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• CoreStore Encryption Error on Mac Lion

  - by Michael

  I am trying to encrypt an external drive using diskutil CoreStorage on Mac Lion 10.7.4. I thought the only requirements were that the drive have GUID partition scheme and Journaled HFS+ file system. I think my drive is configured accordingly but when I type the following command I get an error message back: Michaels-MacBook-Pro:~ Michael$ diskutil cs convert disk2 -passphrase TestPassword Error converting disk to CoreStorage: The given file system is not supported on Core Storage (-69756) Here are the details reported for the drive in question: Michaels-MacBook-Pro:~ Michael$ diskutil list disk2 /dev/disk2 #: TYPE NAME SIZE IDENTIFIER 0: GUID_partition_scheme *500.1 GB disk2 1: EFI 209.7 MB disk2s1 2: Apple_HFS Test1 499.8 GB disk2s2 Michaels-MacBook-Pro:~ Michael$ diskutil list disk2 /dev/disk2 #: TYPE NAME SIZE IDENTIFIER 0: GUID_partition_scheme *500.1 GB disk2 1: EFI 209.7 MB disk2s1 2: Apple_HFS Test1 499.8 GB disk2s2 Michaels-MacBook-Pro:~ Michael$ diskutil info disk2s2 Device Identifier: disk2s2 Device Node: /dev/disk2s2 Part of Whole: disk2 Device / Media Name: Test1 Volume Name: Test1 Escaped with Unicode: Test1 Mounted: Yes Mount Point: /Volumes/Test1 Escaped with Unicode: /Volumes/Test1 File System Personality: Journaled HFS+ Type (Bundle): hfs Name (User Visible): Mac OS Extended (Journaled) Journal: Journal size 40960 KB at offset 0xe8e000 Owners: Disabled Partition Type: Apple_HFS OS Can Be Installed: Yes Media Type: Generic Protocol: FireWire SMART Status: Not Supported Volume UUID: 1024D0B8-1C45-3057-B040-AE5C3841DABF Total Size: 499.8 GB (499763888128 Bytes) (exactly 976101344 512-Byte-Blocks) Volume Free Space: 499.3 GB (499315826688 Bytes) (exactly 975226224 512-Byte-Blocks) Device Block Size: 512 Bytes Read-Only Media: No Read-Only Volume: No Ejectable: Yes Whole: No Internal: No I'm a little concerned that the "Partition Type: Apple_HFS" entry is causing the problem, but I don't know how to change that. I only seem to be able to control the "File System Personality: Journaled HFS+" in Disk Utility. Can anyone shed some light on this for me?

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• Optimized algorithm for line-sphere intersection in GLSL

  - by fernacolo

  Well, hello then! I need to find intersection between line and sphere in GLSL. Right now my solution is based on Paul Bourke's page and was ported to GLSL this way: // The line passes through p1 and p2: vec3 p1 = (...); vec3 p2 = (...); // Sphere center is p3, radius is r: vec3 p3 = (...); float r = ...; float x1 = p1.x; float y1 = p1.y; float z1 = p1.z; float x2 = p2.x; float y2 = p2.y; float z2 = p2.z; float x3 = p3.x; float y3 = p3.y; float z3 = p3.z; float dx = x2 - x1; float dy = y2 - y1; float dz = z2 - z1; float a = dx*dx + dy*dy + dz*dz; float b = 2.0 * (dx * (x1 - x3) + dy * (y1 - y3) + dz * (z1 - z3)); float c = x3*x3 + y3*y3 + z3*z3 + x1*x1 + y1*y1 + z1*z1 - 2.0 * (x3*x1 + y3*y1 + z3*z1) - r*r; float test = b*b - 4.0*a*c; if (test >= 0.0) { // Hit (according to Treebeard, "a fine hit"). float u = (-b - sqrt(test)) / (2.0 * a); vec3 hitp = p1 + u * (p2 - p1); // Now use hitp. } It works perfectly! But it seems slow... I'm new at GLSL. You can answer this questions in two ways: Tell me there is no solution, showing some proof or strong evidence. Tell me about GLSL features (vector APIs, primitive operations) that makes the above algorithm faster, showing some example. Thanks a lot!

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• Detecting walls or floors in pygame

  - by Serial

  I am trying to make bullets bounce of walls, but I can't figure out how to correctly do the collision detection. What I am currently doing is iterating through all the solid blocks and if the bullet hits the bottom, top or sides, its vector is adjusted accordingly. However, sometimes when I shoot, the bullet doesn't bounce, I think it's when I shoot at a border between two blocks. Here is the update method for my Bullet class: def update(self, dt): if self.can_bounce: #if the bullet hasnt bounced find its vector using the mousclick pos and player pos speed = -10. range = 200 distance = [self.mouse_x - self.player[0], self.mouse_y - self.player[1]] norm = math.sqrt(distance[0] ** 2 + distance[1] ** 2) direction = [distance[0] / norm, distance[1 ] / norm] bullet_vector = [direction[0] * speed, direction[1] * speed] self.dx = bullet_vector[0] self.dy = bullet_vector[1] #check each block for collision for block in self.game.solid_blocks: last = self.rect.copy() if self.rect.colliderect(block): topcheck = self.rect.top < block.rect.bottom and self.rect.top > block.rect.top bottomcheck = self.rect.bottom > block.rect.top and self.rect.bottom < block.rect.bottom rightcheck = self.rect.right > block.rect.left and self.rect.right < block.rect.right leftcheck = self.rect.left < block.rect.right and self.rect.left > block.rect.left each test tests if it hit the top bottom left or right side of the block its colliding with if self.can_bounce: if topcheck: self.rect = last self.dy *= -1 self.can_bounce = False print "top" if bottomcheck: self.rect = last self.dy *= -1 #Bottom check self.can_bounce = False print "bottom" if rightcheck: self.rect = last self.dx *= -1 #right check self.can_bounce = False print "right" if leftcheck: self.rect = last self.dx *= -1 #left check self.can_bounce = False print "left" else: # if it has already bounced and colliding again kill it self.kill() for enemy in self.game.enemies_list: if self.rect.colliderect(enemy): self.kill() #update position self.rect.x -= self.dx self.rect.y -= self.dy This definitely isn't the best way to do it but I can't think of another way. If anyone has done this or can help that would be awesome!

