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• Why does my Opengl es android testbed app not render anything besides a red screen?

  - by nathan

  For some reason my code here (this is the entire thing) doesnt actually render anything besides a red screen.. can anyone tell me why? package com.ntu.way2fungames.earth.testbed; import java.nio.FloatBuffer; import javax.microedition.khronos.egl.EGLConfig; import javax.microedition.khronos.opengles.GL10; import android.app.Activity; import android.content.Context; import android.opengl.GLSurfaceView; import android.opengl.GLSurfaceView.Renderer; import android.os.Bundle; public class projectiles extends Activity { GLSurfaceView lGLView; Renderer lGLRenderer; float projectilesX[]= new float[5001]; float projectilesY[]= new float[5001]; float projectilesXa[]= new float[5001]; float projectilesYa[]= new float[5001]; float projectilesTheta[]= new float[5001]; float projectilesSpeed[]= new float[5001]; private static FloatBuffer drawBuffer; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); SetupProjectiles(); Context mContext = this.getWindow().getContext(); lGLView= new MyView(mContext); lGLRenderer= new MyRenderer(); lGLView.setRenderer(lGLRenderer); setContentView(lGLView); } private void SetupProjectiles() { int i=0; for (i=5000;i>0;i=i-1){ projectilesX[i] = 240; projectilesY[i] = 427; float theta = (float) ((i/5000)*Math.PI*2); projectilesXa[i] = (float) Math.cos(theta); projectilesYa[i] = (float) Math.sin(theta); projectilesTheta[i]= theta; projectilesSpeed[i]= (float) (Math.random()+1); } } public class MyView extends GLSurfaceView{ public MyView(Context context) { super(context); // TODO Auto-generated constructor stub } } public class MyRenderer implements Renderer{ private float[] projectilecords = new float[] { .0f, .5f, 0, -.5f, 0f, 0, .5f, 0f, 0, 0, -5f, 0, }; @Override public void onDrawFrame(GL10 gl) { gl.glClear(GL10.GL_COLOR_BUFFER_BIT); gl.glMatrixMode(GL10.GL_MODELVIEW); //gl.glLoadIdentity(); gl.glEnableClientState(GL10.GL_VERTEX_ARRAY); for (int i=5000;i>4500;i=i-1){ //drawing section gl.glLoadIdentity(); gl.glColor4f(.9f, .9f,.9f,.9f); gl.glTranslatef(projectilesY[i], projectilesX[i],1); gl.glVertexPointer(3, GL10.GL_FLOAT, 0, drawBuffer); gl.glDrawArrays(GL10.GL_TRIANGLE_STRIP, 0, 12); //physics section projectilesX[i]=projectilesX[i]+projectilesXa[i]; projectilesY[i]=projectilesY[i]+projectilesYa[i]; } gl.glDisableClientState(GL10.GL_VERTEX_ARRAY); } @Override public void onSurfaceChanged(GL10 gl, int width, int height) { if (height == 0) height = 1; // draw on the entire screen gl.glViewport(0, 0, width, height); // setup projection matrix gl.glMatrixMode(GL10.GL_PROJECTION); gl.glLoadIdentity(); gl.glOrthof(0,width,height,0, -100, 100); } @Override public void onSurfaceCreated(GL10 gl, EGLConfig arg1) { gl.glShadeModel(GL10.GL_SMOOTH); gl.glClearColor(1f, .01f, .01f, 1f); gl.glClearDepthf(1.0f); gl.glEnable(GL10.GL_DEPTH_TEST); gl.glDepthFunc(GL10.GL_LEQUAL); gl.glHint(GL10.GL_PERSPECTIVE_CORRECTION_HINT, GL10.GL_NICEST); drawBuffer = FloatBuffer.wrap(projectilecords); } } }

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• Algorithm for dragging objects on a fixed grid

  - by FlyingStreudel

  Hello, I am working on a program for the mapping and playing of the popular tabletop game D&D :D Right now I am working on getting the basic functionality like dragging UI elements around, snapping to the grid and checking for collisions. Right now every object when released from the mouse immediately snaps to the nearest grid point. This causes an issue when something like a player object snaps to a grid point that has a wall -or other- adjacent. So essentially when the player is dropped they wind up with some of the wall covering them. This is fine and working as intended, however the problem is that now my collision detection is tripped whenever you try to move this player because its sitting underneath a wall and because of this you cant drag the player anymore. Here is the relevant code: void UIObj_MouseMove(object sender, MouseEventArgs e) { blocked = false; if (dragging) { foreach (UIElement o in ((Floor)Parent).Children) { if (o.GetType() != GetType() && o.GetType().BaseType == typeof(UIObj) && Math.Sqrt(Math.Pow(((UIObj)o).cX - cX, 2) + Math.Pow(((UIObj)o).cY - cY, 2)) < Math.Max(r.Height + ((UIObj)o).r.Height, r.Width + ((UIObj)o).r.Width)) { double Y = e.GetPosition((Floor)Parent).Y; double X = e.GetPosition((Floor)Parent).X; Geometry newRect = new RectangleGeometry(new Rect(Margin.Left + (X - prevX), Margin.Top + (Y - prevY), Margin.Right + (X - prevX), Margin.Bottom + (Y - prevY))); GeometryHitTestParameters ghtp = new GeometryHitTestParameters(newRect); VisualTreeHelper.HitTest(o, null, new HitTestResultCallback(MyHitTestResultCallback), ghtp); } } if (!blocked) { Margin = new Thickness(Margin.Left + (e.GetPosition((Floor)Parent).X - prevX), Margin.Top + (e.GetPosition((Floor)Parent).Y - prevY), Margin.Right + (e.GetPosition((Floor)Parent).X - prevX), Margin.Bottom + (e.GetPosition((Floor)Parent).Y - prevY)); InvalidateVisual(); } prevX = e.GetPosition((Floor)Parent).X; prevY = e.GetPosition((Floor)Parent).Y; cX = Margin.Left + r.Width / 2; cY = Margin.Top + r.Height / 2; } } internal virtual void SnapToGrid() { double xPos = Margin.Left; double yPos = Margin.Top; double xMarg = xPos % ((Floor)Parent).cellDim; double yMarg = yPos % ((Floor)Parent).cellDim; if (xMarg < ((Floor)Parent).cellDim / 2) { if (yMarg < ((Floor)Parent).cellDim / 2) { Margin = new Thickness(xPos - xMarg, yPos - yMarg, xPos - xMarg + r.Width, yPos - yMarg + r.Height); } else { Margin = new Thickness(xPos - xMarg, yPos - yMarg + ((Floor)Parent).cellDim, xPos - xMarg + r.Width, yPos - yMarg + ((Floor)Parent).cellDim + r.Height); } } else { if (yMarg < ((Floor)Parent).cellDim / 2) { Margin = new Thickness(xPos - xMarg + ((Floor)Parent).cellDim, yPos - yMarg, xPos - xMarg + ((Floor)Parent).cellDim + r.Width, yPos - yMarg + r.Height); } else { Margin = new Thickness(xPos - xMarg + ((Floor)Parent).cellDim, yPos - yMarg + ((Floor)Parent).cellDim, xPos - xMarg + ((Floor)Parent).cellDim + r.Width, yPos - yMarg + ((Floor)Parent).cellDim + r.Height); } } } Essentially I am looking for a simple way to modify the existing code to allow the movement of a UI element that has another one sitting on top of it. Thanks!

