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• Objective-C or C++ for iOS games?

  - by Martin Wickman

  I'm pretty confident programming in Objective-C and C++, but I find Objective-C to be somewhat easier to use and more flexible and dynamic in nature. What would be the pros and cons when using C++ instead of Obj-C for writing games in iOS? Or rather, are there any known problems with using Obj-C as compared to C++? For instance, I suspect there might be performance issues with Obj-C compared to code written in C/C++.

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• Flixel - Animated Tilemaps

  - by nospoone

  I am using Flixel 2.55 and I am trying to animate a tilemap. I found this piece of code that apparently enables the use of sprites as tiles. From what I understand, this loops over the tilemap's graphic and replaces the tile's pixels with the sprite's pixels each time they change. I have implemented the class and it's working, but not completely; the tiles get replaced, but do not animate unless the camera moves. Here's the relevant parts from LevelLoader.as, which only instantiates the AnimatedTilemaps (piece of code from forum) and pushes sprites to the array. // AnimatedTile is just an extended FlxSprite private var _waterTop1:AnimatedTile; // Create ground tilemap _groundTilemap = new AnimatedTilemap(); _groundTilemap.loadMap(_rawXML.Ground, Assets.OverworldGround, 8, 8); FlxG.state.add(_groundTilemap); _waterTop1 = new AnimatedTile(8, 8, Assets.WaterTop, 100); // .Animate only adds and plays an animation, with a startAtFrame param. _waterTop1.Animate('run', [0...47], 10, true, 0); Now, it seems as though the sprites are updating. I tried tracing the update()s, and they are running for both the sprites and the tilemap. The sprites are even changing frames. Using only AnimatedTiles and hard placing them (giving a x and y) works and animates. What troubles me is that they only update when the camera moves. I've been on this for a week now and can't seem to put my finger on what's wrong. I am also open to other solutions to have animates tiles in a tilemap. If other details are needed, just ask. PS: Sorry for my english, I am not a native speaker...

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• How do I draw an OpenGL point sprite using libgdx for Android?

  - by nbolton

  Here's a few snippets of what I have so far... void create() { renderer = new ImmediateModeRenderer(); tiles = Gdx.graphics.newTexture( Gdx.files.getFileHandle("res/tiles2.png", FileType.Internal), TextureFilter.MipMap, TextureFilter.Linear, TextureWrap.ClampToEdge, TextureWrap.ClampToEdge); } void render() { Gdx.gl.glClear(GL10.GL_COLOR_BUFFER_BIT | GL10.GL_DEPTH_BUFFER_BIT); Gdx.gl.glClearColor(0.6f, 0.7f, 0.9f, 1); } void renderSprite() { int handle = tiles.getTextureObjectHandle(); Gdx.gl.glBindTexture(GL.GL_TEXTURE_2D, handle); Gdx.gl.glEnable(GL.GL_POINT_SPRITE); Gdx.gl11.glTexEnvi(GL.GL_POINT_SPRITE, GL.GL_COORD_REPLACE, GL.GL_TRUE); renderer.begin(GL.GL_POINTS); renderer.vertex(pos.x, pos.y, pos.z); renderer.end(); } create() is called once when the program starts, and renderSprites() is called for each sprite (so, pos is unique to each sprite) where the sprites are arranged in a sort-of 3D cube. Unfortunately though, this just renders a few white dots... I suppose that the texture isn't being bound which is why I'm getting white dots. Also, when I draw my sprites on anything other than 0 z-axis, they do not appear -- I read that I need to crease my zfar and znear, but I have no idea how to do this using libgdx (perhaps it's because I'm using ortho projection? What do I use instead?). I know that the texture is usable, since I was able to render it using a SpriteBatch, but I guess I'm not using it properly with OpenGL.

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• Quick 2D sight area calculation algorithm?

  - by Rogach

  I have a matrix of tiles, on some of that tiles there are objects. I want to calculate which tiles are visible to player, and which are not, and I need to do it quite efficiently (so it would compute fast enough even when I have a big matrices (100x100) and lots of objects). I tried to do it with Besenham's algorithm, but it was slow. Also, it gave me some errors: ----XXX- ----X**- ----XXX- -@------ -@------ -@------ ----XXX- ----X**- ----XXX- (raw version) (Besenham) (correct, since tunnel walls are still visible at distance) (@ is the player, X is obstacle, * is invisible, - is visible) I'm sure this can be done - after all, we have NetHack, Zangband, and they all dealt with this problem somehow :) What algorithm can you recommend for this? EDIT: Definition of visible (in my opinion): tile is visible when at least a part (e.g. corner) of the tile can be connected to center of player tile with a straight line which does not intersect any of obstacles.

