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  • JNDI Datasource Problem on Tomcat 6, Hibernate

    - by Asuman AKYILDIZ
    I am using Tomcat 6 as application server, Struts-Hibernate and MyEclipse 6.0. My application uses JDBC driver but I should modify it to use JNDI Datasource. I followed steps as described in tomcat 6.0 howto tutorial. I defined my resource in tomcatconf: <Resource name="jdbc/ats" global="jdbc/ats" auth="Container" type="javax.sql.DataSource" driverClassName="oracle.jdbc.OracleDriver" url="jdbc:oracle:thin:@//localhost:1521/MISDEV" username="TEST" password="TEST" maxActive="20" maxIdle="10" maxWait="-1" validationQuery="SELECT 1 from dual" removeAbandoned="true" removeAbandonedTimeout="30" logAbandoned="false"/> I gave reference in my application web.xml: <resource-ref> <description>Oracle Datasource example</description> <res-ref-name>jdbc/ats</res-ref-name> <res-type>javax.sql.DataSource</res-type> <res-auth>Container</res-auth> </resource-ref> And I defined datasource-dialect in my hibernate-cfg.xml <property name="connection.datasource">java:comp/env/jdbc/ats</property> <property name="dialect">org.hibernate.dialect.Oracle9Dialect</property> But when I create hibernate session, it can not open the connection: 09:18:11,322 ERROR JDBCExceptionReporter:72 - Connections could not be acquired from the underlying database! org.hibernate.exception.GenericJDBCException: Cannot open connection I also tried to set the properties at runtime: Configuration configuration = new Configuration(); configuration.setProperty("hibernate.dialect", "org.hibernate.dialect.Oracle9Dialect"); //configuration.setProperty("hibernate.connection.datasource", "java:comp/env/jdbc/ats"); configuration.setProperty("hibernate.current_session_context_class", "thread"); configuration.setProperty("hibernate.connection.provider_class", "org.hibernate.connection.C3P0ConnectionProvider"); configuration.setProperty("hibernate.show_sql", "true"); sessionFactory = configuration.configure().buildSessionFactory(); It does not open connection again. But, when I use JDBC driver it works: Configuration configuration = new Configuration(); configuration.setProperty("hibernate.dialect", "org.hibernate.dialect.Oracle9Dialect"); //configuration.setProperty("hibernate.connection.datasource", "java:comp/env/jdbc/ats"); configuration.setProperty("hibernate.connection.url", "jdbc:oracle:thin:@//localhost:1521/MISDEV"); configuration.setProperty("hibernate.connection.username", "test"); configuration.setProperty("hibernate.connection.password", "test"); configuration.setProperty("hibernate.connection.driver_class", "oracle.jdbc.OracleDriver"); configuration.setProperty("hibernate.transaction.factory_class", "org.hibernate.transaction.JDBCTransactionFactory"); configuration.setProperty("hibernate.current_session_context_class", "thread"); configuration.setProperty("hibernate.connection.provider_class", "org.hibernate.connection.C3P0ConnectionProvider"); configuration.setProperty("hibernate.show_sql", "true"); sessionFactory = configuration.configure().buildSessionFactory(); I have been searching for 3 days and no success. What may be de problem?

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  • top does not run

    - by Horace Ho
    Sorry that I can't be very specific, only symtoms are provided: Monday morning a CentOS box, 1GB ram, Pentium 4 web server (thin, rails) does not response (too slow) to a browser of another PC ping it, ok ssh into it, ok a few minutes later, the web server is back to normal speed, serving web requests well ping it, ok ssh into it, ok however, top does not run what should I look at, about this 'top does not run' symptom? thx

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  • open source VDI solution [closed]

    - by sysconfig
    looking to build a 10 node to eventually 50 node VDI solution. the only OS on the desktop will be ubuntu ( or some other linux ) looking for easy setup administration, and remote administration etc. will probably just use diskless PC as clients for now, but would want a solution that can accommodate thin-clients as well, and maybe there its just XDMCP from the server. must be completely open source ( no VMware ) thoughts ?

