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• Diagonalization of bidiagonal matrix with QR

  - by Simon

  How can i diagonalize the matrix A having the orthogonal transformations P and Q: A = Q*B*P ? I saw something pointing out to QR transformations, but i couldn't find out the algorithm.

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• Why is the volatile qualifier used through out std::atomic?

  - by Caspin

  From what I've read from Herb Sutter and others you would think that volatile and concurrent programming were completely orthogonal concepts, at least as far as C/C++ are concerned. However, in GCC c++0x extension all of std::atomic's member functions have the volatile qualifier. The same is true in Anthony Williams's implementation of std::atomic. So what's deal, do my atomic<> variables need be volatile or not?

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• Creating a tiled world with OpenGL

  - by Tamir

  Hello, I'm planning to create a tiled world with OpenGL, with slightly rotated tiles and houses and building in the world will be made of models. Can anybody suggest me what projection(Orthogonal, Perspective) should I use, and how to setup the View matrix(using OpenGL)? If you can't figure what style of world I'm planning to create, look at this game: http://www.youtube.com/watch?v=i6eYtLjFu-Y&feature=PlayList&p=00E63EDCF757EADF&index=2

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• Help on TileMapRenderer

  - by Crypted

  In my project, I'm trying to render a map using TileMapRenderer. But it doesn't show anything when I render it. But when I use some other files from a tutorial they are rendered correctly. When debugging my TileAtlas instance shows the size as 0. I have used Texture Packer UI for packing the images. Comparing with the tutorial's files, I can see that the index starts from 1 in my file and 0 in the tutorial. But changing it to 0 wouldn't work also. map.png format: RGBA8888 filter: Nearest,Nearest repeat: none Map rotate: false xy: 0, 0 size: 32, 32 orig: 32, 32 offset: 0, 0 index: 1 Map rotate: false xy: 32, 0 size: 32, 32 orig: 32, 32 offset: 0, 0 index: 2 Map rotate: false xy: 64, 0 size: 32, 32 orig: 32, 32 offset: 0, 0 index: 3 Map rotate: false xy: 96, 0 size: 32, 32 orig: 32, 32 offset: 0, 0 index: 4 Map rotate: false xy: 128, 0 size: 32, 32 orig: 32, 32 offset: 0, 0 index: 5 Here is the begining of the tmx file. <?xml version="1.0" encoding="UTF-8"?> <map version="1.0" orientation="orthogonal" width="20" height="20" tilewidth="32" tileheight="32"> <tileset firstgid="1" name="a" tilewidth="32" tileheight="32"> <image source="map.png" width="256" height="32"/> </tileset> <layer name="Tile Layer 1" width="20" height="20"> <data> <tile gid="2"/> <tile gid="2"/> Apart from that the tutorial files and my files seems to be similar. Can anyone help me here.

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• Orthographic unit translation mismatch on grid (e.g. 64 pixels translates incorrectly)

  - by Justin Van Horne

  I am looking for some insight into a small problem with unit translations on a grid. Setup 512x448 window 64x64 grid gl_Position = projection * world * position; projection is defined by ortho(-w/2.0f, w/2.0f, -h/2.0f, h/2.0f); This is a textbook orthogonal projection function. world is defined by a fixed camera position at (0, 0) position is defined by the sprite's position. Problem In the screenshot below (1:1 scaling) the grid spacing is 64x64 and I am drawing the unit at (64, 64), however the unit draws roughly ~10px in the wrong position. I've tried uniform window dimensions to prevent any distortion on the pixel size, but now I am a bit lost in the proper way in providing a 1:1 pixel-to-world-unit projection. Anyhow, here are some quick images to aide in the problem. I decided to super-impose a bunch of the sprites at what the engine believes is 64x offsets. When this seemed off place, I went about and did the base case of 1 unit. Which seemed to line up as expected. The yellow shows a 1px difference in the movement. Vertices It would appear that the vertices going into the vertex shader are correct. For example, in reference to the first image the data looks like this in the VBO: x y x y ---------------------------- tl | 0.0 24.0 64.0 24.0 bl | 0.0 0.0 -> 64.0 0.0 tr | 16.0 0.0 80.0 0.0 br | 16.0 24.0 80.0 24.0 With that said, all I am left to believe is that I am munging up my actual projection. So, I am looking for any insight into maintaining the 1:1 pixel-to-world-unit projection.

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• Cutting out smaller rectangles from a larger rectangle

  - by Mauro Destro

  The world is initially a rectangle. The player can move on the world border and then "cut" the world via orthogonal paths (not oblique). When the player reaches the border again I have a list of path segments they just made. I'm trying to calculate and compare the two areas created by the path cut and select the smaller one to remove it from world. After the first iteration, the world is no longer a rectangle and player must move on border of this new shape. How can I do this? Is it possible to have a non rectangular path? How can I move the player character only on path? EDIT Here you see an example of what I'm trying to achieve: Initial screen layout. Character moves inside the world and than reaches the border again. Segment of the border present in the smaller area is deleted and last path becomes part of the world border. Character moves again inside the world. Segments of border present in the smaller area are deleted etc.

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• When decomposing a large function, how can I avoid the complexity from the extra subfunctions?

