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• Implementing an automatic navigation mesh generation for 2d top down map?

  - by J2V

  I am currently in the middle of implementing an A* pathfinding for enemies. In order to implement the actual A* logic, I need a navigation mesh for my map. I am working on a 2D top down rpg map. The world is static, meaning there is no requirement for dynamic runtime mesh generation. My world objects are pixel based, not tile based and have associated data with them such as scale, rotation, origin etc. I will obviously need some vertex data being generated from my world objects, maybe create a polygon generation from color data? I could create a colormap with objects for my whole map, but I have no idea how to begin creating nav mesh polygons. How would an actual navigation mesh generation look like with this kind of available information? Can anyone maybe point to some great resources? I have looked into some 3D nav mesh tools, but they seem kind of overly complex for my situation and also have a lot of their req data available from models. Thanks a lot in advance! I have been trying to get my head around it for some time now.

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• Best way to let users choose country/language when submiting an URL to a directory

  - by Claudiu

  Hi all, I want to offer the user the possibility to add the country/language for websites they would submit to a fairly simple website directory. I have a folder with flags from http://www.famfamfam.com/lab/icons/flags/ . The flag images are named according to the ISO 3166-1 alpha-2 country codes, meaning that I could make a PHP script that would be able to retrieve images and the name of the country retrieved from the image name (not the full name, but it wouldn't be necessary). Just to make things clearer, I couldn't find a proper combo-box jQuery plugin for my needs (that would act exactly like the native but with an icon before the text) and don't really have the time to develop one on my own. Considering the number of images, I also wouldn't just display them all with a radio box near them. Also, having a classic drop-down list would be a nightmare for me as I would have to assign the short country name manually to each entry, or do it once for every country. Offering the user a dropdown list with the short country names but no flag near them would also be unfriendly and confusing. The idea is that every website featured in the directory would have the country flag icon near it. I have the images named properly but I don't know how to let the user choose the right image for their website. Any idees? Thank you all in advance! EDIT Temporary solution is this file: http://www.andrewpatton.com/countrylist.csv It contains a list of countries including various other info, like the short country name, the same name that's used for the flag images. I can take that information and have a classic like this: <select name="countries"> <option value="ro">Romania</option> <option value="ie">Ireland</option> <!-- and so on --> </select> Still, If anybody has a better idea...

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• Discuss: PLs are characterised by which (iso)morphisms are implemented

  - by Yttrill

  I am interested to hear discussion of the proposition summarised in the title. As we know programming language constructions admit a vast number of isomorphisms. In some languages in some places in the translation process some of these isomorphisms are implemented, whilst others require code to be written to implement them. For example, in my language Felix, the isomorphism between a type T and a tuple of one element of type T is implemented, meaning the two types are indistinguishable (identical). Similarly, a tuple of N values of the same type is not merely isomorphic to an array, it is an array: the isomorphism is implemented by the compiler. Many other isomorphisms are not implemented for example there is an isomorphism expressed by the following client code: match v with | ((?x,?y),?z = x,(y,z) // Felix match v with | (x,y), - x,(y,z) (* Ocaml *) As another example, a type constructor C of int in Felix may be used directly as a function, whilst in Ocaml you must write a wrapper: let c x = C x Another isomorphism Felix implements is the elimination of unit values, including those in tuples: Felix can do this because (most) polymorphic values are monomorphised which can be done because it is a whole program analyser, Ocaml, for example, cannot do this easily because it supports separate compilation. For the same reason Felix performs type-class dispatch at compile time whilst Haskell passes around dictionaries. There are some quite surprising issues here. For example an array is just a tuple, and tuples can be indexed at run time using a match and returning a value of a corresponding sum type. Indeed, to be correct the index used is in fact a case of unit sum with N summands, rather than an integer. Yet, in a real implementation, if the tuple is an array the index is replaced by an integer with a range check, and the result type is replaced by the common argument type of all the constructors: two isomorphisms are involved here, but they're implemented partly in the compiler translation and partly at run time.

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• How do I use depth testing and texture transparency together in my 2.5D world?

