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• Algorithm allowing a good waypoint path following?

  - by Thierry Savard Saucier

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

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• Coarse Collision Detection in highly dynamic environment

  - by Millianz

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

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• How to account for speed of the vehicle when shooting shells from it?

  - by John Murdoch

  I'm developing a simple 3D ship game using libgdx and bullet. When a user taps the mouse I create a new shell object and send it in the direction of the mouse click. However, if the user has tapped the mouse in the direction where the ship is currently moving, the ship catches up to the shells very quickly and can sometimes even get hit by them - simply because the speed of shells and the ship are quite comparable. I think I need to account for ship speed when generating the initial impulse for the shells, and I tried doing that (see "new line added"), but I cannot figure out if what I'm doing is the proper way and if yes, how to calculate the correct coefficient. public void createShell(Vector3 origin, Vector3 direction, Vector3 platformVelocity, float velocity) { long shellId = System.currentTimeMillis(); // hack ShellState state = getState().createShellState(shellId, origin.x, origin.y, origin.z); ShellEntity entity = EntityFactory.getInstance().createShellEntity(shellId, state); add(entity); entity.getBody().applyCentralImpulse(platformVelocity.mul(velocity * 0.02f)); // new line added, to compensate for the moving platform, no idea how to calculate proper coefficient entity.getBody().applyCentralImpulse(direction.nor().mul(velocity)); } private final Vector3 v3 = new Vector3(); public void shootGun(Vector3 direction) { Vector3 shipVelocity = world.getShipEntities().get(id).getBody().getLinearVelocity(); world.getState().getShipStates().get(id).transform.getTranslation(v3); // current location of our ship v3.add(direction.nor().mul(10.0f)); // hack; this is to avoid shell immediately impacting the ship that it got shot out from world.createShell(v3, direction, shipVelocity, 500); }

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• How do I use setFilmSize in panda3d to achieve the correct view?

  - by lhk

  I'm working with Panda3d and recently switched my game to isometric rendering. I moved the virtual camera accordingly and set an orthographic lens. Then I implemented the classes "Map" and "Canvas". A canvas is a dynamically generated mesh: a flat quad. I'm using it to render the ingame graphics. Since the game itself is still set in a 3d coordinate system I'm planning to rely on these canvases to draw sprites. I could have named this class "Tile" but as I'd like to use it for non-tile sketches (enemies, environment) as well I thought canvas would describe it's function better. Map does exactly what it's name suggests. Its constructor receives the number of rows and columns and then creates a standard isometric map. It uses the canvas class for tiles. I'm planning to write a map importer that reads a file to create maps on the fly. Here's the canvas implementation: class Canvas: def __init__(self, texture, vertical=False, width=1,height=1): # create the mesh format=GeomVertexFormat.getV3t2() format = GeomVertexFormat.registerFormat(format) vdata=GeomVertexData("node-vertices", format, Geom.UHStatic) vertex = GeomVertexWriter(vdata, 'vertex') texcoord = GeomVertexWriter(vdata, 'texcoord') # add the vertices for a flat quad vertex.addData3f(1, 0, 0) texcoord.addData2f(1, 0) vertex.addData3f(1, 1, 0) texcoord.addData2f(1, 1) vertex.addData3f(0, 1, 0) texcoord.addData2f(0, 1) vertex.addData3f(0, 0, 0) texcoord.addData2f(0, 0) prim = GeomTriangles(Geom.UHStatic) prim.addVertices(0, 1, 2) prim.addVertices(2, 3, 0) self.geom = Geom(vdata) self.geom.addPrimitive(prim) self.node = GeomNode('node') self.node.addGeom(self.geom) # this is the handle for the canvas self.nodePath=NodePath(self.node) self.nodePath.setSx(width) self.nodePath.setSy(height) if vertical: self.nodePath.setP(90) # the most important part: "Drawing" the image self.texture=loader.loadTexture(""+texture+".png") self.nodePath.setTexture(self.texture) Now the code for the Map class class Map: def __init__(self,rows,columns,size): self.grid=[] for i in range(rows): self.grid.append([]) for j in range(columns): # create a canvas for the tile. For testing the texture is preset tile=Canvas(texture="../assets/textures/flat_concrete",width=size,height=size) x=(i-1)*size y=(j-1)*size # set the tile up for rendering tile.nodePath.reparentTo(render) tile.nodePath.setX(x) tile.nodePath.setY(y) # and store it for later access self.grid[i].append(tile) And finally the usage def loadMap(self): self.map=Map(10, 10, 1) this function is called within the constructor of the World class. The instantiation of world is the entry point to the execution. The code is pretty straightforward and runs good. Sadly the output is not as expected: Please note: The problem is not the white rectangle, it's my player object. The problem is that although the map should have equal width and height it's stretched weirdly. With orthographic rendering I expected the map to be a perfect square. What did I do wrong ? UPDATE: I've changed the viewport. This is how I set up the orthographic camera: lens = OrthographicLens() lens.setFilmSize(40, 20) base.cam.node().setLens(lens) You can change the "aspect" by modifying the parameters of setFilmSize. I don't know exactly how they are related to window size and screen resolution but after testing a little the values above seem to work for me. Now everything is rendered correctly as long as I don't resize the window. Every change of the window's size as well as switching to fullscreen destroys the correct rendering. I know that implementing a listener for resize events is not in the scope of this question. However I wonder why I need to make the Film's height two times bigger than its width. My window is quadratic ! Can you tell me how to find out correct setting for the FilmSize ? UPDATE 2: I can imagine that it's hard to envision the behaviour of the game. At first glance the obvious solution is to pass the window's width and height in pixels to setFilmSize. There are two problems with that approach. The parameters for setFilmSize are ingame units. You'll get a way to big view if you pass the pixel size For some strange reason the image is distorted if you pass equal values for width and height. Here's the output for setFilmSize(800,800) You'll have to stress your eyes but you'll see what I mean

