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• What is controlling the desktop display?

  - by Bart Silverstrim

  I have two Ubuntu systems and in the course of changing configurations something has become muddled. I have disabled Unity in favor of gnome shell, the older style display of the desktop. Then I installed xfce 4. Seemed everything would be working okay, and for the most part it does. Except I noticed that on one system there's something else controlling settings. On one, if I right click the desktop, I get the menu with the options: open in new window create launcher... create url link... create folder... create from template -> open terminal here paste desktop settings... properties... applications -> On system two, right clicking brings up the menu: Create new folder Create new document -> organize desktop by name keep aligned paste Change Desktop Background Additionally, even though I set the background with the xfce settings manager, on system two that background will appear for a few seconds before it's replaced by something that looks like a background from Ubuntu's original desktop. And it's being controlled by what comes up with the "change desktop background" when right clicking, which isn't the xfce settings manager. On the first system, that right click does bring up the xfce settings tool. In short, something is controlling/overriding the xfce settings on machine two, but I can't find what file or configuration tool is doing it. How can I get system two to behave as system one, giving control of settings and configuration of X to XFCE's tools?

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• Writing a job requirement for a web application developer

  - by Raul Agrait

  I'm currently writing a job requirement for a software engineer position for my company, in which we are looking for a developer to work on client-side web application work. How should I title the job title / position? I don't necessarily want to call it a "Web Developer", for fear that it might attract more designer-y types. On the other hand, "Software Engineer" doesn't really give the indication that the work, while application based, will be web-based. Is "Web Application Software Engineer" a valid position title? Also, I'm somewhat torn on what the required skills set should be. I don't necessarily think that the ideal candidate should have x years of experience in say, JavaScript or ActionScript, but rather am just looking for someone who has experience in developing client-side applications, and is willing to learn and develop web applications. My current attempt at this, is that I have a section in which I state: Experience in the following frameworks and technologies are a plus, but not necessarily required for the position:

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• Skewed: a rotating camera in a simple CPU-based voxel raycaster/raytracer

  - by voxelizr

  TL;DR -- in my first simple software voxel raycaster, I cannot get camera rotations to work, seemingly correct matrices notwithstanding. The result is skewed: like a flat rendering, correctly rotated, however distorted and without depth. (While axis-aligned ie. unrotated, depth and parallax are as expected.) I'm trying to write a simple voxel raycaster as a learning exercise. This is purely CPU based for now until I figure out how things work exactly -- fow now, OpenGL is just (ab)used to blit the generated bitmap to the screen as often as possible. Now I have gotten to the point where a perspective-projection camera can move through the world and I can render (mostly, minus some artifacts that need investigation) perspective-correct 3-dimensional views of the "world", which is basically empty but contains a voxel cube of the Stanford Bunny. So I have a camera that I can move up and down, strafe left and right and "walk forward/backward" -- all axis-aligned so far, no camera rotations. Herein lies my problem. Screenshot #1: correct depth when the camera is still strictly axis-aligned, ie. un-rotated. Now I have for a few days been trying to get rotation to work. The basic logic and theory behind matrices and 3D rotations, in theory, is very clear to me. Yet I have only ever achieved a "2.5 rendering" when the camera rotates... fish-eyey, bit like in Google Streetview: even though I have a volumetric world representation, it seems --no matter what I try-- like I would first create a rendering from the "front view", then rotate that flat rendering according to camera rotation. Needless to say, I'm by now aware that rotating rays is not particularly necessary and error-prone. Still, in my most recent setup, with the most simplified raycast ray-position-and-direction algorithm possible, my rotation still produces the same fish-eyey flat-render-rotated style looks: Screenshot #2: camera "rotated to the right by 39 degrees" -- note how the blue-shaded left-hand side of the cube from screen #2 is not visible in this rotation, yet by now "it really should"! Now of course I'm aware of this: in a simple axis-aligned-no-rotation-setup like I had in the beginning, the ray simply traverses in small steps the positive z-direction, diverging to the left or right and top or bottom only depending on pixel position and projection matrix. As I "rotate the camera to the right or left" -- ie I rotate it around the Y-axis -- those very steps should be simply transformed by the proper rotation matrix, right? So for forward-traversal the Z-step gets a bit smaller the more the cam rotates, offset by an "increase" in the X-step. Yet for the pixel-position-based horizontal+vertical-divergence, increasing fractions of the x-step need to be "added" to the z-step. Somehow, none of my many matrices that I experimented with, nor my experiments with matrix-less hardcoded verbose sin/cos calculations really get this part right. Here's my basic per-ray pre-traversal algorithm -- syntax in Go, but take it as pseudocode: fx and fy: pixel positions x and y rayPos: vec3 for the ray starting position in world-space (calculated as below) rayDir: vec3 for the xyz-steps to be added to rayPos in each step during ray traversal rayStep: a temporary vec3 camPos: vec3 for the camera position in world space camRad: vec3 for camera rotation in radians pmat: typical perspective projection matrix The algorithm / pseudocode: // 1: rayPos is for now "this pixel, as a vector on the view plane in 3d, at The Origin" rayPos.X, rayPos.Y, rayPos.Z = ((fx / width) - 0.5), ((fy / height) - 0.5), 0 // 2: rotate around Y axis depending on cam rotation. No prob since view plane still at Origin 0,0,0 rayPos.MultMat(num.NewDmat4RotationY(camRad.Y)) // 3: a temp vec3. planeDist is -0.15 or some such -- fov-based dist of view plane from eye and also the non-normalized, "in axis-aligned world" traversal step size "forward into the screen" rayStep.X, rayStep.Y, rayStep.Z = 0, 0, planeDist // 4: rotate this too -- 0,zstep should become some meaningful xzstep,xzstep rayStep.MultMat(num.NewDmat4RotationY(CamRad.Y)) // set up direction vector from still-origin-based-ray-position-off-rotated-view-plane plus rotated-zstep-vector rayDir.X, rayDir.Y, rayDir.Z = -rayPos.X - me.rayStep.X, -rayPos.Y, rayPos.Z + rayStep.Z // perspective projection rayDir.Normalize() rayDir.MultMat(pmat) // before traversal, the ray starting position has to be transformed from origin-relative to campos-relative rayPos.Add(camPos) I'm skipping the traversal and sampling parts -- as per screens #1 through #3, those are "basically mostly correct" (though not pretty) -- when axis-aligned / unrotated.

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• Interpolate air drag for my game?

