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• Storing a Hex Grid

  - by Pedro Caetano

  I've been creating a small hex grid framework for Unity3D and have come to the following dilema. This is my coordinate system (taken from here) Link because I'm a new user It all works pretty nicely except for the fact I have no idea how to store it. I originally intended to store this in a 2D array and use images to generate my maps. One problem was that it had negative values (this was easily fixed by offsetting the coordinates a bit). However, due to this coordinate system, such an image or bitmap would have to be diamond shaped - and since these structures are square shaped, this would cause a lot of headaches even if I hack something together. Is there anything I'm missing that could fix this? I recall seeing a forum post regarding this in the unity forums but I can no longer find the link. Is writing a set of coordinate translators the best solution here? If you guys think it would be helpful, I can post code and images of my problem.

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• How'd they do it: Millions of tiles in Terraria

  - by William 'MindWorX' Mariager

  I've been working up a game engine similar to Terraria, mostly as a challenge, and while I've figured out most of it, I can't really seem to wrap my head around how they handle the millions of interactable/harvestable tiles the game has at one time. Creating around 500.000 tiles, that is 1/20th of what's possible in Terraria, in my engine causes the frame-rate to drop from 60 to around 20, even tho I'm still only rendering the tiles in view. Mind you, I'm not doing anything with the tiles, only keeping them in memory. Update: Code added to show how I do things. This is part of a class, which handles the tiles and draws them. I'm guessing the culprit is the "foreach" part, which iterates everything, even empty indexes. ... public void Draw(SpriteBatch spriteBatch, GameTime gameTime) { foreach (Tile tile in this.Tiles) { if (tile != null) { if (tile.Position.X < -this.Offset.X + 32) continue; if (tile.Position.X > -this.Offset.X + 1024 - 48) continue; if (tile.Position.Y < -this.Offset.Y + 32) continue; if (tile.Position.Y > -this.Offset.Y + 768 - 48) continue; tile.Draw(spriteBatch, gameTime); } } } ... Also here is the Tile.Draw method, which could also do with an update, as each Tile uses four calls to the SpriteBatch.Draw method. This is part of my autotiling system, which means drawing each corner depending on neighboring tiles. texture_* are Rectangles, are set once at level creation, not each update. ... public virtual void Draw(SpriteBatch spriteBatch, GameTime gameTime) { if (this.type == TileType.TileSet) { spriteBatch.Draw(this.texture, this.realm.Offset + this.Position, texture_tl, this.BlendColor); spriteBatch.Draw(this.texture, this.realm.Offset + this.Position + new Vector2(8, 0), texture_tr, this.BlendColor); spriteBatch.Draw(this.texture, this.realm.Offset + this.Position + new Vector2(0, 8), texture_bl, this.BlendColor); spriteBatch.Draw(this.texture, this.realm.Offset + this.Position + new Vector2(8, 8), texture_br, this.BlendColor); } } ... Any critique or suggestions to my code is welcome. Update: Solution added. Here's the final Level.Draw method. The Level.TileAt method simply checks the inputted values, to avoid OutOfRange exceptions. ... public void Draw(SpriteBatch spriteBatch, GameTime gameTime) { Int32 startx = (Int32)Math.Floor((-this.Offset.X - 32) / 16); Int32 endx = (Int32)Math.Ceiling((-this.Offset.X + 1024 + 32) / 16); Int32 starty = (Int32)Math.Floor((-this.Offset.Y - 32) / 16); Int32 endy = (Int32)Math.Ceiling((-this.Offset.Y + 768 + 32) / 16); for (Int32 x = startx; x < endx; x += 1) { for (Int32 y = starty; y < endy; y += 1) { Tile tile = this.TileAt(x, y); if (tile != null) tile.Draw(spriteBatch, gameTime); } } } ...

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• Determine how to display a tile based on surrounding tiles

  - by Jsmith

  I have a game engine which generates maps randomly, set on a 2d grid which is composed of 34px square graphical tiles. These tiles can be displayed in any of three ways, wall, corner, and floor(exists in 2 states, passable and impassible), and four directions, north, south, west and east. What I need to do is, based on the tiles around each individual tile, determine which state to display the tile in, e.g. north wall, northeast corner, floor so that when a player alters the map, the tiles around the affected tile adjust themselves to suit(i.e. tunneling). In case it becomes important, all gameobjects are inherited from the same class, whether they be players, NPC's, walls, or items.

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• Executing Stored Procedures in Visual Studio LightSwitch.