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• How to handle wildly varying rendering hardware / getting baseline

  - by edA-qa mort-ora-y

  I've recently started with mobile programming (cross-platform, also with desktop) and am encountering wildly differing hardware performance, in particular with OpenGL and the GPU. I know I'll basically have to adjust my rendering code but I'm uncertain of how to detect performance and what reasonable default settings are. I notice that certain shader functions are basically free in a desktop implemenation but can be unusable in a mobile device. The problem is I have no way of knowing what features will cause what performance issues on all the devices. So my first issue is that even if I allow configuring options I'm uncertain of which options I have to make configurable. I'm wondering also wheher one just writes one very configurable pipeline, or whether I should have 2 distinct options (high/low). I'm also unsure of where to set the default. If I set to the poorest performer the graphics will be so minimal that any user with a modern device would dismiss the game. If I set them even at some moderate point, the low end devices will basically become a slide-show. I was thinking perhaps that I just run some benchmarks when the user first installs and randomly guess what works, but I've not see a game do this before.

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• Secure login for a game that is open source

  - by David Park

  I am making a game which i will be open sourcing. Its a simple arcade like game but requires a network connection because it is meant to be played with other people. The thing i am worrying about is how would i be sure that the client is the one that i put out for the end user to play with? Kind of a like of sv_pure for Team Fortress 2. I was thinking of different ways to combat this such as the server requesting the client's version or even it's md5 hash but people with simple java knowledge could just force a method to always return what the server wants.

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• Why do meshes show up as bones in the Model class?

  - by Itamar Marom

  Right now I'm working on a 3D game and I've come across something very weird. When I created the model in Blender, I added an armature named "MyBone" to the stage and attached a cube ("MyCube") to it, so that when I move the armature, the cube moves with it. I exported this as an FBX and loaded it as a Model object. What I expected to see was: But what I got was this: I'm really confused. Why is the mesh I created showing up in the bone list? And what's Root Node? Here are the .blend and .fbx files: here or here. Thanks.

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• Struggling to get set up with JOGL2.0

  - by thecoshman

  I guess that Game Dev' is a more sensible place for my problem then SO. I did have JOGL1.1 set up and working, but I soon discovered that it did not support the latest OpenGL, so I started work on upgrading to JOGL2.0 it's not gone too well. Firstly, is it worth me trying to get JOGL to work, or should I just move over to LWJGL? I am fairly comfortable with OpenGL (via C++) and from what I did get working with JOGL1.1, I seem to be OK adapting to it. Assuming that I stick with JOGL, am I foolish for trying to use JOGL2.0? From what I can gather, JOGL2.0 is still in beta, but I am willing to go with it as I want to make use of the latest OpenGL I can. I have been using the Eclipse IDE and have set up a user library for JOGL, here is a screen shot of the configuration and I have added this user library to my own Eclipse project. the system variable %JOGL_HOME% points to "C:\Users\edacosh\Downloads\JOGL2.0" so that should work fine. Now, the problem I actually having, when I try to run my code, on the line GLProfile glp = GLProfile.getDefault(); The code stops with the following message... Exception in thread "main" java.lang.NoClassDefFoundError: com/jogamp/common/jvm/JVMUtil at javax.media.opengl.GLProfile.<clinit>(GLProfile.java:1145) at DiCE.DiCE.<init>(DiCE.java:33) at App.<init>(App.java:17) at App.main(App.java:12) Caused by: java.lang.ClassNotFoundException: com.jogamp.common.jvm.JVMUtil at java.net.URLClassLoader$1.run(Unknown Source) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(Unknown Source) at java.lang.ClassLoader.loadClass(Unknown Source) at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source) at java.lang.ClassLoader.loadClass(Unknown Source) ... 4 more I have also set my project to ensure that it is using jre6 along with jdk6, as I was having some issues. I hope I have given you enough information to be able to help me. It probably doesn't help that I am rather new to Java, been developing in C++ for ages. Thanks

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• Illumination and Shading for computer graphics class