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• How can I determine if an image has loaded, using Javascript/jQuery?

  - by Kip

  I'm writing some Javascript to resize the large image to fit into the user's browser window. (I don't control the size of the source images unfortunately.) So something like this would be in the HTML: <img id="photo" src="a_really_big_file.jpg" alt="this is some alt text" title="this is some title text" /> Is there a way for me to determine if the src image in an img tag has been downloaded? I need this because I'm running into a problem if $(document).ready() is executed before the browser has loaded the image. $("#photo").width() and $("#photo").height() will return the size of the placeholder (the alt text). In my case this is something like 134 x 20. Right now I'm just checking if the photo's height is less than 150, and assuming that if so it is just alt text. But this is quite a hack, and it would break if a photo is less than 150 pixels tall (not likely in my particular case), or if the alt text is more than 150 pixels tall (could possibly happen on a small browser window). Edit: For anyone wanting to see the code: $(function() { var REAL_WIDTH = $("#photo").width(); var REAL_HEIGHT = $("#photo").height(); $(window).resize(adjust_photo_size); adjust_photo_size(); function adjust_photo_size() { if(REAL_HEIGHT < 150) { REAL_WIDTH = $("#photo").width(); REAL_HEIGHT = $("#photo").height(); if(REAL_HEIGHT < 150) { //image not loaded.. try again in a quarter-second setTimeout(adjust_photo_size, 250); return; } } var new_width = . . . ; var new_height = . . . ; $("#photo").width(Math.round(new_width)); $("#photo").height(Math.round(new_height)); } }); Update: Thanks for the suggestions. There is a risk of the event not being fired if I set a callback for the $("#photo").load event, so I have defined an onLoad event directly on the image tag. For the record, here is the code I ended up going with: <img id="photo" onload="photoLoaded();" src="a_really_big_file.jpg" alt="this is some alt text" title="this is some title text" /> Then in Javascript: //This must be outside $() because it may get called first var isPhotoLoaded = false; function photoLoaded() { isPhotoLoaded = true; } $(function() { //Hides scrollbars, so we can resize properly. Set with JS instead of // CSS so that page doesn't break with JS disabled. $("body").css("overflow", "hidden"); var REAL_WIDTH = -1; var REAL_HEIGHT = -1; $(window).resize(adjust_photo_size); adjust_photo_size(); function adjust_photo_size() { if(!isPhotoLoaded) { //image not loaded.. try again in a quarter-second setTimeout(adjust_photo_size, 250); return; } else if(REAL_WIDTH < 0) { //first time in this function since photo loaded REAL_WIDTH = $("#photo").width(); REAL_HEIGHT = $("#photo").height(); } var new_width = . . . ; var new_height = . . . ; $("#photo").width(Math.round(new_width)); $("#photo").height(Math.round(new_height)); } });

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• C# slowdown while creating a bitmap - calculating distances from a large List of places for each pixel

  - by user576849

  I'm creating a graphic of the glow of lights above a geographic location based upon Walkers Law: Skyglow=0.01*Population*DistanceFromCenter^-2.5 I have a CSV file of places with 66,000 records using 5 fields (id,name,population,latitude,longitude), parsed on the FormLoad event and stored it in: List<string[]> placeDataList Then I set up nested loops to fill in a bitmap using SetPixel. For each pixel on the bitmap, which represents a coordinate on a map (latitude and longitude), the program loops through placeDataList – calculating the distance from that coordinate (pixel) to each place record. The distance (along with population) is used in a calculation to find how much cumulative sky glow is contributed to the coordinate from each place record. So, for every pixel, 66,000 distance calculations must be made. The problem is, this is predictably EXTREMELY slow – on the order of one line of pixels per 30 seconds or so on a 320 pixel wide image. This is unrelated to SetPixel, which I know is also slow, because the speed is similarly slow when adding the distance calculation results to an array. I don’t actually need to test all 66,000 records for every pixel, only the records within 150 miles (i.e. no skyglow is contributed to a coordinate from a small town 3000 miles away). But to find which records are within 150 miles of my coordinate I would still need to loop through all the records for each pixel. I can't use a smaller number of records because all 66,000 places contribute to skyglow for SOME coordinate in my map as it loops. This seems like a Catch-22, so I know there must be a better method out there. Like I mentioned, the slowdown is related to how many calculations I’m making per pixel, not anything to do with the bitmap. Any suggestions? private void fillPixels(int width) { Color pixelColor; int pixel_w = width; int pixel_h = (int)Math.Floor((width * 0.424088664)); Bitmap bmp = new Bitmap(pixel_w, pixel_h); for (int i = 0; i < pixel_h; i++) for (int j = 0; j < pixel_w; j++) { pixelColor = getPixelColor(i, j); bmp.SetPixel(j, i, pixelColor); } bmp.Save("Nightfall", System.Drawing.Imaging.ImageFormat.Jpeg); pictureBox1.Image = bmp; MessageBox.Show("Done"); } private Color getPixelColor(int height, int width) { int c; double glow,d,cityLat,cityLon,cityPop; double testLat, testLon; int size_h = (int)Math.Floor((size_w * 0.424088664)); ; testLat = (height * (24.443136 / size_h)) + 24.548874; testLon = (width * (57.636853 / size_w)) -124.640767; glow = 0; for (int i = 0; i < placeDataList.Count; i++) { cityPop=Convert.ToDouble(placeDataList[i][2]); cityLat=Convert.ToDouble(placeDataList[i][3]); cityLon=Convert.ToDouble(placeDataList[i][4]); d = distance(testLat, testLon, cityLat, cityLon,"M"); if(d<150) glow = glow+(0.01 * cityPop * Math.Pow(d, -2.5)); } if (glow >= 1) glow=1; c = (int)Math.Ceiling(glow * 255); return Color.FromArgb(c, c, c); }

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• displaying python's autodoc to the user (python 3.3)

  - by Plotinus

  I'm writing a simple command line math game, and I'm using python's autodoc for my math algorithms to help me remember, for example, what a proth number is while i'm writing the algorithm, but later on I'll want to tell that information to the user as well, so they'll know what the answer was. So, for example I have: def is_proth(): """Proth numbers and numbers that fit the formula k×2^n + 1, where k are odd positive integers, and 2^n > k.""" [snip] return proths and then I tried to make a dictionary, like so: definitions = {"proths" : help(is_proth)} But it doesn't work. It prints this when I start the program, one for each item in the dictionary, and then it errors out on one of them that returns a set. And anyway, I don't want it displayed to the user until after they've played the game. Help on function is_proth in module __main__: is_proth() Proth numbers and numbers that fit the formula k×2^n + 1, where k are odd positive integers, and 2^n > k. (END) I understand the purpose of autodoc is more for helping programmers who are calling a function than for generating userdoc, but it seems inefficient to have to type out the definition of what a proth number is twice, once in a comment to help me remember what an algorithm does and then once to tell the user the answer to the game they were playing after they've won or lost.