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  • RDP 6.1.7600 Bug

    - by Jacob
    I've noticed a bug with RDP 6.1.7600. When I try to remote control another user on our Windows Server 2003 machine, I get an error that says "because of a protocol error, this session will be disconnected" and my RDP session is logged out. The error only happens when I try to control a Neoware Thin Clients. Is it because the RDP protocol versions are different?

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  • JNDI Datasource Problem on Tomcat 6, Hibernate

    - by Asuman AKYILDIZ
    Hello; I am using Tomcat 6 as application server, Struts-Hibernate and MyEclipse 6.0. My application uses JDBC driver but I should modify it to use JNDI Datasource. I followed steps as described in tomcat 6.0 howto tutorial. I defined my resource in tomcatconf: <Resource name="jdbc/ats" global="jdbc/ats" auth="Container" type="javax.sql.DataSource" driverClassName="oracle.jdbc.OracleDriver" url="jdbc:oracle:thin:@//localhost:1521/MISDEV" username="TEST" password="TEST" maxActive="20" maxIdle="10" maxWait="-1" validationQuery="SELECT 1 from dual" removeAbandoned="true" removeAbandonedTimeout="30" logAbandoned="false"/> I gave reference in my application web.xml: <resource-ref> <description>Oracle Datasource example</description> <res-ref-name>jdbc/ats</res-ref-name> <res-type>javax.sql.DataSource</res-type> <res-auth>Container</res-auth> </resource-ref> And I defined datasource-dialect in my hibernate-cfg.xml <property name="connection.datasource">java:comp/env/jdbc/ats</property> <property name="dialect">org.hibernate.dialect.Oracle9Dialect</property> But when I create hibernate session, it can not open the connection: 09:18:11,322 ERROR JDBCExceptionReporter:72 - Connections could not be acquired from the underlying database! org.hibernate.exception.GenericJDBCException: Cannot open connection I also tried to set the properties at runtime: Configuration configuration = new Configuration(); configuration.setProperty("hibernate.dialect", "org.hibernate.dialect.Oracle9Dialect"); //configuration.setProperty("hibernate.connection.datasource", "java:comp/env/jdbc/ats"); configuration.setProperty("hibernate.current_session_context_class", "thread"); configuration.setProperty("hibernate.connection.provider_class", "org.hibernate.connection.C3P0ConnectionProvider"); configuration.setProperty("hibernate.show_sql", "true"); sessionFactory = configuration.configure().buildSessionFactory(); It does not open connection again. But, when I use JDBC driver it works: Configuration configuration = new Configuration(); configuration.setProperty("hibernate.dialect", "org.hibernate.dialect.Oracle9Dialect"); //configuration.setProperty("hibernate.connection.datasource", "java:comp/env/jdbc/ats"); configuration.setProperty("hibernate.connection.url", "jdbc:oracle:thin:@//localhost:1521/MISDEV"); configuration.setProperty("hibernate.connection.username", "test"); configuration.setProperty("hibernate.connection.password", "test"); configuration.setProperty("hibernate.connection.driver_class", "oracle.jdbc.OracleDriver"); configuration.setProperty("hibernate.transaction.factory_class", "org.hibernate.transaction.JDBCTransactionFactory"); configuration.setProperty("hibernate.current_session_context_class", "thread"); configuration.setProperty("hibernate.connection.provider_class", "org.hibernate.connection.C3P0ConnectionProvider"); configuration.setProperty("hibernate.show_sql", "true"); sessionFactory = configuration.configure().buildSessionFactory(); I have been searching for 3 days and no success. What may be de problem?

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  • Problems connecting Clariion LUNS to Solaris 10

    - by vialde
    I've got a Clariion San and a Solaris 10 server with an emulex HBA. The Thin LUNS are visible in Solaris and I can happily format the raw devices. Unfortunately that's all I can do. All other operations result in I/O errors. I'm running current versions of PowerPath and Solaris is patched as high as it'll go. Anyone have any similar experiences?

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  • Can I choose a sparse file as vdev for a zfs pool?