  - by Sam I Am

  I am preparing for my test tomorrow and this is one of the practice questions. I solved it partially but I am confused with the rest. Here is the problem: Consider a gray world with no ambient and specular lighting ( only diffuse lighting). The screen coordinates of a triangle P1,P2,P3, are P1=(100,100), P2= (300,150), P3 = (200, 200). The gray values at P!,P2,P3 are 1/2, 3/4, and 1/4 respectively. The light is at infinity and its direction and gray color are (1,1,1) and 1.0 respectively. The coefficients of diffused reflection is 1/2. The normals of P1,P2,P3 are N1= (0,0,1), N2 = (1,0,0), and N3 = (0,1,0) respectively. Consider the coordinates of three points P1,P2,P3 to be 0. Do not normalize the normals. I have computed that the illumination at the 3 vertices P1,P2,P3 is (1/4,3/8,1/8). Also I computed that interpolation coefficients of a point P inside the triangle whose coordinates are (220, 160) are given by (1/5,2/5,2/5). Now I have 4 more questions regarding this problem. 1) The illumination at P using Gouraud Shading is: i) 1/2 The answer is 1/2, but I have no idea how to compute it.. 2) The interpolated normal at P is given by i) (2/5, 2/5,1/5) ii) (1/2, 1/4, 1/4) iii) (3/5, 1/5, 1/5) 3) The interpolated color at P is given by: i) 1/2 Again, I know the correct answer but no idea how to solve it 4) The illumination at P using Phong Shading is i) 1/4 ii) 9/40 iii) 1/2

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• Cool examples of procedural pixel shader effects?

  - by Robert Fraser

  What are some good examples of procedural/screen-space pixel shader effects? No code necessary; just looking for inspiration. In particular, I'm looking for effects that are not dependent on geometry or the rest of the scene (would look okay rendered alone on a quad) and are not image processing (don't require a "base image", though they can incorporate textures). Multi-pass or single-pass is fine. Screenshots or videos would be ideal, but ideas work too. Here are a few examples of what I'm looking for (all from the RenderMonkey samples): PS - I'm aware of this question; I'm not asking for a source of actual shader implementations but instead for some inspirational ideas -- and the ones at the NVIDIA Shader Library mostly require a scene or are image processing effects. EDIT: this is an open-ended question and I wish there was a good way to split the bounty. I'll award the rep to the best answer on the last day.

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• Maya .IFF plugins for Gimp

  - by Kara Marfia

  Maya's preferred format for saving off a UV Snapshot is its own .IFF format, so I was hoping to find a plugin allowing Gimp 2 (Windows) to read it. I've found plenty of plugins for different linux distros, but none are win-friendly (that I can discern - admittedly I'm no whiz with Gimp). Does anyone know of one? Alternately, .tiff seems to work just fine, so if there's no good reason to bother fiddling with IFFs, I'd appreciate the input there, too. (sorry if this isn't on-topic)

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• 3Ds Max is exporting model with more normals than vertices

  - by Delta

  I made a simple teapot with the "Create Standard Primitives" option and exported it as a collada file, ended up with this: < float_array id="Teapot001-POSITION-array" count="1590" < float_array id="Teapot001-Normal0-array" count="9216" For what I know there should be only one normal per vertex, am I wrong? What am I supposed to do with that much normals? Just put them on the normal buffer all at once normally?

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• GoogleAppEngine : ClassNotFoundException : javax.jdo.metadata.ComponentMetadata

