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  • Failing Screen Resize Method

    - by StrongJoshua
    So I want my game to draw to a specific "optimal" size and then be stretched to fit screens that are a different size. I'm using LibGDX and figured that I could just draw everything to a FrameBuffer and then resize that buffer to the appropriate size when drawing it to the actual display. However, my method does not work, it just results in a black screen with the top right quarter of the screen white.Intermediary is the FBO, interMatrix is a Matrix4 object, and camera is an OrthographicCamera. @Override public void render() { // update actors currentStage.act(); //render to intermediary buffer batch.setProjectionMatrix(interMatrix); intermediary.begin(); batch.begin(); currentStage.draw(); batch.flush(); intermediary.end(); //resize to actual width and height Sprite s = new Sprite(intermediary.getColorBufferTexture()); s.flip(true, false); batch.setProjectionMatrix(camera.combined); batch.draw(s.getTexture(), 0, 0, width, height); batch.end(); } These are the constructors for the above mentioned objects (GAME_WIDTH and HEIGHT are the "optimal" settings, width and height are the actual sizes, which are the same when running on desktop). intermediary = new FrameBuffer(Format.RGBA8888, GAME_WIDTH, GAME_HEIGHT, false); interMatrix = new Matrix4(); camera = new OrthographicCamera(width, height); interMatrix.setToOrtho2D(0, 0, GAME_WIDTH, GAME_HEIGHT); Is there a better way of doing this or can is this a viable option and how do I fix what I have?

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  • A few questions about how JavaScript works

    - by KayoticSully
    I originally posted on Stack Overflow and was told I might get some better answers here. I have been looking deeply into JavaScript lately to fully understand the language and have a few nagging questions that I can not seem to find answers to (Specifically dealing with Object Oriented programming. I know JavaScript is meant to be used in an OOP manner I just want to understand it for the sake of completeness). Assuming the following code: function TestObject() { this.fA = function() { // do stuff } this.fB = testB; function testB() { // do stuff } } TestObject.prototype = { fC : function { // do stuff } } What is the difference between functions fA and fB? Do they behave exactly the same in scope and potential ability? Is it just convention or is one way technically better or proper? If there is only ever going to be one instance of an object at any given time, would adding a function to the prototype such as fC even be worthwhile? Is there any benefit to doing so? Is the prototype only really useful when dealing with many instances of an object or inheritance? And what is technically the "proper" way to add methods to the prototype the way I have above or calling TestObject.prototype.functionName = function(){} every time? I am looking to keep my JavaScript code as clean and readable as possible but am also very interested in what the proper conventions for Objects are in the language. I come from a Java and PHP background and am trying to not make any assumptions about how JavaScript works since I know it is very different being prototype based. Also are there any definitive JavaScript style guides or documentation about how JavaScript operates at a low level? Thanks!

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  • How can I design my classes to include calendar events stored in a database?

    - by Gianluca78
    I'm developing a web calendar in php (using Symfony2) inspired by iCal for a project of mine. At this moment, I have two classes: a class "Calendar" and a class "CalendarCell". Here you are the two classes properties and method declarations. class Calendar { private $month; private $monthName; private $year; private $calendarCellList = array(); private $translator; public function __construct($month, $year, $translator) {} public function getCalendarCellList() {} public function getMonth() {} public function getMonthName() {} public function getNextMonth() {} public function getNextYear() {} public function getPreviousMonth() {} public function getPreviousYear() {} public function getYear() {} private function calculateDaysPreviousMonth() {} private function calculateNumericDayOfTheFirstDayOfTheWeek() {} private function isCurrentDay(\DateTime $dateTime) {} private function isDifferentMonth(\DateTime $dateTime) {} } class CalendarCell { private $day; private $month; private $dayNameAbbreviation; private $numericDayOfTheWeek; private $isCurrentDay; private $isDifferentMonth; private $translator; public function __construct(array $parameters) {} public function getDay() {} public function getMonth() {} public function getDayNameAbbreviation() {} public function isCurrentDay() {} public function isDifferentMonth() {} } Each calendar day can includes many calendar events (such as appointments or schedules) stored in a database. My question is: which is the best way to manage these calendar events in my classes? I think to add a eventList property in CalendarCell and populate it with an array of CalendarEvent objects fetched by the database. This kind of solution doesn't allow other coders to reuse the classes without db (because I should inject at least a repository services also) just to create and visualize a calendar... so maybe it could be better to extend CalendarCell (for instance in CalendarCellEvent) and add the database features? I feel like I'm missing some crucial design pattern! Any suggestion will be very appreciated!