    - by Karl Richter
    man zpool states that a vdev for a zfs pool can be a "regular file". Can I specify a sparse file (the warning about the integrity of the file being determined by the underlying filesystem should apply with the same relevance for a sparse file)? The ZFS administration guide on https://pthree.org/2012/12/04/zfs-administration-part-i-vdevs/ states that file vdevs "must be preallocated, and not sparse files or thin provisioned" (thanks to @jlliagre). On https://wiki.archlinux.org/index.php/Experimenting_with_ZFS sparse files are used without any comment.

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  • Customizing fast-access buttons on left-hand side of File->Open dialogue in most Windows programs

    - by Randolf Richardson
    In many Windows programs when I open a file, the GUI dialogue that starts with "Look in:" and provides a list of directories and files to open has a thin panel on the left-hand side with the following 5 icons: Recent Places Desktop Libraries Computer Network Is there a Registry Hack available for adding my own icons to this? I wish to add three for various folders related to the work that I do, and I haven't been able to find a way to customize this. Thanks in advance.

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  • How to get back to an active minibuffer prompt in emacs without the mouse

    - by Ryan Thompson
    In emacs, sometimes I will be in the middle of finding a file or switching buffers or doing something in the minibuffer, and I will click somewhere else for some reason. When I go back, the only way to make the minibuffer prompt active again is to click inside the minibuffer, which is annoying because it is a thin area. Is there any way to switch back to an active minibuffer prompt without using the mouse?

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  • Get Used rather than Provisioned space in PowerCLI

    - by Matt
    I'm trying to run a capacity report, and when I run the Get-HardDisk cmdlet in PowerCLI, the value it returns for CapacityKB is the Provisioned space. For example, let's say I've thin provisioned a 200GB disk, which is currently using say 30GB, it returns the 200GB value. Is there any way I can get the other value? I need to know how much disk space is actually being used on the LUN by the vmdk file. My PowerCLI version is 5.0.1.

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  • anti-static foam under a motherboard?

    - by user29734
    I am modding out a custom built case/system. I have my motherboard mounted on a metal tray, (Dell did this) has been working great. Not I am modding the case to hold everything and how I want to mount the motherboard on the tray I have a slight gap between the wall of the case and the motherboard/tray. Can I put a piece of thin anti-static foam/packaging in between the tray and the case? That is safe right?

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  • Tool for mass adding properties to many xml files?

    - by user22902
    I have some xml that looks like this in each report: Header Cell /Cell Cell /Cell ... /Header In each cell I need to add: <property name="borderBottomColor">#E1E1E1</property> <property name="borderBottomStyle">solid</property> <property name="borderBottomWidth">thin</property> This will take me about a week to do manually. Is there a tool that could do this? Thanks

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  • Is it possible to scan Entities in jar files using JPA and hibernate

