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• Soft Shadows in Raytracing 3D to 2D

  - by Myx

  Hello: I wish to implement soft shadows produced by area lights in my raytracer. I'm having trouble generating the random samples. So I have a scene in which I have an area light (represented as a circle) whose world (x,y,z) coordinates of the center are given, the radius is given, the normal of the plane on which the circle lies is given, as well as the color and attenuation factors. The sampling scheme I wish to use is the following: generate samples on the quadrilateral that encompasses the circle and discard points outside the circle until the required number of samples within the circle have been found. I'm having trouble understanding how I can transform the 3D coordinates of the center of the circle to its 2D representation (I don't think I can assume that the projection of the circle is on the x-y axis and thus just get rid of the z-component). I think the plane normal information should be used but I'm not sure how. Any and all suggestions are appreciated.

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• Building webparts with Visual Studio 2010 Express

  - by MalphasWats

  Hi, I'm trying to get started with building my own webparts, planning to follow this MSDN article. I've downloaded Visual C# 2010 Express - I'm not quite at the point where I feel comfortable dropping 1000 big ones yet, and I installed Visual Web Developer 2010 Express via the WPInstaller. Following through the tutorial, aside from the fact that I don't get the option to create a "Web Control Library", a gap I filled with this article, I can't seem to find the sn.exe tool (or the "Visual Studio 2005 Command Prompt"!). I know it's not quite a direct programming related question, but I can't even get the thing going yet! Any help is appreciated. Thanks EDIT:- I think I may be jumping the gun quite considerably, I wrote a simple hello world example and tried to build it but it doesn't have any references to the Microsoft.SharePoint packages and they don't appear in my lists. Am I understanding some more research I've done (namely this) correctly, in that I have to actually have a full installation of actual SharePoint on the machine I'm developing on?

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• Setting the a caret in an JEditor Pane causes an exception.

  - by Elliott

  I have a JeditorPane which has some text in HTML format. When I execute the following command int len = editorPane.getText().length(); The value for len is 7473. But then I try to do the following: editorPane.setCaretPosition(4995); And I get the following exception: java.lang.IllegalArgumentException: bad position: 4995 My understanding is that I should only get this exception if the position at which I'm trying to set the caret is less than 0 or greater than the text length. It is neither. How can this be. Thank you, Elliott

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• Entity Relationship Diagramming

  - by Ben Aston

  I'd like to improve my understanding of cardinality constraints in ER diagrams. I have two entities: User Location But, I want the relationship between these two entities to be many-to-many (a user can be in many locations and a location can have many users). To do this I need to introduce an association class UserLocation. Is it correct to say I now have 3 entities? If I were to draw an ER diagam of the above, would I draw in the UserLocation entity, and would the cardinality look like this? User 1 ------ * User Location * ------ 1 Location

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• Selectively configuring Apache 2 mod_headers for Google Chrome Frame

  - by Adam Cobb

  I am currently evaluating Google Chrome Frame and so far i'm happy with it, but what i'd like to do is selectively use it for certain sections of my website. Some sections require ActiveX so need to be viewed in native IE, whereas others benefit greatly, and may end up requiring, Chrome Frame. I've currently got the following configured in my apache httpd.conf file - <IfModule mod_setenvif.c> <IfModule mod_headers.c> BrowserMatch chromeframe gcf Header append X-UA-Compatible "chrome=1" env=gcf </IfModule> </IfModule> This causes anything coming in via Apache to get the chrome frame stuff added to the headers. What I need is to make this only happen when a user visits particular URL's / particular pages, which i'm currently controlling via RewriteRules. Could anybody explain how I would go about this, as my understanding of the Apache config files isn't brilliant. Thanks.

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• What is C's analogy to LabVIEW's Event Structure?

  - by SiegeX

  One programming construct I use quite a bit in LabVIEW is the Event Structure. This gives me the benefit of not having to needlessly waste CPU cycles via polling but only perform actions when an event I'm interested in is generated. As an experienced LabVIEW programmer with a decent understanding of C, I'm curious how one would go about emulating LabVIEW's event structure in C; preferably under Linux. A small code sample (like the one in the link above) illustrating how this might be done would be much appreciated. Also, if there already exists 3rd party libraries (for Linux) to add this event framework to C, that would be nice to know as well. Thanks.

