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  • How to use Fixedsys in the Gnome Terminal, or wherever monospaced fonts are required

    - by Walter Tross
    I think that the Fixedsys font is one of the most readable monospaced fonts for programming. It has zero antialiasing, with vertical lines mostly 2 pixels wide. Close to ideal for current monitor dot pitches, in my eyes (literally). After years of Windows at home (for family reasons) and Linux servers at work accessed through Cygwin on Windows (for company policy reasons), with Fixedsys as the shell and IDE font, I have decided to switch to the Ubuntu desktop. Eclipse and gedit are no problem, they accept the Fixedsys Excelsior TTF font. But the Gnome Terminal only accepts monospaced fonts. Although Fixedsys Excelsior is essentially monospaced, it contains larger glyphs (mostly for eastern languages), and also some ligatures. Since apparently ALL characters must have the same width for a font to be recognized as monospaced, Fixedsys Excelsior cannot be selected in all those contexts where monospaced fonts are required, including gnome-terminal. So what is the easiest/cleanest way to use a Fixedsys clone font in contexts that only accept monospaced fonts?

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  • Expensive HDMI Cables Make No Difference

    - by Jason Fitzpatrick
    While we’re no strangers to spreading the news that expensive HDMI cables are a ripoff, we’re happy to share yet another study that shows there’s zero difference between a $5 cable and a $95 one. Over at the British hardware review site Expert Reviews, they subjected a wide selection of HDMI cables to extensive tests in a bid to produce the end-all examination of whether or not a premium HDMI cable could actually produce a better signal. They used capture cards, pixel-by-pixel comparison of output, and other techniques to pick over individual frames until they ultimately reached the same conclusion everyone outside of the Monster sales staff had already reached: you’re getting absolutely no benefit to spending $100 on cable that can be had for under five bucks. Hit up the link below to read over their methodology. Expensive Cables Make Absolutely No Difference [via Geek News Central] HTG Explains: What Is RSS and How Can I Benefit From Using It? HTG Explains: Why You Only Have to Wipe a Disk Once to Erase It HTG Explains: Learn How Websites Are Tracking You Online

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  • How to determine number of resources to be allocated in a software project

    - by aditi
    Last day I have been interviewed and the interviwer asked me as given the outline of a project, how can we determine the number of resources to be needed for the same? I donot know to do do so? Is there any standard way of doing so? or is it based on the experience? or how.... I am pretty new in this activity and my knowledge is zero at present .... so any clear explanation with some example(simple) will help me(and people like me) to understand this. Thanks

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  • Settings xorg.conf to be used with VESA driver?

    - by Fernando Costa
    I have an brand new installation of Ubuntu 9.10 (karmic version) where everything is fine except the video resolution. In Ubuntu 9.10, the file xorg.conf is empty by default. I'm using an onboard video card, and Ubuntu can not find the right resolution for me. It always uses 800x600, but I need at least 1024x768. Also, my monitor is listed as Unknown Type. Ubuntu did find the right resolution when I changed the monitor to a Samsung monitor. By the way what are the generic settings to put inside xorg.conf? What is the settings for Refresh Rate, for example, I got a resolution of 1280x800, but the Refresh Rate generally between 60 ~ 80 htz is ZERO on my resolution.. In 1024 resolution my Refresh Rate is 75 htz.. What is going on with my resolution and how to modify the Refresh Rate?? Many Thanks!

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  • SPARC T4-4 Delivers World Record Performance on Oracle OLAP Perf Version 2 Benchmark