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• How to implement friction in a physics engine based on "Advanced Character Physics"

  - by paldepind

  I have implemented a physics engine based on the concepts in the classic text Advanced Character Physics by Thomas Jakobsen. Friction is only discussed very briefly in the article and Jakobsen himself notes how "other and better friction models than this could and should be implemented." Generally how could one implement a believable friction model on top of the concepts from the mentioned article? And how could the found friction be translated into rotation on a circle? I do not want this question to be about my specific implementation but about how to combine Jakobsens ideas with a great friction system more generally. But here is a live demo showing the current state of my engine which does not handle friction in any way: http://jsfiddle.net/Z7ECB/embedded/result/ Below is a picture showing and example on how collision detection could work in an engine based in the paper. In the Verlet integration the current and previous position is always stored. Based on these a new position is calculated. In every frame I calculate the distance between the circles and the lines. If this distance is less than a circles radius a collision has occurred and the circle is projected perpendicular out of the offending line according to the size of the overlap (offset on the picture). Velocity is implicit due to Verlet integration so changing position also changes the velocity. What I need to do know is to somehow determine the amount of friction on the circle and move it backwards parallel to the line in order to reduce its speed.

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• Stream Media and Live TV Across the Internet with Orb

  - by DigitalGeekery

  Looking for a way to stream your media collection across the Internet? Or perhaps watch and record TV remotely? Today we are going to look at how to do all that and more with Orb. Requirements Windows XP / Vista / 7 or Intel based Mac w/ OS X 10.5 or later. 1 GB RAM or more Pentium 4 2.4 GHz or higher / AMD Athlon 3200+ Broadband connections TV Tuner for streaming and recording live TV (optional) Note: Slower internet connections may result in stuttering during playback. Installation and Setup Download and install Orb on your home computer. (Download link below) You’ll want to take the defaults for the initial portion of the install. When we get to the Orb Account setup portion of the install is when we will have to enter information and make some decisions. Choose your language and click Next. We’ll need to create and user account and password. A valid email address is required as we’ll need to confirm the account later. Click Next.   Now you’ll want to choose your media sources. Orb will automatically look for folders that may contain media files. You can add or remove folders click on the (+) or (-) buttons. To remove a folder, click on it once to select it from the list and then click the minus (-) button. To add a folder, click the plus (+) button and browse for the folder. You can add local folders as well as shared folders from networked computers and USB attached storage. Note: Both the host computer running Orb and the networked computer will need to be running to access shared network folders remotely. When you’ve selected all your media files, click Next. Orb will proceed to index your media files… When the indexing is complete, click Next. Orb TV Setup Note: Streaming Live TV to Macs is not currently supported. If you have a TV tuner card connected to your PC, you can opt to configure Orb to stream live or recorded TV. Click Next  to configure TV. Or, choose Skip if you don’t wish to configure Orb for TV.   If you have a Digital tuner card, type in your Zip Code and click Get List to pull your channel listings. Select a TV provider from the list and click Next. If not, click Skip.   You can select or deselect any channels by checking or un-checking the box to each channel. Select Auto Scan to let Orb find more channels or disable the ones with no reception. Click Next when finished.   Next choose an analog provider, if necessary, and click Next.   Select “Yes” or “No” for a set top box and click Next. Just as we did with the Digital tuner, select or deselect any channels by checking or un-checking the box to each channel. Select Auto Scan to let Orb find more channels or disable the ones with no reception. Click Next when finished.   Now we’re finished with the setup. Click Close. Accessing your Media Remotely Media files are accessed through a web-based interface. Before we go any further, however, we’ll need to confirm our username and password. Check your inbox for an email from Orb Networks. Click the enclosed confirmation link. You’ll be prompted to enter the username and password you selected in your browser then click Next.   Your account will be confirmed. Now, we’re ready to enjoy our media remotely. To get started, point your browser to the MyCast website from your remote computer. (See link below) Enter your credentials and click Log In. Once logged in, you’ll be presented with the MyCast Home screen. By default you’ll see a handful of “channels” such as a TV program guide, random audio and photos, video favorites, and weather. You can add, remove, or customize channels. To add additional channels, click on Add Channels at the top right…   …and select from the dropdown list. To access your full media libraries, click Open Application at the top left and select from one of the options. Live and Recorded TV If you have a TV tuner card you configured for Orb, you’ll see your program guide on the TV / Webcams screen. To watch or record a show, click on the program listing to bring up a detail box. Then click the red button to record, or the green button to play. When recording a show, you’ll see a pulsating red icon at the top right of the listing in the program guide. If you want to watch Live TV, you may be prompted to choose your media player, depending on your browser and settings. Playback should begin shortly.   Note for Windows Media Center Users If you try to stream live TV in Orb while Windows Media Center is running on your PC, you’ll get an error message. Click the Stop MediaCenter button and then try again.   Audio On the Audio screen, you’ll find your music files indexed by genre, artist, and album. You can play a selection by clicking once and then clicking the green play button, or by simply double-clicking.   Playback will begin in the default media player for the streaming format.   Video Video works essentially the same as audio. Click on a selection and press the green play button, or double-click on the video title. Video playback will begin in the default media player for the streaming format.   Streaming Formats You can change the default streaming format in the control panel settings. To access the Control Panel, click on Open Applications  and select Control Panel. You can also click Settings at the top right.   Select General from the drop down list and then click on the Streaming Formats tab. You are provided four options. Flash, Windows Media, .SDP, and .PLS.   Creating Playlists To create playlists, drag and drop your media title to the playlist work area on the right, or click Add to playlist on the top menu. Click Save when finished.    Sharing your Media Orb allows you to share media playlists across the Internet with friends and family. There are a few ways to accomplish this. We’ll start by click the Share button at the bottom of the playlist work area after you’ve compiled your playlist. You’ll be prompted to choose a method by which to share your playlist. You’ll have the option to share your playlist publicly or privately. You can share publically through links, blogs, or on your Orb public profile.  By choosing the Public Profile option, Orb will automatically create a profile page for you with a URL like http://public.orb.com/username that anyone can easily access on the Internet. The private sharing option allows you to invite friends by email and requires recipients to register with Orb. You can also give your playlist a custom name, or accept the auto-generated title. Click OK when finished. Users who visit your public profile will be able to view and stream any of your shared playlists to their computer or supported device.   Portable Media Devices and Smartphones Orb can stream media to many portable devices and 3G phones. Streaming audio is supported on the iPhone and iPod Touch through the Safari browser. However, video and live TV streaming requires the Orb Live iPhone App.  Orb Live is available in the App store for $9.99. To stream media to your portable device, go to the MyCast website in your mobile browser and login. Browse for your media or playlist. Make a selection and play the media. Playback will begin. We found streaming music to both the Droid and the iPhone to work quite nicely. Video playback on the Droid, however, left a bit to be desired. The video looked good, but the audio tended to be out of sync. System Tray Control Panel By default Orb runs in the system tray on start up. To access the System Tray Control Panel, right-click on the Orb icon in the system tray and select Control Panel. Login with your Orb username and  password and click OK.   From here you can add or remove media sources, add manage accounts, change your password, and more. If you’d rather not run Orb on Startup, click the General icon.   Unselect the checkbox next to Start Orb when the system starts. Conclusion It may seem like a lot of steps, but getting Orb up and running isn’t terribly difficult. Orb is available for both Windows and Intel based Macs. It also supports streaming to many Game Consoles such as the Wii, PS3, and XBox 360. If you are running Windows 7 on multiple computers, you may want to check out our write-up on how to stream music and video over the Internet with Windows Media Player 12. Downloads Download Orb Logon to MyCast Similar Articles Productive Geek Tips Stream Music and Video Over the Internet with Windows Media Player 12Enable Media Streaming in Windows Home Server to Windows Media PlayerStream Media from Windows 7 to XP with VLC Media PlayerShare Digital Media With Other Computers on a Home Network with Windows 7Automatically Start Windows 7 Media Center in Live TV Mode 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 DVDFab 6 Revo Uninstaller Pro Registry Mechanic 9 for Windows PC Tools Internet Security Suite 2010 Looking for Good Windows Media Player 12 Plug-ins? Find Out the Celebrity You Resemble With FaceDouble Whoa ! Use Printflush to Solve Printing Problems Icelandic Volcano Webcams Open Multiple Links At One Go