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  • XNA - Obtaining depth from the scene's render target?

    - by user1423893
    I'm currently rendering my scene to a render target so it can be used for rendering methods such as post processing and order independent transparency. rtScene = new RenderTarget2D( GraphicsDevice, GraphicsDevice.PresentationParameters.BackBufferWidth, GraphicsDevice.PresentationParameters.BackBufferHeight, false, SurfaceFormat.Rgba64, DepthFormat.Depth24Stencil8, // Requires a depth format for objects to be drawn correctly (e.g. wireframe model surrounding model) 0, RenderTargetUsage.PreserveContents ); I am required to use RenderTargetUsage.PreserveContents so that the same render target can be rendered to multiple times, once for each of the draw methods below. DrawBackground DrawDeferred DrawForward DrawTransparent The problem is that DrawTransparent requires a copy of the scene's depth as a texture. Is there any way to obtain this from the scene render target above (rtScene)? I can't have more than one render target with RenderTargetUsage.PreserveContents as this causes problems on hardware such as the XBOX 360, so rendering the depth to a separate render target at the same time as I render the scene isn't possible as far as I can tell. Would I be able to get around this problem by "Ping-Ponging" two render targets (using the more compatible RenderTargetUsage.DiscardContents) and using the result for the depth texture?

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  • Google+ Platform Office Hours for April 25, 2012: Q&A with the Hangouts API Team

    Google+ Platform Office Hours for April 25, 2012: Q&A with the Hangouts API Team This week we were joined by Richard Dunn of the Hangouts API team who answered questions about the Hangouts API. Discuss this video on Google+: goo.gl 1:09 - What's going on with the Hangouts API? 3:43 - Jason shares information about his current projects 5:40 - Can I prevent a Hangout app from running within a Hangout On Air? 8:05 - Can we have APIs to control On Air features? 10:05 - Could a Silverlight / JavaScript bridge be created so we can use them in Hangout Apps? 12:01 - Is there a way to obfuscate the code for a Hangouts app? 15:24 - Are there plans to consolidate the various comment and chat channels for Hangouts On Air? 18:53 - When will Hangouts On Air come to Android? 20:48 - How can I access the OAuth token from the API? - developers.google.com 22:39 - When will we have Hangout apps on the mobile devices? 24:57 - Is it possible to search for 2 or more hash tags via the search REST API? 25:45 - Will we see a PHP REST API demo today? 26:20 - How can I restrict usage of a Hangout app? 30:07 - How do you hold a hangout that is simulcast on YouTube? 31:07 - Why do users show up as empty objects before they've authorized the app? 32:52 - What are the best practice for storing user specific configuration? 38:06 - Is anyone doing in application payment? 39:22 - Has anyone written any books about Hangout apps? From: GoogleDevelopers Views: 1619 19 ratings Time: 42:04 More in Science & Technology

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  • Skip CodedUI Tests, use Selenium for Web Automation

    - by Aligned
    Originally posted on: http://geekswithblogs.net/Aligned/archive/2013/10/31/skip-codedui-tests-use-selenium-for-web-automation.aspxI recently joined a team that was using Agile Methodologies to create a new product. They have a working beta product after 10 or so 2 week sprints and already had UI’s that had changed several times as they went through iterations of their UI. As a result, the QA team was falling behind with automated tests and I was tasked to help them catch up and expand their tests. The project is a website. I heard many complaints about how hard it is to work with CodedUI (writing our own code, not relying on the recorder as we wanted re-usable and more maintainable code) then it took me 4+ hours to fix one issue. It was hard to traverse the key and debugging the objects with breakpoints… I said out loud “there has to be a better way or a framework the uses jQuery to run through the tests.” Plus it seemed really slow (wait… finding the object … wait… start putting in text…). Plus some tests would randomly fail on the test agents (using the test settings and an automated build, they are run on VMs using Microsoft test agents). Enough complaining. Selenium to the rescue (mostly). The lead QA guy decided to try it out and we haven’t turned back. We are now running tests in Chrome and Firefox and they run a lot faster. We had IE running to, but some of the tests were running fine locally, but hanging on the test agents. I’ll add some hints and lessons learned in a later post.