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• Batch File input validation - Make sure user entered an integer

  - by B2Ben

  I'm experimenting with a DOS batch file to perform a simple operation which requires the user to enter a non-negative integer. I'm using simple batch-file techniques to get user input: @ECHO OFF SET /P UserInput=Please Enter a Number: The user can enter any text they want here, so I would like to add some routine to make sure what the user entered was a valid number. That is... they entered at least one character, and every character is a number from 0 to 9. I'd like something I can feed the UserInput into. At the end of the routine would be like an if/then that would run different statements based on whether or not it was actually a valid number. I've experimented with loops and substrings and such, but my knowledge and understanding is still slim... so any help would be appreciated. I could build an executable, and I know there are nicer ways to do things than batch files, but at least for this task I'm trying to keep it simple by using a batch file.

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• Rails 3: What is the proper way to respond to REST-ful actions with JSON in rails?

  - by Damien Wilson

  Hello SO. I'm trying to make an API for my rails application using JSON responses to RESTful resource controllers. This is a new experience for me, so I'm looking for some guidance and pointers. To start things off: In a rails application, what is the "proper" way to respond with JSON to REST-ful controller methods? (create, update, destroy) Is there an idiomatic way to indicate success/failure through a JSON response? Additional information: I'm currently working with rails 3.0.beta2 I would like to avoid using a plugin or gem to do the grunt work, my goal is to gain a better understanding of how to make a rails 3 API. Links to places I could find more information on the topic would also be appreciated, some quick searching on google didn't do me much good.

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• Sync Framework,LINQ, and my DAL

  - by Refracted Paladin

  I am creating a WPF app that needs to allow users to work in a temporary disconnected state and I plan to use a Local Database Cache. My question's are about my data access layer. Do you typically create the whole DAL to point at the Cache or both and create a switching mechanism? Is Entity's a good way to go for my DAL against the Cache? I am used to L2S but my understanding is that I can't use that against SQLCE, correct? Thanks! PS: Any good resources out there for using Sync, Linq, and WPF ALL TOGETHER? Tutorials, videos, etc?

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• Unexpected behavior with AudioQueueServices callback while recording audio

  - by rcw3

  I'm recording a continuous stream of data using AudioQueueServices. It is my understanding that the callback will only be called when the buffer fills with data. In practice, the first callback has a full buffer, the 2nd callback is 3/4 full, the 3rd callback is full, the 4th is 3/4 full, and so on. These buffers are 8000 packets (recording 8khz audio) - so I should be getting back 1s of audio to the callback each time. I've confirmed that my audio queue buffer size is correct (and is somewhat confirmed by the behavior). What am I doing wrong? Should I be doing something in the AudioQueueNewInput with a different RunLoop? I tried but this didn't seem to make a difference... By the way, if I run in the debugger, each callback is full with 8000 samples - making me think this is a threading / timing thing.

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• What are the use cases for closures/callback functions in Javascript?

  - by Christopher Altman

  I was listening to Crockford's talk on Javascript closures and am convinced of the benefit of information hiding, but I do not have a firm understanding of when to use callback functions. It is mostly a true statement that a person could accomplish the same functionality with or without callbacks. As someone who is writing code, what heuristics or cues should I keep in mind when determining when to use callbacks/closures? I am not looking for the blanket statement 'Closures make more secure code', rather a list of practical examples or rules of thumb for when callbacks are the right idea. Crockford's Presentation: http://www.yuiblog.com/blog/2010/04/08/video-crockonjs-5/

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• security issue of Linux sudo command?

  - by George2

  Hello everyone, 1. I am using Red Hat Enterprise 5 Linux box. I find if a user is in /etc/sudoers file, then if the user run command with sudo, the user will run this command with root privilege (without knowing root password, the user runs sudo only need to input the user's own password in order to run a command with sudo). Is that correct understanding? 2. If yes, then is it a security hole? Since users other than root could run with root privilege? thanks in advance, George

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• SQLCLR using the wrong version of the .NET Framework

  - by Tobias Rundbom

  During a recent restart of our development server the SQL Server started using .NET 4.0 for the SQLCLR. This means that nothing using the CLR in SQL works, or at least that's my understanding by reading these sources: http://software.intel.com/en-us/blogs/2009/10/16/sql-server-2008-sqlclr-net-framework-version/ www.sqlskills.com/BLOGS/BOBB/post/On-SQL-Server-and-NET-40.aspx All we get are error messages of this type: Msg 6517, Level 16, State 1, Line 1 Failed to create AppDomain "xxx.dbo[ddl].3". Method's type signature is not Interop compatible. Does anyone know how to solve this or how we can force SQL Server CLR to use an earlier version of the Framework?

