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  • NumPy: how to quickly normalize many vectors?

    - by EOL
    How can a list of vectors be elegantly normalized, in NumPy? Here is an example that does not work: from numpy import * vectors = array([arange(10), arange(10)]) # All x's, then all y's norms = apply_along_axis(linalg.norm, 0, vectors) # Now, what I was expecting would work: print vectors.T / norms # vectors.T has 10 elements, as does norms, but this does not work The last operation yields "shape mismatch: objects cannot be broadcast to a single shape". How can the normalization of the 2D vectors in vectors be elegantly done, with NumPy? Edit: Why does the above not work while adding a dimension to norms does work (as per my answer below)?

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  • How much more complex is it to draw simple curves, lines and circles in OpenGL ES rather than in Qua

    - by mystify
    Is OpenGL ES really so much faster? Why? And is it really so horrible complicated to draw such simple things in OpenGL ES compared to drawing these in Quartz 2D? For example, I have a UIView subclass with -drawRect: implemented, where I draw some lines, curves and circles. Just simple paths, with some shadow. What would I do in OpenGL ES? Isn't there this nice EAGLView layer thing? One thing that comes to mind is how do touch events go into OpenGL ES? Maybe that's the complex thing about it? Are there tutorials on basic drawing operations in OpenGL ES?

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  • How do I determine which C/C++ compiler to use?

    - by Adam Siddhi
    Greetings, I am trying to figure out which C/C++ compiler to use. I found this list of C/C++ compilers at Wikipedia: http://en.wikipedia.org/wiki/List_of_compilers#C.2FC.2B.2B_compilers I am fairly certain that I want to go with an open source compiler. I feel that if it is open source then it will be a more complete compiler since many programmer perspectives are used to make it better. Please tell me if you disagree. I should mention that I plan on learning C/C++ mainly to program 2D/3D game applications that will be compatible with Windows, Linux, MAC and iPhone operating systems. I am currently using Windows Vista x64 OS. Thanks, Adam

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  • What are some techniques to create scrollable areas?

    - by Omega
    I'm getting started with OpenGL ES on Android and I'd looking to learn some techniques to have a game map larger than the visible area. I'm assuming I've somehow got to ensure that the system isn't rendering the entire scene, including what's outside of the visible area. I'm just not sure how I'd go about designing this! This is for simple 2D top-down tile based rendering. No real 3D except what's inherent in OpenGL ES itself. Would anyone be able to get me started on the right path? Are there options that might scale nicely when I decide to start tilting my perspective and doing 3D?

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  • Variable alpha blending in pylab

    - by Hooked
    How does one control the transparency over a 2D image in pylab? I'd like to give two sets of values (X,Y,Z,T) where X,Y are arrays of positions, Z is the color value, and T is the transparency to a function like imshow but it seems that the function only takes alpha as a scalar. As a concrete example, consider the code below that attempts to display two Gaussians. The closer the value is to zero, the more transparent I'd like the plot to be. from pylab import * side = linspace(-1,1,100) X,Y = meshgrid(side,side) extent = (-1,1,-1,1) Z1 = exp(-((X+.5)**2+Y**2)) Z2 = exp(-((X-.5)**2+(Y+.2)**2)) imshow(Z1, cmap=cm.hsv, alpha=.6, extent=extent) imshow(Z2, cmap=cm.hsv, alpha=.6, extent=extent) show() Note: I am not looking for a plot of Z1+Z2 (that would be trivial) but for a general way to specify the alpha blending across an image.

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  • How large a role does subjectiveness play in programming?

    - by Bob
    I often read about the importance of readability and maintainability. Or, I read very strong opinions about which syntax features are bad or good. Or discussions about the values of certain paradigms, like OOP. Aside from that, this same question floats about in my mind whenever I read debates on SO or Meta about subjective questions. Or read questions about best practices and sometimes find myself or others disagreeing. What role does subjectiveness play within the programming realm? Sometimes I think it plays a large role. Software developers are engineers in a way, but also people. A large part of programming is dealing with code that's human readable. This is very different from Math or Physics or other disciplines with very exact and structured rules. Here the exact structure and rules are largely up in the air, changeable on a whim, and hence the amount of languages in existence. And one person may find one language very readable, and another person may find their own language the most comforting. The same with practices. One person may not like certain accepted practices. I myself find splitting classes into different files very unreadable, for instance. But, I can't say rules haven't helped in general. Certain practices have and do make life easier. And new languages have given rise to syntax and structure that make life easier. There's certainly been a progression towards code that is easier to read and maintain even given a largely diverse group of people. So maybe these things aren't as subjective as I thought. It reminds me, in a way, of UI design. Certainly it's subjective, but then there's an entire discipline involved in crafting good UI and it tends to work. Is there something non-subjective about the ideas behind maintainability, readability, and other best practices? Is there something tangible to grasp when one develops a new language or thinks of new practices?

