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  • In 3D camera math, calculate what Z depth is pixel unity for a given FOV

    - by badweasel
    I am working in iOS and OpenGL ES 2.0. Through trial and error I've figured out a frustum to where at a specific z depth pixels drawn are 1 to 1 with my source textures. So 1 pixel in my texture is 1 pixel on the screen. For 2d games this is good. Of course it means that I also factor in things like the size of the quad and the size of the texture. For example if my sprite is a quad 32x32 pixels. The quad size is 3.2 units wide and tall. And the texcoords are 32 / the size of the texture wide and tall. Then the frustum is: matrixFrustum(-(float)backingWidth/frustumScale,(float)backingWidth/frustumScale, -(float)backingHeight/frustumScale, (float)backingHeight/frustumScale, 40, 1000, mProjection); Where frustumScale is 800 for a retina screen. Then at a distance of 800 from camera the sprite is pixel for pixel the same as photoshop. For 3d games sometimes I still want to be able to do this. But depending on the scene I sometimes need the FOV to be different things. I'm looking for a way to figure out what Z depth will achieve this same pixel unity for a given FOV. For this my mProjection is set using: matrixPerspective(cameraFOV, near, far, (float)backingWidth / (float)backingHeight, mProjection); With testing I found that at an FOV of 45.0 a Z of 38.5 is very close to pixel unity. And at an FOV of 30.0 a Z of 59.5 is about right. But how can I calculate a value that is spot on? Here's my matrixPerspecitve code: void matrixPerspective(float angle, float near, float far, float aspect, mat4 m) { //float size = near * tanf(angle / 360.0 * M_PI); float size = near * tanf(degreesToRadians(angle) / 2.0); float left = -size, right = size, bottom = -size / aspect, top = size / aspect; // Unused values in perspective formula. m[1] = m[2] = m[3] = m[4] = 0; m[6] = m[7] = m[12] = m[13] = m[15] = 0; // Perspective formula. m[0] = 2 * near / (right - left); m[5] = 2 * near / (top - bottom); m[8] = (right + left) / (right - left); m[9] = (top + bottom) / (top - bottom); m[10] = -(far + near) / (far - near); m[11] = -1; m[14] = -(2 * far * near) / (far - near); } And my mView is set using: lookAtMatrix(cameraPos, camLookAt, camUpVector, mView); * UPDATE * I'm going to leave this here in case anyone has a different solution, can explain how they do it, or why this works. This is what I figured out. In my system I use a 10th scale unit to pixels on non-retina displays and a 20th scale on retina displays. The iPhone is 640 pixels wide on retina and 320 pixels wide on non-retina (obsolete). So if I want something to be the full screen width I divide by 20 to get the OpenGL unit width. Then divide that by 2 to get the left and right unit position. Something 32 units wide centered on the screen goes from -16 to +16. Believe it or not I have an excel spreadsheet do all this math for me and output all the vertex data for my sprite sheet. It's an arbitrary thing I made up to do .1 units = 1 non-retina pixel or 2 retina pixels. I could have made it .01 units = 2 pixels and someday I might switch to that. But for now it's the other. So the width of the screen in units is 32.0, and that means the left most pixel is at -16.0 and the right most is at 16.0. After messing a bit I figured out that if I take the [0] value of an identity modelViewProjection matrix and multiply it by 16 I get the depth required to get 1:1 pixels. I don't know why. I don't know if the 16 is related to the screen size or just a lucky guess. But I did a test where I placed a sprite at that calculated depth and varied the FOV through all the valid values and the object stays steady on screen with 1:1 pixels. So now I'm just calculating the unityDepth that way. If someone gives me a better answer I'll checkmark it.

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  • Documenting mathematical logic in code

    - by Kiril Raychev
    Sometimes, although not often, I have to include math logic in my code. The concepts used are mostly very simple, but the resulting code is not - a lot of variables with unclear purpose, and some operations with not so obvious intent. I don't mean that the code is unreadable or unmaintainable, just that it's waaaay harder to understand than the actual math problem. I try to comment the parts which are hardest to understand, but there is the same problem as in just coding them - text does not have the expressive power of math. I am looking for a more efficient and easy to understand way of explaining the logic behind some of the complex code, preferably in the code itself. I have considered TeX - writing the documentation and generating it separately from the code. But then I'd have to learn TeX, and the documentation will not be in the code itself. Another thing I thought of is taking a picture of the mathematical notations, equations and diagrams written on paper/whiteboard, and including it in javadoc. Is there a simpler and clearer way? P.S. Giving descriptive names(timeOfFirstEvent instead of t1) to the variables actually makes the code more verbose and even harder too read.

