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• How to evaluate a user against optimal performance?

  - by Alex K

  I have trouble coming up with a system of assigning a rating to player's performance. Well, technically there is is a trivial rating system, but I don't like it because it would mean assigning negative scores, which I think most players will be discouraged by. The problem is that I only know the ideal number of actions to get the desired result. The worst case is infinite number of actions, so there is no obvious scale. The trivial way I referred to above is to take score = (#optimal-moves - #players-moves), with ideal score being zero. However, psychologically people like big numbers. No one wants to win by getting a mark of 0. I wonder if there is a system that someone else has come up with before to solve this problem? Essentially I wish to score the players based on: How close they've come to the ideal solution. Different challenges will have different optimal number of actions, so the scoring system needs to take that into account, e.g. Challenge 1 - max 10 points, Challenge 2 - max 20 points. I don't mind giving the players negative scores if they've performed exceptionally badly, I just don't want all scores to be <=0

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• Alternatives to a leveling system

  - by Bane

  I'm currently designing a rough prototype of a mecha fighting game. These are the basics I came up with: Multiplayer (matchmaking for up to 10 people, for now) Browser based (HTML5) 2D (<canvas>) Persistent (as in, players have accounts and don't have to use a new mech each time they start a match) Players earn money upon destroying another mech, which is used to buy parts (guns, armor, boosters, etc) Simplicity (both of the game itself, and of the development of said game) No "leveling" (as in, players don't get awarded with XP) The last part is bothering me. At first, I wanted to have players gain experience points (XP) when destroying other mechs, but gaining two things at once (money and XP) seemed to be in conflict with my last point, which is simplicity. If I were to have a leveling system, that would require additional development. But, the biggest problem is that I simply couldn't fit it anywhere! Adding levels would require adding meaning to these levels, and most of the things that I hoped to achieve could already be achieved with the money mechanic I introduced. So I decided to drop leveling off completely. That, in turn, removed a fairly popular and robust mean of progression in games from my game (not that I would use it well anyway). Is there another way of progression in games, aside from leveling and XP points, that wouldn't get rendered redundant by my money mechanic, would be somehow meaningful (even on a symbolic level), and wouldn't be in conflict with my last point, which is simplicity?

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• Eculidean space and vector magnitude

  - by Starkers

  Below we have distances from the origin calculated in two different ways, giving the Euclidean distance, the Manhattan distance and the Chebyshev distance. Euclidean distance is what we use to calculate the magnitude of vectors in 2D/3D games, and that makes sense to me: Let's say we have a vector that gives us the range a spaceship with limited fuel can travel. If we calculated this with Manhattan metric, our ship could travel a distance of X if it were travelling horizontally or vertically, however the second it attempted to travel diagonally it could only tavel X/2! So like I say, Euclidean distance does make sense. However, I still don't quite get how we calculate 'real' distances from the vector's magnitude. Here are two points, purple at (2,2) and green at (3,3). We can take two points away from each other to derive a vector. Let's create a vector to describe the magnitude and direction of purple from green: |d| = purple - green |d| = (purple.x, purple.y) - (green.x, green.y) |d| = (2, 2) - (3, 3) |d| = <-1,-1> Let's derive the magnitude of the vector via Pythagoras to get a Euclidean measurement: euc_magnitude = sqrt((x*x)+(y*y)) euc_magnitude = sqrt((-1*-1)+(-1*-1)) euc_magnitude = sqrt((1)+(1)) euc_magnitude = sqrt(2) euc_magnitude = 1.41 Now, if the answer had been 1, that would make sense to me, because 1 unit (in the direction described by the vector) from the green is bang on the purple. But it's not. It's 1.41. 1.41 units is the direction described, to me at least, makes us overshoot the purple by almost half a unit: So what do we do to the magnitude to allow us to calculate real distances on our point graph? Worth noting I'm a beginner just working my way through theory. Haven't programmed a game in my life!

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• Would this be viewed poorly amongst the programming community?

