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• Games without a(n explicit) game loop

  - by Davy8

  Most game development happens with a main game loop. Are there any good articles/blog posts/discussions about games without a game loop? I imagine they'd mostly be web games, but I'd be interested in hearing otherwise. (As a side note, I think it's really interesting that the concept is almost exclusively used in gaming as far as I'm aware, perhaps that may be another question.) Edit: I realize there's probably a redraw loop somewhere. I guess what I really mean is a loop that is hidden to you. Frames are something you as the developer are not concerned with as you're working on a higher level of abstraction. E.g. someLootItem.moveTo(inventory, someAnimatationType) and that will move from the loot box to your inventory using the specified animation type without the game developer having to worry about the implementation details of that animation. Maybe that's how "real" games end up working, but from reading most tutorials they seem to imply a much more granular level of control is used, but that might just be an artifact of being a tutorial.

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• Yelp, Google's API for restaurants help

  - by chris

  Ok I have looked into this, and I'm not sure if anyone else has experience with it. I'm having termendous difficulties with Yelp and Google's API. To help explain what I am trying to do here is the concept of the website. We would have to pull restaurants based on user distance, and then randomize them based on quality of restaurant based on feedback from review websites (Yelp, Google, urbanspoon, zagat, opentable, kudzu, yahoo - doesn't have to be from all), and feedback from our users (on results page for the random restaurant users can select good recommendation/bad recommendation). There’s a lot we could calculate for our formula. Things that will dictate your results will be based on if you’re at home or work. If you’re at home you will have more time to drive out to the city to grab some dinner or lunch. If you’re at work we would have to recommend restaurants nearby as lunch is typically 30 minutes to a hour. A 30 minute lunch would require take out most likely or quick service. A hour lunch break you could dine in at a local fine dining restaurant. So in a nutshell, user comes to website. Select if they're at home or work, click submit and we will have a random restaurant selected for them to go. If they don't like it they can click retry and a new restaurant can show. The issue I am having is using the API to gather all the restaurants in the US. I know it can be done because there are similiar websites/apps that pull restaurants that are closest to you such as Ness, Alfred, and I believe there's two more but I can't remember the names. Anyone know if this can be accomplish?

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• What are some techniques I can use to refactor Object Oriented code into Functional code?

  - by tieTYT

  I've spent about 20-40 hours developing part of a game using JavaScript and HTML5 canvas. When I started I had no idea what I was doing. So it started as a proof of concept and is coming along nicely now, but it has no automated tests. The game is starting to become complex enough that it could benefit from some automated testing, but it seems tough to do because the code depends on mutating global state. I'd like to refactor the whole thing using Underscore.js, a functional programming library for JavaScript. Part of me thinks I should just start from scratch using a Functional Programming style and testing. But, I think refactoring the imperative code into declarative code might be a better learning experience and a safer way to get to my current state of functionality. Problem is, I know what I want my code to look like in the end, but I don't know how to turn my current code into it. I'm hoping some people here could give me some tips a la the Refactoring book and Working Effectively With Legacy Code. For example, as a first step I'm thinking about "banning" global state. Take every function that uses a global variable and pass it in as a parameter instead. Next step may be to "ban" mutation, and to always return a new object. Any advice would be appreciated. I've never taken OO code and refactored it into Functional code before.

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• Ubuntu One - Files API - Cloud - More detailed info somehwere?

  - by Brian McCavour

  I am just starting on a mobile app for Ubuntu One, and I'm reviewing the info at https://one.ubuntu.com/developer/files/store_files/cloud I find the information a bit lacking though. It's a nice reference, but for someone not familiar with it, I had to goggle search to find out what a "volume" was exactly (its kind of obvious, but never hurts to know the specifics) There's also things like: GET /api/file_storage/v1/volumes Return a JSON list of Volume Representations, one for each volume. A volume is a synced folder, or the Ubuntu One folder, owned by the user. Note that all volume paths begin with ~.: ... but there's no such thing as a JSON "list". Does it mean array ? And other things... So I was wondering if here existed another page with more detailed information. Maybe some sample request / responses or something? I could just write a little proof of concept app to answer some of these questions... but I prefer not to unless I have to. Thanks

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• How to animate the sprite along with action in Cocos2d?

