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• Low-level game engine renderer design

  - by Mark Ingram

  I'm piecing together the beginnings of an extremely basic engine which will let me draw arbitrary objects (SceneObject). I've got to the point where I'm creating a few sensible sounding classes, but as this is my first outing into game engines, I've got the feeling I'm overlooking things. I'm familiar with compartmentalising larger portions of the code so that individual sub-systems don't overly interact with each other, but I'm thinking more of the low-level stuff, starting from vertices working up. So if I have a Vertex class, I can combine that with a list of indices to make a Mesh class. How does the engine determine identical meshes for objects? Or is that left to the level designer? Once we have a Mesh, that can be contained in the SceneObject class. And a list of SceneObject can be placed into the Scene to be drawn. Right now I'm only using OpenGL, but I'm aware that I don't want to be tying OpenGL calls right in to base classes (such as updating the vertices in the Mesh, I don't want to be calling glBufferData etc). Are there any good resources that discuss these issues? Are there any "common" heirachies which should be used?

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• Algorithm to reduce calls to mapping API

  - by aidan

  A random distribution of points lies on a map. This data lies behind an API, and I want to grab the complete set of points within a given bounding box. I can query the API with the bounding box and the API will return the set of points that fall within that box. The problem is that the API will limit the result set to 10 items, with no pagination and no indication if there are more points that have been omitted. So I made a recursive algorithm that takes a bounding box and requests the points that lie within it. If the result set is exactly 10 items, then I split the bounding box into four quadrants and recurse. It works fine but my question is this: if want to minimize the number of API calls, what is the optimal way to split the bounding box? Splitting it into quadrants was just an arbitrary decision. When there are a lot of points on the map, I have to drill down many levels before I start getting meaningful results. So I imagine it might be faster to split the box into, say, 9, 16, or more sections. But if I do that, then I eventually get to a point where a lot of requests are returning 0 results which isn't so efficient. Also, does the size of the limit on the results set affect the answer? (This is all assuming that I have no prior knowledge of nominal point density in the bounding box)

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• Hibernate: same generated value in two properties

  - by Markos Fragkakis

  Hi, I have an entity A with fields: aId (the system id) bId I want the first to be generated: @Id @Column(name = "PRODUCT_ID", unique = true, nullable = false, precision = 12, scale = 0) @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "PROD_GEN") @BusinessKey public Long getAId() { return this.aId; } I want the bId to be initially exactly as the aId. One approach is to insert the entity, then get the aId generated by the DB (2nd query) and then update the entity, setting the bId to be equal to aId (3rd query). Is there a way to get the bId to get the same generated value as aId? Note that afterwards, I want to be able to update bId from my gui. If the solution is JPA, even better.

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• Why does DataInputStream not support integers?

  - by Jason

  I need to read in a list of numbers from a file, none of which are larger than 32767. Originally I was going to use the Scanner class to pull in the data, then I read about DataInputStream. This would work well for me, except that according to the API, it supports all primitive variables EXCEPT ints! Listed are longs, shorts, bytes, chars, booleans, ect, but no ints. I have no need for double precision from the incoming data. Is this a deliberate or unintentional oversight?

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• Calculating 3d rotation around random axis

  - by mitim

  This is actually a solved problem, but I want to understand why my original method didn't work (hoping someone with more knowledge can explain). (Keep in mind, I've not very experienced in 3d programming, having only played with the very basic for a little bit...nor do I have a lot of mathematical experience in this area). I wanted to animate a point rotating around another point at a random axis, say a 45 degrees along the y axis (think of an electron around a nucleus). I know how to rotate using the transform matrix along the X, Y and Z axis, but not an arbitrary (45 degree) axis. Eventually after some research I found a suggestion: Rotate the point by -45 degrees around the Z so that it is aligned. Then rotate by some increment along the Y axis, then rotate it back +45 degrees for every frame tick. While this certainly worked, I felt that it seemed to be more work then needed (too many method calls, math, etc) and would probably be pretty slow at runtime with many points to deal with. I thought maybe it was possible to combine all the rotation matrixes involve into 1 rotation matrix and use that as a single operation. Something like: [ cos(-45) -sin(-45) 0] [ sin(-45) cos(-45) 0] rotate by -45 along Z [ 0 0 1] multiply by [ cos(2) 0 -sin(2)] [ 0 1 0 ] rotate by 2 degrees (my increment) along Y [ sin(2) 0 cos(2)] then multiply that result by (in that order) [ cos(45) -sin(45) 0] [ sin(45) cos(45) 0] rotate by 45 along Z [ 0 0 1] I get 1 mess of a matrix of numbers (since I was working with unknowns and 2 angles), but I felt like it should work. It did not and I found a solution on wiki using a different matirx, but that is something else. I'm not sure if maybe I made an error in multiplying, but my question is: this is actually a viable way to solve the problem, to take all the separate transformations, combine them via multiplying, then use that or not?