  - by James.Elsey

  I'm trying to deploy my application to a locally running GoogleAppEngine development server, but I'm getting the following stack trace when I start the server Apr 23, 2010 9:03:33 PM com.google.apphosting.utils.jetty.JettyLogger warn WARNING: Nested in org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'clientDao' defined in ServletContext resource [/WEB-INF/applicationContext.xml]: Cannot resolve reference to bean 'entityManagerFactory' while setting bean property 'entityManagerFactory'; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'entityManagerFactory' defined in ServletContext resource [/WEB-INF/applicationContext.xml]: Invocation of init method failed; nested exception is java.lang.NoClassDefFoundError: javax/jdo/metadata/ComponentMetadata: java.lang.ClassNotFoundException: javax.jdo.metadata.ComponentMetadata at java.net.URLClassLoader$1.run(URLClassLoader.java:217) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(URLClassLoader.java:205) at java.lang.ClassLoader.loadClass(ClassLoader.java:319) at com.google.appengine.tools.development.IsolatedAppClassLoader.loadClass(IsolatedAppClassLoader.java:151) at java.lang.ClassLoader.loadClass(ClassLoader.java:264) at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:332) at java.lang.Class.forName0(Native Method) at java.lang.Class.forName(Class.java:264) at javax.jdo.JDOHelper$18.run(JDOHelper.java:2009) at javax.jdo.JDOHelper$18.run(JDOHelper.java:2007) at java.security.AccessController.doPrivileged(Native Method) at javax.jdo.JDOHelper.forName(JDOHelper.java:2006) at javax.jdo.JDOHelper.invokeGetPersistenceManagerFactoryOnImplementation(JDOHelper.java:1155) at javax.jdo.JDOHelper.getPersistenceManagerFactory(JDOHelper.java:803) at javax.jdo.JDOHelper.getPersistenceManagerFactory(JDOHelper.java:698) at org.datanucleus.jpa.EntityManagerFactoryImpl.initialisePMF(EntityManagerFactoryImpl.java:482) at org.datanucleus.jpa.EntityManagerFactoryImpl.<init>(EntityManagerFactoryImpl.java:255) at org.datanucleus.store.appengine.jpa.DatastoreEntityManagerFactory.<init>(DatastoreEntityManagerFactory.java:68) at org.datanucleus.store.appengine.jpa.DatastorePersistenceProvider.createContainerEntityManagerFactory(DatastorePersistenceProvider.java:45) at org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean.createNativeEntityManagerFactory(LocalContainerEntityManagerFactoryBean.java:224) at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.afterPropertiesSet(AbstractEntityManagerFactoryBean.java:291) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1369) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1335) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:473) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory$1.run(AbstractAutowireCapableBeanFactory.java:409) at java.security.AccessController.doPrivileged(Native Method) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:380) at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:264) at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222) at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:261) at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:185) at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:164) at org.springframework.beans.factory.support.BeanDefinitionValueResolver.resolveReference(BeanDefinitionValueResolver.java:269) at org.springframework.beans.factory.support.BeanDefinitionValueResolver.resolveValueIfNecessary(BeanDefinitionValueResolver.java:104) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.applyPropertyValues(AbstractAutowireCapableBeanFactory.java:1245) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1010) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:472) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory$1.run(AbstractAutowireCapableBeanFactory.java:409) at java.security.AccessController.doPrivileged(Native Method) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:380) at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:264) at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222) at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:261) at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:185) at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:164) at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:429) at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:728) at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:380) at org.springframework.web.context.ContextLoader.createWebApplicationContext(ContextLoader.java:255) at org.springframework.web.context.ContextLoader.initWebApplicationContext(ContextLoader.java:199) at org.springframework.web.context.ContextLoaderListener.contextInitialized(ContextLoaderListener.java:45) at org.mortbay.jetty.handler.ContextHandler.startContext(ContextHandler.java:530) at org.mortbay.jetty.servlet.Context.startContext(Context.java:135) at org.mortbay.jetty.webapp.WebAppContext.startContext(WebAppContext.java:1218) at org.mortbay.jetty.handler.ContextHandler.doStart(ContextHandler.java:500) at org.mortbay.jetty.webapp.WebAppContext.doStart(WebAppContext.java:448) at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:40) at org.mortbay.jetty.handler.HandlerWrapper.doStart(HandlerWrapper.java:117) at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:40) at org.mortbay.jetty.handler.HandlerWrapper.doStart(HandlerWrapper.java:117) at org.mortbay.jetty.Server.doStart(Server.java:217) at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:40) at com.google.appengine.tools.development.JettyContainerService.startContainer(JettyContainerService.java:181) at com.google.appengine.tools.development.AbstractContainerService.startup(AbstractContainerService.java:116) at com.google.appengine.tools.development.DevAppServerImpl.start(DevAppServerImpl.java:217) at com.google.appengine.tools.development.DevAppServerMain$StartAction.apply(DevAppServerMain.java:162) at com.google.appengine.tools.util.Parser$ParseResult.applyArgs(Parser.java:48) at com.google.appengine.tools.development.DevAppServerMain.<init>(DevAppServerMain.java:113) at com.google.appengine.tools.development.DevAppServerMain.main(DevAppServerMain.java:89) The server is running at http://localhost:1234/ I'm a little confused over this, since I have the same application running locally on GlassFish/MySQL. All I have done is to swap in the relevant jar files, and change the persistence.xml. My applicationContext.xml looks as follows : <context:annotation-config/> <bean id="clientDao" class="com.jameselsey.salestracker.dao.jpa.JpaDaoClient"> <property name="entityManagerFactory" ref="entityManagerFactory"/> </bean> <bean id="entityManagerFactory" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean"/> <bean id="transactionManager" class="org.springframework.orm.jpa.JpaTransactionManager"> <property name="entityManagerFactory" ref="entityManagerFactory" /> </bean> <bean id="org.springframework.context.annotation.internalPersistenceAnnotationProcessor" class="com.jameselsey.salestracker.util.GaeFixInternalPersistenceAnnotationProcessor" /> <bean class="org.springframework.orm.jpa.support.PersistenceAnnotationBeanPostProcessor"/> <tx:annotation-driven/> <bean id="clientService" class="com.jameselsey.salestracker.service.ClientService"/> </beans> My JPA DAO looks like this public class JpaDao extends JpaDaoSupport { protected <T> List<T> findAll(Class<T> clazz) { return getJpaTemplate().find("select c from " + clazz.getName() + " c"); } protected <T> T findOne(String jpql, Map params) { List<T> results = getJpaTemplate().findByNamedParams(jpql, params); if(results.isEmpty()) { return null; } if(results.size() > 1) { throw new IncorrectResultSizeDataAccessException(1, results.size()); } return results.get(0); } } And an example implemented method looks like this : @Override public Client getClientById(Integer clientId) { String jpql = "SELECT c " + "FROM com.jameselsey.salestracker.domain.Client c " + "WHERE c.id = " + clientId; return (Client) getJpaTemplate().find(jpql).get(0); } Like I say, this works ok on Glassfish/MySQL, is it possible this error could be a red herring to something else?