  - by Eric P

  So one of my responsibilities at work is to build an internal tool that helps the workers enter in all their information. It's an enterprise application that is similar to a Windows forms database tool. So it's not much different than like developing a Word + Excel combo application, but the average person in this workgroup is a 20-40 year old woman or a random chatty male type. Plus I know all of these people are heavily involved with Facebook on a daily basis. How bad would it be if I styled my new interface to be similar to what Facebook does. People could get award points and stuff when they fill out different types of forms and basically compete against each other like it was a game. When people had completed one, it would be posted on their wall and everyone could comment/like stuff just like in Facebook. And it would be like they are doing peer reviewing for fun. The rewards would be outstanding I would imagine. These people are so into Facebook and Facebook games that productivity would rise due to them trying to compete and earn points and achievements. Would this be taking advantage of the people by 'tricking them into working harder by giving them a game' or would it be viewed as something that would improve happiness at work?

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• Is this possible?

  - by PythonNewbie2

  Hello, I'm exploring some technologies and JSP with JSF 2.0 and Primefaces seems really cool. I'm new to all of these, but I'm a fast learner. I wondering if I can create the web app I want withh JSP/JSF/Primefaces or should I be looking to different technologies? If I should, which ones do you recommend? Here's a basic description of the app: Users log in with their username and password (maybe I can somehow incorporate google OPENID)? With a really nice UI, they will be presented a large list of questions specific to a certain category, for example, JSP. When they click on any of these questions, a little input opens up below it to allow the user to put in a link. If the link they enter has the same question on that webpage the URL points to, they will be awarded one point. This question then disappears and gets added to a different page that has a list of all correctly linked questions. On the right side of the screen, there will be a leaderboard with the usernames of the people with the top ten points. Is this possible with JSP/JSF/Primefaces, or should I be looking elsewhere for a different web technology? The idea is relatively simple - to be able to compile links to external websites for specific questions. I know I can build the UI easily with Primefaces. What I'm not sure is if JSP/JSF gives the ability to parse HTML at a certain URL to see if it contains words. I can do this with python easily by using urllib. Any help would be appreciated!!! What would be more helpful than a "Yes" or "No" answer would be links to where I can see sample code of external HTML parsing. Your input is truly appreciated! Thanks!

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• Performance issues with visibility detection and object transparency

  - by maul

  I'm working on a 3d game that has a view similar to classic isometric games (diablo, etc.). One of the things I'm trying to implement is the effect of turning walls transparent when the player walks behind them. By itself this is not a huge issue, but I'm having trouble determining which walls should be transparent exactly. I can't use a circle or square mask. There are a lot of cases where the wall piece at the same (relative) position has different visibility depending on the surrounding area. With the help of a friend I came up with this algorithm: Create a grid around the player that contains a lot of "visibility points" (my game is semi tile-based so I create one point for every tile on the grid) - the size of the square's side is close to the radius where I make objects transparent. I found 6x6 to be a good value, so that's 36 visibility points total. For every visibility point on the grid, check if that point is in the player's line of sight. For every visibility point that is in the LOS, cast a ray from the camera to that point and mark all objects the ray hits as transparent. This algorithm works - not perfectly, but only requires some tuning - however this is very slow. As you can see, it requries 36 ray casts minimum, but most of the time 60-70 depending on the position. That's simply too much for the CPU. Is there a better way to do this? I'm using Unity 3D but I'm not looking for an engine-specific solution.

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• Can .htaccess slow down a site?