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• Doubt about texture waves in CG Ocean Shader

  - by Alexandre

  I'm new on graphical programming, and I'm having some trouble understanding the Ocean Shader described on "Effective Water Simulation from Physical Models" from GPU Gems. The source code associated to this article is here. My problem has been to understand the concept of texture waves. First of all, what is achieved by texture waves? I'm having a hard time trying to figure out it's usefulness. In the section 1.2.4 of the article, it does say that the waves summed into the texture have the same parametrization as the waves used for vertex positioning. Does it mean that I can't use the texture provided by the source code if I change the parameters of the waves, or add more waves to sum? And in the section 1.4.1, is said that we can assume that there is no rotation between texture space and world space if the texture coordinates for our normal map are implicit. What does mean that the "normal map are implicit'? And why do I need a rotation between texture and world spaces if the normal map are not implicit? I would be very grateful for any help on this.

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• Opengl glVertexAttrib4fv doesn't work?

  - by Naor

  This is my vertex shader: static const GLchar * vertex_shader_source[] = { "#version 430 core \n" "layout (location = 0) in vec4 offset; \n" "void main(void) \n" "{ \n" " const vec4 vertices[3] = vec4[3](vec4( 0.25, -0.25, 0.5, 1.0),\n" " vec4(-0.25, -0.25, 0.5, 1.0), \n" " vec4( 0.25, 0.25, 0.5, 1.0)); \n" " gl_Position = vertices[gl_VertexID] + offset; \n" "} \n" }; and this is what im trying to do: glUseProgram(rendering_program); GLfloat attrib[] = { (float)sin(currentTime) * 0.5f, (float)cos(currentTime) * 0.6f, 0.0f, 0.0f }; glVertexAttrib4fv(0, attrib); glDrawArrays(GL_TRIANGLES, 0, 3); currentTime - The number in seconds since the program has started. Expected result - Triangle moving around the window. Its from the SuperBible book (sixth edition), this is the full code:http://pastebin.com/xA3eCKz1 The triangle should move across the screen but it doesn't.