  - by Valentin Krummenacher

  So I have a little game which works with small steps, however those steps vary in time, so for example I sometimes have 10 Steps/second and then I have 20 Steps/second. This changes automatically depending on how many steps the user's computer can take. To avoid inaccurate positioning of the game's player object I use y=v0*dt+g*dt^2/2 to determine my objects y-position, where dt is the time since the last step, v0 is the velocity of my object in the beginning of my step and g is the gravity. To calculate the velocity in the end of a step I use v=v0+g*dt what also gives me correct results, independent of whether I use 2 steps with a dt of for example 20ms or one step with a dt of 40ms. Now I would like to introduce air drag. For simplicity's sake I use a=k*v^2 where a is the air drag's acceleration (I am aware that it would usually result in a force, but since I assume 1kg for my object's mass the force is the same as the resulting acceleration), k is a constant (in this case I'm using 0.001) and v is the speed. Now in an infinitely small time interval a is k multiplied by the velocity in this small time interval powered by 2. The problem is that v in the next time interval would depend on the drag of the last which again depends on the v of the last interval and so on... In other words: If I use a=k*v^2 I get different results for my position/velocity when I use 2 steps of 20ms than when I use one step of 40ms. I used to have this problem for my position too, but adding +g*dt^2/2 to the formula for my position fixed the problem since it takes into account that the position depends on the velocity which changes slightly in every infinitely small time interval. Does something like that exist for air drag too? And no, I dont mean anything like Adding air drag to a golf ball trajectory equation or similar, for that kind of method only gives correct results when all my steps are the same. (I hope you can understand my intermediate english, it's not my main language so I would like to say sorry for all the silly mistakes I might have made in my question)

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• Game Maker Studio Gravity Problems

  - by Dusty

  I've started messing around with Game Maker Studio. The problem I'm having is trying to get a gravity code for orbiting. Here's how i did it in XNA foreach (GravItem Item in StarSystem.ActiveItems.OfType<GravItem>()) { if (this != Item) { Velocity += (10 * Vector2.Normalize(Item.Position - this.Position * (this.Mass * Item.Mass) / (Vector2.DistanceSquared(this.Position, Item.Position)) / (this.Mass)); } } Simple and works well, things or bit and everything is nice. but in Game maker i don't have the luxury of Vector2's or a For-each loop to loop threw all the objects that have a mass. I've tried a few different things but nothing seems to work distance = distance_to_object(obj_moon); //--Gravity hspeed += (0.5 * (distance) * (Mass * obj_moon.Mass) / (sqr(distance)) / Mass) vspeed += (0.5 * (distance) * (Mass * obj_moon.Mass) / (sqr(distance)) / Mass) thanks for the help

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• Mark Zuckerberg tops the list of 50 Highest Rated CEOs. 3 Indian CEOs feature in the list.

  - by Gopinath

  Mark Zuckerberg, the CEO of Facebook is rated as the best CEO according to a report released by the popular employee reviews website Glassdoor.com. 50,000 employees reviews submitted to Glassdoor in the past 1 year are considered for preparing the rating list and Zukerberg topped the list with 99 percent approval to the question “Do you approve of the way your CEO is leading the company?”. Wow! That’s an amazing support to Zukergerg from his employees though stock market and share holders are not with him. Coincidently Facebook is also rated as the best company to work by Glassdoor in a recent survey. Here is the list of top 10 CEOs Mark Zuckerberg, Facebook; 99.3% Approval Bill McDermott & Jim Hagemann Snabe, SAP; 99% Approval Dominic Barton, McKinsey & Company; 97% Approval Jim Turley, Ernst & Young; 96% Approval John E. Schlifske, Northwestern Mutual; 96% Approval Frank D’Souza, Cognizant Technology Solutions; 96% Approval Joe Tucci, EMC; 96% Approval Paul E. Jacobs, QUALCOMM; 95% Approval Richard K. Davis, U.S. Bank; 95% Approval Pierre Nanterme, Accenture; 95% Approval 3 Indian CEOs in the top 50 list – TCS, Wipro & MindTree The list featured three Indian CEOs and all the three are leading Software IT Services organizations in India and creating thousands of IT jobs.  Natarajan Chandrasekaran – the CEO of TCS is at 25th position, Krishnakumar Natarajan – the CEO of MindTree is at 28th position and  Wipro’s T.K.Kurien is at 44th position. Glad to see Indian CEO joining the global ranks. Tech Heavy Weights Google, Apple, Amazon & Microsoft aren’t in top 10 Another thing to note from this report is that the CEO’s of technology heavy weights Google, Apple, Amazon and Microsoft are not in the top10 list- looks like their employees are not really happy with their bosses. At least not as happy as their peers at Facebook. Google CEO’s Larry Page is at 11th position, Jeff Bezos of Amazon at 16th position and Tim Cook of Apple is at 18th position. Well the Microsoft CEO is not even in the list of top 50!! You can read the complete list of ratings at Glassdoor.com’s blog. Photo Credit: Andrew Feinberg

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• Direction of the bullet - how to have something else than left, right, top, bottom

  - by Florian Margaine

  I'm making a simple shooter game using canvas and javascript. The current code can be seen here. To know which way I want the bullet to be shot, I simply have a direction property that can have 4 values (left, right, bottom, top), and I can then calculate the next position of the bullet easily. However, I'd like to move the bullet to the mouse position, but I don't really see how to do this. How do I calculate the next position? I'm guessing there is some formula to calculate the line between two positions (the player's and the mouse's), but I don't have much idea yet. So there is no obstacle, but I don't see how to calculate this, and be able have the next position of the bullet at each frame.

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• Use alpha or opacity on a table row using CSS [migrated]

  - by mserin

  I have a CSS stylesheet for a webpage. The webpage has a table with a background color of white (set in the rows, not the table). I would like to set the opacity or alpha to 50%. I have tried so many variations, but come up with no luck. A typical row in the HTML file is: <tr> <td>&nbsp;</td> <td>Twitter</td> </tr> The CSS settings for table rows (which works perfectly) is: tr { font-family: Arial, Helvetica, sans-serif; background:rgb(255,255,255); } To get the alpha, I tried tr { font-family: Arial, Helvetica, sans-serif; background-color:rgba(255,255,255,0.5); } I have also tried background-color-opacity: 0.5; Any other suggestions?

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• Use Your Favorite Wallpapers in Windows 7 Starter Edition

  - by Asian Angel

  If you have Windows 7 Starter Edition installed on your netbook, the default wallpaper can get old. If you are tired of looking at the default wallpaper, then join us today as we look at changing it with Oceanis Change Background Windows 7. Special Notes This information is quoted directly from the website and needs to be kept in mind when using Oceanis Change Background Windows 7: If the Oceanis Change Background Windows 7 program no longer works properly after installing some Windows Updates, then uninstall and reinstall the Oceanis Change Background Windows 7 program to have it run properly again. If you ever do an in-place upgrade to another higher level edition of Windows 7 in the future, then be sure to uninstall this Oceanis Change Background Windows 7 program first to avoid incompatibility issues with it in the new edition of Windows 7. It was designed to only work in Windows 7 Starter edition. Before There it is…the default wallpaper everyone with the Starter Edition gets stuck with. Some people may not mind it, but if you are one of the people who really wants something different then get ready to rejoice. After The install file for Oceanis is contained in a zip file so you will need to unzip it to get started. The install process is quick and simple but you will need to do a system restart afterwards. Once you have restarted your computer this is what your screen will look like…do not panic and think that this is all there is to it. This is just the Starter Screen and can be easily changed… Note: Oceanis will auto-start with Windows each time. Using either the Desktop Icon or the Start Menu Entry, open up the Oceanis Main Window. You will see the set of four default wallpapers shown here. At this point the best thing to do is browse for the appropriate folder where you have all of those wonderful new wallpapers just waiting to be used. Note: We found Stretch to be the best Picture Position setting on our system. For our example we had three ready and waiting. We decided to try out the Wallpaper Slideshow feature first. We chose a time frame and saved our changes. Here are our three wallpapers as they switched through. This can be much more interesting than the default wallpaper. There was only one quirk that we encountered while using the Slideshow Setting. On occasion if we minimized a non-maximized window there would be a leftover partial image in place of the window. Our suggestion? Go with one wallpaper at a time and the settings shown below. These are the settings that we had terrific luck with…Only one picture selected, Picture Position = Stretch, & Change Picture Every = Every Day. Using these settings, the Starter Edition acted just like any of the other editions with regard to wallpaper management. Conclusion If you have grown tired of looking at the default wallpaper in Windows 7 Starter Edition then you will certainly appreciate what Oceanis Change Background Windows 7 can do to fix that problem. For more ways to customize your Windows 7 Started Edition, be sure to to check out how to personalize Windows 7 Starter. Links Download Oceanis Change Background Windows 7 Similar Articles Productive Geek Tips Windows 7 Welcome Screen Taking Forever? Here’s the Fix (Maybe)Awesome Desktop Wallpapers: The Windows 7 EditionHow To Customize Wallpaper in Windows 7 Starter EditionDesktop Fun: Starship Theme WallpapersDesktop Fun: Underwater Theme Wallpapers TouchFreeze Alternative in AutoHotkey The Icy Undertow Desktop Windows Home Server – Backup to LAN The Clear & Clean Desktop Use This Bookmarklet to Easily Get Albums Use AutoHotkey to Assign a Hotkey to a Specific Window Latest Software Reviews Tinyhacker Random Tips Acronis Online Backup DVDFab 6 Revo Uninstaller Pro Registry Mechanic 9 for Windows Vista style sidebar for Windows 7 Create Nice Charts With These Web Based Tools Track Daily Goals With 42Goals Video Toolbox is a Superb Online Video Editor Fun with 47 charts and graphs Tomorrow is Mother’s Day

