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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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• 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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• 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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• Realistic planetary terrain generation with weights

  - by Programmdude

  I need terrain generation for a planet. The planet will be divided up into several hundred hexes, and I need it to be realistic and based on weights. I have dabbled in terrain generation before, but nothing like this. So I figure it would be a good idea to ask the community for answers, recommended articles or the like. By realistic, I mean not just random hexes, but continent shaped things with a few islands. More desert around the equator and more ice around the poles. I also have two weights I need to base it around: ice percentage and water percentage. That means that around XX% of the planet will need to be water. Does anyone have any advice or places to start? Generating arbitrary terrain is easy, but something a bit more "organic" like this seems rather difficult. It also needs to be seamless. Should be obvious since it's a planet, but no harm in pointing it out.

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• Structure gameobjects and call events

  - by waco001

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

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• Map building - Tower Defense

  - by Dan K

  Before diving too deep into my question, let it be known that I am learning as far as java script goes and figured a simple Tower Defense game would be an excellent way to learn things. So I have found a simple background image with a path drawn on it and my question is how would I go about building a path so that I can animate my objects. Would I have to take the image and overlay a grid system, or can I store the path in some sort of array and have my objects move across it? Here is the background image:

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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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• Group arrival steering

  - by ltjax

  I've got group movement implemented pretty much like this: http://www.red3d.com/cwr/steer/CrowdPath.html Basically, that's combining path following and separation. It works nicely as long as units are in transit, but arrival does not work very well at all. Right now, units just cease to use the path following component once the "exit" the path, i.e. when their closest point on the path is on or past the end. This leads to those units bumping into each other and also overshooting the point the player clicked. Ideally, I'd have the units arrive scattered around the finish point (and reasonable close to each other), not all clumped up past the finish line. I'd imagine that some kind of arrival steering might work here, but based on other units and a "fuzzy" classification of the end of the path. Is there any proven way to do this?

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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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• Which are the cons of using only non-member functions and POD?

  - by Miro

  I'm creating my own game engine. I've read these articles and this question about DOD and it was written to not use member functions and classes. I also heard some criticism to this idea. I can write it using member functions or non-member functions it would be similar. So what are the benefits/cons of that approach or when the project grows, does any of these approaches give clearer and better manageable code? With POD & non-member functions I don't have to make struct members public I can still use object id outside of engine like OpenGL does with all it's stuff, so It's not about encapsulation. POD - plain old data DOD - data oriented design

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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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• 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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• 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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• 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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• Correct Rotation and Translation with a 4x4 matrix

  - by sFuller

  I am using a 4x4 matrix to transform verts in a shader. I multiply an identity matrix by a rotation matrix by a translation matrix. I am trying to first rotate the verts and then translate them, however in my result, it appears that the verts are being transformed and then rotated. My matrix looks something like this: m00 m01 m02 tx m10 m11 m12 ty m20 m21 m22 tz --- --- --- 1 I am not using OpenGL's fixed function pipeline, I am multiplying matrices on the client side, and uploading the matrix to a GLSL shader. If it helps, I am using my own matrix multiplication code, but I have recreated this problem using matrices on my graphing calculator, so I don't believe my matrix code has errors.. I'll include a visual aid if needed.

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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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• Largest sphere inside a frustum