    - by user1260109
    I have the following situation : Project A - Contains a few entities and is independent Project B - Contains a few entities and is independent Project C - Contains few entities and is dependent on Project A & Project B. I am using Maven to manage dependencies and builds. When I try to test Project A and project B it goes through fine. Each of them has a persistence.xml and a separate persistent context. When I run Project C , It does map any of the entities. I have tried to use the auto-detect, specified the jar file attribute ... but nothing seems to work. It gives me a Mapping Exception saying unknown entity and wont persist or read the Entities from Projects A or B. I have posted the 3 persistence.xml files here. Also, I tried using the class attribute and using the same persistent context but it just wont find the files. Any help is really appreciated. Thanks in advance ! <persistence xmlns="http://java.sun.com/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_1_0.xsd" version="1.0"> <persistence-unit name="A" transaction-type="RESOURCE_LOCAL"> <provider>org.hibernate.ejb.HibernatePersistence</provider> <properties> <property name="hibernate.dialect" value="org.hibernate.dialect.Oracle9Dialect"/> <property name="hibernate.connection.driver_class" value="oracle.jdbc.OracleDriver"/> <property name="hibernate.show_sql" value="true"/> <property name="hibernate.connection.username" value="username"/> <property name="hibernate.connection.password" value="password"/> <property name="hibernate.connection.url" value="jdbc:oracle:thin:@webdev.epi.web:1521/webdev.world"/> <property name="hibernate.max_fetch_depth" value="3"/> <property name="hibernate.archive.autodetection" value="class"/> </properties> </persistence-unit> </persistence> <persistence xmlns="http://java.sun.com/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_1_0.xsd" version="1.0"> <persistence-unit name="B" transaction-type="RESOURCE_LOCAL"> <provider>org.hibernate.ejb.HibernatePersistence</provider> <properties> <property name="hibernate.dialect" value="org.hibernate.dialect.Oracle9Dialect"/> <property name="hibernate.connection.driver_class" value="oracle.jdbc.OracleDriver"/> <property name="hibernate.show_sql" value="true"/> <property name="hibernate.connection.username" value="username"/> <property name="hibernate.connection.password" value="password"/> <property name="hibernate.connection.url" value="jdbc:oracle:thin:@webdev.epi.web:1521/webdev.world"/> <property name="hibernate.max_fetch_depth" value="3"/> <property name="hibernate.archive.autodetection" value="class"/> </properties> </persistence-unit> </persistence> <persistence xmlns="http://java.sun.com/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_1_0.xsd" version="1.0"> <persistence-unit name="C" transaction-type="RESOURCE_LOCAL"> <provider>org.hibernate.ejb.HibernatePersistence</provider> <jar-file>A-0.0.1-SNAPSHOT.jar</jar-file> <jar-file>B-0.0.1-SNAPSHOT.jar</jar-file> <properties> <property name="hibernate.dialect" value="org.hibernate.dialect.Oracle9Dialect"/> <property name="hibernate.connection.driver_class" value="oracle.jdbc.OracleDriver"/> <property name="hibernate.show_sql" value="true"/> <property name="hibernate.connection.username" value="username"/> <property name="hibernate.connection.password" value="password"/> <property name="hibernate.connection.url" value="jdbc:oracle:thin:@webdev.epi.web:1521/webdev.world"/> <property name="hibernate.max_fetch_depth" value="3"/> <property name="hibernate.archive.autodetection" value="class"/> </properties> </persistence-unit> </persistence>

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  • Gigabit and Full-Duplex

    - by jchang
    People still talk about checking if the network is in full-duplex mode even when they are on Gigabit Ethernet. Let me say clearly: Gigabit Ethernet is full-duplex period. There is no half-duplex mode. The same goes for 10 Gigabit Ethernet. If Windows Task Manager says the network Link Speed is 1 or 10 Gbps, don’t bother checking the mode, it can only be full-duplex. In the old days of 10Mbit/sec Ethernet was originally half-duplex. The old 10BASE5 (fat) and 10BASE2 (thin) cable had one signal carrier....(read more)

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  • Sed problem in a Bash script

    - by moata_u
    Hello there. I'm having a problem using the sed command . I'm trying to write a bash script that does the following : search for the line that contain :@ then save the line that contained :@ and replace it with new line as in the following: #! /bin/bash echo "Please enter the ip address of you file"<br> read ipnumber<br> find=`grep ':@' application.properties` # find the line<br> input="connection.url=jdbc\racle\:thin\:@$ipnumber\:1521\:billz" # preparing new line<br> echo `sed "s/'${find}'/'${input}'/g" application.properties` # replace old with new line <br> The problem is: nothing happens. I've already tried to use "${find}" instead of '${find}'

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  • How do I draw a border around a display object in Corona Lua?

    - by Greg
    What would be the easiest way to draw a thin border around a display object in Corona Lua? You could assume it's rectangular image display object. EDIT - re "this question shows no research effort. You should tell us what you've tried and how it didn't work" Reviewed API and could not find a "border" method/property on displayObject Have tried creating a black box slightly bigger behind object, however can not see how to place object behind an existing object hence question How do I move an existing display object behind another in Corona Lua? Google results for putting a border around a display object in corona didn't help

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  • "/etc/init.d/networking restart" with non-root user

