stop to move and the background changes to white. If the background changes to white a new animation/sprite should play on the same position where the white square was. BUT IT DOESNT! (Actually it is still there! It just does not move and this is fine) The animation is basically a sprite animation with some outlines of the square. If I press a key again, the background changes to white and we see the animation of the sprite.. but we do not see the animation of the sprites when it does not move. And this is strange!! I want to have the animation of the square when it doesn't move. But I don't get it.. by the way.. the .gif is a old version. I allready fixed the problem with the moving animation.. but I am still not able to play the animation if the square does not fly. The color of the animation is allready set to green or something! for better contrast. But still.. can't see it. Here is the code: obj.weisse.kugel.stepevent = the white square with the movements and sprite animations etc. if (global.kweiss == 1 ) { // vspeed = 8; //visible = true // sprite_index=spr_weisse_kugel; image_speed = 0; image_index = 0; } else if (global.kweiss == 0) { sprite_index=spr_animation_fade_out; image_speed =0.2; image_index=image_number-1 vspeed = 0; //visible = false // } then I have 1 create event for all the global.variables obj.global_var globalvar kweiss; kweiss = 1; globalvar kschwarz; kschwarz = 0; and then I have 1 controll stepevent in a new obj: if device_mouse_check_button_pressed (0, mb_left) { if background_color = c_black { background_color = c_white } else { background_color = c_black } // change of the square to white if (global.kweiss = 0) { global.kweiss = 1; } else { global.kweiss = 0; } if (global.kschwarz = 0) // change the square to black (other bullets.. we do not need this at the moment!) { global.kschwarz = 1; } else { global.kschwarz = 0; } Many thanks in advance

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  • How to create a copy of an instance without having access to private variables

    - by Jamie
    Im having a bit of a problem. Let me show you the code first: public class Direction { private CircularList xSpeed, zSpeed; private int[] dirSquare = {-1, 0, 1, 0}; public Direction(int xSpeed, int zSpeed){ this.xSpeed = new CircularList(dirSquare, xSpeed); this.zSpeed = new CircularList(dirSquare, zSpeed); } public Direction(Point dirs){ this(dirs.x, dirs.y); } public void shiftLeft(){ xSpeed.shiftLeft(); zSpeed.shiftRight(); } public void shiftRight(){ xSpeed.shiftRight(); zSpeed.shiftLeft(); } public int getXSpeed(){ return this.xSpeed.currentValue(); } public int getZSpeed(){ return this.zSpeed.currentValue(); } } Now lets say i have an instance of Direction: Direction dir = new Direction(0, 0); As you can see in the code of Direction, the arguments fed to the constructor, are passed directly to some other class. One cannot be sure if they stay the same because methods shiftRight() and shiftLeft could have been called, which changes thos numbers. My question is, how do i create a completely new instance of Direction, that is basically copy(not by reference) of dir? The only way i see it, is to create public methods in both CircularList(i can post the code of this class, but its not relevant) and Direction that return the variables needed to create a copy of the instance, but this solution seems really dirty since those numbers are not supposed to be touched after beeing fed to the constructor, and therefore they are private.

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  • Procedural object generation and unique identification

    - by 2080
    My question relates to procedural content generation and data management of the emerging objects in a database. I assume a networked game, with a server-client model. Unspecified objects in the game world are generated while the game is running with procedural algorithms (for example perlin noise). The players (/clients) can modify the properties of these objects, but have to notify the server of these changes. How could this communication address unique objects, so that both the server and the client know of which object they are speaking? Not only the inner properties of the objects can differ, but also visible, such as the position. When the player wants to select one of these objects the game has to find out the id - does anyone know which methods or algorithms can accomplish that?

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  • what's wrong with this Lua code (creating text inside listener in Corona)

    - by Greg
    If you double/triple click on the myObject here the text does NOT disappear. Why is this not working when there are multiple events being fired? That is, are there actually multiple "text" objects, with some existing but no longer having a reference to them held by the local "myText" variable? Do I have to manually removeSelf() on the local "myText" field before assigning it another "display.newText(...)"? display.setStatusBar( display.HiddenStatusBar ) local myText local function hideMyText(event) print ("hideMyText") myText.isVisible = false end local function showTextListener(event) if event.phase == "began" then print("showTextListener") myText = display.newText("Hello World!", 0, 0, native.systemFont, 30) timer.performWithDelay(1000, hideMyText, 1 ) end end -- Display object to press to show text local myObject = display.newImage( "inventory_button.png", display.contentWidth/2, display.contentHeight/2) myObject:addEventListener("touch", showTextListener) Question 2 - Also why is it the case that if I add a line BEFORE "myText = ..." of: a) "if myText then myText:removeSelf() end" = THIS FIXES THINGS, whereas b) "if myText then myText=nil end" = DOES NOT FIX THINGS Interested in hearing how Lua works here re the answer...

