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  • Collision Resolution

    - by CiscoIPPhone
    I know quite well how to check for collisions, but I don't know how to handle the collision in a good way. Simplified, if two objects collide I use some calculations to change the velocity direction. If I don't move the two objects they will still overlap and if the velocity is not big enough they will still collide after next update. This can cause objects to get stuck in each other. But what if I try to move the two objects so they do not overlap. This sounds like a good idea but I have realised that if there is more than two objects this becomes very complicated. What if I move the two objects and one of them collides with other objects so I have to move them too and they may collide with walls etc. I have a top down 2D game in mind but I don't think that has much to do with it. How are collisions usually handled? This question is asked on behalf of Wooh

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  • If using a bootable Ubuntu USB drive, can I use the internal hard drive as a temporary download and

    - by NoCatharsis
    I am new to Linux, so this is probably a basic problem... My flash drive is only 4GB in size and that is not enough to hold kernel and other package updates, even if only temporary. I am actually using Kubuntu, but I don't think this would change the nature of the question...? I would just like to be able to set my download directory to the internal drive to download the upgrades, then replace the old versions installed on the USB. Of course I have no use for keeping the older versions, so would I also have to manually remove those after upgrading?

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  • What is the default value for Empty Temporary Internet Files when browser is closed in IE8?

    - by schellack
    We have four different machines that all have "Empty Temporary Internet Files when browser is closed" set to true (checked) in IE8's Internet Options (located under the Security section in the Advanced tab). No one remembers checking that checkbox to turn on the setting. What is the default value supposed to be? I'm specifically interested in Windows 7 and Windows XP. I have run rsop.msc on one of the corporate machines—3 of the 4 are members of a corporate network/domain—and see this under User Configuration, which makes the current scenario seem even stranger: The Local Group Policy Editor (gpedit.msc) also shows the Configure Delete Browsing History on exit setting to be Not configured (under Computer ConfigurationAdministrative TemplatesWindows ComponentsInternet ExplorerDelete Browsing History).

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  • Windows always logs in to temporary profile (thinks it is in D while it is in C)

    - by asdf
    I have Windows on C: Disk 0 Partition 1 When I start it works fine until the login screen. When I log in, it starts to display "preparing your desktop.." and logs in to a temporary profile. I have to run explorer.exe manually then using task manager. If I execute %SystemRoot% it tells me that Windows could not find D:\Windows. (while Windows is in C:) I have no such drive as D then why Windows is thinking it is in D? I've tried this Bootmanager is missing but it did not work. Bootrec /ScanOS from Windows setup gives me Total identified Windows installations: 0 Also note that Windows Setup correctly thinks windows is installed on C but Windows itself thinks it is on D.

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  • How do I create statistics to make ‘small’ objects appear ‘large’ to the Optmizer?

    - by Maria Colgan
    I recently spoke with a customer who has a development environment that is a tiny fraction of the size of their production environment. His team has been tasked with identifying problem SQL statements in this development environment before new code is released into production. The problem is the objects in the development environment are so small, the execution plans selected in the development environment rarely reflects what actually happens in production. To ensure the development environment accurately reflects production, in the eyes of the Optimizer, the statistics used in the development environment must be the same as the statistics used in production. This can be achieved by exporting the statistics from production and import them into the development environment. Even though the underlying objects are a fraction of the size of production, the Optimizer will see them as the same size and treat them the same way as it would in production. Below are the necessary steps to achieve this in their environment. I am using the SH sample schema as the application schema who's statistics we want to move from production to development. Step 1. Create a staging table, in the production environment, where the statistics can be stored Step 2. Export the statistics for the application schema, from the data dictionary in production, into the staging table Step 3. Create an Oracle directory on the production system where the export of the staging table will reside and grant the SH user the necessary privileges on it. Step 4. Export the staging table from production using data pump export Step 5. Copy the dump file containing the stating table from production to development Step 6. Create an Oracle directory on the development system where the export of the staging table resides and grant the SH user the necessary privileges on it.  Step 7. Import the staging table into the development environment using data pump import Step 8. Import the statistics from the staging table into the dictionary in the development environment. You can get a copy of the script I used to generate this post here. +Maria Colgan

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  • How can I author objects with perspective that fit into a tile-based map but span multiple tiles?