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  • Merge overlapping triangles into a polygon

    - by nornagon
    I've got a bunch of overlapping triangles from a 3D model projected into a 2D plane. I need to merge each island of touching triangles into a closed, non-convex polygon. The resultant polygons shouldn't have any holes in them (since the source data doesn't). Many of the source triangles share (floating point identical) edges with other triangles in the source data. What's the easiest way to do this? Performance isn't particularly important, since this will be done at design time.

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  • Java (or possibly other languages) learning path

    - by bgo
    I am familiar (as a self-learner) with C, python and php such that i can solve some problems involving simple steps (for example, i easily do calculations for physics lab reports with python which normally would take 4x-5x times longer with a calculator). The point here is, as doing such things, i learnt the idea / concepts of programming language and problem solving along with oop or fuctional programming etc. Recently i have started Java and, with the familiarity of other languages, i am doing well for starters but i need guidence. -I am thinking of learning syntax from sun java tutorials and then practicing with codingbat.com or similar sites. I need a reference book that i can study deeper aspects of the topics i am learning. What do you suggest about these? -The problem is (and always have been) the lack of practice. I need coding and problem-solving practices sources. I stuck at the point where i can't figure out what to do next. Can you suggest any source (possibly like codingbat)? If i could plan a learning trail, i can progress faster and efficiently. So i need ideas, comments, suggestions. Thanks in advance.

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  • How do I make lines scale when using GLOrtho?

    - by Mason Wheeler
    I'm using GLOrtho to set up a 2D view that I can render textures onto. It works really well, up until I try to zoom in on the image. If I pass half the width and half the height of the viewport to GLOrtho, I end up with all my textures displayed twice as big as normal, which is exactly what I expect. But then I try to draw a box around part of the image and it all falls apart. I call glBegin(GL_LINE_LOOP), place the four vertices, and call glEnd, and I expect to see the same thing I would see if I drew it at normal zoom level, doubled. Instead, I get lines that are all the right length, but they all come out one pixel wide, instead of two, and it looks really bad. What am I missing?

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  • Compiling Allegro source code (C#)

    - by 7331
    I am trying to build a C# project (downloaded code) in Visual Studio Express 2008. I get the error (my translation): The type or namespace name "Allegro" couldn't be found. for the line using Allegro; I know the 2D graphics library Allegro, of course, but I can't find much information on how to use it in C#. It is being used for visualization in the project I am trying to compile. I also get the warning This reference couldn't be resolved. The Universal assembly couldn't be found. I haven't been working with C# before and and I barely know Visual Studio Express. These are newbie mistakes - but I just need a fast solution for this problem. Could someone provide me with a short step-by-step solution?

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  • Sum an Array - Objective-C

    - by Graham
    Hi Guys, I'm just starting out and I'm looking for an easy way to sum a simple array. I've read into apple developer site on key value coding and I don't understand how to apply that to my array or if that's the appropriate way to sum this. My stumbling block with the key value coding is the .keypathToProperty - I can sort of understand that you need a further reference in a 2D array but they don't show the array code, only the keypath to the title of the row so I can't figure it out yet. NSMutableArray *numArray = [NSMutableArray arrayWithCapacity:4]; [numArray addObject:num1]; [numArray addObject:num2]; [numArray addObject:num3]; [numArray addObject:num4]; I appreciate the replies! Thanks Graham

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  • What should a Java/SOA developer be able to do?

    - by Regular Joe
    I got assigned the task to list the activities a Java Developer should be able to perform and create an estimate about the time it would take. I've came up with the following: Create JDBC CRUD backend ( S=1d, M=5d, H=10d ) Create JSP/Servlet frontend for a CRUD app ( S=1d, M=10d, H=20d ) Create Swing desktop frontend ( S=1d, M=15d, H=30d) Create ORM based CRUD etc. Create Webapp fronend with webframework etc Where.. S = Small complexity M = Medium complexity H = High complexity 1d = 1 day This is thought for a Java "enterprise" developer. The other profile I have is SOA Developer, but I could not pass beyond: Create webservice ( S=.5d, M=2d, H=7d ) Q.- What other activities should a Java Developer be able to do? Q.- What activities should a SOA Developer be able to do? Please, help me with this, I know this is in the limit of the kind of questions that could be asked here, but I really need a little push on this, and I don't want to go to Yahoo Answers for this.

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  • Simple Android OpenGL App Lag

    - by Eugene
    Hi, I have an Android OpenGL application which simply draws 2D squares (using 2 triangles) and animates them moving down the screen. I essentially do this by running: glLoadIdentity(), then glTranslatef, and finally glDrawElements all in a for loop. (The for loop is to draw all 10 blocks on the screen for every frame). In every drawFrame, the y-position of the blocks increments for the animation. The problem I'm having is strange. I run the application and the animation is laggy and not smooth. Then I re-run the application and I get a smooth animation. If I run again, I may get a smooth animation, or possibly not. Is my method correct, or is there a better way of doing this animation? Thanks for the help!