  - by nbolton

  Note: I've already found an answer (which I will post after this question) - I was just wondering if I was doing it right, or if there is a better way. I'm making a "2.5D" isometric game using OpenGL ES (JOGL). By "2.5D", I mean that the world is 3D, but it is rendered using 2D isometric tiles. The original problem I had to solve was that my textures had to be rendered in order (from back to front), so that the tiles overlapped properly to create the proper effect. After some reading, I quickly realised that this is the "old hat" 2D approach. This became difficult to do efficiently, since the 3D world can be modified by the player (so stuff can appear anywhere in 3D space) - so it seemed logical that I take advantage of the depth buffer. This meant that I didn't have to worry about rendering stuff in the correct order. However, I faced a problem. If you use GL_DEPTH_TEST and GL_BLEND together, it creates an effect where objects are blended with the background before they are "sorted" by z order (meaning that you get a weird kind of overlap where the transparency should be). Here's some pseudo code that should illustrate the problem (incidentally, I'm using libgdx for Android). create() { // ... // some other code here // ... Gdx.gl.glEnable(GL10.GL_DEPTH_TEST); Gdx.gl.glEnable(GL10.GL_BLEND); } render() { Gdx.gl.glClear(GL10.GL_COLOR_BUFFER_BIT | GL10.GL_DEPTH_BUFFER_BIT); Gdx.gl.glBlendFunc(GL10.GL_SRC_ALPHA, GL10.GL_ONE_MINUS_SRC_ALPHA); // ... // bind texture and create vertices // ... } So the question is: How do I solve the transparency overlap problem?

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• Emacs/Vim/Vi - do they have a place in modern software development ecosystem? [closed]

  - by Anton Gogolev

  Watching all those screencasts (and listening all those podcasts) with more-or-less famous hackers/programmers I hear that many of those use emacs/vi(m) for their daily work. Now, I myself tried using both emacs and vim, and I honestly cannot understand why would anybody use these for any kind of serious development. The most advertised feature is something along the lines of "you'll be able to work with text (meaning cutting, pasting, duplicating, moving, etc) up to ten times faster than with conventional IDEs", but I don't buy that. When has the success of a software project been defined by how fast a programmer can juggle lines in a text editor or by saving a couple of keystrokes here and there? Plugins and extensions? I bet nothing comes close to R# or IDEA in terms of refactoring support ("Rename" refactoring implemented by means of "Search and Replace" is not a refactoring IMO); others are trivial. Ubiquitous and available everywhere? So what? How often do you find yourself editing files over a 300 baud connection on an esoteric *nix installation without a VCS? So here goes: do said editors have a justified place in a modern software development ecosystem?

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• String patterns that can be used to filter and group files

  - by Louis Rhys

  One of our application filters files in certain directory, extract some data from it and export a document from the extracted data. The algorithm for extracting the data depends on the file, and so far we use regex to select the algorithm to be used, for example .*\.txt will be processed by algorithm A, foo[0-5]\.xml will be processed by algo B, etc. However now we need some files to be processed together. For example, in one case we need two files, foo.*\.xml and bar.*\.xml. Part of the information to be extracted exist in the foo file, and the other part in the bar file. Moreover, we need to make sure the wild card is compatible. For example, if there are 6 files foo1.xml foo23.xml bar1.xml bar9.xml bar23.xml foo4.xml I would expect foo1 and bar1 to be identified as a group, and foo23 and bar23 as another group. bar9 and foo4 has no pair, so they will not be treated. Now, since the filter is configured by user, we need to have a pattern that can express the above requirement. I don't think you can express meaning like above in standard regex. (foo|bar).*\.xml will match all 6 file above and we can't identify which file is paired for a particular file. Is there any standard pattern that can express it? Or any idea how to modify regex to support this, that can be implemented easily?

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• Squeezing all the SEO out of a URL as possible.