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  • How do I become better in math, after being a programmer for several years.

    - by loxs
    I've had quite a weird career till now. First I graduated from a medical school. Then I went into marketing (pharmaceuticals). And then umm, after some time, I decided to go for my (till then) hobby and became a "professional" programmer. I've been quite successful at this ever since. I have quite some languages "under my belt". I earn not bad and I have been involved in the opensource community quite heavily. The thing is that I suck at math :). Well, not totally of course, as I get my work done. But I don't know how much I suck. And I don't know how to find out. Math has never really been of any priority during my middle/high school years. I only picked as little as I could afford, because I was always getting ready to go for Medicine. Of course I know the basics of algebra. Things like "normal" and square equations. Also the basics of geometry. But well, there are things that I have missed. And lately I am being fascinated by things like probability theory, infinity, chaos/order etc. But every time I try to learn something about these topics, I hit a wall of terminology, special symbols, and some special kind of thinking, that is quite like mine (a programmer), but also a lot different (and appears weird to me). So, what kinds of books would you recommend me? It's very hard to find something suitable. All that I find are either too easy (and boring) or totally impenetrable.

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  • For what purpose does java have a float primitive type?

    - by Roman
    I heard plenty times different claims about float type in java. The most popular issues typicaly regard to converting float value to double and vice versa. I read (rather long time ago and not sure that it's actual now with new JVM) that float gives much worse performance then double. And it's also not recommended to use float in scientific applications which should have certain accuracy. I also remember that when I worked with AWT and Swing I had some problems with using float or double (like using Point2D.Float or Point2D.Double). So, I see only 2 advantages of float over double: it needs only 4 bytes while double needs 8 bytes JMM garantees that assignment operation is atomic with float variables while it's not atomic with double's. Are there any other cases where float is better then double? Do you use float's in your applications? It seems to me that the only valuable reason java has float is backward compatibility.

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  • Problem with Precision floating point operation in C

    - by Microkernel
    Hi Guys, For one of my course project I started implementing "Naive Bayesian classifier" in C. My project is to implement a document classifier application (especially Spam) using huge training data. Now I have problem implementing the algorithm because of the limitations in the C's datatype. ( Algorithm I am using is given here, http://en.wikipedia.org/wiki/Bayesian_spam_filtering ) PROBLEM STATEMENT: The algorithm involves taking each word in a document and calculating probability of it being spam word. If p1, p2 p3 .... pn are probabilities of word-1, 2, 3 ... n. The probability of doc being spam or not is calculated using Here, probability value can be very easily around 0.01. So even if I use datatype "double" my calculation will go for a toss. To confirm this I wrote a sample code given below. #define PROBABILITY_OF_UNLIKELY_SPAM_WORD (0.01) #define PROBABILITY_OF_MOSTLY_SPAM_WORD (0.99) int main() { int index; long double numerator = 1.0; long double denom1 = 1.0, denom2 = 1.0; long double doc_spam_prob; /* Simulating FEW unlikely spam words */ for(index = 0; index < 162; index++) { numerator = numerator*(long double)PROBABILITY_OF_UNLIKELY_SPAM_WORD; denom2 = denom2*(long double)PROBABILITY_OF_UNLIKELY_SPAM_WORD; denom1 = denom1*(long double)(1 - PROBABILITY_OF_UNLIKELY_SPAM_WORD); } /* Simulating lot of mostly definite spam words */ for (index = 0; index < 1000; index++) { numerator = numerator*(long double)PROBABILITY_OF_MOSTLY_SPAM_WORD; denom2 = denom2*(long double)PROBABILITY_OF_MOSTLY_SPAM_WORD; denom1 = denom1*(long double)(1- PROBABILITY_OF_MOSTLY_SPAM_WORD); } doc_spam_prob= (numerator/(denom1+denom2)); return 0; } I tried Float, double and even long double datatypes but still same problem. Hence, say in a 100K words document I am analyzing, if just 162 words are having 1% spam probability and remaining 99838 are conspicuously spam words, then still my app will say it as Not Spam doc because of Precision error (as numerator easily goes to ZERO)!!!. This is the first time I am hitting such issue. So how exactly should this problem be tackled?