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• Trouble with speed and vectors

  - by Eegabooga

  I'm working on adding bullets to my game. Right now I can shoot bullets in the direction that I would like from a ship by getting the ship's angle: int speed = 5; int dx = -(cos(degreesToRadians(ship.angle)) * speed); // rate of change in the x direction int dy = -(sin(degreesToRadians(ship.angle)) * speed); // rate of change in the y direction bulletPosition.addX(dx); // addX(dx) is simply bulletPosition.x += dx bulletPosition.addY(dy); The ship is pretty much the exact same thing, except I use the += operator: int dx += -(cos(degreesToRadians(angle)) * 0.15) int dy += -(sin(degreesToRadians(angle)) * 0.15); shipPosition.addX(dx); shipPosition.addY(dy); I would like to be able to add the ship's velocity to the bullet's velocity, but I'm a little confused as to how should get the speed from the ship's vector. I thought that adding the ship's dx to the bullet's dx like int dx = -(cos(degreesToRadians(ship.angle)) * speed * dx) would work because I'm adding the rate of change of the ship to the rate of change of the bullet, but that doesn't work. So here's the final question: How can I get the speed of my ship and apply it to my bullet's speed? Thanks in advance for all help :)

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• LibGDX onTouch() method kill on touch

  - by johnny-b

  How can I add this on my application. i want to use the onTouch() method from the implementation of the InputProcessor to kill the enemies on screen. how do i do that? do i have to do anything to the enemy class? please help Thank you M @Override public boolean touchDown(int screenX, int screenY, int pointer, int button) { return false; } here is my enemy class public class Bullet extends Sprite { private Vector2 velocity; private float lifetime; public Bullet(float x, float y) { velocity = new Vector2(0, 0); } public void update(float delta) { float targetX = GameWorld.getBall().getX(); float targetY = GameWorld.getBall().getY(); float dx = targetX - getX(); float dy = targetY - getY(); float distToTarget = (float) Math.sqrt(dx * dx + dy * dy); velocity.x += dx * delta; velocity.y += dy * delta; } } i am rendering all graphics in a GameRender class and a gameworld class if you need more info please let me know Thank you

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• My raycaster is putting out strange results, how do I fix it?

  - by JamesK89

  I'm working on a raycaster in ActionScript 3.0 for the fun of it, and as a learning experience. I've got it up and running and its displaying me output as expected however I'm getting this strange bug where rays go through corners of blocks and the edges of blocks appear through walls. Maybe somebody with more experience can point out what I'm doing wrong or maybe a fresh pair of eyes can spot a tiny bug I haven't noticed. Thank you so much for your help! Screenshots: http://i55.tinypic.com/25koebm.jpg http://i51.tinypic.com/zx5jq9.jpg Relevant code: function drawScene() { rays.graphics.clear(); rays.graphics.lineStyle(1, rgba(0x00,0x66,0x00)); var halfFov = (player.fov/2); var numRays:int = ( stage.stageWidth / COLUMN_SIZE ); var prjDist = ( stage.stageWidth / 2 ) / Math.tan(toRad( halfFov )); var angStep = ( player.fov / numRays ); for( var i:int = 0; i < numRays; i++ ) { var rAng = ( ( player.angle - halfFov ) + ( angStep * i ) ) % 360; if( rAng < 0 ) rAng += 360; var ray:Object = castRay(player.position, rAng); drawRaySlice(i*COLUMN_SIZE, prjDist, player.angle, ray); } } function drawRaySlice(sx:int, prjDist, angle, ray:Object) { if( ray.distance >= MAX_DIST ) return; var height:int = int(( TILE_SIZE / (ray.distance * Math.cos(toRad(angle-ray.angle))) ) * prjDist); if( !height ) return; var yTop = int(( stage.stageHeight / 2 ) - ( height / 2 )); if( yTop < 0 ) yTop = 0; var yBot = int(( stage.stageHeight / 2 ) + ( height / 2 )); if( yBot > stage.stageHeight ) yBot = stage.stageHeight; rays.graphics.moveTo( (ray.origin.x / TILE_SIZE) * MINI_SIZE, (ray.origin.y / TILE_SIZE) * MINI_SIZE ); rays.graphics.lineTo( (ray.hit.x / TILE_SIZE) * MINI_SIZE, (ray.hit.y / TILE_SIZE) * MINI_SIZE ); for( var x:int = 0; x < COLUMN_SIZE; x++ ) { for( var y:int = yTop; y < yBot; y++ ) { buffer.setPixel(sx+x, y, clrTable[ray.tile-1] >> ( ray.horz ? 1 : 0 )); } } } function castRay(origin:Point, angle):Object { // Return values var rTexel = 0; var rHorz = false; var rTile = 0; var rDist = MAX_DIST + 1; var rMap:Point = new Point(); var rHit:Point = new Point(); // Ray angle and slope var ra = toRad(angle) % ANGLE_360; if( ra < ANGLE_0 ) ra += ANGLE_360; var rs = Math.tan(ra); var rUp = ( ra > ANGLE_0 && ra < ANGLE_180 ); var rRight = ( ra < ANGLE_90 || ra > ANGLE_270 ); // Ray position var rx = 0; var ry = 0; // Ray step values var xa = 0; var ya = 0; // Ray position, in map coordinates var mx:int = 0; var my:int = 0; var mt:int = 0; // Distance var dx = 0; var dy = 0; var ds = MAX_DIST + 1; // Horizontal intersection if( ra != ANGLE_180 && ra != ANGLE_0 && ra != ANGLE_360 ) { ya = ( rUp ? TILE_SIZE : -TILE_SIZE ); xa = ya / rs; ry = int( origin.y / TILE_SIZE ) * ( TILE_SIZE ) + ( rUp ? TILE_SIZE : -1 ); rx = origin.x + ( ry - origin.y ) / rs; mx = 0; my = 0; while( mx >= 0 && my >= 0 && mx < world.size.x && my < world.size.y ) { mx = int( rx / TILE_SIZE ); my = int( ry / TILE_SIZE ); mt = getMapTile(mx,my); if( mt > 0 && mt < 9 ) { dx = rx - origin.x; dy = ry - origin.y; ds = ( dx * dx ) + ( dy * dy ); if( rDist >= MAX_DIST || ds < rDist ) { rDist = ds; rTile = mt; rMap.x = mx; rMap.y = my; rHit.x = rx; rHit.y = ry; rHorz = true; rTexel = int(rx % TILE_SIZE) } break; } rx += xa; ry += ya; } } // Vertical intersection if( ra != ANGLE_90 && ra != ANGLE_270 ) { xa = ( rRight ? TILE_SIZE : -TILE_SIZE ); ya = xa * rs; rx = int( origin.x / TILE_SIZE ) * ( TILE_SIZE ) + ( rRight ? TILE_SIZE : -1 ); ry = origin.y + ( rx - origin.x ) * rs; mx = 0; my = 0; while( mx >= 0 && my >= 0 && mx < world.size.x && my < world.size.y ) { mx = int( rx / TILE_SIZE ); my = int( ry / TILE_SIZE ); mt = getMapTile(mx,my); if( mt > 0 && mt < 9 ) { dx = rx - origin.x; dy = ry - origin.y; ds = ( dx * dx ) + ( dy * dy ); if( rDist >= MAX_DIST || ds < rDist ) { rDist = ds; rTile = mt; rMap.x = mx; rMap.y = my; rHit.x = rx; rHit.y = ry; rHorz = false; rTexel = int(ry % TILE_SIZE); } break; } rx += xa; ry += ya; } } return { angle: angle, distance: Math.sqrt(rDist), hit: rHit, map: rMap, tile: rTile, horz: rHorz, origin: origin, texel: rTexel }; }

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• libgdx rotation (animation, arrays) issues and help needed

