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• Handling packet impersonating in client-server model online game

  - by TheDespite

  I am designing a server-client model game library/engine. How do I, and should I even bother to handle frequent update packet possible impersonating? In my current design anyone could copy a packet from someone else and modify it to execute any non-critical action for another client. I am currently compressing all datagrams so that adds just a tad of security. Edit: One way I thought about was to send a unique "key" to the verified client every x_time and then the client has to add that to all of it's update packets until a new key is sent. Edit2: I should have mentioned that I am not concerned about whether the actions described in the packet are available to the client at the time, this is all checked by the server which I thought was obvious. I am only concerned about someone sending packets for another client.

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• Good book or tutorial for learning how to apply integration methods

  - by Cumatru

  I'm looking to animate a graph layout using edges as springs and nodes as weights ( a node with more links will have a bigger weight ). I'm not capable of wrapping my head around the usage of mathematical and physics relations in my application. As far as i read, Runge Kutta 4 ( preferably ) or Verlet will be a good choice, but i have problems with understanding how they really work, and what physics equations should i apply. If i can't understand them, i can't use them. I'm looking for a book or a tutorial which describe the things that i need.

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• How to port animation from one skeleton to another?

  - by shawn

  While I need to do this in a Blender3D modeler script, the math should be similar for other modelers or realtime engines. Blender3D specific terminology: Armature = skeleton EditBone = rest pose bone (stores the rest pose matrix) PoseBone = can store a different pose (animation matrix) for each frame of your animation I need to share animations (Blender Actions) between Armatures which have EditBones with same names and which have the same positions, but can have different (rest pose) angles and scales. Plus the Armatures might have different bone hierarchy (bone parenting/ no bone parenting). Why I need this: I've made an importer/exporter for a 3d format for a game. The format doesn't store enough info to connect/parent the bones, which makes posing/animating character models in a 3d modeller nearly impossible (original model files for the 3d modeler don't exist, this is for modding). As there are only 2 character skeleton types in the game, I decided to optionally allow to generate the bone from a hardcoded data in the model importer and undo that in the exporter. This allows to easily pose the model for checking weights, easily create weights, makes it easier for Blender to generate automatic weights and of course makes animating possible. This worked perfectly: the importer optionally generated the Armature itself and the exporter removed those changes, so the exported model works with existing animations in the game. But now I'm writing an importer and exporter for the game's animation format and here come the problems of: Trying to make original animations work in Blender with my "custom" (modified) Armature Trying to make animations created by using the "custom" (modified) Armature work with the original models in the game (and Blender). Constraints or bone snapping inside Blender won't work as they don't care that the bones have different angles in the rest pose, they will still face the same direction. It seems I just need to get the "difference" between the EditBone matrices of all EditBones for the two Armatures somehow and apply that difference to PoseBone matrices of all PoseBones, for all frames of my animation. I need to know how to get that difference and how to apply it. BTW, PoseBone matrices are relative to rest pose, they are by default [1.000000, 0.000000, 0.000000, 0.000000](matrix [row 0]) [0.000000, 1.000000, 0.000000, 0.000000](matrix [row 1]) [0.000000, 0.000000, 1.000000, 0.000000](matrix [row 2]) [0.000000, 0.000000, 0.000000, 1.000000](matrix [row 3]) So the question is: How to get the difference between two bone (EditBone) matrices to apply that difference to the animation matrices (PoseBone matrices)? Please be easy on the matrix math.

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• GameState management hierarchical FSM vs stack based FSM

  - by user8363

  I'm reading a bit on Finite State Machines to handle game states (or screens). I would like to build a rather decent FSM that can handle multiple screens. e.g. while the game is running I want to be able to pop-up an ingame menu and when that happens the main screen must stop updating (the game is paused) but must still be visible in the background. However when I open an inventory pop-up the main screen must be visible and continue updating etc. I'm a bit confused about the difference in implementation and functionality between hierarchical FSM's and FSM's that handle a stack of states instead. Are they basically the same? Or are there important differences?

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• How can I use iteration to lead targets?

