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  • Numerical stability in continuous physics simulation

    - by Panda Pajama
    Pretty much all of the game development I have been involved with runs afoul of simulating a physical world in discrete time steps. This is of course very simple, but hardly elegant (not to mention mathematically inaccurate). It also has severe disadvantages when large values are involved (either very large speeds, or very large time intervals). I'm trying to make a continuous physics simulation, just for learning, which goes like this: time = get_time() while true do new_time = get_time() update_world(new_time - time) render() time = new_time end And update_world() is a continuous physical simulation. Meaning that for example, for an accelerated object, instead of doing object.x = object.x + object.vx * timestep object.vx = object.vx + object.ax * timestep -- timestep is fixed I'm doing something like object.x = object.x + object.vx * deltatime + object.ax * ((deltatime ^ 2) / 2) object.vx = object.vx + object.ax * deltatime However, I'm having a hard time with the numerical stability of my solutions, especially for very large time intervals (think of simulating a physical world for hundreds of thousands of virtual years). Depending on the framerate, I get wildly different solutions. How can I improve the numerical stability of my continuous physical simulations?

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  • Name user object and user table correctly

    - by Marc
    It's maybe simple but I think about this every time I build a new application. How do you name the class for the current user of the application and for the orm class of the user table? Usually I have something like CurrentUser: Logged-in user, stored in session, info for last activity etc User: ORM Class (C# EF CodeFirst, but it doesn't matter) And yes, they could have the same name in different namespaces, but I don't really like that.

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  • Why do i get a circular reference exception when calling to_json on an ActiveRecord::Relation

    - by midas06
    In Rails 3 (beta 3 on 1.8.7), when calling to_json on a relation i get a circular reference exception. Converting that relation to an array first, and THEN calling to_json works. Code That fails: Model.where().to_json (Where model is any model in your Rails 3 app) Code that works: Model.where().to_a.to_json This can be reproed on the console. Has anyone else run in to this? Is this expected?

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  • Object-Oriented OpenGL

    - by Sullivan
    I have been using OpenGL for a while and have read a large number of tutorials. Aside from the fact that a lot of them still use the fixed pipeline, they usually throw all the initialisation, state changes and drawing in one source file. This is fine for the limited scope of a tutorial, but I’m having a hard time working out how to scale it up to a full game. How do you split your usage of OpenGL across files? Conceptually, I can see the benefits of having, say, a rendering class that purely renders stuff to screen, but how would stuff like shaders and lights work? Should I have separate classes for things like lights and shaders?

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  • Opengl-es picking object

    - by lacas
    I saw a lot of picking code opengl-es, but nothing worked. Can someone give me what am I missing? My code is (from tutorials/forums) Vec3 far = Camera.getPosition(); Vec3 near = Shared.opengl().getPickingRay(ev.getX(), ev.getY(), 0); Vec3 direction = far.sub(near); direction.normalize(); Log.e("direction", direction.x+" "+direction.y+" "+direction.z); Ray mouseRay = new Ray(near, direction); for (int n=0; n<ObjectFactory.objects.size(); n++) { if (ObjectFactory.objects.get(n)!=null) { IObject obj = ObjectFactory.objects.get(n); float discriminant, b; float radius=0.1f; b = -mouseRay.getOrigin().dot(mouseRay.getDirection()); discriminant = b * b - mouseRay.getOrigin().dot(mouseRay.getOrigin()) + radius*radius; discriminant = FloatMath.sqrt(discriminant); double x1 = b - discriminant; double x2 = b + discriminant; Log.e("asd", obj.getName() + " "+discriminant+" "+x1+" "+x2); } } my camera vectors: //cam Vec3 position =new Vec3(-obj.getPosX()+x, obj.getPosZ()-0.3f, obj.getPosY()+z); Vec3 direction =new Vec3(-obj.getPosX(), obj.getPosZ(), obj.getPosY()); Vec3 up =new Vec3(0.0f, -1.0f, 0.0f); Camera.set(position, direction, up); and my picking code: public Vec3 getPickingRay(float mouseX, float mouseY, float mouseZ) { int[] viewport = getViewport(); float[] modelview = getModelView(); float[] projection = getProjection(); float winX, winY; float[] position = new float[4]; winX = (float)mouseX; winY = (float)Shared.screen.width - (float)mouseY; GLU.gluUnProject(winX, winY, mouseZ, modelview, 0, projection, 0, viewport, 0, position, 0); return new Vec3(position[0], position[1], position[2]); } My camera moving all the time in 3d space. and my actors/modells moving too. my camera is following one actor/modell and the user can move the camera on a circle on this model. How can I change the above code to working?