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• What's your experience with female programmers?

  - by Rachel

  Let me start by saying I'm female, but every single other female programmer I've known has been pretty terrible. The extent of their knowledge seems to be copy/paste and modify some values. Quite often they don't even try to learn new concepts, or understand what they're doing. I'm not saying good female programmers aren't out there, just that the ratio of good/bad programmers seems much worse then males. Perhaps its because everyone feels they have to give female programmers a chance to prove they are not biased? Or is this just me?? What has your experiences been with them? UPDATE: Just want to say thanks for all the responses. I've learned some interesting things and am happy to know that female programmers have such support :) My experience has been very limited with them but all bad, and I agree that it is probably due to my small sample size (around 5). I wasn't trying to be sexist with such a question, I just wanted to find out if it was really that abnormal to be a female programmer. I'm abnormal about a lot of things you'd expect from a female... I play video games in most of my spare time, I liked Math so much I completed my entire math book during christmas break one year (What can I say, I found the subject interesting), I'm not very social, I dislike shopping, I only have 2 pairs of shoes, my significant other doesn't work but does all the housework/laundry/etc... but anyways, thanks :)

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• Silverlight Cream for April 06, 2010 -- #832

  - by Dave Campbell

  In this Issue: Alex van Beek, Gill Cleeren, SilverlightShow, Michael Sync, Rénald Nollet, Charles Petzold, The-Oliver, and Max Paulousky. Shoutouts: Denislav Savkov of SilverlightShow ported his Slider control to WP7: Windows Phone 7 Series Sample Image Viewer SilverlightShow interview: The Silverlight Tour - what, where and why. Interview with one of the Tour organizers Laurent Duveau From SilverlightCream.com: Silverlight 4: using the VisualStateManager for state animations with MVVM Alex van Beek has an approach to resolving the MVVM issue of Animations without keeping a reference to the ViewModel by way of VisualStateManager Leveraging the ASP.NET Membership in Silverlight Gill Cleeren's post at SilverlightShow talks about using ASP.NET authentication inside your Silverlight making membership not only something you know and understand, but now the transition from your ASP.NET apps to Silverlight is simple as well. Windows Phone 7 Series RSS reader SilverlightShow has a demo RSS Reader for WP7 up... no text, but the code is there. Step by Step Tutorial : Installing Multi-Touch Simulator for Silverlight Phone 7 Michael Sync actually has a multi-touch simulator working for WP7 ... it involves a bunch of moving parts and one of the requirements is Windows 7, but if that works for you, this will too :) Element Property Binding Improvements in Blend 4 Beta and Visual Studio 2010 RC Rénald Nollet demonstrates new Blend and VS2010 features that assists you in Element Property binding with real examples. Projection Transforms Sans Math Charles Petzold is writing about Silverlight and 3D and specifically in this post 3D without math which becomes PlaneProjection... good long tutorial on it and code to back it all up. Daily Demo: Silverlight Install out of browser & Check for Update Behaviors The-Oliver has a post up about OOB and checking for updates using behaviors with only a slight change to your xaml... cool! Wizards. Prototype of sketching Wizard for WPF – 2 Max Paulousky has part 2 of his tutorial on a sketchflow Wizard for WPF ... yes WPF, but check it out... source too. Stay in the 'Light! Twitter SilverlightNews | Twitter WynApse | WynApse.com | Tagged Posts | SilverlightCream Join me @ SilverlightCream | Phoenix Silverlight User Group Technorati Tags: Silverlight    Silverlight 3    Silverlight 4    Windows Phone MIX10

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• How I Work: A Cloud Developer's Workstation