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• Can I redistribute Phing with non-free software?

  - by Matt1776

  I am having trouble understanding the terms of the LGPL in light of a program that is not written in C or C++. They speak of libraries being linked and 'derivitive' works. If I were to package a php program and sell it, but within the program the deployment mechanism used the phing package (full up with the entire contents as is and un modified) - would I be violating the terms of the LGPL? For example, If this was a C program that was compiled by linking the phing 'library' then the answer would be easier, it is a derivitive work and therefore unless released under the GPL will not be considered free and also a violation. But this situation is different. I am not linking and not producing a derivitive, i am simply using phing as a deployment tool to move files around and set up the enviornment. Can someone shed some light? Thank you!

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• How do functional programming languages work?

  - by eSKay

  I was just reading this excellent post, and got some better understanding of what exactly object oriented programming is, how Java implements it in one extreme manner, and how functional programming languages are a contrast. What I was thinking is this: if functional programming languages cannot save any state, how do they do some simple stuff like reading input from a user (I mean how do they "store" it), or storing any data for that matter? For example - how would this simple C thing translate to any functional programming language, for example haskell? #include<stdio.h> int main() { int no; scanf("%d",&no); return 0; }

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• Explain Python extensions multithreading

  - by Checkers

  Python interpreter has a Global Interpreter Lock, and it is my understanding that extensions must acquire it in a multi-threaded environment. But Boost.Python HOWTO page says the extension function must release the GIL and reacquire it on exit. I want to resist temptation to guess here, so I would like to know what should be GIL locking patterns in the following scenarios: Extension is called from python (presumably running in a python thread). And extension's background thread calls back into Py_* functions. And a final question is, why the linked document says the GIL should be released and re-acquired?

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• Dns.GetHostEntry returns multiple IP addresses

  - by spender

  This question probably highlights a lack of understanding of networking principals on my part, rather than a programming issue. I'm doing a lookup on a hostname using Dns.GetHostEntry This returns an IPHostEntry to me, which has an AddressList property which is an array of IPAddress. I always thought there is a 1 to 1 mapping between hostname and IP, but I'm finding that in some cases I get back several IPAddress(es) for the same host. This is a surprise to me. Which part of domain name resolution do I not understand?

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• accessing $_SESSION when using file_get_contents in PHP

  - by hairdresser-101

  I am basic - intermediate developer using php and am a little stumped as to what I have found. I need some help in understanding how to alleviate this issue: I have a page called send.email.php which sends an email - pretty simple stuff - I pass an order id, it creates job request and sends it out. This works fine when used in the context I developed it (Use javascript to make an AJAX call to the URL and pass the order_id as a query parameter) I am now trying to reuse the exact same page in another application however I am calling it using php file_get_contents($base_url.'admin/send.email.php?order_id='.$order_id). When I call the page this way, the $_SESSION array is empty isempty() = 1. Is this because I am initiating a new session using file_get_contents and the values I stored in the $_SESSION on login are not available to me within there? Any help? Thanks

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• help converting sql to linq expression with count

  - by Philip

  I am trying to convert the following SQL into a LINQ expression SELECT COUNT(ID) AS Count, MyCode FROM dbo.Archive WHERE DateSent=@DateStartMonth AND DateSent<=@DateEndMonth GROUP BY MyCode and I have been trying to follow this webpage as an example http://stackoverflow.com/questions/606124/converting-sql-containing-top-count-group-and-order-to-linq-2-entities I got this so far but I am stuck on understanding the new part var res=(from p in db.Archives where (p.DateSent>= dateStartMonth) && (p.DateSent< dateToday) group p by p.MyCode into g select new { ??????MyCode = g.something?, MonthlyCount= g.Count() }); Thanks in advance for helping greatly appreciated Philip

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• Building Visual studio like application, need inputs..