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• Data structure for bubble shooter game

  - by SundayMonday

  I'm starting to make a bubble shooter game for a mobile OS. Assume this is just the basic "three or more same-color bubbles that touch pop" and all bubbles that are separated from their group fall/pop. What data structures are common for storing the bubbles? I've considered using an undirected, connected graph where each node is a bubble. This seems like it could help answer the question "which bubbles (if any) should fall now?" after some arbitrary bubbles are popped and corresponding nodes are removed from the graph. I think the answer is all bubbles that were just disconnected from the graph should fall. However the graph approach might be overkill so I'm not sure. Another consideration for the data structure is collision detection. Perhaps being able to grab a list of neighboring bubbles in constant time for a particular "bubble slot" is useful. So the collision detection would be something like "moving bubble is closest to slot ij, neighbors of slot ij are bubbles a,b,c, moving bubble is sufficiently close to bubble b hence moving bubble should come to rest in slot ij". A game like this could be probably be made with a relatively crude grid structure as the primary data structure. However it seems like answering "which bubbles (if any) should fall now?" would be trickier with this data structure.

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• HLSL How to flip geometry horizontally

  - by cubrman

  I want to flip my asymmetric 3d model horizontally in the vertex shader alongside an arbitrary plane parallel to the YZ plane. This should switch everything for the model from the left hand side to the right hand side (like flipping it in Photoshop). Doing it in pixel shader would be a huge computational cost (extra RT, more fullscreen samples...), so it must be done in the vertex shader. Once more: this is NOT reflection, i need to flip THE WHOLE MODEL. I thought I could simply do the following: Turn off culling. Run the following code in the vertex shader: input.Position = mul(input.Position, World); // World[3][0] holds x value of the model's pivot in the World. if (input.Position.x <= World[3][0]) input.Position.x += World[3][0] - input.Position.x; else input.Position.x -= input.Position.x - World[3][0]; ... The model is never drawn. Where am I wrong? I presume that messes up the index buffer. Can something be done about it? P.S. it's INSANELY HARD to format code here. Thanks to Panda I found my problem. SOLUTION: // Do thins before anything else in the vertex shader. Position.x *= -1; // To invert alongside the object's YZ plane.

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• SUM of metric for normalized logical hierarchy

  - by Alex254

  Suppose there's a following table Table1, describing parent-child relationship and metric: Parent | Child | Metric (of a child) ------------------------------------ name0 | name1 | a name0 | name2 | b name1 | name3 | c name2 | name4 | d name2 | name5 | e name3 | name6 | f Characteristics: 1) Child always has 1 and only 1 parent; 2) Parent can have multiple children (name2 has name4 and name5 as children); 3) Number of levels in this "hierarchy" and number of children for any given parent are arbitrary and do not depend on each other; I need SQL request that will return result set with each name and a sum of metric of all its descendants down to the bottom level plus itself, so for this example table the result would be (look carefully at name1): Name | Metric ------------------ name1 | a + c + f name2 | b + d + e name3 | c + f name4 | d name5 | e name6 | f (name0 is irrelevant and can be excluded). It should be ANSI or Teradata SQL. I got as far as a recursive query that can return a SUM (metric) of all descendants of a given name: WITH RECURSIVE temp_table (Child, metric) AS ( SELECT root.Child, root.metric FROM table1 root WHERE root.Child = 'name1' UNION ALL SELECT indirect.Child, indirect.metric FROM temp_table direct, table1 indirect WHERE direct.Child = indirect.Parent) SELECT SUM(metric) FROM temp_table; Is there a way to turn this query into a function that takes name as an argument and returns this sum, so it can be called like this? SELECT Sum_Of_Descendants (Child) FROM Table1; Any suggestions about how to approach this from a different angle would be appreciated as well, because even if the above way is implementable, it will be of poor performance - there would be a lot of iterations of reading metrics (value f would be read 3 times in this example). Ideally, the query should read a metric of each name only once.