  - by Cody Sharp

  I'm working with a client on an e-commerce website. I implemented clean URLs using .htaccess. I also used .htaccess to solve canonical issues such as redirecting www to non-www and removing index.php from the URL. The website recently began to slow down dramatically, sometimes not even loading. The site is hosted on GoDaddy, and when the client called GoDaddy they told him it was the .htaccess file slowing down the website. I find this highly unlikely because of my past experiences, but I'm not 100% sure. My thinking is that the client's website is most likely on a shared server with a busy neighborhood, thus slowing down the site. It's not always slow, but rather sporadic throughout the day, loading fast at some points and slow at other points in time. Can the .htaccess file slow down a website to a crawl? If so, are there better ways to solve these problems with different rewrite rules and such? Here is what the actual .htaccess file looks like: Options +FollowSymlinks RewriteEngine On RewriteBase / RewriteCond %{HTTP_HOST} ^www.example.net [NC] RewriteRule ^(.*)$ http://example.net/$1 [L,R=301] RewriteRule ^products/([0-9a-zA-Z\_\-]*)\.htm([l]?)$ index.php p=product&product_code=$1 [L] RewriteRule ^catalog/([0-9a-zA-Z\_\-]*)\.htm([l]?)$ index.php p=catalog&catalog_code=$1 [L] RewriteRule ^pages/([0-9a-zA-Z\_\-]*)\.htm([l]?)$ index.php?p=page&page_id=$1 [L] RewriteRule ^index\.htm([l]?)$ index.php?p=home [L] RewriteRule ^site_map\.htm([l]?)$ index.php?p=site_map [L] RewriteCond %{QUERY_STRING} ^p=home$ RewriteRule (.*) ? [R=permanent] I'm a .htaccess and regex novice, so any pointed out mistakes would also help. Thank you.

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• LibGdx efficient data saving/loading?

  - by grimrader22

  Currently, my LibGDX game consists of a 512 x 512 map of Tiles and entities such as players and monsters. I am wondering how to efficiently save and load the data of my levels. At the moment I am using JSON serialization for each class I want to save. I implement the Json.Serializable interface for all of these classes and write only the variables that are necessary. So my map consists of 512 x 512 tiles, that's 260,000 tiles. Each tile on the map consists of a Tile object, which points to some final Tile object like a GRASS_TILE or a STONE_TILE. When I serialize each level tile, the final Tile that it points to is re-serialized over and over again, so if I have 100 Tiles all pointing to GRASS_TILE, the data of GRASS_TILE is written 100 times over. When I go to load/deserialize my objects, 100 GrassTile objects are created, but they are each their own object. They no longer point to the final tile object. I feel like this reading/writing files very slow. If I were to abandon JSON serialization, to my knowledge my next best option would be saving the level data to a sql database. Unless there is a way to speed up serializing/deserializing 260,000 tiles I may have to do this. Is this a good idea? Could I really write that many tiles to the database efficiently? To sum all this up, I am trying to save my levels using JSON serialization, but it is VERY slow. What other options do I have for saving the data of so many tiles. I also must note that the JSON serialization is not slow on a PC, it is only VERY slow on a mobile device. Since file writing/reading is so slow on mobile devices, what can I do?

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• 2D Collision masks for handling slopes

  - by JiminyCricket

  I've been looking at the example at: http://create.msdn.com/en-US/education/catalog/tutorial/collision_2d_perpixel and am trying to figure out how to adjust the sprite once a collision has been detected. As David suggested at XNA 4.0 2D sidescroller variable terrain heightmap for walking/collision, I made a few sensor points (feet, sides, bottom center, etc.) and can easily detect when these points actually collide with non-transparent portions of a second texture (simple slope). I'm having trouble with the algorithm of how I would actually adjust the sprite position based on a collision. Say I detect a collision with the slope at the sprite's right foot. How can I scan the slope texture data to find the Y position to place the sprite's foot so it is no longer inside the slope? The way it is stored as a 1D array in the example is a bit confusing, should I try to store the data as a 2D array instead? For test purposes, I'm thinking of just using the slope texture alpha itself as a primitive and easy collision mask (no grass bits or anything besides a simple non-linear slope). Then, as in the example, I find the coordinates of any collisions between the slope texture and the sprite's sensors and mark these special sensor collisions as having occurred. Finally, in the case of moving up a slope, I would scan for the first transparent pixel above (in the texture's Ys at that X) the right foot collision point and set that as the new height of the sprite. I'm a little unclear also on when I should make these adjustments. Collisions are checked on every game.update() so would I quickly change the position of the sprite before the next update is called? I also noticed several people mention that it's best to separate collision checks horizontally and vertically, why is that exactly? Open to any suggestions if this is an inefficient or inaccurate way of handling this. I wish MSDN had provided an example of something like this, I didn't know it would be so much more complex than NES Mario style pure box platforming!