  - by johnny-b

  well i am a noob at java and libgdx. i got the homing bullet working with the help of someone. now i am smashing my head as to how i can make it rotate so it faces the ball (which is the main character) when it goes around it or when it is coming towards it. the bullet is facing <--- and the code below is what i have done so far. also i used sprites for the bullet and also animation method. Also how do i make it an array/arraylist which is best so i can have multiple bullets at random or placed places. i tried many things nothing workd :( thank you for the help. // below is the bullet or enemy if you want to call it. public class Bullet extends Sprite { public static final float BULLET_HOMING = 6000; public static final float BULLET_SPEED = 300; private Vector2 velocity; private float lifetime; public Bullet(float x, float y) { velocity = new Vector2(0, 0); setPosition(x, y); } public void update(float delta) { float targetX = GameWorld.getBall().getX(); float targetY = GameWorld.getBall().getY(); float dx = targetX - getX(); float dy = targetY - getY(); float distToTarget = (float) Math.sqrt(dx * dx + dy * dy); dx /= distToTarget; dy /= distToTarget; dx *= BULLET_HOMING; dy *= BULLET_HOMING; velocity.x += dx * delta; velocity.y += dy * delta; float vMag = (float) Math.sqrt(velocity.x * velocity.x + velocity.y * velocity.y); velocity.x /= vMag; velocity.y /= vMag; velocity.x *= BULLET_SPEED; velocity.y *= BULLET_SPEED; Vector2 v = velocity.cpy().scl(delta); setPosition(getX() + v.x, getY() + v.y); setOriginCenter(); setRotation(velocity.angle()); lifetime += delta; setRegion(AssetLoader.bulletAnimation.getKeyFrame(lifetime)); } } // this is where i load the images. public class AssetLoader { public static Animation bulletAnimation; public static Sprite bullet1, bullet2; public static void load() { texture = new Texture(Gdx.files.internal("SpriteN1.png")); texture.setFilter(TextureFilter.Nearest, TextureFilter.Nearest); bullet1 = new Sprite(texture, 380, 350, 45, 20); bullet1.flip(false, true); bullet2 = new Sprite(texture, 425, 350, 45, 20); bullet2.flip(false, true); Sprite[] bullets = { bullet1, bullet2 }; bulletAnimation = new Animation(0.06f, aims); bulletAnimation.setPlayMode(Animation.PlayMode.LOOP); } public static void dispose() { // We must dispose of the texture when we are finished. texture.dispose(); } // this is for the rendering of the images etc public class GameRenderer { private Bullet bullet; private Ball ball; public GameRenderer(GameWorld world) { myWorld = world; cam = new OrthographicCamera(); cam.setToOrtho(true, 480, 320); batcher = new SpriteBatch(); // Attach batcher to camera batcher.setProjectionMatrix(cam.combined); shapeRenderer = new ShapeRenderer(); shapeRenderer.setProjectionMatrix(cam.combined); // Call helper methods to initialize instance variables initGameObjects(); initAssets(); } private void initGameObjects() { ball = GameWorld.getBall(); bullet = myWorld.getBullet(); scroller = myWorld.getScroller(); } private void initAssets() { ballAnimation = AssetLoader.ballAnimation; bulletAnimation = AssetLoader.bulletAnimation; } public void render(float runTime) { Gdx.gl.glClearColor(0, 0, 0, 1); Gdx.gl.glClear(GL30.GL_COLOR_BUFFER_BIT); batcher.begin(); // Disable transparency // This is good for performance when drawing images that do not require // transparency. batcher.disableBlending(); // The ball needs transparency, so we enable that again. batcher.enableBlending(); batcher.draw(AssetLoader.ballAnimation.getKeyFrame(runTime), ball.getX(), ball.getY(), ball.getWidth(), ball.getHeight()); batcher.draw(AssetLoader.bulletAnimation.getKeyFrame(runTime), bullet.getX(), bullet.getY()); // End SpriteBatch batcher.end(); } } // this is to load the image etc on the screen i guess public class GameWorld { public static Ball ball; private Bullet bullet; private ScrollHandler scroller; public GameWorld() { ball = new Ball(480, 273, 32, 32); bullet = new Bullet(10, 10); scroller = new ScrollHandler(0); } public void update(float delta) { ball.update(delta); bullet.update(delta); scroller.update(delta); } public static Ball getBall() { return ball; } public ScrollHandler getScroller() { return scroller; } public Bullet getBullet() { return bullet; } } so there is the whole thing. the images are loaded via the AssetLoader then to the GameRenderer and GameWorld via the Bullet class. i am guessing that is how it is. sorry newbie so still learning. thank you in advace for the help or any advice.

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• Which of these algorithms is best for my goal?

  - by JonathonG

  I have created a program that restricts the mouse to a certain region based on a black/white bitmap. The program is 100% functional as-is, but uses an inaccurate, albeit fast, algorithm for repositioning the mouse when it strays outside the area. Currently, when the mouse moves outside the area, basically what happens is this: A line is drawn between a pre-defined static point inside the region and the mouse's new position. The point where that line intersects the edge of the allowed area is found. The mouse is moved to that point. This works, but only works perfectly for a perfect circle with the pre-defined point set in the exact center. Unfortunately, this will never be the case. The application will be used with a variety of rectangles and irregular, amorphous shapes. On such shapes, the point where the line drawn intersects the edge will usually not be the closest point on the shape to the mouse. I need to create a new algorithm that finds the closest point to the mouse's new position on the edge of the allowed area. I have several ideas about this, but I am not sure of their validity, in that they may have far too much overhead. While I am not asking for code, it might help to know that I am using Objective C / Cocoa, developing for OS X, as I feel the language being used might affect the efficiency of potential methods. My ideas are: Using a bit of trigonometry to project lines would work, but that would require some kind of intense algorithm to test every point on every line until it found the edge of the region... That seems too resource intensive since there could be something like 200 lines that would have each have to have as many as 200 pixels checked for black/white.... Using something like an A* pathing algorithm to find the shortest path to a black pixel; however, A* seems resource intensive, even though I could probably restrict it to only checking roughly in one direction. It also seems like it will take more time and effort than I have available to spend on this small portion of the much larger project I am working on, correct me if I am wrong and it would not be a significant amount of code (100 lines or around there). Mapping the border of the region before the application begins running the event tap loop. I think I could accomplish this by using my current line-based algorithm to find an edge point and then initiating an algorithm that checks all 8 pixels around that pixel, finds the next border pixel in one direction, and continues to do this until it comes back to the starting pixel. I could then store that data in an array to be used for the entire duration of the program, and have the mouse re-positioning method check the array for the closest pixel on the border to the mouse target position. That last method would presumably execute it's initial border mapping fairly quickly. (It would only have to map between 2,000 and 8,000 pixels, which means 8,000 to 64,000 checked, and I could even permanently store the data to make launching faster.) However, I am uncertain as to how much overhead it would take to scan through that array for the shortest distance for every single mouse move event... I suppose there could be a shortcut to restrict the number of elements in the array that will be checked to a variable number starting with the intersecting point on the line (from my original algorithm), and raise/lower that number to experiment with the overhead/accuracy tradeoff. Please let me know if I am over thinking this and there is an easier way that will work just fine, or which of these methods would be able to execute something like 30 times per second to keep mouse movement smooth, or if you have a better/faster method. I've posted relevant parts of my code below for reference, and included an example of what the area might look like. (I check for color value against a loaded bitmap that is black/white.) // // This part of my code runs every single time the mouse moves. // CGPoint point = CGEventGetLocation(event); float tX = point.x; float tY = point.y; if( is_in_area(tX,tY, mouse_mask)){ // target is inside O.K. area, do nothing }else{ CGPoint target; //point inside restricted region: float iX = 600; // inside x float iY = 500; // inside y // delta to midpoint between iX,iY and tX,tY float dX; float dY; float accuracy = .5; //accuracy to loop until reached do { dX = (tX-iX)/2; dY = (tY-iY)/2; if(is_in_area((tX-dX),(tY-dY),mouse_mask)){ iX += dX; iY += dY; } else { tX -= dX; tY -= dY; } } while (abs(dX)>accuracy || abs(dY)>accuracy); target = CGPointMake(roundf(tX), roundf(tY)); CGDisplayMoveCursorToPoint(CGMainDisplayID(),target); } Here is "is_in_area(int x, int y)" : bool is_in_area(NSInteger x, NSInteger y, NSBitmapImageRep *mouse_mask){ NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init]; NSUInteger pixel[4]; [mouse_mask getPixel:pixel atX:x y:y]; if(pixel[0]!= 0){ [pool release]; return false; } [pool release]; return true; }