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• Blender mesh mirroring screws up normals when importing in Unity

  - by Shivan Dragon

  My issue is as follows: I've modeled a robot in Blender 2.6. It's a mech-like biped or if you prefer, it kindda looks like a chicken. Since it's symmetrical on the XZ plane, I've decided to mirror some of its parts instead of re-modeling them. Problem is, those mirrored meshes look fine in Blender (faces all show up properly and light falls on them as it should) but in Unity faces and lighting on those very same mirrored meshes is wrong. What also stumps me is the fact that even if I flip normals in Blender, I still get bad results in Unity for those meshes (though now I get different bad results than before). Here's the details: Here's a Blender screen shot of the robot. I've took 2 pictures and slightly rotated the camera around so the geometry in question can be clearly seen: Now, the selected cog-wheel-like piece is the mirrored mesh obtained from mirroring the other cog-wheel on the other (far) side of the robot torso. The back-face culling is turned of here, so it's actually showing the faces as dictated by their normals. As you can see it looks ok, faces are orientated correctly and light falls on it ok (as it does on the original cog-wheel from which it was mirrored). Now if I export this as fbx using the following settings: and then import it into Unity, it looks all screwy: It looks like the normals are in the wrong direction. This is already very strange, because, while in Blender, the original cog-wheel and its mirrored counter part both had normals facing one way, when importing this in Unity, the original cog-wheel still looks ok (like in Blender) but the mirrored one now has normals inverted. First thing I've tried is to go "ok, so I'll flip normals in Blender for the mirrored cog-wheel and then it'll display ok in Unity and that's that". So I went back to Blender, flipped the normals on that mesh, so now it looks bad in Blender: and then re-exported as fbx with the same settings as before, and re-imported into Unity. Sure enough the cog-wheel now looks ok in Unity, in the sense where the faces show up properly, but if you look closely you'll notice that light and shadows are now wrong: Now in Unity, even though the light comes from the back of the robot, the cog-wheel in question acts as if light was coming from some-where else, its faces which should be in shadow are lit up, and those that should be lit up are dark. Here's some things I've tried and which didn't do anything: in Blender I tried mirroring the mesh in 2 ways: first by using the scale to -1 trick, then by using the mirroring tool (select mesh, hit crtl-m, select mirror axis), both ways yield the exact same result in Unity I've tried playing around with the prefab import settings like "normals: import/calculate", "tangents: import/calculate" I've also tired not exporting as fbx manually from Blender, but just dropping the .blend file in the assets folder inside the Unity project So, my question is: is there a way to actually mirror a mesh in Blender and then have it imported in Unity so that it displays properly (as it does in Blender)? If yes, how? Thank you, and please excuse the TL;DR style.

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• Determine arc-length of a Catmull-Rom spline

  - by Wouter

  I have a path that is defined by a concatenation of Catmull-Rom splines. I use the static method Vector2.CatmullRom in XNA that allows for interpolation between points with a value going from 0 to 1. Not every spline in this path has the same length. This causes speed differences if I let the weight go at a constant speed for every spline while proceeding along the path. I can remedy this by letting the speed of the weight be dependent on the length of the spline. How can I determine the length of such a spline? Should I just approximate by cutting the spline into 10 straight lines and sum their lengths? I'm using this for dynamic texture mapping on a generated mesh defined by splines.

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• OpenGL 2 on Android: native window

  - by ThreaderSlash

  According to OGLES specification, we have the following definition: EGLSurface eglCreateWindowSurface(EGLDisplay display, EGLConfig config, NativeWindowType native_window, EGLint const * attrib_list) More details, here: http://www.khronos.org/opengles/documentation/opengles1_0/html/eglCreateWindowSurface.html And also by definition: int32_t ANativeWindow_setBuffersGeometry(ANativeWindow* window, int32_t width, int32_t height, int32_t format); More details, here: http://mobilepearls.com/labs/native-android-api I am running Android Native App on OGLES 2 and debugging it in a Samsung Nexus device. For setting up the 3D scene graph environment, the following variables are defined: struct android_app { ... ANativeWindow* window; }; android_app* mApplication; ... mApplication=&pApplication; And to initialize the App, we run the commands in the code: ANativeWindow_setBuffersGeometry(mApplication->window, 0, 0, lFormat); mSurface = eglCreateWindowSurface(mDisplay, lConfig, mApplication->window, NULL); Funny to say is that, the command ANativeWindow_setBuffersGeometry behaves as expected and works fine according to its definition, accepting all the parameters sent to it. But the eglCreateWindowSurface does no accept the parameter mApplication-window, as it should accept according to its definition. Instead, it looks for the following input: EGLNativeWindowType hWnd; mSurface = eglCreateWindowSurface(mDisplay,lConfig,hWnd,NULL); As an alternative, I considered to use instead: NativeWindowType hWnd=android_createDisplaySurface(); But debugger says: Function 'android_createDisplaySurface' could not be resolved Can someone tell if there is a way to convert mApplication-window? In a way that the data from the android_app get accepted to the window surface?

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• Pygame surface rotation, rect rotation or sprite rotation?

  - by Alan

  i seem to have a conceptual misunderstanding of the surface and rect object in pygame. I currently observe these objects this way: Surface Just the loaded image rect the 'hard' representation of the ingame object (sprite). Used for simplifying object moment and collision detection sprite rect and surface grouped together What i want to do is rotate my sprite. The only available method i found for rotation is pygame.transform.rotate. How do i rotate the rectangle, or even better, the whole sprite? Below is the image of how i visualize this problem.

