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  • Evaluating mean and std as simulations are added

    - by Luca Cerone
    I have simulations that evaluate a certain value X. I run the simulations several times and save the value of X in a vector V. When all the runs have finished I evaluate the mean and standard deviation for the vector V. This approach works, but implies saving all the values for X. As my computer is quite old and with limited ram, I was wondering if there is a way to update the mean value M and the standard deviation S, knowing the value of X at the (n+1)-th run, and the values of M and S after n runs. How can I update the mean value and the standard deviation as simulations are added to the set? Please note that this is just a conceptual example, I don't save only one number X but thousands at each simulations, so I really have problems running a big number of runs if I have to keep all the past values into the memory.

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  • add collision detection to sprite?

    - by xBroak
    bassically im trying to add collision detection to the sprite below, using the following: self.rect = bounds_rect collide = pygame.sprite.spritecollide(self, wall_list, False) if collide: # yes print("collide") However it seems that when the collide is triggered it continuously prints 'collide' over and over when instead i want them to simply not be able to walk through the object, any help? def update(self, time_passed): """ Update the creep. time_passed: The time passed (in ms) since the previous update. """ if self.state == Creep.ALIVE: # Maybe it's time to change the direction ? # self._change_direction(time_passed) # Make the creep point in the correct direction. # Since our direction vector is in screen coordinates # (i.e. right bottom is 1, 1), and rotate() rotates # counter-clockwise, the angle must be inverted to # work correctly. # self.image = pygame.transform.rotate( self.base_image, -self.direction.angle) # Compute and apply the displacement to the position # vector. The displacement is a vector, having the angle # of self.direction (which is normalized to not affect # the magnitude of the displacement) # displacement = vec2d( self.direction.x * self.speed * time_passed, self.direction.y * self.speed * time_passed) self.pos += displacement # When the image is rotated, its size is changed. # We must take the size into account for detecting # collisions with the walls. # self.image_w, self.image_h = self.image.get_size() global bounds_rect bounds_rect = self.field.inflate( -self.image_w, -self.image_h) if self.pos.x < bounds_rect.left: self.pos.x = bounds_rect.left self.direction.x *= -1 elif self.pos.x > bounds_rect.right: self.pos.x = bounds_rect.right self.direction.x *= -1 elif self.pos.y < bounds_rect.top: self.pos.y = bounds_rect.top self.direction.y *= -1 elif self.pos.y > bounds_rect.bottom: self.pos.y = bounds_rect.bottom self.direction.y *= -1 self.rect = bounds_rect collide = pygame.sprite.spritecollide(self, wall_list, False) if collide: # yes print("collide") elif self.state == Creep.EXPLODING: if self.explode_animation.active: self.explode_animation.update(time_passed) else: self.state = Creep.DEAD self.kill() elif self.state == Creep.DEAD: pass #------------------ PRIVATE PARTS ------------------# # States the creep can be in. # # ALIVE: The creep is roaming around the screen # EXPLODING: # The creep is now exploding, just a moment before dying. # DEAD: The creep is dead and inactive # (ALIVE, EXPLODING, DEAD) = range(3) _counter = 0 def _change_direction(self, time_passed): """ Turn by 45 degrees in a random direction once per 0.4 to 0.5 seconds. """ self._counter += time_passed if self._counter > randint(400, 500): self.direction.rotate(45 * randint(-1, 1)) self._counter = 0 def _point_is_inside(self, point): """ Is the point (given as a vec2d) inside our creep's body? """ img_point = point - vec2d( int(self.pos.x - self.image_w / 2), int(self.pos.y - self.image_h / 2)) try: pix = self.image.get_at(img_point) return pix[3] > 0 except IndexError: return False def _decrease_health(self, n): """ Decrease my health by n (or to 0, if it's currently less than n) """ self.health = max(0, self.health - n) if self.health == 0: self._explode() def _explode(self): """ Starts the explosion animation that ends the Creep's life. """ self.state = Creep.EXPLODING pos = ( self.pos.x - self.explosion_images[0].get_width() / 2, self.pos.y - self.explosion_images[0].get_height() / 2) self.explode_animation = SimpleAnimation( self.screen, pos, self.explosion_images, 100, 300) global remainingCreeps remainingCreeps-=1 if remainingCreeps == 0: print("all dead")

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  • Reusable skill class structure

    - by Martino Wullems
    Hello, Pretty new to the whole game development scene, but I have experience in other branches of programming. Anyway, I was wondering what methods are used to implement a skill structure. I imagine a skill in itself would a class. I'm using actionscript 3 for this project btw. public class Skill { public var power:int; public var delay:int; public var cooldown:int; public function Attack(user:Mob, target:Mob) { } } } Each skill would extend the Skill class and add it's own functionality. public class Tackle extends Skill { public function Tackle(user:Mob, target:Mob) { super(user, target); executeAttack(); } private function executeAttack():void { //multiply user.strength with power etc //play attack animation } } } This where I get stuck. How do I termine which mobs has which skills? And which skill will they later be able to retrieve (by reaching a certain level etc). How does the player actually execute the skill and how is it determine if it hits. It's all very new to me so I have no idea where to begin. Any links would also be appreciated. Thanks in advance.