    - by bonchen
    I have a thin client with 112mb RAM which boots ubuntu server 12.04.1 from a usb drive with openbox and it is to be used by students to communicate with cisco equipment. And because of this the students need to be able to reconfigure the network interface and then restart it without a reboot using the only user - cisco. This is what I have so far: adduser cisco usermod -a -G dialout cisco chown root:cisco /etc/network/interfaces chmod 664 /etc/network/interfaces chmod u+s /sbin/shutdown chmod u+s /sbin/reboot chmod u+s /sbin/poweroff chmod u+s /run/network/if* chmod u+s /sbin/ifdown chmod u+s /sbin/ifup And when I run /etc/init.d/networking restart as cisco I get: *Reconfiguring network interfaces... rm: cannot remove `eth0.dhclient': Permission denied Failed to send flush request: Operation not permitted RTNETLINK answers: Operation not permitted Any ideas on how to get this working? Thanks!

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  • Anyone know how to get an LTSP image working with VIA VX855 chipset?

    - by Bryan
    I'm running an LTSP server on Ubuntu 11.10 and can load the i386 image via PXE boot on a VirtualBox VM just fine. However, when I PXE boot a Dell FX130 thin client on the LTSP network the login screen ends up being a white screen with a bunch of wavy black lines going up and down it. The 11.10 splash screen displays just fine as the image is booted, then I get a "INVALID CARD NUMBER" message, then a black screen, then finally the white screen with wavy lines. I'm not sure if the "INVALID CARD NUMBER" message has anything to do with the issue, but in the end the white screen with wavy lines makes me think it's a video driver problem. On the LTSP server, I chrooted into /opt/ltsp/i386 and made sure xserver-xorg-video-openchrome was installed. I did notice that no xorg.conf exits in /etc/X11 though.

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  • 3D rotation tool. How can I add simple extrusion?

    - by Gerve
    The 3D rotation tool is excellent but it only lets you rotate 2D objects, this means my object is wafer thin. Is there any way to add simple extrusion or depth to a symbol? I don't really want to use any 3rd party libraries like Away3D or Papervision, this is overkill for my simple 2D game. I only want to do this creating a couple motion tweens if possible. More Details: Below is what my symbol looks like (just with a bit more color). The symbol does a little 3D rotation and then flies away, it's just for something like a scoreboard within the app.

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  • Graffiti is a Sinatra-inspired Groovy Framework

    - by kerry
    Playing around with Sinatra the other day and realized I could really use something like this for Groovy. Thus, Graffiti was born. It’s basically a thin wrapper around Jetty. At first, I thought I might write my own server for it (everybody needs to do that once, don’t they?), but decided to invoke the ’simplest thing that could possibly work’ principle. Here is the requisite ‘Hello World’ example: import graffiti.* @Grab('com.goodercode:graffiti:1.0-SNAPSHOT') @Get('/helloworld') def hello() { 'Hello World' } Graffiti.serve this The code, plus more documentation is hosted under my github account.

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  • Windows Phone 7 Review &ndash; Part 1: LG Quantum

