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• Truly Random Numbers

  German researchers use a "flip-flop" to improve random number generator Random number generation - Algorithms - Pseudorandom Numbers - Math - Recreation

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• To SYNC or not to SYNC – Part 4

  - by AshishRay

  This is Part 4 of a multi-part blog article where we are discussing various aspects of setting up Data Guard synchronous redo transport (SYNC). In Part 1 of this article, I debunked the myth that Data Guard SYNC is similar to a two-phase commit operation. In Part 2, I discussed the various ways that network latency may or may not impact a Data Guard SYNC configuration. In Part 3, I talked in details regarding why Data Guard SYNC is a good thing, and the distance implications you have to keep in mind. In this final article of the series, I will talk about how you can nicely complement Data Guard SYNC with the ability to failover in seconds. Wait - Did I Say “Seconds”? Did I just say that some customers do Data Guard failover in seconds? Yes, Virginia, there is a Santa Claus. Data Guard has an automatic failover capability, aptly called Fast-Start Failover. Initially available with Oracle Database 10g Release 2 for Data Guard SYNC transport mode (and enhanced in Oracle Database 11g to support Data Guard ASYNC transport mode), this capability, managed by Data Guard Broker, lets your Data Guard configuration automatically failover to a designated standby database. Yes, this means no human intervention is required to do the failover. This process is controlled by a low footprint Data Guard Broker client called Observer, which makes sure that the primary database and the designated standby database are behaving like good kids. If something bad were to happen to the primary database, the Observer, after a configurable threshold period, tells that standby, “Your time has come, you are the chosen one!” The standby dutifully follows the Observer directives by assuming the role of the new primary database. The DBA or the Sys Admin doesn’t need to be involved. And - in case you are following this discussion very closely, and are wondering … “Hmmm … what if the old primary is not really dead, but just network isolated from the Observer or the standby - won’t this lead to a split-brain situation?” The answer is No - It Doesn’t. With respect to why-it-doesn’t, I am sure there are some smart DBAs in the audience who can explain the technical reasons. Otherwise - that will be the material for a future blog post. So - this combination of SYNC and Fast-Start Failover is the nirvana of lights-out, integrated HA and DR, as practiced by some of our advanced customers. They have observed failover times (with no data loss) ranging from single-digit seconds to tens of seconds. With this, they support operations in industry verticals such as manufacturing, retail, telecom, Internet, etc. that have the most demanding availability requirements. One of our leading customers with massive cloud deployment initiatives tells us that they know about server failures only after Data Guard has automatically completed the failover process and the app is back up and running! Needless to mention, Data Guard Broker has the integration hooks for interfaces such as JDBC and OCI, or even for custom apps, to ensure the application gets automatically rerouted to the new primary database after the database level failover completes. Net Net? To sum up this multi-part blog article, Data Guard with SYNC redo transport mode, plus Fast-Start Failover, gives you the ideal triple-combo - that is, it gives you the assurance that for critical outages, you can failover your Oracle databases: very fast without human intervention, and without losing any data. In short, it takes the element of risk out of critical IT operations. It does require you to be more careful with your network and systems planning, but as far as HA is concerned, the benefits outweigh the investment costs. So, this is what we in the MAA Development Team believe in. What do you think? How has your deployment experience been? We look forward to hearing from you!

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• When the obvious answer is obviously wrong

  - by John Paul Cook

  This post is about how simple math in T-SQL can produce undesirable results, but first we begin with a math quiz. Answer the following as quickly as possible: You just read pages 100-300 of a book. How many pages did you read? QUICKLY NOW! For those of you who answered 200 pages, I have a new question: Which page did you not read? There were 201 pages to read. If you read 200 pages, you skipped a page! What your answer be if I asked you how many pages did you read if you read pages 1-3? Three pages!...(read more)

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• What are the fundamentals of game development?

  - by Matt

  Hi, I completely do not understand how a video game can be coded. I'm a beginner programmer and only have experience writing console applications that do math and what not. I do not understand how these logical processes can make images move on the screen (video games). Obviously if i jumped into a game development book or something like that I would understand but I am currently still getting a grasp of the fundamentals of programming in general. Could anyone give a simple explanation , coding wise, on the jump between making a computer do simple math to making a computer produce amazing graphical programs such as video games? Maybe there are some intro videos someone can point me to? I

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• Keeping rotation between two objects

  - by user99

  In my XNA game I have two objects that collide. When the first object collides with the other it is able to latch on to it and move it about the world. I am having a problem with the math here (Math isn't my strong point). I currently have the second object latch on to the first and move around with it, but I cannot get it to keep it's original direction. So, if the object is facing up it should keep this direction relative to how it is being rotated with the original item. Any tips on how I could best to achieve this?