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• runtime error: invalid memory address or nil pointer dereference

  - by Klink

  I want to learn OpenGL 3.0 with golang. But when i try to compile some code, i get many errors. package main import ( "os" //"errors" "fmt" //gl "github.com/chsc/gogl/gl33" //"github.com/jteeuwen/glfw" "github.com/go-gl/gl" "github.com/go-gl/glfw" "runtime" "time" ) var ( width int = 640 height int = 480 ) var ( points = []float32{0.0, 0.8, -0.8, -0.8, 0.8, -0.8} ) func initScene() { gl.Init() gl.ClearColor(0.0, 0.5, 1.0, 1.0) gl.Enable(gl.CULL_FACE) gl.Viewport(0, 0, 800, 600) } func glfwInitWindowContext() { if err := glfw.Init(); err != nil { fmt.Fprintf(os.Stderr, "glfw_Init: %s\n", err) glfw.Terminate() } glfw.OpenWindowHint(glfw.FsaaSamples, 1) glfw.OpenWindowHint(glfw.WindowNoResize, 1) if err := glfw.OpenWindow(width, height, 0, 0, 0, 0, 32, 0, glfw.Windowed); err != nil { fmt.Fprintf(os.Stderr, "glfw_Window: %s\n", err) glfw.CloseWindow() } glfw.SetSwapInterval(1) glfw.SetWindowTitle("Title") } func drawScene() { for glfw.WindowParam(glfw.Opened) == 1 { gl.Clear(gl.COLOR_BUFFER_BIT) vertexShaderSrc := `#version 120 attribute vec2 coord2d; void main(void) { gl_Position = vec4(coord2d, 0.0, 1.0); }` vertexShader := gl.CreateShader(gl.VERTEX_SHADER) vertexShader.Source(vertexShaderSrc) vertexShader.Compile() fragmentShaderSrc := `#version 120 void main(void) { gl_FragColor[0] = 0.0; gl_FragColor[1] = 0.0; gl_FragColor[2] = 1.0; }` fragmentShader := gl.CreateShader(gl.FRAGMENT_SHADER) fragmentShader.Source(fragmentShaderSrc) fragmentShader.Compile() program := gl.CreateProgram() program.AttachShader(vertexShader) program.AttachShader(fragmentShader) program.Link() attribute_coord2d := program.GetAttribLocation("coord2d") program.Use() //attribute_coord2d.AttribPointer(size, typ, normalized, stride, pointer) attribute_coord2d.EnableArray() attribute_coord2d.AttribPointer(0, 3, false, 0, &(points[0])) //gl.DrawArrays(gl.TRIANGLES, 0, len(points)) gl.DrawArrays(gl.TRIANGLES, 0, 3) glfw.SwapBuffers() inputHandler() time.Sleep(100 * time.Millisecond) } } func inputHandler() { glfw.Enable(glfw.StickyKeys) if glfw.Key(glfw.KeyEsc) == glfw.KeyPress { //gl.DeleteBuffers(2, &uiVBO[0]) glfw.Terminate() } if glfw.Key(glfw.KeyF2) == glfw.KeyPress { glfw.SetWindowTitle("Title2") fmt.Println("Changed to 'Title2'") fmt.Println(len(points)) } if glfw.Key(glfw.KeyF1) == glfw.KeyPress { glfw.SetWindowTitle("Title1") fmt.Println("Changed to 'Title1'") } } func main() { runtime.LockOSThread() glfwInitWindowContext() initScene() drawScene() } And after that: panic: runtime error: invalid memory address or nil pointer dereference [signal 0xb code=0x1 addr=0x0 pc=0x41bc6f74] goroutine 1 [syscall]: github.com/go-gl/gl._Cfunc_glDrawArrays(0x4, 0x7f8500000003) /tmp/go-build463568685/github.com/go-gl/gl/_obj/_cgo_defun.c:610 +0x2f github.com/go-gl/gl.DrawArrays(0x4, 0x3, 0x0, 0x45bd70) /tmp/go-build463568685/github.com/go-gl/gl/_obj/gl.cgo1.go:1922 +0x33 main.drawScene() /home/klink/Dev/Go/gogl/gopher/exper.go:85 +0x1e6 main.main() /home/klink/Dev/Go/gogl/gopher/exper.go:116 +0x27 goroutine 2 [syscall]: created by runtime.main /build/buildd/golang-1/src/pkg/runtime/proc.c:221 exit status 2

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• Calculating instantaneous speed and acceleration for a simple Car software model

  - by Dylan

  I am trying to model a speedometer and tachometer for a simple software model of a car dashboard. I want this to be relatively simple, so for my purposes I won't likely simulate variables such as drag (or, assume that drag is a constant). But I would like to know the general formulas for: 1) Calculating the RPM, depending on a position of a graphical slider representing the accelerator. 2) Using this information to find the instantaneous speed (or, magnitude of instantaneous velocity?). I am not sure, in the case of 2), what other independent variables I need to consider. Do I need to consider the frequency of rotation of the wheels (assuming a fixed radius), in addition to the RPM? If anyone can give me a rough explanation plus relevant formulas, or alternatively direct me to other trusted resources online (I have had a hard time sifting through info and determining the accuracy), it would be much appreciated.