    - by Nikita Polyakov
    As many of my fellow geeks, I ran out and got a retail windows Phone 7 on the first day. Just had to have it :) I’ve had the developer prototypes in my hands for previous 3 months on and off, so I finally wanted to have one I call my own. I’ve rushed the Launch   I’ve checked out both AT&T and T-Mobile offerings on day 1 and decided on a Samsung Focus. Great screen, super light and thin. If you don’t believe me that this phone can compete with the best of the non-Phone 7 offerings - get it in your hand to compare for yourself. I have to say that even though the on-screen keyboard on Windows Phone 7 is one of the best, the amount of text I write on my phone and my expectation of how long that takes for a short reply are very high. Also the phone being so slick and sexy did not feel solid or confident in my hand or pocket. As the dust settled   Arrives the LG Quantum – now on AT&T and worldwide. First impression of the softer plastic, the back battery cover is solid metal - the entire phone feels solid and indestructible! Phone fits just right in my hand, it’s almost too good. It does not feel like it will crack in your jeans. I feel safe holding it and don’t feel like if I or someone were to bump into me walking it’d fly out of my hand. I’ve dropped and had thrown the Focus a few times on accident as it’s weight is negligible. I won’t even dream of lying the first day adjusting to a 3.5’ LCD screen from the Samsung’s blistering bright and poppy AMOLED 4’ was hard. But the colors and sharpness are still very good. I find it almost easier on the eyes actually for day to day use.  I had a chance to lay the phone down in the line with the prototypes and final versions of other phones that had LCD screens – LG makes HTC looks like a budget LCD compared to a high end LCD in the home theatre department. I am consistently complemented by friends that have the HD7 or Surround on how much better my screen looks. The screen just looks like the most color correct phone out of the line up. Even next to Samsung it makes it look oversaturated, but can’t match the true blacks compensating with true white.   Day to Day Usability   What I also noticed that is a huge difference is how much I am not accidently hitting the soft keys at the bottom. I real pain on Focus since holding it in am average size hand already would accidently touch the controls at the bottom. QWERTY keyboard on this phone is great. It’s like the mission for LG is “make it solid!”. Keyboard has a very durable feel.   LG’s has a secret wild card though is the DLNA support. If you seen an ad for it, you should. Imagine this – playing a song from your phone straight to your network connected A/V receiver. Done. Pictures to TV. Done. Video. Done. DLNA works with components that advertise to as well as Windows 7, XBOX 360 and other consoles.  I will write an extensive review of that experience in near future. LG Exclusive apps – from panorama photo taker to voice to text translator and even look-n-type app that works like a backup inverse camera, there is quite a bit there that won’t be found on the other phones. I’ll review those in more detail in another segment. Conclusion So for a quick comparison: If you want a phone that is super thin, light and is core reference of a Windows Phone 7 – Samsung Focus it is. If you want a great phone with solid secure feel, real keyboard, media features - the hands down winner is LG Quantum.   You can pick up the LG Quantum at AT&T in US and worldwide as LG Optimus 7Q.   Final thought: I have not had SmartPhone that I felt was a reliable trusty primary communication device since Samsung BlackJack II, this time the LG got the crown.   [ Disclosure: Phone was provided to me free of charge. That has been the case for all of my phones for years, nothing new - I get them all. ]

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  • Artifacts when using SamplerState.LinearClamp in SpriteBatch

    - by Raymond Holmboe
    I'm using XNA 4.0 and VS2010 Express for Windows Phone and Windows Phone SDK 7.1. This is a platform game and I have a map made up of 16x16 textures that is drawn dynamically, tile by tile. When using SpriteBatch to draw my map with LinearClamp, I get artifacts that looks like blurry thin lines. They become visible when the camera moves from one pixel to another and when the camera is still, the artifacts disappear. Here's a small sample of what I mean: Here's how I draw with the spritebatch: SBWorld.Begin(SpriteSortMode.Deferred, BlendState.NonPremultiplied, SamplerState.LinearClamp, DepthStencilState.Default, RasterizerState.CullNone, null, camera.View); When using SamplerState.PointClamp the game just plays horribly (IMHO), so I cannot use that. Why do these lines appear and how do I get rid of those?

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  • How can I solve for the game's world coordinates?

    - by HyperGroups
    I've used 3DReaperDX to get a obj file, the header information are shown as follows: #AR=2.00606, FOV=45.09583(height), Xscale:0.83290, Yscale:0.41519, Zscale:1.0 #************************************************** #ALPHABLENDENABLE: No #ZENABLE: Yes #ZWRITEENABLE: Yes #TWOSIDED: No #INVALID: No #THIN: No #RENDERTARGET_IS_BACKBUFFER: Yes #WIDTH_DO_MATCH: Yes #RGBWRITEDISABLED: No # object DrawCall_0 to come ... g v 2143.35547 6654.99023 25835.37109 v 2243.17773 6296.61523 25957.53906 v 2343.00000 5856.84473 26093.97656 How can I get the game's world coordinates. For example: I can map the scaleTransform to the VertexData scaleTransform={X1scale,Y1scale,Z1scale} {0.8329,0.41519,1.} Is the obj file enough to get the game's world coordinates? I want to put a object in this ground, and the coordinates is the same to that in the Game Engine, And I can place something(with some fixed coordinates) in the Game and then to use 3DReaper to get the obj file. If the file is not enough itself to get the game world coordinates.