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• Deterministic Multiplayer RTS game questions?

  - by Martin K

  I am working on a cross-platform multiplayer RTS game where the different clients and a server(flash and C#), all need to stay deterministically synchronised. To deal with Floatpoint inconsistencies, I've come across this method: http://joshblog.net/2007/01/30/flash-floating-point-number-errors/#comment-49912 which basically truncates off the nondeterministic part: return Math.round(1000 * float) / 1000; Howewer my concern is that every time there is a division, there is further chance of creating additional floatpoint errors, in essence making it worse? . So it occured to me, how about something like this: function floatSafe(number:Number) : Number {return Math.round(float* 1024) / 1024; } ie dividing with only powers of 2 ? What do you think? . Ironically with the above method I got less accurate results: trace( floatSafe(3/5) ) // 0.599609375 where as with the other method(dividing with 1000), or just tracing the raw value I am getting 3/5 = 0.6 or Maybe thats what 3/5 actually is, IE 0.6 cannot really be represented with a floatpoint datatype, and would be more consistent across different platforms?

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• HedgeWar code confusion

  - by BluFire

  I looked at an open source project(HedgeWars) that was built using many programming languages such as C++ and Java. While I was looking through the code, I couldn't help noticing that all the math and physics were gone from the Java code. HedgeWars I imported the project file called "SDL-android-project" which was a sub folder to "android build" and project files. My question is where is all the math and physics inside the code? Do I have to look at the C++ code in order to see it? I think Hedgewars was originally programmed in C++ but the files are confusing be because of its size and the fact that it has several programming languages inside.

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• What kind of spam is this?

  - by SSilk

  I realize this is a pretty vague question, but I occasionally get spam messages through my contact form on a Drupal 6 site. The contact form does not have any anti-spam protection (i.e. math question). The messages I get are all very similar and just jumbled junk, like below, so I think they're all from the same source. Example: ylsaf0V bpsdfuxnhjjd, [url=http://wwgfsggzgyjyjm.com/]wwgrfgzrgsjyjm[/url], [link=http://xmgvyghcuufvb.com/]xmjyhvyjyfjirovb[/link], http://frgxmdghrgruhfc.com/ Anyway, I'm just wondering what the point of such a message is. All the links are dead, it's illegible, and it's not trying to sell me a product or get me to do anything, so I'm a bit perplexed. Is there any way to tell where they're coming from? And how concerned should I be? To be clear, I'm not asking how to avoid them, I realize just adding a simple math challenge or captcha would likely do the job.

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• Trouble with AABB collision response and physics

  - by WCM

  I have been racking my brain trying to figure out a problem I am having with physics and basic AABB collision response. I am fairly close as the physics are mostly right. Gravity feels good and movement is solid. The issue I am running into is that when I land on the test block in my project, I can jump off of it most of the time. If I repeatedly jump in place, I will eventually get stuck one or two pixels below the surface of the test block. If I try to jump, I can become free of the other block, but it will happen again a few jumps later. I feel like I am missing something really obvious with this. I have two functions that support the detection and function to return a vector for the overlap of the two rectangle bounding boxes. I have a single update method that is processing the physics and collision for the entity. I feel like I am missing something very simple, like an ordering of the physics vs. collision response handling. Any thoughts or help can be appreciated. I apologize for the format of the code, tis prototype code mostly. The collision detection function: public static bool Collides(Rectangle source, Rectangle target) { if (source.Right < target.Left || source.Bottom < target.Top || source.Left > target.Right || source.Top > target.Bottom) { return false; } return true; } The overlap function: public static Vector2 GetMinimumTranslation(Rectangle source, Rectangle target) { Vector2 mtd = new Vector2(); Vector2 amin = source.Min(); Vector2 amax = source.Max(); Vector2 bmin = target.Min(); Vector2 bmax = target.Max(); float left = (bmin.X - amax.X); float right = (bmax.X - amin.X); float top = (bmin.Y - amax.Y); float bottom = (bmax.Y - amin.Y); if (left > 0 || right < 0) return Vector2.Zero; if (top > 0 || bottom < 0) return Vector2.Zero; if (Math.Abs(left) < right) mtd.X = left; else mtd.X = right; if (Math.Abs(top) < bottom) mtd.Y = top; else mtd.Y = bottom; // 0 the axis with the largest mtd value. if (Math.Abs(mtd.X) < Math.Abs(mtd.Y)) mtd.Y = 0; else mtd.X = 0; return mtd; } The update routine (gravity = 0.001f, jumpHeight = 0.35f, moveAmount = 0.15f): public void Update(GameTime gameTime) { Acceleration.Y = gravity; Position += new Vector2((float)(movement * moveAmount * gameTime.ElapsedGameTime.TotalMilliseconds), (float)(Velocity.Y * gameTime.ElapsedGameTime.TotalMilliseconds)); Velocity.Y += Acceleration.Y; Vector2 previousPosition = new Vector2((int)Position.X, (int)Position.Y); KeyboardState keyboard = Keyboard.GetState(); movement = 0; if (keyboard.IsKeyDown(Keys.Left)) { movement -= 1; } if (keyboard.IsKeyDown(Keys.Right)) { movement += 1; } if (Position.Y + 16 > GameClass.Instance.GraphicsDevice.Viewport.Height) { Velocity.Y = 0; Position = new Vector2(Position.X, GameClass.Instance.GraphicsDevice.Viewport.Height - 16); IsOnSurface = true; } if (Collision.Collides(BoundingBox, GameClass.Instance.block.BoundingBox)) { Vector2 mtd = Collision.GetMinimumTranslation(BoundingBox, GameClass.Instance.block.BoundingBox); Position += mtd; Velocity.Y = 0; IsOnSurface = true; } if (keyboard.IsKeyDown(Keys.Space) && !previousKeyboard.IsKeyDown(Keys.Space)) { if (IsOnSurface) { Velocity.Y = -jumpHeight; IsOnSurface = false; } } previousKeyboard = keyboard; } This is also a full download to the project. https://www.box.com/s/3rkdtbso3xgfgc2asawy P.S. I know that I could do this with the XNA Platformer Starter Kit algo, but it has some deep flaws that I am going to try to live without. I'd rather go the route of collision response via an overlay function. Thanks for any and all insight!