  - by missingno

  Say I have a large function like the following: function do_lots_of_stuff(){ { //subpart 1 ... } ... { //subpart N ... } } a common pattern is to decompose it into subfunctions function do_lots_of_stuff(){ subpart_1(...) subpart_2(...) ... subpart_N(...) } I usually find that decomposition has two main advantages: The decomposed function becomes much smaller. This can help people read it without getting lost in the details. Parameters have to be explicitly passed to the underlying subfunctions, instead of being implicitly available by just being in scope. This can help readability and modularity in some situations. However, I also find that decomposition has some disadvantages: There are no guarantees that the subfunctions "belong" to do_lots_of_stuff so there is nothing stopping someone from accidentally calling them from a wrong place. A module's complexity grows quadratically with the number of functions we add to it. (There are more possible ways for things to call each other) Therefore: Are there useful convention or coding styles that help me balance the pros and cons of function decomposition or should I just use an editor with code folding and call it a day? EDIT: This problem also applies to functional code (although in a less pressing manner). For example, in a functional setting we would have the subparts be returning values that are combined in the end and the decomposition problem of having lots of subfunctions being able to use each other is still present. We can't always assume that the problem domain will be able to be modeled on just some small simple types with just a few highly orthogonal functions. There will always be complicated algorithms or long lists of business rules that we still want to correctly be able to deal with. function do_lots_of_stuff(){ p1 = subpart_1() p2 = subpart_2() pN = subpart_N() return assembleStuff(p1, p2, ..., pN) }

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• OpenGL: Move camera regardless of rotation

  - by Markus

  For a 2D board game I'd like to move and rotate an orthogonal camera in coordinates given in a reference system (window space), but simply can't get it to work. The idea is that the user can drag the camera over a surface, rotate and scale it. Rotation and scaling should always be around the center of the current viewport. The camera is set up as: gl.glMatrixMode(GL2.GL_PROJECTION); gl.glLoadIdentity(); gl.glOrtho(-width/2, width/2, -height/2, height/2, nearPlane, farPlane); where width and height are equal to the viewport's width and height, so that 1 unit is one pixel when no zoom is applied. Since these transformations usually mean (scaling and) translating the world, then rotating it, the implementation is: gl.glMatrixMode(GL2.GL_MODELVIEW); gl.glLoadIdentity(); gl.glRotatef(rotation, 0, 0, 1); // e.g. 45° gl.glTranslatef(x, y, 0); // e.g. +10 for 10px right, -2 for 2px down gl.glScalef(zoomFactor, zoomFactor, zoomFactor); // e.g. scale by 1.5 That however has the nasty side effect that translations are transformed as well, that is applied in world coordinates. If I rotate around 90° and translate again, X and Y axis are swapped. If I reorder the transformations so they read gl.glTranslatef(x, y, 0); gl.glScalef(zoomFactor, zoomFactor, zoomFactor); gl.glRotatef(rotation, 0, 0, 1); the translation will be applied correctly (in reference space, so translation along x always visually moves the camera sideways) but rotation and scaling are now performed around origin. It shouldn't be too hard, so what is it I'm missing?

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• OPENGLES 2.0 equivalent of glorthof?

  - by Zippo

  Hi Guys, In my iphone app, i need to project 3d scene into the 2D coordinates of the screen for some calculations. My objects go through various rotations, translations and scaling. So i figured i need to multiply the vertices with ModelView matrix first, then i need to multiply it with the Orthogonal projection matrix. First of all am on the right track? I have the Model View Matrix, but need the projection matrix. Is there a glorthof equivalent in ES 2.0? PS: i am new to opengl. Thanks for your help. Zippo

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• Maths: Determining angle in 3D space

  - by 742

  I hope this is the proper location to ask this question which is the same as this one, but expressed as pure math instead of graphically (at least I hope I translated the problem to math correctly). Considering: two vectors that are orthogonal: Up (ux, uy, uz) and Look (lx, ly, lz) a plane P which is perpendicular to Look (hence including Up) Y1 which is the projection of Y (vertical axis) along Look onto P Question: what is the value of the angle between Y1 and Up? As mathematicians will agree, this is a very basic question, but I've been scratching my head on walls now for at least two weeks without being able to visualize the solution... maybe now too old for finding solutions to school exercises. I'm looking for the scalar trigonometric solution, not a solution using a matrix. Thanks.

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• Diagonal of polygon is inside or outside?

  - by Himadri

  I have three consecutive points of polygon, say p1,p2,p3. Now I wanted to know whether the orthogonal between p1 and p3 is inside the polygon or outside the polygon. I am doing it by taking three vectors v1,v2 and v3. And the point before the point p1 in polygon say p0. v1 = (p0 - p1) v2 = (p2 - p1) v3 = (p3 - p1) With reference to this question, I am using the method shown in the accepted answer of that question. It is only for counterclockwise. What if my points are clockwise. I am also knowing my whole polygon is clockwise or counterclockwise. And accordingly I select the vectors v1 and v2. But still I am getting some problem. I am showing one case where I am getting problem. This polygon is counterclockwise. and It is starting from the origin of v1 and v2.

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• What good practices, if any, has the agile movement lost?

  - by clarke ching

  I am a long time agile advocated but one of the things that bothers me about Agile is that a lot of agile practitioners, especially the younger ones, have thrown out or are missing a whole lot of good (non Scrum, non XP) practices. Alistair Cockburn's style of writing Use Cases springs to mind; orthogonal arrays (pairwise testing) is another. I hope this is an okay forum to ask this, but since I read mostly Agile related books and articles and work with mostly Agile folk ... is there anything I'm missing? Thanks for all your help. StackOverlow is a fantastic resource.

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• Design report of 4-D data set

  - by phq

  I'm writing a report generator that will present data each being generated from 4 parameters. Time interval Group Measurement value(one of several to choose from) Device All these are orthogonal giving me a 4-D dataset to present. There are some simplifications where one parameter is the same for all and other parameters are merged. Still it appears as there are situations where all values are wanted on the report. In short the report should both be simple to overview and contain details. There will also be an interface where the user setup the range and granularity for each parameter. The most naive solution would be to have a 2D table where each cell contain another table with values of the remaining two dimensions. This is technically feasible but I'm worried that it would become hard to overview. Another approach is to present first two dimensions in a 2D table and the remaining parameters in groups Are there any good method to address this kind of issue?