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  • Python Web Applications: What is the way and the method to handle Registrations, Login-Logouts and Cookies? [on hold]

    - by Phil
    I am working on a simple Python web application for learning purposes. I have chosen a very minimalistic and simple framework. I have done a significant amount of research but I couldn't find a source clearly explaining what I need, which is as follows: I would like to learn more about: User registration User Log-ins User Log-outs User auto-logins I have successfully handled items 1 and 3 due to their simple nature. However, I am confused with item 2 (log-ins) and item 4 (auto-logins). When a user enters username and password, and after hashing with salts and matching it in the DB; What information should I store in the cookies in order to keep the user logged in during the session? Do I keep username+password but encrypt them? Both or just password? Do I keep username and a generated key matching their password? If I want the user to be able to auto-login (when they leave and come back to the web page), what information then is kept in the cookies? I don't want to use modules or libraries that handle these things automatically. I want to learn basics and why something is the way it is. I would also like to point out that I do not mind reading anything you might offer on the topic that explains hows and whys. Possibly with algorithm diagrams to show the process. Some information: I know about setting headers, cookies, encryption (up to some level, obviously not an expert!), request objects, SQLAlchemy etc. I don't want any data kept in a single web application server's store. I want multiple app-servers to be handle a user, and whatever needs to be kept on the server to be done with a Postgres/MySQL via SQLAlchemy (I think, this is called stateless?) Thank you.

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  • POLL: How do you build your interfaces in xcode for iphone/coco-touch applications?

    - by LolaRun
    Hi all, It's been 2 months i'm using xcode and building iphone apps, and i'm finding it really hard to grasp the good design for the applications. I always face problems like you can't put your tabbarcontroller in another custom viewcontroller sort of a thing? or other problems... That 'sometimes' - of course - would work if you did the creation of the views/viewcontrollers programmatically. so I don't know if i should start writing the creation of my objects or use interface builder. This is why i'm asking this poll question, to see what's the most accepted way among other developers. I'm not going to answer my question, so the votes would not increase my reputation and risk my poll being closed soon. I prefer that the first two readers of this question should answer by 'using IB' and the second one 'programmatically' and the rest would vote up or down for these two answers. And don't vote my question either, i just need to know, and maybe someone else wants to know. so the longer this question lives the better. and gaining nothing from it concerning reputation would help that cause. thank you all for your cooperation. and go ahead and answer Peace

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  • Scene transitions

    - by Mars
    It's my first time working with actual scenes/states, aka DrawableGameComponents, which work separate from one another. I'm now wondering what's the best way to make transitions between them, and how to affect them from other scenes. Lets say I wanted to "push" one screen to the right, with another one coming in at the same time. Naturally I'd have to keep drawing both, until the transition is complete. And I'd have to adjust the coordinates I'm drawing at while doing it. Is there a way around specifically handling this special case in every single scene? Or of I wanted to fade one into the other. Basically the question stays the same, how would you do that without having to handle it in every single scene? While writing this I'm realizing it will be the same thing for all kinds of transitions. Maybe a central Draw method in the manager could be a solution, where parameters and effects are applied when necessary. But this wouldn't work if objects that are drawn have their own method, and aren't drawn within the scene, or if an effect has to be applied to the whole scene. That means, maybe scenes have to be drawn to their own rendertarget? That way one call to the base class after the normal drawing could be enough, to apply the effects, while drawing it to the main render target. But I once heard there are problems when switching from target to target, back and forth. So is that even a viable option? As you can see, I have some basic ideas how it might work... but nothing specific. I'd like to learn what's the common way to achieve such things, a general way to apply all kinds of transitions.