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  • Trying to detect collision between two polygons using Separating Axis Theorem

    - by Holly
    The only collision experience i've had was with simple rectangles, i wanted to find something that would allow me to define polygonal areas for collision and have been trying to make sense of SAT using these two links Though i'm a bit iffy with the math for the most part i feel like i understand the theory! Except my implementation somewhere down the line must be off as: (excuse the hideous font) As mentioned above i have defined a CollisionPolygon class where most of my theory is implemented and then have a helper class called Vect which was meant to be for Vectors but has also been used to contain a vertex given that both just have two float values. I've tried stepping through the function and inspecting the values to solve things but given so many axes and vectors and new math to work out as i go i'm struggling to find the erroneous calculation(s) and would really appreciate any help. Apologies if this is not suitable as a question! CollisionPolygon.java: package biz.hireholly.gameplay; import android.graphics.Canvas; import android.graphics.Color; import android.graphics.Paint; import biz.hireholly.gameplay.Types.Vect; public class CollisionPolygon { Paint paint; private Vect[] vertices; private Vect[] separationAxes; CollisionPolygon(Vect[] vertices){ this.vertices = vertices; //compute edges and separations axes separationAxes = new Vect[vertices.length]; for (int i = 0; i < vertices.length; i++) { // get the current vertex Vect p1 = vertices[i]; // get the next vertex Vect p2 = vertices[i + 1 == vertices.length ? 0 : i + 1]; // subtract the two to get the edge vector Vect edge = p1.subtract(p2); // get either perpendicular vector Vect normal = edge.perp(); // the perp method is just (x, y) => (-y, x) or (y, -x) separationAxes[i] = normal; } paint = new Paint(); paint.setColor(Color.RED); } public void draw(Canvas c, int xPos, int yPos){ for (int i = 0; i < vertices.length; i++) { Vect v1 = vertices[i]; Vect v2 = vertices[i + 1 == vertices.length ? 0 : i + 1]; c.drawLine( xPos + v1.x, yPos + v1.y, xPos + v2.x, yPos + v2.y, paint); } } /* consider changing to a static function */ public boolean intersects(CollisionPolygon p){ // loop over this polygons separation exes for (Vect axis : separationAxes) { // project both shapes onto the axis Vect p1 = this.minMaxProjection(axis); Vect p2 = p.minMaxProjection(axis); // do the projections overlap? if (!p1.overlap(p2)) { // then we can guarantee that the shapes do not overlap return false; } } // loop over the other polygons separation axes Vect[] sepAxesOther = p.getSeparationAxes(); for (Vect axis : sepAxesOther) { // project both shapes onto the axis Vect p1 = this.minMaxProjection(axis); Vect p2 = p.minMaxProjection(axis); // do the projections overlap? if (!p1.overlap(p2)) { // then we can guarantee that the shapes do not overlap return false; } } // if we get here then we know that every axis had overlap on it // so we can guarantee an intersection return true; } /* Note projections wont actually be acurate if the axes aren't normalised * but that's not necessary since we just need a boolean return from our * intersects not a Minimum Translation Vector. */ private Vect minMaxProjection(Vect axis) { float min = axis.dot(vertices[0]); float max = min; for (int i = 1; i < vertices.length; i++) { float p = axis.dot(vertices[i]); if (p < min) { min = p; } else if (p > max) { max = p; } } Vect minMaxProj = new Vect(min, max); return minMaxProj; } public Vect[] getSeparationAxes() { return separationAxes; } public Vect[] getVertices() { return vertices; } } Vect.java: package biz.hireholly.gameplay.Types; /* NOTE: Can also be used to hold vertices! Projections, coordinates ect */ public class Vect{ public float x; public float y; public Vect(float x, float y){ this.x = x; this.y = y; } public Vect perp() { return new Vect(-y, x); } public Vect subtract(Vect other) { return new Vect(x - other.x, y - other.y); } public boolean overlap(Vect other) { if( other.x <= y || other.y >= x){ return true; } return false; } /* used specifically for my SAT implementation which i'm figuring out as i go, * references for later.. * http://www.gamedev.net/page/resources/_/technical/game-programming/2d-rotated-rectangle-collision-r2604 * http://www.codezealot.org/archives/55 */ public float scalarDotProjection(Vect other) { //multiplier = dot product / length^2 float multiplier = dot(other) / (x*x + y*y); //to get the x/y of the projection vector multiply by x/y of axis float projX = multiplier * x; float projY = multiplier * y; //we want to return the dot product of the projection, it's meaningless but useful in our SAT case return dot(new Vect(projX,projY)); } public float dot(Vect other){ return (other.x*x + other.y*y); } }