  - by user1201239

  Cocos2d-android - I have an animation which has 5 Frames they are close cropped images. Now I want Sprite to do animation as well as Move in X direction.i.e. I have a player running which gets collided with obstacle and falls down .. Now I want sprite to run animation as well as moveBy in -ve x direction gameOverAnimation =CCSprite.sprite("gmovr00") gameOverAnimation.setAnchorPoint(0, 0); gameOverAnimation.setPosition(340.0f, 200.0f); addChild(gameOverAnimation,10); CCIntervalAction action1 = CCAnimate.action(mEndAnimation, false); action1.setDuration(1.0f); CCIntervalAction delay = CCDelayTime.action(0.68f); CCMoveBy actionBy = CCMoveBy.action(1.0f, CGPoint.ccp(-340,0)); CCIntervalAction seq1 = CCSpawn.actions(action1,actionBy); //CCSpawn spawn = CCSpawn.actions(action1, actionBy); CCSequence sequence1 = CCSequence.actions(seq1,CCCallFuncN.action(this,"gameOver")); gameOverAnimation.runAction(sequence1); Above code makes animation run first then moved in y direction Thanks for the help.. And can some one explaing me the concept of time with frame Animation or good example ?

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• How to write code that communicates with an accelerator in the real address space (real mode)?

  - by ysap

  This is a preliminary question for the issue, where I was asked to program a host-accelerator program on an embedded system we are building. The system is comprised of (among the standard peripherals) an ARM core and an accelerator processor. Both processors access the system bus via their bus interfaces, and share the same 32-bit global physical memory space. Both share access to the system's DRAM through the system bus. (The computer concept is similar to Beagleboard/raspberry Pie, but with a specialized accelerator added) The accelerator has its own internal memory (SRAM) which is exposed to the system and occupies a portion of the global address space (as opposed to how a graphics card would talk to teh CPU via a "small" aperture in the system memory space). On the ARM core (the host) we plan on running Ubuntu 12.04. The mode of operation of communicating between the processors should be that the host issues memory transactions on the system bus that are targeted at the accelerator internal memory. As far as my understanding goes, if I write a program for the host that simply writes to the physical address of the accelerator, most chances are that the program will crash due to a segmentation violation. So, I assume that I need some way of communicating with the device in real mode. What is the easiest way to achieve this mode of operation?

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• C++ program...overshoots? [migrated]

  - by Zdrok

  I'm decent at C++, but I may have missed some nuance that applies here. Or maybe I completely missed a giant concept, I have no idea. My program was instantly crashing ("blah.exe is not responding") about 1/5 times it was run (other times it ran completely fine) and I tracked the problem down to a constructor for a world class that was called once in the beginning of the main function. Here is the code (in the constructor) that causes the problem: int ii; for(ii=0;ii<=255;ii++) { cout<<"ent "<<ii<<endl; entity_list[ii]=NULL; } for(ii=0;ii<=255;ii++) { cout<<"sec "<<ii<<endl; sector_list[ii]=NULL; } entity_list[0] = new Entity(0,0); entity_list[0]->_world = this; Specifically the second for loop. The cout references are new for the sake of telling where it is having trouble. It would print the entire "ent 1" to "ent 255" and then "sec 1" to "sec 255" and then crash right after, as if it was going for a 257th run through of the second for loop. I set the second for loop to go until "ii<=254" which stopped all crashes. Does C++ code tend to "overshoot" for loops or something? What is causing it to crash at this specific loop seemingly at random? By the way, entity_list and sector_list point to classes called Entity and Sector, respectively, but they are not constructing anything so I didn't think it would be relevant. I also have a forward declaration for the Entity class in a header for this, but since none were being constructed I didn't think it was relevant either. EDIT: It was due to the new Entity line, I assumed wrongly that the fact that altering the for statement to 254 fixed the crashes meant that it had to be there. I still don't understand why the for loop is related, though.

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• What is the breakdown of jobs in game development?