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• Passive Income for a programmer : Teaching

  - by Victor

  While looking into passive income streams for someone with a Science/math/Engineering/Programming background, I ran into various ideas. I was looking to generate a passive income that would not take too much of an initiall learning curve. And it occurs to me that teaching/writing books/ on High School math/Physics/English is something I can do without a lot of prepwork. I am in Toronto . what are the average income opportunities for something like this? Where should I start looking?

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• What undergraduate course to choose for a mature programmer returning to study

  - by Dve

  I have been developing applications (mostly web-based) for almost 10 years now and have learnt pretty much everything I know through experience (and the internet!). I wouldn't call myself an advanced programmer, but I am quite proficient in several languages (C#, Javascript, Ruby, HTML/CSS etc) and spend a quite a bit of time working on personal projects and reading countless books & articles. I am looking to emigrate to Canada, hopefully Vancouver (im from the UK) and one way would be on a student visa, if I was going to be studying for a minimum of 2 years. Having never been to university or achieved anything higher than A-Levels I am quite tempted by this path. The thought of learning is more exciting to me now than it was 10 years ago! What would be people recommend as a good undergraduate course to take that would complement this career path? Would Math be beneficial, if so which area of Math? TL;DR What undergraduate course/area of study would complement 10 years of (mostly web-based) programming experience?

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• Bridge made out of blocks at an angle

  - by Pozzuh

  I'm having a bit of trouble with the math behind my project. I want the player to be able to select 2 points (vectors). With these 2 points a floor should be created. When these points are parallel to the x-axis it's easy, just calculate the amount of blocks needed by a simple division, loop through that amount (in x and y) and keep increasing the coordinate by the size of that block. The trouble starts when the 2 vectors aren't parallel to an axis, for example at an angle of 45 degrees. How do I handle the math behind this? If I wasn't completely clear, I made this awesome drawing in paint to demonstrate what I want to achieve. The 2 red dots would be the player selected locations. (The blocks indeed aren't square.) http://i.imgur.com/pzhFMEs.png.

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• Will taking two years off for school in a related field destroy a mid level development career?

  - by rsteckly

  Hi, I know some people have asked about getting back into programming after a break and this is a potential duplicate. I just am in a position where I can go back to school for a graduate degree in Stat/Applied Math. But I'm very worried about the impact it will have on my career and ability to find a job afterwards. I have 3 years experience in .NET on top of a couple of years in PHP. Right now, I'm a senior software engineer. Do you think taking two years off to do math is going to dramatically hurt my marketability?

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• I am new to game development, what do I need to know? [closed]

  - by farmdve

  I am unsure if this question is a duplicate, I hope it isn't. Are there any resources on the terminology when doing game development? Because, even if you tell me to learn some graphics API, how would I understand the things it does, if I am not well into the terminology(voxel,mesh,polygon,shading). What about the math that is involved in the game(geometry) or the concept of the gravity,collision detection in the game and their respective maths? I am very bad at math, never was good, because I have ADHD, but I won't give up just yet. I look at a game, and I see "textures", but how am I walking on them, how do they take substance so I don't fall off of them? And depth? This is what I need information about, not just a link to a library like SDL(which I have compiled under MinGW and MinGW-W64) and tell me to learn it and the cliché answer "start simple/small". I hope the question(s) are not too vague.