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• Great Example of a Simple Cost-Benefit Analysis

  - by BuckWoody

  I saw a post the other day that you should definitely go check out. It’s a cost/benefit decision, and although the author gives it a quick treatment and doesn’t take all points in the decision into account, you should focus on the process he follows. It’s a quick and simple example of the kind of thought process we should have as data professionals when we pick a server, a process, or application and even platform software. The key is to include more than just the price of a piece of software or hardware. You need to think about the “other” costs in the decision, and then make the right one. Sometimes the cheapest option is the cheapest, and other times, well, it isn’t. I’ve seen this played out not only in the decision to go with a certain selection, but in the options or editions it comes in. You have to put all of the decision points in the analysis to come up with the right answer, and you have to be able to explain your logic to your team and your company. This is the way you become a data professional, not just a DBA. You can check out the post here – it deals with Azure, but the point is the process, not Azure itself: http://blogs.msdn.com/eugeniop/archive/2010/03/19/windows-azure-guidance-a-simplistic-economic-analysis-of-a-expense-migration.aspx Share this post: email it! | bookmark it! | digg it! | reddit! | kick it! | live it!

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• Architectural and Design Challenges with SOA

  With all of the hype about service oriented architecture (SOA) primarily through the use of web services, not much has been said about potential issues of using SOA in the design of an application. I am personally a fan of SOA, but it is not the solution for every application. Proper evaluation should be done on all requirements and use cases prior to deciding to go down the SOA road. It is important to consider how your application/service will handle the following perils as it executes. Example Challenges of SOA Network Connectivity Issues Handling Connectivity Issues Longer Processing/Transaction Times How many of us have had issues visiting our favorite web sites from time to time? The same issue will occur when using service based architecture especially if it is implemented using web services. Forcing applications to access services via a network connection introduces a lot of new failure points to the application. Potential failure points include: DNS issues, network hardware issues, remote server issues, and the lack of physical network connections. When network connectivity issues do occur, how are the service clients are implemented is very important. Should the client wait and poll the service until it is accessible again? If so what is the maximum wait time or number of attempts it should retry. Due to the fact of services being distributed across a network automatically increase the responsiveness of client applications due to the fact that processing time must now also include time to send and receive messages from called services. This could add nanoseconds to minutes per each request based on network load and server usage of the service provider. If speed highly desirable quality attribute then I would consider creating components that are hosted where the client application is located. References: Rader, Dave. (2002). Overcoming Web Services Challenges with Smart Design: http://soa.sys-con.com/node/39458

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• What causes player box/world geometry glitches in old games?

  - by Alexander

  I'm looking to understand and find the terminology for what causes - or allows - players to interfere with geometry in old games. Famously, ID's Quake3 gave birth to a whole community of people breaking the physics by jumping, sliding, getting stuck and launching themselves off points in geometry. Some months ago (though I'd be darned if I can find it again!) I saw a conference held by Bungie's Vic DeLeon and a colleague in which Vic briefly discussed the issues he ran into while attempting to wrap 'collision' objects (please correct my terminology) around environment objects so that players could appear as though they were walking on organic surfaces, while not clipping through them or appear to be walking on air at certain points, due to complexities in the modeling. My aim is to compose a case study essay for University in which I can tackle this issue in games, drawing on early exploits and how techniques have changed to address such exploits and to aid in the gameplay itself. I have 3 current day example of where exploits still exist, however specifically targeting ID Software clearly shows they've massively improved their techniques between Q3 and Q4. So in summary, with your help please, I'd like to gain a slightly better understanding of this issue as a whole (its terminology mainly) so I can use terms and ask the right questions within the right contexts. In practical application, I know what it is, I know how to do it, but I don't have the benefit of level design knowledge yet and its technical widgety knick-knack terms =) Many thanks in advance AJ

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• Which web site gives the most accurate indication of a programmer's capabilities?