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• Resolving bounding box collision detection

  - by ndg

  I'm working on a simple collision detection and resolution method for a 2d tile-based bounding box system. Collision appears to work correctly, but I'm having issues with resolving a collision after it has happened. Essentially what I'm attempting to do is very similar to this approach. The problem I'm experiencing is that because objects can be traveling with both horizontal and vertical velocity, my resolution code causes the object to jump incorrectly. I've drawn the following annotation to explain my issue. In this example, because my object has both horizontal and vertical velocity, my object (which is heading upwards and collides with the bottom of a tile) has it's position altered twice: To correctly adjust it's vertical position to be beneath the tile. To incorrectly adjust it's horizontal position to be to the left of the tile. Below is my collision/resolution code in full: function intersects(x1, y1, w1, h1, x2, y2, w2, h2) { w2 += x2; w1 += x1; if (x2 > w1 || x1 > w2) return false; h2 += y2; h1 += y1; if (y2 > h1 || y1 > h2) return false; return true; } for(var y = 0; y < this.game.level.tiles.length; y++) { for(var x = 0; x < this.game.level.tiles[y].length; x++) { var tile = this.game.level.getTile(x, y); if(tile) { if( this.velocity.x > 0 && intersects(this.position.x+dx+this.size.w, this.position.y+dy, 1, this.size.h, x*tileSize, y*tileSize, tileSize, tileSize) ) { this.position.x = ((x*tileSize)-this.size.w); hitSomething = true; break; } else if( this.velocity.x < 0 && intersects(this.position.x+dx, this.position.y+dy, 1, this.size.h, x*tileSize, y*tileSize, tileSize, tileSize) ) { this.position.x = ((x*tileSize)+tileSize); hitSomething = true; break; } if( this.velocity.y > 0 && intersects(this.position.x+dx, this.position.y+dy+this.size.h, this.size.w, 1, x*tileSize, y*tileSize, tileSize, tileSize) ) { this.position.y = ((y*tileSize)-this.size.h); hitSomething = true; break; } else if( this.velocity.y < 0 && intersects(this.position.x+dx, this.position.y+dy, this.size.w, 1, x*tileSize, y*tileSize, tileSize, tileSize) ) { this.position.y = ((y*tileSize)+tileSize); hitSomething = true; break; } } } } if(hitSomething) { this.velocity.x = this.velocity.y = 0; dx = dy = 0; this.setJumping(false); }

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• Determine if getPixel() value is greater than or less than 50% gray

  - by cmal

  I am trying to loop through a bitmap and determine if each pixel is lighter or darker than gray using getPixel(). Problem is, I am not sure how to tell whether the value returned by getPixel() is darker or lighter than gray. Neutral gray is about 0x808080 or R:127, G:127, B:127. How would I need to modify the code below to accurately determine this? for (var dx:int=0; dx < objectWidth; dx++) { for (var dy:int=0; dy < objectHeight; dy++) { if (testBmd.getPixel(dx, dy) > GRAY) { trace("Lighter than gray!"); } else { trace("Darker than gray!"); } } }

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• The Math of a Jump in a 2D game.

  - by ONi

  I have been all around with this question and I can't find the correct answer! So, behold, the description of my question: I'm working in J2ME, I have my gameloop that do the following: public void run() { Graphics g = this.getGraphics(); while (running) { long diff = System.currentTimeMillis() - lastLoop; lastLoop = System.currentTimeMillis(); input(); this.level.doLogic(); render(g, diff); try { Thread.sleep(10); } catch (InterruptedException e) { stop(e); } } } so it's just a basic gameloop, the doLogic() function calls for all the logic functions of the characters in the scene and render(g, diff) calls the animateChar function of every character on scene, following this, the animChar function in the Character class sets up everything in the screen as this: protected void animChar(long diff) { this.checkGravity(); this.move((int) ((diff * this.dx) / 1000), (int) ((diff * this.dy) / 1000)); if (this.acumFrame > this.framerate) { this.nextFrame(); this.acumFrame = 0; } else { this.acumFrame += diff; } } This ensures me that everything must to move according to the time that the machine takes to go from cycle to cycle (remember it's a phone, not a gaming rig). I'm sure it's not the most efficient way to achieve this behavior so I'm totally open for criticism of my programming skills in the comments, but here my problem: When I make I character jump, what I do is that I put his dy to a negative value, say -200 and I set the boolean jumping to true, that makes the character go up, and then I have this function called checkGravity() that ensure that everything that goes up has to go down, checkGravity also checks for the character being over platforms so I will strip it down a little for the sake of your time: public void checkGravity() { if (this.jumping) { this.jumpSpeed += 10; if (this.jumpSpeed > 0) { this.jumping = false; this.falling = true; } this.dy = this.jumpSpeed; } if (this.falling) { this.jumpSpeed += 10; if (this.jumpSpeed > 200) this.jumpSpeed = 200; this.dy = this.jumpSpeed; if (this.collidesWithPlatform()) { this.falling = false; this.standing = true; this.jumping = false; this.jumpSpeed = 0; this.dy = this.jumpSpeed; } } } So, the problem is, that this function updates the dy regardless of the diff, making the characters fly like Superman in slow machines, and I have no idea how to implement the diff factor so that when a character is jumping, his speed decrement in a proportional way to the game speed. Can anyone help me fix this issue? or give me pointers on how to make a 2D Jump in J2ME the right way. Thank you very much for your time.