    - by Growler
    I'm creating a tilemap city and trying to figure out the most efficient way to create unique building scenes. The trick is, I need to maintain a sort of 2D, almost-top-down perspective, which is hard to do with buildings or large objects that span multiple tiles. I've tried doing three buildings at a time, and mixing and matching the base layer and colors, like this: This creates a weird overlapping effect, and also doesn't seem that efficient from a production standpoint. But it was the best way to have shadows appear correctly on the neighboring buildings. I'm wondering if modular buildings would be the way to go? That way I can mix and match any set of buildings together as tiles: I guess I would have to risk some perspective and shadowing to get the buildings to align correctly. What sort of authoring process could I use to allow me to create a variety of buildings (or other objects) that maintain this perspective while spanning multiple tiles worth of screen space? Would you recommend creating blank buildings, and then affixing art overlays as necessary to make the buildings unique? Or should they be directly part of the building tile (for example, create a separate tileset of buildings signs and colorings)?

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  • How to REALLY start thinking in terms of objects?

    - by Mr Grieves
    I work with a team of developers who all have several years of experience with languages such as C# and Java. Most of them are young enough to have been shown OOP as a standard way to develop software in university and are very comfortable with concepts such as inheritance, abstraction, encapsulation and polymorphism. Yet, many of them, and I have to include myself, still tend to create classes which are meant to be used in a very functional fashion. The resulting software is often several smaller classes which correctly represent business objects which get passed through larger classes which only supply ways to modify and use those objects (functions). Large complex difficult-to-maintain classes named Manager are usually the result of such behaviour. I can see two theoretical reasons why people might write this type of code: It's easy to start thinking of everything in terms of the database Deep down, for me, a computer handling a web request feels more like a functional operation than an object oriented operation when you think about Request Handlers, Threads, Processes, CPU Cores and CPU operations... I want source code which is easy to read and easy to modify. I have seen excellent examples of OO code which meet these objectives. How can I start writing code like this? How I can I really start thinking in an object oriented fashion? How can I share such a mentality with my colleagues?

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  • Are there legitimate reasons for returning exception objects instead of throwing them?

    - by stakx
    This question is intended to apply to any OO programming language that supports exception handling; I am using C# for illustrative purposes only. Exceptions are usually intended to be raised when an problem arises that the code cannot immediately handle, and then to be caught in a catch clause in a different location (usually an outer stack frame). Q: Are there any legitimate situations where exceptions are not thrown and caught, but simply returned from a method and then passed around as error objects? This question came up for me because .NET 4's System.IObserver<T>.OnError method suggests just that: exceptions being passed around as error objects. Let's look at another scenario, validation. Let's say I am following conventional wisdom, and that I am therefore distinguishing between an error object type IValidationError and a separate exception type ValidationException that is used to report unexpected errors: partial interface IValidationError { } abstract partial class ValidationException : System.Exception { public abstract IValidationError[] ValidationErrors { get; } } (The System.Component.DataAnnotations namespace does something quite similar.) These types could be employed as follows: partial interface IFoo { } // an immutable type partial interface IFooBuilder // mutable counterpart to prepare instances of above type { bool IsValid(out IValidationError[] validationErrors); // true if no validation error occurs IFoo Build(); // throws ValidationException if !IsValid(…) } Now I am wondering, could I not simplify the above to this: partial class ValidationError : System.Exception { } // = IValidationError + ValidationException partial interface IFoo { } // (unchanged) partial interface IFooBuilder { bool IsValid(out ValidationError[] validationErrors); IFoo Build(); // may throw ValidationError or sth. like AggregateException<ValidationError> } Q: What are the advantages and disadvantages of these two differing approaches?

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  • How are objects modelled in a functional programming language?

    - by Giorgio
    In an answer to this question (written by Pete) there are some considerations about OOP versus FP. In particular, it is suggested that FP languages are not very suitable for modelling (persistent) objects that have an identity and a mutable state. I was wondering if this is true or, in other words, how one would model objects in a functional programming language. From my basic knowledge of Haskell I thought that one could use monads in some way, but I really do not know enough on this topic to come up with a clear answer. So, how are entities with an identity and a mutable persistent state normally modelled in a functional language? EDIT Here are some further details to clarify what I have in mind. Take a typical Java application in which I can (1) read a record from a database table into a Java object, (2) modify the object in different ways, (3) save the modified object to the database. How would this be implemented e.g. in Haskell? I would initially read the record into a record value (defined by a data definition), perform different transformations by applying functions to this initial value (each intermediate value is a new, modified copy of the original record) and then write the final record value to the database. Is this all there is to it? How can I ensure that at each moment in time only one copy of the record is valid / accessible? One does not want to have different immutable values representing different snapshots of the same object to be accessible at the same time.