  - by Jerry Coffin

  If you were hiring programmers, and could choose between one of (say) the top 100 coders on topcoder.com, or one of the top 100 on stackoverflow.com, which would you choose? At least to me, it would appear that topcoder.com gives a more objective evaluation of pure ability to solve problems and write code. At the same time, despite obvious technical capabilities, this person may lack any hint of social skills -- he may be purely a "lone coder", with little or no ability to help/work with others, may lack mentoring ability to help transfer his technical skills to others, etc. On the other hand, stackoverflow.com would at least appear to give a much better indication of peers' opinion of the coder in question, and the degree to which his presence and useful and helpful to others on the "team". At the same time, the scoring system is such that somebody who just throws up a lot of mediocre (or even poor answers) will almost inevitably accumulate a positive total of "reputation" points -- a single up-vote (perhaps just out of courtesy) will counteract the effects of no fewer than 5 down-votes, and others are discouraged (to some degree) from down-voting because they have to sacrifice their own reputation points to do so. At the same time, somebody who makes little or no technical contribution seems unlikely to accumulate a reputation that lands them (even close to) the top of the heap, so to speak. So, which provides a more useful indication of the degree to which this particular coder is likely to be useful to your organization? If you could choose between them, which set of coders would you rather have working on your team?

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• Cleaning Up Online Games with Positive Enforcement

  - by Jason Fitzpatrick

  Anyone who has played online multiplayer games, especially those focused on combat, can attest to how caustic other players can be. League of Legends creators are fighting that, rather successfully, with a positive-reinforcement honor system. The Mary Sue reports: Here’s the background: Six months ago, Riot established Team Player Behavior — affectionately called Team PB&J — a group of experts in psychology, neuroscience, and statistics (already, I am impressed). At the helm is Jeffrey Lin, better known as Dr. Lyte, Riot’s lead designer of social systems. As quoted in a recent article at Polygon: We want to show other companies and other games that it is possible to tackle player behavior, and with certain systems and game design tools, we can shape players to be more positive. Which brings us to the Honor system. Honor is a way for players to reward each other for good behavior. This is divvied up into four categories: Friendly, Helpful, Teamwork, and Honorable Opponent. At the end of a match, players can hand out points to those they deem worthy. These points are reflected on players’ profiles, but do not result in any in-game bonuses or rewards (though this may change in the future). All Honor does is show that you played nicely. 6 Ways Windows 8 Is More Secure Than Windows 7 HTG Explains: Why It’s Good That Your Computer’s RAM Is Full 10 Awesome Improvements For Desktop Users in Windows 8

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• backface culling error (in world space)

  - by acrilige

  I write simple software renderer. In my pipeline i have stage of backface culling. But looks like it has some error (see picture). I perform culling right after world transformation (is it correct?). (i can't insert picture in post coz i don't have enough points, so i just upload it (cube model): http://imageshack.us/photo/my-images/705/bcerror.png/) Vector3F view_dir(0.0f, 0.0f, 1.0f); std::vector<Triangle> to_remove; for (Triangle &t : m_triangles) { Vector4F e1 = t.v2 - t.v1; Vector4F e2 = t.v3 - t.v1; Vector3F normal( e1.y * e2.z - e1.z * e2.y, e1.z * e2.x - e1.x * e2.z, e1.x * e2.y - e1.y * e2.x ); normal.Normalize(); float dot = Dot(view_dir, normal); if (dot <= 0) to_remove.push_back(t); } for (Triangle& t : to_remove) m_triangles.erase(std::remove(m_triangles.begin(), m_triangles.end(), t), m_triangles.end()); Camera sits in origin and points in screen (RH). What is the reason? For better explanation i upload picture with cube rotation screenshots: http://imageshack.us/photo/my-images/842/bcmove.png/ UPDATED: The error occurs only when triangle has non-zero offset from origin UPDATED 2: If i process backface culling in clip space (after transforming all vertices with view and projection matrix), and just check z coordinate of triangle normal - it works perfect... Can i perform culing RIGHT BEFORE view/proj transforms? In this case looks like culling will not depends of projection and it's not right?.. UPDATED 3: I found answer and will post it in two hours - again coz of reputation lack.