    - by Brian
    Oracle's SPARC T4-4 server delivered world record performance with subsecond response time on the Oracle OLAP Perf Version 2 benchmark using Oracle Database 11g Release 2 running on Oracle Solaris 11. The SPARC T4-4 server achieved throughput of 430,000 cube-queries/hour with an average response time of 0.85 seconds and the median response time of 0.43 seconds. This was achieved by using only 60% of the available CPU resources leaving plenty of headroom for future growth. The SPARC T4-4 server operated on an Oracle OLAP cube with a 4 billion row fact table of sales data containing 4 dimensions. This represents as many as 90 quintillion aggregate rows (90 followed by 18 zeros). Performance Landscape Oracle OLAP Perf Version 2 Benchmark 4 Billion Fact Table Rows System Queries/hour Users* Response Time (sec) Average Median SPARC T4-4 430,000 7,300 0.85 0.43 * Users - the supported number of users with a given think time of 60 seconds Configuration Summary and Results Hardware Configuration: SPARC T4-4 server with 4 x SPARC T4 processors, 3.0 GHz 1 TB memory Data Storage 1 x Sun Fire X4275 (using COMSTAR) 2 x Sun Storage F5100 Flash Array (each with 80 FMODs) Redo Storage 1 x Sun Fire X4275 (using COMSTAR with 8 HDD) Software Configuration: Oracle Solaris 11 11/11 Oracle Database 11g Release 2 (11.2.0.3) with Oracle OLAP option Benchmark Description The Oracle OLAP Perf Version 2 benchmark is a workload designed to demonstrate and stress the Oracle OLAP product's core features of fast query, fast update, and rich calculations on a multi-dimensional model to support enhanced Data Warehousing. The bulk of the benchmark entails running a number of concurrent users, each issuing typical multidimensional queries against an Oracle OLAP cube consisting of a number of years of sales data with fully pre-computed aggregations. The cube has four dimensions: time, product, customer, and channel. Each query user issues approximately 150 different queries. One query chain may ask for total sales in a particular region (e.g South America) for a particular time period (e.g. Q4 of 2010) followed by additional queries which drill down into sales for individual countries (e.g. Chile, Peru, etc.) with further queries drilling down into individual stores, etc. Another query chain may ask for yearly comparisons of total sales for some product category (e.g. major household appliances) and then issue further queries drilling down into particular products (e.g. refrigerators, stoves. etc.), particular regions, particular customers, etc. Results from version 2 of the benchmark are not comparable with version 1. The primary difference is the type of queries along with the query mix. Key Points and Best Practices Since typical BI users are often likely to issue similar queries, with different constants in the where clauses, setting the init.ora prameter "cursor_sharing" to "force" will provide for additional query throughput and a larger number of potential users. Except for this setting, together with making full use of available memory, out of the box performance for the OLAP Perf workload should provide results similar to what is reported here. For a given number of query users with zero think time, the main measured metrics are the average query response time, the median query response time, and the query throughput. A derived metric is the maximum number of users the system can support achieving the measured response time assuming some non-zero think time. The calculation of the maximum number of users follows from the well-known response-time law N = (rt + tt) * tp where rt is the average response time, tt is the think time and tp is the measured throughput. Setting tt to 60 seconds, rt to 0.85 seconds and tp to 119.44 queries/sec (430,000 queries/hour), the above formula shows that the T4-4 server will support 7,300 concurrent users with a think time of 60 seconds and an average response time of 0.85 seconds. For more information see chapter 3 from the book "Quantitative System Performance" cited below. -- See Also Quantitative System Performance Computer System Analysis Using Queueing Network Models Edward D. Lazowska, John Zahorjan, G. Scott Graham, Kenneth C. Sevcik external local Oracle Database 11g – Oracle OLAP oracle.com OTN SPARC T4-4 Server oracle.com OTN Oracle Solaris oracle.com OTN Oracle Database 11g Release 2 oracle.com OTN Disclosure Statement Copyright 2012, Oracle and/or its affiliates. All rights reserved. Oracle and Java are registered trademarks of Oracle and/or its affiliates. Other names may be trademarks of their respective owners. Results as of 11/2/2012.

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  • Free Universal Construction Kit Links Different Construction Toy Systems

    - by Jason Fitzpatrick
    If you or a young tinker in your household is disappointed that there is no way to link LEGO bricks and Lincoln Logs (or other construction toys on the market) this project is for you. Free Universal Construction Kit is project oriented around creating inter-operable linking bricks that allow the user to link previously non-compatible building system. Using the bricks you can, for example, attach LEGO bricks to a K’Nex construction. The adapter bricks are all available as free 3D printer models–download them, fire up your 3D printer, and start mish-mashing your construction sets. Free Universal Construction Kits [via Make] The HTG Guide to Hiding Your Data in a TrueCrypt Hidden Volume Make Your Own Windows 8 Start Button with Zero Memory Usage Reader Request: How To Repair Blurry Photos

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  • Is there an open source license for this?