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  • Alternatives to NSMutableArray for storing 2D grid - iOS Cocos2d

    - by SundayMonday
    I'm creating a grid-based iOS game using Cocos2d. Currently the grid is stored in an NSMutableArray that contains other NSMutableArrays (the latter are rows in the grid). This works ok and performance so far is pretty good. However the syntax feels bulky and the indexing isn't very elegant (using CGPoints, would prefer integer indices). I'm looking for an alternative. What are some alternatives data structures for 2D arrays in this situation? In my game it's very common to add and remove rows from the bottom of the grid. So the grid might start off 10x10, grow to 17x10, shrink to 8x10 and then finally end with 2x10. Note the column count is constant. I've consider using a vector<vector<Object*>>. Also I'm vaguely aware of some type of "fast array" or similar offered by Cocos2d. I'd just like to learn about best practices from other developers!

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  • Understanding how texCUBE works and writing cubemaps properly into a cube rendertarget

    - by cubrman
    My goal is to create accurate reflections, sampled from a dynamic cubemap, for specific 3d objects (mostly lights) in XNA 4.0. To sample the cubemap I compute the 3d reflection vector in a classic way: half3 ReflectionVec = reflect(-directionToCamera, Normal.rgb); I then use the vector to get the actual reflected color: half3 ReflectionCol = texCUBElod(ReflectionSampler, float4(ReflectionVec, 0)); The cubemap I am sampling from is a RenderTarget with 6 flat faces. So my question is, given the 3d world position of an arbitrary 3d object, how can I make sure that I get accurate reflections of this object, when I re-render the cubemap. Should I build the ViewProjection matrix in a specific way? Or is there any other approach?

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  • Error in my Separating Axis Theorem collision code

    - by Holly
    The only collision experience i've had was with simple rectangles, i wanted to find something that would allow me to define polygonal areas for collision and have been trying to make sense of SAT using these two links Though i'm a bit iffy with the math for the most part i feel like i understand the theory! Except my implementation somewhere down the line must be off as: (excuse the hideous font) As mentioned above i have defined a CollisionPolygon class where most of my theory is implemented and then have a helper class called Vect which was meant to be for Vectors but has also been used to contain a vertex given that both just have two float values. I've tried stepping through the function and inspecting the values to solve things but given so many axes and vectors and new math to work out as i go i'm struggling to find the erroneous calculation(s) and would really appreciate any help. Apologies if this is not suitable as a question! CollisionPolygon.java: package biz.hireholly.gameplay; import android.graphics.Canvas; import android.graphics.Color; import android.graphics.Paint; import biz.hireholly.gameplay.Types.Vect; public class CollisionPolygon { Paint paint; private Vect[] vertices; private Vect[] separationAxes; int x; int y; CollisionPolygon(Vect[] vertices){ this.vertices = vertices; //compute edges and separations axes separationAxes = new Vect[vertices.length]; for (int i = 0; i < vertices.length; i++) { // get the current vertex Vect p1 = vertices[i]; // get the next vertex Vect p2 = vertices[i + 1 == vertices.length ? 0 : i + 1]; // subtract the two to get the edge vector Vect edge = p1.subtract(p2); // get either perpendicular vector Vect normal = edge.perp(); // the perp method is just (x, y) => (-y, x) or (y, -x) separationAxes[i] = normal; } paint = new Paint(); paint.setColor(Color.RED); } public void draw(Canvas c, int xPos, int yPos){ for (int i = 0; i < vertices.length; i++) { Vect v1 = vertices[i]; Vect v2 = vertices[i + 1 == vertices.length ? 0 : i + 1]; c.drawLine( xPos + v1.x, yPos + v1.y, xPos + v2.x, yPos + v2.y, paint); } } public void update(int xPos, int yPos){ x = xPos; y = yPos; } /* consider changing to a static function */ public boolean intersects(CollisionPolygon p){ // loop over this polygons separation exes for (Vect axis : separationAxes) { // project both shapes onto the axis Vect p1 = this.minMaxProjection(axis); Vect p2 = p.minMaxProjection(axis); // do the projections overlap? if (!p1.overlap(p2)) { // then we can guarantee that the shapes do not overlap return false; } } // loop over the other polygons separation axes Vect[] sepAxesOther = p.getSeparationAxes(); for (Vect axis : sepAxesOther) { // project both shapes onto the axis Vect p1 = this.minMaxProjection(axis); Vect p2 = p.minMaxProjection(axis); // do the projections overlap? if (!p1.overlap(p2)) { // then we can guarantee that the shapes do not overlap return false; } } // if we get here then we know that every axis had overlap on it // so we can guarantee an intersection return true; } /* Note projections wont actually be acurate if the axes aren't normalised * but that's not necessary since we just need a boolean return from our * intersects not a Minimum Translation Vector. */ private Vect minMaxProjection(Vect axis) { float min = axis.dot(new Vect(vertices[0].x+x, vertices[0].y+y)); float max = min; for (int i = 1; i < vertices.length; i++) { float p = axis.dot(new Vect(vertices[i].x+x, vertices[i].y+y)); if (p < min) { min = p; } else if (p > max) { max = p; } } Vect minMaxProj = new Vect(min, max); return minMaxProj; } public Vect[] getSeparationAxes() { return separationAxes; } public Vect[] getVertices() { return vertices; } } Vect.java: package biz.hireholly.gameplay.Types; /* NOTE: Can also be used to hold vertices! Projections, coordinates ect */ public class Vect{ public float x; public float y; public Vect(float x, float y){ this.x = x; this.y = y; } public Vect perp() { return new Vect(-y, x); } public Vect subtract(Vect other) { return new Vect(x - other.x, y - other.y); } public boolean overlap(Vect other) { if(y > other.x && other.y > x){ return true; } return false; } /* used specifically for my SAT implementation which i'm figuring out as i go, * references for later.. * http://www.gamedev.net/page/resources/_/technical/game-programming/2d-rotated-rectangle-collision-r2604 * http://www.codezealot.org/archives/55 */ public float scalarDotProjection(Vect other) { //multiplier = dot product / length^2 float multiplier = dot(other) / (x*x + y*y); //to get the x/y of the projection vector multiply by x/y of axis float projX = multiplier * x; float projY = multiplier * y; //we want to return the dot product of the projection, it's meaningless but useful in our SAT case return dot(new Vect(projX,projY)); } public float dot(Vect other){ return (other.x*x + other.y*y); } }