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• Calculating a circle or sphere along a vector

  - by Sparky

  Updated this post and the one at Math SE (http://math.stackexchange.com/questions/127866/calculating-a-circle-or-sphere-along-a-vector), hope this makes more sense. I previously posted a question (about half an hour ago) involving computations along line segments, but the question and discussion were really off track and not what I was trying to get at. I am trying to work with an FPS engine I am attempting to build in Java. The problem I am encountering is with hitboxing. I am trying to calculate whether or not a "shot" is valid. I am working with several approaches and any insight would be helpful. I am not a native speaker of English nor skilled in Math so please bear with me. Player position is at P0 = (x0,y0,z0), Enemy is at P1 = (x1,y1,z1). I can of course compute the distance between them easily. The target needs a "hitbox" object, which is basically a square/rectangle/mesh either in front of, in, or behind them. Here are the solutions I am considering: I have ruled this out...doesn't seem practical. [Place a "hitbox" a small distance in front of the target. Then I would be able to find the distance between the player and the hitbox, and the hitbox and the target. It is my understanding that you can compute a circle with this information, and I could simply consider any shot within that circle a "hit". However this seems not to be an optimal solution, because it requires you to perform a lot of calculations and is not fully accurate.] Input, please! Place the hitbox "in" the player. This seems like the better solution. In this case what I need is a way to calculate a circle along the vector, at whatever position I wish (in this case, the distance between the two objects). Then I can pick some radius that encompasses the whole player, and count anything within this area a "hit". I am open to your suggestions. I'm trying to do this on paper and have no familiarity with game engines. If any software folk out there think I'm doing this the hard way, I'm open to help! Also - Anyone with JOGL/LWJGL experience, please chime in. Is this making sense?

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• Circular movement - eliminating speed ups near Y = 0

  - by Fibericon

  I have a basic algorithm to rotate an enemy around a 200 unit radius circle with center 0. This is how I'm achieving that: if (position.Y <= 0 && position.X > -200) { position.X -= 2; position.Y = 0 - (float)Math.Sqrt((200 * 200) - (position.X * position.X)); } else { position.X += 2; position.Y = (float)Math.Sqrt((200 * 200) - (position.X * position.X)); } It does work, and I've ensured that at no point does either X or Y equal NaN. However, when Y approaches 0, it seems to go significantly faster. This surprises me, because the Y values are locked to the X, which is being incremented by a steady amount. What can I do to smooth the speed?

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• Actionscript - Dropping Multiple Objects Using an Array?

  - by Eratosthenes

  I'm trying to get these fireBalls to drop more often, im not sure if im using Math.random correctly also, for some reason I'm getting a null reference because I think the fireBalls array waits for one to leave the stage before dropping another one? this is the relevant code: var sun:Sun=new Sun var fireBalls:Array=new Array() var left:Boolean; function onEnterFrame(event:Event){ if (left) { sun.x = sun.x - 15; }else{ sun.x = sun.x + 15; } if (fireBalls.length>0&&fireBalls[0].y>stage.stageHeight){ // Fireballs exit stage removeChild(fireBalls[0]); fireBalls.shift(); } for (var j:int=0; j<fireBalls.length; j++){ fireBalls[j].y=fireBalls[j].y+15; if (fireBalls[j].y>stage.stageHeight-fireBall.width/2){ } } if (Math.random()<.2){ // Fireballs shooting from Sun var fireBall:FireBall=new FireBall; fireBall.x=sun.x; addChild(fireBall); fireBalls.push(fireBall); } }

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• SlimDX: Lightning problem with Direct3D9