  - by Destry Ullrich

  There's a project I'm trying to start for Indie Game Development; specifically, it's going to be a social networking website that lets developers meet through (It's a secret). One of the key components is showing what skills members have. Question: I need to know what MAJOR game development roles are not represented in the following list, keeping in mind that many specialist roles are being condensed into more broad, generalist roles: Art Animator (Characters, creatures, props, etc.) Concept Artist (2D scenes, environments, props, silhouettes, etc.) Technical Artist (UI artists, typefaces, graphic designers, etc.) 3D Artist (Modeling, rigging, texture, lighting, etc.) Audio Composer (Scores, music, etc.) Sound Engineer (SFX, mood setting, audio implementation, etc.) Voice (Dialog, acting, etc.) Design Creative Director (Initial direction, team management, communications, etc.) Gameplay Designer (Systems, mechanics, control mapping, etc.) World Designer (Level design, aesthetics, game progression, events, etc.) Writer (Story, mythos, dialog, flavor text, etc.) Programming Engine Programming (Engine creation, scripting, physics, etc.) Graphics Engineer (Sprites, lighting, GUI, etc.) Network Engineer (LAN, multiplayer, server support, etc.) Technical Director (I don't know what a technical director would even do.) Post Script: I have an art background, so i'm not familiar with what the others behind game creation actually do. What's missing from this list, and if you feel some things should be changed around how so?

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• C++ Succinctly now available!

  - by Michael B. McLaughlin

  Over the summer I worked with SyncFusion to create an eBook based off of my C# to C++ guide for their free Succinctly Series of eBooks. Today the result, C++ Succinctly, was published for download. It is a free (registration required; they make tools and libraries for .NET development so you might get an occasional email from them – I’ve been signed up for a few months and have had maybe 3 emails total so it’s not horrible super spam or anything ) and you can download it as a PDF or a Kindle .MOBI file (or both). I’m excited with how it turned out and enjoyed working with the people at SyncFusion. The book contains a total of 20 code samples, which you can download from BitBucket (there’s a link very early in the book). Almost all of the code is also inline in the book itself so that you don’t need to worry about flipping back and forth between your dev machine and your eReader (but if you want to try to understand a concept better, you can easily download the code, open it up in VS 2012, and play around with it to see what happens when you tinker with things). The code does require Visual Studio 2012 because of its expanded support for C++11 features and since I wrote all of the samples as Console programs for clarity and compactness, you will need a version that supports C++ desktop development (currently VS 2012 Pro, Premium, or Ultimate). Sometime this Fall, Microsoft will be releasing Visual Studio 2012 Express for Windows Desktop which should provide a free way to use the samples. That said, I tested all of the samples with MinGW and only the StorageDurationSample will not compile with it due to the thread-local storage code. If you comment that out then you can compile and run all the samples with MinGW (or using a recent version of GCC in a GNU/Linux environment, or any other C++ compiler that provides the same level of C++11 support that Visual Studio 2012 does). I hope it proves helpful to those of you who choose to check it out!

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• Is Akka a good solution for a concurrent pipeline/workflow problem?

  - by herpylderp

  Disclaimer: I am brand new to Akka and the concept of Actors/Event-Driven Architectures in general. I have to implement a fairly complex problem where users can configure a "concurrent pipeline": Pipeline: consists of 1+ Stages; all Stages execute sequentially Stage: consists of 1+ Tasks; all Tasks execute in parallel Task: essentially a Java Runnable As you can see above, a Task is a Runnable that does some unit of work. Tasks are organized into Stages, which execute their Tasks in parallel. Stages are organized into the Pipeline, which executes its Stages sequentially. Hence if a user specifies the following Pipeline: CrossTheRoadSafelyPipeline Stage 1: Look Left Task 1: Turn your head to the left and look for cars Task 2: Listen for cars Stage 2: Look right Task 1: Turn your head to the right and look for cars Task 2: Listen for cars Then, Stage 1 will execute, and then Stage 2 will execute. However, while each Stage is executing, it's individual Tasks are executing in parallel/at the same time. In reality Pipelines will become very complicated, and with hundreds of Stages, dozens of Tasks per Stage (again, executing at the same time). To implement this Pipeline I can only think of several solutions: ESB/Apache Camel Guava Event Bus Java 5 Concurrency Actors/Akka Camel doesn't seem right because its core competency is integration not synchrony and orchestration across worker threads. Guava is great, but this doesn't really feel like a subscriber/publisher-type of problem. And Java 5 Concurrency (ExecutorService, etc.) just feels too low-level and painful. So I ask: is Akka a strong candidate for this type of problem? If so, how? If not, then why, and what is a good candidate?