  - by e100

  In my 2D game, I have stationary AI turrets firing constant speed bullets at moving targets. So far I have used a quadratic solver technique to calculate where the turret should aim in advance of the target, which works well (see Algorithm to shoot at a target in a 3d game, Predicting enemy position in order to have an object lead its target). But it occurs to me that an iterative technique might be more realistic (e.g. it should fire even when there is no exact solution), efficient and tunable - for example one could change the number of iterations to improve accuracy. I thought I could calculate the current range and thus an initial (inaccurate) bullet flight time to target, then work out where the target would actually be by that time, then recalculate a more accurate range, then recalculate flight time, etc etc. I think I am missing something obvious to do with the time term, but my aimpoint calculation does not currently converge after the significant initial correction in the first iteration: import math def aimpoint(iters, target_x, target_y, target_vel_x, target_vel_y, bullet_speed): aimpoint_x = target_x aimpoint_y = target_y range = math.sqrt(aimpoint_x**2 + aimpoint_y**2) time_to_target = range / bullet_speed time_delta = time_to_target n = 0 while n <= iters: print "iteration:", n, "target:", "(", aimpoint_x, aimpoint_y, ")", "time_delta:", time_delta aimpoint_x += target_vel_x * time_delta aimpoint_y += target_vel_y * time_delta range = math.sqrt(aimpoint_x**2 + aimpoint_y**2) new_time_to_target = range / bullet_speed time_delta = new_time_to_target - time_to_target n += 1 aimpoint(iters=5, target_x=0, target_y=100, target_vel_x=1, target_vel_y=0, bullet_speed=100)

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• How do I efficiently code both the client and server at the same time?

  - by liamzebedee

  I'm coding my game using a client-server model. When playing on singleplayer, the game starts a local server, and interacts with it just like a remote server (multiplayer). I have done this to avoid coding separate singleplayer and multiplayer code. I have just started coding and have encountered a major problem. Currently I'm developing the game in Eclipse, having all the game classes organized into packages. Then, in my server code, I just use all the classes in the client packages. The problem is, these client classes have variables that are specific to rendering, which obviously wouldn't be performed on a server. Should I create modified versions of the client classes to use in the server? Or should I just modify the client classes with a boolean, to indicate if its the client/server using it. Are there any other options I have? I just had a thought about maybe using the server class as the core class, then extending it with rendering stuff?

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• Why am I not getting an sRGB default framebuffer?

  - by Aaron Rotenberg

  I'm trying to make my OpenGL Haskell program gamma correct by making appropriate use of sRGB framebuffers and textures, but I'm running into issues making the default framebuffer sRGB. Consider the following Haskell program, compiled for 32-bit Windows using GHC and linked against 32-bit freeglut: import Foreign.Marshal.Alloc(alloca) import Foreign.Ptr(Ptr) import Foreign.Storable(Storable, peek) import Graphics.Rendering.OpenGL.Raw import qualified Graphics.UI.GLUT as GLUT import Graphics.UI.GLUT(($=)) main :: IO () main = do (_progName, _args) <- GLUT.getArgsAndInitialize GLUT.initialDisplayMode $= [GLUT.SRGBMode] _window <- GLUT.createWindow "sRGB Test" -- To prove that I actually have freeglut working correctly. -- This will fail at runtime under classic GLUT. GLUT.closeCallback $= Just (return ()) glEnable gl_FRAMEBUFFER_SRGB colorEncoding <- allocaOut $ glGetFramebufferAttachmentParameteriv gl_FRAMEBUFFER gl_FRONT_LEFT gl_FRAMEBUFFER_ATTACHMENT_COLOR_ENCODING print colorEncoding allocaOut :: Storable a => (Ptr a -> IO b) -> IO a allocaOut f = alloca $ \ptr -> do f ptr peek ptr On my desktop (Windows 8 64-bit with a GeForce GTX 760 graphics card) this program outputs 9729, a.k.a. gl_LINEAR, indicating that the default framebuffer is using linear color space, even though I explicitly requested an sRGB window. This is reflected in the rendering results of the actual program I'm trying to write - everything looks washed out because my linear color values aren't being converted to sRGB before being written to the framebuffer. On the other hand, on my laptop (Windows 7 64-bit with an Intel graphics chip), the program prints 0 (huh?) and I get an sRGB default framebuffer by default whether I request one or not! And on both machines, if I manually create a non-default framebuffer bound to an sRGB texture, the program correctly prints 35904, a.k.a. gl_SRGB. Why am I getting different results on different hardware? Am I doing something wrong? How can I get an sRGB framebuffer consistently on all hardware and target OSes?