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• Approximating walking physics via simpler sliding physics

  - by Dave

  I am modeling walking insects. I implement them as cuboids and use forces (including friction and drag), to control motion. However, the movement characteristics of this 'sliding box' physics don't match those due to a legged creature. For example, legged creatures near-instantly accelerate to their top speed; whereas applying a force to a box takes time to accelerate it. The applied force can be increased along with the counteracting drag, giving much quicker acceleration (via force) to a max speed (via drag). However, this also means the force that creatures can exert when pushing on other objects is increased. Does anyone know of any techniques using a physics engine to cheaply model walking creatures?

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• Cocos2d-x Spritebatch node animation appears to be broken? cocos2d-x 2.0.3

  - by George Host

  Hi I have spent aprox 2 days trying to get this to work doing a google searches left and right and I did get it working except for sprite batch nodes. So in my class I am able to load kuwalio_stand.png and I tested kuwalio_walk1.png and 2 and 3 from the FrameCache(). They work for sure 100%. I run this code and it does not animate does anyone else have the same issue with sprite batch nodes? cocos2d::CCSprite * player = Player::create(); player->setPosition(cocos2d::CCPointMake(0.0f,0.0f)); player->setDisplayFrame(cocos2d::CCSpriteFrameCache::sharedSpriteFrameCache()->spriteFrameByName("kuwalio_stand.png")); player->setTag(PlayerTag); cocos2d::CCAnimation * walk = cocos2d::CCAnimation::create(); cocos2d::CCSpriteFrame * walk1 = cocos2d::CCSpriteFrameCache::sharedSpriteFrameCache()->spriteFrameByName("kuwalio_walk1"); cocos2d::CCSpriteFrame * walk2 = cocos2d::CCSpriteFrameCache::sharedSpriteFrameCache()->spriteFrameByName("kuwalio_walk2"); cocos2d::CCSpriteFrame * walk3 = cocos2d::CCSpriteFrameCache::sharedSpriteFrameCache()->spriteFrameByName("kuwalio_walk3"); walk->addSpriteFrame(walk1); walk->addSpriteFrame(walk2); walk->addSpriteFrame(walk3); cocos2d::CCAnimate * actionWalk = cocos2d::CCAnimate::create(walk); cocos2d::CCRepeatForever * actionRepeat = cocos2d::CCRepeatForever::create(actionWalk); walk->setDelayPerUnit(0.1f); actionWalk->setDuration(10.1f); this->runAction(actionRepeat); // Change camera to a soft follow camera. this->runAction(cocos2d::CCFollow::create(player)); mSceneSpriteBatchNode->addChild(player); // Have the CCNode object run its virtual update function as fast as possible. // Every frame for this layer. this-scheduleUpdate(); Counter example without the sprite batch node... cocos2d::CCSprite * sprite = cocos2d::CCSprite::create("kuwalio_walk1.png"); this->addChild(sprite,0); sprite->setPosition(cocos2d::CCPointMake(60,60)); sprite->retain(); cocos2d::CCAnimation * actionAnimation = cocos2d::CCAnimation::create(); actionAnimation->setDelayPerUnit(0.01f); actionAnimation->retain(); actionAnimation->addSpriteFrameWithFileName("kuwalio_walk1.png"); actionAnimation->addSpriteFrameWithFileName("kuwalio_walk2.png"); actionAnimation->addSpriteFrameWithFileName("kuwalio_walk3.png"); cocos2d::CCAnimate * a = cocos2d::CCAnimate::create(actionAnimation); a->setDuration(0.10f); cocos2d::CCRepeatForever * actionRepeat = cocos2d::CCRepeatForever::create(a); sprite->runAction(actionRepeat);

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• working in extrenal actionscript file does not show anything on the screen?

  - by XNA

  I'm writing this code in Flash builder and I tested the file in flash, but nothing appears in the swf file. (no text in the screen show , i don't know why) Is there any missing property in the code? Also, when I create text or movie clip with flash tools on the stage and give it an instance name, flash builder doesn't seem to recognize it in the action script code. package { import flash.display.MovieClip; import flash.text.TextField; public class mark extends MovieClip { public function mark() { super(); public var d:TextField=new TextField(); d.text="Hello world"; d.x=250; d.y=300; addChild(d); } }