  - by John Isaacks

  I am working on an ecommerce site, I told our SEO consultant that I plan to make the URL scheme: /products/<id>/<name>. This is similar to Stackoverflow's URLs which are /questions/<id>/<title>. He asked me if I could change the URL scheme to /p/<id>/<name> instead. I know why he wants this change, the word "products" isn't needed to find the correct product, and it doesn't offer any SEO, so shortening it to just p would make the relevant keywords in the <name> weigh more. His main priority is maximizing SEO, but the part that I don't think he is considering is how this effects the semantics of the site. Also having the word "products" looks like it has meaning and a reason for being there, just having a p looks chaotic and ugly to me. I also don't think it makes that much of a difference does it? Stackoverflow doesn't use /q/<id>/<title> and they do just fine, I do realize that theres many factors at play here though, not just the URL. So I want some outside opinions on which is the better way and why?

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• How to subtract 1 from a orginal count in an ASP.NET gridview

  - by SAMIR BHOGAYTA

  I have a gridview that contains a count (whic is Quantity) were i have a button that adds a row under the orginal row and i need the sub row's count (Quantity) to subtract one from the orgianl row Quantity. EX: Before button click Orgianl row = 3 After click Orginal row = 2 Subrow = 1 Code: ASP.NET // FUNCTION : Adds a new subrow protected void gvParent_RowCommand(object sender, GridViewCommandEventArgs e) { if (e.CommandName.Equals("btn_AddRow", StringComparison.OrdinalIgnoreCase)) { // Get the row that was clicked (index 0. Meaning that 0 is 1, 1 is 2 and so on) // Objects can be null, Int32s cannot not. // Int16 = 2 bytes long (short) // Int32 = 4 bytes long (int) // Int64 = 8 bytes long (long) int i = Convert.ToInt32(e.CommandArgument); // create a DataTable based off the view state DataTable dataTable = (DataTable)ViewState["gvParent"]; for (int part = 0; part 1) { dataTable.Rows[part]["Quantity"] = oldQuantitySubtract - 1; // Instert a new row at a specific index DataRow dtAdd = dataTable.NewRow(); for (int k = 0; k dtAdd[k] = dataTable.Rows[part][k]; dataTable.Rows.InsertAt(dtAdd, i + 1); break; //dataTable.Rows.Add(dtAdd); } } // Rebind the data gvParent.DataSource = dataTable; gvParent.DataBind(); } }

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• How to remove seams from a tile map in 3D?

  - by Grimshaw

  I am using my OpenGL custom engine to render a tilemap made with Tiled, using a well spread tileset from the web. There is nothing fancy going on. I load the TMX file from Tiled and generate vertex arrays and index arrays to render the tilemap. I am rendering this tilemap as a wall in my 3D world, meaning that I move around with a fly camera in my 3D world and at Z=0 there is a plane showing me my tiles. Everything is working correctly but I get ugly seems between the tiles. I've tried orthographic and perspective cameras and with either I found particular sets of parameters for the projection and view matrices where the artifacts did not show, but otherwise they are there 99% of the time in multiple patterns, depending on the zoom and camera parameters like field of view. Here's a screenshot of the artifact being shown: http://i.imgur.com/HNV1g4M.png Here's the tileset I am using (which Tiled also uses and renders correctly): http://i.imgur.com/SjjHK4q.png My tileset has no mipmaps and is set to GL_NEAREST and GL_CLAMP_TO_EDGE values. I've looked around many articles in the internet and nothing helped. I tried uv correction so the uv fall at half of the texel, rather than the end of the texel to prevent interpolating with the neighbour value(which is transparency). I tried debugging with my geometry and I verified that with no texture and a random color in each tile, I don't seem to see any seams. All vertices have integer coordinates, i.e, the first tile is a quad from (0,0) to (1,1) and so on. Tried adding a little offset both to the UV and to the vertices to see if the gaps cease to exist. Disabled multisampling too. Nothing fixed it so far. Thanks.

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• Mutating Programming Language?