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  • FP for simulation and modelling

    - by heaptobesquare
    I'm about to start a simulation/modelling project. I already know that OOP is used for this kind of projects. However, studying Haskell made me consider using the FP paradigm for modelling a system of components. Let me elaborate: Let's say I have a component of type A, characterised by a set of data (a parameter like temperature or pressure,a PDE and some boundary conditions,etc.) and a component of type B, characterised by a different set of data(different or same parameter, different PDE and boundary conditions). Let's also assume that the functions/methods that are going to be applied on each component are the same (a Galerkin method for example). If I were to use an OOP approach, I would create two objects that would encapsulate each type's data, the methods for solving the PDE(inheritance would be used here for code reuse) and the solution to the PDE. On the other hand, if I were to use an FP approach, each component would be broken down to data parts and the functions that would act upon the data in order to get the solution for the PDE. This approach seems simpler to me assuming that linear operations on data would be trivial and that the parameters are constant. What if the parameters are not constant(for example, temperature increases suddenly and therefore cannot be immutable)? In OOP, the object's (mutable) state can be used. I know that Haskell has Monads for that. To conclude, would implementing the FP approach be actually simpler,less time consuming and easier to manage (add a different type of component or new method to solve the pde) compared to the OOP one? I come from a C++/Fortran background, plus I'm not a professional programmer, so correct me on anything that I've got wrong.

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  • AI agents with FSM: a question regarding this

    - by Prog
    Finite State Machines implemented with the State design pattern are a common way to design AI agents. I am familiar with the State design pattern and know how to implement it. However I have a question regarding how this is used in games to design AI agents. Please consider a class Monster that represents an AI agent. Simplified it looks like this: class Monster{ State state; // other fields omitted public void update(){ // called every game-loop cycle state.execute(this); } public void setState(State state){ this.state = state; } // irrelevant stuff omitted } There are several State subclasses that implement execute() differently. So far classic State pattern. Here's my question: AI agents are subject to environmental effects and other objects communicating with them. For example an AI agent might tell another AI agent to attack (i.e. agent.attack()). Or a fireball might tell an AI agent to fall down. This means that the agent must have methods such as attack() and fallDown(), or commonly some message receiving mechanism to understand such messages. My question is divided to two parts: 1- Please say if this is correct: With an FSM, the current State of the agent should be the one taking care of such method calls - i.e. the agent delegates to the current state upon every event. Correct? Or wrong? 2- If correct, than how is this done? Are all states obligated by their superclass) to implement methods such as attack(), fallDown() etc., so the agent can always delegate to them on almost every event? Or is it done in some other way?

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  • Prevent collisions between mobs/npcs/units piloted by computer AI : How to avoid mobile obstacles?

    - by Arthur Wulf White
    Lets says we have character a starting at point A and character b starting at point B. character a is headed to point B and character b is headed to point A. There are several simple ways to find the path(I will be using Dijkstra). The question is, how do I take preventative action in the code to stop the two from colliding with one another? case2: Characters a and b start from the same point in different times. Character b starts later and is the faster of the two. How do I make character b walk around character a without going through it? case3:Lets say we have m such characters in each side and there is sufficient room to pass through without the characters overlapping with one another. How do I stop the two groups of characters from "walking on top of one another" and allow them pass around one another in a natural organic way. A correct answer would be any algorithm, that given the path to the destination and a list of mobile objects that block the path, finds an alternative path or stops without stopping all units when there is sufficient room to traverse.

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  • Access Control Service: Programmatically Accessing Identity Provider Information and Redirect URLs

    - by Your DisplayName here!
    In my last post I showed you that different redirect URLs trigger different response behaviors in ACS. Where did I actually get these URLs from? The answer is simple – I asked ACS ;) ACS publishes a JSON encoded feed that contains information about all registered identity providers, their display names, logos and URLs. With that information you can easily write a discovery client which, at the very heart, does this: public void GetAsync(string protocol) {     var url = string.Format( "https://{0}.{1}/v2/metadata/IdentityProviders.js?protocol={2}&realm={3}&version=1.0",         AcsNamespace,         "accesscontrol.windows.net",         protocol,         Realm);     _client.DownloadStringAsync(new Uri(url)); } The protocol can be one of these two values: wsfederation or javascriptnotify. Based on that value, the returned JSON will contain the URLs for either the redirect or notify method. Now with the help of some JSON serializer you can turn that information into CLR objects and display them in some sort of selection dialog. The next post will have a demo and source code.