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• extrapolating object state based on updates

  - by user494461

  I have a networked multi-user collaborative application. To maintain a consistent virtual world, I send updates for objects from a master peer to a guest peer. The update state contains x,y,z coordinates of object center and his rotation matrix(CHAI3d api used a 3x3 matrix) with 30Hz frequency. I want to reduce this update rate and want to send with a reduced update rate. I want a predictor on both peers. When the predicted value is outside, say a error value of 10% in comparison to master peers objects original state the master peer triggers a state update. Now for position I used velocity,position updates so that the guest peer can extrapolate position. Like velocity for position what parameter should I use for rotation extrapolition?

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• How to emulate pressing the Close button from a script?

  - by Karthik

  I wanted Thunderbird to stay in the Background to notify me of incoming mails. After a bit of searching, I found this post. How to keep Thunderbird and Pidgin running on background? The solution is to install an addon so that when we close Thunderbird it just stays in the background. Now, to have thunderbird running at Start up we can just add it to Startup Applications. But, when I open my system, Thunderbird also gets opened and I have to manually press the close button everytime to make Thunderbird go into the background. The solution given in the above post for this problem is to select Minimize on start. But doing so affects the way in which Thunderbird works when invoked from the Messaging menu. So I deselected this option. But, if there is a way to emulate pressing the Close button from a script, I can just add that script to Startup Applications So is there a way to achieve this? Note : If there is a simpler way to solve my original problem of keeping Thunderbird in background please post that also. Many thanks.

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• Improve mouse movement in First person game

  - by brainydexter

  In my current FPS game, I have the mouse setup in a way, that it always forces the position of the mouse to be centered at the screen. This gets the job done, but also gets very annoying, since the mouse is "fixed" at the center of the screen. Here is what I am doing: get mouse current position find offset from center of the screen set mouse current position to center of the screen apply difference to m_pTransformation (transformation matrix of the player) Is there a better way to deal with this ?

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• xna orbit camera troubles

  - by user17753

  I have a Model named cube to which I load in LoadContent(): cube = Content.Load<Model>("untitled");. In the Draw Method I call DrawModel: private void DrawModel(Model m, Matrix world) { foreach (ModelMesh mesh in m.Meshes) { foreach (BasicEffect effect in mesh.Effects) { effect.EnableDefaultLighting(); effect.View = camera.View; effect.Projection = camera.Projection; effect.World = world; } mesh.Draw(); } } camera is of the Camera type, a class I've setup. Right now it is instantiated in the initialization section with the graphics aspect ratio and the translation (world) vector of the model, and the Draw loop calls the camera.UpdateCamera(); before drawing the models. class Camera { #region Fields private Matrix view; // View Matrix for Camera private Matrix projection; // Projection Matrix for Camera private Vector3 position; // Position of Camera private Vector3 target; // Point camera is "aimed" at private float aspectRatio; //Aspect Ratio for projection private float speed; //Speed of camera private Vector3 camup = Vector3.Up; #endregion #region Accessors /// <summary> /// View Matrix of the Camera -- Read Only /// </summary> public Matrix View { get { return view; } } /// <summary> /// Projection Matrix of the Camera -- Read Only /// </summary> public Matrix Projection { get { return projection; } } #endregion /// <summary> /// Creates a new Camera. /// </summary> /// <param name="AspectRatio">Aspect Ratio to use for the projection.</param> /// <param name="Position">Target coord to aim camera at.</param> public Camera(float AspectRatio, Vector3 Target) { target = Target; aspectRatio = AspectRatio; ResetCamera(); } private void Rotate(Vector3 Axis, float Amount) { position = Vector3.Transform(position - target, Matrix.CreateFromAxisAngle(Axis, Amount)) + target; } /// <summary> /// Resets Default Values of the Camera /// </summary> private void ResetCamera() { speed = 0.05f; position = target + new Vector3(0f, 20f, 20f); projection = Matrix.CreatePerspectiveFieldOfView(MathHelper.PiOver4, aspectRatio, 0.5f, 100f); CalculateViewMatrix(); } /// <summary> /// Updates the Camera. Should be first thing done in Draw loop /// </summary> public void UpdateCamera() { Rotate(Vector3.Right, speed); CalculateViewMatrix(); } /// <summary> /// Calculates the View Matrix for the camera /// </summary> private void CalculateViewMatrix() { view = Matrix.CreateLookAt(position,target, camup); } I'm trying to create the camera so that it can orbit the center of the model. For a test I am calling Rotate(Vector3.Right, speed); but it rotates almost right but gets to a point where it "flips." If I rotate along a different axis Rotate(Vector3.Up, speed); everything seems OK in that direction. So I guess, can someone tell me what I'm not accounting for in the above code I wrote? Or point me to an example of an orbiting camera that can be fixed on an arbitrary point?

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• How to create array with unique sprites? in cocos2d iphone