  - by MattiasK

  For fun I was thinking about how one could build a programming language that differs from OOP and came up with this concept. I don't have a strong foundation in computer science so it might be common place without me knowing it (more likely it's just a stupid idea :) I apologize in advance for this somewhat rambling question :) Anyways here goes: In normal OOP methods and classes are variant only upon parameters, meaning if two different classes/methods call the same method they get the same output. My, perhaps crazy idea, is that the calling method and class could be an "invisible" part of it's signature and the response could vary depending on who call's an method. Say that we have a Window object with a Break() method, now anyone (who has access) could call this method on Window with the same result. Now say that we have two different objects, Hammer and SledgeHammer. If Break need to produce different results based on these we'd pass them as parameters Break(IBluntObject bluntObject) With a mutating programming language (mpl) the operating objects on the method would be visible to the Break Method without begin explicitly defined and it could adopt itself based on them). So if SledgeHammer calls Window.Break() it would generate vastly different results than if Hammer did so. If OOP classes are black boxes then MPL are black boxes that knows who's (trying) to push it's buttons and can adapt accordingly. You could also have different permission sets on methods depending who's calling them rather than having absolute permissions like public and private. Does this have any advantage over OOP? Or perhaps I should say, would it add anything to it since you should be able to simply add this aspect to methods (just give access to a CallingMethod and CallingClass variable in context) I'm not sure, might be to hard to wrap one's head around, it would be kinda interesting to have classes that adopted themselves to who uses them though. Still it's an interesting concept, what do you think, is it viable?

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• What's a nice explanation for pointers?

  - by Macneil

  In your own studies (on your own, or for a class) did you have an "ah ha" moment when you finally, really understood pointers? Do you have an explanation you use for beginner programmers that seems particularly effective? For example, when beginners first encounter pointers in C, they might just add &s and *s until it compiles (as I myself once did). Maybe it was a picture, or a really well motivated example, that made pointers "click" for you or your student. What was it, and what did you try before that didn't seem to work? Were any topics prerequisites (e.g. structs, or arrays)? In other words, what was necessary to understand the meaning of &s and *, when you could use them with confidence? Learning the syntax and terminology or the use cases isn't enough, at some point the idea needs to be internalized. Update: I really like the answers so far; please keep them coming. There are a lot of great perspectives here, but I think many are good explanations/slogans for ourselves after we've internalized the concept. I'm looking for the detailed contexts and circumstances when it dawned on you. For example: I only somewhat understood pointers syntactically in C. I heard two of my friends explaining pointers to another friend, who asked why a struct was passed with a pointer. The first friend talked about how it needed to be referenced and modified, but it was just a short comment from the other friend where it hit me: "It's also more efficient." Passing 4 bytes instead of 16 bytes was the final conceptual shift I needed.

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• Why is NDA so hard to understand?

  - by Dave Campbell

  Maybe this concept is simpler for me because of all the jobs I've been on over the years requiring security clearances. I've signed quite a few NDA forms. Some for big companies, some for small, but the meaning of "NDA" remains constant: Non-Disclosure Agreement. To me, that takes no further explanation, but apparently it's confusing to some people, and I don't understand how you can be confused. The papers I signed with the U.S. Army in 1970 read "10 years and $10,000" for a violation... can't imagine what it's up to now, but THAT is a strict NDA :) So those things I've been told, I cannot talk about, period. Even if the entire world knows about them, I cannot speak about them until the information goes off NDA. An example was a Silverlight release a while back. It might have been Silverlight 3, I don't remember. Everyone was anxiously awaiting the release so they could post their material. Of course the entire world knew it was coming out and imminently so. Some enterprising folks had even found the bits on a server before the official announcement. So then the situation became: everyone knew about it, some were even coding with it and blogging about it and yet we couldn't talk about it. Scott Guthrie's posting about it opened the flood gates and then it went off NDA, but up until that moment, we were locked. Sitting out on the edge you're uninstalling and re-installing all the time and you get frustrated when things that used to work don't, but hey... those bits were still warm when you got 'em, and that's the fun. But that fun comes at a price, and the price is the NDA. Awkward yes, confusing no... See you at MIX10, and Stay in the 'Light! MIX10

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• How to achieve a loosely coupled REST API but with a defined and well understood contract?