  - by Will

  How do you find the largest sphere that you can draw in perspective? Viewed from the top, it'd be this: Added: on the frustum on the right, I've marked four points I think we know something about. We can unproject all eight corners of the frusum, and the centres of the near and far ends. So we know point 1, 3 and 4. We also know that point 2 is the same distance from 3 as 4 is from 3. So then we can compute the nearest point on the line 1 to 4 to point 2 in order to get the centre? But the actual math and code escapes me. I want to draw models (which are approximately spherical and which I have a miniball bounding sphere for) as large as possible. Update: I've tried to implement the incircle-on-two-planes approach as suggested by bobobobo and Nathan Reed : function getFrustumsInsphere(viewport,invMvpMatrix) { var midX = viewport[0]+viewport[2]/2, midY = viewport[1]+viewport[3]/2, centre = unproject(midX,midY,null,null,viewport,invMvpMatrix), incircle = function(a,b) { var c = ray_ray_closest_point_3(a,b); a = a[1]; // far clip plane b = b[1]; // far clip plane c = c[1]; // camera var A = vec3_length(vec3_sub(b,c)), B = vec3_length(vec3_sub(a,c)), C = vec3_length(vec3_sub(a,b)), P = 1/(A+B+C), x = ((A*a[0])+(B*a[1])+(C*a[2]))*P, y = ((A*b[0])+(B*b[1])+(C*b[2]))*P, z = ((A*c[0])+(B*c[1])+(C*c[2]))*P; c = [x,y,z]; // now the centre of the incircle c.push(vec3_length(vec3_sub(centre[1],c))); // add its radius return c; }, left = unproject(viewport[0],midY,null,null,viewport,invMvpMatrix), right = unproject(viewport[2],midY,null,null,viewport,invMvpMatrix), horiz = incircle(left,right), top = unproject(midX,viewport[1],null,null,viewport,invMvpMatrix), bottom = unproject(midX,viewport[3],null,null,viewport,invMvpMatrix), vert = incircle(top,bottom); return horiz[3]<vert[3]? horiz: vert; } I admit I'm winging it; I'm trying to adapt 2D code by extending it into 3 dimensions. It doesn't compute the insphere correctly; the centre-point of the sphere seems to be on the line between the camera and the top-left each time, and its too big (or too close). Is there any obvious mistakes in my code? Does the approach, if fixed, work?

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• Dealing with 2D pixel shaders and SpriteBatches in XNA 4.0 component-object game engine?

  - by DaveStance

  I've got a bit of experience with shaders in general, having implemented a couple, very simple, 3D fragment and vertex shaders in OpenGL/WebGL in the past. Currently, I'm working on a 2D game engine in XNA 4.0 and I'm struggling with the process of integrating per-object and full-scene shaders in my current architecture. I'm using a component-entity design, wherein my "Entities" are merely collections of components that are acted upon by discreet system managers (SpatialProvider, SceneProvider, etc). In the context of this question, my draw call looks something like this: SceneProvider::Draw(GameTime) calls... ComponentManager::Draw(GameTime, SpriteBatch) which calls (on each drawable component) DrawnComponent::Draw(GameTime, SpriteBatch) The SpriteBatch is set up, with the default SpriteBatch shader, in the SceneProvider class just before it tells the ComponentManager to start rendering the scene. From my understanding, if a component needs to use a special shader to draw itself, it must do the following when it's Draw(GameTime, SpriteBatch) method is invoked: public void Draw(GameTime gameTime, SpriteBatch spriteBatch) { spriteBatch.End(); spriteBatch.Begin(SpriteSortMode.Immediate, BlendState.AlphaBlend, null, null, null, EffectShader, ViewMatrix); // Draw things here that are shaded by the "EffectShader." spriteBatch.End(); spriteBatch.Begin(/* same settings that were set by SceneProvider to ensure the rest of the scene is rendered normally */); } My question is, having been told that numerous calls to SpriteBatch.Begin() and SpriteBatch.End() within a single frame was terrible for performance, is there a better way to do this? Is there a way to instruct the currently running SpriteBatch to simply change the Effect shader it is using for this particular draw call and then switch it back before the function ends?

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• Moving Character in C# XNA Not working

  - by Matthew Stenquist

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

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• Partial recalculation of visibility on a 2D uniform grid

  - by Martin Källman

  Problem Imagine that we have a 2D uniform grid of dimensions N x N. For this grid we have also pre-computed a visibility look-up table, e.g. with DDA, which answers the boolean query is cell X visible from cell Y? The look-up table is a complete graph KN of the cells V in the grid, with each edge E being a binary value denoting the visibility between its vertices. Question If any given cell has its visibility modified, is it possible to extract the subset Edelta of edges which must have their visibility recomputed due to the change, so as to avoid a full-on recomputation for the entire grid? (Which is N(N-1) / 2 or N2 depending on the implementation) Update If is not possible to solve thi in closed form, then maintaining a separate mapping of each cell and every cell pair who's line intersects said cell might also be an option. This obviously consumes more memory, but the data is static. The increased memory requirement could be reduced by introducing a hierarchy, subdividing the grid into smaller parts, and by doing so the above mapping can be reused for each sub-grid. This would come at a cost in terms of increased computation relative to the number of subdivisions; also requiring a resumable ray-casting algorithm.