  - by BuckWoody

  I've written here a little about how I work during the day, including things like using a stand-up desk (still doing that, by the way). Inspired by a Twitter conversation yesterday, I thought I might explain how I set up my computing environment. First, a couple of important points. I work in Cloud Computing, specifically (but not limited to) Windows Azure. Windows Azure has features to run a Virtual Machine (IaaS), run code without having to control a Virtual Machine (PaaS) and use databases, video streaming, Hadoop and more (a kind of SaaS for tech pros). As such, my designs run the gamut of on-premises, VM's in the Cloud, and software that I write for a platform. I focus on data primarily, meaning that I design a lot of systems that use an RDBMS (like SQL Server or Windows Azure Databases) or a NoSQL approach (MongoDB on Azure or large-scale Key-Value Pairs in Table storage) and even Hadoop and R, and also Cloud Numerics in F#. All that being said, those things inform my choices below. Hardware I have a Lenovo X220 tablet/laptop which I really like a great deal - it's a light, tough, extremely fast system. When I travel, that's the system I take. It has 8GB of RAM, and an SSD drive. I sometimes use that to develop or work at a client's site, on the road, or in the living room when I'm not in my home office. My main system is a GateWay DX430017 - I've maxed it out on RAM, and I have two 1TB drives in it. It's not only my workstation for work; I leave it on all the time and it streams our videos, music and books. I have about 3400 e-books, and I've just started using Calibre to stream the library. I run Windows 8 on it so I can set up Hyper-V images, since Windows Azure allows me to move regular Hyper-V disks back and forth to the Cloud. That's where all my "servers" are, when I have to use an IaaS approach. The reason I use a desktop-style system rather than a laptop only approach is that a good part of my job is setting up architectures to solve really big, complex problems. That means I have to simulate entire networks on-premises, along with the Hybrid Cloud approach I use a lot. I need a lot of disk space and memory for that, and I use two huge monitors on my stand-up desk. I could probably use 10 monitors if I had the room for them. Also, since it's our home system as well, I leave it on all the time and it doesn't travel.   Software For the software for my systems, it's important to keep in mind that I not only write code, but I design databases, teach, present, and create Linux and other environments. Windows 8 - While the jury is out for me on the new interface, the context-sensitive search, integrated everything, and speed is just hands-down the right choice. I've evaluated a server OS, Linux, even an Apple, but I just am not as efficient on those as I am with Windows 8. Visual Studio Ultimate - I develop primarily in .NET (C# and F# mostly) and I use the Team Foundation Server in the cloud, and I'm asked to do everything from UI to Services, so I need everything. Windows Azure SDK, Windows Azure Training Kit - I need the first to set up my Azure PaaS coding, and the second has all the info I need for PaaS, IaaS and SaaS. This is primarily how I get paid. :) SQL Server Developer Edition - While I might install Oracle, MySQL and Postgres on my VM's, the "outside" environment is SQL Server for an RDBMS. I install the Developer Edition because it has the same features as Enterprise Edition, and comes with all the client tools and documentation. Microsoft Office -  Even if I didn't work here, this is what I would use. I've just grown too accustomed to doing business this way to change, so my advice is always "use what works", and this does. The parts I use are: OneNote (and a Math Add-in) - I do almost everything - and I mean everything in OneNote. I can code, do high-end math, present, design, collaborate and more. All my notebooks are on my Skydrive. I can use them from any system, anywhere. If you take the time to learn this program, you'll be hooked. Excel with PowerPivot - Don't make that face. Excel is the world's database, and every Data Scientist I know - even the ones where I teach at the University of Washington - know it, use it, and love it.  Outlook - Primary communications, CRM and contact tool. I have all of my social media hooked up to it, so when I get an e-mail from you, I see everything, see all the history we've had on e-mail, find you on a map and more. Lync - I was fine with LiveMeeting, although it has it's moments. For me, the Lync client is tres-awesome. I use this throughout my day, present on it, stay in contact with colleagues and the folks on the dev team (who wish I didn't have it) and more.  PowerPoint - Once again, don't make that face. Whenever I see someone complaining about PowerPoint, I have 100% of the time found they don't know how to use it. If you suck at presenting or creating content, don't blame PowerPoint. Works great on my machine. :) Zoomit - Magnifier - On Windows 7 (and 8 as well) there's a built-in magnifier, but I install Zoomit out of habit. It enlarges the screen. If you don't use one of these tools (or their equivalent on some other OS) then you're presenting/teaching wrong, and you should stop presenting/teaching until you get them and learn how to show people what you can see on your tiny, tiny monitor. :) Cygwin - Unix for Windows. OK, that's not true, but it's mostly that. I grew up on mainframes and Unix (IBM and HP, thank you) and I can't imagine life without  sed, awk, grep, vim, and bash. I also tend to take a lot of the "Science" and "Development" and "Database" packages in it as well. PuTTY - Speaking of Unix, when I need to connect to my Linux VM's in Windows Azure, I want to do it securely. This is the tool for that. Notepad++ - Somewhere between torturing myself in vim and luxuriating in OneNote is Notepad++. Everyone has a favorite text editor; this one is mine. Too many features to name, and it's free. Browsers - I install Chrome, Firefox and of course IE. I know it's in vogue to rant on IE, but I tend to think for myself a great deal, and I've had few (none) problems with it. The others I have for the haterz that make sites that won't run in IE. Visio - I've used a lot of design packages, but none have the extreme meta-data edit capabilities of Visio. I don't use this all the time - it can be rather heavy, but what it does it does really well. I also present this way when I'm not using PowerPoint. Yup, I just bring up Visio and diagram away as I'm chatting with clients. Depending on what we're covering, this can be the right tool for that. Tweetdeck - The AIR one, not that new disaster they came out with. I live on social media, since you, dear readers, are my cube-mates. When I get tired of you all, I close Tweetdeck. When I need help or someone needs help from me, or if I want to see a picture of a cat while I'm coding, I bring it up. It's up most all day and night. Windows Media Player - I listen to Trance or Classical when I code, and I find music managers overbearing and extra. I just use what comes in the box, and it works great for me. R - F# and Cloud Numerics now allows me to load in R libraries (yay!) and I use this for statistical work on big data loads. Microsoft Math - One of the most amazing, free, rich, amazing, awesome, amazing calculators out there. I get the 64-bit version for quick math conversions, plots and formula-checks. Python - I know, right? Who knew that the scientific community loved Python so much. But they do. I use 2.7; not as much runs with 3+. I also use IronPython in Visual Studio, or I edit in Notepad++ Camstudio recorder - Windows PSR - In much of my training, and all of my teaching at the UW, I need to show a process on a screen. Camstudio records screen and voice, and it's free. If I need to make static training, I use the Windows PSR tool that's built right in. It's ostensibly for problem duplication, but I use it to record for training.   OK - your turn. Post a link to your blog entry below, and tell me how you set your system up.  

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• Movement and Collision with AABB