  - by dataintegration

  A LightSwitch Project is very easy way to visualize and manipulate information directly from one of our ADO.NET Providers. But when it comes to executing the Stored Procedures, it can be a bit more complicated. In this article, we will demonstrate how to execute a Stored Procedure in LightSwitch. For the purposes of this article, we will be using the RSSBus Email Data Provider, but the same process will work with any of our ADO.NET Providers. Creating the RIA Service. Step 1: Open Visual Studio and create a new WCF RIA Service Class Project. Step 2:Add the reference to the RSSBus Email Data Provider dll in the (ProjectName).Web project. Step 3: Add a new Domain Service Class to the (ProjectName).Web project. Step 4: In the new Domain Service Class, create a new class with the attributes needed for the Stored Procedure's parameters. In this demo, the Stored Procedure we are executing is called SendMessage. The parameters we will need are as follows: public class NewMessage{ [Key] public int ID { get; set; } public string FromEmail { get; set; } public string ToEmail { get; set; } public string Subject { get; set; } public string Text { get; set; } } Note: The created class must have an ID which will serve as the key value. Step 5: Create a new method that will executed when the insert event fires. Inside this method you can use the standards ADO.NET code which will execute the stored procedure. [Insert] public void SendMessage(NewMessage newMessage) { try { EmailConnection conn = new EmailConnection(connectionString); EmailCommand comm = new EmailCommand("SendMessage", conn); comm.CommandType = System.Data.CommandType.StoredProcedure; if (!newMessage.FromEmail.Equals("")) comm.Parameters.Add(new EmailParameter("@From", newMessage.FromEmail)); if (!newMessage.ToEmail.Equals("")) comm.Parameters.Add(new EmailParameter("@To", newMessage.ToEmail)); if (!newMessage.Subject.Equals("")) comm.Parameters.Add(new EmailParameter("@Subject", newMessage.Subject)); if (!newMessage.Text.Equals("")) comm.Parameters.Add(new EmailParameter("@Text", newMessage.Text)); comm.ExecuteNonQuery(); } catch (Exception exc) { Console.WriteLine(exc.Message); } } Step 6: Create a query method. We are not going to be using getNewMessages(), so it does not matter what it returns for the purpose of our example, but you will need to create a method for the query event as well. [Query(IsDefault=true)] public IEnumerable<NewMessage> getNewMessages() { return null; } Step 7: Rebuild the whole solution. Creating the LightSwitch Project. Step 8: Open Visual Studio and create a new LightSwitch Application Project. Step 9: On the Data Sources, add a new data source. Choose a WCF RIA Service Step 10: Choose to add a new reference and select the (Project Name).Web.dll generated from the RIA Service. Step 11: Select the entities you would like to import. In this case, we are using the recently created NewMessage entity. Step 13: On the Screens section, create a new screen and select the NewMessage entity as the Screen Data. Step 14: After you run the project, you will be able to add a new record and save it. This will execute the Stored Procedure and send the new message. If you create a screen to check the sent messages, you can refresh this screen to see the mail you sent. Sample Project To help you with get started using stored procedures in LightSwitch, download the fully functional sample project. You will also need the RSSBus Email Data Provider to make the connection. You can download a free trial here.

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• Algorithm to increase odds of matching when randomly selecting

  - by Bryan

  I am building a mobile game loosely based on dual n-back http://brainworkshop.sourceforge.net/tutorial.html Now with the game I have 9 squares (numbered 1 through 9) and 9 letters (A through K) In the current code, I randomly select a square (e.g. 3) and a letter (e.g. C), then repeat the random selection for the next turn. For 1-back, I test whether either, neither or both match the previous turn. The problem with my current code is I get very few matches - I can go through many turns without having either match. How can I increase the match frequency, or alternatively decrease the randomness so a match is more likely? I am not looking for specific code (but pseudo-code would be fine) - just more an approach to increase match frequency.

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• Web Service Example - Part 3: Asynchronous