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  • Bullet Physics - Casting a ray straight down from a rigid body (first person camera)

    - by Hydrocity
    I've implemented a first person camera using Bullet--it's a rigid body with a capsule shape. I've only been using Bullet for a few days and physics engines are new to me. I use btRigidBody::setLinearVelocity() to move it and it collides perfectly with the world. The only problem is the Y-value moves freely, which I temporarily solved by setting the Y-value of the translation vector to zero before the body is moved. This works for all cases except when falling from a height. When the body drops off a tall object, you can still glide around since the translate vector's Y-value is being set to zero, until you stop moving and fall to the ground (the velocity is only set when moving). So to solve this I would like to try casting a ray down from the body to determine the Y-value of the world, and checking the difference between that value and the Y-value of the camera body, and disable or slow down movement if the difference is large enough. I'm a bit stuck on simply casting a ray and determining the Y-value of the world where it struck. I've implemented this callback: struct AllRayResultCallback : public btCollisionWorld::RayResultCallback{ AllRayResultCallback(const btVector3& rayFromWorld, const btVector3& rayToWorld) : m_rayFromWorld(rayFromWorld), m_rayToWorld(rayToWorld), m_closestHitFraction(1.0){} btVector3 m_rayFromWorld; btVector3 m_rayToWorld; btVector3 m_hitNormalWorld; btVector3 m_hitPointWorld; float m_closestHitFraction; virtual btScalar addSingleResult(btCollisionWorld::LocalRayResult& rayResult, bool normalInWorldSpace) { if(rayResult.m_hitFraction < m_closestHitFraction) m_closestHitFraction = rayResult.m_hitFraction; m_collisionObject = rayResult.m_collisionObject; if(normalInWorldSpace){ m_hitNormalWorld = rayResult.m_hitNormalLocal; } else{ m_hitNormalWorld = m_collisionObject->getWorldTransform().getBasis() * rayResult.m_hitNormalLocal; } m_hitPointWorld.setInterpolate3(m_rayFromWorld, m_rayToWorld, m_closestHitFraction); return 1.0f; } }; And in the movement function, I have this code: btVector3 from(pos.x, pos.y + 1000, pos.z); // pos is the camera's rigid body position btVector3 to(pos.x, 0, pos.z); // not sure if 0 is correct for Y AllRayResultCallback callback(from, to); Base::getSingletonPtr()->m_btWorld->rayTest(from, to, callback); So I have the callback.m_hitPointWorld vector, which seems to just show the position of the camera each frame. I've searched Google for examples of casting rays, as well as the Bullet documentation, and it's been hard to just find an example. An example is really all I need. Or perhaps there is some method in Bullet to keep the rigid body on the ground? I'm using Ogre3D as a rendering engine, and casting a ray down is quite straightforward with that, however I want to keep all the ray casting within Bullet for simplicity. Could anyone point me in the right direction? Thanks.