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  • Learn More About the PO Approvals Analyzer

    - by LuciaC
    You may think that the PO Approvals Analyzer for Release 12 is only for diagnosing problems when you have a single Purchase Order or Requisition stuck in process, but it offers valuable information to keep your Procurement environment healthy.  Consider this:     The analyzer will list all Procurement critical patches that have not been applied.     It will provide Procurement invalid objects with error messages and provides solutions.     Validations of setup and database conditions for example max extents and space issues. Also the analyzer can be run on all Purchasing documents starting from a date you enter.  This multiple document check provides validations on:     Data corruption issues.     Workflow errors with generic messages i.e. document manager errors.     Documents with workflows in error that cannot be progressed via the application. And, unlike other diagnostics, the analyzer provides known solutions to the problems indicated! So access the Analyzer today and run it on your instance!  Access it now via Doc ID 1525670.1.

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  • Anemic Domain Model, Business Logic and DataMapper (PHP)

    - by sunwukung
    I've implemented a rudimentary ORM layer based on DataMapper (I don't want to use a full blown ORM like Propel/Doctrine - for anything beyond simple fetch/save ops I prefer to access the data directly layer using a SQL abstraction layer). Following the DataMapper pattern, I've endeavoured to keep all persistence operations in the Mapper - including the location of related entities. My Entities have access to their Mapper, although I try not to call Mapper logic from the Entity interface (although this would be simple enough). The result is: // get a mapper and produce an entity $ProductMapper = $di->get('product_mapper'); $Product = $ProductMapper->find('[email protected]','email'); //.. mutaute some values.. save $ProductMapper->save($Product) // uses __get to trigger relation acquisition $Manufacturer = $Product->manufacturer; I've read some articles regarding the concept of an Anemic Domain model, i.e. a Model that does not contain any "business logic". When demonstrating the sort of business logic ideally suited to a Domain Model, however, acquiring related data items is a common example. Therefore I wanted to ask this question: Is persistence logic appropriate in Domain Model objects?

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  • As a programmer, what's the most valuable non-English (human) language to learn?

    - by Andrew M
    I was thinking that with my developer skills, learning new languages like French, German etc. might be easier for me now. I could setup the verbs as objects in Python and use dir(verb) to find its methods, tenses and stuff ;-) But seriously, if you're a professional developer, in my case in the UK, what's the best foreign language to learn from an employment perspective? I'm thinking, like Hindi - if all our programming jobs are getting outsourced to India, might as well position yourself to be the on-site, go-between guy. Mandarin - if the Chinese become the pre-eminent economy, the new USA, in ten or twenty years, then speaking their language would open up a huge market to you. Russian - maybe another major up-and-comer, but already closer to Western standards. More IT-sector growth here than anywhere else in the coming years? Japanese - drivers of global technology, being able to speak their language could give you a big competitive advantage over other Westerners But I'm just guessing/musing with all these points. If you have an opinion, or even better, some evidence, I'd like to hear it. If the programming things falls through then at least it'll make for more interesting holidays.

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  • Take a snapshot with JavaFX!

    - by user12610255
    JavaFX 2.2 has a "snapshot" feature that enables you to take a picture of any node or scene. Take a look at the API Documentation and you will find new snapshot methods in the javafx.scene.Scene class. The most basic version has the following signature: public WritableImage snapshot(WritableImage image) The WritableImage class (also introduced in JavaFX 2.2) lives in the javafx.scene.image package, and represents a custom graphical image that is constructed from pixels supplied by the application. In fact, there are 5 new classes in javafx.scene.image: PixelFormat: Defines the layout of data for a pixel of a given format. WritablePixelFormat: Represents a pixel format that can store full colors and so can be used as a destination format to write pixel data from an arbitrary image. PixelReader: Defines methods for retrieving the pixel data from an Image or other surface containing pixels. PixelWriter: Defines methods for writing the pixel data of a WritableImage or other surface containing writable pixels. WritableImage: Represents a custom graphical image that is constructed from pixels supplied by the application, and possibly from PixelReader objects from any number of sources, including images read from a file or URL. The API documentation contains lots of information, so go investigate and have fun with these useful new classes! -- Scott Hommel

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  • Are specific types still necessary?