  - by Spi1988

  I am creating a simple application to get familiar with SlimDX library. I found some code written in MDX and I'm trying to convert it to run on SlimDX. I am having some problems with the light because everything is being shown as black. The code is: public partial class DirectTest : Form { private Device device= null; private float angle = 0.0f; Light light = new Light(); public DirectTest() { InitializeComponent(); this.Size = new Size(800, 600); this.SetStyle(ControlStyles.AllPaintingInWmPaint | ControlStyles.Opaque, true); } /// <summary> /// We will initialize our graphics device here /// </summary> public void InitializeGraphics() { PresentParameters pres_params = new PresentParameters() { Windowed = true, SwapEffect = SwapEffect.Discard }; device = new Device(new Direct3D(), 0, DeviceType.Hardware, this.Handle, CreateFlags.SoftwareVertexProcessing, pres_params); } private void SetupCamera() { device.SetRenderState(RenderState.CullMode, Cull.None); device.SetTransform(TransformState.World, Matrix.RotationAxis(new Vector3(angle / ((float)Math.PI * 2.0f), angle / ((float)Math.PI * 4.0f), angle / ((float)Math.PI * 6.0f)), angle / (float)Math.PI)); angle += 0.1f; device.SetTransform(TransformState.Projection, Matrix.PerspectiveFovLH((float)Math.PI / 4, this.Width / this.Height, 1.0f, 100.0f)); device.SetTransform(TransformState.View, Matrix.LookAtLH(new Vector3(0, 0, 5.0f), new Vector3(), new Vector3(0, 1, 0))); device.SetRenderState(RenderState.Lighting, false); } protected override void OnPaint(System.Windows.Forms.PaintEventArgs e) { device.Clear(ClearFlags.Target | ClearFlags.ZBuffer, Color.CornflowerBlue, 1.0f, 0); SetupCamera(); CustomVertex.PositionColored[] verts = new CustomVertex.PositionColored[3]; verts[0].Position = new Vector3(0.0f, 1.0f, 1.0f); verts[0].Normal = new Vector3(0.0f, 0.0f, -1.0f); verts[0].Color = System.Drawing.Color.White.ToArgb(); verts[1].Position = new Vector3(-1.0f, -1.0f, 1.0f); verts[1].Normal = new Vector3(0.0f, 0.0f, -1.0f); verts[1].Color = System.Drawing.Color.White.ToArgb(); verts[2].Position = new Vector3(1.0f, -1.0f, 1.0f); verts[2].Normal = new Vector3(0.0f, 0.0f, -1.0f); verts[2].Color = System.Drawing.Color.White.ToArgb(); light.Type = LightType.Point; light.Position = new Vector3(); light.Diffuse = System.Drawing.Color.White; light.Attenuation0 = 0.2f; light.Range = 10000.0f; device.SetLight(0, light); device.EnableLight(0, true); device.BeginScene(); device.VertexFormat = CustomVertex.PositionColored.format; device.DrawUserPrimitives<CustomVertex.PositionColored>(PrimitiveType.TriangleList, 1, verts); device.EndScene(); device.Present(); this.Invalidate(); } } } The Vertex Format that I am using is the following [StructLayout(LayoutKind.Sequential)] public struct PositionNormalColored { public Vector3 Position; public int Color; public Vector3 Normal; public static readonly VertexFormat format = VertexFormat.Diffuse | VertexFormat.Position | VertexFormat.Normal; } Any suggestions on what the problem might be? Thanks in Advance

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• Common Mercator Projection formulas for Google Maps not working correctly

  - by Tom Halladay

  I am building a Tile Overlay server for Google maps in C#, and have found a few different code examples for calculating Y from Latitude. After getting them to work in general, I started to notice certain cases where the overlays were not lining up properly. To test this, I made a test harness to compare Google Map's Mercator LatToY conversion against the formulas I found online. As you can see below, they do not match in certain cases. Case #1 Zoomed Out: The problem is most evident when zoomed out. Up close, the problem is barely visible. Case #2 Point Proximity to Top & Bottom of viewing bounds: The problem is worse in the middle of the viewing bounds, and gets better towards the edges. This behavior can negate the behavior of Case #1 The Test: I created a google maps page to display red lines using the Google Map API's built in Mercator conversion, and overlay this with an image using the reference code for doing Mercator conversion. These conversions are represented as black lines. Compare the difference. The Results: Check out the top-most and bottom-most lines: The problem gets visually larger but numerically smaller as you zoom in: And it all but disappears at closer zoom levels, regardless of screen orientation. The Code: Google Maps Client Side Code: var lat = 0; for (lat = -80; lat <= 80; lat += 5) { map.addOverlay(new GPolyline([new GLatLng(lat, -180), new GLatLng(lat, 0)], "#FF0033", 2)); map.addOverlay(new GPolyline([new GLatLng(lat, 0), new GLatLng(lat, 180)], "#FF0033", 2)); } Server Side Code: Tile Cutter : http://mapki.com/wiki/Tile_Cutter OpenStreetMap Wiki : http://wiki.openstreetmap.org/wiki/Mercator protected override void ImageOverlay_ComposeImage(ref Bitmap ZipCodeBitMap) { Graphics LinesGraphic = Graphics.FromImage(ZipCodeBitMap); Int32 MapWidth = Convert.ToInt32(Math.Pow(2, zoom) * 255); Point Offset = Cartographer.Mercator2.toZoomedPixelCoords(North, West, zoom); TrimPoint(ref Offset, MapWidth); for (Double lat = -80; lat <= 80; lat += 5) { Point StartPoint = Cartographer.Mercator2.toZoomedPixelCoords(lat, -179, zoom); Point EndPoint = Cartographer.Mercator2.toZoomedPixelCoords(lat, -1, zoom); TrimPoint(ref StartPoint, MapWidth); TrimPoint(ref EndPoint, MapWidth); StartPoint.X = StartPoint.X - Offset.X; EndPoint.X = EndPoint.X - Offset.X; StartPoint.Y = StartPoint.Y - Offset.Y; EndPoint.Y = EndPoint.Y - Offset.Y; LinesGraphic.DrawLine(new Pen(Color.Black, 2), StartPoint.X, StartPoint.Y, EndPoint.X, EndPoint.Y); LinesGraphic.DrawString( lat.ToString(), new Font("Verdana", 10), new SolidBrush(Color.Black), new Point( Convert.ToInt32((width / 3.0) * 2.0), StartPoint.Y)); } } protected void TrimPoint(ref Point point, Int32 MapWidth) { point.X = Math.Max(point.X, 0); point.X = Math.Min(point.X, MapWidth - 1); point.Y = Math.Max(point.Y, 0); point.Y = Math.Min(point.Y, MapWidth - 1); } So, Anyone ever experienced this? Dare I ask, resolved this? Or simply have a better C# implementation of Mercator Project coordinate conversion? Thanks!