    - by Philip
    I have written code at home, on my own time and using my own knowledge and equipment, while under no contract or NDA. I want to make this code open source so that I can use it in software I write for an employer, without denying myself the right to use it at home or elsewhere later. I'm not sure if saying it is in the "public domain" would fit this purpose, or if I need to find an open source license. I want anyone to be able to use the code in closed source proprietary software with zero requirements for including a license with the source or binary. And I want to minimize the risk of anyone being sued for using it. (I'm aware that one can never be 100% safe from being sued.) Is there an open source license that fits this purpose? To what extent is what I want to do even possible? I wouldn't mind putting the license in comments in the code files themselves, but that obviously doesn't go with the binary.

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  • Unable to mount external hard drive

    - by arranjamesroche
    Basically I my 12.10 update crashed halfway through, so I've had to start again and put all my data onto an external HDD. It was all going fine until this came up : Error mounting /dev/sdb1 at /media/amy/CA47-8339: Command-line `mount -t "vfat" -o "uhelper=udisks2,nodev,nosuid,uid=1000,gid=1000,shortname=mixed,dmask=0077,utf8=1,showexec,flush" "/dev/sdb1" "/media/amy/CA47-8339"' exited with non-zero exit status 32: mount: wrong fs type, bad option, bad superblock on /dev/sdb1, missing codepage or helper program, or other error In some cases useful info is found in syslog - try dmesg | tail or so When I tried to restore my info off the HDD. Now I'm stuck completely clueless as to how I'll get anything off the hard drive.

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  • How to Use Windows 8's Storage Spaces to Mirror & Combine Drives

    - by Chris Hoffman
    “Storage Spaces” is a new feature in Windows 8 that can combine multiple hard drives into a single virtual drive. It can mirror data across multiple drives for redundancy or combine multiple physical drives into a single pool of storage. You can even create pools of storage larger than the amount of physical storage space you have available. When the physical storage fills up, you can plug in another drive and take advantage of it with no additional configuration required. Storage Spaces is similar to RAID or LVM on Linux. The HTG Guide to Hiding Your Data in a TrueCrypt Hidden Volume Make Your Own Windows 8 Start Button with Zero Memory Usage Reader Request: How To Repair Blurry Photos

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  • Switch Gmail Icons Back to Text Labels

    - by Jason Fitzpatrick
    If Gmail’s icon-based buttons annoy you, it’s now possible to switch them back to the old text labels with a simple settings toggle. At MakeUseOf they highlight the new option in Gmail and how you can switch back to the old button layout: So how do you make that happen? All you have to do is click on the cog button, choose “Settings”, and go to the the General tab. Scroll down to find the “Button labels” setting, and change it from icons to text. I know what I’ll be doing shortly; text-based button labels here I come. [via MakeUseOf] Make Your Own Windows 8 Start Button with Zero Memory Usage Reader Request: How To Repair Blurry Photos HTG Explains: What Can You Find in an Email Header?

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  • What You Said: How You Organize Your Apps

    - by Jason Fitzpatrick
    Earlier this week we asked you to share your tips and tricks for keeping your apps organized and accessible; now we’re back to showcase some great reader tips to help you manage your mountain of apps. One of the trends was striving for consistency across environments. Henrique highlights how this plays out on a dual OS setup: On my windows desktop I use the taskbar and to keep my day to day applications (basically firefox, itunes, office, adobe, evernote and wunderkit), and whenever I need something else, I use windows built in search, which is quite fast, despite needing a few more clicks than spotlight would. On my macbook the dock is basically mirrors my taskbar, and I use spotlight for other applications, but launchpad is wining my heart a bit more every day. It’s faster then than accessing the applications folder and the windows start menu, and possibly even than spotlight, at least for apps How To Properly Scan a Photograph (And Get An Even Better Image) The HTG Guide to Hiding Your Data in a TrueCrypt Hidden Volume Make Your Own Windows 8 Start Button with Zero Memory Usage

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  • Need Help Changing Owner of External HArd Drive

    - by Thomas Ballew
    My understanding of code is about zero. I can open a terminal window, and type commands that are given to me, but that's about it. If someone can help me with this question, and explain at a level I'm likely to understand, thanks. If not, thanks anyway. I have an external hard drive with two partitions. I bought this drive when my operating system was Apple, 10.5 or so, and it was formatted as HFS+ with that system. Now, connecting the HD to my Linux system, I can read files, but I have about 1.5 TB of space that I can't use, because I am not the owner of the file, so can't write to the HD. Short of reformatting the HD, is there a way for me to set the permissions for the HD so I can write to it? Again, thank you.