  - by Denis T

  In this edition of the ADF Mobile blog we'll tackle part 3 of our Web Service examples.  In this posting we'll take a look at firing the web service asynchronously and then filling in the UI when it completes.  This can be useful when you have data on the device in a local store and want to show that to the user while the application uses lazy loading from a web service to load more data. Getting the sample code: Just click here to download a zip of the entire project.  You can unzip it and load it into JDeveloper and deploy it either to iOS or Android.  Please follow the previous blog posts if you need help getting JDeveloper or ADF Mobile installed.  Note: This is a different workspace than WS-Part2 What's different? In this example, when you click the Search button on the Forecast By Zip option, now it takes you directly to the results page, which is initially blank.  When the web service returns a second or two later the data pops into the UI.  If you go back to the search page and hit Search it will again clear the results and invoke the web service asynchronously.  This isn't really that useful for this particular example but it shows an important technique that can be used for other use cases. How it was done 1)  First we created a new class, ForecastWorker, that implements the Runnable interface.  This is used as our worker class that we create an instance of and pass to a new thread that we create when the Search button is pressed inside the retrieveForecast actionListener handler.  Once the thread is started, the retrieveForecast returns immediately.  2)  The rest of the code that we had previously in the retrieveForecast method has now been moved to the retrieveForecastAsync.  Note that we've also added synchronized specifiers on both these methods so they are protected from re-entrancy. 3)  The run method of the ForecastWorker class then calls the retrieveForecastAsync method.  This executes the web service code that we had previously, but now on a separate thread so the UI is not locked.  If we had already shown data on the screen it would have appeared before this was invoked.  Note that you do not see a loading indicator either because this is on a separate thread and nothing is blocked. 4)  The last but very important aspect of this method is that once we update data in the collections from the data we retrieve from the web service, we call AdfmfJavaUtilities.flushDataChangeEvents().   We need this because as data is updated in the background thread, those data change events are not propagated to the main thread until you explicitly flush them.  As soon as you do this, the UI will get updated if any changes have been queued. Summary of Fundamental Changes In This Application The most fundamental change is that we are invoking and handling our web services in a background thread and updating the UI when the data returns.  This allows an application to provide a better user experience in many cases because data that is already available locally is displayed while lengthy queries or web service calls can be done in the background and the UI updated when they return.  There are many different use cases for background threads and this is just one example of optimizing the user experience and generating a better mobile application. 

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• Tetris : Effective rotation

  - by hqt

  I rotate each piece by rotation formula. More detail, because rotation angle is 90 so : xNew = y; yNew = -x; But my method has met two problems : 1) Out of box : each type of pieces is fit in square 4x4. (0,0 at under left) But by this rotation, at some case they will out of this box. For example, there is a point with coordinate (5,6) So, please help me how to fit these coordinate into 4x4 box again, or give me another formula for this. 2) at I case : (4 squares at same row or same column), just has two rotations case. but in method above, they still has 4 pieces. So, how to prevent this. Thanks :)

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• How to make a stack stable? Need help for an explicit resting contact scheme (2-dimensional)

  - by Register Sole

  Previously, I struggle with the sequential impulse-based method I developed. Thanks to jedediah referring me to this paper, I managed to rebuild the codes and implement the simultaneous impulse based method with Projected-Gauss-Seidel (PGS) iterative solver as described by Erin Catto (mentioned in the reference of the paper as [Catt05]). So here's how it currently is: The simulation handles 2-dimensional rotating convex polygons. Detection is using separating-axis test, with a SKIN, meaning closest points between two polygons is detected and determined if their distance is less than SKIN. To resolve collision, simultaneous impulse-based method is used. It is solved using iterative solver (PGS-solver) as in Erin Catto's paper. Error-correction is implemented using Baumgarte's stabilization (you can refer to either paper for this) using J V = beta/dt*overlap, J is the Jacobian for the constraints, V the matrix containing the velocities of the bodies, beta an error-correction parameter that is better be < 1, dt the time-step taken by the engine, and overlap, the overlap between the bodies (true overlap, so SKIN is ignored). However, it is still less stable than I expected :s I tried to stack hexagons (or squares, doesn't really matter), and even with only 4 to 5 of them, they would swing! Also note that I am not looking for a sleeping scheme. But I would settle if you have any explicit scheme to handle resting contacts. That said, I would be more than happy if you have a way of treating it generally (as continuous collision, instead of explicitly as a special state). Ideas I have tried: Using simultaneous position based error correction as described in the paper in section 5.3.2, turned out to be worse than the current scheme. If you want to know the parameters I used: Hexagons, side 50 (pixels) gravity 2400 (pixels/sec^2) time-step 1/60 (sec) beta 0.1 restitution 0 to 0.2 coeff. of friction 0.2 PGS iteration 10 initial separation 10 (pixels) mass 1 (unit is irrelevant for now, i modified velocity directly<-impulse method) inertia 1/1000 Thanks in advance! I really appreciate any help from you guys!! :) EDIT In response to Cholesky's comment about warm starting the solver and Baumgarte: Oh right, I forgot to mention! I do save the contact history and the impulse determined in this time step to be used as initial guess in the next time step. As for the Baumgarte, here's what actually happens in the code. Collision is detected when the bodies' closest distance is less than SKIN, meaning they are actually still separated. If at this moment, I used the PGS solver without Baumgarte, restitution of 0 alone would be able to stop the bodies, separated by a distance of ~SKIN, in mid-air! So this isn't right, I want to have the bodies touching each other. So I turn on the Baumgarte, where its role is actually to pull the bodies together! Weird I know, a scheme intended to push the body apart becomes useful for the reverse. Also, I found that if I increase the number of iteration to 100, stacks become much more stable, though the program becomes so slow. UPDATE Since the stack swings left and right, could it be something is wrong with my friction model? Current friction constraint: relative_tangential_velocity = 0