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• C-states and P-states : confounding factors for benchmarking

  - by Dave

  I was recently looking into a performance issue in the java.util.concurrent (JUC) fork-join pool framework related to particularly long latencies when trying to wake (unpark) threads in the pool. Eventually I tracked the issue down to the power & scaling governor and idle-state policies on x86. Briefly, P-states refer to the set of clock rates (speeds) at which a processor can run. C-states reflect the possible idle states. The deeper the C-state (higher numerical values) the less power the processor will draw, but the longer it takes the processor to respond and exit that sleep state on the next idle to non-idle transition. In some cases the latency can be worse than 100 microseconds. C0 is normal execution state, and P0 is "full speed" with higher Pn values reflecting reduced clock rates. C-states are P-states are orthogonal, although P-states only have meaning at C0. You could also think of the states as occupying a spectrum as follows : P0, P1, P2, Pn, C1, C2, ... Cn, where all the P-states are at C0. Our fork-join framework was calling unpark() to wake a thread from the pool, and that thread was being dispatched onto a processor at deep C-state, so we were observing rather impressive latencies between the time of the unpark and the time the thread actually resumed and was able to accept work. (I originally thought we were seeing situations where the wakee was preempting the waker, but that wasn't the case. I'll save that topic for a future blog entry). It's also worth pointing out that higher P-state values draw less power and there's usually some latency in ramping up the clock (P-states) in response to offered load. The issue of C-states and P-states isn't new and has been described at length elsewhere, but it may be new to Java programmers, adding a new confounding factor to benchmarking methodologies and procedures. To get stable results I'd recommend running at C0 and P0, particularly for server-side applications. As appropriate, disabling "turbo" mode may also be prudent. But it also makes sense to run with the system defaults to understand if your application exhibits any performance sensitivity to power management policies. The operating system power management sub-system typically control the P-state and C-states based on current and recent load. The scaling governor manages P-states. Operating systems often use adaptive policies that try to avoid deep C-states for some period if recent deep idle episodes proved to be very short and futile. This helps make the system more responsive under bursty or otherwise irregular load. But it also means the system is stateful and exhibits a memory effect, which can further complicate benchmarking. Forcing C0 + P0 should avoid this issue.

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• Rending 2D Tile World (With Player In The Middle)

  - by Mick

  What I have at the moment is a series of data structures I'm using, and I would like to render the world onto the screen (just the visible parts). I've actually already done this several times (lots of rewrites), but it's a bit buggy (rounding seems to make the screen jump ever so slightly every x tiles the player walks past). Basically I've been confusing myself heavily on what I feel should be a pretty simple problem... so here I am asking for some help! OK! So I have a 50x50 array holding the tiles of the world. I have the player position as 2 floats, x ([0, 49]) and y ([0, 49]) in that array. I have the application size exactly in pixels (x and y). I have an arbitrary TILE_SIZE static int (based on screen pixels). What I think is heavily confusing me is using a 2d orthogonal projection in opengl which maps (0,0) to the top left of the screen and (SCREEN_SIZE_X, SCREEN_SIZE_Y) to the bottom right of the screen. gl.glMatrixMode(GL.GL_PROJECTION); gl.glLoadIdentity(); glu.gluOrtho2D(0, getActualWidth(), getActualHeight(), 0); gl.glMatrixMode(GL.GL_MODELVIEW); gl.glLoadIdentity(); The map tiles are set so that the (0,0) in the array is the bottom left. And the player has to be in the middle on the screen (SCREEN_SIZE_X/2, SCREEN_SIZE_Y/2). What I've been doing so far is trying to render 1-2 tiles more all around what would be displayed on the screen so that I don't have to worry about figuring out rendering half a tile from the top left, depending where the player is. It seems like such an easy problem but after spending about 40+hours on it rewriting it many times I think I'm at a point where I just can't think clearly anymore... Any help would be appreciated. It would be great if someone can provide some very basic pseudo code on keeping the player in the middle when your projection is mapped to screen coordinates and only rendering basically the tiles that you would be any be see. Thanks!

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• How to get desired FireFox last tab behavior?

  - by JustJeff

  All tabs should be the same; so if any of the have a 'close' button, they all should, including the last tab. I see no reason that a tab's close button should suddenly vanish simply b/c that tab has become the last one open. If I have N tabs open, and park the mouse over the left-most tab's close button, this vanishing close button trick means now I have to make a large mouse move to get to the app's close button. Unsat. Mouse moves = too many milliseconds wasted. Closing the last tab should NOT take me to my home page, or any other page whatsoever. I want the browser to close with the last tab. I do not expect or want "new tab" behavior when I click a Close button. Now, I've gone into about:config and played with browser.tabs.closeWindoWithLastTab, but this setting oversteps its purpose; while it does make the browser close, for some inexplicable reason, it also suppresses the last tab's close button! I have tried the "last tab close button" add-on, and while this does restore the close button, the add-on oversteps by taking the liberty of turning closeWindowWithLastTab off. Is there some way out of this pickle? Is it too hard to just code things to provide simple, orthogonal actions, so that everybody can config the UI to their liking, and not just to a few pre-fab configurations that the developers think everyone should like? Btw, FF 13.0.1 on ms windows

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• View transform seems to be ignored when animating on iphone. Why?

  - by heymon

  I have views that can be rotated, scaled and moved around the screen. I want the view to resize and be orthogonal when the user double tap's the view to edit the textview within. The code is below. Somewhere the transform is getting reset. The NSLog statement below prints the identity transform, but a print of the transform when the animation is complete in transitionDidStop reveals that the transform is what it was before I thought I set it to identity. The view resizes, but it acts like the transform was never set to identity? Any ideas/pointers? originalBounds = self.bounds; originalCenter = self.center; originalTransform = self.transform; r = CGRectMake(0, 0, [UIScreen mainScreen].bounds.size.width - 70, 450); [UIView beginAnimations: nil context: NULL]; [UIView setAnimationDelegate: self]; [UIView setAnimationDidStopSelector: @selector(transitionDidStop:finished:context:)]; self.transform = CGAffineTransformIdentity; NSLog(@"%@ after set", NSStringFromCGAffineTransform([self transform])); [self setBounds: r]; [self setCenter: p]; [self setAlpha: 1.0]; [UIView commitAnimations]; [textView becomeFirstResponder];

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• OpenGL Pixel Format Attributes (NSOpenGLPixelFormatAttibutes) explanation?