  - by BestPractices

  I am new to REST and am struggling to understand how one would properly design a REST system to both allow for loose coupling but at the same time allow a consumer of a REST API to understand the API. If, in my client code, I issue a GET request for a resource and get back XML, how do I know what to do with that xml? e.g. if it contains <fname>John</fname><lname>Smith</lname> how do I know that these refer to the concept of "first name", "last name"? Is it up to the person writing the REST API to define in documentation some place what each of the XML fields mean? What if producer of the API wants to change the implementation to be <firstname> instead of <fname>? How do they do this and notify their consumers that this change occurred? Or do the consumers just encounter the error and then look at the payload and figure out on their own that it changed? I've read in REST in Practice that using a WADL tool to create a client implementation based on the WADL (and hide the fact that you're doing a distributed call) is an "anti-pattern". But I was planning to do this-- at least then I would have a statically typed API call that, if it changed, I would know at compile time and not at run time. Why is this a bad thing to generate client code based on a WADL? And how do I know what to do with the links that returned in the response of a POST to a REST API? What defines this contract and gives true meaning to what each link will do? Please help! I dont understand how to go from statically-typed or even SOAP/RPC to REST!

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• Why don't %MEM values add up to mem in top?

  - by ben

  I'm currently debugging performance issues with my VPS and for that I'm trying to understand which of the processes eat the most memory. Reading top, here's what I get: Mem: 366544k total, 321396k used, 45148k free, 380k buffers Swap: 1048572k total, 592388k used, 456184k free, 7756k cached PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 12339 ruby 20 0 844m 74m 2440 S 0 20.8 0:24.84 ruby 12363 ruby 20 0 844m 73m 1576 S 0 20.6 0:00.26 ruby 21117 ruby 20 0 171m 33m 1792 S 0 9.3 2:03.98 ruby 11846 ruby 20 0 858m 21m 1820 S 0 6.0 0:09.15 ruby 21277 ruby 20 0 219m 11m 1648 S 0 3.2 2:00.98 ruby 792 root 20 0 266m 10m 1024 S 0 3.0 1:40.06 ruby 532 mysql 20 0 234m 4760 1040 S 0 1.3 0:41.58 mysqld 793 root 20 0 250m 4616 984 S 0 1.3 1:20.55 ruby 586 root 20 0 156m 4532 848 S 0 1.2 6:17.10 god 12315 ruby 20 0 175m 2412 1900 S 0 0.7 0:07.55 ruby 3844 root 20 0 44036 2132 1028 S 0 0.6 1:08.22 ruby 10939 ruby 20 0 179m 1884 1724 S 0 0.5 0:08.33 ruby 4660 ruby 20 0 229m 1592 1440 S 0 0.4 2:55.46 ruby 3879 nobody 20 0 37428 964 520 S 0 0.3 0:01.99 nginx As you can see my memory is about 90% used (which is my issue) but when you add up the %MEM values, it goes to about 50-60% only. Same thing, RES doesn't add up to ~350mb. Why? Am I misunderstanding their meaning? Thanks

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• NDC Oslo

  - by Alan Smith

  Originally posted on: http://geekswithblogs.net/asmith/archive/2013/06/14/153136.aspx2013 has been a hectic year for conference presentations so far, NDC in Oslo has been the 6th conference I have attended, and my session there was my 11th conference presentation this year. I have been meaning to make the short trip over from Stockholm to NDC for a few years, and this was the first time I made it. I have heard a lot of great things about the event, and was impressed with the location, the sessions, and most of all the atmosphere around the event boots and during the party on Thursday evening. The session I was delivering was my “Grid Computing with 256 Windows Azure Worker Roles & Kinect” demo, which I have delivered at many events over the past 12 months. The demo went fine. I’m always a little nervous when I try to scale out the application to 256 worker roles, it almost always works well and the application will scale in minutes, but very occasionally there can be a longer delay due to the provisioning process in the Windows Azure data centers. This would not be an issue for many scenarios, but when standing on stage in front of a room full of developers you really want things to run smoothly. A number of people have suggested that I should pre-provision an environment so that it is guaranteed to be there when I run the demo during a session. For me the aim has always been to show the rapid scalability on cloud-based platforms live on stage. Pre-provisioning an environment may make for a more reliable demo but to me that would be cheating, and not half as much fun!