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  • 2D Animation Smoothness - Delta time vs. Kinematics

    - by viperld002
    I'm animating a sprite in 2D with key frames of rotation and xy-positions. I've recently had a discussion with someone saying that when the device (happens to be an iPad using cocos2D) hits a performance bump due to whatever else the user may be doing, lag will arise and that the best way to fight it is to not use actual positions, but velocities, accelerations and torques with kinematics. His message is to evaluate the positions and rotations from these speeds at the current point in time. I've never experienced a situation where I've heard of using kinematics to stem lag in 2D animations and am not sure of how effective it could be. Also, it seems to be overkill. The application is not networked so it's all running on a local device. The desired effect is that the animation always plays as closely as it can to the target frame rate. Wouldn't the technique suffer the same problems as just using the time since the last frame or a fixed time step since the kinematics would also require some time value to perform the calculation? What techniques could you suggest to best achieve the desired effect? EDIT 1 Thank you for your responses, they are very illuminating. I want to clarify my question before choosing an answer however, to make sure that this post really serves it's purpose. I have a sprite of a ball, and a text file with 3 arrays worth of information (rotation,translations x, translations y) with each unit of information existing as a key frame to be stepped through (0 to 49 and back to 0 to replay it again). I have this playing by interpolating from the current key frame to the next, every n-units of time. The animation is visibly correct when compared to a video I was given of it, and it is smooth because of the interpolations between the key frames. This is the existing state of the project. There are no physics simulated, only a static animation of a ball moving in a way an artist specifically designed. Should I, instead of rotation in degrees and translations by positions in space, derive velocities, accelerations and torques to express this static animation as a function of time? As in, position now = foo(time now), where foo uses kinematics.

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  • Behaviour tree code example?

    - by jokoon
    http://altdevblogaday.org/2011/02/24/introduction-to-behavior-trees/ Obviously the most interesting article I found on this website. What do you think about it ? It lacks some code example, don't you know any ? I also read that state machines are not very flexible compared to behaviour trees... On top of that I'm not sure if there is a true link between state machines and the state pattern... is there ?

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  • About online game servers and how to handle data

    - by TreantBG
    So my question isn't about what technology to use or how to do this or that, but a more general question. I'm currently developing a action third person shooter. With elements of RPG - weapon,armor upgrades and items. Players will be able to create new games or join old ones. So my question is how to create the game server that players will play in. I have two ideas on my mind. The player who made the game is the server. All data passes trough him and he send this data to the server updating the database of the players with their XP points kills/deaths score and other. Or my host machine is the server, the player who made the game just will open new instance on my host and will be like client. And all players send their input data to the host, the host updates the game and send response back to client for any new changes like where is the enemy and other. And if i choose option 1 is there a chance the host to change the game content and manipulate the game results? (I think there is but i'm not sure) And if i choose option 2 isn't that raising the response time and potentially the game lag? or maybe there is another option?

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  • What should I worry about when changing OpenGL origin to upper left of screen?

    - by derivative
    For self education, I'm writing a 2D platformer engine in C++ using SDL / OpenGL. I initially began with pure SDL using the tutorials on sdltutorials.com and lazyfoo.net, but I'm now rendering in an OpenGL context (specifically immediate mode but I'm learning about VAOs/VBOs) and using SDL for interface, audio, etc. SDL uses a coordinate system with the origin in the upper left of the screen and the positive y-axis pointing down. It's easy to set up my orthographic projection in OpenGL to mirror this. I know that texture coordinates are a right-hand system with values from 0 to 1 -- flipping the texture vertically before rendering (well, flip the file before loading) yields textures that render correctly... which is fine if I'm drawing the entire texture, but ultimately I'll be using tilesets and can imagine problems. What should I be concerned about in terms of rendering when I do this? If anybody has any advice or they've done this themselves and can point out future pitfalls, that would be great, but really any thoughts would be appreciated.

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  • How can I improve my isometric tile-picking algorithm?