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  • Java - learning / migrating fast

    - by Yippie-Kai-Yay
    Hello! This is not one of those questions like "How do I learn Java extremely fast, I know nothing about programming, but I heard Java is cool, yo". I have an interview for a Java Software Developer in a couple of weeks and the thing is that I think that I know C++ really good and I am somewhat good at C# (like, here I can probably answer on a lot of questions related to these languages), but I have almost zero experience with Java. I have a lot of projects written in both languages, I participiated in several open-source projects (mostly C++, though). Now, what should I do (in your opinion) to prepare myself for this Java interview. I guess migrating from C# to Java should be kind of fast, especially when you know a lot about programming in global, patterns, modern techniques and have a lot of practical experience behind you. But still two weeks is obviously not enough to get Java in-depth - so what should I focus on to have the best chances to pass the interview? Thank you.

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  • Move Data into the grid for scalable, predictable response times

    - by JuergenKress
    CloudTran is pleased to introduce the availability of the CloudTran Transaction and Persistence Manager for creating scalable, reliable data services on the Oracle Coherence In-Memory Data Grid (IMDG). Use of IMDG architectures has been key to handling today’s web-scale loads because it eliminates database latency by storing important and frequently access data in memory instead of on disk. The CloudTran product lets developers easily use an IMDG for full ACID-compliant transactions without having to be concerned about the location or spread of data. The system has its own implementation of fast, scalable distributed transactions that does NOT depend on XA protocols but still guarantees all ACID properties. Plus, CloudTran asynchronously replicates data going into the IMDG to back-end datastores and back-up data centers, again ensuring ACID properties. CloudTran can be accessed through Java Persistence API (JPA via TopLink Grid) and now, through a new Low-Level API, or LLAPI. This is ideal for use in SOA applications that need data reliability, high availability, performance, and scalability. It is still in its limited beta release, the LLAPI gives developers the ability to use standard put/remove logic available in Coherence and then wrap logic with simple Spring annotations or XML+AspectJ to start transactions. An important feature of LLAPI is the ability to join transactions. This is a common outcome for SOA applications that need to reduce network traffic by aggregating data into single cache entries and then doing SOA service processing in the node holding the data. This results in the need to orchestrate transaction processing across multiple service calls. CloudTran has the capability to handle these “multi-client” transactions at speed with no loss in ACID properties. Developing software around an IMDG like Oracle Coherence is an important choice for today’s web-scale applications and services. But this introduces new architectural considerations to maintain scalability in light of increased network loads and data movement. Without using CloudTran, developers are faced with an incredibly difficult task to ensure data reliability, availability, performance, and scalability when working with an IMDG. Working with highly distributed data that is entirely volatile while stored in memory presents numerous edge cases where failures can result in data loss. The CloudTran product takes care of all of this, leaving developers with the confidence and peace of mind that all data is processed correctly. For those interested in evaluating the CloudTran product and IMDGs, take a look at this link for more information: http://www.CloudTran.com/downloadAPI.ph , or send your questions to [email protected]. SOA & BPM Partner Community For regular information on Oracle SOA Suite become a member in the SOA & BPM Partner Community for registration please visit  www.oracle.com/goto/emea/soa (OPN account required) If you need support with your account please contact the Oracle Partner Business Center. Blog Twitter LinkedIn Mix Forum Technorati Tags: CloudTran,data grid,M,SOA Community,Oracle SOA,Oracle BPM,BPM,Community,OPN,Jürgen Kress

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  • How to Seamlessly Extend the Windows Server Trial to 240 Days

    - by Jason Faulkner
    The Microsoft evaluation releases of their products are incredibly valuable and useful tools as they allow you to have an unlimited number of test, demo and development environments to work with at no cost. The only catch is evaluation releases are time limited, so the more time you can squeeze out of them, the more useful they can be. Here we are going to show you how to extend the usage time of the Windows Server 2008 R2 evaluation release to its maximum. Make Your Own Windows 8 Start Button with Zero Memory Usage Reader Request: How To Repair Blurry Photos HTG Explains: What Can You Find in an Email Header?