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• The correct usage of nested #pragma omp for directives

  - by GoldenLee

  The following code runs like a charm before OpenMP parallelization was applied. In fact, the following code was in a state of endless loop! I'm sure that's result from my incorrect use to the OpenMP directives. Would you please show me the correct way? Thank you very much. #pragma omp parallel for for (int nY = nYTop; nY <= nYBottom; nY++) { for (int nX = nXLeft; nX <= nXRight; nX++) { // Use look-up table for performance dLon = theApp.m_LonLatLUT.LonGrid()[nY][nX] + m_FavoriteSVISSRParams.m_dNadirLon; dLat = theApp.m_LonLatLUT.LatGrid()[nY][nX]; // If you don't want to use longitude/latitude look-up table, uncomment the following line //NOMGeoLocate.XYToGEO(dLon, dLat, nX, nY); if (dLon > 180 || dLat > 180) { continue; } if (Navigation.GeoToXY(dX, dY, dLon, dLat, 0) > 0) { continue; } // Skip void data scanline dY = dY - nScanlineOffset; // Compute coefficients as well as its four neighboring points' values nX1 = int(dX); nX2 = nX1 + 1; nY1 = int(dY); nY2 = nY1 + 1; dCx = dX - nX1; dCy = dY - nY1; dP1 = pIRChannelData->operator [](nY1)[nX1]; dP2 = pIRChannelData->operator [](nY1)[nX2]; dP3 = pIRChannelData->operator [](nY2)[nX1]; dP4 = pIRChannelData->operator [](nY2)[nX2]; // Bilinear interpolation usNomDataBlock[nY][nX] = (unsigned short)BilinearInterpolation(dCx, dCy, dP1, dP2, dP3, dP4); } }

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• How to make a pause before continuing method

  - by user1766728

  Now, I know that this has been asked, but I need to know how to do this NOT on html or anything. Heres my code, not including all of the other java files. package rtype; import java.awt.Image; import java.awt.event.KeyEvent; import java.util.ArrayList; import javax.swing.ImageIcon; public class aa { private int xd; private int yd; private int dx; private int dy; private int x; private int y; private Image image; private ArrayList missiles; private final int CRAFT_SIZE = 70; public aa() { ImageIcon ii = new ImageIcon(this.getClass().getResource("/aa.png")); image = ii.getImage(); missiles = new ArrayList(); x = 10; y = 10; xd = -14; yd = 140; } public void move() { if(y >=xd) y += dx; else if(y < xd) y += 1; if(y <=yd) y += dy; else if(y > yd) y += -1; } public int getX() { return x; } public int getY() { return y; } public Image getImage() { return image; } public ArrayList getMissiles() { return missiles; } public void keyPressed(KeyEvent e) { int key = e.getKeyCode(); if (key == KeyEvent.VK_SPACE) { fire(); } if (key == KeyEvent.VK_UP) { dy = -1; } if (key == KeyEvent.VK_DOWN) { dy = 1; } if (key == KeyEvent.VK_RIGHT) { yd++; } if (key == KeyEvent.VK_LEFT) { yd--; } if (key == KeyEvent.VK_W) { xd++; } if (key == KeyEvent.VK_S) { xd--; } } public void fire() { try{ missiles.add(new Missle(x + CRAFT_SIZE, y + CRAFT_SIZE)); }catch(Exception e){} } public void keyReleased(KeyEvent e) { int key = e.getKeyCode(); if (key == KeyEvent.VK_UP) { dy = 0; } if (key == KeyEvent.VK_DOWN) { dy = 0; } } } So, at the method, fire(), I want to make it delay between shots. HOW? sorry if this is n00bish

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• Silverlight Cream for November 26, 2011 -- #1175

  - by Dave Campbell

  In this Issue: Michael Washington, Manas Patnaik, Jeff Blankenburg, Doug Mair, Jon Galloway, Richard Bartholomew, Peter Bromberg, Joel Reyes, Zeben Chen, Navneet Gupta, and Cathy Sullivan. Above the Fold: Silverlight: "Using ASP.NET PageMethods With Silverlight" Peter Bromberg WP7: "Leveraging Background Services and Agents in Windows Phone 7 (Mango)" Jon Galloway Metro/WinRT/Windows8: "Debugging Contracts using Windows Simulator" Cathy Sullivan LightSwitch: "LightSwitch: It Is About The Money (It Is Always About The Money)" Michael Washington Shoutouts: Michael Palermo's latest Desert Mountain Developers is up Michael Washington's latest Visual Studio #LightSwitch Daily is up From SilverlightCream.com:LightSwitch: It Is About The Money (It Is Always About The Money)Michael Washington has a very nice post up about LightSwitch apps in general and his opinion about the future use... based on what he and I have been up to, I tend to agree on all counts!Accessing Controls from DataGrid ColumnHeader – SilverlightManas Patnaik's latest post is about using the VisualTreeHelper class to iterate through the visual tree to find the controls you need ... including sample code31 Days of Mango | Day #18: Using Sample DataJeff Blankenburg's Day 18 in his 31-Day Mango quest is on Sample Data using Expression Blend, and he begins with great links to his other Blend posts followed by a nice sample data tutorial and source31 Days of Mango | Day #19: Tilt EffectsDoug Mair returns to the reigns of Jeff's 31-Days series with number 19 which is all about Tilt Effects ... as seen in the Phone application when you select a user... Doug shows how to add this effect to your appLeveraging Background Services and Agents in Windows Phone 7 (Mango)Jon Galloway has a WP7 post up discussing Background Services and how they all fit together... he's got a great diagram of that as an overview then really nice discussion of each followed up by his slides from DevConnections, and codeNetflix on Windows 8This one isn't C#/XAML, but Richard Bartholomew has a Netflix on Windows 8 app running that bears noticeUsing ASP.NET PageMethods With SilverlightPeter Bromberg has a post up demonstrating calling PageMethods from a Silverlight app using the ScriptManager controlAWESOME Windows Phone Power ToolJoel Reyes announced the release of a full-featured tool for side-loading apps to your WP7 device... available at codeplexMicrosoft Windows Simulator Rotation and Resolution EmulationZeben Chen discusses the Windows 8 Simulator a bit deeper with this code-laden post showing how to look at roation and orientation-aware apps and resolution.First look at Windows SimulatorNavneet Gupta has a great into post to using the simulator in VS2011 for Windows 8 apps. Four things you really need this for: Touch Emulation, Rotation, Different target resolutions, and ContractsDebugging Contracts using Windows SimulatorCathy Sullivan shows how to debug W8 Contracts in VS2011... why you ask? because when you hit one in the debugger, the target app disappears.. but enter the simulator... check it outStay in the 'Light!Twitter SilverlightNews | Twitter WynApse | WynApse.com | Tagged Posts | SilverlightCreamJoin me @ SilverlightCream | Phoenix Silverlight User GroupTechnorati Tags:Silverlight    Silverlight 3    Silverlight 4    Windows PhoneMIX10

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• Silverlight Cream for November 22, 2011 -- #1172