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• Simple moving object jitters every couple of seconds [on hold]

  - by Liam

  I'm trying to get smooth movement in my game, right now every couple of seconds the moving square jitters. I'm using C++ with SDL2. I made a very simple project to test different methods so all that's happening is a box moves across the screen. Here's a pastebin of the code http://pastebin.com/7YxxSw0D Here's a link to a dropbox folder containing the 'game' https://www.dropbox.com/sh/0ygntl140qv8iv0/AABVuuk6khArOJmdBi1OaFlua?dl=0 Any input would be greatly appreciated, and let me know if you need any more info. Thanks!

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• Determining the angle to fire a shot when target and shooter moves, and bullet moves with shooter velocity added in

  - by Azaral

  I saw this question: Predicting enemy position in order to have an object lead its target and followed the link in the answer to stack overflow. In the stack overflow page I used the 2nd answer, the one that is a large mathematical derivation. My situation is a little different though. My first question though is will the answer provided in the stack overflow page even work to begin with, assuming the original circumstances of moving target and stationary shooter. My situation is a little different than that situation. My target moves, the shooter moves, and the bullets from the shooter start off with the velocities in x and y added to the bullets' x and y velocities. If you are sliding to the right, the bullets will remain in front of you as you move so as long as your velocity remains constant. What I'm trying to do is to get the enemy to be able to determine where they need to shoot in order to hit the player. Unless the player and enemy is stationary, the velocity from the ship adding to the velocity of the bullets will cause a miss. I'd rather like to prevent that. I used the formula in the stack overflow answer and did what I thought were the appropriate adjustments. I've been banging at this for the last four hours and I just can't make it click. It is probably something really simple and boneheaded that I am missing (that seems to be a lot of my problems lately). Here is the solution presented from the stack overflow answer: It boils down to solving a quadratic equation of the form: a * sqr(x) + b * x + c == 0 Note that by sqr I mean square, as opposed to square root. Use the following values: a := sqr(target.velocityX) + sqr(target.velocityY) - sqr(projectile_speed) b := 2 * (target.velocityX * (target.startX - cannon.X) + target.velocityY * (target.startY - cannon.Y)) c := sqr(target.startX - cannon.X) + sqr(target.startY - cannon.Y) Now we can look at the discriminant to determine if we have a possible solution. disc := sqr(b) - 4 * a * c If the discriminant is less than 0, forget about hitting your target -- your projectile can never get there in time. Otherwise, look at two candidate solutions: t1 := (-b + sqrt(disc)) / (2 * a) t2 := (-b - sqrt(disc)) / (2 * a) Note that if disc == 0 then t1 and t2 are equal. If there are no other considerations such as intervening obstacles, simply choose the smaller positive value. (Negative t values would require firing backward in time to use!) Substitute the chosen t value back into the target's position equations to get the coordinates of the leading point you should be aiming at: aim.X := t * target.velocityX + target.startX aim.Y := t * target.velocityY + target.startY Here is my code, after being corrected by Sam Hocevar (thank you again for your help!). It still doesn't work. For some reason it never enters the section of code inside the if(disc = 0) (obviously because it is always less than zero but...). However, if I plug the numbers from my game log on the enemy and player positions and velocities it outputs a valid firing solution. I have looked at the code side by side a couple of times now and I can't find any differences. There has got to be something simple I'm missing here. If someone else could look at this code and determine what is going on here I'd appreciate it. I know it's not going through that section because if it were, shouldShoot would become true and the enemy would be blasting away at the player. This section calls the function in question, CalculateShootHeading() if(shouldMove) { UseEngines(); } x += xVelocity; y += yVelocity; CalculateShootHeading(); if(shouldShoot) { ShootWeapons(); } UpdateWeapons(); This is CalculateShootHeading(). This is inside the enemy class so x and y are the enemy's x and y and the same with velocity. One output from my game log gives Player X = 2108, Player Y = -180.956, Player X velocity = 10.9949, Player Y Velocity = -6.26017, Enemy X = 1988.31, Enemy Y = -339.051, Enemy X velocity = 1.81666, Enemy Y velocity = -9.67762, 0 enemy projectiles. The output from the console tester is Bullet position = 2210.49, -239.313 and Player Position = 2210.49, -239.313. This doesn't make any sense. The only thing that could be different is the code or the input into my function in the game and I've checked that and I don't think that it is wrong as it's updated before this and never changed. float const bulletSpeed = 30.f; float const dx = playerX - x; float const dy = playerY - y; float const vx = playerXVelocity - xVelocity; float const vy = playerYVelocity - yVelocity; float const a = vx * vx + vy * vy - bulletSpeed * bulletSpeed; float const b = 2.f * (vx * dx + vy * dy); float const c = dx * dx + dy * dy; float const disc = b * b - 4.f * a * c; shouldShoot = false; if (disc >= 0.f) { float t0 = (-b - std::sqrt(disc)) / (2.f * a); float t1 = (-b + std::sqrt(disc)) / (2.f * a); if (t0 < 0.f || (t1 < t0 && t1 >= 0.f)) { t0 = t1; } if (t0 >= 0.f) { float shootx = vx + dx / t0; float shooty = vy + dy / t0; heading = std::atan2(shooty, shootx) * RAD2DEGREE; } shouldShoot = true; }