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  • Choice Hotels' Rain Fletcher talks WebLogic Server

    - by ruma.sanyal
    Choice Hotels International's Vice President of Application Development & Architecture, Rain Fletcher, discusses how Oracle WebLogic Server supports their mission-critical reservation system. Choice Hotels has very stringent requirements of their reservation systems servicing over hundred thousand check-in and check-outs every day. The reservation system needs to be up 24X7 and unplanned outages are not acceptable. Choice Hotels chose WebLogic because it is the #1 app server in the marketplace with high uptime, zero downtime deployment, and best in class clustering abilities. Listen to Rain discuss Choice Hotels future plans and how Oracle bestows them with competitive advantage.

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  • ATI Proprietary Driver Over/Underscan setting ignored after reboot

    - by Lassi
    I installed the proprietary driver (fglrx-updates) on Ubuntu 12.10 64-bit for my graphics card (ATI Radeon HD 7570). I am using two displays, one connected with DVI, one with HDMI. I set the desktop to be expanded to both screens and disabled the under scan for the HDMI screen, which is always for some reason enabled on HDMI screens. Now the issue. Everything was fine until I restarted my computer. After reboot, the screen connected with HDMI cable had the black borders again, meaning that the under scan is again enabled. I checked the ATI CCC, and under scan was disabled. However, moving the slider to enable under scan and then back to zero fixed the issue -- temporarily. The same issue is repeated every time I restart my computer. The settings remains the same, but the computer seems to ignore it. Any ideas how I could solve the issue?

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  • Learning about security and finding exploits

    - by Jayraj
    First things first: I have absolutely no interest in learning how to crack systems for personal enrichment, hurting other people or doing anything remotely malicious. I understand the basis of many exploits (XSS, SQL injection, use after free etc.), though I've never performed any myself. I even have some idea about how to guard web applications from common exploits (like the aforementioned XSS and SQL injection) Reading this question about the Internet Explorer zero-day vulnerability from the Security SE piqued my curiosity and made me wonder: how did someone even find out about this exploit? What tools did they use? How did they know what to look for? I'm wary about visiting hacker dens online for fear of getting my own system infected (the Defcon stories make me paranoid). So what's a good, safe place to start learning?

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  • how to set the border = 0 on GtkBox (dialog-Vbox-Element) in Glade on Dialog, which was creadted via "quickly add dialog"

    - by Marian Lux
    To make the Toolbar look native in Ubuntu (like the application in this video: https://www.youtube.com/watch?feature=player_embedded&v=sO8hiPreNBg), I don't want to show a border. In my main window of my application I am able to set the property for the border width to zero on the GtkBox under tab "common". But on a dialog (created via "quickly add dialog") there is no option on the GtkBox to set the property under "common". The property for the border width sill not appears under common! What can I do to solve this problem? I tried to create a Window-Element and tried to delete the Dialog-Element. Result: Then I was able to set this property in Glade but I could not do anything with the Window-Element and its Child-Elements (e.g. set the native look for its toolbar) in the corresponding .py-File (for the ui-File) because I destroyed dependencies...

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  • How are Java ByteBuffer's limit and position variable's updated?

    - by Dummy Derp
    There are two scenarios: writing and reading Writing: Whenever I write something to the ByteBuffer by calling its put(byte[]) method the position variable is incremented as: current position + size of byte[] and limit stays at the max. If, however, I put the data in a view buffer then I will have to, manually, calculate and update the position Before I call the write(ByteBuffer) method of the channel to write something, I will have to flip() the Bytebuffer so that position points to zero and limit points to the last byte that was written to the ByteBuffer. Reading: Whenever I call the read(ByteBuffer) method of a channel to read something, the position variable stays at 0 and the limit variable of the ByteBuffer points to the last byte that was read. So, if the ByteBuffer is smaller than the file being read, the limit variable is pushed to max This means that the ByteBuffer is already flipped and I can proceed to extracting the values from the ByteBuffer. Please, correct me where I am wrong :)

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  • Ask The Readers: How Do You Organize Your Apps?