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  • Detect duplicate in a subset from a set of elements

    - by Abhinav Shrivastava
    I have a set of numbers say : 1 1 2 8 5 6 6 7 8 8 4 2... I want to detect the duplicate element in subsets(of given size say k) of the above numbers... For example : Consider the increasing subsets(for example consider k=3) Subset 1 :{1,1,2} Subset 2 :{1,2,8} Subset 3 :{2,8,5} Subset 4 :{8,5,6} Subset 5 :{5,6,6} Subset 6 :{6,6,7} .... .... So my algorithm should detect that subset 1,5,6 contains duplicates.. My approach : 1)Copy the 1st k elements to a temporary array(vector) 2) using #include file in C++ STL...using unique() I would determine if there's any change in size of vector.. Any other clue how to approach this problem..

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  • Google search results are invalid

    - by Rufus
    I'm writing a program that lets a user perform a Google search. When the result comes back, all of the links in the search results are links not to other sites but to Google, and if the user clicks on one, the page is fetched not from the other site but from Google. Can anyone explain how to fix this problem? My Google URL consists of this: http://google.com/search?q=gargle But this is what I get back when the user clicks on the Wikipedia search result, which was http://www.google.com/url?q=http://en.wikipedia.org/wiki/Gargling&sa=U&ei=_4vkT5y555Wh6gGBeOzECg&ved=0CBMQejAe&usg=AFQjeNHd1eRV8Xef3LGeH6AvGxt-AF-Yjw <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html lang="en" dir="ltr" class="client-nojs" xmlns="http://www.w3.org/1999/xhtml"> <head> <title>Gargling - Wikipedia, the free encyclopedia</title> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /> <meta http-equiv="Content-Style-Type" content="text/css" /> <meta name="generator" content="MediaWiki 1.20wmf5" /> <meta http-equiv="last-modified" content="Fri, 09 Mar 2012 12:34:19 +0000" /> <meta name="last-modified-timestamp" content="1331296459" /> <meta name="last-modified-range" content="0" /> <link rel="alternate" type="application/x-wiki" title="Edit this page" > <link rel="edit" title="Edit this page" > <link rel="apple-touch-icon" > <link rel="shortcut icon" > <link rel="search" type="application/opensearchdescription+xml" > <link rel="EditURI" type="application/rsd+xml" > <link rel="copyright" > <link rel="alternate" type="application/atom+xml" title="Wikipedia Atom feed" > <link rel="stylesheet" href="//bits.wikimedia.org/en.wikipedia.org/load.php?debug=false&amp;lang=en&amp;modules=ext.gadget.teahouse%7Cext.wikihiero%7Cmediawiki.legacy.commonPrint%2Cshared%7Cskins.vector&amp;only=styles&amp;skin=vector&amp;*" type="text/css" media="all" /> <style type="text/css" media="all">#mwe-lastmodified { display: none; }</style><meta name="ResourceLoaderDynamicStyles" content="" /> <link rel="stylesheet" href="//bits.wikimedia.org/en.wikipedia.org/load.php?debug=false&amp;lang=en&amp;modules=site&amp;only=styles&amp;skin=vector&amp;*" type="text/css" media="all" /> <style type="text/css" media="all">a:lang(ar),a:lang(ckb),a:lang(fa),a:lang(kk-arab),a:lang(mzn),a:lang(ps),a:lang(ur){text-decoration:none} /* cache key: enwiki:resourceloader:filter:minify-css:7:d5a1bf6cbd05fc6cc2705e47f52062dc */</style>

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  • How to implment the database for event conditions and item bonuses for a browser based game

    - by Saifis
    I am currently creating a browser based game, and was wondering what was the standard approach in making diverse conditions and status bonuses database wise. Currently considering two cases. Event Conditions Needs min 1000 gold Needs min Lv 10 Needs certain item. Needs fulfillment of another event Status Bonus Reduces damage by 20% +100 attack points Deflects certain type of attack I wish to be able to continually change these parameters during the process of production and operation, so having them hard-coded isn't the best way. All I could come up with are the following two methods. Method 1 Create a table that contains each conditions with needed attributes Have a model named conditions with all the attributes it would need to set them conditions condition_type (level, money_min, money_max item, event_aquired) condition_amount prerequisite_condition_id prerequisite_item_id Method 2 write it in a DSL form that could be interpreted later in the code Perhaps something like yaml, have a text area in the setting form and have the code interpret it. condition_foo: condition_type :level min_level: 10 condition_type :item item_id: 2 At current Method 2 looks to be more practical and flexible for future changes, trade off being that all the flex must be done on the code side. Not to sure how this is supposed to be done, is it supposed to be hard coded? separate config file? Any help would be appreciated. Added For additional info, it will be implemented with Ruby on Rails