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  • What is an efficient algorithm for randomly assigning a pool of objects to a parent using specific rules

    - by maple_shaft
    I need some expert answers to help me determine the most efficient algorithm in this scenario. Consider the following data structures: type B { A parent; } type A { set<B> children; integer minimumChildrenAllowed; integer maximumChildrenAllowed; } I have a situation where I need to fetch all the orphan children (there could be hundreds of thousands of these) and assign them RANDOMLY to A type parents based on the following rules. At the end of the job, there should be no orphans left At the end of the job, no object A should have less children than its predesignated minimum. At the end of the job, no object A should have more children than its predesignated maximum. If we run out of A objects then we should create a new A with default values for minimum and maximum and assign remaining orphans to these objects. The distribution of children should be as evenly distributed as possible. There may already be some children assigned to A before the job starts. I was toying with how to do this but I am afraid that I would just end up looping across the parents sorted from smallest to largest, and then grab an orphan for each parent. I was wondering if there is a more efficient way to handle this?

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  • SOA Suite Integration: Part 1: Building a Web Service

    - by Anthony Shorten
    Over the next few weeks I will be posting blog entries outlying the SOA Suite integration of the Oracle Utilities Application Framework. This will illustrate how easy it is to integrate by providing some samples. I will use a consistent set of features as examples. The examples will be simple and while will not illustrate ALL the possibilities it will illustrate the relative ease of integration. Think of them as a foundation. You can obviously build upon them. Now, to ease a few customers minds, this series will certainly feature the latest version of SOA Suite and the latest version of Oracle Utilities Application Framework but the principles will apply to past versions of both those products. So if you have Oracle SOA Suite 10g or are a customer of Oracle Utilities Application Framework V2.1 or above most of what I will show you will work with those versions. It is just easier in Oracle SOA Suite 11g and Oracle Utilities Application Framework V4.x. This first posting will not feature SOA Suite at all but concentrate on the capability for the Oracle Utilities Application Framework to create Web Services you can use for integration. The XML Application Integration (XAI) component of the Oracle Utilities Application Framework allows product objects to be exposed as XML based transactions or as Web Services (or both). XAI was written before Web Services became fashionable and has allowed customers of our products to provide a consistent interface into and out of our product line. XAI has been enhanced over the last few years to take advantages of the maturing landscape of Web Services in the market place to a point where it now easier to integrate to SOA infrastructure. There are a number of object types that can be exposed as Web Services: Maintenance Objects – These are the lowest level objects that can be exposed as Web Services. Customers of past versions of the product will be familiar with XAI services based upon Maintenance Objects as they used to be the only method of generating Web Services. These are still supported for background compatibility but are starting to become less popular as they were strict in their structure and were solely attribute based. To generate Maintenance Object based Web Services definition you need to use the XAI Schema Editor component. Business Objects – In Oracle Utilities Application Framework V2.1 we introduced the concept of Business Objects. These are site or industry specific objects that are based upon Maintenance Objects. These allow sites to respecify, in configuration, the structure and elements of a Maintenance Object and other Business Objects (they are true objects with support for inheritance, polymorphism, encapsulation etc.). These can be exposed as Web Services. Business Services – As with Business Objects, we introduced Business Services in Oracle Utilities Application Framework V2.1 which allowed applications services and query zones to be expressed as custom services. These can then be exposed as Web Services via the Business Service definition. Service Scripts - As with Business Objects and Business Services, we introduced Service Scripts in Oracle Utilities Application Framework V2.1. These allow services and/objects to be combined into complex objects or simply expose common routines as callable scripts. These can also be defined as Web Services. For the purpose of this series we will restrict ourselves to Business Objects. The techniques can apply to any of the objects discussed above. Now, lets get to the important bit of this blog post, the creation of a Web Service. To build a Business Object, you first logon to the product and navigate to the Administration Menu by selecting the Admin Menu from the Menu action on left top of the screen (next to Home). A popup menu will appear with the menu’s available. If you do not see the Admin menu then you do not have authority to use it. Here is an example: Navigate to the B menu and select the + symbol next to the Business Object menu item. This indicates that you want to ADD a new Business Object. This menu will appear if you are running Alphabetic mode in your installation (I almost forgot that point). You will be presented with the Business Object maintenance screen. You will fill out the following on the first tab (at a minimum): Business Object – The name of the Business Object. Typically you will make it descriptive and also prefix with CM to denote it as a customization (you can easily find it if you prefix it). As I running this on my personal copy of the product I will use my initials as the prefix and call the sample Web Service “AS-User”. Description – A short description of the object to tell others what it is used for. For my example, I will use “Anthony Shorten’s User Object”. Detailed Description – You can add a long description to help other developers understand your object. I am just going to specify “Anthony Shorten’s Test Object for SOA Suite Integration”. Maintenance Object – As this Business Service is going to be based upon a Maintenance Object I will specify the desired Maintenance Object. In this example, I have decided to use the Framework object USER. Now, I chose this for a number of reasons. It is meaningful, simple