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• Turn Based Event Algorithm

  - by GamersIncoming

  I'm currently working on a small roguelike in XNA, which sees the player in a randomly generated series of dungeons fending off creeps, as you might expect. As with most roguelikes, the player makes a move, and then each of the creeps currently active on screen will make a move in turns, until all creeps have updated, and it return's to the player's go. On paper, the simple algorithm is straightforward: Player takes turn Turn Number increments For each active creep, update Position Once all active creeps have updated, allow player to take next turn However, when it comes to actually writing this in more detail, the concept becomes a bit more tricky for me. So my question comes as this: what is the best way to handle events taking turns to trigger, where the completion of each last event triggers the next, when dealing with a large number of creeps (probably stored as an array of an enemy object), and is there an easier way to create some kind of engine that just takes all objects that need updating and chains them together so their updates follow suit? I'm not asking for code, just algorithms and theory in the direction of objects triggering updates one after the other, in a turn based manner. Thanks in advance. Edited: Here's the code I currently have that is horrible :/ if (player.getTurnOver() && updateWait == 0) { if (creep[creepToUpdate].getActive()) { creep[creepToUpdate].moveObject(player, map1); updateWait = 10; } if (creepToUpdate < creep.Length -1) { creepToUpdate++; } else { creepToUpdate = 0; player.setTurnOver(false); } } if (updateWait > 0) { updateWait--; }

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• I'm a Subversion geek, why should I consider or not consider Mercurial or Git or any other DVCS?

  - by user2567

  I try to understand the benefits of distributed version control system (DVCS). I found Subversion Re-education and this article by Martin Fowler very useful. Mercurial and others DVCS promote a new way of working on code with changesets and local commits. It prevents from merging hell and other collaboration issues We are not affected by this as I practice continuous integration and working alone in a private branch is not an option, unless we are experimenting. We use a branch for every major version, in which we fix bugs merged from the trunk. Mercurial allows you to have lieutenants I understand this can be useful for very large projects like Linux, but I don't see the value in small and highly collaborative teams (5 to 7 people). Mercurial is faster, takes less disk space and full local copy allows faster logs & diffs operations. I'm not concerned by this either, as I didn't notice speed or space problems with SVN even with very large projects I'm working on. I'm seeking for your personal experiences and/or opinions from former SVN geeks. Especially regarding the changesets concept and overall performance boost you measured. UPDATE (12th Jan): I'm now convinced that it worth a try. UPDATE (12th Jun): I kissed Mercurial and I liked it. The taste of his cherry local commits. I kissed Mercurial just to try it. I hope my SVN Server don't mind it. It felt so wrong. It felt so right. Don't mean I'm in love tonight. FINAL UPDATE (29th Jul): I had the privilege to review Eric Sink's next book called Version Control by Example. He finished to convince me. I'll go for Mercurial.

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• Proper XAML for Windows 8 Applications [closed]

  - by Jaapjan

  Traditionally, my programs do their work in the background and when I do have to make an interface for some reason, they often do not need to be complex which means I can use a simple Windows Forms or console application. But lets be honest-- Windows Forms? That is so ... ancient! Instead I have been looking at Windows 8. A new interface, different, maybe better-- but fun to give a try. Which means XAML. Now, XAML isn't all that hard in concept. Panel here, button there-- A smattering of XML. My question in short: Where can I find resources that teach me how to write good XAML code for Windows 8 applications? The long version: How do I combine XAML constructs to achieve effects? Horizontal panels with multiple sections you can scroll through with your finger, the proper way? How should you use default style resources Windows 8 might give you by default? How do I properly create a panel with user info on the right? Left aligned stackpanels with embedded dockpanels? Yes? No? Why?

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• github team workflow - to fork or not?

  - by aporat

  We're a small team of web developers currently using subversion but soon we're making a switch to github. I'm looking at different types of github workflows, and we're not sure if the whole forking concept in github for each developer is such a good idea for us. If we use forks, I understand each developer will have his own private remote & local repositories. I'm worried it will make pushing changesets hard and too complex. Also, my biggest concern is that it will force each developer to have 2 remotes: origin (which is the remote fork) and an upstream (which is used to "sync" changes from the main repository). Not sure if it's such a easy way to do things. This is similar to the workflow explained here: https://github.com/usm-data-analysis/usm-data-analysis.github.com/wiki/Git-workflow If we don't use forks, we can probably get by fine by using a central repo creating a branch for each task we're working on, and merge them into the development branch on the same repository. It means we won't be able to restrict merging of branches and might be a little messy to have many branches on the central repository. Any suggestions from teams who tried both workflow?