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  • calculate intersection between two segments in a symmetric way

    - by Elazar Leibovich
    When using the usual formulas to calculate intersection between two 2D segments, ie here, if you round the result to an integer, you get non-symmetric results. That is, sometimes, due to rounding errors, I get that intersection(A,B)!=intersection(B,A). The best solution is to keep working with floats, and compare the results up to a certain precision. However, I must round the results to integers after calculating the intersection, I cannot keep working with floats. My best solution so far was to use some full order on the segments in the plane, and have intersection to always compare the smaller segment to the larger segment. Is there a better method? Am I missing something?

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  • OpenGL: Textured Primitives + High Framerate

    - by James D
    Short version: What's the best practice going forward for efficiently rendering large numbers of independent texture-mapped, lighted 2D/3D primitives (circles, rects, etc.) in OpenGL? For example: a typical particle system using billboarded quads/triangles, point sprites, or whatever other technique, with blending. Because after reading this thread on the messiness of OpenGL versioning/deprecation I'm starting to have my doubts. My specific question is not the ABCs of displaying primitives in OpenGL, but rather how to do so efficiently in post-deprecation (or pre-deprecation) OpenGL, in a way that's going to be compatible with a wide range of commodity hardware and in a way that's not going to break or itself get deprecated, five years down the line. Thanks!

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  • Library for polygon operations

    - by AJM
    I've recently encountered a need for a library or set of libraries to handle operations on 2D polygons. I need to be able to perform boolean/clipping operations (difference and union) and triangulation. So far the libraries I've found are poly2tri, CGAL, and GPC. Poly2tri looks good for triangulation but I'm still left with boolean operations, and I'm unsure about its maturity. CGAL and GPC are only free if my own project is free. My particular project isn't commercial, so I'm hesitant to pay or request for any licenses. But I may want to use my code for a future commercial project, so I'm hesitant about CGAL's open source licenses and GPC's freeware-only restriction. There doesn't seem to be any polygon clipping libraries with nice BSD-style licenses.

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  • Logging a specific package in log4j programmatically

    - by VinTem
    Hi there, here is the thing, I have to deploy a web app and the the log4j.properties file is created by the client so I dont have control over it. Their properties file is like this: log4j.rootCategory= FILE !-----------FILE--------------! log4j.category.FILE=DEBUG log4j.appender.FILE=org.apache.log4j.RollingFileAppender log4j.appender.FILE.File=${catalina.base}/logs/rcweb.log log4j.appender.FILE.MaxFileSize=1024KB log4j.appender.FILE.MaxBackupIndex=10 log4j.appender.FILE.layout=org.apache.log4j.PatternLayout log4j.appender.FILE.layout.ConversionPattern=%-2d{dd/MM/yyyy HH:mm:ss} [%t] %5p %c:%L - %m%n And in my classes I do something like this: private static final Logger LOG = Logger.getLogger(MaterialController.class); LOG.info("my log"); But the log file has never been created. I did the test and changed the log4j.properties file and deployed in my computer adding the following line: log4j.logger.br.com.golive.requisicaoCompras=DEBUG This works, but I cant use the file like this. Is there any ideas? Thanks

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  • 'Array of arrays' in matlab?

    - by waitinforatrain
    Hey, having a wee bit of trouble. Trying to assign a variable length 1d array to different values of an array, e.g. a(1) = [1, 0.13,0.52,0.3]; a(2) = [1, 0, .268]; However, I get the error: ??? In an assignment A(I) = B, the number of elements in B and I must be the same. Error in ==> lab2 at 15 a(1) = [1, 0.13,0.52,0.3]; I presume this means that it's expecting a scalar value instead of an array. Does anybody know how to assign the array to this value? I'd rather not define it directly as a 2d array as it is for are doing solutions to different problems in a loop Edit: Got it! a(1,1:4) = [1, 0.13,0.52,0.3]; a(2,1:3) = [1, 0, .268];

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  • Common lisp, CFFI, and instantiating c structs