  - by prakash s

  I write the code like this. This displays only one sprite (red colour bubble) with number of times and moving down, but actually I want to display different sprites (different colour bubble) every time and moving down. I also add no of .png images in resource folder of my project. Here I used only 3.png, but I need to display all *.png images (different colour bubbles) in my project but I don't know how to get this. Please help me Thank you. Here is the code: -(void)addTarget { CCSprite *target = [CCSprite spriteWithFile:@"3.png" rect:CGRectMake(0, 0, 256, 256)]; CGSize winSize = [[CCDirector sharedDirector] winSize]; int minY = target.contentSize.height/2; int maxY = winSize.height - target.contentSize.height/2; int rangeY = maxY - minY; int actualY = (arc4random() % rangeY) + minY; // Create the target slightly off-screen along the right edge, // and along a random position along the Y axis as calculated above target.position = ccp(winSize.width + (target.contentSize.width/2), actualY); [self addChild:target]; // Determine speed of the target int minDuration = 4.0; int maxDuration = 12.0; int rangeDuration = maxDuration - minDuration; int actualDuration = (arc4random() % rangeDuration) + minDuration; // Create the actions id actionMove = [CCMoveTo actionWithDuration:actualDuration position:ccp(-target.contentSize.width/2,actualY)]; id actionMoveDone = [CCCallFuncN actionWithTarget:self selector:@selector(spriteMoveFinished:)]; [target runAction:[CCSequence actions:actionMove, actionMoveDone, nil]]; // Add to targets array target.tag = 2; [_targets addObject:target]; } -(void)gameLogic:(ccTime)dt { [self addTarget]; } -(id) init { if( (self=[super initWithColor:ccc4(255,255,255,255)] )) { // Enable touch events self.isTouchEnabled = YES; // Initialize arrays _targets = [[NSMutableArray alloc] init]; _projectiles = [[NSMutableArray alloc] init]; // Get the dimensions of the window for calculation purposes CGSize winSize = [[CCDirector sharedDirector] winSize]; [self schedule:@selector(gameLogic:) interval:1.0]; [self schedule:@selector(update:)]; } return self; } - (void)update:(ccTime)dt { NSMutableArray *projectilesToDelete = [[NSMutableArray alloc] init]; for (CCSprite *projectile in _projectiles) { CGRect projectileRect = CGRectMake(projectile.position.x - (projectile.contentSize.width/2), projectile.position.y - (projectile.contentSize.height/2), projectile.contentSize.width, projectile.contentSize.height); NSMutableArray *targetsToDelete = [[NSMutableArray alloc] init]; for (CCSprite *target in _targets) { CGRect targetRect = CGRectMake(target.position.x - (target.contentSize.width/2), target.position.y - (target.contentSize.height/2), target.contentSize.width, target.contentSize.height); if (CGRectIntersectsRect(projectileRect, targetRect)) { [targetsToDelete addObject:target]; } } for (CCSprite *target in targetsToDelete) { [_targets removeObject:target]; [self removeChild:target cleanup:YES]; _projectilesDestroyed++; if (_projectilesDestroyed > 30) { //GameOverScene *gameOverScene = [GameOverScene node]; // [gameOverScene.layer.label setString:@"You Win!"]; // [[CCDirector sharedDirector] replaceScene:gameOverScene]; } } if (targetsToDelete.count > 0) { [projectilesToDelete addObject:projectile]; } [targetsToDelete release]; } for (CCSprite *projectile in projectilesToDelete) { [_projectiles removeObject:projectile]; [self removeChild:projectile cleanup:YES]; } [projectilesToDelete release]; }

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• Consuming the Amazon S3 service from a Win8 Metro Application

  - by cibrax

  As many of the existing Http APIs for Cloud Services, AWS also provides a set of different platform SDKs for hiding many of complexities present in the APIs. While there is a platform SDK for .NET, which is open source and available in C#, that SDK does not work in Win8 Metro Applications for the changes introduced in WinRT. WinRT offers a complete different set of APIs for doing I/O operations such as doing http calls or using cryptography for signing or encrypting data, two aspects that are absolutely necessary for consuming AWS. All the I/O APIs available as part of WinRT are asynchronous, and uses the TPL model for .NET applications (HTML and JavaScript Metro applications use a model based in promises, which is similar concept).  In the case of S3, the http Authorization header is used for two purposes, authenticating clients and make sure the messages were not altered while they were in transit. For doing that, it uses a signature or hash of the message content and some of the headers using a symmetric key (That's just one of the available mechanisms). Windows Azure for example also uses the same mechanism in many of its APIs. There are three challenges that any developer working for first time in Metro will have to face to consume S3, the new WinRT APIs, the asynchronous nature of them and the complexity introduced for generating the Authorization header. Having said that, I decided to write this post with some of the gotchas I found myself trying to consume this Amazon service. 1. Generating the signature for the Authorization header All the cryptography APIs in WinRT are available under Windows.Security.Cryptography namespace. Many of operations available in these APIs uses the concept of buffers (IBuffer) for representing a chunk of binary data. As you will see in the example below, these buffers are mainly generated with the use of static methods in a WinRT class CryptographicBuffer available as part of the namespace previously mentioned. private string DeriveAuthToken(string resource, string httpMethod, string timestamp) { var stringToSign = string.Format("{0}\n" + "\n" + "\n" + "\n" + "x-amz-date:{1}\n" + "/{2}/", httpMethod, timestamp, resource); var algorithm = MacAlgorithmProvider.OpenAlgorithm("HMAC_SHA1"); var keyMaterial = CryptographicBuffer.CreateFromByteArray(Encoding.UTF8.GetBytes(this.secret)); var hmacKey = algorithm.CreateKey(keyMaterial); var signature = CryptographicEngine.Sign( hmacKey, CryptographicBuffer.CreateFromByteArray(Encoding.UTF8.GetBytes(stringToSign)) ); return CryptographicBuffer.EncodeToBase64String(signature); } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } The algorithm that determines the information or content you need to use for generating the signature is very well described as part of the AWS documentation. In this case, this method is generating a signature required for creating a new bucket. A HmacSha1 hash is computed using a secret or symetric key provided by AWS in the management console. 2. Sending an Http Request to the S3 service WinRT also ships with the System.Net.Http.HttpClient that was first introduced some months ago with ASP.NET Web API. This client provides a rich interface on top the traditional WebHttpRequest class, and also solves some of limitations found in this last one. There are a few things that don't work with a raw WebHttpRequest such as setting the Host header, which is something absolutely required for consuming S3. Also, HttpClient is more friendly for doing unit tests, as it receives a HttpMessageHandler as part of the constructor that can fake to emulate a real http call. This is how the code for consuming the service with HttpClient looks like, public async Task<S3Response> CreateBucket(string name, string region = null, params string[] acl) { var timestamp = string.Format("{0:r}", DateTime.UtcNow); var auth = DeriveAuthToken(name, "PUT", timestamp); var request = new HttpRequestMessage(HttpMethod.Put, "http://s3.amazonaws.com/"); request.Headers.Host = string.Format("{0}.s3.amazonaws.com", name); request.Headers.TryAddWithoutValidation("Authorization", "AWS " + this.key + ":" + auth); request.Headers.Add("x-amz-date", timestamp); var client = new HttpClient(); var response = await client.SendAsync(request); return new S3Response { Succeed = response.StatusCode == HttpStatusCode.OK, Message = (response.Content != null) ? await response.Content.ReadAsStringAsync() : null }; } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } You will notice a few additional things in this code. By default, HttpClient validates the values for some well-know headers, and Authorization is one of them. It won't allow you to set a value with ":" on it, which is something that S3 expects. However, that's not a problem at all, as you can skip the validation by using the TryAddWithoutValidation method. Also, the code is heavily relying on the new async and await keywords to transform all the asynchronous calls into synchronous ones. In case you would want to unit test this code and faking the call to the real S3 service, you should have to modify it to inject a custom HttpMessageHandler into the HttpClient. The following implementation illustrates this concept, In case you would want to unit test this code and faking the call to the real S3 service, you should have to modify it to inject a custom HttpMessageHandler into the HttpClient. The following implementation illustrates this concept, public class FakeHttpMessageHandler : HttpMessageHandler { HttpResponseMessage response; public FakeHttpMessageHandler(HttpResponseMessage response) { this.response = response; } protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, System.Threading.CancellationToken cancellationToken) { var tcs = new TaskCompletionSource<HttpResponseMessage>(); tcs.SetResult(response); return tcs.Task; } } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } You can use this handler for injecting any response while you are unit testing the code.