  - by nacho4d

  Hi, I am not new to OpenGL, but not an expert. Many tutorials teach how to draw, 3D, 2D, projections, orthogonal, etc, but How about setting a the view? (NSOpenGLView in Cocoa, Macs). For example I have this: - (id) initWithFrame: (NSRect) frame { GLuint attribs[] = { //PF: PixelAttibutes NSOpenGLPFANoRecovery, NSOpenGLPFAWindow, NSOpenGLPFAAccelerated, NSOpenGLPFADoubleBuffer, NSOpenGLPFAColorSize, 24, NSOpenGLPFAAlphaSize, 8, NSOpenGLPFADepthSize, 24, NSOpenGLPFAStencilSize, 8, NSOpenGLPFAAccumSize, 0, 0 }; NSOpenGLPixelFormat* fmt = [[NSOpenGLPixelFormat alloc] initWithAttributes: (NSOpenGLPixelFormatAttribute*) attribs]; return self = [super initWithFrame:frame pixelFormat: [fmt autorelease]]; } And I don't understand very well their usage, specially when combining them. For example: If I want my view to be capable of full screen should I write NSOpenGLPFAFullScreen only ? or both? (by capable I mean not always in full screen) Regarding Double Buffer, what is this exactly? (Below: Apple's definition) If present, this attribute indicates that only double-buffered pixel formats are considered. Otherwise, only single-buffered pixel formats are considered Regarding Color: if NSOpenGLPFAColorSize is 24 and NSOpenGLPFAColorSize is 8 then it means that alpha and RGB components are treated differently? what happen if I set the former to 32 and the later to 0? Etc, etc,In general how do I learn to set my view from scratch? Thanks in advance. Ignacio.

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• NET Math Libraries

  - by JoshReuben

  NET Mathematical Libraries   .NET Builder for Matlab The MathWorks Inc. - http://www.mathworks.com/products/netbuilder/ MATLAB Builder NE generates MATLAB based .NET and COM components royalty-free deployment creates the components by encrypting MATLAB functions and generating either a .NET or COM wrapper around them. .NET/Link for Mathematica www.wolfram.com a product that 2-way integrates Mathematica and Microsoft's .NET platform call .NET from Mathematica - use arbitrary .NET types directly from the Mathematica language. use and control the Mathematica kernel from a .NET program. turns Mathematica into a scripting shell to leverage the computational services of Mathematica. write custom front ends for Mathematica or use Mathematica as a computational engine for another program comes with full source code. Leverages MathLink - a Wolfram Research's protocol for sending data and commands back and forth between Mathematica and other programs. .NET/Link abstracts the low-level details of the MathLink C API. Extreme Optimization http://www.extremeoptimization.com/ a collection of general-purpose mathematical and statistical classes built for the.NET framework. It combines a math library, a vector and matrix library, and a statistics library in one package. download the trial of version 4.0 to try it out. Multi-core ready - Full support for Task Parallel Library features including cancellation. Broad base of algorithms covering a wide range of numerical techniques, including: linear algebra (BLAS and LAPACK routines), numerical analysis (integration and differentiation), equation solvers. Mathematics leverages parallelism using .NET 4.0's Task Parallel Library. Basic math: Complex numbers, 'special functions' like Gamma and Bessel functions, numerical differentiation. Solving equations: Solve equations in one variable, or solve systems of linear or nonlinear equations. Curve fitting: Linear and nonlinear curve fitting, cubic splines, polynomials, orthogonal polynomials. Optimization: find the minimum or maximum of a function in one or more variables, linear programming and mixed integer programming. Numerical integration: Compute integrals over finite or infinite intervals, over 2D and higher dimensional regions. Integrate systems of ordinary differential equations (ODE's). Fast Fourier Transforms: 1D and 2D FFT's using managed or fast native code (32 and 64 bit) BigInteger, BigRational, and BigFloat: Perform operations with arbitrary precision. Vector and Matrix Library Real and complex vectors and matrices. Single and double precision for elements. Structured matrix types: including triangular, symmetrical and band matrices. Sparse matrices. Matrix factorizations: LU decomposition, QR decomposition, singular value decomposition, Cholesky decomposition, eigenvalue decomposition. Portability and performance: Calculations can be done in 100% managed code, or in hand-optimized