  - by Jeremy Giberson

  I'm having a little difficulty figuring out the following scenarios. http://i.stack.imgur.com/8lM6i.png In scenario A, the moving entity has fallen to (and slightly into the floor). The current position represents the projected position that will occur if I apply the acceleration & velocity as usual without worrying about collision. The Next position, represents the corrected projection position after collision check. The resulting end position is the falling entity now rests ON the floor--that is, in a consistent state of collision by sharing it's bottom X axis with the floor's top X axis. My current update loop looks like the following: // figure out forces & accelerations and project an objects next position // check collision occurrence from current position -> projected position // if a collision occurs, adjust projection position Which seems to be working for the scenario of my object falling to the floor. However, the situation becomes sticky when trying to figure out scenario's B & C. In scenario B, I'm attempt to move along the floor on the X axis (player is pressing right direction button) additionally, gravity is pulling the object into the floor. The problem is, when the object attempts to move the collision detection code is going to recognize that the object is already colliding with the floor to begin with, and auto correct any movement back to where it was before. In scenario C, I'm attempting to jump off the floor. Again, because the object is already in a constant collision with the floor, when the collision routine checks to make sure moving from current position to projected position doesn't result in a collision, it will fail because at the beginning of the motion, the object is already colliding. How do you allow movement along the edge of an object? How do you allow movement away from an object you are already colliding with. Extra Info My collision routine is based on AABB sweeping test from an old gamasutra article, http://www.gamasutra.com/view/feature/3383/simple_intersection_tests_for_games.php?page=3 My bounding box implementation is based on top left/bottom right instead of midpoint/extents, so my min/max functions are adjusted. Otherwise, here is my bounding box class with collision routines: public class BoundingBox { public XYZ topLeft; public XYZ bottomRight; public BoundingBox(float x, float y, float z, float w, float h, float d) { topLeft = new XYZ(); bottomRight = new XYZ(); topLeft.x = x; topLeft.y = y; topLeft.z = z; bottomRight.x = x+w; bottomRight.y = y+h; bottomRight.z = z+d; } public BoundingBox(XYZ position, XYZ dimensions, boolean centered) { topLeft = new XYZ(); bottomRight = new XYZ(); topLeft.x = position.x; topLeft.y = position.y; topLeft.z = position.z; bottomRight.x = position.x + (centered ? dimensions.x/2 : dimensions.x); bottomRight.y = position.y + (centered ? dimensions.y/2 : dimensions.y); bottomRight.z = position.z + (centered ? dimensions.z/2 : dimensions.z); } /** * Check if a point lies inside a bounding box * @param box * @param point * @return */ public static boolean isPointInside(BoundingBox box, XYZ point) { if(box.topLeft.x <= point.x && point.x <= box.bottomRight.x && box.topLeft.y <= point.y && point.y <= box.bottomRight.y && box.topLeft.z <= point.z && point.z <= box.bottomRight.z) return true; return false; } /** * Check for overlap between two bounding boxes using separating axis theorem * if two boxes are separated on any axis, they cannot be overlapping * @param a * @param b * @return */ public static boolean isOverlapping(BoundingBox a, BoundingBox b) { XYZ dxyz = new XYZ(b.topLeft.x - a.topLeft.x, b.topLeft.y - a.topLeft.y, b.topLeft.z - a.topLeft.z); // if b - a is positive, a is first on the axis and we should use its extent // if b -a is negative, b is first on the axis and we should use its extent // check for x axis separation if ((dxyz.x >= 0 && a.bottomRight.x-a.topLeft.x < dxyz.x) // negative scale, reverse extent sum, flip equality ||(dxyz.x < 0 && b.topLeft.x-b.bottomRight.x > dxyz.x)) return false; // check for y axis separation if ((dxyz.y >= 0 && a.bottomRight.y-a.topLeft.y < dxyz.y) // negative scale, reverse extent sum, flip equality ||(dxyz.y < 0 && b.topLeft.y-b.bottomRight.y > dxyz.y)) return false; // check for z axis separation if ((dxyz.z >= 0 && a.bottomRight.z-a.topLeft.z < dxyz.z) // negative scale, reverse extent sum, flip equality ||(dxyz.z < 0 && b.topLeft.z-b.bottomRight.z > dxyz.z)) return false; // not separated on any axis, overlapping return true; } public static boolean isContactEdge(int xyzAxis, BoundingBox a, BoundingBox b) { switch(xyzAxis) { case XYZ.XCOORD: if(a.topLeft.x == b.bottomRight.x || a.bottomRight.x == b.topLeft.x) return true; return false; case XYZ.YCOORD: if(a.topLeft.y == b.bottomRight.y || a.bottomRight.y == b.topLeft.y) return true; return false; case XYZ.ZCOORD: if(a.topLeft.z == b.bottomRight.z || a.bottomRight.z == b.topLeft.z) return true; return false; } return false; } /** * Sweep test min extent value * @param box * @param xyzCoord * @return */ public static float min(BoundingBox box, int xyzCoord) { switch(xyzCoord) { case XYZ.XCOORD: return box.topLeft.x; case XYZ.YCOORD: return box.topLeft.y; case XYZ.ZCOORD: return box.topLeft.z; default: return 0f; } } /** * Sweep test max extent value * @param box * @param xyzCoord * @return */ public static float max(BoundingBox box, int xyzCoord) { switch(xyzCoord) { case XYZ.XCOORD: return box.bottomRight.x; case XYZ.YCOORD: return box.bottomRight.y; case XYZ.ZCOORD: return box.bottomRight.z; default: return 0f; } } /** * Test if bounding box A will overlap bounding box B at any point * when box A moves from position 0 to position 1 and box B moves from position 0 to position 1 * Note, sweep test assumes bounding boxes A and B's dimensions do not change * * @param a0 box a starting position * @param a1 box a ending position * @param b0 box b starting position * @param b1 box b ending position * @param aCollisionOut xyz of box a's position when/if a collision occurs * @param bCollisionOut xyz of box b's position when/if a collision occurs * @return */ public static boolean sweepTest(BoundingBox a0, BoundingBox a1, BoundingBox b0, BoundingBox b1, XYZ aCollisionOut, XYZ bCollisionOut) { // solve in reference to A XYZ va = new XYZ(a1.topLeft.x-a0.topLeft.x, a1.topLeft.y-a0.topLeft.y, a1.topLeft.z-a0.topLeft.z); XYZ vb = new XYZ(b1.topLeft.x-b0.topLeft.x, b1.topLeft.y-b0.topLeft.y, b1.topLeft.z-b0.topLeft.z); XYZ v = new XYZ(vb.x-va.x, vb.y-va.y, vb.z-va.z); // check for initial overlap if(BoundingBox.isOverlapping(a0, b0)) { // java pass by ref/value gotcha, have to modify value can't reassign it aCollisionOut.x = a0.topLeft.x; aCollisionOut.y = a0.topLeft.y; aCollisionOut.z = a0.topLeft.z; bCollisionOut.x = b0.topLeft.x; bCollisionOut.y = b0.topLeft.y; bCollisionOut.z = b0.topLeft.z; return true; } // overlap min/maxs XYZ u0 = new XYZ(); XYZ u1 = new XYZ(1,1,1); float t0, t1; // iterate axis and find overlaps times (x=0, y=1, z=2) for(int i = 0; i < 3; i++) { float aMax = max(a0, i); float aMin = min(a0, i); float bMax = max(b0, i); float bMin = min(b0, i); float vi = XYZ.getCoord(v, i); if(aMax < bMax && vi < 0) XYZ.setCoord(u0, i, (aMax-bMin)/vi); else if(bMax < aMin && vi > 0) XYZ.setCoord(u0, i, (aMin-bMax)/vi); if(bMax > aMin && vi < 0) XYZ.setCoord(u1, i, (aMin-bMax)/vi); else if(aMax > bMin && vi > 0) XYZ.setCoord(u1, i, (aMax-bMin)/vi); } // get times of collision t0 = Math.max(u0.x, Math.max(u0.y, u0.z)); t1 = Math.min(u1.x, Math.min(u1.y, u1.z)); // collision only occurs if t0 < t1 if(t0 <= t1 && t0 != 0) // not t0 because we already tested it! { // t0 is the normalized time of the collision // then the position of the bounding boxes would // be their original position + velocity*time aCollisionOut.x = a0.topLeft.x + va.x*t0; aCollisionOut.y = a0.topLeft.y + va.y*t0; aCollisionOut.z = a0.topLeft.z + va.z*t0; bCollisionOut.x = b0.topLeft.x + vb.x*t0; bCollisionOut.y = b0.topLeft.y + vb.y*t0; bCollisionOut.z = b0.topLeft.z + vb.z*t0; return true; } else return false; } }

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• How do you deal with translating theory into practice?

  - by Mr. Shickadance

  Hello all! Being a computer scientist in a research field I am often tasked with working alongside professionals outside of the software domain (think math people, electrical engineer etc), and then translating their theories and ideas into real-world implementations. I often find it difficult when they present a theoretical problem which appears to be somewhat disconnected from reality. I am not saying that the theory is bogus, only that it is difficult to translate into real-world situations. For example, recently I have been working with software defined radios. We are exploring many different areas, but often the math specialists in my group would present a problem which is heavily grounded in theory (signal processing, physics, whatever). I often struggle at times where it is hard to draw direct parallels between the theory and the real-world implementation that I need to develop. Say we are working on an energy detector, the theory person in my group would say "you need to measure the noise variance with no signal present." This leads me to think "how the hell do I isolate noise from a signal in reality?" There are many examples, but I hope you see where I am going. So, my question is how does one deal with implementation of theoretical concepts when the theory seems detached from reality? Or at least when the connections are not so clear. Or perhaps, the person with the 'theory' may be ignorant of real restrictions? Note: I found this to be a hard question to ask - hopefully you are following me. If you have suggestions on how I could improve it, by all means let me know! Thanks for looking! EDIT: To be a bit more clear, I understand in situations like this that I must learn that specific domain myself to an extent (i.e. signal processing), but I am more concerned with when those theoretical concepts do not appear to be as grounded in practice as one would like.

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• Converting 2D coordinates from multiple viewpoints into 3D coordinates

  - by Kirk Smith

  Here's the situation. I've got a set of 2D coordinates that specify a point on an image. These 2D coordinates relate to an event that happened in a 3D space (video game). I have 5 images with the same event point on it, so I have 5 sets of 2D coordinates for a single 3D coordinate. I've tried everything I can think to translate these 2D coordinates into 3D coordinates, but the math just escapes me. I have a good estimate of the coordinates from which each image was taken, they're not perfect but they're close. I tried simplifying this and opening up Cinema 4D, a 3D modeling application. I placed 5 cameras at the coordinates where the pictures were taken and lined up the pictures with the event points for each one and tried to find a link, but nothing was forthcoming. I know it's a math question, but like I said, I just can't get it. I took physics in high school 6 years ago, but we didn't deal with a whole lot of this sort of thing. Any help will be very much appreciated, I've been thinking on it for quite a while and I just can't come up with anything.