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• Issue with permanent redirect implementation

  - by Argoron

  I have a tricky problem related to 301 redirections I badly need help with. I tried to implement these via .htaccess, but ran into trouble. The start of my .htaccess looks like this: SetEnv PHP_VER 5 Options +FollowSymlinks RewriteEngine on # Redirect non-www to www RewriteCond %{HTTP_HOST} !^(www\.|$) [NC] RewriteRule ^ http://www.%{HTTP_HOST}%{REQUEST_URI} [R=301,L] #--- GENERAL --- RewriteRule ^index\.html$ index.php [L] ... When I try to put a permanent redirect to index.php by adding R=301 in the square brackets, I get a 404, and I have no idea where the error comes from.

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• Algorithm for optimal combination of two variables

  - by AlanChavez

  I'm looking for an algorithm that would be able to determine the optimal combination of two variables, but I'm not sure where to start looking. For example, if I have 10,000 rows in a database and each row contains price, and square feet is there any algorithm out there that will be able to determine what combination of price and sq ft is optimal. I know this is vague, but I assume is along the lines of Fuzzy logic and fuzzy sets, but I'm not sure and I'd like to start digging in the right field to see if I can come up with something that solves my problem.

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• Effecient finding of long-range spotting targets

  - by nihohit

  I'm creating a top-down 2d strategy game, with a square grid map. So far, I've used Bresenham's line drawing algorithm in a circle to determine what's in LOS of each unit, and then targedt one of the targets in the circle. Now I find that this limits my units to shoot only at targets that they see. I want to extend my targeting algorithm to target any other unit in range of my weapon, even if they're out of sight range of this given unit, if they're "spotted" by another friendly unit. In other words, I want to enable usage of weapons with ranges longer than sight range. Is there a better way than iterating over all sighted units and computing range and LOSto each of them?

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• Is it possible to procedurally place objects in a non-gridded game?

  - by nickbadal

  I'd like to implement procedural world generation, but I don't want it to look gridded or blocky, where everything is obviously placed on an integer grid. I know that you can do this in gridded worlds by inputting a square's x and y into a noise function, or similar, but is it possible to generate a more natural looking object placement using procedural methods? This is in the context of an adventure game, if it matters. Edit: I guess I should have been a bit more clear in my original question, but I'm mostly wondering about the actual placement of objects in game, e.g. trees, buildings.

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• Should I drawing directly on CCLayer or CCSprite?

  - by einverne

  Now I am a little confused in my cocos2d-x cpp project. I want to draw lines with user's finger touch. Following the screenshot of a CCScene: In the screen, there are two squares. I want show an animation in the first square and let the second one draw lines with user touch. Now these two squares are CCSprite. And I can draw dots in the second one on the CCLayer. But I am little confused that I should draw lines on the Sprite or on the Layer. Or are there other ways to organize the code?

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• OpenGL: Drawing to a texture

  - by Danran

  Well im just a bit stuck wondering how to draw an item to a texture. Specifically, i'm using; glDrawArrays(GL_LINE_STRIP, indices[0], indices.size()); Because what i'm drawing via the above function updates every-frame, i'm just totally not sure how to go about drawing what i have to a texture. Any help is greatly appreciated! Edit: Well unfortunately my graphics card doesn't support FrameBuffer Objects :/. So i've been trying to get the copy contents from backbuffer method working. Here's what i currently have; http://pastebin.com/dJpPt6Pd And sadly all i get is a white square. Its probably something stupid that i'm doing wrong. Just unsure what it could be?

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• How can you procedurally place objects in a non-gridded game?

  - by nickbadal

  This is a follow-up question to this question. I mistakenly worded the question, but got a good answer before I could correct myself, so I didn't want to delete it. Sorry! Now that I know that it is possible, I'd like to implement procedural world generation, but I don't want it to look gridded or blocky, where everything is obviously placed on an integer grid. I know that you can do this in gridded worlds by inputting a square's x and y into a noise function, or similar, but how can I generate a more natural looking object placement using procedural methods? This is in the context of an adventure game, if it matters.