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• Using 12.04 installation as a persistent pen drive

  - by Cawas

  Disclaimer: I aim to build a self contained pen drive with my application inside, so no matter about updates. Maybe I'm looking at the wrong linux distribution to do this... Please let me know if you think so. I've tried knoppix and even lubuntu, but they don't come with enough "drivers" for Unity3D to work. Creating a custom live persistent pen drive is a real pain and I'm trying for 1 day without any success. Sure, being able to do it would probably be ideal and occupy the minimum space. Using the installation image on a pen drive, however, is good enough and is really easy to create. We can even do it from any OS, using UNetBootin, LiLi USB Creator or some other methods. Straight forward. Some recommend installing it on a pen drive. But that requires a lot of space and, I believe, it won't behave as good as something meant to be installed on a usb disk, because of memory management. So, there are only a few negative points on using the installation image that I can think of. Question here, is how to remove those drawbacks: Having to press "Try Ubuntu". That's the big one. Couldn't find how. Unable to load everything on memory and keep on running without the pen drive (like this) Unable to remove "Install Ubuntu 12.04 LTS" app. Setting the ISO to use maximum amount of space for the OS will leave pen drive with zero space left and any file saved within it from ubuntu is inaccessible from the outside (when plugin the pen drive and not booting from it). Am I missing something? Can those points be fixed?

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• Location of development solutions on disk - Common or upto the individual

  - by dreza

  In our team meeting today a senior member brought up the proposal that we should be having a common location/structure for our development solutions. A couple of his points were: Making it common meant when talking about projects and emailing stuff everyone is on the same wavelength and knows where to look. If there is ever the need to hard code a location path then it will work across all developers pc's. He had a more few points to back up his suggestion but I unfortunately got distracted during the discussion and so didn't hear all of them. I have no issue with the idea and can see it's merits but I was wondering if it is common or even recommended that all developers place their code in the same folder structure. Or do developers like to have the flexibility of location solutions where-ever they want? We currently use SVN for our version control. In this case his recommendation was to place all code in: c:\Work\Development\<Customer>\<project>\Code\<solution>\ the code I guess actual path is irrelevant for this question but added for completeness.

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• backface culling error

  - by acrilige

  I write simple software renderer. In my pipeline i have stage of backface culling. But looks like it has some error (see picture). I perform culling right after world transformation. (i can't insert picture in post coz i don't have enough points, so i just upload it (cube model): http://imageshack.us/photo/my-images/705/bcerror.png/) Vector3F view_dir(0.0f, 0.0f, 1.0f); std::vector<Triangle> to_remove; for (Triangle &t : m_triangles) { Vector4F e1 = t.v2 - t.v1; Vector4F e2 = t.v3 - t.v1; Vector3F normal( e1.y * e2.z - e1.z * e2.y, e1.z * e2.x - e1.x * e2.z, e1.x * e2.y - e1.y * e2.x ); normal.Normalize(); float dot = Dot(view_dir, normal); if (dot <= 0) to_remove.push_back(t); } for (Triangle& t : to_remove) m_triangles.erase(std::remove(m_triangles.begin(), m_triangles.end(), t), m_triangles.end()); Camera sits in origin and points in screen (RH). What is the reason?

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• Draw contour around object in Opengl

  - by Maciekp

  I need to draw contour around 2d objects in 3d space. I tried drawing lines around object(+points to fill the gap), but due to line width, some part of it(~50%) was covering object. I tried to use stencil buffer, to eliminate this problem, but I got sth like this(contour is green): http://goo.gl/OI5uc (sorry I can't post images, due to my reputation) You can see(where arrow points), that some parts of line are behind object, and some are above. This changes when I move camera, but always there is some part, that is covering it. Here is code, that I use for drawing object: glColorMask(1,1,1,1); std::list<CObjectOnScene*>::iterator objIter=ptr->objects.begin(),objEnd=ptr->objects.end(); int countStencilBit=1; while(objIter!=objEnd) { glColorMask(1,1,1,1); glStencilFunc(GL_ALWAYS,countStencilBit,countStencilBit); glStencilOp(GL_REPLACE,GL_KEEP,GL_REPLACE ); (*objIter)->DrawYourVertices(); glStencilFunc(GL_NOTEQUAL,countStencilBit,countStencilBit); glStencilOp(GL_KEEP,GL_KEEP,GL_REPLACE); (*objIter)->DrawYourBorder(); ++objIter; ++countStencilBit; } I've tried different settings of stencil buffer, but always I was getting sth like that. Here is question: 1.Am I setting stencil buffer wrong? 2. Are there any other simple ways to create contour on such objects? Thanks in advance.