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• Ruby on Rails - Currency : commas causing an issue.

  - by easement

  Looking on SO, I see that the preferred way to currency using RoR is using decimal(8,2) and to output them using number_to_currency(); I can get my numbers out of the DB, but I'm having issues on getting them in. Inside my update action I have the following line: if @non_labor_expense.update_attributes(params[:non_labor_expense]) puts YAML::dump(params) The dump of params shows the correct value. xx,yyy.zz , but what gets stored in the DB is only xx.00 What do I need to do in order to take into account that there may be commas and a user may not enter .zz (the cents). Some regex and for comma? how would you handle the decimal if it were .2 versus .20 . There has to be a builtin or at least a better way. My Migration (I don't know if this helps): class ChangeExpenseToDec < ActiveRecord::Migration def self.up change_column :non_labor_expenses, :amount, :decimal, :precision => 8, :scale => 2 end def self.down change_column :non_labor_expenses, :amount, :integer end end

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• CodePlex Daily Summary for Sunday, September 09, 2012

  CodePlex Daily Summary for Sunday, September 09, 2012Popular ReleasesMishra Reader: Mishra Reader Beta 4: Additional bug fixes and logging in this release to try to find the reason some users aren't able to see the main window pop up. Also, a few UI tweaks to tighten up the feed item list. This release requires the final version of .NET 4.5. If the ClickOnce installer doesn't work for you, please try the additional setup exe.Xenta Framework - extensible enterprise n-tier application framework: Xenta Framework 1.9.0: Release Notes Imporved framework architecture Improved the framework security More import/export formats and operations New WebPortal application which includes forum, new, blog, catalog, etc. UIs Improved WebAdmin app. Reports, navigation and search Perfomance optimization Improve Xenta.Catalog domain More plugin interfaces and plugin implementations Refactoring Windows Azure support and much more... Package Guide Source Code - package contains the source code Binaries...Json.NET: Json.NET 4.5 Release 9: New feature - Added JsonValueConverter Fix - Fixed DefaultValueHandling.Ignore not igoring default values of non-nullable properties Fix - Fixed DefaultValueHandling.Populate error with non-nullable properties Fix - Fixed error when writing JSON for a JProperty with no value Fix - Fixed error when calling ToList on empty JObjects and JArrays Fix - Fixed losing decimal precision when writing decimal JValuesMicrosoft Ajax Minifier: Microsoft Ajax Minifier 4.66: Just going to bite the bullet and rip off the band-aid... SEMI-BREAKING CHANGE! Well, it's a BREAKING change to those who already adjusted their projects to use the previous breaking change's ill-conceived renamed DLLs (versions 4.61-4.65). For those who had not adapted and were still stuck in this-doesn't-work-please-fix-me mode, this is more like a fixing change. The previous breaking change just broke too many people, I'm sorry to say. Renaming the DLL from AjaxMin.dll to AjaxMinLibrary.dl...DotNetNuke® Community Edition CMS: 07.00.00 CTP (Not for Production Use): NOTE: New Minimum Requirementshttp://www.dotnetnuke.com/Portals/25/Blog/Files/1/3418/Windows-Live-Writer-1426fd8a58ef_902C-MinimumVersionSupport_2.png Simplified InstallerThe first thing you will notice is that the installer has been updated. Not only have we updated the look and feel, but we also simplified the overall install process. You shouldn’t have to click through a series of screens in order to just get your website running. With the 7.0 installer we have taken an approach that a...BIDS Helper: BIDS Helper 1.6.1: In addition to fixing a number of bugs that beta testers reported, this release includes the following new features for Tabular models in SQL 2012: New Features: Tabular Display Folders Tabular Translations Editor Tabular Sync Descriptions Fixed Issues: Biml issues 32849 fixing bug in Tabular Actions Editor Form where you type in an invalid action name which is a reserved word like CON or which is a duplicate name to another action 32695 - fixing bug in SSAS Sync Descriptions whe...Umbraco CMS: Umbraco 4.9.0: Whats newThe media section has been overhauled to support HTML5 uploads, just drag and drop files in, even multiple files are supported on any HTML5 capable browser. The folder content overview is also much improved allowing you to filter it and perform common actions on your media items. The Rich Text Editor’s “Media” button now uses an embedder based on the open oEmbed standard (if you’re upgrading, enable the media button in the Rich Text Editor datatype settings and set TidyEditorConten...menu4web: menu4web 0.4.1 - javascript menu for web sites: This release is for those who believe that global variables are evil. menu4web has been wrapped into m4w singleton object. Added "Vertical