processor-specific native code (32 and 64 bit). Statistics Data manipulation: Sort and filter data, process missing values, remove outliers, etc. Supports .NET data binding. Statistical Models: Simple, multiple, nonlinear, logistic, Poisson regression. Generalized Linear Models. One and two-way ANOVA. Hypothesis Tests: 12 14 hypothesis tests, including the z-test, t-test, F-test, runs test, and more advanced tests, such as the Anderson-Darling test for normality, one and two-sample Kolmogorov-Smirnov test, and Levene's test for homogeneity of variances. Multivariate Statistics: K-means cluster analysis, hierarchical cluster analysis, principal component analysis (PCA), multivariate probability distributions. Statistical Distributions: 25 29 continuous and discrete statistical distributions, including uniform, Poisson, normal, lognormal, Weibull and Gumbel (extreme value) distributions. Random numbers: Random variates from any distribution, 4 high-quality random number generators, low discrepancy sequences, shufflers. New in version 4.0 (November, 2010) Support for .NET Framework Version 4.0 and Visual Studio 2010 TPL Parallellized – multicore ready sparse linear program solver - can solve problems with more than 1 million variables. Mixed integer linear programming using a branch and bound algorithm. special functions: hypergeometric, Riemann zeta, elliptic integrals, Frensel functions, Dawson's integral. Full set of window functions for FFT's. Product  Price Update subscription Single Developer License $999  $399  Team License (3 developers) $1999  $799  Department License (8 developers) $3999  $1599  Site License (Unlimited developers in one physical location) $7999  $3199    NMath http://www.centerspace.net .NET math and statistics libraries matrix and vector classes random number generators Fast Fourier Transforms (FFTs) numerical integration linear programming linear regression curve and surface fitting optimization hypothesis tests analysis of variance (ANOVA) probability distributions principal component analysis cluster analysis built on the Intel Math Kernel Library (MKL), which contains highly-optimized, extensively-threaded versions of BLAS (Basic Linear Algebra Subroutines) and LAPACK (Linear Algebra PACKage). Product  Price Update subscription Single Developer License $1295 $388 Team License (5 developers) $5180 $1554   DotNumerics http://www.dotnumerics.com/NumericalLibraries/Default.aspx free DotNumerics is a website dedicated to numerical computing for .NET that includes a C# Numerical Library for .NET containing algorithms for Linear Algebra, Differential Equations and Optimization problems. The Linear Algebra library includes CSLapack, CSBlas and CSEispack, ports from Fortran to C# of LAPACK, BLAS and EISPACK, respectively. Linear Algebra (CSLapack, CSBlas and CSEispack). Systems of linear equations, eigenvalue problems, least-squares solutions of linear systems and singular value problems. Differential Equations. Initial-value problem for nonstiff and stiff ordinary differential equations ODEs (explicit Runge-Kutta, implicit Runge-Kutta, Gear's BDF and Adams-Moulton). Optimization. Unconstrained and bounded constrained optimization of multivariate functions (L-BFGS-B, Truncated Newton and Simplex methods).   Math.NET Numerics http://numerics.mathdotnet.com/ free an open source numerical library - includes special functions, linear algebra, probability models, random numbers, interpolation, integral transforms. A merger of dnAnalytics with Math.NET Iridium in addition to a purely managed implementation will also support native hardware optimization. constants & special functions complex type support real and complex, dense and sparse linear algebra (with LU, QR, eigenvalues, ... decompositions) non-uniform probability distributions, multivariate distributions, sample generation alternative uniform random number generators descriptive statistics, including order statistics various interpolation methods, including barycentric approaches and splines numerical function integration (quadrature) routines integral transforms, like fourier transform (FFT) with arbitrary lengths support, and hartley spectral-space aware sequence manipulation (signal processing) combinatorics, polynomials, quaternions, basic number theory. parallelized where appropriate, to leverage multi-core and multi-processor systems fully managed or (if available) using native libraries (Intel MKL, ACMS, CUDA, FFTW) provides a native facade for F# developers