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• GetData() error creating framebuffer

  - by Lelezeus

  I'm currently porting a game written in C# with XNA library to Android with Monogame. I have a Texture2D and i'm trying to get an array of uint in this way: Texture2d textureDeform = game.Content.Load<Texture2D>("Texture/terrain"); uint[] pixelDeformData = new uint[textureDeform.Width * textureDeform.Height]; textureDeform.GetData(pixelDeformData, 0, textureDeform.Width * textureDeform.Height); I get the following exception: System.Exception: Error creating framebuffer: Zero at Microsoft.Xna.Framework.Graphics.Texture2D.GetTextureData (Int32 ThreadPriorityLevel) [0x00000] in :0 I found that the problem is in private byte[] GetTextureData(int ThreadPriorityLevel) creating the framebuffer: private byte[] GetTextureData(int ThreadPriorityLevel) { int framebufferId = -1; int renderBufferID = -1; GL.GenFramebuffers(1, ref framebufferId); // framebufferId is still -1 , why can't be created? GraphicsExtensions.CheckGLError(); GL.BindFramebuffer(All.Framebuffer, framebufferId); GraphicsExtensions.CheckGLError(); //renderBufferIDs = new int[currentRenderTargets]; GL.GenRenderbuffers(1, ref renderBufferID); GraphicsExtensions.CheckGLError(); // attach the texture to FBO color attachment point GL.FramebufferTexture2D(All.Framebuffer, All.ColorAttachment0, All.Texture2D, this.glTexture, 0); GraphicsExtensions.CheckGLError(); // create a renderbuffer object to store depth info GL.BindRenderbuffer(All.Renderbuffer, renderBufferID); GraphicsExtensions.CheckGLError(); GL.RenderbufferStorage(All.Renderbuffer, All.DepthComponent24Oes, Width, Height); GraphicsExtensions.CheckGLError(); // attach the renderbuffer to depth attachment point GL.FramebufferRenderbuffer(All.Framebuffer, All.DepthAttachment, All.Renderbuffer, renderBufferID); GraphicsExtensions.CheckGLError(); All status = GL.CheckFramebufferStatus(All.Framebuffer); if (status != All.FramebufferComplete) throw new Exception("Error creating framebuffer: " + status); ... } The frameBufferId is still -1, seems that framebuffer could not be generated and I don't know why. Any help would be appreciated, thank you in advance.

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• GLM Velocity Vectors - Basic Maths to Simulate Steering

  - by Reanimation

  UPDATE - Code updated below but still need help adjusting my math. I have a cube rendered on the screen which represents a car (or similar). Using Projection/Model matrices and Glm I am able to move it back and fourth along the axes and rotate it left or right. I'm having trouble with the vector mathematics to make the cube move forwards no matter which direction it's current orientation is. (ie. if I would like, if it's rotated right 30degrees, when it's move forwards, it travels along the 30degree angle on a new axes). I hope I've explained that correctly. This is what I've managed to do so far in terms of using glm to move the cube: glm::vec3 vel; //velocity vector void renderMovingCube(){ glUseProgram(movingCubeShader.handle()); GLuint matrixLoc4MovingCube = glGetUniformLocation(movingCubeShader.handle(), "ProjectionMatrix"); glUniformMatrix4fv(matrixLoc4MovingCube, 1, GL_FALSE, &ProjectionMatrix[0][0]); glm::mat4 viewMatrixMovingCube; viewMatrixMovingCube = glm::lookAt(camOrigin, camLookingAt, camNormalXYZ); vel.x = cos(rotX); vel.y=sin(rotX); vel*=moveCube; //move cube ModelViewMatrix = glm::translate(viewMatrixMovingCube,globalPos*vel); //bring ground and cube to bottom of screen ModelViewMatrix = glm::translate(ModelViewMatrix, glm::vec3(0,-48,0)); ModelViewMatrix = glm::rotate(ModelViewMatrix, rotX, glm::vec3(0,1,0)); //manually turn glUniformMatrix4fv(glGetUniformLocation(movingCubeShader.handle(), "ModelViewMatrix"), 1, GL_FALSE, &ModelViewMatrix[0][0]); //pass matrix to shader movingCube.render(); //draw glUseProgram(0); } keyboard input: void keyboard() { char BACKWARD = keys['S']; char FORWARD = keys['W']; char ROT_LEFT = keys['A']; char ROT_RIGHT = keys['D']; if (FORWARD) //W - move forwards { globalPos += vel; //globalPos.z -= moveCube; BACKWARD = false; } if (BACKWARD)//S - move backwards { globalPos.z += moveCube; FORWARD = false; } if (ROT_LEFT)//A - turn left { rotX +=0.01f; ROT_LEFT = false; } if (ROT_RIGHT)//D - turn right { rotX -=0.01f; ROT_RIGHT = false; } Where am I going wrong with my vectors? I would like change the direction of the cube (which it does) but then move forwards in that direction.