    - by Jason Fitzpatrick
    Application organization and launching has improved significantly over the years but there’s always room for improvement and customization. This week we’re interested in hearing about your tips, tricks, and tools for efficiently organizing and launching your apps. Do you stick with the OS defaults? Do you use third-party app launchers to streamline your workflow? Whether you’ve done some minor tweaking to the Start Menu or installed a brand new application dock, we want to hear all about it. Sound off in the comments with your tips and tricks for avoiding time wasted searching for application shortcuts–check back in on Friday for the What You Said roundup to see how your fellow readers are wrangling their applications. The HTG Guide to Hiding Your Data in a TrueCrypt Hidden Volume Make Your Own Windows 8 Start Button with Zero Memory Usage Reader Request: How To Repair Blurry Photos

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  • High Speed Photographs Capture Pellet Gun Destruction

    - by Jason Fitzpatrick
    What do you get when you combine high speed flash photography, a carefully focused camera, and pellet gun? Gloriously detailed pictures of pellets tearing apart fruit, cans, ceramic gnomes, and more. Alan Sailer has a passion; in his garage studio he photographs all manner of objects–bottles, raspberries, candy, soda cans–at the moment a pellet shot from a pellet gun tears them apart. The results are beautiful and reminescent of early high-speed photos by photography pioneer Edgerton Born. Hit up the link below to check out the collection and read more about his process. Alan Sailer’s High Speed Photographs [via FlavorWire] Make Your Own Windows 8 Start Button with Zero Memory Usage Reader Request: How To Repair Blurry Photos HTG Explains: What Can You Find in an Email Header?

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  • Cannot mount one usb disc, although other mounts automatically after 12.10 upgrade

    - by Allen Williams
    Since upgrading to 12.10, switching on or attempting to mount one of my usb hard drives gives this error message: Error mounting system-managed device /dev/sdg1: Command-line `mount "/mnt/usb-ST350041_8AS_60CAFFFFFFFF-0:0-part1"' exited with non-zero exit status 32: mount: wrong fs type, bad option, bad superblock on /dev/sdg1, missing codepage or helper program, or other error In some cases useful info is found in syslog - try dmesg | tail or so dmesg | tail gives (inter alia): [ 1080.727830] sdg: sdg1 [ 1080.732003] sd 8:0:0:0: [sdg] Attached SCSI disk [ 1081.383633] FAT-fs (sdg1): Unrecognized mount option "x-gvfs-show" or missing value [ 1871.160973] sdg: sdg1 The drive cannot be mounted, but is recognized by the system as a "place". I am not a technical bod; I cannot take this further myself and any help would be much appreciated.

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  • Physics System ignores collision in some rare cases