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• I'm trying to make lots of the same object appear randomly on the screen subject to conditions and k

  - by Katsideswide

  Hi! A good friend recommended this site to me, it looks really useful! I'm a bit of a shameless noob at actionscript and after 3 days of tutorials and advice I've hit a brick wall. I've managed to get a sensor attached to an arduino talking to flash using something called AS3glue. it works, when i set up a trace("leaf") for the contition that the sensor reads 0, i get a printout of the word "leaf". however i want the program to make a graphic appear on the screen when this condition is met, not just trace something. I'm trying to get the program to generate a library object called "Enemy" on the screen at a random position each time the conditions are met. It's called enemy because I was following a game tutorial...actually it's a drawing of a leaf. Here's the bit of the code which is causing me problems: var army:Array; var enemy:Enemy; function AvoiderGame() { army = new Array(); var newEnemy = new Enemy( 100, 100 ); army.push( newEnemy ); addChild( newEnemy ); } function timerEvent(event:Event):void { if (a.getAnalogData(0) ==0 && a.getAnalogData(0) != this.lastposition){ trace("leaf"); var randomX:Number = (Math.random() * 200) + 100; var randomY:Number = (Math.random() * 150) + 50; var newEnemy = new Enemy( randomX, randomY); army.push( newEnemy ); addChild( newEnemy ); } else if (a.getAnalogData(0) == 0) { //don't trace anything } else { //don't trace anything } this.lastposition = a.getAnalogData(0); //afterwards, set the position to be the new lastposition and repeat. } I've imported "import flash.display.MovieClip;" and the code for the Enemy class looks like this: package { import flash.display.MovieClip; public class Enemy extends MovieClip { public function Enemy( startX:Number, startY:Number ) { x = startX; y = startY; } } } Here's my error. I've tried googling, it seems like a pretty general error: TypeError: Error #1009: Cannot access a property or method of a null object reference. at as3glue_program_fla::MainTimeline/timerEvent() at flash.utils::Timer/_timerDispatch() at flash.utils::Timer/tick() I've made sure that the "Enemy" object is exported for AS3. I'm going for something like this when it's programmed in AS2: leafCounter = 0; //set the counter to 0 counter.swapDepths(1000); //puts the counter on top of pretty much anything, unless you make more than 1000 leaves! counter.textbox.text = 0; //shows "0" in the text box in the "counter" movie clip this.onMouseDown = function() { //triggers when the mouse is clicked this.attachMovie("Leaf","Leaf"+leafCounter,leafCounter,{_x:Math.random()*Stage.width,_y:Math.random()*Stage.height,_rotation:Math.random()*360}); //adds a leaf to rthe stage with a random position and random rotation leafCounter++; //adds 1 to the leaf counter counter.textbox.text = leafCounter; //shows that number in the text box } I'm sure it must be a simple error, I can get the logic working when it just traces something on the screen but i can't get it to generate an "enemy" Any help or hints would be really useful! I know this is a bit of a ham-fisted job of altering existing code.