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• Consuming the Amazon S3 service from a Win8 Metro Application

  - by cibrax

  As many of the existing Http APIs for Cloud Services, AWS also provides a set of different platform SDKs for hiding many of complexities present in the APIs. While there is a platform SDK for .NET, which is open source and available in C#, that SDK does not work in Win8 Metro Applications for the changes introduced in WinRT. WinRT offers a complete different set of APIs for doing I/O operations such as doing http calls or using cryptography for signing or encrypting data, two aspects that are absolutely necessary for consuming AWS. All the I/O APIs available as part of WinRT are asynchronous, and uses the TPL model for .NET applications (HTML and JavaScript Metro applications use a model based in promises, which is similar concept).  In the case of S3, the http Authorization header is used for two purposes, authenticating clients and make sure the messages were not altered while they were in transit. For doing that, it uses a signature or hash of the message content and some of the headers using a symmetric key (That's just one of the available mechanisms). Windows Azure for example also uses the same mechanism in many of its APIs. There are three challenges that any developer working for first time in Metro will have to face to consume S3, the new WinRT APIs, the asynchronous nature of them and the complexity introduced for generating the Authorization header. Having said that, I decided to write this post with some of the gotchas I found myself trying to consume this Amazon service. 1. Generating the signature for the Authorization header All the cryptography APIs in WinRT are available under Windows.Security.Cryptography namespace. Many of operations available in these APIs uses the concept of buffers (IBuffer) for representing a chunk of binary data. As you will see in the example below, these buffers are mainly generated with the use of static methods in a WinRT class CryptographicBuffer available as part of the namespace previously mentioned. private string DeriveAuthToken(string resource, string httpMethod, string timestamp) { var stringToSign = string.Format("{0}\n" + "\n" + "\n" + "\n" + "x-amz-date:{1}\n" + "/{2}/", httpMethod, timestamp, resource); var algorithm = MacAlgorithmProvider.OpenAlgorithm("HMAC_SHA1"); var keyMaterial = CryptographicBuffer.CreateFromByteArray(Encoding.UTF8.GetBytes(this.secret)); var hmacKey = algorithm.CreateKey(keyMaterial); var signature = CryptographicEngine.Sign( hmacKey, CryptographicBuffer.CreateFromByteArray(Encoding.UTF8.GetBytes(stringToSign)) ); return CryptographicBuffer.EncodeToBase64String(signature); } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } The algorithm that determines the information or content you need to use for generating the signature is very well described as part of the AWS documentation. In this case, this method is generating a signature required for creating a new bucket. A HmacSha1 hash is computed using a secret or symetric key provided by AWS in the management console. 2. Sending an Http Request to the S3 service WinRT also ships with the System.Net.Http.HttpClient that was first introduced some months ago with ASP.NET Web API. This client provides a rich interface on top the traditional WebHttpRequest class, and also solves some of limitations found in this last one. There are a few things that don't work with a raw WebHttpRequest such as setting the Host header, which is something absolutely required for consuming S3. Also, HttpClient is more friendly for doing unit tests, as it receives a HttpMessageHandler as part of the constructor that can fake to emulate a real http call. This is how the code for consuming the service with HttpClient looks like, public async Task<S3Response> CreateBucket(string name, string region = null, params string[] acl) { var timestamp = string.Format("{0:r}", DateTime.UtcNow); var auth = DeriveAuthToken(name, "PUT", timestamp); var request = new HttpRequestMessage(HttpMethod.Put, "http://s3.amazonaws.com/"); request.Headers.Host = string.Format("{0}.s3.amazonaws.com", name); request.Headers.TryAddWithoutValidation("Authorization", "AWS " + this.key + ":" + auth); request.Headers.Add("x-amz-date", timestamp); var client = new HttpClient(); var response = await client.SendAsync(request); return new S3Response { Succeed = response.StatusCode == HttpStatusCode.OK, Message = (response.Content != null) ? await response.Content.ReadAsStringAsync() : null }; } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } You will notice a few additional things in this code. By default, HttpClient validates the values for some well-know headers, and Authorization is one of them. It won't allow you to set a value with ":" on it, which is something that S3 expects. However, that's not a problem at all, as you can skip the validation by using the TryAddWithoutValidation method. Also, the code is heavily relying on the new async and await keywords to transform all the asynchronous calls into synchronous ones. In case you would want to unit test this code and faking the call to the real S3 service, you should have to modify it to inject a custom HttpMessageHandler into the HttpClient. The following implementation illustrates this concept, In case you would want to unit test this code and faking the call to the real S3 service, you should have to modify it to inject a custom HttpMessageHandler into the HttpClient. The following implementation illustrates this concept, public class FakeHttpMessageHandler : HttpMessageHandler { HttpResponseMessage response; public FakeHttpMessageHandler(HttpResponseMessage response) { this.response = response; } protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, System.Threading.CancellationToken cancellationToken) { var tcs = new TaskCompletionSource<HttpResponseMessage>(); tcs.SetResult(response); return tcs.Task; } } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } You can use this handler for injecting any response while you are unit testing the code.

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• Quaternion Camera Orbiting around a Sphere

  - by jessejuicer

  Background: I'm trying to create a game where the camera is always rotating around a single sphere. I'm using the DirectX D3DX math functions in C++ on Windows. The Problem: I cannot get both the camera position and orientation both working properly at the same time. Either one works but not both together. Here's the code for my quaternion camera that revolves around a sphere, always looking at the centerpoint of the sphere, ... as far as I understand it (but which isn't working properly): (I'm only going to present rotation around the X axis here, to simplify this post) Whenever the UP key is pressed or held down, the camera should rotate around the X axis, while looking at the centerpoint of the sphere (which is at 0,0,0 in the world). So, I build a quaternion that represents a small angle of rotation around the x axis like this (where 'deltaAngle' is a small enough number for a slow rotation): D3DXVECTOR3 rotAxis; D3DXQUATERNION tempQuat; tempQuat.x = 0.0f; tempQuat.y = 0.0f; tempQuat.z = 0.0f; tempQuat.w = 1.0f; rotAxis.x = 1.0f; rotAxis.y = 0.0f; rotAxis.z = 0.0f; D3DXQuaternionRotationAxis(&tempQuat, &rotAxis, deltaAngle); ...and I accumulate the result into the camera's current orientation quat, like this: D3DXQuaternionMultiply(&cameraOrientationQuat, &cameraOrientationQuat, &tempQuat); ...which all works fine. Now I need to build a view matrix to pass to DirectX SetTransform function. So I build a rotation matrix from the camera orientation quat as follows: D3DXMATRIXA16 rotationMatrix; D3DXMatrixIdentity(&rotationMatrix); D3DXMatrixRotationQuaternion(&rotationMatrix, &cameraOrientationQuat); ...Now (as seen below) if I just transpose that rotationMatrix and plug it into the 3x3 section of the view matrix, then negate the camera's position and plug it into the translation section of the view matrix, the rotation magically works. Perfectly. (even when I add in rotations for all three axes). There's no gimbal lock, just a smooth rotation all around in any direction. BUT- this works even though I never change the camera's position. At all. Which sorta blows my mind. I even display the camera position and can watch it stay constant at it's starting point (0.0, 0.0, -4000.0). It never moves, but the rotation around the sphere is perfect. I don't understand that. For proper view rotation, the camera position should be revolving around the sphere. Here's the rest of building the view matrix (I'll talk about the commented code below). Note that the camera starts out at (0.0, 0.0, -4000.0) and m_camDistToTarget is 4000.0: /* D3DXVECTOR3 vec1; D3DXVECTOR4 vec2; vec1.x = 0.0f; vec1.y = 0.0f; vec1.z = -1.0f; D3DXVec3Transform(&vec2, &vec1, &rotationMatrix); g_cameraActor->pos.x = vec2.x * g_cameraActor->m_camDistToTarget; g_cameraActor->pos.y = vec2.y * g_cameraActor->m_camDistToTarget; g_cameraActor->pos.z = vec2.z * g_cameraActor->m_camDistToTarget; */ D3DXMatrixTranspose(&g_viewMatrix, &rotationMatrix); g_viewMatrix._41 = -g_cameraActor->pos.x; g_viewMatrix._42 = -g_cameraActor->pos.y; g_viewMatrix._43 = -g_cameraActor->pos.z; g_viewMatrix._44 = 1.0f; g_direct3DDevice9->SetTransform( D3DTS_VIEW, &g_viewMatrix ); ...(The world matrix is always an identity, and the perspective projection works fine). ...So, without the commented code being compiled, the rotation works fine. But to be proper, for obvious reasons, the camera position should be rotating around the sphere, which it currently is not. That's what the commented code is supposed to do. And when I add in that chunk of code to do that, and look at all the data as I hold the keys down (using UP, DOWN, LEFT, RIGHT to rotate different directions) all the values look correct! The camera position is rotating around the sphere just fine, and I can watch that happen visually too. The problem is that the camera orientation does not lookat the center of the sphere. It always looks straight forward down the z axis (toward positive z) as it revolves around the sphere. Yet the values of both the rotation matrix and the view matrix seem to be behaving correctly. (The view matrix orientation is the same as the rotation matrix, just transposed). For instance if I just hold down the key to spin around the x axis, I can watch the values of the three axes represented in the view matrix (x, y, and z axes)... view x-axis stays at (1.0, 0.0, 0.0), and view y-axis and z-axis both spin around the x axis just fine. All the numbers are changing as they should be... well, almost. As far as I can tell, the position of the view matrix is spinning around the sphere one direction (like clockwise), and the orientation (the axes in the view matrix) are spinning the opposite direction (like counter-clockwise). Which I guess explains why the orientation appears to stay straight ahead. I know the position is correct. It revolves properly. It's the orientation that's wrong. Can anyone see what am I doing wrong? Am I using these functions incorrectly? Or is my algorithm flawed? As usual I've been combing my code for simple mistakes for many hours. I'm willing to post the actual code, and a video of the behavior, but that will take much more effort. Thought I'd ask this way first.