    - by Gajoo
    I've been developing a simple physics engine for my game. since the game physics is very simple I've decided to increase accuracy a little bit. Instead of formal integration methods like fourier or RK4, I'm directly computing the results after delta time "dt". based on the very first laws of physics : dx = 0.5 * a * dt^2 + v0 * dt dv = a * dt where a is acceleration and v0 is object's previous velocity. Also to handle collisions I've used a method which is somehow different from those I've seen so far. I'm detecting all the collision in the given time frame, stepping the world forward to the nearest collision, resolving it and again check for possible collisions. As I said the world consist of very simple objects, so I'm not loosing any performance due to multiple collision checking. First I'm checking if the ball collides with any walls around it (which is working perfectly) and then I'm checking if it collides with the edges of the walls (yellow points in the picture). the algorithm seems to work without any problem except some rare cases, in which the collision with points are ignored. I've tested everything and all the variables seem to be what they should but after leaving the system work for a minute or two the system the ball passes through one of those points. Here is collision portion of my code, hopefully one of you guys can give me a hint where to look for a potential bug! void PhysicalWorld::checkForPointCollision(Vec2 acceleration, PhysicsComponent& ball, Vec2& collisionNormal, float& collisionTime, Vec2 target) { // this function checks if there will be any collision between a circle and a point // ball contains informations about the circle (it's current velocity, position and radius) // collisionNormal is an output variable // collisionTime is also an output varialbe // target is the point I want to check for collisions Vec2 V = ball.mVelocity; Vec2 A = acceleration; Vec2 P = ball.mPosition - target; float wallWidth = mMap->getWallWidth() / (mMap->getWallWidth() + mMap->getHallWidth()) / 2; float r = ball.mRadius / (mMap->getWallWidth() + mMap->getHallWidth()); // r is ball radius scaled to match actual rendered object. if (A.any()) // todo : I need to first correctly solve the collisions in case there is no acceleration return; if (V.any()) // if object is not moving there will be no collisions! { float D = P.x * V.y - P.y * V.x; float Delta = r*r*V.length2() - D*D; if(Delta < eps) return; Delta = sqrt(Delta); float sgnvy = V.y > 0 ? 1: (V.y < 0?-1:0); Vec2 c1(( D*V.y+sgnvy*V.x*Delta) / V.length2(), (-D*V.x+fabs(V.y)*Delta) / V.length2()); Vec2 c2(( D*V.y-sgnvy*V.x*Delta) / V.length2(), (-D*V.x-fabs(V.y)*Delta) / V.length2()); float t1 = (c1.x - P.x) / V.x; float t2 = (c2.x - P.x) / V.x; if(t1 > eps && t1 <= collisionTime) { collisionTime = t1; collisionNormal = c1; } if(t2 > eps && t2 <= collisionTime) { collisionTime = t2; collisionNormal = c2; } } } // this function should step the world forward by dt. it doesn't check for collision of any two balls (components) // it just checks if there is a collision between the current component and 4 points forming a rectangle around it. void PhysicalWorld::step(float dt) { for (unsigned i=0;i<mObjects.size();i++) { PhysicsComponent &current = *mObjects[i]; Vec2 acceleration = current.mForces * current.mInvMass; float rt=dt; // stores how much more the world should advance while(rt > eps) { float collisionTime = rt; Vec2 collisionNormal = Vec2(0,0); float halfWallWidth = mMap->getWallWidth() / (mMap->getWallWidth() + mMap->getHallWidth()) / 2; // we check if there is any collision with any of those 4 points around the ball // if there is a collision both collisionNormal and collisionTime variables will change // after these functions collisionTime will be exactly the value of nearest collision (if any) // and if there was, collisionNormal will report in which direction the ball should return. checkForPointCollision(acceleration,current,collisionNormal,collisionTime,Vec2(floor(current.mPosition.x) + halfWallWidth,floor(current.mPosition.y) + halfWallWidth)); checkForPointCollision(acceleration,current,collisionNormal,collisionTime,Vec2(floor(current.mPosition.x) + halfWallWidth, ceil(current.mPosition.y) - halfWallWidth)); checkForPointCollision(acceleration,current,collisionNormal,collisionTime,Vec2( ceil(current.mPosition.x) - halfWallWidth,floor(current.mPosition.y) + halfWallWidth)); checkForPointCollision(acceleration,current,collisionNormal,collisionTime,Vec2( ceil(current.mPosition.x) - halfWallWidth, ceil(current.mPosition.y) - halfWallWidth)); // either if there is a collision or if there is not we step the forward since we are sure there will be no collision before collisionTime current.mPosition += collisionTime * (collisionTime * acceleration * 0.5 + current.mVelocity); current.mVelocity += collisionTime * acceleration; // if the ball collided with anything collisionNormal should be at least none zero in one of it's axis if (collisionNormal.any()) { collisionNormal *= Dot(collisionNormal, current.mVelocity) / collisionNormal.length2(); current.mVelocity -= 2 * collisionNormal; // simply reverse velocity along collision normal direction } rt -= collisionTime; } // reset all forces for current object so it'll be ready for later game event current.mForces.zero(); } }

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  • Platformer Starter Kit - Collision Issues