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• Ruby: implementing alpha-beta pruning for tic-tac-toe

  - by DerNalia

  So, alpha-beta pruning seems to be the most efficient algorithm out there aside from hard coding (for tic tac toe). However, I'm having problems converting the algorithm from the C++ example given in the link: http://www.webkinesia.com/games/gametree.php #based off http://www.webkinesia.com/games/gametree.php # (converted from C++ code from the alpha - beta pruning section) # returns 0 if draw LOSS = -1 DRAW = 0 WIN = 1 @next_move = 0 def calculate_ai_next_move score = self.get_best_move(COMPUTER, WIN, LOSS) return @next_move end def get_best_move(player, alpha, beta) best_score = nil score = nil if not self.has_available_moves? return false elsif self.has_this_player_won?(player) return WIN elsif self.has_this_player_won?(1 - player) return LOSS else best_score = alpha NUM_SQUARES.times do |square| if best_score >= beta break end if self.state[square].nil? self.make_move_with_index(square, player) # set to negative of opponent's best move; we only need the returned score; # the returned move is irrelevant. score = -get_best_move(1-player, -beta, -alpha) if (score > bestScore) @next_move = square best_score = score end undo_move(square) end end end return best_score end the problem is that this is returning nil. some support methods that are used above: WAYS_TO_WIN = [[0, 1, 2], [3, 4, 5], [6, 7, 8], [0, 3, 6], [1, 4, 7], [2, 5, 8],[0, 4, 8], [2, 4, 6]] def has_this_player_won?(player) result = false WAYS_TO_WIN.each {|solution| result = self.state[solution[0]] if contains_win?(solution) } return (result == player) end def contains_win?(ttt_win_state) ttt_win_state.each do |pos| return false if self.state[pos] != self.state[ttt_win_state[0]] or self.state[pos].nil? end return true end def make_move(x, y, player) self.set_square(x,y, player) end

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• Shader optimization - cg/hlsl pseudo and via multiplication

  - by teodron

  Since HLSL/Cg do not allow texture fetching inside conditional blocks, I am first checking a variable and performing some computations, afterwards setting a float flag to 0.0 or 1.0, depending on the computations. I'd like to trigger a texture fetch only if the flag is 1.0 or not null, for that matter of fact. I kind of hoped this would do the trick: float4 TU0_atlas_colour = pseudoBool * tex2Dlod(TU0_texture, float4(tileCoord, 0, mipLevel)); That is, if pseudoBool is 0, will the texture fetch function still be called and produce overhead? I was hoping to prevent it from getting executed via this trick that usually works in plain C/C++.

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• Client side latency when using prediction

  - by Tips48

  I've implemented Client-Side prediction into my game, where when input is received by the client, it first sends it to the server and then acts upon it just as the server will, to reduce the appearance of lag. The problem is, the server is authoritative, so when the server sends back the position of the Entity to the client, it undo's the effect of the interpolation and creates a rubber-banding effect. For example: Client sends input to server - Client reacts on input - Server receives and reacts on input - Server sends back response - Client reaction is undone due to latency between server and client To solve this, I've decided to store the game state and input every tick in the client, and then when I receive a packet from the server, get the game state from when the packet was sent and simulate the game up to the current point. My questions: Won't this cause lag? If I'm receiving 20/30 EntityPositionPackets a second, that means I have to run 20-30 simulations of the game state. How do I sync the client and server tick? Currently, I'm sending the milli-second the packet was sent by the server, but I think it's adding too much complexity instead of just sending the tick. The problem with converting it to sending the tick is that I have no guarantee that the client and server are ticking at the same rate, for example if the client is an old-end PC.

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• How do I simplify terrain with tunnels or overhangs?

  - by KKlouzal

  I'm attempting to store vertex data in a quadtree with C++, such that far-away vertices can be combined to simplify the object and speed up rendering. This works well with a reasonably flat mesh, but what about terrain with overhangs or tunnels? How should I represent such a mesh in a quadtree? After the initial generation, each mesh is roughly 130,000 polygons and about 300 of these meshes are lined up to create the surface of a planetary body. A fully generated planet is upwards of 10,000,000 polygons before applying any culling to the individual meshes. Therefore, this second optimization is vital for the project. The rest of my confusion focuses around my inexperience with vertex data: How do I properly loop through the vertex data to group them into specific quads? How do I conclude from vertex data what a quad's maximum size should be? How many quads should the quadtree include?