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• RK4 Bouncing a Ball

  - by Jonathan Dickinson

  I am trying to wrap my head around RK4. I decided to do the most basic 'ball with gravity that bounces' simulation. I have implemented the following integrator given Glenn Fiedler's tutorial: /// <summary> /// Represents physics state. /// </summary> public struct State { // Also used internally as derivative. // S: Position // D: Velocity. /// <summary> /// Gets or sets the Position. /// </summary> public Vector2 X; // S: Position // D: Acceleration. /// <summary> /// Gets or sets the Velocity. /// </summary> public Vector2 V; } /// <summary> /// Calculates the force given the specified state. /// </summary> /// <param name="state">The state.</param> /// <param name="t">The time.</param> /// <param name="acceleration">The value that should be updated with the acceleration.</param> public delegate void EulerIntegrator(ref State state, float t, ref Vector2 acceleration); /// <summary> /// Represents the RK4 Integrator. /// </summary> public static class RK4 { private const float OneSixth = 1.0f / 6.0f; private static void Evaluate(EulerIntegrator integrator, ref State initial, float t, float dt, ref State derivative, ref State output) { var state = new State(); // These are a premature optimization. I like premature optimization. // So let's not concentrate on that. state.X.X = initial.X.X + derivative.X.X * dt; state.X.Y = initial.X.Y + derivative.X.Y * dt; state.V.X = initial.V.X + derivative.V.X * dt; state.V.Y = initial.V.Y + derivative.V.Y * dt; output = new State(); output.X.X = state.V.X; output.X.Y = state.V.Y; integrator(ref state, t + dt, ref output.V); } /// <summary> /// Performs RK4 integration over the specified state. /// </summary> /// <param name="eulerIntegrator">The euler integrator.</param> /// <param name="state">The state.</param> /// <param name="t">The t.</param> /// <param name="dt">The dt.</param> public static void Integrate(EulerIntegrator eulerIntegrator, ref State state, float t, float dt) { var a = new State(); var b = new State(); var c = new State(); var d = new State(); Evaluate(eulerIntegrator, ref state, t, 0.0f, ref a, ref a); Evaluate(eulerIntegrator, ref state, t + dt * 0.5f, dt * 0.5f, ref a, ref b); Evaluate(eulerIntegrator, ref state, t + dt * 0.5f, dt * 0.5f, ref b, ref c); Evaluate(eulerIntegrator, ref state, t + dt, dt, ref c, ref d); a.X.X = OneSixth * (a.X.X + 2.0f * (b.X.X + c.X.X) + d.X.X); a.X.Y = OneSixth * (a.X.Y + 2.0f * (b.X.Y + c.X.Y) + d.X.Y); a.V.X = OneSixth * (a.V.X + 2.0f * (b.V.X + c.V.X) + d.V.X); a.V.Y = OneSixth * (a.V.Y + 2.0f * (b.V.Y + c.V.Y) + d.V.Y); state.X.X = state.X.X + a.X.X * dt; state.X.Y = state.X.Y + a.X.Y * dt; state.V.X = state.V.X + a.V.X * dt; state.V.Y = state.V.Y + a.V.Y * dt; } } After reading over the tutorial I noticed a few things that just seemed 'out' to me. Notably how the entire simulation revolves around t at 0 and state at 0 - considering that we are working out a curve over the duration it seems logical that RK4 wouldn't be able to handle this simple scenario. Never-the-less I forged on and wrote a very simple Euler integrator: static void Integrator(ref State state, float t, ref Vector2 acceleration) { if (state.X.Y > 100 && state.V.Y > 0) { // Bounce vertically. acceleration.Y = -state.V.Y * t; } else { acceleration.Y = 9.8f; } } I then ran the code against a simple fixed-time step loop and this is what I got: 0.05 0.20 0.44 0.78 1.23 1.76 ... 74.53 78.40 82.37 86.44 90.60 94.86 99.23 103.05 105.45 106.94 107.86 108.42 108.76 108.96 109.08 109.15 109.19 109.21 109.23 109.23 109.24 109.24 109.24 109.24 109.24 109.24 109.24 109.24 109.24 109.24 109.24 109.24 109.24 109.24 ... As I said, I was expecting it to break - however I am unsure of how to fix it. I am currently looking into keeping the previous state and time, and working from that - although at the same time I assume that will defeat the purpose of RK4. How would I get this simulation to print the expected results?

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• Unity3D and Texture2D. GetPixel returns wrong values

  - by Heisenbug

  I'm trying to use Texture2D set and get colors, but I encountered a strange behavior. Here's the code to reproduce it: Texture2D tex = new Texture2D(2,2, TextureFormat.RGBA32 ,false); Color col = new Color(1.0f,0.5f,1.0f,0.5f); //col values: 1.00, 0.500, 1.00, 0.500 tex.setPixel(0,0,col); Color colDebug = tex.getPixel(0,0); //col values: 1.00, 0.502, 1.00, 0.502 The Color retrieved with getPixel is different from the Color set before. I initially thought about float approximation, but when inspectin col the value stored are correct, so can't be that reason. It sounds weird even a sampling error because the getValue returns a value really similar that not seems to be interpolated with anything else. Anyway I tried even to add these lines after building the texture but nothing change: this.tex.filterMode = FilterMode.Point; this.tex.wrapMode = TextureWrapMode.Clamp; this.tex.anisoLevel = 1; What's my mistake? What am I missing? In addition to that. I'm using tex to store Rect coordinates returned from atlas generation, in order to be able of retriving the correct uv coordinate of an atlas inside a shader. Is this a right way to go?