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  • Best way to implement a simple bullet trajectory

    - by AirieFenix
    I searched and searched and although it's a fair simple question, I don't find the proper answer but general ideas (which I already have). I have a top-down game and I want to implement a gun which shoots bullets that follow a simple path (no physics nor change of trajectory, just go from A to B thing). a: vector of the position of the gun/player. b: vector of the mouse position (cross-hair). w: the vector of the bullet's trajectory. So, w=b-a. And the position of the bullet = [x=x0+speed*time*normalized w.x , y=y0+speed*time * normalized w.y]. I have the constructor: public Shot(int shipX, int shipY, int mouseX, int mouseY) { //I get mouse with Gdx.input.getX()/getY() ... this.shotTime = TimeUtils.millis(); this.posX = shipX; this.posY = shipY; //I used aVector = aVector.nor() here before but for some reason didn't work float tmp = (float) (Math.pow(mouseX-shipX, 2) + Math.pow(mouseY-shipY, 2)); tmp = (float) Math.sqrt(Math.abs(tmp)); this.vecX = (mouseX-shipX)/tmp; this.vecY = (mouseY-shipY)/tmp; } And here I update the position and draw the shot: public void drawShot(SpriteBatch batch) { this.lifeTime = TimeUtils.millis() - this.shotTime; //position = positionBefore + v*t this.posX = this.posX + this.vecX*this.lifeTime*speed*Gdx.graphics.getDeltaTime(); this.posY = this.posY + this.vecY*this.lifeTime*speed*Gdx.graphics.getDeltaTime(); ... } Now, the behavior of the bullet seems very awkward, not going exactly where my mouse is (it's like the mouse is 30px off) and with a random speed. I know I probably need to open the old algebra book from college but I'd like somebody says if I'm in the right direction (or points me to it); if it's a calculation problem, a code problem or both. Also, is it possible that Gdx.input.getX() gives me non-precise position? Because when I draw the cross-hair it also draws off the cursor position. Sorry for the long post and sorry if it's a very basic question. Thanks!

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  • Point Light Soft Shadows

    - by notabene
    How to implement soft shadows for omni directional (point) light. We use typical shadow mapping technique. Depth is rendered to texture cube and addresing is pretty simple then. Just using vector from light to fragments world position. It works perfectly. Until you want soft shadows. In our engine we use PCSS technique for spot lights. But for point light there begins troubles. How to sample in 3D? I developed technique when orthonormal basis is created from a direction and upvector (0,1,0). And then multiply sampling vector (something like this (1.0,i/depthMapSize,j/depthMapSize) with this basis. But this (of course :)) looks pretty bad for vectors near (0,1,0) and (0,-1,0). I will appreciate any help on this.

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  • How useful is mounting /tmp noexec?

    - by Novelocrat
    Many people (including the Securing Debian Manual) recommend mounting /tmp with the noexec,nodev,nosuid set of options. This is generally presented as one element of a 'defense-in-depth' strategy, by preventing the escalation of an attack that lets someone write a file, or an attack by a user with a legitimate account but no other writable space. Over time, however, I've encountered arguments (most prominently by Debian/Ubuntu Developer Colin Watson) that noexec is a useless measure, for a couple potential reasons: The user can run /lib/ld-linux.so <binary> in an attempt to get the same effect. The user can still run system-provided interpreters on scripts that can't be run directly Given these arguments, the potential need for more configuration (e.g. debconf likes an executable temporary directory), and the potential loss of convenience, is this a worthwhile security measure? What other holes do you know of that enable circumvention?

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  • Does data mining qualify as an abuse?

    - by Hybryd
    Hi all, today I had a strange experience with my ISP. They disabled my password for internet connection, and when I called them, they enabled it again, but they didn't say why it happened. In the last couple of days I was running a data mining that I made for one forum to get some useful info about business that I'm in. So I thought, maybe my ISP figured that 10,000 page requests in couple of hours to the same site may be some kind of attack. What do you think, does it qualify as an attack? Is it even ok to data mine in that way?

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  • Understanding Unity3d physics: where is the force applied?

    - by Heisenbug
    I'm trying to understand which is the right way to apply forces to a RigidBody. I noticed that there are AddForce and AddRelativeForce methods, one applied in world space coordinate system meanwhile the other in the local space. The thing that I do not understand is the following: usually in physics library (es. Bullet) we can specify the force vector and also the force application point. How can I do this in Unity? Is it possible to apply a force vector in a specific point relative to the given RigidBody coordinate system? Where does AddForce apply the force?