  - by Dave Campbell

  In this Issue: XAMLGeek, WindowsPhoneGeek, Nigel Sampson, Jesse Liberty, Sumit Dutta(-2-), Dave Bost, Jared Bienz, Joost van Schaik, and Michael Crump. Above the Fold: Silverlight: "10 Laps around Silverlight 5 (Part 7 of 10)" Michael Crump WP7: "Using MVVMLight, ItemsControl, Blend and behaviors to make a ‘heads up compass’" Joost van Schaik Metro/WinRT/W8: "“Badevand” for Windows 8" XAMLGeek Shoutouts: Michael Palermo's latest Desert Mountain Developers is up Michael Washington's latest Visual Studio #LightSwitch Daily is up From SilverlightCream.com:“Badevand” for Windows 8XAMLGeek posted a Metro app that shows water and air temperature and rain level for 5 beaches in Copenhagen, Denmark... no source, but good to see people posting appsGetting Started with Windows Phone RemindersWindowsPhoneGeek digs into Reminders in this WP7.1 post... the code you need, description, and a project to downloadHelp my app has been revoked!Nigel Sampson had a surprise when his latest app was revoked on his device, and then another... read what the solution wasA Dozen Windows Phone Videos… And CountingJesse Liberty posted his 12th WP7.1 video on Channel 9 - all about Reminders in MangoPart 23 - Windows Phone 7 - Detect Operator and Network InformationSumit Dutta has 2 more parts to his WP7 quest up... this part 23 is about getting mobile operator information and hot to get network capabilities using Microsoft.Phone.Net.DeviceNetworkInformationPart 24 - Windows Phone 7 - Microphone RepeaterIn part 24, Sumit Dutta uses the Microsoft.Xna.Framework Microphone class to record and play back voice.31 Days of Mango | Day #13: Marketplace Test KitDave Bost is at the helm of Jeff Blankenburg's Day 13 in his 31 day quest, discussing the Marketplace Test Kit and showing how to use it to determine if your app is ready for certification31 Days of Mango | Day #12; Beta DistributionJeff Blankenburg's Day 12 is written by guest author Jared Bienz, and shows how to submit an application for Beta testingUsing MVVMLight, ItemsControl, Blend and behaviors to make a ‘heads up compass’Joost van Schaik has a tutorial up showing how to make a WP7 Compass app using MVVMLight, Expression Blend, and then shows his thoughts on using the ItemsControl and Behaviors... code, descriptions and a project to download.... and I think I got your name right for the first time, Joost :)10 Laps around Silverlight 5 (Part 7 of 10)Michael Crump put out part 7 of his Silverlight 5 series at SilverlightShow... this is actually part 2 of OS Integration with Silverlight covering, among other things, 64-bit browser support and Power AwarenessStay in the 'Light!Twitter SilverlightNews | Twitter WynApse | WynApse.com | Tagged Posts | SilverlightCreamJoin me @ SilverlightCream | Phoenix Silverlight User GroupTechnorati Tags:Silverlight    Silverlight 3    Silverlight 4    Windows PhoneMIX10

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• How to implement a SIMPLE "You typed ACB, did you mean ABC?"

  - by marcgg

  I know this is not a straight up question, so if you need me to provide more information about the scope of it, let me know. There are a bunch of questions that address almost the same issue (they are linked here), but never the exact same one with the same kind of scope and objective - at least as far as I know. Context: I have a MP3 file with ID3 tags for artist name and song title. I have two tables Artists and Songs The ID3 tags might be slightly off (e.g. Mikaell Jacksonne) I'm using ASP.NET + C# and a MSSQL database I need to synchronize the MP3s with the database. Meaning: The user launches a script The script browses through all the MP3s The script says "Is 'Mikaell Jacksonne' 'Michael Jackson' YES/NO" The user pick and we start over Examples of what the system could find: In the database... SONGS = {"This is a great song title", "This is a song title"} ARTISTS = {"Michael Jackson"} Outputs... "This is a grt song title" did you mean "This is a great song title" ? "This is song title" did you mean "This is a song title" ? "This si a song title" did you mean "This is a song title" ? "This si song a title" did you mean "This is a song title" ? "Jackson, Michael" did you mean "Michael Jackson" ? "JacksonMichael" did you mean "Michael Jackson" ? "Michael Jacksno" did you mean "Michael Jackson" ? etc. I read some documentation from this /how-do-you-implement-a-did-you-mean and this is not exactly what I need since I don't want to check an entire dictionary. I also can't really use a web service since it's depending a lot on what I already have in my database. If possible I'd also like to avoid dealing with distances and other complicated things. I could use the google api (or something similar) to do this, meaning that the script will try spell checking and test it with the database, but I feel there could be a better solution since my database might end up being really specific with weird songs and artists, making spell checking useless. I could also try something like what has been explained on this post, using Soundex for c#. Using a regular spell checker won't work because I won't be using words but names and 'titles'. So my question is: is there a relatively simple way of doing this, and if so, what is it? Any kind of help would be appreciated. Thanks!

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• Remove words enclosed in parenthesis

  - by Maverick50

  How do I remove words enclosed in parenthesis in Word 2007 Example: From this: Michael Winkelman (Ben), Steven Benson (Joey), To This: Michael Winkelman, Steven Benson,

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• Explaining the difference between OData & RDF by way of analogy

  - by jamiet

  A couple of months back I wrote a blog post entitled Microsoft, OData and RDF where I gave a high level view of the OData protocol and how it compares to RDF. I talked about linked data, triples and such like which may have been somewhat useful however jargon-heavy. Earlier today Dr Michael Hausenblas (blog | twitter) offered an analogy which I think is probably more useful and with Michael's permission I'm re-posting it here:Imagine a Web (a Web of Documents, if you wish), which is not based on HTML and hyperlinks, but on MS Word documents. The documents are all available on the Internet, so you can download them and consume the content. But after you’re done with a certain document that talks about a book, how do you learn more about it? For example, reviews about the book or where you can purchase it? Maybe the original document mentions that there is some more related information on another server. So you’d need to go there and look for the related bit of information yourself. You see? That’s what the Web is great at – you just click on a hyperlink and it takes you to the document (or section) you’re interested in. All the legwork is taken care of for you through HTML, URIs and HTTP.Hm, right, but how is this related to OData? Well, OData feels a bit like the above mentioned scenario, just concerning data. Of course you – well actually rather a software program I guess – can consume it (a single source), but that’s it.from Oh – it is data on the Web by Michael Hausenblas I believe that OData has loads of use cases but its important to understand its limitations as well and I think Michael has done a good job of explaining those limitations.@Jamiet   Share this post: email it! | bookmark it! | digg it! | reddit! | kick it! | live it!

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• Android, how important is deltaTime?