Tabs" example which illustrates object notation.Microsoft SQL Server Product Samples: Database: AdventureWorks OData Feed: The AdventureWorks OData service exposes resources based on specific SQL views. The SQL views are a limited subset of the AdventureWorks database that results in several consuming scenarios: CompanySales Documents ManufacturingInstructions ProductCatalog TerritorySalesDrilldown WorkOrderRouting How to install the sample You can consume the AdventureWorks OData feed from http://services.odata.org/AdventureWorksV3/AdventureWorks.svc. You can also consume the AdventureWorks OData fe...Desktop Google Reader: 1.4.6: Sorting feeds alphabetical is now optional (see preferences window)Lightweight Fluent Workflow: objectflow 1.4.0.1: Changes in this release;Exception handling policies Install on NuGet console; Install-Package objectflow.core -pre Supported work-flow patterns Exception policies Sequence Parallel split Simple merge Exclusive choice Retry Arbitrary cycles Framework Features Handle exceptions with workflow.Configure().On<Exception>() Repeat operations and functions an arbitrary number of times Retry failed lamda functions Generic interface for concise workflow registration Operations t...Droid Explorer: Droid Explorer 0.8.8.7 Beta: Bug in the display icon for apk's, will fix with next release Added fallback icon if unable to get the image/icon from the Cloud Service Removed some stale plugins that were either out dated or incomplete. Added handler for *.ab files for restoring backups Added plugin to create device backups Backups stored in %USERPROFILE%\Android Backups\%DEVICE_ID%\ Added custom folder icon for the android backups directory better error handling for installing an apk bug fixes for the Runn...LibXmlSocket: Binary: .net4.5,.netCore???????Hidden Capture (HC): Hidden Capture 1.1: Hidden Capture 1.1 by Mohsen E.Dawatgar http://Hidden-Capture.blogfa.comThe Visual Guide for Building Team Foundation Server 2012 Environments: Version 1: --Nearforums - ASP.NET MVC forum engine: Nearforums v8.5: Version 8.5 of Nearforums, the ASP.NET MVC Forum Engine. New features include: Built-in search engine using Lucene.NET Flood control improvements Notifications improvements: sync option and mail body View Roadmap for more details webdeploy package sha1 checksum: 961aff884a9187b6e8a86d68913cdd31f8deaf83WiX Toolset: WiX Toolset v3.6: WiX Toolset v3.6 introduces the Burn bootstrapper/chaining engine and support for Visual Studio 2012 and .NET Framework 4.5. Other minor functionality includes: WixDependencyExtension supports dependency checking among MSI packages. WixFirewallExtension supports more features of Windows Firewall. WixTagExtension supports Software Id Tagging. WixUtilExtension now supports recursive directory deletion. Melt simplifies pure-WiX patching by extracting .msi package content and updating .w...Iveely Search Engine: Iveely Search Engine （0.2.0）: ????ISE?0.1.0??，?????，ISE?0.2.0?????????，???????，????????20???follow?ISE，????，??ISE??????????，??????????，?????????，?????????0.2.0??????，??????????。 Iveely Search Engine ?0.2.0?????????“??????????”，??????，?????????，???????，???????????????????，????、????????????。???0.1.0????????????： 1. ??“????” ??。??????????，?????????，???????????????????。??：????????，????????????，??????????????????。??????。 2. ??“????”??。?0.1.0??????，???????，???????????????，?????????????，????????，?0.2.0?，???????...GmailDefaultMaker: GmailDefaultMaker 3.0.0.2: Add QQ Mail BugfixSmart Data Access layer: Smart Data access Layer Ver 3: In this version support executing inline query is added. Check Documentation section for detail.New ProjectsAjax based Multi Forms ASP.NET Framework (Amfan): Ajax based Multi Forms ASP.NET Framework (Amfan) reduces the limitations of the Asp.Net by creating multiple sub-forms of the page as separate aspx pages.APO-CS: A straight port of Apophysis to C#.BaceCP / ???? ????? ?? ???????? ????: BaceCP e ??????????? ???????? ?? ????????, ??????????? ? ????????? ?? ???? ????? ?? ???????? ????.CafeAdm Messenger: CafeAdm Messenger Allows a server connection for CafeAdm Schedule and MessengerDECnet 2.0 Router: A user mode DECnet 2.0 router that will interoperate with the HECnet bridge.DriveManager: This is a common utility to provide an interface for all cloud based drive providers like google drive, dropbox, MS Sky Drive. Email Tester: This utility will help you check your SMTP settings for SharePoint. It is best for Pre-PROD and PROD environment where you can't modify code.EvoGame: The evo game that im working onforebittims: Project Owner : ForeBitt Inc. Sri Lanka Project Manager : Chackrapani Wickramarathne Technologies : VS 2010, C#, Linq to Sql, Sql server 2008 R2, Dev ExpressMCServe: MCServe is the minecraft-server which takes advantage of the performance of the .NET FrameworkMental: Ðang trong quá trình phát tri?nSalaryManagementSys: SalaryManagementSysVKplay: This application is audio player, launches on windows phone platform and uses music from vk.com social network.