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  • Ray Picking Problems

    - by A Name I Haven't Decided On
    I've read so many answers on here about how to do Ray Picking, that I thought I had the idea of it down. But when I try to implement it in my game, I get garbage. I'm working with LWJGL. Here's the code: public static Ray getPick(int mouseX, int mouseY){ glPushMatrix(); //Setting up the Mouse Clip Vector4f mouseClip = new Vector4f((float)mouseX * 2 / 960f - 1, 1 - (float)mouseY * 2 / 640f ,0 ,1); //Loading Matrices FloatBuffer modMatrix = BufferUtils.createFloatBuffer(16); FloatBuffer projMatrix = BufferUtils.createFloatBuffer(16); glGetFloat(GL_MODELVIEW_MATRIX, modMatrix); glGetFloat(GL_PROJECTION_MATRIX, projMatrix); //Assigning Matrices Matrix4f proj = new Matrix4f(); Matrix4f model = new Matrix4f(); model.load(modMatrix); proj.load(projMatrix); //Multiplying the Projection Matrix by the Model View Matrix Matrix4f tempView = new Matrix4f(); Matrix4f.mul(proj, model, tempView); tempView.invert(); //Getting the Camera Position in World Space. The 4th Column of the Model View Matrix. model.invert(); Point cameraPos = new Point(model.m30, model.m31, model.m32); //Theoretically getting the vector the Picking Ray goes Vector4f rayVector = new Vector4f(); Matrix4f.transform(tempView, mouseClip, rayVector); rayVector.translate((float)-cameraPos.getX(),(float) -cameraPos.getY(),(float) -cameraPos.getZ(), 0f); rayVector.normalise(); glPopMatrix(); //This Basically Spits out a value that changes as the Camera moves. //When the Mouse moves, the values change around 0.001 points from screen edge to edge. System.out.format("Vector: %f %f %f%n", rayVector.x, rayVector.y, rayVector.z); //return new Ray(cameraPos, rayVector); return null; } I don't really know why this isn't working. I was hoping some more experienced eyes might be able to help me out. I can get the camera position like a champ, it's the vector the rays going in that I can't seem to get right. Thanks.

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  • game play strategy in an arena

    - by joulesm
    I am writing a player's behavior for an arena game, and I'm wondering if you can offer some strategies. I'm writing it in Python, but I'm just interested in the high level game play. Here are the game aspects: Arena is a circle of a given size. The arena size shrinks every round to help break ties. Players are much smaller circles, can be on teams of 1 or 2 players. Players attack by colliding with other players, and based on the physics of the collision (speed of both players, angle), one could force another player out of the arena. Once a player is out of the arena, they are out of the game (for that round). The goal is to be the only team with players left in the arena. All other players have been pushed (through collisions or mistakes) out of the arena. It is possible for there to be no winner if the last two players exit the arena at the same time. Once the player has been programmed, the game just runs. There is no human intervention in the game. I'm thinking it's easiest to implement a few simple programmatic rules for my player to follow. For example, stay close to center of the arena, attack opponents from the inner side of the arena, etc. Are there any good simple game strategies? Would adding a random aspect to the game help? For example, to avoid predictability by the other team or something. Thanks in advance.

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  • What Kind of Spam is This? Testing Blog Comment Limits

    - by Yar
    I received this comment on one of my blogs today (on blogger.com): Easily I agree but I about the post should acquire more info then it has. It's the third in a series. Before there was: I will not acquiesce in on it. I over precise post. Expressly the title attracted me to be familiar with the sound story. and before that Your blog keeps getting better and better! Your older articles are not as good as newer ones you have a lot more creativity and originality now keep it up! It is obviously computer-generated (well, not this last one). The comments are from Anonymous, so they're not trying to legitimate a user on Blogger. Is this a spam attack? What might its goal be? Or are they just testing my blog to see if I reject or not? Does this kind of "attack" have a name?

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  • Translate along local axis

    - by Aaron
    I have an object with a position matrix and a rotation matrix (derived from a quaternion, but I digress). I'm able to translate this object along world-relative vectors, but I'm trying to figure out how to translate it along local-relative vectors. So if the object is tilted 45 degrees around its Z-axis the vector (1, 0, 0) would make it move to the upper right. For world-space translations I simply turn the movement vector into a matrix and multiply it by the position matrix: position_mat = translation_mat * position_mat. For local-space translations I'd think I'd have to use the rotation matrix into that formula, but I see the object spin around instead when I apply a translation over time no matter where I multiply the rotation matrix.