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• Best way to load application settings

  - by enzom83

  A simple way to keep the settings of a Java application is represented by a text file with ".properties" extension containing the identifier of each setting associated with a specific value (this value may be a number, string, date, etc..). C# uses a similar approach, but the text file must be named "App.config". In both cases, in source code you must initialize a specific class for reading settings: this class has a method that returns the value (as string) associated with the specified setting identifier. // Java example Properties config = new Properties(); config.load(...); String valueStr = config.getProperty("listening-port"); // ... // C# example NameValueCollection setting = ConfigurationManager.AppSettings; string valueStr = setting["listening-port"]; // ... In both cases we should parse strings loaded from the configuration file and assign the ??converted values to the related typed objects (parsing errors could occur during this phase). After the parsing step, we must check that the setting values ??belong to a specific domain of validity: for example, the maximum size of a queue should be a positive value, some values ??may be related (example: min < max), and so on. Suppose that the application should load the settings as soon as it starts: in other words, the first operation performed by the application is to load the settings. Any invalid values for the settings ??must be replaced automatically with default values??: if this happens to a group of related settings, those settings are all set with default values. The easiest way to perform these operations is to create a method that first parses all the settings, then checks the loaded values ??and finally sets any default values??. However maintenance is difficult if you use this approach: as the number of settings increases while developing the application, it becomes increasingly difficult to update the code. In order to solve this problem, I had thought of using the Template Method pattern, as follows. public abstract class Setting { protected abstract bool TryParseValues(); protected abstract bool CheckValues(); public abstract void SetDefaultValues(); /// <summary> /// Template Method /// </summary> public bool TrySetValuesOrDefault() { if (!TryParseValues() || !CheckValues()) { // parsing error or domain error SetDefaultValues(); return false; } return true; } } public class RangeSetting : Setting { private string minStr, maxStr; private byte min, max; public RangeSetting(string minStr, maxStr) { this.minStr = minStr; this.maxStr = maxStr; } protected override bool TryParseValues() { return (byte.TryParse(minStr, out min) && byte.TryParse(maxStr, out max)); } protected override bool CheckValues() { return (0 < min && min < max); } public override void SetDefaultValues() { min = 5; max = 10; } } The problem is that in this way we need to create a new class for each setting, even for a single value. Are there other solutions to this kind of problem? In summary: Easy maintenance: for example, the addition of one or more parameters. Extensibility: a first version of the application could read a single configuration file, but later versions may give the possibility of a multi-user setup (admin sets up a basic configuration, users can set only certain settings, etc..). Object oriented design.

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• I need help with 2D collision response (of stacking rotating polygons, with friction and gravity, for a game)

  - by Register Sole

  Hi I am looking for suggestions on how to write a collision response for game programming purpose (so not a scientific simulation). I am dealing with 2D polygons that are rotating, and I want them to be able to stack. I also want friction and gravity. I have a detection mechanism that returns the separating axis, how long the polygons are overlapping, and up to 2 points of contact. For the response, I am currently using an impulse-based response, which main idea is: find the separating axis, length of overlap, and the point of contact (if there are two, pick a random point between to simulate averaged force. i believe there are better ways than this) separate the object (modifying their positions, taking into account of their masses. i do not separate them completely though, to keep track that they are colliding to reduce jitter) calculate normal force based on the coefficient of restitution as if there is no friction. calculate friction, as if there is no normal force. I also assume that the direction of the friction is the same throughout the collision. apply the two forces (which result in a rather inaccurate result, since each force is calculated as if the other is not present. for non-rotating bodies though, this method is exact) I am aware that this method requires the coefficient of friction to be sufficiently small due to the assumption that the direction of friction stays the same in a collision. Also, the result is visually satisfying if gravity is not present. However, when there is gravity, objects on ground jitter and drift (even with zero coefficient of restitution)! It also happens for stacking objects. Larger coefficient of restitution and gravity increase the jittering. I hope you can help me with this. Some things i would like to know more about is how to handle collision with two point of contacts (how to end up having an object sitting still on the ground?), how to reduce, and prevent if possible, jitter and drift (do people use the most accurate method possible, or is there a trick to overcome this?), and how to handle multiple objects collision (for example, in the case of stacking objects, how do I check collisions between all of them and keep them all stable at every frame so they don't jitter?). A total reformulation of my algorithm is also welcomed, as long as it works. Another thing to note is that I am not making a Physics game, so I only need a visually satisfying response (though a realistic response is preferable, if it is not performance-heavy). But surely jittering and drifting objects on flat ground are not at all acceptable. In addition, I am a Physics student, so feel free to talk about impulse and whatever needed. Finally, I'm sorry for the long post. I tried to be as concise as I can. Thank you for reading it! EDIT It seems what I didn't manage to come up all this time is to separate resting contact as a class of its own and how to solve them. Currently reading the paper suggested by Jedediah. More suggestions on the topic are welcome :) CASE CLOSED After reading various papers referenced in the paper, successfully implemented simultaneous impulse method (referring to the original paper by Erin Catto, [Catt05]). Thanks maaaan!! The paper is wonderful. The current system is visibly much better than the previous. Still haven't separated resting contact as a class of its own though, which brings me to my next question. Love you all! Haha (sorry, I'm just so happy thanks to you).