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• stdexcept On Android

  - by David R.

  I'm trying to compile SoundTouch on Android. I started with this configure line: ./configure CPPFLAGS="-I/Volumes/android-build/mydroid/development/ndk/build/platforms/android-3/arch-arm/usr/include/" LDFLAGS="-Wl,-rpath-link=/Volumes/android-build/mydroid/development/ndk/build/platforms/android-3/arch-arm/usr/lib -L/Volumes/android-build/mydroid/development/ndk/build/platforms/android-3/arch-arm/usr/lib -nostdlib -lc" --host=arm-eabi --enable-shared=yes CFLAGS="-nostdlib -O3 -mandroid" host_alias=arm-eabi --no-create --no-recursion Because the Android NDK targets ARM, I also had to change the Makefile to remove the -msse2 flags to progress. When I run 'make', I get: /bin/sh ../../libtool --tag=CXX --mode=compile arm-eabi-g++ -DHAVE_CONFIG_H -I. -I../../include -I../../include -I/Volumes/android-build/mydroid/development/ndk/build/platforms/android-3/arch-arm/usr/include/ -O3 -fcheck-new -I../../include -g -O2 -MT FIRFilter.lo -MD -MP -MF .deps/FIRFilter.Tpo -c -o FIRFilter.lo FIRFilter.cpp libtool: compile: arm-eabi-g++ -DHAVE_CONFIG_H -I. -I../../include -I../../include -I/Volumes/android-build/mydroid/development/ndk/build/platforms/android-3/arch-arm/usr/include/ -O3 -fcheck-new -I../../include -g -O2 -MT FIRFilter.lo -MD -MP -MF .deps/FIRFilter.Tpo -c FIRFilter.cpp -o FIRFilter.o FIRFilter.cpp:46:21: error: stdexcept: No such file or directory FIRFilter.cpp: In member function 'virtual void soundtouch::FIRFilter::setCoefficients(const soundtouch::SAMPLETYPE*, uint, uint)': FIRFilter.cpp:177: error: 'runtime_error' is not a member of 'std' FIRFilter.cpp: In static member function 'static void* soundtouch::FIRFilter::operator new(size_t)': FIRFilter.cpp:225: error: 'runtime_error' is not a member of 'std' make[2]: *** [FIRFilter.lo] Error 1 make[1]: *** [all-recursive] Error 1 make: *** [all-recursive] Error 1 This isn't very surprising, since the -nostdlib flag was required. Android seems to have neither stdexcept nor stdlib. How can I get past this block of compiling SoundTouch? At a guess, there may be some flag I don't know about that I should use. I could refactor the code not to use stdexcept. There may be a way to pull in the original stdexcept source and reference that. I might be able to link to a precompiled stdexcept library.

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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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• 3d vertex translated onto 2d viewport

  - by Dan Leidal

  I have a spherical world defined by simple trigonometric functions to create triangles that are relatively similar in size and shape throughout. What I want to be able to do is use mouse input to target a range of vertices in the area around the mouse click in order to manipulate these vertices in real time. I read a post on this forum regarding translating 3d world coordinates into the 2d viewport.. it recommended that you should multiply the world vector coordinates by the viewport and then the projection, but they didn't include any code examples, and suffice to say i couldn't get any good results. Further information.. I am using a lookat method for the viewport. Does this cause a problem, and if so is there a solution? If this isn't the problem, does anyone have a simple code example illustrating translating one vertex in a 3d world into a 2d viewspace? I am using XNA.

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