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• Implementing Light Volume Front Faces

  - by cubrman

  I recently read an article about light indexed deferred rendering from here: http://code.google.com/p/lightindexed-deferredrender/ It explains its ideas in a clear way, but there was one point that I failed to understand. It in fact is one of the most interesting ones, as it explains how to implement transparency with this approach: Typically when rendering light volumes in deferred rendering, only surfaces that intersect the light volume are marked and lit. This is generally accomplished by a “shadow volume like” technique of rendering back faces – incrementing stencil where depth is greater than – then rendering front faces and only accepting when depth is less than and stencil is not zero. By only rendering front faces where depth is less than, all future lookups by fragments in the forward rendering pass will get all possible lights that could hit the fragment. Can anyone explain how exactly you need to render only front faces? Another question is why do you need the front faces at all? Why can't we simply render all the lights and store the ones that overlap at this pixel in a texture? Does this approach serves as a cut-off plane to discard lights blocked by opaque geometry?

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• obj-c classes and sub classes (Cocos2d) conversion

  - by Lewis

  Hi I'm using this version of cocos2d: https://github.com/krzysztofzablocki/CCNode-SFGestureRecognizers Which supports the UIGestureRecognizer within a CCLayer in a cocos2d scene like so: @interface HelloWorldLayer : CCLayer <UIGestureRecognizerDelegate> { } Now I want to make this custom gesture work within the scene, attaching it to a sprite in cocos2d: #import <Foundation/Foundation.h> #import <UIKit/UIGestureRecognizerSubclass.h> @protocol OneFingerRotationGestureRecognizerDelegate <NSObject> @optional - (void) rotation: (CGFloat) angle; - (void) finalAngle: (CGFloat) angle; @end @interface OneFingerRotationGestureRecognizer : UIGestureRecognizer { CGPoint midPoint; CGFloat innerRadius; CGFloat outerRadius; CGFloat cumulatedAngle; id <OneFingerRotationGestureRecognizerDelegate> target; } - (id) initWithMidPoint: (CGPoint) midPoint innerRadius: (CGFloat) innerRadius outerRadius: (CGFloat) outerRadius target: (id) target; - (void)reset; - (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event; - (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event; - (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event; - (void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event; @end #include <math.h> #import "OneFingerRotationGestureRecognizer.h" @implementation OneFingerRotationGestureRecognizer // private helper functions CGFloat distanceBetweenPoints(CGPoint point1, CGPoint point2); CGFloat angleBetweenLinesInDegrees(CGPoint beginLineA, CGPoint endLineA, CGPoint beginLineB, CGPoint endLineB); - (id) initWithMidPoint: (CGPoint) _midPoint innerRadius: (CGFloat) _innerRadius outerRadius: (CGFloat) _outerRadius target: (id <OneFingerRotationGestureRecognizerDelegate>) _target { if ((self = [super initWithTarget: _target action: nil])) { midPoint = _midPoint; innerRadius = _innerRadius; outerRadius = _outerRadius; target = _target; } return self; } /** Calculates the distance between point1 and point 2. */ CGFloat distanceBetweenPoints(CGPoint point1, CGPoint point2) { CGFloat dx = point1.x - point2.x; CGFloat dy = point1.y - point2.y; return sqrt(dx*dx + dy*dy); } CGFloat angleBetweenLinesInDegrees(CGPoint beginLineA, CGPoint endLineA, CGPoint beginLineB, CGPoint endLineB) { CGFloat a = endLineA.x - beginLineA.x; CGFloat b = endLineA.y - beginLineA.y; CGFloat c = endLineB.x - beginLineB.x; CGFloat d = endLineB.y - beginLineB.y; CGFloat atanA = atan2(a, b); CGFloat atanB = atan2(c, d); // convert radiants to degrees return (atanA - atanB) * 180 / M_PI; } #pragma mark - UIGestureRecognizer implementation - (void)reset { [super reset]; cumulatedAngle = 0; } - (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event { [super touchesBegan:touches withEvent:event]; if ([touches count] != 1) { self.state = UIGestureRecognizerStateFailed; return; } } - (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event { [super touchesMoved:touches withEvent:event]; if (self.state == UIGestureRecognizerStateFailed) return; CGPoint nowPoint = [[touches anyObject] locationInView: self.view]; CGPoint prevPoint = [[touches anyObject] previousLocationInView: self.view]; // make sure the new point is within the area CGFloat distance = distanceBetweenPoints(midPoint, nowPoint); if ( innerRadius <= distance && distance <= outerRadius) { // calculate rotation angle between two points CGFloat angle = angleBetweenLinesInDegrees(midPoint, prevPoint, midPoint, nowPoint); // fix value, if the 12 o'clock position is between prevPoint and nowPoint if (angle > 180) { angle -= 360; } else if (angle < -180) { angle += 360; } // sum up single steps cumulatedAngle += angle; // call delegate if ([target respondsToSelector: @selector(rotation:)]) { [target rotation:angle]; } } else { // finger moved outside the area self.state = UIGestureRecognizerStateFailed; } } - (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event { [super touchesEnded:touches withEvent:event]; if (self.state == UIGestureRecognizerStatePossible) { self.state = UIGestureRecognizerStateRecognized; if ([target respondsToSelector: @selector(finalAngle:)]) { [target finalAngle:cumulatedAngle]; } } else { self.state = UIGestureRecognizerStateFailed; } cumulatedAngle = 0; } - (void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event { [super touchesCancelled:touches withEvent:event]; self.state = UIGestureRecognizerStateFailed; cumulatedAngle = 0; } @end Header file for view controller: #import "OneFingerRotationGestureRecognizer.h" @interface OneFingerRotationGestureViewController : UIViewController <OneFingerRotationGestureRecognizerDelegate> @property (nonatomic, strong) IBOutlet UIImageView *image; @property (nonatomic, strong) IBOutlet UITextField *textDisplay; @end then this is in the .m file: gestureRecognizer = [[OneFingerRotationGestureRecognizer alloc] initWithMidPoint: midPoint innerRadius: outRadius / 3 outerRadius: outRadius target: self]; [self.view addGestureRecognizer: gestureRecognizer]; Now my question is, is it possible to add this custom gesture into the cocos2d project found on that github, and if so, what do I need to change in the OneFingerRotationGestureRecognizerDelegate to get it to work within cocos2d. Because at the minute it is setup in a standard iOS project and not a cocos2d project and I do not know enough about UIViews and classing/ sub classing in obj-c to get this to work. Also it seems to inherit from a UIView where cocos2d uses CCLayer. Kind regards, Lewis. I also realise I may have not included enough code from the custom gesture project for readers to interpret it fully, so the full project can be found here: https://github.com/melle/OneFingerRotationGestureDemo

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• Low coupling and tight cohesion

  - by hidayat

  Of course it depends on the situation. But when a lower lever object or system communicate with an higher level system, should callbacks or events be preferred to keeping a pointer to higher level object? For example, we have a world class that has a member variable vector<monster> monsters. When the monster class is going to communicate with the world class, should I prefer using a callback function then or should I have a pointer to the world class inside the monster class?

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• Coarse Collision Detection in highly dynamic environment

  - by Millianz

  I'm currently working a 3D space game with A LOT of dynamic objects that are all moving (there is pretty much no static environment). I have the collision detection and resolution working just fine, but I am now trying to optimize the collision detection (which is currently O(N^2) -- linear search). I thought about multiple options, a bounding volume hierarchy, a Binary Spatial Partitioning tree, an Octree or a Grid. I however need some help with deciding what's best for my situation. A grid seems unfeasible simply due to the space requirements and cache coherence problems. Since everything is so dynamic however, it seems to be that trees aren't ideal either, since they would have to be completely rebuilt every frame. I must admit I never implemented a physics engine that required spatial partitioning, do I indeed need to rebuild the tree every frame (assuming that everything is constantly moving) or can I update the trees after integrating? Advice is much appreciated - to give some more background: You're flying a space ship in an asteroid field, and there are lots and lots of asteroids and some enemy ships, all of which shoot bullets. EDIT: I came across the "Sweep an Prune" algorithm, which seems like the right thing for my purposes. It appears like the right mixture of fast building of the data structures involved and detailed enough partitioning. This is the best resource I can find: http://www.codercorner.com/SAP.pdf If anyone has any suggestions whether or not I'm going in the right direction, please let me know.