    - by Cypher
    I've spent the last few days researching isometric tile-picking algorithms (converting screen-coordinates to tile-coordinates), and have obviously found a lot of the math beyond my grasp. I have come fairly close and what I have is workable, but I would like to improve on this algorithm as it's a little off and seems to pick down and to the right of the mouse pointer. I've uploaded a video to help visualize the current implementation: http://youtu.be/EqwWcq1zuaM My isometric rendering algorithm is based on what is found at this stackoverflow question's answer, with the exception that my x and y axis' are inverted (x increased down-right, while y increased up-right). Here is where I am converting from screen to tiles: // these next few lines convert the mouse pointer position from screen // coordinates to tile-grid coordinates. cameraOffset captures the current // mouse location and takes into consideration the camera's position on screen. System.Drawing.Point cameraOffset = new System.Drawing.Point( 0, 0 ); cameraOffset.X = mouseLocation.X + (int)camera.Left; cameraOffset.Y = ( mouseLocation.Y + (int)camera.Top ); // the camera-aware mouse coordinates are then further converted in an attempt // to select only the "tile" portion of the grid tiles, instead of the entire // rectangle. this algorithm gets close, but could use improvement. mouseTileLocation.X = ( cameraOffset.X + 2 * cameraOffset.Y ) / Global.TileWidth; mouseTileLocation.Y = -( ( 2 * cameraOffset.Y - cameraOffset.X ) / Global.TileWidth ); Things to make note of: mouseLocation is a System.Drawing.Point that represents the screen coordinates of the mouse pointer. cameraOffset is the screen position of the mouse pointer that includes the position of the game camera. mouseTileLocation is a System.Drawing.Point that is supposed to represent the tile coordinates of the mouse pointer. If you check out the above link to youtube, you'll notice that the picking algorithm is off a bit. How can I improve on this?

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  • Victory rewards in digital CCG

    - by Nils Munch
    I am currently polishing a digital CCG where people can play against friend and random opponents in a classical Magic the Gathering-like duel CCG. I plan to award the players with 20 ingame currency units (lets call them gold) for each hour they are playing, 50 for each day they are playing and X for each victory. Now, the X is what I am trying to calculate here, since I would prefer keeping the currency to a certain value, but also with to entice the players to battle. I could go with a solid figure, say 25, for beating up an opponent. But that would result in experienced players only beating up newly started players, making the experience lame for both. I could also make a laddered tier, where you start at level 1, and raise in level as you defeat your opponents, where winning over a player awards you his level x 2 in gold. Which would you prefer if you were playing a game like this. There is no gold-based scoreboard, but the gold is used to purchase new cards along the way.

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  • vector collision on polygon in 3d space detection/testing?

    - by LRFLEW
    In the 3d fps in java I'm working on, I need a bullet to be fired and to tell if it hit someone. All visual objects in the game are defined through OpenGL, so the object it can be colliding with can be any drawable polygon (although they will most likely be triangles and rectangles anyways). The bullet is not an object, but will be treated as a vector that instantaneously moves all the way across the map (like the snipper riffle in Halo). What's the best way to detect/test collisions with the polygon and the vector. I have access to OpenCL, however I have absolutely no experience with it. I am very early in the developmental stage, so if you think there's a better way of going about this, feel free to tell me (I barley have a player model to collide with anyways, so I'm flexible with it). Thanks

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  • Slerping rotation mirrors

    - by Esa
    I rotate my game character to watch at the target using the following code: transform.rotation = Quaternion.Slerp(startQuaternion, lookQuaternion, turningNormalizer*turningSpeed/10f) startQuaternion is the character's current rotation when a new target is given. lookQuaternion is the direction the character should look at and it's set like this: destinationVector = currentWaypoint.transform.position - transform.position; lookQuaternion = Quaternion.LookRotation(destinationVector, Vector3.up); turningNormalizer is just Time.deltaTime incremented and turningSpeed is a static value given in the editor. The problem is that while the character turns as it should most of the time, it has problems when it has to do close to 180 degrees. Then it at times jitters and mirrors the rotation: In this poorly drawn image the character(on the right) starts to turn towards the circle on the left. Instead of just turning either through left or right it starts this "mirror dance": It starts to rotate towards the new facing Then it suddenly snaps to the same angle but on other side and keeps rotating It does this "mirroring" so long until it looks at the target. Is this a thing with quaternions, slerping/lerping or something else?

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  • How do you set up PhysFS for use in a game?