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• Heightmap in Shader not working

  - by CSharkVisibleBasix

  I'm trying to implement GPU based geometry clipmapping and have problems to apply a simple heightmap to my terrain. For the heightmap I use a simple texture with the surface format "single". I've taken the texture from here. To apply it to my terrain, I use the following shader code: texture Heightmap; sampler2D HeightmapSampler = sampler_state { Texture = <Heightmap>; MinFilter = Point; MagFilter = Point; MipFilter = Point; AddressU = Mirror; AddressV = Mirror; }; Vertex Shader: float4 worldPos = mul(float4(pos.x,0.0f,pos.y, 1.0f), worldMatrix); float elevation = tex2Dlod(HeightmapSampler, float4(worldPos.x, worldPos.z,0,0)); worldPos.y = elevation * 128; The complete vertex shader (also containig clipmapping transforms) looks like this: float4x4 View : View; float4x4 Projection : Projection; float3 CameraPos : CameraPosition; float LODscale; //The LOD ring index 0:highest x:lowest float2 Position; //The position of the part in the world texture Heightmap; sampler2D HeightmapSampler = sampler_state { Texture = <Heightmap>; MinFilter = Point; MagFilter = Point; MipFilter = Point; AddressU = Mirror; AddressV = Mirror; }; //Accept only float2 because we extract 3rd dim out of Heightmap float4 wireframe_VS(float2 pos : POSITION) : POSITION{ float4x4 worldMatrix = float4x4( LODscale, 0, 0, 0, 0, LODscale, 0, 0, 0, 0, LODscale, 0, - Position.x * 64 * LODscale + CameraPos.x, 0, Position.y * 64 * LODscale + CameraPos.z, 1); float4 worldPos = mul(float4(pos.x,0.0f,pos.y, 1.0f), worldMatrix); float elevation = tex2Dlod(HeightmapSampler, float4(worldPos.x, worldPos.z,0,0)); worldPos.y = elevation * 128; float4 viewPos = mul(worldPos, View); float4 projPos = mul(viewPos, Projection); return projPos; }

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• Shadows shimmer when camera moves

  - by Chad Layton

  I've implemented shadow maps in my simple block engine as an exercise. I'm using one directional light and using the view volume to create the shadow matrices. I'm experiencing some problems with the shadows shimmering when the camera moves and I'd like to know if it's an issue with my implementation or just an issue with basic/naive shadow mapping itself. Here's a video: http://www.youtube.com/watch?v=vyprATt5BBg&feature=youtu.be Here's the code I use to create the shadow matrices. The commented out code is my original attempt to perfectly fit the view frustum. You can also see my attempt to try clamping movement to texels in the shadow map which didn't seem to make any difference. Then I tried using a bounding sphere instead, also to no apparent effect. public void CreateViewProjectionTransformsToFit(Camera camera, out Matrix viewTransform, out Matrix projectionTransform, out Vector3 position) { BoundingSphere cameraViewFrustumBoundingSphere = BoundingSphere.CreateFromFrustum(camera.ViewFrustum); float lightNearPlaneDistance = 1.0f; Vector3 lookAt = cameraViewFrustumBoundingSphere.Center; float distanceFromLookAt = cameraViewFrustumBoundingSphere.Radius + lightNearPlaneDistance; Vector3 directionFromLookAt = -Direction * distanceFromLookAt; position = lookAt + directionFromLookAt; viewTransform = Matrix.CreateLookAt(position, lookAt, Vector3.Up); float lightFarPlaneDistance = distanceFromLookAt + cameraViewFrustumBoundingSphere.Radius; float diameter = cameraViewFrustumBoundingSphere.Radius * 2.0f; Matrix.CreateOrthographic(diameter, diameter, lightNearPlaneDistance, lightFarPlaneDistance, out projectionTransform); //Vector3 cameraViewFrustumCentroid = camera.ViewFrustum.GetCentroid(); //position = cameraViewFrustumCentroid - (Direction * (camera.FarPlaneDistance - camera.NearPlaneDistance)); //viewTransform = Matrix.CreateLookAt(position, cameraViewFrustumCentroid, Up); //Vector3[] cameraViewFrustumCornersWS = camera.ViewFrustum.GetCorners(); //Vector3[] cameraViewFrustumCornersLS = new Vector3[8]; //Vector3.Transform(cameraViewFrustumCornersWS, ref viewTransform, cameraViewFrustumCornersLS); //Vector3 min = cameraViewFrustumCornersLS[0]; //Vector3 max = cameraViewFrustumCornersLS[0]; //for (int i = 1; i < 8; i++) //{ // min = Vector3.Min(min, cameraViewFrustumCornersLS[i]); // max = Vector3.Max(max, cameraViewFrustumCornersLS[i]); //} //// Clamp to nearest texel //float texelSize = 1.0f / Renderer.ShadowMapSize; //min.X -= min.X % texelSize; //min.Y -= min.Y % texelSize; //min.Z -= min.Z % texelSize; //max.X -= max.X % texelSize; //max.Y -= max.Y % texelSize; //max.Z -= max.Z % texelSize; //// We just use an orthographic projection matrix. The sun is so far away that it's rays are essentially parallel. //Matrix.CreateOrthographicOffCenter(min.X, max.X, min.Y, max.Y, -max.Z, -min.Z, out projectionTransform); } And here's the relevant part of the shader: if (CastShadows) { float4 positionLightCS = mul(float4(position, 1.0f), LightViewProj); float2 texCoord = clipSpaceToScreen(positionLightCS) + 0.5f / ShadowMapSize; float shadowMapDepth = tex2D(ShadowMapSampler, texCoord).r; float distanceToLight = length(LightPosition - position); float bias = 0.2f; if (shadowMapDepth < (distanceToLight - bias)) { return float4(0.0f, 0.0f, 0.0f, 0.0f); } } The shimmer is slightly better if I drastically reduce the view volume but I think that's mostly just because the texels become smaller and it's harder to notice them flickering back and forth. I'd appreciate any insight, I'd very much like to understand what's going on before I try other techniques.