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• Algorithm for waypoint path following?

  - by Thierry Savard Saucier

  I have a worldmap, with different cities on it. The player can choose a city from a menu, or click on an available cities on the world map, and the toon should walk over there. I want him to follow a predefined path. Lets say our hero is on the city 1. He clicks on city 4. I want him to follow the path to city 2 and from there to city 4. I was handling this easily with arrow movement (left right top bottom) since its a single check. Now I'm not sure how I should do this. Should I loop threw each possible path and check which one leads me to D the fastest ... and if I do how do I avoid running in circle forever with cities 1-5-2 ?

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• Sprite not rotating around its centre after Scaling at its centre

  - by asma.farhat

  If I scale a sprite at its centre, then try to rotate it around its centre as well, the rotation does not occur around its centre. If you need to rotate, for example a scaled ball,the way its working it is set the scale center at the top left (0,0) set the scale that you want, and then set the rotation center to the middle of the scaled sprite, and then apply the rotation modifier. blaBloBliSprite.setScaleCenter(0, 0); blaBloBliSprite.setScale(0.667f); blaBloBliSprite.setPosition(557, CAMERA_HEIGHT / 2 - blaBloBliSprite.getHeightScaled() / 2); blaBloBliSprite.setRotationCenter(blaBloBliSprite.getWidthScaled() / 2, blaBloBliSprite.getHeightScaled() / 2); But I want to scale a sprite at its centre as well. Is there any way of doing it?

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• Algorithm allowing a good waypoint path following?

  - by Thierry Savard Saucier

  I'm more looking into how should I implement this, either a tutorial or even the name of the concept I'm missing. I'm pretty sure some basic pathfinding algorithm could help me here, but I dont know which one ... I have a worldmap, with different cities on it. The player can choose a city from a menu, or click on an available cities on the world map, and the toon should walk over there. But I want him to follow a predefine path. Lets say our hero is on the city 1. He clicks on city 4. I want him to follow the path to city 2 and from there to city 4. I was handling this easily with arrow movement (left right top bottom) since its a single check. Now I'm not sure how I should do this. Should I loop threw each possible path and check which one leads me to D the fastest ... and if I do how do I avoid running in circle forever with cities 1-5-2 ?

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• Structure gameobjects and call events

  - by waco001

  I'm working on a 2D tile based game in which the player interacts with other game objects (chests, AI, Doors, Houses etc...). The entire map will be stored in a file which I can read. When loading the tilemap, it will find any tile with the ID that represents a gameobject and store it in a hashmap (right data structure I think?). private static HashMap<Integer, Class<GameObject>> gameObjects = new HashMap<Integer, Class<GameObject>>(); How exactly would I go about calling, and checking for events? I figure that I would just call the update, render and input methods of each gameobject using the hashmap. Should I got towards a Minecraft/Bukkit approach (sorry only example I can think of), where the user registers an event, and it gets called whenever that event happens, and where should I go as in resources to learn about that type of programming, (Java, LWJGL). Or should I just loop through the entire hashmap looking for an event that fits? Thanks waco

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• Logarithmic spacing of FFT bins

  - by Mykel Stone

  I'm trying to do the examples within the GameDev.net Beat Detection article ( http://archive.gamedev.net/archive/reference/programming/features/beatdetection/index.html ) I have no issue with performing a FFT and getting the frequency data and doing most of the article. I'm running into trouble though in the section 2.B, Enhancements and beat decision factors. in this section the author gives 3 equations numbered R10-R12 to be used to determine how many bins go into each subband: R10 - Linear increase of the width of the subband with its index R11 - We can choose for example the width of the first subband R12 - The sum of all the widths must not exceed 1024 He says the following in the article: "Once you have equations (R11) and (R12) it is fairly easy to extract 'a' and 'b', and thus to find the law of the 'wi'. This calculus of 'a' and 'b' must be made manually and 'a' and 'b' defined as constants in the source; indeed they do not vary during the song." However, I cannot seem to understand how these values are calculated...I'm probably missing something simple, but learning fourier analysis in a couple of weeks has left me Decimated-in-Mind and I cannot seem to see it.