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• Basic shadow mapping fails on NVIDIA card?

  - by James

  Recently I switched from an AMD Radeon HD 6870 card to an (MSI) NVIDIA GTX 670 for performance reasons. I found however that my implementation of shadow mapping in all my applications failed. In a very simple shadow POC project the problem appears to be that the scene being drawn never results in a draw to the depth map and as a result the entire depth map is just infinity, 1.0 (Reading directly from the depth component after draw (glReadPixels) shows every pixel is infinity (1.0), replacing the depth comparison in the shader with a comparison of the depth from the shadow map with 1.0 shadows the entire scene, and writing random values to the depth map and then not calling glClear(GL_DEPTH_BUFFER_BIT) results in a random noisy pattern on the scene elements - from which we can infer that the uploading of the depth texture and comparison within the shader are functioning perfectly.) Since the problem appears almost certainly to be in the depth render, this is the code for that: const int s_res = 1024; GLuint shadowMap_tex; GLuint shadowMap_prog; GLint sm_attr_coord3d; GLint sm_uniform_mvp; GLuint fbo_handle; GLuint renderBuffer; bool isMappingShad = false; //The scene consists of a plane with box above it GLfloat scene[] = { -10.0, 0.0, -10.0, 0.5, 0.0, 10.0, 0.0, -10.0, 1.0, 0.0, 10.0, 0.0, 10.0, 1.0, 0.5, -10.0, 0.0, -10.0, 0.5, 0.0, -10.0, 0.0, 10.0, 0.5, 0.5, 10.0, 0.0, 10.0, 1.0, 0.5, ... }; //Initialize the stuff used by the shadow map generator int initShadowMap() { //Initialize the shadowMap shader program if (create_program("shadow.v.glsl", "shadow.f.glsl", shadowMap_prog) != 1) return -1; const char* attribute_name = "coord3d"; sm_attr_coord3d = glGetAttribLocation(shadowMap_prog, attribute_name); if (sm_attr_coord3d == -1) { fprintf(stderr, "Could not bind attribute %s\n", attribute_name); return 0; } const char* uniform_name = "mvp"; sm_uniform_mvp = glGetUniformLocation(shadowMap_prog, uniform_name); if (sm_uniform_mvp == -1) { fprintf(stderr, "Could not bind uniform %s\n", uniform_name); return 0; } //Create a framebuffer glGenFramebuffers(1, &fbo_handle); glBindFramebuffer(GL_FRAMEBUFFER, fbo_handle); //Create render buffer glGenRenderbuffers(1, &renderBuffer); glBindRenderbuffer(GL_RENDERBUFFER, renderBuffer); //Setup the shadow texture glGenTextures(1, &shadowMap_tex); glBindTexture(GL_TEXTURE_2D, shadowMap_tex); glTexImage2D(GL_TEXTURE_2D, 0, GL_DEPTH_COMPONENT, s_res, s_res, 0, GL_DEPTH_COMPONENT, GL_FLOAT, NULL); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE); return 0; } //Delete stuff void dnitShadowMap() { //Delete everything glDeleteFramebuffers(1, &fbo_handle); glDeleteRenderbuffers(1, &renderBuffer); glDeleteTextures(1, &shadowMap_tex); glDeleteProgram(shadowMap_prog); } int loadSMap() { //Bind MVP stuff glm::mat4 view = glm::lookAt(glm::vec3(10.0, 10.0, 5.0), glm::vec3(0.0, 0.0, 0.0), glm::vec3(0.0, 1.0, 0.0)); glm::mat4 projection = glm::ortho<float>(-10,10,-8,8,-10,40); glm::mat4 mvp = projection * view; glm::mat4 biasMatrix( 0.5, 0.0, 0.0, 0.0, 0.0, 0.5, 0.0, 0.0, 0.0, 0.0, 0.5, 0.0, 0.5, 0.5, 0.5, 1.0 ); glm::mat4 lsMVP = biasMatrix * mvp; //Upload light source matrix to the main shader programs glUniformMatrix4fv(uniform_ls_mvp, 1, GL_FALSE, glm::value_ptr(lsMVP)); glUseProgram(shadowMap_prog); glUniformMatrix4fv(sm_uniform_mvp, 1, GL_FALSE, glm::value_ptr(mvp)); //Draw to the framebuffer (with depth buffer only draw) glBindFramebuffer(GL_FRAMEBUFFER, fbo_handle); glBindRenderbuffer(GL_RENDERBUFFER, renderBuffer); glBindTexture(GL_TEXTURE_2D, shadowMap_tex); glFramebufferTexture2D(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_TEXTURE_2D, shadowMap_tex, 0); glDrawBuffer(GL_NONE); glReadBuffer(GL_NONE); GLenum result = glCheckFramebufferStatus(GL_FRAMEBUFFER); if (GL_FRAMEBUFFER_COMPLETE != result) { printf("ERROR: Framebuffer is not complete.\n"); return -1; } //Draw shadow scene printf("Creating shadow buffers..\n"); int ticks = SDL_GetTicks(); glClear(GL_DEPTH_BUFFER_BIT); //Wipe the depth buffer glViewport(0, 0, s_res, s_res); isMappingShad = true; //DRAW glEnableVertexAttribArray(sm_attr_coord3d); glVertexAttribPointer(sm_attr_coord3d, 3, GL_FLOAT, GL_FALSE, 5*4, scene); glDrawArrays(GL_TRIANGLES, 0, 14*3); glDisableVertexAttribArray(sm_attr_coord3d); isMappingShad = false; glBindFramebuffer(GL_FRAMEBUFFER, 0); printf("Render Sbuf in %dms (GLerr: %d)\n", SDL_GetTicks() - ticks, glGetError()); return 0; } This is the full code for the POC shadow mapping project (C++) (Requires SDL 1.2, SDL-image 1.2, GLEW (1.5) and GLM development headers.) initShadowMap is called, followed by loadSMap, the scene is drawn from the camera POV and then dnitShadowMap is called. I followed this tutorial originally (Along with another more comprehensive tutorial which has disappeared as this guy re-configured his site but used to be here (404).) I've ensured that the scene is visible (as can be seen within the full project) to the light source (which uses an orthogonal projection matrix.) Shader utilities function fine in non-shadow-mapped projects. I should also note that at no point is the GL error state set. What am I doing wrong here and why did this not cause problems on my AMD card? (System: Ubuntu 12.04, Linux 3.2.0-49-generic, 64 bit, with the nvidia-experimental-310 driver package. All other games are functioning fine so it's most likely not a card/driver issue.)

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• JDK bug migration: components and subcomponents