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• What is Mark Shuttleworth's "Easter eggs" blog a reference to? [closed]

  - by fluteflute

  I saw this blog post today, and I was wondering if there's some meaning within the Ubuntu community that I've missed? (I know what an easter egg is in a computer context.) One of our ducks has started dropping eggs in random locations in the garden. I don’t know which duck, but I assume it’s one of the new females we took in from the SPCA, who hasn’t figured out “nesting” yet. I do love ‘em but they’re not African Grey’s in the IQ department. Anyhow, I think I finally understand why people hide eggs in the garden at Easter. Because ducks used to do it for them! I suppose, for millennia, this has been the season to go hunting for eggs. Now we just substitute chocolate ones instead. For the moment, I’ve kept them in a cool shady spot while I keep an eye out for an actual nest. If a polecat doesn’t find them first, I may be able to slip them onto the nest in time for them to get hatched along with some cousins.

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• Precising definition of programming paradigm

  - by Kazark

  Wikipedia defines programming paradigm thus: a fundamental style of computer programming which is echoed in the descriptive text of the paradigms tag on this site. I find this a disappointing definition. Anyone who knows the words programming and paradigm could do about that well without knowing anything else about it. There are many styles of computer programming at many level of abstraction; within any given programming paradigm, multiple styles are possible. For example, Bob Martin says in Clean Code (13), Consider this book a description of the Object Mentor School of Clean Code. The techniques and teachings within are the way that we practice our art. We are willing to claim that if you follow these teachings, you will enjoy the benefits that we have enjoyed, and you will learn to write code that is clean and professional. But don't make the mistake of thinking that we are somehow "right" in any absolute sense. Thus Bob Martin is not claiming to have the correct style of Object-Oriented programming, even though he, if anyone, might have some claim to doing so. But even within his school of programming, we might have different styles of formatting the code (K&R, etc). There are many styles of programming at many levels. Sp how can we define programming paradigm rigorously, to distinguish it from other categories of programming styles? Fundamental is somewhat helpful, but not specific. How can we define the phrase in a way that will communicate more than the separate meanings of each of the two words—in other words, how can we define it in a way that will provide additional meaning for someone who speaks English but isn't familiar with a variety of paradigms?

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• MATLAB: Best fitness vs mean fitness, initial range

  - by Sa Ta

  Based on the example of Rastrigin's function. At the plot function, if I chose 'best fitness', on the same graph 'mean fitness' will also be plotted. I understand well about 'best fitness' whereby it plots the best function value in each generation versus iteration number. It will reach value zero after some times. I don't understand about 'mean fitness'in the graph plotted. What do those 'mean fitness' values mean? How does the 'mean fitness' graph help to understand Rastrigin's function? What are the meaning of the term initial population, initial score and initial range? I wish to have a better understanding of these terms. The default value for initial range is [0,1]. Does it mean that 0 is the lower bound (lb) and 1 is the upper bound (ub)? Do these values interfere with the lb and ub values I set in the constraints? I try to better understand about lb and ub. If my lb is 0 and ub is 5, does it mean that my final point values will be within 0 and 5? If I know the lb and ub for my problem is between 0 and 5, do I just set the initial range as [0,5] at all times and may I assume that this is the best option for initial range, and I need not try it with any other values?

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• How to simulate pressure with particles?

  - by BeachRunnerJoe

  I'm trying to simulate pressure with a collection of spherical particles in a Unity game I'm building. A couple notes about the problem: The goal is to fill a constantly changing 2d space/void with small, frictionless spheres. The game is trying to simulate the ever-growing pressure of more objects being shoved into this space. The level itself is constantly scrolling from left to right, meaning if the space's dimensions are not changed by the user it will automatically get smaller (the leftmost part of the space will continually scroll off-screen). I'm wondering what some approaches are that I can take to tackling these problems... Knowing when to detect when there is space to fill and then add spheres to the space. Removing spheres from the space when it is shrinking. Strategies to simulate pressure on the spheres such that they "explode outwards" when more space is created. The current approach I am contemplating is using a constantly moving wall, that is off screen and moves with the screen, as this image illustrates: . This moving wall will push and trap the spheres into the space. As for adding new spheres, I was going to have either (1) spheres replicate themselves upon detecting free space, OR (2) spawn them at the left side of the space (where the wall is) - pushing the rest of the spheres to fill the space. I foresee problems with idea #1 because this likely wouldn't really create/simulate pressure; idea #2 seems more promising, but raises the question of how to provide a location for these new sphere particles to spawn (and the ramifications of spawning them when there IS no space). Thanks so much in advance for your wisdom!