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  • Preoblem with Precision floating point operation in C

    - by Microkernel
    Hi Guys, For one of my course project I started implementing "Naive Bayesian classifier" in C. My project is to implement a document classifier application (especially Spam) using huge training data. Now I have problem implementing the algorithm because of the limitations in the C's datatype. ( Algorithm I am using is given here, http://en.wikipedia.org/wiki/Bayesian_spam_filtering ) PROBLEM STATEMENT: The algorithm involves taking each word in a document and calculating probability of it being spam word. If p1, p2 p3 .... pn are probabilities of word-1, 2, 3 ... n. The probability of doc being spam or not is calculated using Here, probability value can be very easily around 0.01. So even if I use datatype "double" my calculation will go for a toss. To confirm this I wrote a sample code given below. #define PROBABILITY_OF_UNLIKELY_SPAM_WORD (0.01) #define PROBABILITY_OF_MOSTLY_SPAM_WORD (0.99) int main() { int index; long double numerator = 1.0; long double denom1 = 1.0, denom2 = 1.0; long double doc_spam_prob; /* Simulating FEW unlikely spam words */ for(index = 0; index < 162; index++) { numerator = numerator*(long double)PROBABILITY_OF_UNLIKELY_SPAM_WORD; denom2 = denom2*(long double)PROBABILITY_OF_UNLIKELY_SPAM_WORD; denom1 = denom1*(long double)(1 - PROBABILITY_OF_UNLIKELY_SPAM_WORD); } /* Simulating lot of mostly definite spam words */ for (index = 0; index < 1000; index++) { numerator = numerator*(long double)PROBABILITY_OF_MOSTLY_SPAM_WORD; denom2 = denom2*(long double)PROBABILITY_OF_MOSTLY_SPAM_WORD; denom1 = denom1*(long double)(1- PROBABILITY_OF_MOSTLY_SPAM_WORD); } doc_spam_prob= (numerator/(denom1+denom2)); return 0; } I tried Float, double and even long double datatypes but still same problem. Hence, say in a 100K words document I am analyzing, if just 162 words are having 1% spam probability and remaining 99838 are conspicuously spam words, then still my app will say it as Not Spam doc because of Precision error (as numerator easily goes to ZERO)!!!. This is the first time I am hitting such issue. So how exactly should this problem be tackled?

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  • Array loading with doubles in C

    - by user2892120
    I am trying to load a 3x8 array of doubles but my code keeps outputting 0.00 for all of the values. The code should be outputting the array (same as the input) under the Read#1 Read#2 Read#3 lines, with the average under average. Here is my code: #include <stdio.h> double getAvg(double num1, double num2, double num3); int main() { int numJ,month,day,year,i,j; double arr[3][8]; scanf("%d %d %d %d",&numJ,&month,&day,&year); for (i = 0; i < 8; i++) { scanf("%f %f %f",&arr[i][0], &arr[i][1], &arr[i][2]); } printf("\nJob %d Date: %d/%d/%d",numJ,month,day,year); printf("\n\nLocation Read#1 Read#2 Read#3 Average"); for (j = 0; j < 8; j++) { printf("\n %d %.2f %.2f %.2f %.2f",j+1,arr[j][0],arr[j] [1],arr[j][2],getAvg(arr[j][0],arr[j][1],arr[j][2])); } return 0; } double getAvg(double num1, double num2, double num3) { double avg = (num1 + num2 + num3) / 3; return avg; } Input example: 157932 09 01 2013 0.00 0.00 0.00 0.36 0.27 0.23 0.18 0.16 0.26 0.27 0.00 0.34 0.24 0.00 0.31 0.16 0.33 0.36 0.29 0.36 0.00 0.21 0.36 0.00

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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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  • how do I set up a double domain?

    - by kdavis8
    I would like to set up a server similar to Google's. Their domain acts like a double domain, like you can use these URLS, "play.Google.com" or "apps.Google.com", to go to different sites.. For example, my domain would now be "my_domain.com" but i would like another one to be "domain2.my_domain.com". My question is,what is this officially called and how do i set it up? I'm not sure if you need two servers or just 1;

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  • Opera double ses téléchargements en Europe depuis l'arrivée du "Ballot Screen" sur Windows : réelle

    Opera double ses téléchargements En Europe depuis l'arrivée du "Ballot Screen" sur Windows : réelle envolée ou effet passager ? Opera Software, l'éditeur du navigateur Norvégien, était à l'origine de la procédure européenne pour imposer le ballot-screen à Microsoft. Et c'est son produit, Opera qui semble bien tirer les bénéfices de cet écran de choix du navigateur par défaut à installer lors du premier démarrage de Windows. En Europe, depuis l'arrivée du ballot-screen, Opera aurait connu une pr...