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• How to fetch only the sprites in the player's range of motion for collision testing? (2D, axis aligned sprites)

  - by Twodordan

  I am working on a 2D sprite game for educational purposes. (In case you want to know, it uses WebGl and Javascript) I've implemented movement using the Euler method (and delta time) to keep things simple. Now I'm trying to tackle collisions. The way I wrote things, my game only has rectangular sprites (axis aligned, never rotated) of various/variable sizes. So I need to figure out what I hit and which side of the target sprite I hit (and I'm probably going to use these intersection tests). The old fashioned method seems to be to use tile based grids, to target only a few tiles at a time, but that sounds silly and impractical for my game. (Splitting the whole level into blocks, having each sprite's bounding box fit multiple blocks I might abide. But if the sprites change size and move around, you have to keep changing which tiles they belong to, every frame, it doesn't sound right.) In Flash you can test collision under one point, but it's not efficient to iterate through all the elements on stage each frame. (hence why people use the tile method). Bottom line is, I'm trying to figure out how to test only the elements within the player's range of motion. (I know how to get the range of motion, I have a good idea of how to write a collisionCheck(playerSprite, targetSprite) function. But how do I know which sprites are currently in the player's vicinity to fetch only them?) Please discuss. Cheers!

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• PCF shadow shader math causing artifacts

  - by user2971069

  For a while now I used PCSS for my shadow technique of choice until I discovered a type of percentage closer filtering. This method creates really smooth shadows and with hopes of improving performance, with only a fraction of texture samples, I tried to implement PCF into my shader. This is the relevant code: float c0, c1, c2, c3; float f = blurFactor; float2 coord = ProjectedTexCoords; if (receiverDistance - tex2D(lightSampler, coord + float2(0, 0)).x > 0.0007) c0 = 1; if (receiverDistance - tex2D(lightSampler, coord + float2(f, 0)).x > 0.0007) c1 = 1; if (receiverDistance - tex2D(lightSampler, coord + float2(0, f)).x > 0.0007) c2 = 1; if (receiverDistance - tex2D(lightSampler, coord + float2(f, f)).x > 0.0007) c3 = 1; coord = (coord % f) / f; return 1 - (c0 * (1 - coord.x) * (1 - coord.y) + c1 * coord.x * (1 - coord.y) + c2 * (1 - coord.x) * coord.y + c3 * coord.x * coord.y); This is a very basic implementation. blurFactor is initialized with 1 / LightTextureSize. So the if statements fetch the occlusion values for the four adjacent texels. I now want to weight each value based on the actual position of the texture coordinate. If it's near the bottom-right pixel, that occlusion value should be preferred. The weighting itself is done with a simple bilinear interpolation function, however this function takes a 2d vector in the range [0..1] so I have to convert my texture coordinate to get the distance from my first pixel to the second one in range [0..1]. For that I used the mod operator to get it into [0..f] range and then divided by f. This code makes sense to me, and for specific blurFactors it works, producing really smooth one pixel wide shadows, but not for all blurFactors. Initially blurFactor is (1 / LightTextureSize) to sample the 4 adjacent texels. I now want to increase the blurFactor by factor x to get a smooth interpolation across maybe 4 or so pixels. But that is when weird artifacts show up. Here is an image: Using a 1x on blurFactor produces a good result, 0.5 is as expected not so smooth. 2x however doesn't work at all. I found that only a factor of 1/2^n produces an good result, every other factor produces artifacts. I'm pretty sure the error lies here: coord = (coord % f) / f; Maybe the modulo is not calculated correctly? I have no idea how to fix that. Is it even possible for pixel that are further than 1 pixel away?

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• If I use my own normal values, should I turn off winding order culling?

  - by Phil

  I've discovered that I managed to program a series of boxes with indexed vertices in such a way that every other triangle (Half of each face) has a backwards winding order. As a result, XNA is culling half of them. However, my Vertex objects contain normal data that I have explicitly set, and I am going to implement my own backface culling shortly to reduce the size of the VertexBuffer. Should I turn off winding order culling and manage it myself, or should I make sure the winding order is consistent and let XNA handle it?