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• Do the benefits of Resin/Quercus outweigh the overhead?

  - by Craige

  Lately, I've been looking more and more into Resin + Quercus as a technology to develop an application of mine. The reason I started looking into it was that this application has high reporting needs, a lot of which cannot (or realistically, should not) be created in real-time. Java would offer a nice backend to queue and generate reports. Also, with Quercus I would be able to develop my data models in Hibernate, and use them "from PHP", thus effectively stretching these models across front and back-end. This same concept would also apply to any front/back-end common business logic, which could be developed in Java libraries. Now, the downside is that whichever front-end (PHP) MVC Framework I choose (my goal was Symfony 2), it is unlikely to work without some heavy modification, if it can work at all. Quercus is a pretty close implementation of PHP, and is supposed to be compatible with PHP5.3, so namespaces and closures SHOULDN'T be a problem, but when I tried to run an existing Symfony 1.4 app, I failed miserably. So, my question to you is, do you think the benefits of Resin + Quercus outweigh the overhead of using a not-so-perfect/stable implementation of PHP? If this were your application, and your goal was and end-product, rather than educational purposes, what would you decide?

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• Permissions issue: how can Apache access files in my Home directory?

  - by richzilla

  I know file permissions have been covered on here before, but im struggling to get my head around the concept for my scenario. I created the files on an old ubuntu installation. Ive copied the files into my new ubuntu installation and put them in my webroot. When i attempt to run the files (theyre PHP files) i get an error relating to permissions in an attempt to fix this, i assumed that they must still be owned by the previous owner, so i ran chown -R on the directory, with my username as an argument, in order to take ownership of all of the files in the directory. It should be noted that the usernames between new and old ubuntu installations were the same. When i attempt to run the files again, same problem: 500 error due to permissions problems. Can anyone tell me what other steps i should take? The webroot for my apache installation is inside my home folder. If i create new files in my webroot, they also work as expected, its only the old files that are causing the problem.

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• What should a programmer's yearly routine be to maximize their technical skills?

  - by sguptaet

  2 years ago I made a big career change into programming. I learned various technologies on my own without any prior experience. I really love it and feel lucky with all the resources around us to help us learn. Books, courses, open-source, etc. There are so many avenues. I'm wondering what a good routine would be to follow to maximize my software development skills. I don't believe just building software is the way, because that leaves no time for learning new concepts or technologies. I'm looking for an answer like this: Take a new concept sabbatical/workshop 2 weeks per year. Read 1 theoretical and 1 practical programming book per year. Learn 1 additional language every 2 years. Take a 1 week vacation every 6 months. Etc. I realize that the above might sound naive and unrealistic as there are so many factors. But I'd like to know the "recipe" that you think is best that will serve as a guide for people.

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• At the Java DEMOgrounds - ZeroTurnaround and its LiveRebel 2.5

  - by Janice J. Heiss

  At the ZeroTurnaround demo, I spoke with Krishnan Badrinarayanan, their Product Marketing Manager. ZeroTurnaround, the creator of JRebel and LiveRebel, describes itself on their site as a company “dedicated to changing the way the world develops, tests and runs Java applications."“We just launched LiveRebel 2.5 today,” stated Badrinarayanan, “which enables companies to embrace the concept and practice of continuous delivery, which means having a pipeline that takes products right from the developers to an end-user, faster, more frequently -- all the while ensuring that it’s a quality product that does not break in production. So customers don’t feel the discontinuity that something has changed under them and that they can’t deal with the change. And all this happens while there is zero down time.”He pointed out that Salesforce.com is not useable from 3 a.m. to 5 a.m. on Saturday because they are engaged in maintenance. “With LiveRebel 2.5, you can unify the whole delivery chain without having any downtime at all,” he said. “There are many products that tell customers to take their tools and change how they work as an organization so that you they have to conform to the way the tool prescribes them to work as an application team. We take a more pragmatic approach. A lot of companies might use Jenkins or Bamboo to do continuous integration. We extend that. We say, take our product, take LiveRebel okay, and integrate it with Jenkins – you can do that quickly, so that, in half a day, you will be up and running. And let LiveRebel automate your deployment processes and all the automated tasks that go with it. Right from tests to the staging environment to production -- all with zero downtime and with no impact on users currently using the system.” “So if you were to make the update right now and you had 100 users on your system, they would not even know this was happening. It would maintain their sessions and transfer them over to the new version, all in the background.”