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• Showing range on hexagonal grid

  - by user23673

  Here is the situation. I have hexagonal board,and a unit on it,with speed or move value 4.Diffrent terrain has a diffrent cost.When i click on the unit,game should show me a move range. My solution was to check each hex in range of 4,with A* pathfinding,and if path cost was less than 4 then this hex was in range.Finally game nicely show me range of that unit. My question is: Is there other solution to search for range on hex grids or square grid,because even if i am really proud of what i did in my solution,i think,it is a little to exaggerated?:)) What make me ask this question?I noticed that when unit speed is 4 or 6 or even 8,time to computing range for my computer was really good,but when speed was 10 and more i noticed that i needed to wait few second to compute.Well in real games i rather dont see something like this and my A* pathfinding is rather well optimized,so im thinking that my solution is wrong. Thanks for any replies.

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• Driver inversion

  - by Val

  I have a GUI game, which is driven by user every time it clicks the mouse. Every time user clicks a square on a board, the board state is updated (we re-compute the score, the player to make next move and legal movements it can make) and repainted. Both mouse click, state recomputation and painting are handled in the GUI thread. Now, suppose that I want to train AI to play without GUI. That is, game engine should consume next move by simply calling AI's makeMove function in one thread. This would allow to play millions of games per second automatically. GUI may just screenshot some arbitrary states time after time. How do you switch to this strategy?

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• connecting mysql from android with jdbc

  - by manuraphy

  hai i used the following code to connect mysql in local host from android. it only displays the actions given in catch section . i dont know whether its a connection problem or not package com.test1; import java.sql.Connection; import java.sql.DriverManager; import java.sql.PreparedStatement; import java.sql.ResultSet; import android.app.Activity; import android.os.Bundle; import android.widget.TextView; public class Test1Activity extends Activity { /** Called when the activity is first created. */ String str="new"; static ResultSet rs; static PreparedStatement st; static Connection con; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); final TextView tv=(TextView)findViewById(R.id.user); try { Class.forName("com.mysql.jdbc.Driver"); con=DriverManager.getConnection("jdbc:mysql://10.0.2.2:8080/example","root",""); st=con.prepareStatement("select * from country where id=1"); rs=st.executeQuery(); while(rs.next()) { str=rs.getString(2); } tv.setText(str); setContentView(tv); } catch(Exception e) { tv.setText(str); } } } when executes it displays "new" in the avd. java.lang.management.ManagementFactory.getThreadMXBean, referenced from method com.mysql.jdbc.MysqlIO.appendDeadlockStatusInformation Could not find class 'javax.naming.StringRefAddr', referenced from method com.mysql.jdbc.ConnectionPropertiesImpl$ConnectionProperty.storeTo Could not find method javax.naming.Reference.get, referenced from method com.mysql.jdbc.ConnectionPropertiesImpl$ConnectionProperty.initializeFrom can anyone suggest some solution ? and thankz in advance

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• Rendering a UIWebView in drawRect with loadHTMLString

  - by Nick Weaver

  Hello there, I am having a problem with UIWebView. I'd like to render my own html code in it. When I add a webview as a subview and put in some html code it renders just fine. When it gets down to some optimized drawing of tableview cell with the drawRect method the problem pops up. Drawing UIView descendants works pretty well this way. It's even possible to load a URL with the loadRequest method, setting the delegate, conforming to the UIWebViewDelegate protocol and redrawing the table cell with setNeedsDisplay when webViewDidFinishLoad is called. It does show, but when it comes to loadHTMLString, nothing shows up, only a white rect. Due to performance reasons I have to do the drawing in the drawRect method. Any ideas? Thanks in advance Nick Example snippet code for the html code being loaded by a UIWebView: NSString *html = @"<html><head><title>My fancy webview</title></head><body style='background-color:green;'><p>It somehow seems<h2 style='color:black;'>this does not show up in drawRect</h2>!</p></body></html>"; [webView loadHTMLString:html baseURL:nil]; Snippet for the drawRect method: - (void)drawRect:(CGRect)aRect { CGContextRef context = UIGraphicsGetCurrentContext(); [[webView layer] renderInContext:context]; }