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  • My server's been hacked EMERGENCY

    - by Grant unwin
    I'm on my way into work at 9.30 p.m. on a Sunday because our server has been compromised somehow and was resulting in a DOS attack on our provider. The servers access to the Internet has been shut down which means over 5-600 of our clients sites are now down. Now this could be an FTP hack, or some weakness in code somewhere. I'm not sure till I get there. How can I track this down quickly? We're in for a whole lot of litigation if I don't get the server back up ASAP. Any help is appreciated. UPDATE Thanks to everyone for your help. Luckily I WASN'T the only person responsible for this server, just the nearest. We managed to resolve this problem, although it may not apply to many others in a different situation. I'll detail what we did. We unplugged the server from the net. It was performing (attempting to perform) a Denial Of Service attack on another server in Indonesia, and the guilty party was also based there. We firstly tried to identify where on the server this was coming from, considering we have over 500 sites on the server, we expected to be moonlighting for some time. However, with SSH access still, we ran a command to find all files edited or created in the time the attacks started. Luckily, the offending file was created over the winter holidays which meant that not many other files were created on the server at that time. We were then able to identify the offending file which was inside the uploaded images folder within a ZenCart website. After a short cigarette break we concluded that, due to the files location, it must have been uploaded via a file upload facility that was inadequetly secured. After some googling, we found that there was a security vulnerability that allowed files to be uploaded, within the ZenCart admin panel, for a picture for a record company. (The section that it never really even used), posting this form just uploaded any file, it did not check the extension of the file, and didn't even check to see if the user was logged in. This meant that any files could be uploaded, including a PHP file for the attack. We secured the vulnerability with ZenCart on the infected site, and removed the offending files. The job was done, and I was home for 2 a.m. The Moral - Always apply security patches for ZenCart, or any other CMS system for that matter. As when security updates are released, the whole world is made aware of the vulnerability. - Always do backups, and backup your backups. - Employ or arrange for someone that will be there in times like these. To prevent anyone from relying on a panicy post on Server Fault. Happy servering!

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  • Best way to calculate unit deaths in browser game combat?

    - by MikeCruz13
    My browser game's combat system is written and mechanically functioning well. It's written in PHP and uses a SQL database. I'm happy with the unit balance in relation to one another. I am, however, a little worried about how I'm calculating unit deaths when one player attacks another because the deaths seem to pile up a little fast for my taste. For this system, a battle doesn't just trigger, calculate winner, and end. Instead, it is allowed to go for several rounds (say one round every 15 mins.) until one side passes a threshold of being too strong for the other player and allows players to send reinforcements between rounds. Each round, units pair up and attack each other. Essentially what I do is calculate the damage: AP = Attack Points HP = Hit Points Units AP * Quantity * Random Factors * other factors (such as attrition) I take that and divide by the defending unit's HP to find the number of casualties of defending units. So, for example (simplified to take out some factors), if I have: 500 attackers with 50 AP vs 1000 defenders with 100 HP = 250 deaths. I wonder if that last step could be handled better to reduce the deaths piling up. Some ideas: I just change all the units with more HP? I make sure to set the Attacking unit's AP to be a max of the defender's HP to make sure they only kill 1 unit. (is that fair if I have less huge units vs many small units?) I spread the damage around more by including the defending unit's quantity more? i.e. in that scenario some are dead and some are 50% damage. (How would I track this every round?) Other better mathematical approaches?

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  • How do I best remove an entity from my game loop when it is dead?

    - by Iain
    Ok so I have a big list of all my entities which I loop through and update. In AS3 I can store this as an Array (dynamic length, untyped), a Vector (typed) or a linked list (not native). At the moment I'm using Array but I plan to change to Vector or linked list if it is faster. Anyway, my question, when an Entity is destroyed, how should I remove it from the list? I could null its position, splice it out or just set a flag on it to say "skip over me, I'm dead." I'm pooling my entities, so an Entity that is dead is quite likely to be alive again at some point. For each type of collection what is my best strategy, and which combination of collection type and removal method will work best?

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  • How to block null/blank user-agents in IIS 7.5

    - by Jeremy
    We are going through a large scale DDOS attack, but it isn't the typical bot-net that our Cisco Guard can handle, it is a BitTorrent attack. This is new to me, so I am unsure how to stop it. Here are the stats IIS is processing between 40 and 100 requests per second from BitTorrent clients. We have about 20% of the User Agents, but the other 75% are blank. We want to block the blank user agents at the server level. What is the best approach?

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  • Resolving equivalence relations

    - by Luca Cerone
    I am writing a function to label the connected component in an image (I know there are several libraries outside, I just wanted to play with the algorithm). To do this I label the connected regions with different labels and create an equivalence table that contain information on the labels belonging to the same connected component. As an example if my equivalence table (vector of vector) looks something like: 1: 1,3 2: 2,3 3: 1,2,3 4: 4 It means that in the image there are 2 different regions, one made of elements that are labelled 1,2,3 and an other made of elements labelled 4. What is an easy and efficient way to resolve the equivalences and end up with something that looks like: 1: 1,2,3 2: 4 that I can use to "merge" the different connected regions belonging to the same connected component? Thanks a lot for the help!

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