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• Maintaining State in Mud Engine

  - by Johnathon Sullinger

  I am currently working on a Mud Engine and have started implementing my state engine. One of the things that has me troubled is maintaining different states at once. For instance, lets say that the user has started a tutorial, which requires specific input. If the user types "help" I want to switch in to a help state, so they can get the help they need, then return them to the original state once exiting the help. my state system uses a State Manager to manage the state per user: public class StateManager { /// <summary> /// Gets the current state. /// </summary> public IState CurrentState { get; private set; } /// <summary> /// Gets the states available for use. /// </summary> /// <value> public List<IState> States { get; private set; } /// <summary> /// Gets the commands available. /// </summary> public List<ICommand> Commands { get; private set; } /// <summary> /// Gets the mob that this manager controls the state of. /// </summary> public IMob Mob { get; private set; } public void Initialize(IMob mob, IState initialState = null) { this.Mob = mob; if (initialState != null) { this.SwitchState(initialState); } } /// <summary> /// Performs the command. /// </summary> /// <param name="message">The message.</param> public void PerformCommand(IMessage message) { if (this.CurrentState != null) { ICommand command = this.CurrentState.GetCommand(message); if (command is NoOpCommand) { // NoOperation commands indicate that the current state is not finished yet. this.CurrentState.Render(this.Mob); } else if (command != null) { command.Execute(this.Mob); } else if (command == null) { new InvalidCommand().Execute(this.Mob); } } } /// <summary> /// Switches the state. /// </summary> /// <param name="state">The state.</param> public void SwitchState(IState state) { if (this.CurrentState != null) { this.CurrentState.Cleanup(); } this.CurrentState = state; if (state != null) { this.CurrentState.Render(this.Mob); } } } Each of the different states that the user can be in, is a Type implementing IState. public interface IState { /// <summary> /// Renders the current state to the players terminal. /// </summary> /// <param name="player">The player to render to</param> void Render(IMob mob); /// <summary> /// Gets the Command that the player entered and preps it for execution. /// </summary> /// <returns></returns> ICommand GetCommand(IMessage command); /// <summary> /// Cleanups this instance during a state change. /// </summary> void Cleanup(); } Example state: public class ConnectState : IState { /// <summary> /// The connected player /// </summary> private IMob connectedPlayer; public void Render(IMob mob) { if (!(mob is IPlayer)) { throw new NullReferenceException("ConnectState can only be used with a player object implementing IPlayer"); } //Store a reference for the GetCommand() method to use. this.connectedPlayer = mob as IPlayer; var server = mob.Game as IServer; var game = mob.Game as IGame; // It is not guaranteed that mob.Game will implement IServer. We are only guaranteed that it will implement IGame. if (server == null) { throw new NullReferenceException("LoginState can only be set to a player object that is part of a server."); } //Output the game information mob.Send(new InformationalMessage(game.Name)); mob.Send(new InformationalMessage(game.Description)); mob.Send(new InformationalMessage(string.Empty)); //blank line //Output the server MOTD information mob.Send(new InformationalMessage(string.Join("\n", server.MessageOfTheDay))); mob.Send(new InformationalMessage(string.Empty)); //blank line mob.StateManager.SwitchState(new LoginState()); } /// <summary> /// Gets the command. /// </summary> /// <param name="message">The message.</param> /// <returns>Returns no operation required.</returns> public Commands.ICommand GetCommand(IMessage message) { return new NoOpCommand(); } /// <summary> /// Cleanups this instance during a state change. /// </summary> public void Cleanup() { // We have nothing to clean up. return; } } With the way that I have my FSM set up at the moment, the user can only ever have one state at a time. I read a few different posts on here about state management but nothing regarding keeping a stack history. I thought about using a Stack collection, and just pushing new states on to the stack then popping them off as the user moves out from one. It seems like it would work, but I'm not sure if it is the best approach to take. I'm looking for recommendations on this. I'm currently swapping state from within the individual states themselves as well which I'm on the fence about if it makes sense to do there or not. The user enters a command, the StateManager passes the command to the current State and lets it determine if it needs it (like passing in a password after entering a user name), if the state doesn't need any further commands, it returns null. If it does need to continue doing work, it returns a No Operation to let the state manager know that the state still requires further input from the user. If null is returned, the state manager will then go find the appropriate state for the command entered by the user. Example state requiring additional input from the user public class LoginState : IState { /// <summary> /// The connected player /// </summary> private IPlayer connectedPlayer; private enum CurrentState { FetchUserName, FetchPassword, InvalidUser, } private CurrentState currentState; /// <summary> /// Renders the current state to the players terminal. /// </summary> /// <param name="mob"></param> /// <exception cref="System.NullReferenceException"> /// ConnectState can only be used with a player object implementing IPlayer /// or /// LoginState can only be set to a player object that is part of a server. /// </exception> public void Render(IMob mob) { if (!(mob is IPlayer)) { throw new NullReferenceException("ConnectState can only be used with a player object implementing IPlayer"); } //Store a reference for the GetCommand() method to use. this.connectedPlayer = mob as IPlayer; var server = mob.Game as IServer; // Register to receive new input from the user. mob.ReceivedMessage += connectedPlayer_ReceivedMessage; if (server == null) { throw new NullReferenceException("LoginState can only be set to a player object that is part of a server."); } this.currentState = CurrentState.FetchUserName; switch (this.currentState) { case CurrentState.FetchUserName: mob.Send(new InputMessage("Please enter your user name")); break; case CurrentState.FetchPassword: mob.Send(new InputMessage("Please enter your password")); break; case CurrentState.InvalidUser: mob.Send(new InformationalMessage("Invalid username/password specified.")); this.currentState = CurrentState.FetchUserName; mob.Send(new InputMessage("Please enter your user name")); break; } } /// <summary> /// Receives the players input. /// </summary> /// <param name="sender">The sender.</param> /// <param name="e">The e.</param> void connectedPlayer_ReceivedMessage(object sender, IMessage e) { // Be good memory citizens and clean ourself up after receiving a message. // Not doing this results in duplicate events being registered and memory leaks. this.connectedPlayer.ReceivedMessage -= connectedPlayer_ReceivedMessage; ICommand command = this.GetCommand(e); } /// <summary> /// Gets the Command that the player entered and preps it for execution. /// </summary> /// <param name="command"></param> /// <returns>Returns the ICommand specified.</returns> public Commands.ICommand GetCommand(IMessage command) { if (this.currentState == CurrentState.FetchUserName) { this.connectedPlayer.Name = command.Message; this.currentState = CurrentState.FetchPassword; } else if (this.currentState == CurrentState.FetchPassword) { // find user } return new NoOpCommand(); } /// <summary> /// Cleanups this instance during a state change. /// </summary> public void Cleanup() { // If we have a player instance, we clean up the registered event. if (this.connectedPlayer != null) { this.connectedPlayer.ReceivedMessage -= this.connectedPlayer_ReceivedMessage; } } Maybe my entire FSM isn't wired up in the best way, but I would appreciate input on what would be the best to maintain a stack of state in a MUD game engine, and if my states should be allowed to receive the input from the user or not to check what command was entered before allowing the state manager to switch states. Thanks in advance.