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• LightDM Backgroud is a simple purple radiant

  - by Zahidul Islam

  It seems after I tried to change the login screen background with Ubuntu Tweak, the greeter's background stays a simple purple background with just the spots.. I tried using dconf-editor, rechanging the image from Ubuntu Tweak back to the default, it still does not work. So In The End, everything for the lightdm points to /usr/share/backgrounds/warty-final-ubuntu.png. But it's still a purple solid color. How do I fix it?

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• Need help about Drag a sprite with Animation (Cocos2d)

  - by Zishan

  I want to play an animation when someone drag a sprite from it's default position to another selected position. If he drag half of the selected position then animation will be play half. Example, I have 15 Frames of a animation and have a projectile arm. The projectile arm can be rotate maximum 30°, if someone rotate the arm 2° then animation sprite will be show 2nd frame, if rotate 12° then animation sprite will be show 6th frame.... and so on. Also when he release the arm, then the arm will be reverse back to it's default position and animation frames also will be reverse back to it's default first frame. I am new on cocos2d.I know how to make an animation and how to drag a sprite but I have no idea how to do this. Can anyone Please give me any idea or any tutorial how to do this, it will be very helpful for me. Thank you in advance.

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• Moving Character in C# XNA Not working

  - by Matthew Stenquist

  I'm having trouble trying to get my character to move for a game I'm making in my sparetime for the Xbox. However, I can't seem to figure out what I'm doing wrong , and I'm not even sure if I'm doing it right. I've tried googling tutorials on this but I haven't found any helpful ones. Mainly, ones on 3d rotation on the XNA creators club website. My question is : How can I get the character to walk towards the right in the MoveInput() function? What am I doing wrong? Did I code it wrong? The problem is : The player isn't moving. I think the MoveInput() class isn't working. Here's my code from my character class : using System; using System.Collections.Generic; using System.Linq; using System.Text; using Microsoft.Xna.Framework; using Microsoft.Xna.Framework.Graphics; using Microsoft.Xna.Framework.Input; namespace Jumping { class Character { Texture2D texture; Vector2 position; Vector2 velocity; int velocityXspeed = 2; bool jumping; public Character(Texture2D newTexture, Vector2 newPosition) { texture = newTexture; position = newPosition; jumping = true; } public void Update(GameTime gameTime) { JumpInput(); MoveInput(); } private void MoveInput() { //Move Character right GamePadState gamePad1 = GamePad.GetState(PlayerIndex.One); velocity.X = velocity.X + (velocityXspeed * gamePad1.ThumbSticks.Right.X); } private void JumpInput() { position += velocity; if (GamePad.GetState(PlayerIndex.One).Buttons.A == ButtonState.Pressed && jumping == false) { position.Y -= 1f; velocity.Y = -5f; jumping = true; } if (jumping == true) { float i = 1.6f; velocity.Y += 0.15f * i; } if (position.Y + texture.Height >= 1000) jumping = false; if (jumping == false) velocity.Y = 0f; } public void Draw(SpriteBatch spriteBatch) { spriteBatch.Draw(texture, position, Color.White); } } }

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• Picture rendered from above and below using an Orthographic camera do not match

  - by Roy T.

  I'm using an orthographic camera to render slices of a model (in order to voxelize it). I render each slice both from above and below in order to determine what is inside each slice. I am using an orthographic camera The model I render is a simple 'T' shape constructed from two cubes. The cubes have the same dimensions and have the same Y (height) coordinate. See figure 1 for a render of it in Blender. I render this model once directly from above and once directly from below. My expectation was that I would get exactly the same image (except for mirroring over the y-axis). However when I render using a very low resolution render target (25x25) the position (in pixels) of the 'T' is different when rendered from above as opposed to rendered from below. See figure 2 and 3. The pink blocks are not part of the original rendering but I've added them so you can easily count/see the differences. Figure 2: the T rendered from above Figure 3: the T rendered from below This is probably due to what I've read about pixel and texel coordinates which might be biased to the top-left as seen from the camera. Since I'm using the same 'up' vector for both of my camera's my bias only shows on the x-axis. I've tried to change the position of the camera and it's look-at by, what I thought, should be half a pixel. I've tried both shifting a single camera and shifting both cameras and while I see some effect I am not able to get a pixel-by-pixel perfect copy from both camera's. Here I initialize the camera and compute, what I believe to be, half pixel. boundsDimX and boundsDimZ is a slightly enlarged bounding box around the model which I also use as the width and height of the view volume of the orthographic camera. Matrix projection = Matrix.CreateOrthographic(boundsDimX, boundsDimZ, 0.5f, sliceHeight + 0.5f); Vector3 halfPixel = new Vector3(boundsDimX / (float)renderTarget.Width, 0, boundsDimY / (float)renderTarget.Height) * 0.5f; This is the code where I set the camera position and camera look ats // Position camera if (downwards) { float cameraHeight = bounds.Max.Y + 0.501f - (sliceHeight * i); Vector3 cameraPosition = new Vector3 ( boundsCentre.X, // possibly adjust by half a pixel? cameraHeight, boundsCentre.Z ); camera.Position = cameraPosition; camera.LookAt = new Vector3(cameraPosition.X, cameraHeight - 1.0f, cameraPosition.Z); } else { float cameraHeight = bounds.Max.Y - 0.501f - (sliceHeight * i); Vector3 cameraPosition = new Vector3 ( boundsCentre.X, cameraHeight, boundsCentre.Z ); camera.Position = cameraPosition; camera.LookAt = new Vector3(cameraPosition.X, cameraHeight + 1.0f, cameraPosition.Z); } Main Question Now you've seen all the problems and code you can guess it. My main question is. How do I align both camera's so that they each render exactly the same image (mirrored along the Y axis)? Figure 1 the original model rendered in blender

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• Collision Resolution

  - by ultifinitus

  Hey all, I'm making a simple side-scrolling game, and I would appreciate some input! My collision detection system is a simple bounding box detection, so it's really easy to implement. However my collision resolution is ridiculous! Currently I have a little formula like this: if (colliding(firstObject,secondObject)) firstObject.resolve_collision(yAxisOffset); if (colliding(firstObject,secondObject)) firstObject.resolve_collision(xAxisOffset); where yAxisOffset is only set if the first object's previous y position was outside the second object's collision frame, respectively xAxisOffset as well. Now this is working great, in general. However there is a single problem. When I have a stack of objects and I push the first object against that stack, the first object get's "stuck," on the stack. What's I think is happening is the object's collision system checks and resolves for collisions based on creation time, so If I check one axis, then the other, the object will "sink" object directly along the checking axis. This sinking action causes the collision detection routine to think there's a gap between our position and the other object's position, and when I finally check the object that I've already sunk into, my object's position is resolved to it's original position... All this is great, and I'm sure if I bang my head against a wall long enough i'll come up with a working algorithm, but I'd rather not =). So what in the heck do you think I should do? How could I change my collision resolution system to fix this? Here's the program (temporary link, not sure how long it'll last) (notes: arrow keys to navigate, click to drop block, x to jump) I'd appreciate any help you can offer!