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• Where to implement storable items

  - by James Hay

  I'm creating a multiplayer online trading game. The things that are traded range from raw items to complex products. For example Steel is a raw item. Mechanical Assembly is a more complex item that requires 2x Steel and maybe 1x Rubber. Then Hydraulics is an item that contains 2x Mechanical Assemblies and 1x Electronics (which is another complex item). So and so forth. These items will be created by me, players can't create their own items, so it doesn't need to be able to handle arbitrary layers of complexity for items. If my example isn't clear, think Minecraft. You have wooden planks, which can be made into sticks. From there the sticks - combined with metals - can be made into tools. My game is nothing to do with minecraft or any sandbox building game, but it uses a similar progressive complexity to creating items that I want to have in my game. My question is basically, how do you store something like this assuming that I will want to add more items in the future? Do you store it in a database or in a seperate library that the game uses? EDIT None of the items actually "do" anything, they are simply there to either sell, purchase, or combine with other items to make a more complex item, which can then be sold, purchased or combined... you get the idea. The items themselves would not have any properties, but the instances of the items would. For example an item that one player has would have a certain "quality" and if they were selling it a certain "price". An instance of that same item that a different player had would need to have a different "quality" and "price" if they were selling it. I think the price part will not be required on an individual item because instead I would have a "sale" object which was for a price and contained certain items.

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• Using a permutation table for simplex noise without storing it

  - by J. C. Leitão

  Generating Simplex noise requires a permutation table for randomisation (e.g. see this question or this example). In some applications, we need to persist the state of the permutation table. This can be done by creating the table, e.g. using def permutation_table(seed): table_size = 2**10 # arbitrary for this question l = range(1, table_size + 1) random.seed(seed) # ensures the same shuffle for a given seed random.shuffle(l) return l + l # see shared link why l + l; is a detail and storing it. Can we avoid storing the full table by generating the required elements every time they are required? Specifically, currently I store the table and call it using table[i] (table is a list). Can I avoid storing it by having a function that computes the element i, e.g. get_table_element(seed, i). I'm aware that cryptography already solved this problem using block cyphers, however, I found it too complex to go deep and implement a block cypher. Does anyone knows a simple implementation of a block cypher to this problem?

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• An alternative to multiple inheritance when creating an abstraction layer?