  - by akjoshi

  Hi, I am working on a Visual studio like application i.e. hava a tolbox, an editor and property grid similar to VS. ser can drag and drop the controls(custom and third party) to the editor window and perform operations like resize, move, align, group etc.; Properties of that control needs to be displayed in property grid and user can update them from there. As per my current understanding I will have to extend the Canvas to create my own editor and and Interface for controls which it supports; Each supported control will have to implemnt this interface so that it can be placed in our editor. Something similar to this - http://www.codeproject.com/KB/WPF/WPFDiagramDesigner_Part4.aspx Looking forward for any kind of help, comment or links.

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• Why is thread local storage so slow?

  - by dsimcha

  I'm working on a custom mark-release style memory allocator for the D programming language that works by allocating from thread-local regions. It seems that the thread local storage bottleneck is causing a huge (~50%) slowdown in allocating memory from these regions compared to an otherwise identical single threaded version of the code, even after designing my code to have only one TLS lookup per allocation/deallocation. This is based on allocating/freeing memory a large number of times in a loop, and I'm trying to figure out if it's an artifact of my benchmarking method. My understanding is that thread local storage should basically just involve accessing something through an extra layer of indirection, similar to accessing a variable via a pointer. Is this incorrect? How much overhead does thread-local storage typically have? Note: Although I mention D, I'm also interested in general answers that aren't specific to D, since D's implementation of thread-local storage will likely improve if it is slower than the best implementations.

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• MIT vs. BSD vs. Dual License

  - by ryanve

  My understanding is that: MIT-licensed projects can be used/redistributed in BSD-licensed projects. BSD-licensed projects can be used/redistributed in MIT-licensed projects. The MIT and the BSD 2-clause licenses are essentially identical. BSD 3-clause = BSD 2-clause + the "no endorsement" clause Issuing a dual license allows users to choose from those licenses—not be bound to both. If all of the above is correct, then what is the point of using a dual MIT/BSD license? Even if the BSD refers to the 3-clause version, then can't a user legally choose to only abide by the MIT license? It seems that if you really want the "no endorsement" clause to apply then you have to license it as just BSD (not dual). If you don't care about the "no endorsement" clause, then MIT alone is sufficient and MIT/BSD is redundant. Similarly, since the MIT and BSD licenses are both "GPL-compatible" and can be redistributed in GPL-licensed projects, then dual licensing MIT/GPL also seems redundant.

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• Base class for windows service

  - by user187020

  My new project has a design in which there are number windows services for performing different tasks. I have been given a task to create base class from which all of the windows service will inherit. This base class will perform common functions like creating instances of other windows services by iterating through the config file (may be like Activator.CreateInstance), do event logging on onStart, onStop etc. and may contain some more functionality. Before I start developing stuff, wondering if there is any pattern already in place or someone has good understanding of how to implement this kind of functionality. Any help appreciated.

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• Why does MSBuild fail from the command line where VS2008 succeeds?

  - by sundeep

  I have an ASP.NET solution that builds just fine from within VS2008. However , it fails when i do this : MSBUILD.exe c:\path-to-sln It fails with a CS0006 error ("Metadata file 'dll_name' could not be found"). It also fails when I try with a .csproj of a project within the solution. What is VS2008 doing that MSBuild is missing ? It is my understanding that VS knows about inter assembly dependencies that MSBuild cant. Is there any way I can inform MSBuild of these? (I need MSBuild to work from the command line because I am calling it from an MSBuild-Task from within CruiseControl.Net.) Thanks in Advance. :3) (I have looked at http://stackoverflow.com/questions/280559/how-to-get-cmd-line-build-command-for-vs-solution , but still dont get it)

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• Computing orientation of a square and displaying an object with the same orientation

  - by Robin

  Hi, I wrote an application which detects a square within an image. To give you a good understanding of how such an image containing such a square, in this case a marker, could look like: What I get, after the detection, are the coordinates of the four corners of my marker. Now I don't know how to display an object on my marker. The object should have the same rotation/angle/direction as the marker. Are there any papers on how to achieve that, any algorithms that I can use that proofed to be pretty solid/working? It doesn't need to be a working solution, it could be a simple description on how to achieve that or something similar. If you point me at a library or something, it should work under linux, windows is not needed but would be great in case I need to port the application at some point. I already looked at the ARToolkit but they you camera parameter files and more complex matrices while I only got the four corner points and a single image instead of a whole video / camera stream.

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