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• I don't understand how TDD helps me get a good design if I need a design to start testing it

  - by Michael Stum

  I'm trying to wrap my head around TDD, specifically the development part. I've looked at some books, but the ones I found mainly tackle the testing part - the History of NUnit, why testing is good, Red/Green/Refactor and how to create a String Calculator. Good stuff, but that's "just" Unit Testing, not TDD. Specifically, I don't understand how TDD helps me get a good design if I need a Design to start testing it. To illustrate, imagine these 3 requirements: A catalog needs to have a list of products The catalog should remember which products a user viewed Users should be able to search for a product At this points, many books pull a magic rabbit out of a hat and just dive into "Testing the ProductService", but they don't explain how they came to the conclusion that there is a ProductService in the first place. That is the "Development" part in TDD that I'm trying to understand. There needs to be an existing design, but stuff outside of entity-services (that is: There is a Product, so there should be a ProductService) is nowhere to be found (e.g., the second requirement requires me to have some concept of a User, but where would I put the functionality to remind? And is Search a feature of the ProductService or a separate SearchService? How would I know which I should choose?) According to SOLID, I would need a UserService, but if I design a system without TDD, I might end up with a whole bunch of Single-Method Services. Isn't TDD intended to make me discover my design in the first place? I'm a .net developer, but Java resources would also work. I feel that there doesn't seem to be a real sample application or book that deals with a real line of business application. Can someone provide a clear example that illustrates the process of creating a design using TDD?

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• Making efficeint voxel engines using "chunks"

  - by Wardy

  Concept I'm currently looking in to how voxel engines work with a view to possibly making one myself. I see a lot of stuff like this ... https://sites.google.com/site/letsmakeavoxelengine/home/chunks ... which talks about how to go about reducing the draw calls. What I can't seem to understand is how it actually saves draw call counts on the basis of the logic being something like this ... Without chunks foreach voxel in myvoxels DrawIfVisible() With Chunks foreach chunk in mychunks DrawIfVisible() which then does ... foreach voxel in myvoxels DrawIfVisible() So surely you saved nothing ?!?! You still make a draw call for each visible voxel do you not? A visible voxel needs a draw call in either scenario. The only real saving I can see is that the logic that evaluates a chunk will be able to determine if a large number of voxels are visible or not effectively saving a bit of "is this chunk visible" cpu time. But it's the draw calls that interest me ... The fewer of those, the faster the application. EDIT: In case it makes any difference I will probably be using XNA (DX not OpenGL) for my engine so don't consider my choice of example in the link above my choice of technology. But this question is such that I doubt it would matter.

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• What are most demanded web-development languages today for startups?

  - by Liston Catch

  What technologies are in demand nowaydas for web-development for web-startups? For frontend its all clear: HTML5, JS, AJAX, JQuery. But what about backend? What languages (and frameworks) should I consider using? I am not asking "which language is best", I just need a list of modern languages and frameworks (and not Pascal, Delphi or Basic) which are demanded and well-payed. UPD: I totally decline the "it's all about logic, not about language. language is just a tool" concept. While THEORETICALLY it's true, in reality the time you need to study required frameworks is counted by months, so language DOES matter indeed. That's why I made this topic UPD 2: Mason Wheeler, so you seriously advice me to go for Delphi? You think its DEMANDED nowadays? Or you just tell me an exception which only confirms the rule? It's like "one guy won 100,000,000$ in lottery. Just for you to know that lottery is not a bad way to earn money."

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• Using foldr to append two lists together (Haskell)

  - by Luke Murphy

  I have been given the following question as part of a college assignment. Due to the module being very short, we are using only a subset of Haskell, without any of the syntactic sugar or idiomatic shortcuts....I must write: append xs ys : The list formed by joining the lists xs and ys, in that order append (5:8:3:[]) (4:7:[]) => 5:8:3:4:7:[] I understand the concept of how foldr works, but I am only starting off in Functional programming. I managed to write the following working solution (hidden for the benefit of others in my class...) : However, I just can't for the life of me, explain what the hell is going on!? I wrote it by just fiddling around in the interpreter, for example, the following line : foldr (\x -> \y -> x:y) [] (2:3:4:[]) which returned [2:3:4] , which led me to try, foldr (\x -> \y -> x:y) (2:3:4:[]) (5:6:7:[]) which returned [5,6,7,2,3,4] so I worked it out from there. I came to the correct solution through guess work and a bit of luck... I am working from the following definition of foldr: foldr = \f -> \s -> \xs -> if null xs then s else f (head xs) (foldr f s (tail xs) ) Can someone baby step me through my correct solution? I can't seem to get it....I already have scoured the web, and also read a bunch of SE threads, such as How foldr works