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  • The Linux powered LAN Gaming House

    - by sachinghalot
    LAN parties offer the enjoyment of head to head gaming in a real-life social environment. In general, they are experiencing decline thanks to the convenience of Internet gaming, but Kenton Varda is a man who takes his LAN gaming very seriously. His LAN gaming house is a fascinating project, and best of all, Linux plays a part in making it all work.Varda has done his own write ups (short, long), so I'm only going to give an overview here. The setup is a large house with 12 gaming stations and a single server computer.The client computers themselves are rack mounted in a server room, and they are linked to the gaming stations on the floor above via extension cables (HDMI for video and audio and USB for mouse and keyboard). Each client computer, built into a 3U rack mount case, is a well specced gaming rig in its own right, sporting an Intel Core i5 processor, 4GB of RAM and an Nvidia GeForce 560 along with a 60GB SSD drive.Originally, the client computers ran Ubuntu Linux rather than Windows and the games executed under WINE, but Varda had to abandon this scheme. As he explains on his site:"Amazingly, a majority of games worked fine, although many had minor bugs (e.g. flickering mouse cursor, minor rendering artifacts, etc.). Some games, however, did not work, or had bad bugs that made them annoying to play."Subsequently, the gaming computers have been moved onto a more conventional gaming choice, Windows 7. It's a shame that WINE couldn't be made to work, but I can sympathize as it's rare to find modern games that work perfectly and at full native speed. Another problem with WINE is that it tends to suffer from regressions, which is hardly surprising when considering the difficulty of constantly improving the emulation of the Windows API. Varda points out that he preferred working with Linux clients as they were easier to modify and came with less licensing baggage.Linux still runs the server and all of the tools used are open source software. The hardware here is a Intel Xeon E3-1230 with 4GB of RAM. The storage hanging off this machine is a bit more complex than the clients. In addition to the 60GB SSD, it also has 2x1TB drives and a 240GB SDD.When the clients were running Linux, they booted over PXE using a toolchain that will be familiar to anyone who has setup Linux network booting. DHCP pointed the clients to the server which then supplied PXELINUX using TFTP. When booted, file access was accomplished through network block device (NBD). This is a very easy to use system that allows you to serve the contents of a file as a block device over the network. The client computer runs a user mode device driver and the device can be mounted within the file system using the mount command.One snag with offering file access via NBD is that it's difficult to impose any security restrictions on different areas of the file system as the server only sees a single file. The advantage is perfomance as the client operating system simply sees a block device, and besides, these security issues aren't relevant in this setup.Unfortunately, Windows 7 can't use NBD, so, Varda had to switch to iSCSI (which works in both server and client mode under Linux). His network cards are not compliant with this standard when doing a netboot, but fortunately, gPXE came to the rescue, and he boostraps it over PXE. gPXE is also available as an ISO image and is worth knowing about if you encounter an awkward machine that can't manage a network boot. It can also optionally boot from a HTTP server rather than the more traditional TFTP server.According to Varda, booting all 12 machines over the Gigabit Ethernet network is surprisingly fast, and once booted, the machines don't seem noticeably slower than if they were using local storage. Once loaded, most games attempt to load in as much data as possible, filling the RAM, and the the disk and network bandwidth required is small. It's worth noting that these are aspects of this project that might differ from some other thin client scenarios.At time of writing, it doesn't seem as though the local storage of the client machines is being utilized. Instead, the clients boot into Windows from an image on the server that contains the operating system and the games themselves. It uses the copy on write feature of LVM so that any writes from a client are added to a differencing image allocated to that client. As the administrator, Varda can log into the Linux server and authorize changes to the master image for updates etc.SummaryOverall, Varda estimates the total cost of the project at about $40,000, and of course, he needed a property that offered a large physical space in order to house the computers and the gaming workstations. Obviously, this project has stark differences to most thin client projects. The balance between storage, network usage, GPU power and security would not be typical of an office installation, for example. The only letdown is that WINE proved to be insufficiently compatible to run a wide variety of modern games, but that is, perhaps, asking too much of it, and hats off to Varda for trying to make it work.