and is across all our product lines. I could choose ANY maintenance object I wished to expose (including any custom ones, if I had them). Parent Business Object – If I was not using a Maintenance Object but building a child Business Object against another Business Object, then I would specify the Parent Business Object here. I am not using Parent’s so I will leave this blank. You either use Parent Business Object or Maintenance Object not both. Application Service – Business Objects like other objects are subject to security. You can attach an Application Service to an object to specify which groups of users (remember services are attached to user groups not users) have appropriate access to the object. I will use a default service provided with the product, F1-DFLTS ,as this is just a demonstration so I do not have to be too sophisticated about security. Instance Control – This allows the object to create instances in its objects. You can specify a Business Object purely to hold rules. I am being simple here so I will set it to Allow New Instances to allow the Business Object to be used to create, read, update and delete user records. The rest of the tab I will leave empty as I want this to be a very simple object. Other options allow lots of flexibility. The contents should look like this: Before saving your work, you need to navigate to the Schema tab and specify the contents of your object. I will save some time. When you create an object the schema will only contain the basic root elements of the object (in fact only the schema tag is visible). When you go to the Schema Tab, on the dashboard you will see a BO Schema zone with a solitary button. This will allow you to Generate the Schema for you from our metadata. Click on the Generate button to generate a basic schema from the metadata. You will now see a Schema with the element tags and references to the metadata of the Maintenance object (in the mapField attribute). I could spend a while outlining all the ways you can change the schema with defaults, formatting, tagging etc but the online help has plenty of great examples to illustrate this. You can use the Schema Tips zone in the for more details of the available customizations. Note: The tags are generated from the language pack you have installed. The sample is English so the tags are in English (which is the base language of all installations). If you are using a language pack then the tags will be generated in the language of the user that generated the object. At this point you can save your Business Object by pressing the Save action. At this point you have a basic Business Object based on the USER maintenance object ready for use but it is not defined as a Web Service yet. To do this you need to define the newly created Business Object as an XAI Inbound Service. The easiest and quickest way is to select + off the XAI Inbound Service off the context menu on the Business Object maintenance screen. This will prepopulate the service definition with the following: Adapter – This will be set to Business Adaptor. This indicates that the service is either Business Object, Business Service or Service Script based. Schema Type – Whether the object is a Business Object, Business Service or Service Script. In this case it is a Business Object. Schema Name – The name of the object. In this case it is the Business Object AS-User. Active – Set to Yes. This means the service is available upon startup automatically. You can enable and disable services as needed. Transaction Type – A default transaction type as this is Business Object Service. More about this in later postings. In our case we use the default Read. This means that if we only specify data and not a transaction type then the product will assume you want to issue a read against the object. You need to fill in the following: XAI Inbound Service – The name of the Web Service. Usually people use the same name as the underlying object , in the case of this example, but this can match your sites interfacing standards. By the way you can define multiple XAI Inbound Services/Web Services against the same object if you want. Description and Detail Description – Documentation for your Web Service. I just supplied some basic documentation for this demonstration. You can now save the service definition. Note: There are lots of other options on this screen that allow for behavior of your service to be specified. I will leave them blank for now. When you save the service you are issued with two new pieces of information. XAI Inbound Service Id is a randomly generated identifier used internally by the XAI Servlet. WSDL URL is the WSDL standard URL used for integration. We will take advantage of that in later posts. An example of the definition is shown below: Now you have defined the service but it will only be available when the next server restart or when you flush the data cache. XAI Inbound Services are cached for performance so the cache needs to be told of this new service. To refresh the cache you can use the Admin –> X –> XAI Command menu item. From the command dropdown select Refresh Registry and press Send Command. You will see an XML of the command sent to the server (the presence of the XML means it is finished). If you have an error around the authorization, then check your default user and password settings on the XAI Options menu item. Be careful with flushing the cache as the cache is shared (unless of course you are the only Web Service user on the system – In that case it only affects you). The Web Service is NOW available to be used. To perform a simple test of your new Web Service, navigate to the Admin –> X –> XAI Submission menu item. You will see an open XML request tab. You need to type in the request XML you want to test in the Main tab. The first tag is the XAI Inbound Service Name and the elements are as per your schema (minus the schema tag itself as that is only used internally). My example is as follows (I want to return the details of user SYSUSER) – Remember to close tags. Hitting the Save button will issue the XML and return the response according to the Business Object schema. Now before you panic, you noticed that it did not ask for credentials. It propagates the online credentials to the service call on this function. You now have a Web Service you can use for integration. We will reuse this information in subsequent posts. The process I just described can be used for ANY object in the system you want to expose. This whole process at a minimum can take under a minute. Obviously I only showed the basics but you can at least get an appreciation of the ease of defining a Web Service (just by using a browser). The next posts now build upon this. Hope you enjoyed the post.