  - by darcy

  One subtask of the JDK migration from the legacy bug tracking system to JIRA was reclassifying bugs from a three-level taxonomy in the legacy system, (product, category, subcategory), to a fundamentally two-level scheme in our customized JIRA instance, (component, subcomponent). In the JDK JIRA system, there is technically a third project-level classification, but by design a large majority of JDK-related bugs were migrated into a single "JDK" project. In the end, over 450 legacy subcategories were simplified into about 120 subcomponents in JIRA. The 120 subcomponents are distributed among 17 components. A rule of thumb used was that a subcategory had to have at least 50 bugs in it for it to be retained. Below is a listing the component / subcomponent classification of the JDK JIRA project along with some notes and guidance on which OpenJDK email addresses cover different areas. Eventually, a separate incidents project to host new issues filed at bugs.sun.com will use a slightly simplified version of this scheme. The preponderance of bugs and subcomponents for the JDK are in library-related areas, with components named foo-libs and subcomponents primarily named after packages. While there was an overall condensation of subcomponents in the migration, in some cases long-standing informal divisions in core libraries based on naming conventions in the description were promoted to formal subcomponents. For example, hundreds of bugs in the java.util subcomponent whose descriptions started with "(coll)" were moved into java.util:collections. Likewise, java.lang bugs starting with "(reflect)" and "(proxy)" were moved into java.lang:reflect. client-libs (Predominantly discussed on 2d-dev and awt-dev and swing-dev.) 2d demo java.awt java.awt:i18n java.beans (See beans-dev.) javax.accessibility javax.imageio javax.sound (See sound-dev.) javax.swing core-libs (See core-libs-dev.) java.io java.io:serialization java.lang java.lang.invoke java.lang:class_loading java.lang:reflect java.math java.net java.nio (Discussed on nio-dev.) java.nio.charsets java.rmi java.sql java.sql:bridge java.text java.util java.util.concurrent java.util.jar java.util.logging java.util.regex java.util:collections java.util:i18n javax.annotation.processing javax.lang.model javax.naming (JNDI) javax.script javax.script:javascript javax.sql org.openjdk.jigsaw (See jigsaw-dev.) security-libs (See security-dev.) java.security javax.crypto (JCE: includes SunJCE/MSCAPI/UCRYPTO/ECC) javax.crypto:pkcs11 (JCE: PKCS11 only) javax.net.ssl (JSSE, includes javax.security.cert) javax.security javax.smartcardio javax.xml.crypto org.ietf.jgss org.ietf.jgss:krb5 other-libs corba corba:idl corba:orb corba:rmi-iiop javadb other (When no other subcomponent is more appropriate; use judiciously.) Most of the subcomponents in the xml component are related to jaxp. xml jax-ws jaxb javax.xml.parsers (JAXP) javax.xml.stream (JAXP) javax.xml.transform (JAXP) javax.xml.validation (JAXP) javax.xml.xpath (JAXP) jaxp (JAXP) org.w3c.dom (JAXP) org.xml.sax (JAXP) For OpenJDK, most JVM-related bugs are connected to the HotSpot Java virtual machine. hotspot (See hotspot-dev.) build compiler (See hotspot-compiler-dev.) gc (garbage collection, see hotspot-gc-dev.) jfr (Java Flight Recorder) jni (Java Native Interface) jvmti (JVM Tool Interface) mvm (Multi-Tasking Virtual Machine) runtime (See hotspot-runtime-dev.) svc (Servicability) test core-svc (See serviceability-dev.) debugger java.lang.instrument java.lang.management javax.management tools The full JDK bug database contains entries related to legacy virtual machines that predate HotSpot as well as retired APIs. vm-legacy jit (Sun Exact VM) jit_symantec (Symantec VM, before Exact VM) jvmdi (JVM Debug Interface ) jvmpi (JVM Profiler Interface ) runtime (Exact VM Runtime) Notable command line tools in the $JDK/bin directory have corresponding subcomponents. tools appletviewer apt (See compiler-dev.) hprof jar javac (See compiler-dev.) javadoc(tool) (See compiler-dev.) javah (See compiler-dev.) javap (See compiler-dev.) jconsole launcher updaters (Timezone updaters, etc.) visualvm Some aspects of JDK infrastructure directly affect JDK Hg repositories, but other do not. infrastructure build (See build-dev and build-infra-dev.) licensing (Covers updates to the third party readme, licenses, and similar files.) release_eng (Release engineering) staging (Staging of web pages related to JDK releases.) The specification subcomponent encompasses the formal language and virtual machine specifications. specification language (The Java Language Specification) vm (The Java Virtual Machine Specification) The code for the deploy and install areas is not currently included in OpenJDK. deploy deployment_toolkit plugin webstart install auto_update install servicetags In the JDK, there are a number of cross-cutting concerns whose organization is essentially orthogonal to other areas. Since these areas generally have dedicated teams working on them, it is easier to find bugs of interest if these bugs are grouped first by their cross-cutting component rather than by the affected technology. docs doclet guides hotspot release_notes tools tutorial embedded build hotspot libraries globalization locale-data translation performance hotspot libraries The list of subcomponents will no doubt grow over time, but my inclination is to resist that growth since the addition of each subcomponent makes the system as a whole more complicated and harder to use. When the system gets closer to being externalized, I plan to post more blog entries describing recommended use of various custom fields in the JDK project.

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• How do i rotate a CALayer around a diagonal line?

  - by Mattias Wadman

  Hi. I'm trying to implement a flip animation to be used in board game like iPhone-application. The animation is supposed to look like a game piece that rotates and changes to the color of its back (kind of like an Reversi piece). I've managed to create an animation that flips the piece around its orthogonal axis, but when I try to flip it around a diagonal axis by changing the rotation around the z-axis the actual image also gets rotated (not surprisingly). Instead I would like to rotate the image "as is" around a diagonal axis. I have tried to change layer.sublayerTransform but with no success. Here is my current implementation. It works by doing a trick to resolve the issue of getting a mirrored image at the end of the animation. The solution is to not actually rotate the layer 180 degrees, instead it rotates it 90 degrees, changes image and then rotates it back. + (void)flipLayer:(CALayer *)layer toImage:(CGImageRef)image withAngle:(double)angle { const float duration = 0.5f; CAKeyframeAnimation *diag = [CAKeyframeAnimation animationWithKeyPath:@"transform.rotation.z"]; diag.duration = duration; diag.values = [NSArray arrayWithObjects: [NSNumber numberWithDouble:angle], [NSNumber numberWithDouble:0.0f], nil]; diag.keyTimes = [NSArray arrayWithObjects: [NSNumber numberWithDouble:0.0f], [NSNumber numberWithDouble:1.0f], nil]; diag.calculationMode = kCAAnimationDiscrete; CAKeyframeAnimation *flip = [CAKeyframeAnimation animationWithKeyPath:@"transform.rotation.y"]; flip.duration = duration; flip.values = [NSArray arrayWithObjects: [NSNumber numberWithDouble:0.0f], [NSNumber numberWithDouble:M_PI / 2], [NSNumber numberWithDouble:0.0f], nil]; flip.keyTimes = [NSArray arrayWithObjects: [NSNumber numberWithDouble:0.0f], [NSNumber numberWithDouble:0.5f], [NSNumber numberWithDouble:1.0f], nil]; flip.calculationMode = kCAAnimationLinear; CAKeyframeAnimation *replace = [CAKeyframeAnimation animationWithKeyPath:@"contents"]; replace.duration = duration / 2; replace.beginTime = duration / 2; replace.values = [NSArray arrayWithObjects:(id)image, nil]; replace.keyTimes = [NSArray arrayWithObjects: [NSNumber numberWithDouble:0.0f], nil]; replace.calculationMode = kCAAnimationDiscrete; CAAnimationGroup *group = [CAAnimationGroup animation]; group.removedOnCompletion = NO; group.duration = duration; group.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionLinear]; group.animations = [NSArray arrayWithObjects:diag, flip, replace, nil]; group.fillMode = kCAFillModeForwards; [layer addAnimation:group forKey:nil]; }

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• XML to be validated against multiple xsd schemas