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• REST API wrapper - class design for 'lite' object responses

  - by sasfrog

  I am writing a class library to serve as a managed .NET wrapper over a REST API. I'm very new to OOP, and this task is an ideal opportunity for me to learn some OOP concepts in a real-life situation that makes sense to me. Some of the key resources/objects that the API returns are returned with different levels of detail depending on whether the request is for a single instance, a list, or part of a "search all resources" response. This is obviously a good design for the REST API itself, so that full objects aren't returned (thus increasing the size of the response and therefore the time taken to respond) unless they're needed. So, to be clear: .../car/1234.json returns the full Car object for 1234, all its properties like colour, make, model, year, engine_size, etc. Let's call this full. .../cars.json returns a list of Car objects, but only with a subset of the properties returned by .../car/1234.json. Let's call this lite. ...search.json returns, among other things, a list of car objects, but with minimal properties (only ID, make and model). Let's call this lite-lite. I want to know what the pros and cons of each of the following possible designs are, and whether there is a better design that I haven't covered: Create a Car class that models the lite-lite properties, and then have each of the more detailed responses inherit and extend this class. Create separate CarFull, CarLite and CarLiteLite classes corresponding to each of the responses. Create a single Car class that contains (nullable?) properties for the full response, and create constructors for each of the responses which populate it to the extent possible (and maybe include a property that returns the response type from which the instance was created). I expect among other things there will be use cases for consumers of the wrapper where they will want to iterate through lists of Cars, regardless of which response type they were created from, such that the three response types can contribute to the same list. Happy to be pointed to good resources on this sort of thing, and/or even told the name of the concept I'm describing so I can better target my research.

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• Did I Inadvertently Create a Mediator in my MVC?

  - by SoulBeaver

  I'm currently working on my first biggish project. It's a frontend facebook application that has, since last Tuesday, spanned some 6000-8000 LOC. I say this because I'm using the MVC, an architecture I have never rigidly enforced in any of my hobby projects. I read part of the PureMVC book, but I didn't quite grasp the concept of the Mediator. Since I didn't understand and didn't see the need for it, my project has yet to use a single mediator. Yesterday I went back to the design board because of some requirement changes and noticed that I could move all UI elements out of the View and into its own class. The View essentially only managed the lifetime of the UI and all events from the UI or Model. Technically, the View has now become a 'Mediator' between the Model and UI. Therefore, I realized today, I could just move all my UI stuff back into the View and create a mediator class that handles all events from the view and model. Is my understanding correct in thinking that I have devolved my View as it currently is (handling events from the Model and UI) into a Mediator and that the UI class is what should be the View?

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• multi-thread in mmorpg server

  - by jean

  For MMORPG, there is a tick function to update every object's state in a map. The function was triggered by a timer in fixed interval. So each map's update can be dispatch to different thread. At other side, server handle player incoming package have its own threads also: I/O threads. Generally, the handler of the corresponding incoming package run in I/O threads. So there is a problem: thread synchronization. I have consider two methods: Synchronize with mutex. I/O thread lock a mutex before execute handler function and map thread lock same mutex before it execute map's update. Execute all handler functions in map's thread, I/O thread only queue the incoming handler and let map thread to pop the queue then call handler function. These two have a disadvantage: delay. For method 1, if the map's tick function is running, then all clients' request need to waiting the lock release. For method 2, if map's tick function is running, all clients' request need to waiting for next tick to be handle. Of course, there is another method: add lock to functions that use data which will be accessed both in I/O thread & map thread. But this is hard to maintain and easy to goes incorrect. It needs carefully check all variables whether or not accessed by both two kinds thread. My problem is: is there better way to do this? Notice that I said map is logic concept means no interactions can happen between two map except transport. I/O thread means thread in 3rd part network lib which used to handle client request.

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