    - by andrew
    Hi, I've been on google for about, oh, 3 hours looking for a solution to this "problem." I'm trying to figure out how to instantiate a C structure in lisp using CFFI. I have a struct in c: struct cpVect{cpFloat x,y;} Simple right? I have auto-generated CFFI bindings (swig, I think) to this struct: (cffi:defcstruct #.(chipmunk-lispify "cpVect" 'classname) (#.(chipmunk-lispify "x" 'slotname) :double) (#.(chipmunk-lispify "y" 'slotname) :double)) This generates a struct "VECT" with slots :X and :Y, which foreign-slot-names confirms (please note that I neither generated the bindings or programmed the C library (chipmunk physics), but the actual functions are being called from lisp just fine). I've searched far and wide, and maybe I've seen it 100 times and glossed over it, but I cannot figure out how to create a instance of cpVect in lisp to use in other functions. Note the function: cpShape *cpPolyShapeNew(cpBody *body, int numVerts, cpVect *verts, cpVect offset) Takes not only a cpVect, but also a pointer to a set of cpVects, which brings me to my second question: how do I create a pointer to a set of structs? I've been to http://common-lisp.net/project/cffi/manual/html_node/defcstruct.html and tried the code, but get "Error: Unbound variable: PTR" (I'm in Clozure CL), not to mention that looks to only return a pointer, not an instance. I'm new to lisp, been going pretty strong so far, but this is the first real problem I've hit that I can't figure out. Thanks!

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  • Dynamic programming: Largest diamond(rhombus) block

    - by Darksody
    I have a small program to do in Java. I have a 2D array filled with 0 and 1, and I must find the largest rhombus (as in square rotated by 90 degrees) and their numbers. Example: 0 1 0 0 0 1 1 0 1 1 1 0 1 0 1 1 1 1 0 1 1 1 1 1 0 0 1 1 1 1 1 1 1 1 1 1 Result: 1 1 1 1 1 1 1 1 1 1 1 1 1 The problem is similar to this SO question. If you have any idea, post it here.

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  • Android: Deciding between SurfaceView and OpenGL (GLSurfaceView)

    - by Rich
    Is there a way to decide up front based on the expected complexity of a game/app in the planning phase whether to use regular Canvas drawing in a SurfaceView or to go with OpenGL? I've been playing around with a Canvas and only need 2D movement, and on a fairly new phone I'm getting pretty decent performance with a bunch of primitive objects and a few bitmaps running around the screen on a solid background. Is it fair to say that if I'm going to be drawing background images and increasing the number of objects being moved and drawn on top of them that I should go straight to OpenGL?

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  • Beagleboard: How do I send/receive data to/from the DSP?

    - by snakile
    I have a beagleboard with TMS320C64x+ DSP. I'm working on an image processing beagleboard application. Here's how it's going to work: The ARM reads an image from a file and put the image in a 2D array. The arm sends the matrix to the DSP. The DSP receives the matrix. The DSP performs the image processing algorithm on the received matrix (the algorithm code uses about 5MB of dynamically allocated memory). The DSP sends the processed image (matrix) to the ARM. The arm received the matrix. The arm saved the processed image to a file. I'v already written the code for steps 1,3,5. What is the easiest way to do steps 3+4 (sending the data)? Code examples are welcome.

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  • C++ - dynamic pointer of array

    - by Eagle
    Hi to all, first i would like to say i am Newbie in C++. As part of my master thesis i am writing a program in C++ which also get as parameters the variables m and d (both integers). Were d is the power of 2 (this means 2^d elements). Parameter m define the number of possible interactions between one element and the total group (2^d elements). The number of possible interactions is computed as following: \kappa = \sum_{i=0}^m\binom{d}{i} (at present i generate vector of vectors for 2^d x \kappa, but my Prof. would like me to create different statistics to different m's. My first though was to to generate a dynamic array of m arrays of different sizes... Then i though of defining a 3-dim array with the biggest needed 2d array, but also program speed is important (e.g d = 20). i would like to ask for your advice how to define such kind of dynamic array that will also be fast. Regards

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  • Dynamic programming: Find largest diamond (rhombus)

    - by Darksody
    I have a small program to do in Java. I have a 2D array filled with 0 and 1, and I must find the largest rhombus (as in square rotated by 90 degrees) and their numbers. Example: 0 1 0 0 0 1 1 0 1 1 1 0 1 0 1 1 1 1 0 1 1 1 1 1 0 0 1 1 1 1 1 1 1 1 1 1 Result: 1 1 1 1 1 1 1 1 1 1 1 1 1 The problem is similar to this SO question. If you have any idea, post it here.

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  • How to determine which side of a 3D plane is showing?

    - by Josh Santangelo
    This is a 3d n00b question. I'm working on a WPF control which implements the basics of Silverlight's PerspectiveTransform feature, allowing a 2D plane to be rotated on any of the three axes. It works pretty well. However I'm a little stuck on the math required to determine whether or not the back of the plane is showing. My naive code for figuring that out now is: bool isBackShowing = Math.Abs(RotationX) > 90 && Math.Abs(RotationY) < 90; if (!isBackShowing) { isBackShowing = Math.Abs(RotationX) < 90 && Math.Abs(RotationY) > 90; } However, this fails when the rotation is between +-270 and +-360 on either axis. The underlying transform is using a Quaternion object to do the actual rotation, and that has nice Axis and Angle properties, so I'm guessing I could just use that if I knew how.

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