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• How can I properly create /dev/dvd?

  - by chazomaticus

  Certain programs look for /dev/dvd by default to find DVDs. When I first boot my computer without a DVD inserted, /dev/dvd exists and points to the correct place (/dev/sr0). However, when I insert a DVD, /dev/dvd disappears. I'd like it to stick around so I don't have to navigate to /dev/sr0 in programs that are looking for DVDs. How do I ensure that the /dev/dvd symlink exists and points to the right place? It looks like I can add something to /etc/udev/rules.d/70-persistent-cd.rules. This site gives a couple of examples, but the 70-persistent-cd.rules file says "add the ENV{GENERATED}=1 flag to your own rules", which isn't part of the examples. The man 7 udev page is impenetrable to me, and I'm not convinced the linked page gives 100% of the information I need. So, what can I do on a modern, Ubuntu 12.04 (or later) system to make /dev/dvd always exist and point to the right device? EDIT: Is it as simple as adding ENV{GENERATED}=1 to the rules in the linked page, something like this: SUBSYSTEM=="block", KERNEL=="sr0", SYMLINK+="dvd", GROUP="cdrom", ENV{GENERATED}=1 Is that the right information for modern Ubuntu? What is ENV{GENERATED} doing there, when it wasn't generated, but hand-written?

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• Hosting and scaling of a facebook application on cloud?

  - by DhruvPathak

  We would be building a facebook application in django(Python), but still not sure of where to host it economically,and with a good provision to scale in case the app gets viral. Some details about the app: i) Would be HTML based like a website,using django as a framework. ii) 100K is the number of expected pageviews in a day,if the app is viral. iii) The users will not generate any media content,only some database data will be generated by them. It would be great if someone with more experience can guide on following points: A) Hosting on google app engine or Amazon EC2 or some other cloud like RackSpace : Preferable points found in AppEngine were ease of deployment,cost effectiveness and easy scaling. For EC2: Full hold of the virtual machine,Amazon NoSQL and RDMBS database services in case we decide to use them. B) Does backend technology affect monthly cost ? eg. would CPU and memory usage difference of Django over , for example , PHP framework like CodeIgnitor really make remarkable difference in running costs. ( Here is the article that triggered this thought process : http://journal.dedasys.com/2010/01/12/rough-estimates-of-the-dollar-cost-of-scaling-web-platforms-part-i#comments) C) Does something like Heroku , which provides additional services over Amazon EC2, prove to be better than raw cloud management ? It is not that we are trying for premature scaling, we just want to have a good start so that we are ready to handle unpredicted growth and scale.

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• Name of the Countdown Numbers round problem - and algorithmic solutions?

  - by Dai

  For the non-Brits in the audience, there's a segment of a daytime game-show where contestants have a set of 6 numbers and a randomly generated target number. They have to reach the target number using any (but not necessarily all) of the 6 numbers using only arithmetic operators. All calculations must result in positive integers. An example: Youtube: Countdown - The Most Extraordinary Numbers Game Ever? A detailed description is given on Wikipedia: Countdown (Game Show) For example: The contentant selects 6 numbers - two large (possibilities include 25, 50, 75, 100) and four small (numbers 1 .. 10, each included twice in the pool). The numbers picked are 75, 50, 2, 3, 8, 7 are given with a target number of 812. One attempt is (75 + 50 - 8) * 7 - (3 * 2) = 813 (This scores 7 points for a solution within 5 of the target) An exact answer would be (50 + 8) * 7 * 2 = 812 (This would have scored 10 points exactly matching the target). Obviously this problem has existed before the advent of TV, but the Wikipedia article doesn't give it a name. I've also saw this game at a primary school I attended where the game was called "Crypto" as an inter-class competition - but searching for it now reveals nothing. I took part in it a few times and my dad wrote an Excel spreadsheet that attempted to brute-force the problem, I don't remember how it worked (only that it didn't work, what with Excel's 65535 row limit), but surely there must be an algorithmic solution for the problem. Maybe there's a solution that works the way human cognition does (e.g. in-parallel to find numbers 'close enough', then taking candidates and performing 'smaller' operations).