    - by ThePlan
    After my recent question on GD I've been advised to use PhysFS to pack all my game data in 1 file. So I have, and the decission wasn't light, because I've tried out every library in my answers but none contained a single good tutorial whatsoever, in fact PhysFS is the poorest documented library I've ever seen. After attempting to set up PhysFS in my game I realized it's not as simple as adding the headers to the project, it appears something much more complicated, in fact after my first attempt to install PhysFS the compiler ran out of memory to display errors, it reached the critical count of 50 errors. So basically what I'm asking here is: How can I set up PhysFS on my game? I'm using Code::Blocks IDE on Windows XP SP3;

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  • Moving 2d camera in the y direction

    - by Alex
    I'm developing a simple game for the iphone and am struggling to work out the best way for the camera to follow the main character. The following picture hightlights the three main components: There are 3 components to this: Circle - the main character Green line - terrain Black background The terrain is simply made from an array of points (approx 20 points per screen width). The terrain is moved in the x direction relative to the black background in order to keep the circle in its position shown. The distance to move the terrain is simply: movex = circle.position.x - terrain.position.x with a constant to fix the circle at some distance from the left of the screen. I am struggling to determine the best way to position the terrain in the y plane keep the focus in the character. I want to move the terrain in the y direction smoothly and not fix it to the position of the circle, so the circle can move in the y plane. If I take the same approach as the x positioning, the character is fixed at a point on the screen and the terrain moves. I could sample some terrain points either side of the character and produce an average, but in my implementation this was not smooth. I thought another approach might be to create a camera 'line' that is a smooth version of the terrain line and make the camerea follow this, but I'm not sure if this is the optimum solution. Any advice is much appreciated!

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  • Reversi/Othello early-game evaluation function

    - by Vladislav Il'ushin
    I've written my own Reversi player, based on the MiniMax algorithm, with Alpha-Beta pruning, but in the first 10 moves my evaluation function is too slow. I need a good early-game evaluation function. I'm trying to do it with this matrix (corresponding to the board) which determines how favourable that square is to have: { 30, -25, 10, 5, 5, 10, -25, 30,}, {-25, -25, 1, 1, 1, 1, -25, -25,}, { 10, 1, 5, 2, 2, 5, 1, 10,}, { 5, 1, 2, 1, 1, 2, 1, 5,}, { 5, 1, 2, 1, 1, 2, 1, 5,}, { 10, 1, 5, 2, 2, 5, 1, 10,}, {-25, -25, 1, 1, 1, 1, -25, -25,}, { 30, -25, 10, 5, 5, 10, -25, 30,},}; But it doesn't work well. Have you even written an early-game evaluation function for Reversi?

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  • Square game map rendered as sphere with OpenGL

    - by Roflha
    Okay so I have been trying to find a good way to do this for a while now and so far I have nothing. For a hobby project of mine I have created a finite voxel world (similar to minecraft), but as I said, mine is finite. When you reach the edge of it, you are sent to the other side. That is all working fine along with rendering the far side of the map, but I want to be able to render this grid as a sphere. Looking down from above, the world is a square. I basically want to be able to represent a portion of that square as a sphere, as if you were looking at a planet. Right now I am experimenting with taking a circular section of the map, and rendering that, but it look to flat (no curvature around the edges). My question then, is what would be the best way to add some curvature to the edges of a 2d circle to make it look like a hemisphere. However, I am not overly attached to this implementation so if somebody has some other idea for representing the square as a planet, I am all ears.

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  • Making body(box2d) a spite(andengine) in android

    - by Kadir
    I can't make body(box2d) a spite(andengine) and at the same time i wanna apply MoveModifier to sprite which is body.if i can make just body,it works namely the srites can collide.if i can apply just MoveModifier to sprites,the sprites can move where i want.but i wanna make body(they can collide) and apply MoveModifier(they can move where i want) at the same time.How can i do? this my code just run MoveModifier not as body at the same time. circles[i] = new Sprite(startX, startY, textRegCircle[i]); body[i] = PhysicsFactory.createCircleBody(physicsWorld, circles[i], BodyType.DynamicBody, FIXTURE_DEF); physicsWorld.registerPhysicsConnector(new PhysicsConnector(circles[i], body[i], true, true)); circles[i].registerEntityModifier( (IEntityModifier) new SequenceEntityModifier ( new MoveModifier(10.0f, circles[i].getX(), circles[i].getX(), circles[i].getY(),CAMERA_HEIGHT+64.0f))); scene.getLastChild().attachChild(circles[i]); scene.registerUpdateHandler(physicsWorld);

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  • Circle-Line Collision Detection Problem