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  • Must double-tap Windows key to open Dash

    - by Bart van Heukelom
    I'm experiencing some strange behaviour of the Unity Dash and the Windows/Super keyboard key. As far as I know, normal behaviour is: Tap: Open Dash Hold: Show keyboard shortcut overlay However, the behaviour I'm experiencing is: Tap: Show keyboard shortcut overlay (after a short delay) Double Tap: Open Dash Hold: Show keyboard shortcut overlay What could cause this, and how do I fix it? I'm on a fresh 12.10 (Quantal) installation.

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  • Avoid double compression of resources

    - by user1095108
    I am using .pngs for my textures and am using a virtual file system in a .zip file for my game project. This means my textures are compressed and decompressed twice. What are the solutions to this double compression problem? One solution I've heard about is to use .tgas for textures, but it seems ages ago, since I've heard that. Another solution is to implement decompression on the GPU and, since that is fast, forget about the overhead.

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  • Single quotes vs double quotes

    - by Eric Hydrick
    I just started a job where I'm writing Python after coming from a Java background, and I'm noticing that other developers tend to quote strings using single quotes ('') instead of double quotes (""). For example: line1 = 'This is how strings typically look.' line2 = "Not like this." Is there a particular reason for this other than personal preference? Is this the proper way to be quoting strings?

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  • Double Buffering in Panda3D (C++)

    - by jsvcycling
    How would I go about using Double Buffering (to create a loading screen) in Panda3D using C++? I've searched Google and found some forums that talk about the concept of swapping buffers, but I haven't seen any that show any type of source code (specifically Panda3D/C++). I'd like to try and stay away from using pure OpenGL code and work it through Panda3D, but if I have no other choice, then I'll have to go with OpenGL coding.

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  • xfce4 - 'Run Program' dialogue box does not appear when double clicking script

    - by Ron Paulfan
    Ubuntu 12.04 Xfce4 On my previous Ubuntu distro, when I double clicked scripts I got a little dialogue window that asked me if I wanted to run the script as a program or run it in terminal. Similar to this window: Since upgrading, I have never seen that window. I have ensured that the option to 'Allow executing as a program is enabled' and the script works if I run it through terminal. I simply just don't get the prompt. Any ideas?

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  • Normal Redundancy (Double Mirroring) Option Available

    - by TammyBednar
    Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Calibri","sans-serif";} The Oracle Database Appliance 2.4 Patch was released last week and provides you an option of ASM normal redundancy (double mirroring) during the initial deployment of the Database Appliance. The default deployment of the Oracle Database Appliance is high redundancy for the +DATA and +RECO disk groups. While there is 12TB of raw shared storage available, the Database Backup Location and Disk Group Redundancy govern how much usable storage is presented after the initial deployment is completed. The Database Backup Location options are Local or External. When the Local Backup Option is selected, this means that 60% of the available shared storage will be allocated for the Fast Recovery Area that contains database backups and archive logs. The External Backup Option will allocate 20% of the available shared storage to the Fast Recovery Area. So, let’s look at an example of High Redundancy and External Backups. Disk Group Redundancy – High --> Triple Mirroring to provide ~4TB of available storage Database Backup Location – External --> 20% of available shared storage allocated to +RECO +DATA = 3.2TB of usable storage, +RECO = 0.8TB of usable storage What about Normal Redundancy with External Backups? Disk Group Redundancy – Normal --> Double Mirroring to provide ~6TB of available storage Database Backup Location – External --> 20% of available shared storage allocated to +RECO +DATA = 4.8TB of usable storage, +RECO = 1.2TB of usable storage As a best practice, we would recommend using Normal Redundancy for your test and/or development Oracle Database Appliances and High Redundancy for production.

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  • Dectect ASCII codes for asian double byte / cyrillic character sets?

    - by jfroom
    Is it possible to detect if an ascii character belongs to Asian double byte or Cyrillic character sets? Perhaps specific code ranges? I've googled, but not finding anything at first glance. There's an RSS feed I'm tapping into that has the locale set as 'en-gb'. But there are some Asian double byte characters in the feed itself - which I need to handle differently. Just not sure how to detect it since the meta locale data is incorrect. I do not have access to correct the public feed.

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  • Has anyone noticed that a WPF file dialog will pass a click through to the UI when double clicking t

    - by Ben
    I have some buttons on my WPF UI and I also need to choose files from time to time. I kept noticing strange problems where when I double-click an item in the file dialog, a button on the main UI would also get clicked. After experimenting, it seems that if you line up an item in the file dialog with a button behind it on the main UI and double click to select the file, it will single-click the button behind it as well. Has anyone else noticed this, or is it just a freak bug with the way I have my UI laid out?

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