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  • Why am I getting a warning that windows is logging on with a temporary profile to run a task scheduler task?

    - by Dan C
    I am having a strange problem with the Windows Server 2008 Task Scheduler. I have to run a small command-line application every few minutes. This application just executes a quick web service call on the localhost and adds an entry to a log file; so it should not need anything special in terms of permissions. First, I created a new user account "my_scheduler" just for the task. This account is a member of the Users group (not sure what other settings I should turn on/off) and set it's password to not expire. I then create a task to run the application every few minutes. I set it to "Run whether user is logged on or not" and turned on "Do not store password. The task will only have access to local resources" (I did this since it's not hitting anything on the network. I did not turn on "Run with highest privileges" since it does not seem to need them. I set the schedule to "After triggered, repeat every 30 minutes for a duration of 1 day" and "Allow task to be run on demand" (no other settings enabled). However, I notice that in the Event Log, I see a bunch of these warnings whenever the task is run: "Windows cannot find the local profile and is logging you on with a temporary profile. Changes you make to this profile will be lost when you log off." Even though I get the warning, the task is executing (I see the log entries appearing). Another (possibly related) issue is that I also see that it's starting multiple copies of the task (within a few seconds of each other) even though it should only start one. This is also a big problem. Any idea how I can fix this? Thanks in advance, Dan

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  • Why are snapshots considered as temporary backups not real backups?

    - by Samselvaprabu
    I am using VMware ESXi. In our team we use to provide snapshots for long term backup. Then we faced issues like memory spillover and the server got hang up. I started reading in VMware knowledgebase articles and everywhere. Everywhere it was recommended not to have snapshots for a long time. Even VMware advised to keep snapshots for maximum of three days. But our team kept asking us to have at least two permanent snapshots (till deleting the VM). Sometimes we may use the VM for a year). one snapshot is for fresh machine state. (So when we complete testing an application, we will revert back to fresh state and install another application) (If I did not allow that, I may often need to host the VM.) Next snapshot for keeping the VM in some state (maybe they would have found an issue and keep that state for some time. Or they may install prerequisites for the application and keep the machine ready for testing.) Logically, their needs seems to be fair. But if I allow that, I am to permit them to hold the snapshots for long time. We are not using our VM as a mail server or database server. Why is keeping snapshots for long time having an adverse effect? Why are snapshots considered as temporary backups, not real backups?