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  • This for array colllision function doesn't work with anything but first object in array

    - by Zee Bashew
    For some reason, this simple simple loop is totally broken. (characterSheet is my character Class, it's just a movieClip with some extra functionality) (hitBox, is basically a square movieclip) Anyway: every time hitBox make contact with a characterSheet in a different order than they were created: Nothing happens. The program only seems to be listening to collisions that are made with o2[0]. As soon as another hitBox is created, it pushes the last one out of o2[0] and the last one becomes totally useless. What's super weird is that I can hit characterSheets in any order I like.... public function collisions(o1:Array, o2:Array) { if((o1.lenght>=0)&&(o2.length>=0)){ for (var i = 0; i < o1.length; i++) { var ob1 = o1[i]; for (var f = 0; f < o1.length; f++) { var ob2 = o2[f]; if (ob1 is characterSheet) { if (ob2.hitTestObject(ob1)) { var right:Boolean = true; if (ob1.x < hitBox(ob2).origin.x) right = false; characterSheet(ob1).specialDamage(hitBox(ob2).damageType, hitBox(ob2).damage, right); }}}}}} Also it might be somewhat helpful to see the function for creating a new hitBox public function SpawnHitBox(targeted, following, atype, xoff, yoff, ... args) { var newHitBox = new hitBox(targeted, following, atype, xoff, yoff, args); badCollisionObjects.push(newHitBox); arraydictionary[newHitBox] = badCollisionObjects; addChild(newHitBox); }

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  • Control Reference Static Method Performance

    - by dotnetguts
    I have just asked which one is better? Static Vs Non-Static? http://stackoverflow.com/questions/3016717/static-vs-non-static-method-performance-c I would like to take this discussion one step ahead. Consider If i pass reference of Panel control as parameter to Public static method, will static method still rules in performance?

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  • libgdx collision detection / bounding the object

    - by johnny-b
    i am trying to get collision detection so i am drawing a red rectangle to see if it is working, and when i do the code below in the update method. to check if it is going to work. the position is not in the right place. the red rectangle starts from the middle and not at the x and y point?Huh so it draws it wrong. i also have a getter method so nothing wrong there. bullet.set(getX(), getY(), getOriginX(), getOriginY()); this is for the render shapeRenderer.begin(ShapeType.Filled); shapeRenderer.setColor(Color.RED); shapeRenderer.rect(bullet.getX(), bullet.getY(), bullet.getOriginX(), bullet.getOriginY(), 15, 5, bullet.getRotation()); shapeRenderer.end(); i have tried to do it with a circle but the circle draws in the middle and i want it to be at the tip of the bullet. at the front of the bullet. x, y point. boundingCircle.set(getX() + getOriginX(), getY() + getOriginY(), 4.0f); shapeRenderer.begin(ShapeType.Filled); shapeRenderer.setColor(Color.RED); shapeRenderer.circle(bullet.getBoundingCircle().x, bullet.getBoundingCircle().y, bullet.getBoundingCircle().radius); shapeRenderer.end(); thank you need it to be of the x and y as the bullet is in the middle of the sprite when drawn originally via paint.

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  • What should a domain object's validation cover?

    - by MarcoR88
    I'm trying to figure out how to do validation of domain objects that need external resources, such as data mappers/dao Firstly here's my code class User { const INVALID_ID = 1; const INVALID_NAME = 2; const INVALID_EMAIL = 4; int getID(); void setID(Int i); string getName(); void setName(String s); string getEmail(); void setEmail(String s); int getErrorsForInsert(); // returns a bitmask for INVALID_* constants int getErrorsForUpdate(); } My worries are about the uniqueness of the email, checking it would require the storage layer. Reading others' code seems that two solutions are equally accepted: both perform the unique validation in data mapper but some set an error state to the DO user.addError(User.INVALID_EMAIL) while others prefer to throw a totally different type of exception that covers only persistence, like: UserStorageException { const INVALID_EMAIL = 1; const INVALID_CITY = 2; } What are the pros and cons of these solutions?

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  • Modify a reference numbered group to match against

    - by StuperUser
    I want to match YYYY-YY for sequential years. I at moment I'm trying to match where all the second YY is the 3rd and 4th characters in YYYY with 1 added to it. So far I've got {19|20}(\d{2})-(\d{2}), but not sure how to use ? with reference to (1) or whether I'm going about this the right way and finding out the inevitable "unknown unknowns" (like YY99) with this approach? Edit: Matches: 2010-11,2011-12,2029-30 Not matches: 2010-12, 2010-09,2011-2,2011-2012

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  • Share java object between two forms using Spring IoC

    - by Vladimir
    I want to share java object between two forms using Spring IoC. It should acts like Registry: Registry.set("key", new Object()); // ... Object o = Registry.get("key"); // ... Registry.set("key", new AnotherObject()); // rewrite old object I tried this code to register bean at runtime: applicationContext.getBeanFactory().registerSingleton("key", object); but it does not allow to rewrite existing object (result code for checking and deleting existing bean is too complicated)... PS I am Java newbie, so mb I am doing it wrong and I should not use IoC at all... any help is appreciated...