  - by sebf

  In my project I am creating an abstraction layer for some APIs. The purpose of the layer is to make multi-platform easier, and also to simplify the APIs to the feature set that I need while also providing some functionality, the implementation of which will be unique to each platform. At the moment, I have implemented it by defining and abstract class, which has methods which creates objects that implement interfaces. The abstract class and these interfaces define the capabilities of my abstraction layer. The implementation of these in my layer should of course be arbitrary from the POV view of my application, but I have done it, for my first API, by creating chains of subclasses which add more specific functionality as the features of the APIs they expose become less generic. An example would probably demonstrate this better: //The interface as seen by the application interface IGenericResource { byte[] GetSomeData(); } interface ISpecificResourceOne : IGenericResource { int SomePropertyOfResourceOne {get;} } interface ISpecificResourceTwo : IGenericResource { string SomePropertyOfResourceTwo {get;} } public abstract class MyLayer { ISpecificResourceOne CreateResourceOne(); ISpecificResourceTwo CreateResourceTwo(); void UseResourceOne(ISpecificResourceOne one); void UseResourceTwo(ISpecificResourceTwo two); } //The layer as created in my library public class LowLevelResource : IGenericResource { byte[] GetSomeData() {} } public class ResourceOne : LowLevelResource, ISpecificResourceOne { int SomePropertyOfResourceOne {get{}} } public class ResourceTwo : ResourceOne, ISpecificResourceTwo { string SomePropertyOfResourceTwo {get {}} } public partial class Implementation : MyLayer { override UseResourceOne(ISpecificResourceOne one) { DoStuff((ResourceOne)one); } } As can be seen, I am essentially trying to have two inheritance chains on the same object, but of course I can't do this so I simulate the second version with interfaces. The thing is though, I don't like using interfaces for this; it seems wrong, in my mind an interface defines a contract, any class that implements that interface should be able to be used where that interface is used but here that is clearly not the case because the interfaces are being used to allow an object from the layer to masquerade as something else, without the application needing to have access to its definition. What technique would allow me to define a comprehensive, intuitive collection of objects for an abstraction layer, while their implementation remains independent? (Language is C#)

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• Algorithmic problem - quickly finding all #'s where value %x is some given value

  - by Steve B.

  Problem I'm trying to solve, apologies in advance for the length: Given a large number of stored records, each with a unique (String) field S. I'd like to be able to find through an indexed query all records where Hash(S) % N == K for any arbitrary N, K (e.g. given a million strings, find all strings where HashCode(s) % 17 = 5. Is there some way of memoizing this so that we can quickly answer any question of this form without doing the % on every value? The motivation for this is a system of N distributed nodes, where each record has to be assigned to at least one node. The nodes are numbered 0 - (K-1) , and each node has to load up all of the records that match it's number: If we have 3 nodes Node 0 loads all records where Hash % 3 ==0 Node 1 loads all records where Hash % 3 ==1 Node 2 loads all records where Hash % 3 ==2 adding a 4th node, obviously all the assignments have to be recomputed - Node 0 loads all records where Hash % 4 ==0 ... etc I'd like to easily find these records through an indexed query without having to compute the mod individually. The best I've been able to come up with so far: If we take the prime factors of N (p1 * p2 * ... ) if N % M == I then p % M == I % p for all of N's prime factors e.g. 10 nodes : N % 10 == 6 then N % 2 = 0 == 6 %2 N % 5 = 1 == 6 %5 so storing an array of the "%" of N for the first "reasonable" number of primes for my data set should be helpful. For example in the above example we store the hash and the primes HASH PRIMES (array of %2, %3, %5, %7, ... ]) 16 [0 1 1 2 .. ] so looking for N%10 == 6 is equivalent to looking for all values where array[1]==1 and array[2] == 1. However, this breaks at the first prime larger than the highest number I'm storing in the factor table. Is there a better way?

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• Looking for solution to persist rows sequence in a database table that allow efficient reordering at

  - by Chau Chee Yang

  I have a database table. There is a field name "Sequence" that indicate sequence when user presents the rows in report or grid visually. When the rows are retrieved and presented in a grid, there are few UI gadget that allow user to reorder the rows arbitrary. The new sequence will be persist in database table when user commit the changes. Here are some UI operations: Move to first Move to last Move up 1 row Move down 1 row multi-select rows and move up or down multi-select rows and drag to new position For operation like "Move to first" or "Move to Last", it usually involve many rows and the sequence those rows would need to be updated accordingly. This may not be efficient enough at runtime. It is a common practice to use INTEGER as sequence's data type. Other solution is using "DOUBLE" or "FLOAT" that could overcome the mass update of row sequence but we will face problem if we reach the limit of precision.