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• how to define a field of view for the entire map for shadow?

  - by Mehdi Bugnard

  I recently added "Shadow Mapping" in my XNA games to include shadows. I followed the nice and famous tutorial from "Riemers" : http://www.riemers.net/eng/Tutorials/XNA/Csharp/Series3/Shadow_map.php . This code work nice and I can see my source of light and shadow. But the problem is that my light source does not match the field of view that I created. I want the light covers the entire map of my game. I don't know why , but the light only affect 2-3 cubes of my map. ScreenShot: (the emission of light illuminates only 2-3 blocks and not the full map) Here is my code i create the fieldOfView for LightviewProjection Matrix: Vector3 lightDir = new Vector3(10, 52, 10); lightPos = new Vector3(10, 52, 10); Matrix lightsView = Matrix.CreateLookAt(lightPos, new Vector3(105, 50, 105), new Vector3(0, 1, 0)); Matrix lightsProjection = Matrix.CreatePerspectiveFieldOfView(MathHelper.PiOver2, 1f, 20f, 1000f); lightsViewProjectionMatrix = lightsView * lightsProjection; As you can see , my nearPlane and FarPlane are set to 20f and 100f . So i don't know why the light stop after 2 cubes. it's should be bigger Here is set the value to my custom effect HLSL in the shader file /* SHADOW VALUE */ effectWorld.Parameters["LightDirection"].SetValue(lightDir); effectWorld.Parameters["xLightsWorldViewProjection"].SetValue(Matrix.Identity * .lightsViewProjectionMatrix); effectWorld.Parameters["xWorldViewProjection"].SetValue(Matrix.Identity * arcadia.camera.View * arcadia.camera.Projection); effectWorld.Parameters["xLightPower"].SetValue(1f); effectWorld.Parameters["xAmbient"].SetValue(0.3f); Here is my custom HLSL shader effect file "*.fx" // This sample uses a simple Lambert lighting model. float3 LightDirection = normalize(float3(-1, -1, -1)); float3 DiffuseLight = 1.25; float3 AmbientLight = 0.25; uniform const float3 DiffuseColor = 1; uniform const float Alpha = 1; uniform const float3 EmissiveColor = 0; uniform const float3 SpecularColor = 1; uniform const float SpecularPower = 16; uniform const float3 EyePosition; // FOG attribut uniform const float FogEnabled ; uniform const float FogStart ; uniform const float FogEnd ; uniform const float3 FogColor ; float3 cameraPos : CAMERAPOS; texture Texture; sampler Sampler = sampler_state { Texture = (Texture); magfilter = LINEAR; minfilter = LINEAR; mipfilter = LINEAR; AddressU = mirror; AddressV = mirror; }; texture xShadowMap; sampler ShadowMapSampler = sampler_state { Texture = <xShadowMap>; magfilter = LINEAR; minfilter = LINEAR; mipfilter = LINEAR; AddressU = clamp; AddressV = clamp; }; /* *************** */ /* SHADOW MAP CODE */ /* *************** */ struct SMapVertexToPixel { float4 Position : POSITION; float4 Position2D : TEXCOORD0; }; struct SMapPixelToFrame { float4 Color : COLOR0; }; struct SSceneVertexToPixel { float4 Position : POSITION; float4 Pos2DAsSeenByLight : TEXCOORD0; float2 TexCoords : TEXCOORD1; float3 Normal : TEXCOORD2; float4 Position3D : TEXCOORD3; }; struct SScenePixelToFrame { float4 Color : COLOR0; }; float DotProduct(float3 lightPos, float3 pos3D, float3 normal) { float3 lightDir = normalize(pos3D - lightPos); return dot(-lightDir, normal); } SSceneVertexToPixel ShadowedSceneVertexShader(float4 inPos : POSITION, float2 inTexCoords : TEXCOORD0, float3 inNormal : NORMAL) { SSceneVertexToPixel Output = (SSceneVertexToPixel)0; Output.Position = mul(inPos, xWorldViewProjection); Output.Pos2DAsSeenByLight = mul(inPos, xLightsWorldViewProjection); Output.Normal = normalize(mul(inNormal, (float3x3)World)); Output.Position3D = mul(inPos, World); Output.TexCoords = inTexCoords; return Output; } SScenePixelToFrame ShadowedScenePixelShader(SSceneVertexToPixel PSIn) { SScenePixelToFrame Output = (SScenePixelToFrame)0; float2 ProjectedTexCoords; ProjectedTexCoords[0] = PSIn.Pos2DAsSeenByLight.x / PSIn.Pos2DAsSeenByLight.w / 2.0f + 0.5f; ProjectedTexCoords[1] = -PSIn.Pos2DAsSeenByLight.y / PSIn.Pos2DAsSeenByLight.w / 2.0f + 0.5f; float diffuseLightingFactor = 0; if ((saturate(ProjectedTexCoords).x == ProjectedTexCoords.x) && (saturate(ProjectedTexCoords).y == ProjectedTexCoords.y)) { float depthStoredInShadowMap = tex2D(ShadowMapSampler, ProjectedTexCoords).r; float realDistance = PSIn.Pos2DAsSeenByLight.z / PSIn.Pos2DAsSeenByLight.w; if ((realDistance - 1.0f / 100.0f) <= depthStoredInShadowMap) { diffuseLightingFactor = DotProduct(xLightPos, PSIn.Position3D, PSIn.Normal); diffuseLightingFactor = saturate(diffuseLightingFactor); diffuseLightingFactor *= xLightPower; } } float4 baseColor = tex2D(Sampler, PSIn.TexCoords); Output.Color = baseColor*(diffuseLightingFactor + xAmbient); return Output; } SMapVertexToPixel ShadowMapVertexShader(float4 inPos : POSITION) { SMapVertexToPixel Output = (SMapVertexToPixel)0; Output.Position = mul(inPos, xLightsWorldViewProjection); Output.Position2D = Output.Position; return Output; } SMapPixelToFrame ShadowMapPixelShader(SMapVertexToPixel PSIn) { SMapPixelToFrame Output = (SMapPixelToFrame)0; Output.Color = PSIn.Position2D.z / PSIn.Position2D.w; return Output; } /* ******************* */ /* END SHADOW MAP CODE */ /* ******************* */ / For rendering without instancing. technique ShadowMap { pass Pass0 { VertexShader = compile vs_2_0 ShadowMapVertexShader(); PixelShader = compile ps_2_0 ShadowMapPixelShader(); } } technique ShadowedScene { /* pass Pass0 { VertexShader = compile vs_2_0 VSBasicTx(); PixelShader = compile ps_2_0 PSBasicTx(); } */ pass Pass1 { VertexShader = compile vs_2_0 ShadowedSceneVertexShader(); PixelShader = compile ps_2_0 ShadowedScenePixelShader(); } } technique SimpleFog { pass Pass0 { VertexShader = compile vs_2_0 VSBasicTx(); PixelShader = compile ps_2_0 PSBasicTx(); } } I edited my fx file , for show you only information and functions about the shadow ;-)

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