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• Corona SDK: Animation takes a long time to play after "prepare" step

  - by Michael Taufen

  First off, I'm using the current publicly available build, version 2011.704 I'm building a platformer, and have a character that runs along and jumps when the screen is tapped. While jumping, the animation code has him assume a svelte jumping pose, and upon the detection of a collision with the ground, he returns to running. All of this happens. The problem is that there is this strange gap of time, about 1/2 a second by the feel of it, where my character sits on the first frame of the run animation after landing, before it actually starts playing. This leads me to believe that the problem is somewhere between the "prepare" step of loading up a sprite set's animation sequence and the "play" step. Thanks in advance for any help :). My code for when my character lands is as follows: local function collisionHandler ( event ) if (event.object1.myName == "character") and (event.object2.type == "terrain") then inAir = false characterInstance:prepare( "run" ) -- TODO: time between prepare and play is curiously long... characterInstance:play() end end

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• Trying to setup first DirectX project (don't understand the error) [on hold]

  - by user1157885

  I've just started learning DirectX with the book "3D Game Programming with DirectX". I just finished setting up all the paths and adding the code to the project which I think I did correctly, but I get this massive error which I don't really understand and is hard to google. Could someone tell me what it means and how to fix it? Error 1 error TRK0002: Failed to execute command: ""C:\Program Files (x86)\Microsoft DirectX SDK (June 2010)\Utilities\bin\x64\fxc.exe" /nologo /Emain /Fo "C:\Desktop\DirectX 11 Projects\box\Win32Project2\Debug\color.cso" /Od /Zi "....\Book Files\3DGameProg\DVD\Code\Chapter 6 Drawing in Direct3D\Box\FX\color.fx"". The handle is invalid.

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• How do I make my rain effect look more like rain and less like snowfall?

  - by Nikhil Lamba

  I am making a game in that game I want a rain effect. I am little bit far from this right now. I am creating the rain effect like below: particleSystem.addParticleInitializer(new ColorInitializer(1, 1, 1)); particleSystem.addParticleInitializer(new AlphaInitializer(0)); particleSystem.setBlendFunction(GL10.GL_SRC_ALPHA, GL10.GL_ONE); particleSystem.addParticleInitializer(new VelocityInitializer(2, 2, 20, 10)); particleSystem.addParticleInitializer(new RotationInitializer(0.0f, 30.0f)); particleSystem.addParticleModifier(new ScaleModifier(1.0f, 2.0f, 0, 150)); particleSystem.addParticleModifier(new ColorModifier(1, 1, 1, 1f, 1, 1, 1, 3)); particleSystem.addParticleModifier(new ColorModifier(1, 1, 1f, 1, 1, 1, 1, 6)); particleSystem.addParticleModifier(new AlphaModifier(0, 1, 0, 3)); particleSystem.addParticleModifier(new AlphaModifier(1, 0, 1, 125)); particleSystem.addParticleModifier(new ExpireModifier(50, 50)); scene.attachChild(particleSystem); But it looks like snowfall! What changes can I do for it to look more like rain? EDIT Here is a screenshot:

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• how to link a c++ object to a local variable in Lua

  - by MahanGM

  I'm completing my scripting interface with Lua, but recently I've stuck at some point. I have several functions for my Entitiy events like Update(). I have a function called create_entitiy() which instantiate a new entity from a given entity index: function Update() local bullet = create_entity(0, 0, "obj_bullet") end create_entity returns a table which is the properties of the created entity. Now how can I make a connection between bullet variable and my newly created object? Right now for previously added objects to the scene, I simply set a global table for each of them and then after every call to Update(), I go through registered names to find object tables and perform new changes. Like the one below: function Update() if keyboard_key_press(vk_right) then obj_player.x += 3 end I can get obj_player table because I know its name from C++, plus I can get it as a global table and simply reach for the first instance named obj_player. Is there any solution for me to make bullet variable act like this? I was thinking to get all local variables in Update() function and check for every one to see if is it table and it has an unique field attached to it like id, this way I can determine that this is an object table and do the rest of the process. By the way, is this interface going to work easier with luaBind if I implement it? Bottom line: How can I make a local variable in Lua that receives a table from create_entity function and track that local variable to capture it from C++. e. g. function Update() local bullet = create_entity(0, 0, "obj_bullet") bullet.x = 10 <== Commit a change in table end Now I want to get variable bullet from C++. And it's not just this variable, there might be a ton of these local variables with different names.

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