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• Extreme Optimization – Curves (Function Mapping) Part 1

  - by JoshReuben

  Overview ·        a curve is a functional map relationship between two factors (i.e. a function - However, the word function is a reserved word). ·        You can use the EO API to create common types of functions, find zeroes and calculate derivatives - currently supports constants, lines, quadratic curves, polynomials and Chebyshev approximations. ·        A function basis is a set of functions that can be combined to form a particular class of functions.   The Curve class ·        the abstract base class from which all other curve classes are derived – it provides the following methods: ·        ValueAt(Double) - evaluates the curve at a specific point. ·        SlopeAt(Double) - evaluates the derivative ·        Integral(Double, Double) - evaluates the definite integral over a specified interval. ·        TangentAt(Double) - returns a Line curve that is the tangent to the curve at a specific point. ·        FindRoots() - attempts to find all the roots or zeroes of the curve. ·        A particular type of curve is defined by a Parameters property, of type ParameterCollection   The GeneralCurve class ·        defines a curve whose value and, optionally, derivative and integrals, are calculated using arbitrary methods. A general curve has no parameters. ·        Constructor params:  RealFunction delegates – 1 for the function, and optionally another 2 for the derivative and integral ·        If no derivative  or integral function is supplied, they are calculated via the NumericalDifferentiation  and AdaptiveIntegrator classes in the Extreme.Mathematics.Calculus namespace. // the function is 1/(1+x^2) private double f(double x) {     return 1 / (1 + x*x); }   // Its derivative is -2x/(1+x^2)^2 private double df(double x) {     double y = 1 + x*x;     return -2*x* / (y*y); }   // The integral of f is Arctan(x), which is available from the Math class. var c1 = new GeneralCurve (new RealFunction(f), new RealFunction(df), new RealFunction(System.Math.Atan)); // Find the tangent to this curve at x=1 (the Line class is derived from Curve) Line l1 = c1.TangentAt(1);

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• what does AngleVectors method in quake 3 source code does

  - by kypronite

  I just downloaded quake 3 for learning purposes. I know some of some linear algebra(basic vector math ie: dot,cross product). However I can't decipher what below method does, I know what is yaw,pitch and roll. But I can't connect these with vector. Worse, I'm not sure this fall under what math 'category', so I don't really know how to google. Hence the question here. Anyone? void AngleVectors( const vec3_t angles, vec3_t forward, vec3_t right, vec3_t up) { float angle; static float sr, sp, sy, cr, cp, cy; // static to help MS compiler fp bugs angle = angles[YAW] * (M_PI*2 / 360); sy = sin(angle); cy = cos(angle); angle = angles[PITCH] * (M_PI*2 / 360); sp = sin(angle); cp = cos(angle); angle = angles[ROLL] * (M_PI*2 / 360); sr = sin(angle); cr = cos(angle); if (forward) { forward[0] = cp*cy; forward[1] = cp*sy; forward[2] = -sp; } if (right) { right[0] = (-1*sr*sp*cy+-1*cr*-sy); right[1] = (-1*sr*sp*sy+-1*cr*cy); right[2] = -1*sr*cp; } if (up) { up[0] = (cr*sp*cy+-sr*-sy); up[1] = (cr*sp*sy+-sr*cy); up[2] = cr*cp; } } ddddd

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• How do I animate a spritesheet in cocos2d Android

  - by user729053

  I'm trying to animate a sprite in a spritesheet, the goal is to make the character walk from left to right. I subclassed CCSprite: CharacterSprite. this is my code: CCSpriteFrameCache.sharedSpriteFrameCache().addSpriteFrames("WalkAnimation.plist"); CCSpriteSheet spriteSheet = CCSpriteSheet.spriteSheet("WalkAnimation.png"); w.addChild(spriteSheet); ArrayList<CCSpriteFrame> walkSprites = new ArrayList<CCSpriteFrame>(); for(int i = 1; i<=8;++i) { walkSprites.add(CCSpriteFrameCache.sharedSpriteFrameCache().spriteFrameByName("walk"+ i +".png")); } //float randomFactor = (float)Math.random()*10; CCAnimation walkAnimation = CCAnimation.animation("walk", 0.1f, walkSprites); Log.v("addEnemy", "Show"); this.character = CCSprite.sprite(walkSprites.get(0)); Log.v("addEnemy", "Don't Show"); this.walkAction = CCRepeatForever.action(CCAnimate.action(walkAnimation, false)); character.runAction(walkAction); for(int k =0; k<amount; k++) { float randomFactor = (float)Math.random()*10; character.setPosition(CGPoint.ccp(-randomFactor * character.getContentSize().width/2, winSize.height / 6.0f)); spriteSheet.addChild(character); } This code is in my 2nd scene. And whenever I press on Start Game, nothing happens. But the code is executed till: character = CharacterSprite.sprite("walk1.png"); Can someone provide me of a snippet of animation using a spritesheet?

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• Drawing a circle in opengl es android, squiggly boundaries

  - by ladiesMan217

  I am new to OpenGL ES and facing a hard time drawing a circle on my GLSurfaceView. Here's what I have so far. the Circle Class public class MyGLBall { private int points=40; private float vertices[]={0.0f,0.0f,0.0f}; private FloatBuffer vertBuff; //centre of circle public MyGLBall(){ vertices=new float[(points+1)*3]; for(int i=3;i<(points+1)*3;i+=3){ double rad=(i*360/points*3)*(3.14/180); vertices[i]=(float)Math.cos(rad); vertices[i+1]=(float) Math.sin(rad); vertices[i+2]=0; } ByteBuffer bBuff=ByteBuffer.allocateDirect(vertices.length*4); bBuff.order(ByteOrder.nativeOrder()); vertBuff=bBuff.asFloatBuffer(); vertBuff.put(vertices); vertBuff.position(0); } public void draw(GL10 gl){ gl.glPushMatrix(); gl.glTranslatef(0, 0, 0); // gl.glScalef(size, size, 1.0f); gl.glColor4f(1.0f,1.0f,1.0f, 1.0f); gl.glVertexPointer(3, GL10.GL_FLOAT, 0, vertBuff); gl.glEnableClientState(GL10.GL_VERTEX_ARRAY); gl.glDrawArrays(GL10.GL_TRIANGLE_FAN, 0, points/2); gl.glDisableClientState(GL10.GL_VERTEX_ARRAY); gl.glPopMatrix(); } } I couldn't retrieve the screenshot of my image but here's what it looks like As you can see the border has crests and troughs thereby renering it squiggly which I do not want. All I want is a simple curve

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• How can I prevent Libre Office to start unexpected when I start other applications?