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  • How to move an object using X and Y coordinates in JavaScript

    - by Geroy290
    I am making a 2d game with JavaScript and HTML5 and am trying to move an image that I have drawn with JavaScript like so: //canvas var c = document.getElementById("gameCanvas"); var ctx = c.getContext("2d"); //baseball var baseball = new Image(); baseball.onload = function() { ctx.drawImage(baseball, 400, 425); }; baseball.src = "baseball2.png"; I'm not sure how I would move it though, I have seen many people seem to just type something like ballX and ballY but I don't understand where the actual x and y definition comes from. Here is my code so far: http://jsfiddle.net/xRfua/ I have a different image source but it is a local source so I couldn't include it. Thanks in a dvance for any help!

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  • C++: Checking if an object faces a point (within a certain range)

    - by bojoradarial
    I have been working on a shooter game in C++, and am trying to add a feature whereby missiles shot must be within 90 degrees (PI/2 radians) of the direction the ship is facing. The missiles will be shot towards the mouse. My idea is that the ship's angle of rotation is compared with the angle between the ship and the mouse (std::atan2(mouseY - shipY, mouseX - shipX)), and if the difference is less than PI/4 (45 degrees) then the missile can be fired. However, I can't seem to get this to work. The ship's angle of rotation is increased and decreased with the A and D keys, so it is possible that it isn't between 0 and 2*PI, hence the use of fmod() below. Code: float userRotation = std::fmod(user->Angle(), 6.28318f); if (std::abs(userRotation - missileAngle) > 0.78f) return; Any help would be appreciated. Thanks!

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  • win32:libs undefined reference

    - by hector
    I want to link a .lib in my Qt project and I get an error about an undefined reference to vhtIOConn::getDefault(vhtIOConn::DeviceType). I have already added the following specifications to the .pro file: ###################################################################### # Automatically generated by qmake (2.01a) vie 28. ago 12:48:10 2009 ###################################################################### TARGET = DEPENDPATH += . INCLUDEPATH += . LIBS += "C:\agregar\VirtualHandCore.lib" LIBS += "C:\agregar\VirtualHandDevice.lib" LIBS += "C:\agregar\VirtualHandRegistry.lib" # Input HEADERS += "C:/Documents and Settings/halvarado/Mis documentos/respaldos de Qt/Development/include/vhandtk/vhtBase.h" SOURCES += main.cpp What should I do?

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  • Object-based content management system

    - by Adam Maras
    I remember hearing within the last year or two about a content management system either being released or developed that was centralized around product/item information. I'm aware that there are several CMSes that have this capability, but this particular one was built specifically for that task. Also, I remember it winning some sort of award or recognition for upcoming software products. However, I can't for the life of me remember what this CMS was called or who was developing it. Does anyone know what package I'm talking about?

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  • Autofac: Reference from a SingleInstance'd type to a HttpRequestScoped

    - by Michael Wagner
    I've got an application where a shared object needs a reference to a per-request object. Shared: Engine | Per Req: IExtensions() | Request If i try to inject the IExtensions directly into the constructor of Engine, even as Lazy(Of IExtension), I get a "No scope matching [Request] is visible from the scope in which the instance was requested." exception when it tries to instantiate each IExtension. How can I create a HttpRequestScoped instance and then inject it into a shared instance? Would it be considered good practice to set it in the Request's factory (and therefore inject Engine into RequestFactory)?

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  • Periodic updates of an object in Unity

    - by Blue
    I'm trying to make a collider appear every 1 second. But I can't get the code right. I tried enabling the collider in the Update function and putting a yield to make it update every second or so. But it's not working (it gives me an error: Update() cannot be a coroutine.) How would I fix this? Would I need a timer system to toggle the collider? var waitTime : float = 1; var trigger : boolean = false; function Update () { if(!trigger){ collider.enabled = false; yield WaitForSeconds(waitTime); } if(trigger){ collider.enabled = true; yield WaitForSeconds(waitTime); } } }

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  • C++ undefined reference

    - by klaus-johan
    Hi , My problem is the following : I have a class A that inherits from an abstract base class. I override all the virtual functions from the base class, and I have a constructor like this : A::A(B* b) { this->b=b; } In the constructor of class B , I have the following piece of code: A* a=new A(this) However this line of code gives the error : undefined reference to 'A::A(B*)' I have absolutly no idea why could this be happening , so any suggestion would be greatly appreciated !

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