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• C++ fixed point library?

  - by uj2

  I am looking for a free C++ fixed point library (Mainly for use with embedded devices, not for arbitrary precision math). Basically, the requirements are: No unnecessary runtime overhead: whatever can be done at compile time, should be done at compile time. Ability to transparently switch code between fixed and floating point, with no inherent overhead. Fixed point math functions. There's no much point using fixed point if you need to cast back and forth in order to take a square root. Small footprint. Any suggestions?

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• Is committing/checking in code everyday a good practice?

  - by ArtB

  I've been reading Martin Fowler's note on Continuous Integration and he lists as a must "Everyone Commits To the Mainline Every Day". I do not like to commit code unless the section I'm working on is complete and that in practice I commit my code every three days: one day to investigate/reproduce the task and make some preliminary changes, a second day to complete the changes, and a third day to write the tests and clean it up^ for submission. I would not feel comfortable submitting the code sooner. Now, I pull changes from the repository and integrate them locally usually twice a day, but I do not commit that often unless I can carve out a smaller piece of work. Question: is committing everyday such a good practice that I should change my workflow to accomodate it, or it is not that advisable? Edit: I guess I should have clarified that I meant "commit" in the CVS meaning of it (aka "push") since that is likely what Fowler would have meant in 2006 when he wrote this. ^ The order is more arbitrary and depends on the task, my point was to illustrate the time span and activities, not the exact sequence.

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• Floating point equality and tolerances

  - by doron

  Comparing two floating point number by something like a_float == b_float is looking for trouble since a_float / 3.0 * 3.0 might not be equal to a_float due to round off error. What one normally does is something like fabs(a_float - b_float) < tol. How does one calculate tol? Ideally tolerance should be just larger than the value of one or two of the least significant figures. So if the single precision floating point number is use tol = 10E-6 should be about right. However this does not work well for the general case where a_float might be very small or might be very large. How does one calculate tol correctly for all general cases? I am interested in C or C++ cases specifically.

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• strtod() and sprintf() inconsistency under GCC and MSVC

  - by Dmitry Sapelnikov

  I'm working on a cross-platform app for Windows and Mac OS X, and I have a problem with two standard C library functions: strtod() - string-to-double conversion sprintf() - when used for outputting double-precision floating point numbers) Their GCC and MSVC versions return different results. I'm looking for a well-tested cross-platform open-source implementation of those functions, or just for a pair of functions that would correctly and consistently convert double to string and back. I've already tried the clib GCC implementation, but the code is too long and too dependent on other source files, so I expect the adaptation to be difficult. What implementations of string-to-double and double-to-string functions would you recommend?

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• Express highest floating point quantity that is less than 1

  - by edA-qa mort-ora-y

  I was doing some rounding calculations and happened upon a question. How can I express the highest quantity less than 1 for a given floating point type? That is, how I write/represent value x such that x < 1, x + y >= 1 for any y > 0. In fractions this would be x = (q-1)/q where q is the precision of the type. For example, if you are counting in 1/999 increments then x = 998/999. For a given type (float, double, long double), how could one express the value x in code? I also wonder if such a value actually exists for all values of y. That is, as y's exponent gets smaller perhaps the relation doesn't hold anymore. So an answer with some range restriction on y is also acceptable. (The value of x I want still does exist, the relationship may just not properly express it.)

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• Rails - Format number as currency format in the Getter

  - by daemonsy

  I am making a simple retail commerce solution, where there are prices in a few different models. These prices contribute to a total price. Imagine paying $0.30 more for selecting a topping for your yogurt. When I set the price field to t.decimal :price, precision:8, scale:2 The database stores 6.50 as 6.5. I know in the standard rails way, you call number_to_currency(price) to get the formatted value in the Views. I need to programmatically call the price field as well formatted string, i.e. $6.50 a few places that are not directly part of the View. Also, my needs are simple (no currency conversion etc), I prefer to have the price formatted universally in the model without repeated calling number_to_currency in views. Is there a good way I can modify my getter for price such that it always returns two decimal place with a dollar sign, i.e. $6.50 when it's called? Thanks in advance.