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• Pixel Shader - apply a mask (XNA)

  - by Michal Bozydar Pawlowski

  I'd like to apply a simple few masks to few images. The first mask I'd like to implement is mask like: XXXOOO I mean, that on the right everything is masked (to black), and on the left everything is stayed without changes. The second mask I'd like to implement is glow mask. I mean something like this: O O***O O**X**O O***O O What I mean, is a circle mask, which in the center everything is saved without changes, and going outside the circle everything is starting to be black The last mask is irregular mask. For example like this: OOO* O**X**O OO**OO**O OO*X*O O*O O Where: O - to black * - to gray X - without changes I've read, how to apply distortion pixel shader in XNA: msdn Could you explain me how to apply mute mask on an image? (mask will be grayscale)

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• Collision in Tiled Map - LibGDX

  - by user43353

  I have collision code that deals with left or right or top or bottom. I am using Tiled Map with LibGDX. Question is: How do I detect collision with other cells by all 4 sides, and not specifically by left/right or top/bottom. Here is my top/bottom and left/right collision code: private boolean isCellBlocked(float x, float y) { Cell cell = collisionLayer.getCell((int) (x / collisionLayer.getTileWidth()), (int) (y / collisionLayer.getTileHeight())); return cell != null && cell.getTile() != null && cell.getTile().getProperties().containsKey(blockedKey); } public boolean collidesRight() { for(float step = 0; step < getHeight(); step += collisionLayer.getTileHeight() / 2) if(isCellBlocked(getX() + getWidth(), getY() + step)) return true; return false; } public boolean collidesLeft() { for(float step = 0; step < getHeight(); step += collisionLayer.getTileHeight() / 2) if(isCellBlocked(getX(), getY() + step)) return true; return false; } public boolean collidesTop() { for(float step = 0; step < getWidth(); step += collisionLayer.getTileWidth() / 2) if(isCellBlocked(getX() + step, getY() + getHeight())) return true; return false; } public boolean collidesBottom() { for(float step = 0; step < getWidth(); step += collisionLayer.getTileWidth() / 2) if(isCellBlocked(getX() + step, getY())) return true; return false; } What I'm trying to achieve is simple: I'm trying to make code that will detect by all 4 sides, collidesRight + collidesLeft + collidesTop + collidesBottom in one boolean. For some reason, I cant seem to figure it out. I tried to use Rectangles (the Java Class) on the specific tile I want to be detected, but was messy and I have multiple maps. Having a Rectangle (from Java's API) around the player is no problem. It's just the tiles I want to be detected are the main issues as they cause messy code when used with the Rectangle class. Im trying to minimize the amount of code....

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• Manually writing a dx11 tessellation shader

  - by Tudor

  I am looking for resources on what are the steps of manually implementing tessellation (I'm using Unity cg). Today it seems that it is all the rage to hide most of the gpu code far away and use rather rigid simplifications such as unity's SURFace shaders. And it seems useless unless you're doing supeficial stuff. A little background: I have procedurally generated meshes (using marching cubes) which have quality normals but no UVs and no Tangents. I have successfully written a custom vertex and fragment shader to do triplanar texture and bumpmap projection as well as some custom stuff (custom lighting, procedurally warping the texture for variation etc). I am using the GPU Gems book as reference. Now I need to implement tessellation, but It seems I must calculate the tangents at runtime by swizzling normals (ctrl+f this in gems: <normal.z, normal.y, -normal.x>) before the tessellator gets them. And I also need to keep my custom vert+frag setup (with my custom parameters/textures being passed between them) - so apparently I cannot use surface shaders. Can anyone provide some guidence?

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• Tween Animation Cannot Start

  - by David Dimalanta

  Do you have any reasons why my tween code didn't run or work? I already add the tween engine onto the library folder under LibGDX project folder and "Order and Export" it under Java Build Path at the Properties menu. My first two classes ran correctly and workly but my third class didn't work. Here's the sequence: First class is the first screen. Fade animation works on the company's logo. Second class is the second screen. Fade animation for the loading screen works. Third class is the third screen. After the second screen, now calls for the third screen. Animation stopped or won't run since I want the black screen to fade out at the start when the menu is here. Can you check if I did right? Look carefully by comment lines for explanation. //-----[ Animation Setup ]----- Tween.registerAccessor(Sprite.class, new Tween_Animation()); // --> Tween_Animation.java Tween_Manager = new TweenManager(); // --> I initialized it the TweenManager and seems okay. cb_start = new TweenCallback() // --> I'll use this when I choose START and the menu will fade in black. { @Override public void onEvent(int arg0, BaseTween<?> arg1) { goTo(); } }; Tween // --> This is where I focused the problem. .to(black_Sprite, Tween_Animation.ALPHA, 3f) .target(1) .ease(TweenEquations.easeInQuad) .repeatYoyo(200, 2.5f) // --> I set the repeat for 200 times when I noticed that the animation won't work! .start(Tween_Manager);

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• How does braking assist of car racing games work?