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• onDraw() triggered but results don't show

  - by Don

  I have the following routine in a subclass of view: It calculates an array of points that make up a line, then erases the previous lines, then draws the new lines (impact refers to the width in pixels drawn with multiple lines). The line is your basic bell curve, squeezed or stretched by variance and x-factor. Unfortunately, nothing shows on the screen. A previous version with drawPoint() and no array worked, and I've verified the array contents are being loaded correctly, and I can see that my onDraw() is being triggered. Any ideas why it might not be drawn? Thanks in advance! protected void drawNewLine( int maxx, int maxy, Canvas canvas, int impact, double variance, double xFactor, int color) { // impact = 2 to 8; xFactor between 4 and 20; variance between 0.2 and 5 double x = 0; double y = 0; int cx = maxx / 2; int cy = maxy / 2; int mu = cx; int index = 0; points[maxx<<1][1] = points[maxx<<1][0]; for (x = 0; x < maxx; x++) { points[index][1] = points[index][0]; points[index][0] = (float) x; Log.i(DEBUG_TAG, "x: " + x); index++; double root = 1.0 / (Math.sqrt(2 * Math.PI * variance)); double exponent = -1.0 * (Math.pow(((x - mu)/maxx*xFactor), 2) / (2 * variance)); double ePow = Math.exp(exponent); y = Math.round(cy * root * ePow); points[index][1] = points[index][0]; points[index][0] = (float) (maxy - y - OFFSET); index++; } points[maxx<<1][0] = (float) impact; for (int line = 0; line < points[maxx<<1][1]; line++) { for (int pt = 0; pt < (maxx<<1); pt++) { pointsToPaint[pt] = points[pt][1]; } for (int skip = 1; skip < (maxx<<1); skip = skip + 2) pointsToPaint[skip] = pointsToPaint[skip] + line; myLinePaint.setColor(Color.BLACK); canvas.drawLines(pointsToPaint, bLinePaint); // draw over old lines w/blk } for (int line = 0; line < points[maxx<<1][0]; line++) { for (int pt = 0; pt < maxx<<1; pt++) { pointsToPaint[pt] = points[pt][0]; } for (int skip = 1; skip < maxx<<1; skip = skip + 2) pointsToPaint[skip] = pointsToPaint[skip] + line; myLinePaint.setColor(color); canvas.drawLines(pointsToPaint, myLinePaint); / new color } } update: Replaced the drawLines() with drawPoint() in loop, still no joy for (int p = 0; p<pointsToPaint.length; p = p + 2) { Log.i(DEBUG_TAG, "x " + pointsToPaint[p] + " y " + pointsToPaint[p+1]); canvas.drawPoint(pointsToPaint[p], pointsToPaint[p+1], myLinePaint); } /// canvas.drawLines(pointsToPaint, myLinePaint);

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• Path to background in servlet

  - by kapil chhattani

  //the below line is the element of my HTML form which renders the image sent by the servlet written further below. <img style="margin-left:91px; margin-top:-6px;" class="image" src="http://www.abcd.com/captchaServlet"> I generate a captcha code using the following code in java. public class captchaServlet extends HttpServlet { protected void processRequest(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { int width = 150; int height = 50; int charsToPrint = 6; String elegibleChars = "ABCDEFGHJKLMPQRSTUVWXYabcdefhjkmnpqrstuvwxy1234567890"; char[] chars = elegibleChars.toCharArray(); StringBuffer finalString = new StringBuffer(); for ( int i = 0; i < charsToPrint; i++ ) { double randomValue = Math.random(); int randomIndex = (int) Math.round(randomValue * (chars.length - 1)); char characterToShow = chars[randomIndex]; finalString.append(characterToShow); } System.out.println(finalString); BufferedImage bufferedImage = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB); Graphics2D g2d = bufferedImage.createGraphics(); Font font = new Font("Georgia", Font.BOLD, 18); g2d.setFont(font); RenderingHints rh = new RenderingHints( RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON); rh.put(RenderingHints.KEY_RENDERING, RenderingHints.VALUE_RENDER_QUALITY); g2d.setRenderingHints(rh); GradientPaint gp = new GradientPaint(0, 0, Color.BLUE, 0, height/2, Color.black, true); g2d.setPaint(gp); g2d.fillRect(0, 0, width, height); g2d.setColor(new Color(255, 255, 0)); Random r = new Random(); int index = Math.abs(r.nextInt()) % 5; char[] data=new String(finalString).toCharArray(); String captcha = String.copyValueOf(data); int x = 0; int y = 0; for (int i=0; i<data.length; i++) { x += 10 + (Math.abs(r.nextInt()) % 15); y = 20 + Math.abs(r.nextInt()) % 20; g2d.drawChars(data, i, 1, x, y); } g2d.dispose(); response.setContentType("image/png"); OutputStream os = response.getOutputStream(); ImageIO.write(bufferedImage, "png", os); os.close(); } protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { processRequest(request, response); } protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { processRequest(request, response); } } But in the above code background is also generated using the setPaint menthod I am guessing. I want the background to be some image from my local machine whoz URL i should be able to mention like URL url=this.getClass().getResource("Desktop/images.jpg"); BufferedImage bufferedImage = ImageIO.read(url); I am just writing the above two lines for making the reader understand better what the issue is. Dont want to use the exact same commands. All I want is the the background of the captcha code generated should be an image of my choice.