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  • SQL SERVER – Find Referenced or Referencing Object in SQL Server using sys.sql_expression_dependencies

    - by pinaldave
    A very common question which I often receive are: How do I find all the tables used in a particular stored procedure? How do I know which stored procedures are using a particular table? Both are valid question but before we see the answer of this question – let us understand two small concepts – Referenced and Referencing. Here is the sample stored procedure. CREATE PROCEDURE mySP AS SELECT * FROM Sales.Customer GO Reference: The table Sales.Customer is the reference object as it is being referenced in the stored procedure mySP. Referencing: The stored procedure mySP is the referencing object as it is referencing Sales.Customer table. Now we know what is referencing and referenced object. Let us run following queries. I am using AdventureWorks2012 as a sample database. If you do not have SQL Server 2012 here is the way to get SQL Server 2012 AdventureWorks database. Find Referecing Objects of a particular object Here we are finding all the objects which are using table Customer in their object definitions (regardless of the schema). USE AdventureWorks GO SELECT referencing_schema_name = SCHEMA_NAME(o.SCHEMA_ID), referencing_object_name = o.name, referencing_object_type_desc = o.type_desc, referenced_schema_name, referenced_object_name = referenced_entity_name, referenced_object_type_desc = o1.type_desc, referenced_server_name, referenced_database_name --,sed.* -- Uncomment for all the columns FROM sys.sql_expression_dependencies sed INNER JOIN sys.objects o ON sed.referencing_id = o.[object_id] LEFT OUTER JOIN sys.objects o1 ON sed.referenced_id = o1.[object_id] WHERE referenced_entity_name = 'Customer' The above query will return all the objects which are referencing the table Customer. Find Referenced Objects of a particular object Here we are finding all the objects which are used in the view table vIndividualCustomer. USE AdventureWorks GO SELECT referencing_schema_name = SCHEMA_NAME(o.SCHEMA_ID), referencing_object_name = o.name, referencing_object_type_desc = o.type_desc, referenced_schema_name, referenced_object_name = referenced_entity_name, referenced_object_type_desc = o1.type_desc, referenced_server_name, referenced_database_name --,sed.* -- Uncomment for all the columns FROM sys.sql_expression_dependencies sed INNER JOIN sys.objects o ON sed.referencing_id = o.[object_id] LEFT OUTER JOIN sys.objects o1 ON sed.referenced_id = o1.[object_id] WHERE o.name = 'vIndividualCustomer' The above query will return all the objects which are referencing the table Customer. I am just glad to write above query. There are more to write to this subject. In future blog post I will write more in depth about other DMV which also aids in finding referenced data. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL DMV, SQL Query, SQL Server, SQL Tips and Tricks, SQL Utility, T SQL, Technology

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  • JavaScript or PHP based WYSIWYG vector based image editor

    - by Jeroen Pluimers
    For a PHP based site of a client, I'm looking for a vector based image editor that allows: end user creation of vectored images consisting of objects supports upload of bitmap images to be used as objects inside the vector image supports adding text objects to add to the vector image, and change properties (font name, font style, font size) of the text objects preferably supports layering or grouping of objects inside the vector image integrates nicely with a PHP based site (so a PHP or JavaScript library is preferred) can store the vector image in SVG, EPS or PDF Both commercial and FOSS solutions are OK. Any idea where to find such a library? --jeroen

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  • Scene Graph as Object Container?

    - by Bunkai.Satori
    Scene graph contains game nodes representing game objects. At a first glance, it might seem practical to use Scene Graph as physical container for in game objects, instead of std::vector< for example. My question is, is it practical to use Scene Graph to contain the game objects, or should it be used only to define scene objects/nodes linkages, while keepig the objects stored in separate container, such as std::vector<?

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  • F# Objects &ndash; Integrating with the other .Net Languages &ndash; Part 1

    - by MarkPearl
    In the next few blog posts I am going to explore objects in F#. Up to now, my dabbling in F# has really been a few liners and while I haven’t reached the point where F# is my language of preference – I am already seeing the benefits of the language when solving certain types of programming problems. For me I believe that the F# language will be used in a silo like architecture and that the real benefit of having F# under your belt is so that you can solve problems that F# lends itself towards and then interact with other .Net languages in doing the rest. When I was still very new to the F# language I did the following post covering how to get F# & C# to talk to each other. Today I am going to use a similar approach to demonstrate the structure of F# objects when inter-operating with other languages. Lets start with an empty F# class … type Person() = class end   Very simple, and all we really have done is declared an object that has nothing in it. We could if we wanted to make an object that takes a constructor with parameters… the code for this would look something like this… type Person =     {         Firstname : string         Lastname : string     }   What’s interesting about this syntax is when you try and interop with this object from another .Net language like C# - you would see the following…   Not only has a constructor been created that accepts two parameters, but Firstname and Lastname are also exposed on the object. Now it’s important to keep in mind that value holders in F# are immutable by default, so you would not be able to change the value of Firstname after the construction of the object – in C# terms it has been set to readonly. One could however explicitly state that the value holders were mutable, which would then allow you to change the values after the actual creation of the object. type Person = { mutable Firstname : string mutable Lastname : string }   Something that bugged me for a while was what if I wanted to have an F# object that requires values in its constructor, but does not expose them as part of the object. After bashing my head for a few moments I came up with the following syntax – which achieves this result. type Person(Firstname : string, Lastname : string) = member v.Fullname = Firstname + " " + Lastname What I haven’t figured out yet is what is the difference between the () & {} brackets when declaring an object.