  - by iQue

  Im making a game that is getting pretty big and sometimes my thread has to skip a frame, so far I'm not using deltaTime for setting the speed of my different objects in the game because it's still not a big enough game for it to matter imo. But its getting bigger then I planned, so my question is, how important is delta Time? If I should use delta time there is a problem, since speedX and speedY are integers(they have to be for eclipse to let you make a rectangle of them), I cant add delta time very functionally as far as I understand, but might be wrong? Ive tried adding deltaTime to the code below, and sometimes my enemies just not move after spawn, they just stand there and run in the same place Will add an some code for how I set / use speed: public void update(int dx, int dy) { double theta = 180.0 / Math.PI * Math.atan2(-(y - controls.pointerPosition.y), controls.pointerPosition.x - x); x +=dx * Math.cos(Math.toRadians(theta)); y +=dy * Math.sin(Math.toRadians(theta)); currentFrame = ++currentFrame % BMP_COLUMNS; } public void draw(Canvas canvas) { int srcX = currentFrame * width; int srcY = 1 * height; Rect src = new Rect(srcX, srcY, srcX + width, srcY + height); Rect dst = new Rect(x, y, x + width, y + height); canvas.drawBitmap(bitmap, src, dst, null); } So if someone with some experience with this has any thoughts, please share. Thank you! Changed code: public void update(int dx, int dy, float delta) { double theta = 180.0 / Math.PI * Math.atan2(-(y - controls.pointerPosition.y), controls.pointerPosition.x - x); double speedX = delta * dx * Math.cos(Math.toRadians(theta)); double speedY = delta * dy * Math.sin(Math.toRadians(theta)); x += speedX; y += speedY; currentFrame = ++currentFrame % BMP_COLUMNS; } public void draw(Canvas canvas) { int srcX = currentFrame * width; int srcY = 1 * height; Rect src = new Rect(srcX, srcY, srcX + width, srcY + height); Rect dst = new Rect(x, y, x + width, y + height); canvas.drawBitmap(bitmap, src, dst, null); } with this code my enemies move like before, except they wont move to the right (wont increment x), all other directions work.

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• Building a Flash Platformer

  - by Jonathan O

  I am basically making a game where the whole game is run in the onEnterFrame method. This is causing a delay in my code that makes debugging and testing difficult. Should programming an entire platformer in this method be efficient enough for me to run hundreds of lines of code? Also, do variables in flash get updated immediately? Are there just lots of threads listening at the same time? Here is the code... stage.addEventListener(Event.ENTER_FRAME, onEnter); function onEnter(e:Event):void { //Jumping if (Yoshi.y > groundBaseLevel) { dy = 0; canJump = true; onGround = true; //This line is not updated in time } if (Key.isDown(Key.UP) && canJump) { dy = -10; canJump = false; onGround = false; //This line is not updated in time } if(!onGround) { dy += gravity; Yoshi.y += dy; } //limit screen boundaries //character movement if (! Yoshi.hitTestObject(Platform)) //no collision detected { if (Key.isDown(Key.RIGHT)) { speed += 4; speed *= friction; Yoshi.x = Yoshi.x + movementIncrement + speed; Yoshi.scaleX = 1; Yoshi.gotoAndStop('Walking'); } else if (Key.isDown(Key.LEFT)) { speed -= 4; speed *= friction; Yoshi.x = Yoshi.x - movementIncrement + speed; Yoshi.scaleX = -1; Yoshi.gotoAndStop('Walking'); } else { speed *= friction; Yoshi.x = Yoshi.x + speed; Yoshi.gotoAndStop('Still'); } } else //bounce back collision detected { if(Yoshi.hitTestPoint(Platform.x - Platform.width/2, Platform.y - Platform.height/2, false)) { trace('collision left'); Yoshi.x -=20; } if(Yoshi.hitTestPoint(Platform.x, Platform.y - Platform.height/2, false)) { trace('collision top'); onGround=true; //This update is not happening in time speed = 0; } } }

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• Game works on netbeans but not outside netbeans in jar file?

  - by Michael Haywood

  I am creating a basic game of 'Pong'. I have finished the game apart from a few glitches I need to remove. The game runs perfectly in netbeans but if I create a jar file errors come up causing it to not work. I am quite new to java but I believe it is something to do with my code looking for the images but the images have not been loaded up yet. Here is the error. How can I get this to work outside of netbeans in a jar file? C:\Users\michael>java -jar "C:\Users\michael\Documents\NetBeansProjects\Pong\dis t\Pong.jar" Exception in thread "main" java.lang.NullPointerException at javax.swing.ImageIcon.<init>(Unknown Source) at pong.BallMainMenu.<init>(BallMainMenu.java:19) at pong.Board.gameInit(Board.java:93) at pong.Board.addNotify(Board.java:86) at java.awt.Container.addNotify(Unknown Source) at javax.swing.JComponent.addNotify(Unknown Source) at java.awt.Container.addNotify(Unknown Source) at javax.swing.JComponent.addNotify(Unknown Source) at java.awt.Container.addNotify(Unknown Source) at javax.swing.JComponent.addNotify(Unknown Source) at javax.swing.JRootPane.addNotify(Unknown Source) at java.awt.Container.addNotify(Unknown Source) at java.awt.Window.addNotify(Unknown Source) at java.awt.Frame.addNotify(Unknown Source) at java.awt.Window.show(Unknown Source) at java.awt.Component.show(Unknown Source) at java.awt.Component.setVisible(Unknown Source) at java.awt.Window.setVisible(Unknown Source) at pong.Pong.<init>(Pong.java:16) at pong.Pong.main(Pong.java:23)

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• ArchBeat Link-o-Rama for 2012-06-01

  - by Bob Rhubart

  Complexity of Social Computing - Is it a Consideration for EA's? | Pat Shepherd blogs.oracle.com Pat Shepherd asks, "Does Enterprise Architecture need to consider Social Computing in its scope?" Who should own the Enterprise Architecture? | Michael Glas blogs.oracle.com "Instead of looking at just who owns the architecture," suggests Michael Glas, "think about what the person/role/organization should do." The Application Architecture Domain | Michael Glas blogs.oracle.com Michael Glas asks—and answers: "As an Enterprise Architect, what do I need to consider when looking at/defining/designing the Application Architecture Domain?" CAP Twelve Years Later: How the "Rules" Have Changed | Eric Brewer www.infoq.com The CAP theorem asserts that any net­worked shared-data system can have only two of three desirable properties. How­ever, by explicitly handling partitions, designers can optimize consistency and availability, thereby achieving some trade-off of all three. Oracle DB with OEM in Amazon Cloud | Dr. Frank Munz www.munzandmore.com Dr. Frank Munz shares a video that screencast that explains "how to create an Oracle DB instance in AWS, how to enable OEM...and how to connect to your cloud instance with a local installation of NetBeans." Sample External Login.jsp page for Oracle Access Manager 11g | Brian Eidelman fusionsecurity.blogspot.com A-Team blogger Brian Eidelman expands on a previous post dealing with configuring OAM 11g to use an externally hosted custom login page. Bay Area Coherence Special Interest Group (BACSIG) Meeting June 7 coherence.oracle.com Date: Thursday, June 7, 2012 Time: 5:30pm – 9:00pm PT Where: Oracle Conference Center Room # 103 350 Oracle Parkway Redwood, Shores, CA Presentations: 6:00 p.m. - Coherence 101, The Evolution of Distributed Caching - Noah Arliss (Oracle) 7:00 p.m. - Optimizing Performance for Oracle Coherence and TopLink Grid at OOCL - Matt Rosen, Leo Limqueco (OOCL) 8:00 p.m. - Oracle Coherence Message Bus - Extreme Performance on Oracle Exalogic - Ballav Bihani (Oracle) Thought for the Day "I can't be left unsupervised." — Ron Wood (Born 06/01/1947 Source: Brainy Quote