    - by MKO
    One thing that occurred to me the other day, are specific types still necessary or a legacy that is holding us back. What I mean is: do we really need short, int, long, bigint etc etc. I understand the reasoning, variables/objects are kept in memory, memory needs to be allocated and therefore we need to know how big a variable can be. But really, shouldn't a modern programming language be able to handle "adaptive types", ie, if something is only ever allocated in the shortint range it uses fewer bytes, and if something is suddenly allocated a very big number the memory is allocated accordinly for that particular instance. Float, real and double's are a bit trickier since the type depends on what precision you need. Strings should however be able to take upp less memory in many instances (in .Net) where mostly ascii is used buth strings always take up double the memory because of unicode encoding. One argument for specific types might be that it's part of the specification, ie for example a variable should not be able to be bigger than a certain value so we set it to shortint. But why not have type constraints instead? It would be much more flexible and powerful to be able to set permissible ranges and values on variables (and properties). I realize the immense problem in revamping the type architecture since it's so tightly integrated with underlying hardware and things like serialization might become tricky indeed. But from a programming perspective it should be great no?

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  • Authenticate with Django 1.5

    - by gorjuce
    I'm currently testing django 1.5 and a custom User model, but I've some problems. I've created a User class in my account app, which looks like: class User(AbstractBaseUser): email = models.EmailField() activation_key = models.CharField(max_length=255) is_active = models.BooleanField(default=False) is_admin = models.BooleanField(default=False) USERNAME_FIELD = 'email' I can correctly register a user, who is stored in my account_user table. Now, how can I log in? I've tried with: def login(request): form = AuthenticationForm() if request.method == 'POST': form = AuthenticationForm(request.POST) email = request.POST['username'] password = request.POST['password'] user = authenticate(username=email, password=password) if user is not None: if user.is_active: login(user) else: message = 'disabled account, check validation email' return render( request, 'account-login-failed.html', {'message': message} ) return render(request, 'account-login.html', {'form': form}) I can correctly register a new User My forms.py which contains my register form class RegisterForm(forms.ModelForm): """ a form to create user""" password = forms.CharField( label="Password", widget=forms.PasswordInput() ) password_confirm = forms.CharField( label="Password Repeat", widget=forms.PasswordInput() ) class Meta: model = User exclude = ('last_login', 'activation_key') def clean_password_confirm(self): password = self.cleaned_data.get("password") password_confirm = self.cleaned_data.get("password_confirm") if password and password_confirm and password != password_confirm: raise forms.ValidationError("Password don't math") return password_confirm def clean_email(self): if User.objects.filter(email__iexact=self.cleaned_data.get("email")): raise forms.ValidationError("email already exists") return self.cleaned_data['email'] def save(self): user = super(RegisterForm, self).save(commit=False) user.password = self.cleaned_data['password'] user.activation_key = generate_sha1(user.email) user.save() return user My question is: Why does authenticate give me None? I know I'm trying to authenticate() with an email as username but is that not one of the reasons to use a custom User model?

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  • How do I interpolate air drag with a variable time step?

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

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  • Is there a (family of) monotonically non-decreasing noise function(s)?

    - by Joe Wreschnig
    I'd like a function to animate an object moving from point A to point B over time, such that it reaches B at some fixed time, but its position at any time is randomly perturbed in a continuous fashion, but never goes backwards. The objects move along straight lines, so I only need one dimension. Mathematically, that means I'm looking for some continuous f(x), x ? [0,1], such that: f(0) = 0 f(1) = 1 x < y ? f(x) = f(y) At "most" points f(x + d) - f(x) bears no obvious relation to d. (The function is not uniformly increasing or otherwise predictable; I think that's also equivalent to saying no degree of derivative is a constant.) Ideally, I would actually like some way to have a family of these functions, providing some seed state. I'd need at least 4 bits of seed (16 possible functions), for my current use, but since that's not much feel free to provide even more. To avoid various issues with accumulation errors, I'd prefer the function not require any kind of internal state. That is, I want it to be a real function, not a programming "function".

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  • How to choose between Tell don't Ask and Command Query Separation?

    - by Dakotah North
    The principle Tell Don't Ask says: you should endeavor to tell objects what you want them to do; do not ask them questions about their state, make a decision, and then tell them what to do. The problem is that, as the caller, you should not be making decisions based on the state of the called object that result in you then changing the state of the object. The logic you are implementing is probably the called object’s responsibility, not yours. For you to make decisions outside the object violates its encapsulation. A simple example of "Tell, don't Ask" is Widget w = ...; if (w.getParent() != null) { Panel parent = w.getParent(); parent.remove(w); } and the tell version is ... Widget w = ...; w.removeFromParent(); But what if I need to know the result from the removeFromParent method? My first reaction was just to change the removeFromParent to return a boolean denoting if the parent was removed or not. But then I came across Command Query Separation Pattern which says NOT to do this. It states that every method should either be a command that performs an action, or a query that returns data to the caller, but not both. In other words, asking a question should not change the answer. More formally, methods should return a value only if they are referentially transparent and hence possess no side effects. Are these two really at odds with each other and how do I choose between the two? Do I go with the Pragmatic Programmer or Bertrand Meyer on this?