    - by Cyral
    I'm having trouble with my game that is based off the XNA Platformer starter kit. My game uses smaller tiles (16x16) then the original (32x40) which I'm thinking may be having an effect on collision (Being it needs to be more precise). Standing on the edge of a tile and jumping causes the player to move off the the tile when he lands. And 80% of the time, when the player lands, he goes flying though SOLID tiles in a diagonal fashion. This is very annoying as it is almost impossible to test other features, when spawning and jumping will result in the player landing in another part of the level or falling off the edge completely. The code is as follows: /// <summary> /// Updates the player's velocity and position based on input, gravity, etc. /// </summary> public void ApplyPhysics(GameTime gameTime) { float elapsed = (float)gameTime.ElapsedGameTime.TotalSeconds; Vector2 previousPosition = Position; // Base velocity is a combination of horizontal movement control and // acceleration downward due to gravity. velocity.X += movement * MoveAcceleration * elapsed; velocity.Y = MathHelper.Clamp(velocity.Y + GravityAcceleration * elapsed, -MaxFallSpeed, MaxFallSpeed); velocity.Y = DoJump(velocity.Y, gameTime); // Apply pseudo-drag horizontally. if (IsOnGround) velocity.X *= GroundDragFactor; else velocity.X *= AirDragFactor; // Prevent the player from running faster than his top speed. velocity.X = MathHelper.Clamp(velocity.X, -MaxMoveSpeed, MaxMoveSpeed); // Apply velocity. Position += velocity * elapsed; Position = new Vector2((float)Math.Round(Position.X), (float)Math.Round(Position.Y)); // If the player is now colliding with the level, separate them. HandleCollisions(); // If the collision stopped us from moving, reset the velocity to zero. if (Position.X == previousPosition.X) velocity.X = 0; if (Position.Y == previousPosition.Y) velocity.Y = 0; } /// <summary> /// Detects and resolves all collisions between the player and his neighboring /// tiles. When a collision is detected, the player is pushed away along one /// axis to prevent overlapping. There is some special logic for the Y axis to /// handle platforms which behave differently depending on direction of movement. /// </summary> private void HandleCollisions() { // Get the player's bounding rectangle and find neighboring tiles. Rectangle bounds = BoundingRectangle; int leftTile = (int)Math.Floor((float)bounds.Left / Tile.Width); int rightTile = (int)Math.Ceiling(((float)bounds.Right / Tile.Width)) - 1; int topTile = (int)Math.Floor((float)bounds.Top / Tile.Height); int bottomTile = (int)Math.Ceiling(((float)bounds.Bottom / Tile.Height)) - 1; // Reset flag to search for ground collision. isOnGround = false; // For each potentially colliding tile, for (int y = topTile; y <= bottomTile; ++y) { for (int x = leftTile; x <= rightTile; ++x) { // If this tile is collidable, ItemCollision collision = Level.GetCollision(x, y); if (collision != ItemCollision.Passable) { // Determine collision depth (with direction) and magnitude. Rectangle tileBounds = Level.GetBounds(x, y); Vector2 depth = RectangleExtensions.GetIntersectionDepth(bounds, tileBounds); if (depth != Vector2.Zero) { float absDepthX = Math.Abs(depth.X); float absDepthY = Math.Abs(depth.Y); // Resolve the collision along the shallow axis. if (absDepthY < absDepthX || collision == ItemCollision.Platform) { // If we crossed the top of a tile, we are on the ground. if (previousBottom <= tileBounds.Top) isOnGround = true; // Ignore platforms, unless we are on the ground. if (collision == ItemCollision.Impassable || IsOnGround) { // Resolve the collision along the Y axis. Position = new Vector2(Position.X, Position.Y + depth.Y); // Perform further collisions with the new bounds. bounds = BoundingRectangle; } } else if (collision == ItemCollision.Impassable) // Ignore platforms. { // Resolve the collision along the X axis. Position = new Vector2(Position.X + depth.X, Position.Y); // Perform further collisions with the new bounds. bounds = BoundingRectangle; } } } } } // Save the new bounds bottom. previousBottom = bounds.Bottom; } It also tends to jitter a little bit sometimes, I'm solved some of this with some fixes I found here on stackexchange, But Ive only seen one other case of the flying though blocks problem. This question seems to have a similar problem in the video, but mine is more crazy. Again this is a very annoying bug! Any help would be greatly appreciated! EDIT: Speed stuff // Constants for controling horizontal movement private const float MoveAcceleration = 13000.0f; private const float MaxMoveSpeed = 1750.0f; private const float GroundDragFactor = 0.48f; private const float AirDragFactor = 0.58f; // Constants for controlling vertical movement private const float MaxJumpTime = 0.35f; private const float JumpLaunchVelocity = -3500.0f; private const float GravityAcceleration = 3400.0f; private const float MaxFallSpeed = 550.0f; private const float JumpControlPower = 0.14f;

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