  - by Ayush Khemka

  There are a lot of PC car racing games around which have this unique driving assist which helps brake your car so that you can safely turn it. While in some games it just an 'assist', it will just help your car brake but won't ensure a safe turn. While in others, the braking assist will help you get a safe turn. I was wondering on what could be the algorithm that is followed to achieve it. A very basic algorithm I could think of was, Pre-determine the braking distance of an ideal car for every turn of the track, depending on the radius of the turn, and then start braking the car accordingly. For example, for a turn of less than 90o, the car would start braking automatically at 50m distance from the start of the turn. A more advanced algorithm, which would ensure a safe turn, could be Pre-determine the speed of the car at the start of each turn, individually for each track, turn and car. Also, pre-determine the deceleration rate of each car individually, which varies because of the car's performance. The braking assist would keep recording the speed of the car at a certain instant of time. Start braking the car appropriately so that the car gets to the exact speed needed at the start of the turn. For example, let the speed of a particular car at the start of a turn 43m in radius, be 120km/h. Let the deceleration rate of the car be 200km/h2. If, at some instant of time, the speed of the car is 200km/h, then the car would automatically start braking at 400m from the start of the turn.

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• cocos2dx - Custom Fragment Shader and CCRenderTexture

  - by saiy2k

  I have a CCRenderTexture that is filled with a sprite when the scene is loaded, as follows, canvas = CCRenderTexture::create(this->getContentSize().width, this->getContentSize().height); canvas->setPosition(data->position); canvas->beginWithClear(0.0, 0.0, 0.0, 0); this->visit(); canvas->end(); The above code is written within a class, which derives from CCSprite (Hence this). Then, in another function applyShader(), I create a sprite named splat, from the texture of CCRenderTexture *canvas. Thus splat will contain the whole texture of canvas. Now I apply a custom fragment shader to the splat by calling the function splat->renderShader(), which will modify some small portion of the whole texture. Then I draw the modified texture back to the CCRenderTexture *canvas. Hence, applyShader() will * take a texture from CCRenderTexture, * create a sprite based on it, * apply a fragment shader to it * and draw the modified texture back to CCRenderTexture. This applyShader() will be called repetitively and its code is as follows: splat = Splat::createWithTexture(art->canvas->getSprite()->getTexture()); splat->renderShader(); art->canvas->begin(); splat->visit(); art->canvas->end(); My shader code is (nothing fancy) precision mediump float; varying vec2 v_texCoord; uniform sampler2D u_texture; uniform sampler2D u_colorRampTexture; uniform float params[5]; void main() { gl_FragColor = texture2D(u_texture, v_texCoord); return; } So, with the above code I expect the original sprite this to get rendered over and over again without any visual changes. But on each call to applyShader(), the texture is getting stretched a little and the stretched image is getting rendered. After some 10 calls, the image gets so distorted. Can someone please tell me where I am going wrong? Thanks :-) PS: All code shown here is partial, not complete code. Edit: Adding Screens Update: The problem has nothing to do with shaders it seems. It happens even when I dont call renderShader(). The actual lines of code is: splat = Splat::createWithTexture(art->canvas->getSprite()->getTexture()); splat->setPosition( ccp( art->getContentSize().width * 0.5, art->getContentSize().height * 0.5 ) ); splat->setFlipY(true); art->canvas->begin(); splat->visit(); art->canvas->end();

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• Error in destroying object in Box2D/LibGDX

  - by Crypted

  I'm trying to delete an object when a collision happens. I have put the following code in the render method of the object so it would be outside of the physics calculations. public void render(SpriteBatch spriteBatch) { // some other code... body.setActive(false); body.getWorld().destroyBody(body); But I'm getting an run-time error which crashes the JVM and shows, AL lib: alc_cleanup: 1 device not closed Assertion failed! Program: C:\Program Files\Java\jre6\bin\javaw.exe File: /var/lib/hudson/jobs/libgdx-git/workspace/gdx/jni/Box2D/Dynamics/b2World.cpp, Line 133 Expression: m_bodyCount 0 Can anyone help me here?

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• Unity - Mecanim & Rigidbody on Third Person Controller - Gravity bug?

  - by Celtc

  I'm working on a third person controller which uses physX to interact with the other objects (using the Rigidbody component) and Mecanim to animate the character. All the animations used are baked to Y, and the movement on this axis is controlled by the gravity applied by the rigidbody component. The configuration of the falling animation: And the character components configuration: Since the falling animation doesn't have root motion on XZ, I move the character on XZ by code. Like this: // On the Ground if (IsGrounded()) { GroundedMovementMgm(); // Stores the velocity velocityPreFalling = rigidbody.velocity; } // Mid-Air else { // Continue the pre falling velocity rigidbody.velocity = new Vector3(velocityPreFalling.x, rigidbody.velocity.y, velocityPreFalling.z); } The problem is that when the chracter starts falling and hit against a wall in mid air, it gets stuck to the wall. Here are some pics which explains the problems: Hope someone can help me. Thanks and sory for my bad english! PD.: I was asked for the IsGrounded() function, so I'm adding it: void OnCollisionEnter(Collision collision) { if (!grounded) TrackGrounded(collision); } void OnCollisionStay(Collision collision) { TrackGrounded(collision); } void OnCollisionExit() { grounded = false; } public bool IsGrounded() { return grounded; } private void TrackGrounded(Collision collision) { var maxHeight = capCollider.bounds.min.y + capCollider.radius * .9f; foreach (var contact in collision.contacts) { if (contact.point.y < maxHeight && Vector3.Angle(contact.normal, Vector3.up) < maxSlopeAngle) { grounded = true; break; } } } I'll also add a LINK to download the project if someone wants it.

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