  - by brubaker

  I am on Ubuntu 11.10/64bit with Gnome 3. Regards [update] I trying to say that when I start an application like Nautilus LibreOffice starts as well. Sometimes this also happens when I open a document with a totally different extension i.e. a .html doc. I checked if and which plugins are installed to Firefox: OpenOffice.org Plug-in File: libnpsoplugin.so Version: OpenOffice.org Plug-in handles all its documents MIME Type Description Suffixes application/vnd.stardivision.calc StarCalc 3.0 - 5.0 sdc application/vnd.stardivision.chart StarChart 3.0 - 5.0 sds application/vnd.stardivision.draw StarDraw 3.0 - 5.0 sda application/vnd.stardivision.impress StarImpress 3.0 - 5.0 sdd application/vnd.stardivision.impress-packed StarImpress-packed 3.0 - 5.0 sdp application/vnd.stardivision.math StarMath 3.0 - 5.0 smf application/vnd.stardivision.writer StarWriter Template 3.0 - 5.0 vor application/vnd.stardivision.writer-global StarWriter Global 3.0 - 5.0 sgl application/vnd.staroffice.writer StarWriter 3.0 - 5.0 sdw application/vnd.sun.xml.calc StarOffice 6.0/7 Spreadsheet sxc application/vnd.sun.xml.calc.template StarOffice 6.0/7 Spreadsheet Template stc application/vnd.sun.xml.draw StarOffice 6.0/7 Drawing sxd application/vnd.sun.xml.draw.template StarOffice 6.0/7 Drawing Template std application/vnd.sun.xml.impress StarOffice 6.0/7 Presentation sxi application/vnd.sun.xml.impress.template StarOffice 6.0/7 Presentation Template sti application/vnd.sun.xml.math StarOffice 6.0/7 Formula sxm application/vnd.sun.xml.writer StarOffice 6.0/7 Text Document sxw application/vnd.sun.xml.writer.global StarOffice 6.0/7 Master Document sxg application/vnd.sun.xml.writer.template StarOffice 6.0/7 Text Document Template stw application/vnd.oasis.opendocument.text OpenDocument Text odt application/vnd.oasis.opendocument.text-template OpenDocument Text Template ott application/vnd.oasis.opendocument.text-master OpenDocument Master Document odm application/vnd.oasis.opendocument.text-web HTML Document Template oth application/vnd.oasis.opendocument.spreadsheet OpenDocument Spreadsheet ods application/vnd.oasis.opendocument.spreadsheet-template OpenDocument Spreadsheet Template ots application/vnd.oasis.opendocument.graphics OpenDocument Drawing odg application/vnd.oasis.opendocument.graphics-template OpenDocument Drawing Template otg application/vnd.oasis.opendocument.presentation OpenDocument Presentation odp application/vnd.oasis.opendocument.presentation-template OpenDocument Presentation Template otp application/vnd.oasis.opendocument.formula OpenDocument Formula odf

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• Slick2D + LWJGL collision system

  - by Connor W

  So I've been learning java for a while and have explored slick and lwjgl before but went away from using Slick for a while. But I've recently gone back to using it (as I'm making a platformer and Tiled will be really helpful). But here's where my problems begin: collision. I have a player polygon and I check to see if it's colliding with my tiled map with this method: public static boolean playerCollisionWith() { for(int i = 0; i < Blockmap.entities.size(); i++) { Block entity1 = (Block) Blockmap.entities.get(i); if(playerPoly.intersects(entity1.poly)) { return true; } } return false; } This would work normally but I'm using a different method for movement. Instead of just adding a speed variable to the player's x axis. I move like this: if(Keyboard.isKeyDown(Keyboard.KEY_RIGHT)) { speedX = Math.min(5, speedX + 1); moving = true; playerPoly.setX(x); if(playerCollisionWith()) { speedX = -5; playerPoly.setX(x); } } That Math.min call is what is messing me up =. I can't just call speedX = -5, because when I do the player "bounces" when the right mouse button is down and it's colliding. Bounces as in flashes back and forth REALLY quickly. But I don't really know how I would make it so that collisions on the y axis would work either, whether the player is jumping or not. So if I could get some help with how to fix this problem that would be great. Thank you for the help!

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• LWJGL Determining whether or not a polygon is on-screen.

  - by Brandon oubiub

  Not sure whether this is an LWJGL or math question. I want to check whether a shape is on-screen, so that I don't have to render it if it isn't. First of all, is there any simple way to do this that I am overlooking? Like some method or something that I haven't found? I'm going to assume there isn't. I tried using my trigonometry skills, but it is hard to do this because of how glRotate also distorts the image a little for perspective and realism. Or, is there any way to easily determine if a ray starting from the camera, and going outward in a straight line intersects a shape? (I can probably do it with my math skillz, but is there an easier way?) By the way, I can easily determine the angle at which the camera is facing around the x and y axis. EDIT: Or, possibly, I could get the angles of a vector from the camera to the object, and compare those angles to my camera angles. But I have a feeling that the distorts from glRotate and glTranslate would be an issue. I'll try it though.

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• Which of these design patterns is superior?

  - by durron597

  I find I tend to design class structures where several subclasses have nearly identical functionality, but one piece of it is different. So I write nearly all the code in the abstract class, and then create several subclasses to do the one different thing. Does this pattern have a name? Is this the best way for this sort of scenario? Option 1: public interface TaxCalc { String calcTaxes(); } public abstract class AbstractTaxCalc implements TaxCalc { // most constructors and fields are here public double calcTaxes(UserFinancials data) { // code double diffNumber = getNumber(data); // more code } abstract protected double getNumber(UserFinancials data); protected double initialTaxes(double grossIncome) { // code return initialNumber; } } public class SimpleTaxCalc extends AbstractCalc { protected double getNumber(UserFinancials data) { double temp = intialCalc(data.getGrossIncome()); // do other stuff return temp; } } public class FancyTaxCalc extends AbstractTaxCalc { protected double getNumber(UserFinancials data) { int temp = initialCalc(data.getGrossIncome()); // Do fancier math return temp; } } Option 2: This version is more like the Strategy pattern, and should be able to do essentially the same sorts of tasks. public class TaxCalcImpl implements TaxCalc { private final TaxMath worker; public DummyImpl(TaxMath worker) { this.worker = worker; } public double calcTaxes(UserFinancials data) { // code double analyzedDouble = initialNumber; int diffNumber = worker.getNumber(data, initialNumber); // more code } protected int initialTaxes(double grossIncome) { // code return initialNumber; } } public interface TaxMath { double getNumber(UserFinancials data, double initial); } Then I could do: TaxCalc dum = new TaxCalcImpl(new TaxMath() { @Override public double getNumber(UserFinancials data, double initial) { double temp = data.getGrossIncome(); // do math return temp; }); And I could make specific implementations of TaxMath for things I use a lot, or I could make a stateless singleton for certain kinds of workers I use a lot. So the question I'm asking is: Which of these patterns is superior, when, and why? Or, alternately, is there an even better third option?