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  • C# XNA 2D Multiple boxes collision detection and movement

    - by zini
    Hi, I've been making simple game where you shoot boxes that are coming towards you. All game objects are simple rectangles. Now I have problem with collision detection; how to check where the collision comes so I can change the coordinates right? I have this kind of situation: http://imgur.com/8yjfW Imagine that all of those blocks are moving towards you (green box). If those orange boxes collide with each other, they should "avoid" themselves and not go through each other. I have class Enemy which has properties x, y and such. Now I'm doing the collision like this: // os.Count is an amount of other enemies colliding with this enemy if (os.Count == 0) { // If enemy doesn't collide with other enemy lasty = y; lastx = x; slope = (x - player.x) / (y - player.y); x += slope * l; // l is "movement speed" of enemy (float) if (y > player.y) { y = lasty; } else if (y < player.y) { y += l; } } else { foreach(Enemy b in os) { if (b.y > this.y) { // If some colliding enemy is closer player than this enemy, that closer one will be moved towards the player b.lasty = b.y; if (!BiggestY(os)) { // BiggestY returns true if this enemy has the biggest Y b.y += b.l; } b.x = b.lastx; } } } But this is very, very bad way to do this. I know it, but I just can't figure out other way. And as a matter in fact, this method doesn't even work pretty good; if multiple enemies are colliding same enemy they go through each other. I explained this pretty badly, but I hope that you understand this. And to sum up, as I said: How to check where the collision comes so I can change the coordinates right?

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  • Design in "mixed" languages: object oriented design or functional programming?

    - by dema80
    In the past few years, the languages I like to use are becoming more and more "functional". I now use languages that are a sort of "hybrid": C#, F#, Scala. I like to design my application using classes that correspond to the domain objects, and use functional features where this makes coding easier, more coincise and safer (especially when operating on collections or when passing functions). However the two worlds "clash" when coming to design patterns. The specific example I faced recently is the Observer pattern. I want a producer to notify some other code (the "consumers/observers", say a DB storage, a logger, and so on) when an item is created or changed. I initially did it "functionally" like this: producer.foo(item => { updateItemInDb(item); insertLog(item) }) // calls the function passed as argument as an item is processed But I'm now wondering if I should use a more "OO" approach: interface IItemObserver { onNotify(Item) } class DBObserver : IItemObserver ... class LogObserver: IItemObserver ... producer.addObserver(new DBObserver) producer.addObserver(new LogObserver) producer.foo() //calls observer in a loop Which are the pro and con of the two approach? I once heard a FP guru say that design patterns are there only because of the limitations of the language, and that's why there are so few in functional languages. Maybe this could be an example of it? EDIT: In my particular scenario I don't need it, but.. how would you implement removal and addition of "observers" in the functional way? (I.e. how would you implement all the functionalities in the pattern?) Just passing a new function, for example?

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  • Need help understanding Mocks and Stubs

    - by Theomax
    I'm new to use mocking frameworks and I have a few questions on the things that I am not clear on. I'm using Rhinomocks to generate mock objects in my unit tests. I understand that mocks can be created to verify interactions between methods and they record the interactions etc and stubs allow you to setup data and entities required by the test but you do not verify expectations on stubs. Looking at the recent unit tests I have created, I appear to be creating mocks literally for the purpose of stubbing and allowing for data to be setup. Is this a correct usage of mocks or is it incorrect if you're not actually calling verify on them? For example: user = MockRepository.GenerateMock<User>(); user.Stub(x => x.Id = Guid.NewGuid()); user.Stub(x => x.Name = "User1"); In the above code I generate a new user mock object, but I use a mock so I can stub the properties of the user because in some cases if the properties do not have a setter and I need to set them it seems the only way is to stub the property values. Is this a correct usage of stubbing and mocking? Also, I am not completely clear on what the difference between the following lines is: user.Stub(x => x.Id).Return(new Guid()); user.Stub(x => x.Id = Guid.NewGuid());

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