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• Spring to Java EE, Part Three - new tech article on otn/java

  - by Janice J. Heiss

  In a new article up on otn/java, Java EE expert David Heffelfinger continues his series exploring the relative strengths and weaknesses of Java EE and Spring. Here, he demonstrates how easy it is to develop the data layer of an application using Java EE, JPA, and the NetBeans IDE instead of the Spring Framework.In the first two parts of the series, he generated a complete Java EE application by using JavaServer Faces (JSF) 2.0, Enterprise JavaBeans (EJB) 3.1, and Java Persistence API (JPA) 2.0 from Spring’s Pet Clinic MySQL schema, thus showing how easy it is to develop an application whose functionality equaled that of the Spring sample application.In his new article, Heffelfinger tweaks the application to make it more user friendly.From the article:“The generated application displays primary keys on some of the pages, and these keys are surrogate primary keys—meaning that they have no business value and are used strictly as a unique identifier—so there is no reason why they should be visible to the user. In addition, we will modify some of the generated labels to make them more user-friendly.”He concludes the article with a summary:“The Java EE version of the application is not a straight port of the Spring version. For example, the Java EE version enables us to create, update, and delete veterinarians as well as veterinary specialties, whereas the Spring version of the application enables us only to view veterinarians and specialties. Additionally, the Spring version has a single page for managing/viewing owners, pets, and visits, whereas the Java EE version of the application has separate pages for each of these entities.The other thing we should keep in mind is that we didn’t actually write a lot of the code and markup for the Java EE version of the application, because the bulk of it was generated by the NetBeans wizard.” Have a look at the complete article here.

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• UML Diagrams of Multi-Threaded Applications

  - by PersonalNexus

  For single-threaded applications I like to use class diagrams to get an overview of the architecture of that application. This type of diagram, however, hasn’t been very helpful when trying to understand heavily multi-threaded/concurrent applications, for instance because different instances of a class "live" on different threads (meaning accessing an instance is save only from the one thread it lives on). Consequently, associations between classes don’t necessarily mean that I can call methods on those objects, but instead I have to make that call on the target object's thread. Most literature I have dug up on the topic such as Designing Concurrent, Distributed, and Real-Time Applications with UML by Hassan Gomaa had some nice ideas, such as drawing thread boundaries into object diagrams, but overall seemed a bit too academic and wordy to be really useful. I don’t want to use these diagrams as a high-level view of the problem domain, but rather as a detailed description of my classes/objects, their interactions and the limitations due to thread-boundaries I mentioned above. I would therefore like to know: What types of diagrams have you found to be most helpful in understanding multi-threaded applications? Are there any extensions to classic UML that take into account the peculiarities of multi-threaded applications, e.g. through annotations illustrating that some objects might live in a certain thread while others have no thread-affinity; some fields of an object may be read from any thread, but written to only from one; some methods are synchronous and return a result while others are asynchronous that get requests queued up and return results for instance via a callback on a different thread.

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• System boots in console + login loop

  - by Imagicien

  I messed up my system while trying to fix permission problems for setting up a LAMP local server. I tried this solution: How to avoid using sudo when working in /var/www? without success. Then I saw this solution: Permissions issue: how can Apache access files in my Home directory? I understood that I had to change the permissions of my root directory (among others), so I executed: sudo chmod 710 / I also changed the user group on / to www-data. I also did these operations on /home. I'm pretty sure one of those commands broke something, because it's the last commands I executed, and after that, my system showed strange/broken behavior: Firefox stopped showing pages Some icons got replaced by an red X icon (meaning "Icon not found" I guess) Applications refused to launch (no reaction) After rebooting: I got a strange graphical message talking about not being able to mount something, asking me if I wanted to wait, and talking about /tmp (I forgot the message since I was in shock) My system now boots in console, and when I login, it flashes unsignificant stuff* before re-asking me to login. My important data is on Ubuntu One. I'd prefer not having to reinstall from scratch. Is there a way to regain access to my system? Thanks a lot for your help. *Looks like a terminal header with the name of the OS and other info. Doesn't seem important.