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• Philosophy of [WebInvoke(ResponseFormat = WebMessageFormat.Json)]

  - by Mikey Cee

  Hi everyone, I'm writing what I'm referring to as a POJ (Plain Old JSON) WCF web service - one that takes and emits standard JSON with none of the crap that ASP.NET Ajax likes to add to it. It seems that there are three steps to accomplish this: Change to in the endpoint's tag Decorate the method with [WebInvoke(ResponseFormat = WebMessageFormat.Json)] Add an incantation of [AspNetCompatibilityRequirements(RequirementsMode = AspNetCompatibilityRequirementsMode.Allowed)] to the service contract This is all working OK for me - I can pass in and am being returned nice plain JSON. If I remove the WebInvoke attribute, then I get XML returned instead, so it is certainly doing what it is supposed to do. But it strikes me as odd that the option to specify JSON output appears here and not in the configuration file. Say I wanted to expose my method as an XML endpoint too - how would I do this? Currently the only way I can see would be to have a second method that does exactly the same thing but does not have WebMethodFormat.Json specified. Then rinse and repeat for every method in my service? Yuck. Specifying that the output should be serialized to JSON in the attribute seems to be completely contrary to the philosophy of WCF, where the service is implemented is a transport and encoding agnostic manner, leaving the nasty details of how the data will be moved around to the configuration file. Is there a better way of doing what I want to do? Or are we stuck with this awkward attribute? Or do I not understanding WCF deeply enough?

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• Hidden Features of C#?

  - by Serhat Özgel

  This came to my mind after I learned the following from this question: where T : struct We, C# developers, all know the basics of C#. I mean declarations, conditionals, loops, operators, etc. Some of us even mastered the stuff like Generics, anonymous types, lambdas, linq, ... But what are the most hidden features or tricks of C# that even C# fans, addicts, experts barely know? Here are the revealed features so far: Keywords yield by Michael Stum var by Michael Stum using() statement by kokos readonly by kokos as by Mike Stone as / is by Ed Swangren as / is (improved) by Rocketpants default by deathofrats global:: by pzycoman using() blocks by AlexCuse volatile by Jakub Šturc extern alias by Jakub Šturc Attributes DefaultValueAttribute by Michael Stum ObsoleteAttribute by DannySmurf DebuggerDisplayAttribute by Stu DebuggerBrowsable and DebuggerStepThrough by bdukes ThreadStaticAttribute by marxidad FlagsAttribute by Martin Clarke ConditionalAttribute by AndrewBurns Syntax ?? operator by kokos number flaggings by Nick Berardi where T:new by Lars Mæhlum implicit generics by Keith one-parameter lambdas by Keith auto properties by Keith namespace aliases by Keith verbatim string literals with @ by Patrick enum values by lfoust @variablenames by marxidad event operators by marxidad format string brackets by Portman property accessor accessibility modifiers by xanadont ternary operator (?:) by JasonS checked and unchecked operators by Binoj Antony implicit and explicit operators by Flory Language Features Nullable types by Brad Barker Currying by Brian Leahy anonymous types by Keith __makeref __reftype __refvalue by Judah Himango object initializers by lomaxx format strings by David in Dakota Extension Methods by marxidad partial methods by Jon Erickson preprocessor directives by John Asbeck DEBUG pre-processor directive by Robert Durgin operator overloading by SefBkn type inferrence by chakrit boolean operators taken to next level by Rob Gough pass value-type variable as interface without boxing by Roman Boiko programmatically determine declared variable type by Roman Boiko Static Constructors by Chris Easier-on-the-eyes / condensed ORM-mapping using LINQ by roosteronacid Visual Studio Features select block of text in editor by Himadri snippets by DannySmurf Framework TransactionScope by KiwiBastard DependantTransaction by KiwiBastard Nullable<T> by IainMH Mutex by Diago System.IO.Path by ageektrapped WeakReference by Juan Manuel Methods and Properties String.IsNullOrEmpty() method by KiwiBastard List.ForEach() method by KiwiBastard BeginInvoke(), EndInvoke() methods by Will Dean Nullable<T>.HasValue and Nullable<T>.Value properties by Rismo GetValueOrDefault method by John Sheehan Tips & Tricks nice method for event handlers by Andreas H.R. Nilsson uppercase comparisons by John access anonymous types without reflection by dp a quick way to lazily instantiate collection properties by Will JavaScript-like anonymous inline-functions by roosteronacid Other netmodules by kokos LINQBridge by Duncan Smart Parallel Extensions by Joel Coehoorn

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