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  • Representing complex object dependencies

    - by max
    I have several classes with a reasonably complex (but acyclic) dependency graph. All the dependencies are of the form: class X instance contains an attribute of class Y. All such attributes are set during initialization and never changed again. Each class' constructor has just a couple parameters, and each object knows the proper parameters to pass to the constructors of the objects it contains. class Outer is at the top of the dependency hierarchy, i.e., no class depends on it. Currently, the UI layer only creates an Outer instance; the parameters for Outer constructor are derived from the user input. Of course, Outer in the process of initialization, creates the objects it needs, which in turn create the objects they need, and so on. The new development is that the a user who knows the dependency graph may want to reach deep into it, and set the values of some of the arguments passed to constructors of the inner classes (essentially overriding the values used currently). How should I change the design to support this? I could keep the current approach where all the inner classes are created by the classes that need them. In this case, the information about "user overrides" would need to be passed to Outer class' constructor in some complex user_overrides structure. Perhaps user_overrides could be the full logical representation of the dependency graph, with the overrides attached to the appropriate edges. Outer class would pass user_overrides to every object it creates, and they would do the same. Each object, before initializing lower level objects, will find its location in that graph and check if the user requested an override to any of the constructor arguments. Alternatively, I could rewrite all the objects' constructors to take as parameters the full objects they require. Thus, the creation of all the inner objects would be moved outside the whole hierarchy, into a new controller layer that lies between Outer and UI layer. The controller layer would essentially traverse the dependency graph from the bottom, creating all the objects as it goes. The controller layer would have to ask the higher-level objects for parameter values for the lower-level objects whenever the relevant parameter isn't provided by the user. Neither approach looks terribly simple. Is there any other approach? Has this problem come up enough in the past to have a pattern that I can read about? I'm using Python, but I don't think it matters much at the design level.

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  • Translating multiple objects in GUI based on average position?

    - by user1423893
    I use this method to move a single object in 3D space, it accounts for a local offset based on where the cursor ray hits the widget and the center of the widget. var cursorRay = cursor.Ray; Vector3 goalPosition = translationWidget.GoalPosition; Vector3 position = cursorRay.Origin + cursorRay.Direction * grabDistance; // Constrain object movement based on selected axis switch (translationWidget.AxisSelected) { case AxisSelected.All: goalPosition = position; break; case AxisSelected.None: break; case AxisSelected.X: goalPosition.X = position.X; break; case AxisSelected.Y: goalPosition.Y = position.Y; break; case AxisSelected.Z: goalPosition.Z = position.Z; break; } translationWidget.GoalPosition = goalPosition; Vector3 p = goalPosition - translationWidget.LocalOffset; objectSelected.Position = p; I would like to move multiple objects based on the same principle and using a widget which is located at the average position of all the objects currently selected. I thought that I would have to translate each object based on their offset from the average point and then include the local offset. var cursorRay = cursor.Ray; Vector3 goalPosition = translationWidget.GoalPosition; Vector3 position = cursorRay.Origin + cursorRay.Direction * grabDistance; // Constrain object movement based on selected axis switch (translationWidget.AxisSelected) { case AxisSelected.All: goalPosition = position; break; case AxisSelected.None: break; case AxisSelected.X: goalPosition.X = position.X; break; case AxisSelected.Y: goalPosition.Y = position.Y; break; case AxisSelected.Z: goalPosition.Z = position.Z; break; } translationWidget.GoalPosition = goalPosition; Vector3 p = goalPosition - translationWidget.LocalOffset; int numSelectedObjects = objectSelectedList.Count; for (int i = 0; i < numSelectedObjects; ++i) { objectSelectedList[i].Position = (objectSelectedList[i].Position - translationWidget.Position) + p; } This doesn't work as the object starts shaking, which I think is because I haven't accounted for the new offset correctly. Where have I gone wrong?