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  • When is my View too smart?

    - by Kyle Burns
    In this posting, I will discuss the motivation behind keeping View code as thin as possible when using patterns such as MVC, MVVM, and MVP.  Once the motivation is identified, I will examine some ways to determine whether a View contains logic that belongs in another part of the application.  While the concepts that I will discuss are applicable to most any pattern which favors a thin View, any concrete examples that I present will center on ASP.NET MVC. Design patterns that include a Model, a View, and other components such as a Controller, ViewModel, or Presenter are not new to application development.  These patterns have, in fact, been around since the early days of building applications with graphical interfaces.  The reason that these patterns emerged is simple – the code running closest to the user tends to be littered with logic and library calls that center around implementation details of showing and manipulating user interface widgets and when this type of code is interspersed with application domain logic it becomes difficult to understand and much more difficult to adequately test.  By removing domain logic from the View, we ensure that the View has a single responsibility of drawing the screen which, in turn, makes our application easier to understand and maintain. I was recently asked to take a look at an ASP.NET MVC View because the developer reviewing it thought that it possibly had too much going on in the view.  I looked at the .CSHTML file and the first thing that occurred to me was that it began with 40 lines of code declaring member variables and performing the necessary calculations to populate these variables, which were later either output directly to the page or used to control some conditional rendering action (such as adding a class name to an HTML element or not rendering another element at all).  This exhibited both of what I consider the primary heuristics (or code smells) indicating that the View is too smart: Member variables – in general, variables in View code are an indication that the Model to which the View is being bound is not sufficient for the needs of the View and that the View has had to augment that Model.  Notable exceptions to this guideline include variables used to hold information specifically related to rendering (such as a dynamically determined CSS class name or the depth within a recursive structure for indentation purposes) and variables which are used to facilitate looping through collections while binding. Arithmetic – as with member variables, the presence of arithmetic operators within View code are an indication that the Model servicing the View is insufficient for its needs.  For example, if the Model represents a line item in a sales order, it might seem perfectly natural to “normalize” the Model by storing the quantity and unit price in the Model and multiply these within the View to show the line total.  While this does seem natural, it introduces a business rule to the View code and makes it impossible to test that the rounding of the result meets the requirement of the business without executing the View.  Within View code, arithmetic should only be used for activities such as incrementing loop counters and calculating element widths. In addition to the two characteristics of a “Smart View” that I’ve discussed already, this View also exhibited another heuristic that commonly indicates to me the need to refactor a View and make it a bit less smart.  That characteristic is the existence of Boolean logic that either does not work directly with properties of the Model or works with too many properties of the Model.  Consider the following code and consider how logic that does not work directly with properties of the Model is just another form of the “member variable” heuristic covered earlier: @if(DateTime.Now.Hour < 12) {     <div>Good Morning!</div> } else {     <div>Greetings</div> } This code performs business logic to determine whether it is morning.  A possible refactoring would be to add an IsMorning property to the Model, but in this particular case there is enough similarity between the branches that the entire branching structure could be collapsed by adding a Greeting property to the Model and using it similarly to the following: <div>@Model.Greeting</div> Now let’s look at some complex logic around multiple Model properties: @if (ModelPageNumber + Model.NumbersToDisplay == Model.PageCount         || (Model.PageCount != Model.CurrentPage             && !Model.DisplayValues.Contains(Model.PageCount))) {     <div>There's more to see!</div> } In this scenario, not only is the View code difficult to read (you shouldn’t have to play “human compiler” to determine the purpose of the code), but it also complex enough to be at risk for logical errors that cannot be detected without executing the View.  Conditional logic that requires more than a single logical operator should be looked at more closely to determine whether the condition should be evaluated elsewhere and exposed as a single property of the Model.  Moving the logic above outside of the View and exposing a new Model property would simplify the View code to: @if(Model.HasMoreToSee) {     <div>There’s more to see!</div> } In this posting I have briefly discussed some of the more prominent heuristics that indicate a need to push code from the View into other pieces of the application.  You should now be able to recognize these symptoms when building or maintaining Views (or the Models that support them) in your applications.

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