  - by Michael Rusch

  I'm writing the xsd and the code to validate, so I have great control here. I would like to have an upload facility that adds stuff to my application based on an xml file. One part of the xml file should be validated against different schemas based on one of the values in the other part of it. Here's an example to illustrate: <foo> <name>Harold</name> <bar>Alpha</bar> <baz>Mercury</baz> <!-- ... more general info that applies to all foos ... --> <bar-config> <!-- the content here is specific to the bar named "Alpha" --> </bar-config> <baz-config> <!-- the content here is specific to the baz named "Mercury" --> </baz> </foo> In this case, there is some controlled vocabulary for the content of <bar>, and I can handle that part just fine. Then, based on the bar value, the appropriate xml schema should be used to validate the content of bar-config. Similarly for baz and baz-config. The code doing the parsing/validation is written in Java. Not sure how language-dependent the solution will be. Ideally, the solution would permit the xml author to declare the appropriate schema locations and what-not so that s/he could get the xml validated on the fly in a sufficiently smart editor. Also, the possible values for <bar> and <baz> are orthogonal, so I don't want to do this by extension for every possible bar/baz combo. What I mean is, if there are 24 possible bar values/schemas and 8 possible baz values/schemas, I want to be able to write 1 + 24 + 8 = 33 total schemas, instead of 1 * 24 * 8 = 192 total schemas. Also, I'd prefer to NOT break out the bar-config and baz-config into separate xml files if possible. I realize that might make all the problems much easier, as each xml file would have a single schema, but I'm trying to see if there is a good single-xml-file solution.

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• How do i rotate a CALayer around a diagonal axis?

  - by Mattias Wadman

  Hi, im trying to implement a flip animation to be used in board game like application. The animation is suppose to look like a game piece that rotate and change to the color of its back. I have managed to get a animation that flips around orthogonal axis, but when i try to flip around a diagonal axis by changing the rotation around the z-axis not surprisingly the actual image also gets rotated. Instead i would like to rotate the image as it is around a diagonal axis. I have tried to change layer.sublayerTransform but with no success. Here is the current implementation. It works by doing a trick to resolve the issue of getting a mirrored image at the end of the animation. The solution is to not actually rotate the layer 180 degrees, instead it rotates it 90 degrees, changes image and then rotates it back. + (void)flipLayer:(CALayer *)layer toImage:(CGImageRef)image withAngle:(double)angle { const float duration = 0.5f; CAKeyframeAnimation *diag = [CAKeyframeAnimation animationWithKeyPath:@"transform.rotation.z"]; diag.duration = duration; diag.values = [NSArray arrayWithObjects: [NSNumber numberWithDouble:angle], [NSNumber numberWithDouble:0.0f], nil]; diag.keyTimes = [NSArray arrayWithObjects: [NSNumber numberWithDouble:0.0f], [NSNumber numberWithDouble:1.0f], nil]; diag.calculationMode = kCAAnimationDiscrete; CAKeyframeAnimation *flip = [CAKeyframeAnimation animationWithKeyPath:@"transform.rotation.y"]; flip.duration = duration; flip.values = [NSArray arrayWithObjects: [NSNumber numberWithDouble:0.0f], [NSNumber numberWithDouble:M_PI / 2], [NSNumber numberWithDouble:0.0f], nil]; flip.keyTimes = [NSArray arrayWithObjects: [NSNumber numberWithDouble:0.0f], [NSNumber numberWithDouble:0.5f], [NSNumber numberWithDouble:1.0f], nil]; flip.calculationMode = kCAAnimationLinear; CAKeyframeAnimation *replace = [CAKeyframeAnimation animationWithKeyPath:@"contents"]; replace.duration = duration / 2; replace.beginTime = duration / 2; replace.values = [NSArray arrayWithObjects:(id)image, nil]; replace.keyTimes = [NSArray arrayWithObjects: [NSNumber numberWithDouble:0.0f], nil]; replace.calculationMode = kCAAnimationDiscrete; CAAnimationGroup *group = [CAAnimationGroup animation]; group.removedOnCompletion = NO; group.duration = duration; group.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionLinear]; group.animations = [NSArray arrayWithObjects:diag, flip, replace, nil]; group.fillMode = kCAFillModeForwards; [layer addAnimation:group forKey:nil]; }

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• velocity vector

  - by wanderer

  Hi, I am trying to simulate a collision. The collision is shown here http://www.freeimagehosting.net/image.php?c5ae01b476.jpg A particle falls down on a sphere and a collision between sphere and particle takes place. The sphere always remain stationary and the collision itself is not elastic. So if the particle falls directly n top of sphere, the velocity of particle will become zero. I was trying to set the velocity of particle to be zero after the collision. But that does not give good simulation when the collision does not occur on top of sphere but along the side of sphere. So now after the collision i need to make sure that the particle has a velocity which is orthogonal to the vector of the point of collision from the center of sphere. The velocity along the vector from center of sphere to point of collision should become zero. How do i do that? I am a bit mathematically challenged but i think it has something to do with dot product of vectors. Or maybe i am wrong :) I have the initial velocity vector and 'radiusvector' say :- 1)velocity <-1.03054, -1.56563, 1.33341e-016 2) radius vector <2.04406, 2.19587, 1.0514 Pseudo code for the problem is: foreach( particle particle in particlesCollections) { //sphere.x, sphere.y sphere.z give the center of the sphere dist = particle.pos-vector(sphere.x,sphere.y,sphere.z); //detect if a collision has taken place. if (dist.mag < sphere.radius) { rVector=dist/dist.mag*sphere.radius; particle.pos=vector(sphere.x,sphere.y,sphere.z) + rVector; //particle.Velocity gives the velocity vector of the particle at the time of collision //i need to modify particle.Velocity so that the component of velocity that runs along // with the rvector becomes zero as i have a non elsatic collision. The remaining //velocity that the particle will have is the one which runs along with tangent to the //rVector. The sphere remains stationary. //example values: particle.Velocity == <-1.03054, -1.56563, .006> //and rVector = <2.04406, 2.19587, 1.0514> } } Thanks

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