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• Why jquery have problem with onbeforeprint even?

  - by Cesar Lopez

  Hi all, I have the following function. $(function() { $(".sectionHeader:gt(0)").click(function() { $(this).next(".fieldset").slideToggle("fast"); }); $("img[alt='minimize']").click(function(e) { $(this).closest("table").next(".fieldset").slideUp("fast"); e.stopPropagation(); return false; }); $("img[alt='maximize']").click(function(e) { $(this).closest("table").next(".fieldset").slideDown("fast"); e.stopPropagation(); return false; }); }); <script type="text/javascript"> window.onbeforeprint = expandAll; function expandAll(){ $(".fieldset:gt(0)").slideDown("fast"); } </script> For this html <table class="sectionHeader" ><tr ><td>Heading 1</td></tr></table> <div style="display:none;" class="fieldset">Content 1</div> <table class="sectionHeader" ><tr ><td>Heading 2</td></tr></table> <div style="display:none;" class="fieldset">Content 2</div> I have several div class="fieldset" over the page, but when I do print preview or print, I can see all divs sliding down before opening the print preview or printing but on the actual print preview or print out they are all collapse. I would appreciate if anyone comes with a solution for this. Anyone have any idea why is this or how to fix it? Thanks. PS:Using a does not work either ( I assume because jquery using toggle) and its not the kind of question I am looking for.

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• Common Table Expressions slow when using a table variable

  - by Phil Haselden

  I have been experimenting with the following (simplified) CTE. When using a table variable () the query runs for minutes before I cancel it. Any of the other commented out methods return in less than a second. If I replace the whole WHERE clause with an INNER JOIN it is fast as well. Any ideas why using a table variable would run so slowly? FWIW: The database contains 2.5 million records and the inner query returns 2 records. CREATE TABLE #rootTempTable (RootID int PRIMARY KEY) INSERT INTO #rootTempTable VALUES (1360); DECLARE @rootTableVar TABLE (RootID int PRIMARY KEY); INSERT INTO @rootTableVar VALUES (1360); WITH My_CTE AS ( SELECT ROW_NUMBER() OVER(ORDER BY d.DocumentID) rownum, d.DocumentID, d.Title FROM [Document] d WHERE d.LocationID IN ( SELECT LocationID FROM Location JOIN @rootTableVar rtv ON Location.RootID = rtv.RootID -- VERY SLOW! --JOIN #rootTempTable tt ON Location.RootID = tt.RootID -- Fast --JOIN (SELECT 1360 as RootID) AS rt ON Location.RootID = rt.RootID -- Fast --WHERE RootID = 1360 -- Fast ) ) SELECT * FROM My_CTE WHERE (rownum > 0) AND (rownum <= 100) ORDER BY rownum

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• JQuery not Working in chrome?

  - by Pete Herbert Penito

  Hi everyone! I have some code here which works perfectly in firefox but not in chrome or IE, my javascript is thus ` $(document).ready(function() { $("#clientLoginPop").show(); $("#clientLoginPop").animate({"left": "-=400px"}, "fast"); }); $("#clientLoginCloseLink").click(function () { $("#clientLoginPop").animate({"left": "+=400px"}, "fast"); }); $("#contactUsPopLink").click(function () { $("#contactUsPop").show(); $("#contactUsPop").animate({"left": "-=437px"}, "fast"); }); $("#contactUsClose").click(function () { $("#contactUsPop").animate({"left": "+=474px"}, "fast"); }); }); ` and finally the css of the div looks like this, i think rather importantly it's aligned to the right of the browser: (the client login div looks similar just a different height) ` #contactUsPop { width:437px; right:-437px; margin-top:220px; position:fixed; height:217px; background-color:white; z-index:2; } ` so what happens in firefox is the div animates to the left and then when it closes it moves back to the right. when in chrome the div doesn't seem to pop up at all? the URL of the site is this: http://clearcreativegroup.com/devcorner/clear3/ the tabs are on the right hand side of the browser, any advice would help tons, thank you!

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