    - by jazzdawg
    I am currently developing a breakout clone and I have hit a roadblock in getting collision detection between a ball (circle) and a brick (convex polygon) working correctly. I am using a Circle-Line collision detection test where each line represents and edge on the convex polygon brick. For the majority of the time the Circle-Line test works properly and the points of collision are resolved correctly. Collision detection working correctly. However, occasionally my collision detection code returns false due to a negative discriminant when the ball is actually intersecting the brick. Collision detection failing. I am aware of the inefficiency with this method and I am using axis aligned bounding boxes to cut down on the number of bricks tested. My main concern is if there are any mathematical bugs in my code below. /* * from and to are points at the start and end of the convex polygons edge. * This function is called for every edge in the convex polygon until a * collision is detected. */ bool circleLineCollision(Vec2f from, Vec2f to) { Vec2f lFrom, lTo, lLine; Vec2f line, normal; Vec2f intersectPt1, intersectPt2; float a, b, c, disc, sqrt_disc, u, v, nn, vn; bool one = false, two = false; // set line vectors lFrom = from - ball.circle.centre; // localised lTo = to - ball.circle.centre; // localised lLine = lFrom - lTo; // localised line = from - to; // calculate a, b & c values a = lLine.dot(lLine); b = 2 * (lLine.dot(lFrom)); c = (lFrom.dot(lFrom)) - (ball.circle.radius * ball.circle.radius); // discriminant disc = (b * b) - (4 * a * c); if (disc < 0.0f) { // no intersections return false; } else if (disc == 0.0f) { // one intersection u = -b / (2 * a); intersectPt1 = from + (lLine.scale(u)); one = pointOnLine(intersectPt1, from, to); if (!one) return false; return true; } else { // two intersections sqrt_disc = sqrt(disc); u = (-b + sqrt_disc) / (2 * a); v = (-b - sqrt_disc) / (2 * a); intersectPt1 = from + (lLine.scale(u)); intersectPt2 = from + (lLine.scale(v)); one = pointOnLine(intersectPt1, from, to); two = pointOnLine(intersectPt2, from, to); if (!one && !two) return false; return true; } } bool pointOnLine(Vec2f p, Vec2f from, Vec2f to) { if (p.x >= min(from.x, to.x) && p.x <= max(from.x, to.x) && p.y >= min(from.y, to.y) && p.y <= max(from.y, to.y)) return true; return false; }

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  • Managing multiple references of the same game entity in different places using IDs

    - by vargonian
    I've seen great questions on similar topics, but none that addressed this particular method: Given that I have multiple collections of game entities in my [XNA Game Studio] game, with many entities belonging to multiple lists, I'm considering ways I could keep track of whenever an entity is destroyed and remove it from the lists it belongs to. A lot of potential methods seem sloppy/convoluted, but I'm reminded of a way I've seen before in which, instead of having multiple collections of game entities, you have collections of game entity IDs instead. These IDs map to game entities via a central "database" (perhaps just a hash table). So, whenever any bit of code wants to access a game entity's members, it first checks to see if it's even in the database still. If not, it can react accordingly. Is this a sound approach? It seems that it would eliminate many of the risks/hassles of storing multiple lists, with the tradeoff being the cost of the lookup every time you want to access an object.

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  • Why is my model's scale changing after rotating it?

    - by justnS
    I have just started a simple flight simulator and have implemented Roll and pitch. In the beginning, testing went very well; however, after about 15-20 seconds of constantly moving the thumbsticks in a random or circular motion, my model's scale begins to grow. At first I thought the model was moving closer to the camera, but i set break points when it was happening and can confirm the translation of my orientation matrix remains 0,0,0. Is this a result of Gimbal Lock? Does anyone see an obvious error in my code below? public override void Draw( Matrix view, Matrix projection ) { Matrix[] transforms = new Matrix[Model.Bones.Count]; Model.CopyAbsoluteBoneTransformsTo( transforms ); Matrix translateMatrix = Matrix.Identity * Matrix.CreateFromAxisAngle( _orientation.Right, MathHelper.ToRadians( pitch ) ) * Matrix.CreateFromAxisAngle( _orientation.Down, MathHelper.ToRadians( roll ) ); _orientation *= translateMatrix; foreach ( ModelMesh mesh in Model.Meshes ) { foreach ( BasicEffect effect in mesh.Effects ) { effect.World = _orientation * transforms[mesh.ParentBone.Index]; effect.View = view; effect.Projection = projection; effect.EnableDefaultLighting(); } mesh.Draw(); } } public void Update( GamePadState gpState ) { roll = 5 * gpState.ThumbSticks.Left.X; pitch = 5 * gpState.ThumbSticks.Left.Y; }

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