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• Logarithmic spacing of FFT bins

  - by Mykel Stone

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

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• (Quaternion based) Trouble moving foward based on model rotation

  - by ChocoMan

  Using quaternions, I'm having trouble moving my model in its facing direction. Currently the model moves can move in all cardinal directions with no problems. The problem comes when I rotate the move as it still travelling in the direction of world space. Meaning, if I'm moving forward, backward or any other direction while rotating the model, the model acts like its a figure skater spinning while traveling in the same direction. How do I update the direction of travel proper with the facing direction of the model? Rotates model on Y-axis: Yaw = pController.ThumbSticks.Right.X * MathHelper.ToRadians(speedAngleMAX); AddRotation = Quaternion.CreateFromYawPitchRoll(yaw, 0, 0); ModelLoad.MRotation *= AddRotation; MOrientation = Matrix.CreateFromQuaternion(ModelLoad.MRotation); Moves model forward: // Move Forward if (pController.IsButtonDown(Buttons.LeftThumbstickUp)) { SpeedX = (float)(Math.Sin(ModelLoad.ModelRotation)) * FWDSpeedMax * pController.ThumbSticks.Left.Y * (float)gameTime.ElapsedGameTime.TotalSeconds; SpeedZ = (float)(Math.Cos(ModelLoad.ModelRotation)) * FWDSpeedMax * pController.ThumbSticks.Left.Y * (float)gameTime.ElapsedGameTime.TotalSeconds; // Update model position ModelLoad._modelPos += Vector3.Forward * SpeedZ; ModelLoad._modelPos += Vector3.Left * SpeedX; }

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• Making a game "resize-safe"

  - by CPP_Person

  It's one thing to get the graphics aligned perfectly, it's another to do this for every single resolution and not take too much time and/or make the code unreadable due to size. Games like Battlefield 3 and Minecraft seem to manage this. But what do they do to keep things from stretching or going off the screen? I don't know any algorithms to do this. I'd like some help on this topic. I've always programmed games that only handle a single resolution, so help would be appreciate.

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• accessing c++ class members with luaplus

  - by cppanda

  i've implemented LuaPlus in my engine eventmanager successfully and really like the flexibility i gained. but i'm still not exactly where i want to by, because i can't link my c++ classes to a lua class. for example i have a Actor class in c++, and i want to be able to create the same class in lua and gain access to members with luaplus, but i can't figure how i can achieve that. Is this actually luaplus built in functionality, or do i have to write my own interface that exchanges data tables between c++ and lua? my current approach would be to fire an event in luascript that creates an new actor class in c++ code, and transfer its id and the data i need to back to lua. when i modify the data i send the modifications back to c++ code again, but i actually thought there's something in luaplus that exposes this functionality already.

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• Low coupling and tight cohesion

  - by hidayat

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

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