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• rotate sprite and shooting bullets from the end of a cannon

  - by Alberto

  Hi all i have a problem in my Andengine code, I need , when I touch the screen, shoot a bullet from the cannon (in the same direction of the cannon) The cannon rotates perfectly but when I touch the screen the bullet is not created at the end of the turret This is my code: private void shootProjectile(final float pX, final float pY){ int offX = (int) (pX-canon.getSceneCenterCoordinates()[0]); int offY = (int) (pY-canon.getSceneCenterCoordinates()[1]); if (offX <= 0) return ; if(offY>=0) return; double X=canon.getX()+canon.getWidth()*0,5; double Y=canon.getY()+canon.getHeight()*0,5 ; final Sprite projectile; projectile = new Sprite( (float) X, (float) Y, mProjectileTextureRegion,this.getVertexBufferObjectManager() ); mMainScene.attachChild(projectile); int realX = (int) (mCamera.getWidth()+ projectile.getWidth()/2.0f); float ratio = (float) offY / (float) offX; int realY = (int) ((realX*ratio) + projectile.getY()); int offRealX = (int) (realX- projectile.getX()); int offRealY = (int) (realY- projectile.getY()); float length = (float) Math.sqrt((offRealX*offRealX)+(offRealY*offRealY)); float velocity = (float) 480.0f/1.0f; float realMoveDuration = length/velocity; MoveModifier modifier = new MoveModifier(realMoveDuration,projectile.getX(), realX, projectile.getY(), realY); projectile.registerEntityModifier(modifier); } @Override public boolean onSceneTouchEvent(Scene pScene, TouchEvent pSceneTouchEvent) { if (pSceneTouchEvent.getAction() == TouchEvent.ACTION_MOVE){ double dx = pSceneTouchEvent.getX() - canon.getSceneCenterCoordinates()[0]; double dy = pSceneTouchEvent.getY() - canon.getSceneCenterCoordinates()[1]; double Radius = Math.atan2(dy,dx); double Angle = Radius * 180 / Math.PI; canon.setRotation((float)Angle); return true; } else if (pSceneTouchEvent.getAction() == TouchEvent.ACTION_DOWN){ final float touchX = pSceneTouchEvent.getX(); final float touchY = pSceneTouchEvent.getY(); double dx = pSceneTouchEvent.getX() - canon.getSceneCenterCoordinates()[0]; double dy = pSceneTouchEvent.getY() - canon.getSceneCenterCoordinates()[1]; double Radius = Math.atan2(dy,dx); double Angle = Radius * 180 / Math.PI; canon.setRotation((float)Angle); shootProjectile(touchX, touchY); } return false; } Anyone know how to calculate the coordinates (X,Y) of the end of the barrel to draw the bullet?

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• box2d resize bodies arround point

  - by philipp

  I have a compound object, consisting of a b2Body, vector-graphics and a list polygons which describe the b2body's shapes. This object has its own transformation matrix to centralize the storage of transformations. So far everything is working quiet fine, even scaling works, but not if i scale around a point. In the initialization phase of the object it is scaled around a point. This happens in this order: transform the main matrix transform the vector graphics and the polygons recreate the b2Body After this function ran, the shapes and all the graphics are exactly where they should be, BUT: after the first steps of the b2World the graphical stuff moves away from the body. When I ran the debugger I found out that the position of the body is 0/0 the red dot shows the center of scaling. the first image shows the basic setup and the second the final position of the graphics. This distance stays constant for the rest of the simulation. If I set the position via myBody.SetPosition( sx, sy ); the whole scenario just plays a bit more distant for the origin. Any Idea how to fix this? EDIT:: I came deeper down to the problem and it lies in the fact that i must not scale the transform matrix for the b2body shapes around the center, but set the b2body's position back to the point after scaling. But how can I calculate that point? EDIT 2 :: I came ever deeper down to it, even solved it, but this is a slow solution and i hope that there is somebody who understands what formula I need. assuming to have a set polygons relative to an origin as basis shapes for a b2body: scaling the whole object around a certain point is done in the following steps: i scale everything around the center except the polygons i create a clone of the polygons matrix i scale this clone around the point i calculate dx, dy as difference of clone.tx - original.tx and clone.ty - original.ty i scale the original polygon matrix NOT around the point i recreate the body i create the fixture i set the position of the body to dx and dy done! So what i an interested in is a formula for dx and dy without cloning matrices, scaling the clone around a point, getting dx and dy and finally scale the vertex matrix.

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• 2D Collision in Canvas - Balls Overlapping When Velocity is High

  - by kushsolitary

  I am doing a simple experiment in canvas using Javascript in which some balls will be thrown on the screen with some initial velocity and then they will bounce on colliding with each other or with the walls. I managed to do the collision with walls perfectly but now the problem is with the collision with other balls. I am using the following code for it: //Check collision between two bodies function collides(b1, b2) { //Find the distance between their mid-points var dx = b1.x - b2.x, dy = b1.y - b2.y, dist = Math.round(Math.sqrt(dx*dx + dy*dy)); //Check if it is a collision if(dist <= (b1.r + b2.r)) { //Calculate the angles var angle = Math.atan2(dy, dx), sin = Math.sin(angle), cos = Math.cos(angle); //Calculate the old velocity components var v1x = b1.vx * cos, v2x = b2.vx * cos, v1y = b1.vy * sin, v2y = b2.vy * sin; //Calculate the new velocity components var vel1x = ((b1.m - b2.m) / (b1.m + b2.m)) * v1x + (2 * b2.m / (b1.m + b2.m)) * v2x, vel2x = (2 * b1.m / (b1.m + b2.m)) * v1x + ((b2.m - b1.m) / (b2.m + b1.m)) * v2x, vel1y = v1y, vel2y = v2y; //Set the new velocities b1.vx = vel1x; b2.vx = vel2x; b1.vy = vel1y; b2.vy = vel2y; } } You can see the experiment here. The problem is, some balls overlap each other and stick together while some of them rebound perfectly. I don't know what is causing this issue. Here's my balls object if that matters: function Ball() { //Random Positions this.x = 50 + Math.random() * W; this.y = 50 + Math.random() * H; //Random radii this.r = 15 + Math.random() * 30; this.m = this.r; //Random velocity components this.vx = 1 + Math.random() * 4; this.vy = 1 + Math.random() * 4; //Random shade of grey color this.c = Math.round(Math.random() * 200); this.draw = function() { ctx.beginPath(); ctx.fillStyle = "rgb(" + this.c + ", " + this.c + ", " + this.c + ")"; ctx.arc(this.x, this.y, this.r, 0, Math.PI*2, false); ctx.fill(); ctx.closePath(); } }

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