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• Obtaining a world point from a screen point with an orthographic projection

  - by vargonian

  I assumed this was a straightforward problem but it has been plaguing me for days. I am creating a 2D game with an orthographic camera. I am using a 3D camera rather than just hacking it because I want to support rotating, panning, and zooming. Unfortunately the math overwhelms me when I'm trying to figure out how to determine if a clicked point intersects a bounds (let's say rectangular) in the game. I was under the impression that I could simply transform the screen point (the clicked point) by the inverse of the camera's View * Projection matrix to obtain the world coordinates of the clicked point. Unfortunately this is not the case at all; I get some point that seems to be in some completely different coordinate system. So then as a sanity check I tried taking an arbitrary world point and transforming it by the camera's View*Projection matrices. Surely this should get me the corresponding screen point, but even that didn't work, and it is quickly shattering any illusion I had that I understood 3D coordinate systems and the math involved. So, if I could form this into a question: How would I use my camera's state information (view and projection matrices, for instance) to transform a world point to a screen point, and vice versa? I hope the problem will be simpler since I'm using an orthographic camera and can make several assumptions from that. I very much appreciate any help. If it makes a difference, I'm using XNA Game Studio.

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• (Quaternion based) Trouble moving foward based on model rotation

  - by ChocoMan

  Using quaternions, I'm having trouble moving my model in its facing direction. Currently the model moves can move in all cardinal directions with no problems. The problem comes when I rotate the move as it still travelling in the direction of world space. Meaning, if I'm moving forward, backward or any other direction while rotating the model, the model acts like its a figure skater spinning while traveling in the same direction. How do I update the direction of travel proper with the facing direction of the model? Rotates model on Y-axis: Yaw = pController.ThumbSticks.Right.X * MathHelper.ToRadians(speedAngleMAX); AddRotation = Quaternion.CreateFromYawPitchRoll(yaw, 0, 0); ModelLoad.MRotation *= AddRotation; MOrientation = Matrix.CreateFromQuaternion(ModelLoad.MRotation); Moves model forward: // Move Forward if (pController.IsButtonDown(Buttons.LeftThumbstickUp)) { SpeedX = (float)(Math.Sin(ModelLoad.ModelRotation)) * FWDSpeedMax * pController.ThumbSticks.Left.Y * (float)gameTime.ElapsedGameTime.TotalSeconds; SpeedZ = (float)(Math.Cos(ModelLoad.ModelRotation)) * FWDSpeedMax * pController.ThumbSticks.Left.Y * (float)gameTime.ElapsedGameTime.TotalSeconds; // Update model position ModelLoad._modelPos += Vector3.Forward * SpeedZ; ModelLoad._modelPos += Vector3.Left * SpeedX; }

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• program logic of printing the prime numbers

  - by Vignesh Vicky

  can any body help to understand this java program it just print prime n.o ,as you enter how many you want and it works good class PrimeNumbers { public static void main(String args[]) { int n, status = 1, num = 3; Scanner in = new Scanner(System.in); System.out.println("Enter the number of prime numbers you want"); n = in.nextInt(); if (n >= 1) { System.out.println("First "+n+" prime numbers are :-"); System.out.println(2); } for ( int count = 2 ; count <=n ; ) { for ( int j = 2 ; j <= Math.sqrt(num) ; j++ ) { if ( num%j == 0 ) { status = 0; break; } } if ( status != 0 ) { System.out.println(num); count++; } status = 1; num++; } } } i dont understand this for loop condition for ( int j = 2 ; j <= Math.sqrt(num) ; j++ ) why we are taking sqrt of num...which is 3....why we assumed it as 3?

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• Making a perfect map (not tile-based)

  - by Sri Harsha Chilakapati

  I would like to make a map system as in the GameMaker and the latest code is here. I've searched a lot in google and all of them resulted in tutorials about tile-maps. As tile maps do not fit for every type of game and GameMaker uses tiles for a different purpose, I want to make a "Sprite Based" map. The major problem I had experienced was collision detection being slow for large maps. So I wrote a QuadTree class here and the collision detection is fine upto 50000 objects in the map without PixelPerfect collision detection and 30000 objects with PixelPerferct collisions enabled. Now I need to implement the method "isObjectCollisionFree(float x, float y, boolean solid, GObject obj)". The existing implementation is becoming slow in Platformer games and I need suggestions on improvement. The current Implementation: /** * Checks if a specific position is collision free in the map. * * @param x The x-position of the object * @param y The y-position of the object * @param solid Whether to check only for solid object * @param object The object ( used for width and height ) * @return True if no-collision and false if it collides. */ public static boolean isObjectCollisionFree(float x, float y, boolean solid, GObject object){ boolean bool = true; Rectangle bounds = new Rectangle(Math.round(x), Math.round(y), object.getWidth(), object.getHeight()); ArrayList<GObject> collidables = quad.retrieve(bounds); for (int i=0; i<collidables.size(); i++){ GObject obj = collidables.get(i); if (obj.isSolid()==solid && obj != object){ if (obj.isAlive()){ if (bounds.intersects(obj.getBounds())){ bool = false; if (Global.USE_PIXELPERFECT_COLLISION){ bool = !GUtil.isPixelPerfectCollision(x, y, object.getAnimation().getBufferedImage(), obj.getX(), obj.getY(), obj.getAnimation().getBufferedImage()); } break; } } } } return bool; } Thanks.

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• Sprites rendering blurry with velocity

  - by ashes999

  After adding velocity to my game, I feel like my textures are twitching. I thought it was just my eyes, until I finally captured it in a screenshot: The one on the left is what renders in my game; the one on the right is the original sprite, pasted over. (This is a screenshot from Photoshop, zoomed in 6x.) Notice the edges are aliasing -- it looks almost like sub-pixel rendering. In fact, if I had not forced my sprites (which have position and velocity as ints) to draw using integer values, I would swear that MonoGame is drawing with floating point values. But it isn't. What could be the cause of these things appearing blurry? It doesn't happen without velocity applied. To be precise, my SpriteComponent class has a Vector2 Position field. When I call Draw, I essentially use new Vector2((int)Math.Round(this.Position.X), (int)Math.Round(this.Position.Y)) for the position. I had a bug before where even stationary objects would jitter -- that was due to me using the straight Position vector and not rounding the values to ints. If I use Floor/Ceiling instead of round, the sprite sinks/hovers (one pixel difference either way) but still draws blurry.

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• Tried teaching myself to program before college, accidently overwhelmed myself, tips?

  - by Gunnar Keith

  I'm sixteen, I'm overly interested in programming, and I'm currently taking IT classes during my mornings in high school. Last year, I tried teaching myself to code. It was quite exciting, but all I did was watch TheNewBoston's videos on YouTube for Python. After his tutorials, I just did research, made some CMD programs, and that's it. After that, I got cocky and got my feet wet in many other languages. Java, C++, C#, Perl, Ruby... and it overwhelmed me. Which made it less fun to code. I want to go to college for a 2 year programming course. And I want to make writing code my profession. But how do you recommend I attack re-learning it all again? Start with Python? Don't even try? Also, I'm not 100% in math, but I'm good friends with a lot of programmers, who say they suck at math, but manage to code just fine. I'm not looking for negative feedback. I just want the proper head-start on things before college.

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