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  • How to find collision detection side between two objects?

    - by user2362369
    I am using box2D and I have two objects, one is bouncy ball and the other one is block. I'd like to find which side of the block is collided with, so I can only make the ball bounce when it hits the top. I tried to implement many things like fixture data and by detecting position, using manifold but not get the accurate result. I also tried to calculate distance between two object but all went wrong.

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  • Significant amount of the time, I can't think of a reason to have an object instead of a static class. Do objects have more benefits than I think?

    - by Prog
    I understand the concept of an object, and as a Java programmer I feel the OO paradigm comes rather naturally to me in practice. However recently I found myself thinking: Wait a second, what are actually the practical benefits of using an object over using a static class (with proper encapsulation and OO practices)? I could think of two benefits of using an object (both significant and powerful): Polymorphism: allows you to swap functionality dynamically and flexibly during runtime. Also allows to add new functionality 'parts' and alternatives to the system easily. For example if there's a Car class designed to work with Engine objects, and you want to add a new Engine to the system that the Car can use, you can create a new Engine subclass and simply pass an object of this class into the Car object, without having to change anything about Car. And you can decide to do so during runtime. Being able to 'pass functionality around': you can pass an object around the system dynamically. But are there any more advantages to objects over static classes? Often when I add new 'parts' to a system, I do so by creating a new class and instantiating objects from it. But recently when I stopped and thought about it, I realized that a static class would do just the same as an object, in a lot of the places where I normally use an object. For example, I'm working on adding a save/load-file mechanism to my app. With an object, the calling line of code will look like this: Thing thing = fileLoader.load(file); With a static class, it would look like this: Thing thing = FileLoader.load(file); What's the difference? Fairly often I just can't think of a reason to instantiate an object when a plain-old static-class would act just the same. But in OO systems, static classes are fairly rare. So I must be missing something. Are there any more advantages to objects other from the two that I listed? Please explain.

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  • In C# should I reuse a function / property parameter to compute temp result or create a temporary v

    - by Hamish Grubijan
    The example below may not be problematic as is, but it should be enough to illustrate a point. Imagine that there is a lot more work than trimming going on. public string Thingy { set { // I guess we can throw a null reference exception here on null. value = value.Trim(); // Well, imagine that there is so much processing to do this.thingy = value; // That this.thingy = value.Trim() would not fit on one line ... So, if the assignment has to take two lines, then I either have to abusereuse the parameter, or create a temporary variable. I am not a big fan of temporary variables. On the other hand, I am not a fan of convoluted code. I did not include an example where a function is involved, but I am sure you can imagine it. One concern I have is if a function accepted a string and the parameter was "abused", and then someone changed the signature to ref in both places - this ought to mess things up, but ... who would knowingly make such a change if it already worked without a ref? Seems like it is their responsibility in this case. If I mess with the value of value, am I doing something non-trivial under the hood? If you think that both approaches are acceptable, then which do you prefer and why? Thanks.

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  • In C# should I reuse a function / property parameter to compute cleaner temporary value or create a

    - by Hamish Grubijan
    The example below may not be problematic as is, but it should be enough to illustrate a point. Imagine that there is a lot more work than trimming going on. public string Thingy { set { // I guess we can throw a null reference exception here on null. value = value.Trim(); // Well, imagine that there is so much processing to do this.thingy = value; // That this.thingy = value.Trim() would not fit on one line ... So, if the assignment has to take two lines, then I either have to abusereuse the parameter, or create a temporary variable. I am not a big fan of temporary variables. On the other hand, I am not a fan of convoluted code. I did not include an example where a function is involved, but I am sure you can imagine it. One concern I have is if a function accepted a string and the parameter was "abused", and then someone changed the signature to ref in both places - this ought to mess things up, but ... who would knowingly make such a change if it already worked without a ref? Seems like it is their responsibility in this case. If I mess with the value of value, am I doing something non-trivial under the hood? If you think that both approaches are acceptable, then which do you prefer and why? Thanks.

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