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• Java - Using Linear Coordinates to Check Against AI [closed]

  - by Oliver Jones

  I'm working on some artificial intelligence, and I want my AI not to run into given coordinates as these are references of a wall/boundary. To begin with, every time my AI hits a wall, it makes a reference to that position (x,y). When it hits the same wall three times, it uses linear check points to 'imagine' there is a wall going through these coordinates. I want to now prevent my AI from going into that wall again. To detect if my coordinates make a straight line, i use: private boolean collinear(double x1, double y1, double x2, double y2, double x3, double y3) { return (y1 - y2) * (x1 - x3) == (y1 - y3) * (x1 - x2); } This returns true is the given points are linear to one another. So my problems are: How do I determine whether my robot is approaching the wall from its current trajectory? Instead of Java 'imagining' theres a line from 1, to 3. But to 'imagine' a line all the way through these linear coordinantes, until infinity (or close). I have a feeling this is going to require some confusing trigonometry? (REPOST: http://stackoverflow.com/questions/13542592/java-using-linear-coordinates-to-check-against-ai)

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• Draw contour around object in Opengl

  - by Maciekp

  I need to draw contour around 2d objects in 3d space. I tried drawing lines around object(+points to fill the gap), but due to line width, some part of it(~50%) was covering object. I tried to use stencil buffer, to eliminate this problem, but I got sth like this(contour is green): http://goo.gl/OI5uc (sorry I can't post images, due to my reputation) You can see(where arrow points), that some parts of line are behind object, and some are above. This changes when I move camera, but always there is some part, that is covering it. Here is code, that I use for drawing object: glColorMask(1,1,1,1); std::list<CObjectOnScene*>::iterator objIter=ptr->objects.begin(),objEnd=ptr->objects.end(); int countStencilBit=1; while(objIter!=objEnd) { glColorMask(1,1,1,1); glStencilFunc(GL_ALWAYS,countStencilBit,countStencilBit); glStencilOp(GL_REPLACE,GL_KEEP,GL_REPLACE ); (*objIter)->DrawYourVertices(); glStencilFunc(GL_NOTEQUAL,countStencilBit,countStencilBit); glStencilOp(GL_KEEP,GL_KEEP,GL_REPLACE); (*objIter)->DrawYourBorder(); ++objIter; ++countStencilBit; } I've tried different settings of stencil buffer, but always I was getting sth like that. Here is question: 1.Am I setting stencil buffer wrong? 2. Are there any other simple ways to create contour on such objects? Thanks in advance. EDIT: 1. I don't have normals of objects. 2. Object can be concave. 3. I can't use shaders(see below why).

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• CSOM (Client Side Object Model) - What's new with SharePoint 2013

  - by KunaalKapoor

  SharePoint CSOMThe Client-Side Object Model or CSOM came out with SharePoint 2010. CSOM is accessible through client.svc but all client.svc calls must go through supported WFC entry points (supported entry points are .NET, Silverlight and JavaScript). So a developer would need to use client side proxy objects exposed by either a .NET assembly or a JavaScript library. Changes with SharePoint 2013REST Capabilities - Direct access to client.svcNew APIs - App ModelREST CapabilitiesOne of the most important changes to the CSOM with SharePoint 2013 is that the web service entry point of client.svc has been extended to allow direct access  via REST-Based web service calls. This is a really critical change since its going to make the SharePoint platform accessible to any other platform, opening the horizons of integration and collaboration with other REST based platforms and devices. OData (a really popular standard data access API for HTTP-based clients) is supported similar to 2010 but will be a more important aspect of SharePoint 2013 development.New API'sCSOM for SharePoint 2013 has been buffed up with several new APIs for not only SharePoint server functionality but also an API for Windows Phone applications. For a SharePoint 2010 farm most of the new APIs mentioned below are available only via server side APIs:SearchTaxonomyPublishingWorkflowUser ProfilesE-DiscoveryAnalyticsBusiness DataIRMFeedsSharePoint 2013 remote APIs being accessible through both CSOM and REST is very important to the new app model where developers can no longer run code in a SharePoint environment nor can they access the server-side APIs. So CSOM plays the savior here.Also, you can now substitute the alias '_api' in order to reference '_vti_bin/client.svc'.

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