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• Central renderer for a given scene

  - by Loggie

  When creating a central rendering system for all game objects in a given scene I am trying to work out the best way to go about passing the scene to the render system to be rendered. If I have a scene managed by an arbitrary structure, i.e., an octree, bsp trees, quad-tree, kd tree, etc. What is the best way to pass this to the render system? The obvious problem is that if simply given the root node of the structure, the render system would require an intrinsic knowledge of the structure in order to traverse the structure. My solution to this is to clip all objects outside the frustum in the scene manager and then create a list of the objects which are left and pass this simple list to the render system, be it an array, a vector, a linked list, etc. (This would be a structure required by the render system as a means to know which objects should be rendered). The list would of course attempt to minimise OpenGL state changes by grouping objects that require the same rendering operations to be performed on them. I have been thinking a lot about this and started searching various terms on here and followed any additional information/links but I have not really found a definitive answer. The case may be that there is no definitive answer but I would appreciate some advice and tips. My question is, is this a reasonable solution to the problem? Are there any improvements that I could make? Are there any caveats I should know about? Side question: Am I right in assuming that octrees, bsp trees, etc are all forms of BVH?

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• SQL CLR and nullable datetime parameter

  - by toluca70

  I'm trying to write a SQLCLR function that takes a DateTime2 as input and returns another DateTime2. Based on this post I altered the parameter to be the C# type DateTime giving me the level of precision I require. However because the input can be null I would like it to be DateTime?; the return type as well. using System; using Microsoft.SqlServer.Server; namespace SqlServer.Functions { public class UserDefinedFunctions { [SqlFunction(DataAccess = DataAccessKind.None)] public static DateTime? GetLocalTimeFromGMT(DateTime? dateTime) { if (dateTime.HasValue) return DateTime.SpecifyKind(dateTime.Value, DateTimeKind.Utc).ToLocalTime(); else return (DateTime?)null; } } } The problem is I get the following error when I try to deploy: Error 1 Cannot find the type 'Nullable`1', because it does not exist or you do not have permission. SqlServer.Functions I'm using Sql Server 2008 and Visual Studio 2008.

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• GPU Computing - # of GPUs supported

  - by TehTypoKing

  I currently have a desktop with 6 GPUs ( 3x HD 5970s ) in non-crossfire mode. Unfortunately, it seems that Windows 7 64bit only supports up to 4 GPUs. I have not been able to find a reliable source to deny or confirm this. If windows 7 has this limitation, is there a Linux flavor that supports more than 4 GPUs? In-case you are wondering, this is not for gaming but high-speed single precision computing. With this current setup ( if I can find 6gpu support ) I am looking to reach 13.8 Teraflops. Also, my motherboard does support 3 16x pci-xpress gen2 slots... and I have a 1500w powersupply plugged into a 20amp outlet. Windows is able to detect all 6 cores.. although, 2 of which displays the warning "Drivers failed to load". To recap: - Can windows support 6 GPUs? - If not, does Linux? Thank you.

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• What's a way to implement a flexible buff/debuff system?

  - by gkimsey

  Overview: Lots of games which RPG-like statistics allow for character "buffs", ranging from simple "Deal 25% extra damage" to more complicated things like "Deal 15 damage back to attackers when hit." The specifics of each type of buff aren't really relevant. I'm looking for a (presumably object-oriented) way to handle arbitrary buffs. Details: In my particular case, I have multiple characters in a turn-based battle environment, so I envisioned buffs being tied to events like "OnTurnStart", "OnReceiveDamage", etc. Perhaps each buff is a subclass of a main Buff abstract class, where only the relevant events are overloaded. Then each character could have a vector of buffs currently applied. Does this solution make sense? I can certainly see dozens of event types being necessary, it feels like making a new subclass for each buff is overkill, and it doesn't seem to allow for any buff "interactions". That is, if I wanted to implement a cap on damage boosts so that even if you had 10 different buffs which all give 25% extra damage, you only do 100% extra instead of 250% extra. And there's more complicated situations that ideally I could control. I'm sure everyone can come up with examples of how more sophisticated buffs can potentially interact with each other in a way that as a game developer I may not want. As a relatively inexperienced C++ programmer (I generally have used C in embedded systems), I feel like my solution is simplistic and probably doesn't take full advantage of the object-oriented language. Thoughts? Has anyone here designed a fairly robust buff system before?

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