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• Relationships in a Chen ERD

  - by Nibroc A Rehpotsirhc

  I am working on a Chen ERD to model our organizations merchandise. Our central entity is a Style. We have supplemental entities of Color and Season. I am defining our assortment as the relationship between these three entities, and this relationship itself will have attributes and is defined by the three entities which participate in the mandatory relationship. The rules are; Many Styles can be offered in a Season, and a Style can be offered in many Seasons. Within a Season, a Style can be offered in Many Colors. I then have 2 other entities, one of which I believe is a weak entity, Climate, and the other may be weak, but I am not sure, this being Transaction Channel. I am thinking of these as relationships off of a relationship? Meaning, for a given Style/Color combination offered in a Season, it can be available through 1 or more Transaction Channels. Additionally, within a season, a given Style/Color combination can be intended for 1 or more Climates. Is it valid to have relationships off of relationships? Or does this requirement dictate that I should think of this Style/Color/Season relationship as an entity itself, and define the relationships to Climate and Transaction Channel off of this entity?

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• Strange spam posts not making sense

  - by Paaland

  I'm running a web site with a forum where one small part is open for posting from unregistered users. The site uses captcha, but still some spam posts get through every day. Here is the thing. All of the messages follow the same pattern, but all also come from different IP's. That makes me thing this is some sort of automated scripted "attack" from a botnet of some sorts. The strange thing is that all the messages start with six random characters and contains a couple of links. The words have no meaning and the domains in the links does not even exist. Why would anyone use time and resources spreading these things? Below you can see two of these messages: A5Zfs6 exrzvrbspntz, [url=http://nktqoqllnuab.com/]nktqoqllnuab[/url], [link=http://wtrenldadvsy.com/]wtrenldadvsy[/link], [http://rnlrqfgdvdot.com/] O2oLpL nqeffxhryfdk, [url=http://jutyurbpfxow.com/]jutyurbpfxow[/url], [link=http://jpcdtmdalpow.com/]jpcdtmdalpow[/link], [http://qopqwqxwjdjx.com/] Since all the messages come from different IP's I can't see blocking those will help much. For now I'm considering just dropping all messages following this pattern since it's quite easy to match with a regexp. Have anyone else seen these kinds of messages or know the point of posting them?

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• Where does jQuery fit-in with frameworks like JavaScriptMVC, BackboneJS, SproutCore and Knockout?

  - by Prisoner ZERO

  I have been happily using JQuery for the last 2 years and have been quite sucessful creating some really cool functionality with it...so I am very comfortable with it. I also beleive the future of the web will continue on the current client-side path. However... The next challenge seems to be coming in the form of various controller frameworks: KnockoutJS, BackboneJS, SproutCore, JavaScriptMVC (the list goes on). Additonally, there are some great AMD Loader tools for use like RequireJS or LabJS etc. However, jQuery now has define and then capabilities baked-in. It's getting harder-and-harder to keep track of it all... And now, my task seems to be to evaluate/decide-on a strategic-direction for using some form of either an MVC or MVVM framework client-side...but I have so many questions. Where does JQuery fit-in with the various controller-frameworks mentioned above? Is JQuery used alongside each or do some of them have their own 'JQuery-styled version' baked-in? Are tools like RequireJS still needed if you implement one of the various controller-frameworks mentioned above? Does the define and then capabilities baked-into JQuery now supercede the AMD Loader mentioned above? Which one seems most modular? (see notes below) NOTES: One thing I don't want in any future-framework is the requirement of having to take-in vast amounts of functionality that I don't use. Meaning, I would rather use a framework that is truly modular. For example, to use jQuery UI you have to take-in a lot other core libraries that you might not actually use. I will be experimenting with each one, but some REAL feedback would be great. I've seen some 'similar' questions, but none have really answered the above skew. Thanks in advance!

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