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• read text files containing binary data as a single matrix in matlab

  - by user1716595

  I have a text file which contains binary data in the following manner: 00000000000000000000000000000000001011111111111111111111111111111111111111111111111111111111110000000000000000000000000000000 00000000000000000000000000000000000000011111111111111111111111111111111111111111111111000111100000000000000000000000000000000 00000000000000000000000000000000000011111111111111111111111111111111111111111111111111111111100000000000000000000000000000000 00000000000000000000000000000000000111111111111111111111111111111111111111111111111111111111100000000000000000000000000000000 00000000000000000000000000000000000011111111111111111111111111111111111111111111111111111111100000000000000000000000000000000 00000000000000000000000000000000000000011111111111111111111111111111111111111111111111111111100000000000000000000000000000000 00000000000000000000000000000000000000011111111111111111111111111111111111111111111111000111110000000000000000000000000000000 00000000000000000000000000000000000000111111111111111111111111111111111111111111111111111111110000000000000000000000000000000 00000000000000000000000000000000000000000000111111111111111111111111111111111111110000000011100000000000000000000000000000000 00000000000000000000000000000000000000011111111111111111111111111111111111111111111111100111110000000000000000000000000000000 00000000000000000000000000000000000111111111111111111111111111111111111111111111111111110111110000000000000000000000000000000 00000000000000000000000000000000001111111111111111111111111111111111111111111111111111111111100000000000000000000000000000000 00000000000000000000000000000000000000001111111111111111111111111111111111111111111111000011100000000000000000000000000000000 00000000000000000000000000000000000000001111111111111111111111111111111111111111111111000011100000000000000000000000000000000 00000000000000000000000000000000000001111111111111111111111111111111111111111111111111111111000000000000000000000000000000000 00000000000000000000000000000000000000011111111111111111111111111111111111111111111110000011100000000000000000000000000000000 00000000000000000000000000000000000000000000011111111111111111111111111111111111100000000011100000000000000000000000000000000 00000000000000000000000000000000000000111111111111111111111111111111111111111111111111110111100000000000000000000000000000000 Plz note that each 1 or 0 is independent i.e the values are not decimal.I need to find the column wise sum of the file.There are 125 columns in all (here it is jumping onto the next line) and there are 840946 rows. I have tried textread,fscanf and a few other matlab commands but the result is that they all read each row in decimal format and create a 840946*1 array.I want to create a 840946*125 array to compute a column wise sum. Kindly help, Thanks!

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• JOGL hardware based shadow mapping - computing the texture matrix

  - by axel22

  I am implementing hardware shadow mapping as described here. I've rendered the scene successfully from the light POV, and loaded the depth buffer of the scene into a texture. This texture has correctly been loaded - I check this by rendering a small thumbnail, as you can see in the screenshot below, upper left corner. The depth of the scene appears to be correct - objects further away are darker, and that are closer to the light are lighter. However, I run into trouble while rendering the scene from the camera's point of view using the depth texture - the texture on the polygons in the scene is rendered in a weird, nondeterministic fashion, as shown in the screenshot. I believe I am making an error while computing the texture transformation matrix, but I am unsure where exactly. Since I have no matrix utilities in JOGL other then the gl[Load|Mult]Matrix procedures, I multiply the matrices using them, like this: void calcTextureMatrix() { glPushMatrix(); glLoadIdentity(); glLoadMatrixf(biasmatrix, 0); glMultMatrixf(lightprojmatrix, 0); glMultMatrixf(lightviewmatrix, 0); glGetFloatv(GL_MODELVIEW_MATRIX, shadowtexmatrix, 0); glPopMatrix(); } I obtained these matrices by using the glOrtho and gluLookAt procedures: glLoadIdentity() val wdt = width / 45 val hgt = height / 45 glOrtho(wdt, -wdt, -hgt, hgt, -45.0, 45.0) glGetFloatv(GL_MODELVIEW_MATRIX, lightprojmatrix, 0) glLoadIdentity() glu.gluLookAt( xlook + lightpos._1, ylook + lightpos._2, lightpos._3, xlook, ylook, 0.0f, 0.f, 0.f, 1.0f) glGetFloatv(GL_MODELVIEW_MATRIX, lightviewmatrix, 0) My bias matrix is: float[] biasmatrix = new float[16] { 0.5f, 0.f, 0.f, 0.f, 0.f, 0.5f, 0.f, 0.f, 0.f, 0.f, 0.5f, 0.f, 0.5f, 0.5f, 0.5f, 1.f } After applying the camera projection and view matrices, I do: glTexGeni(GL_S, GL_TEXTURE_GEN_MODE, GL_EYE_LINEAR) glTexGenfv(GL_S, GL_EYE_PLANE, shadowtexmatrix, 0) glEnable(GL_TEXTURE_GEN_S) for each component. Does anybody know why the texture is not being rendered correctly? Thank you.

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• Having trouble with projection matrix, need help

  - by Mr.UNOwen

  I'm having trouble with what appears to be the projection matrix. Given a wide enough of a screen, when a cube is on the left and right most edge, the left or right wall will appear stretched to the point that the front face is 1/10 the width of the side. So I do update the screen ratio along with the projection matrix and view port on screen resize, am I safe to assume all the trouble is from the matrix class? Also the cube follows the mouse, but it's only vertically aligned and ahead of the mouse when going left or right from the center of the screen. Perspective function call: * setPerspective * * @param fov: angle in radians * @param aspect: screen ratio w/h * @param near: near distance * @param far: far distance **/ void APCamera::setPerspective(GMFloat_t fov, GMFloat_t aspect, GMFloat_t near, GMFloat_t far) { GMFloat_t difZ = near - far; GMFloat_t *data; mProjection->clear(); //set to identity matrix data = mProjection->getData(); GMFloat_t v = 1.0f / tan(fov / 2.0f); data[_AP_MAA] = v / aspect; data[_AP_MBB] = v; data[_AP_MCC] = (far + near) / difZ; data[_AP_MCD] = -1.0f; data[_AP_MDD] = 0.0f; data[_AP_MDC] = 2.0f * far * near/ difZ; mRatio = aspect; mInvProjOutdated = true; mIsPerspective = true; } and... #define _AP_MAA 0 #define _AP_MAB 1 #define _AP_MAC 2 #define _AP_MAD 3 #define _AP_MBA 4 #define _AP_MBB 5 #define _AP_MBC 6 #define _AP_MBD 7 #define _AP_MCA 8 #define _AP_MCB 9 #define _AP_MCC 10 #define _AP_MCD 11 #define _AP_MDA 12 #define _AP_MDB 13 #define _AP_MDC 14 #define _AP_MDD 15

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• Flickering problem with world matrix

  - by gnomgrol

  I do have a pretty wierd problem today. As soon as I try to change my translation- or rotationmatrix for an object to something else than (0,0,0), the object starts to flicker (scaling works fine). It rapid and randomly switches between the spot it should be in and a crippled something. I first thought that the problem would be z-fighting, but now Im pretty sure it isn't. I have now clue at all what it could be, here are two screenshots of the two states the plant is switching between. I already used PIX, but could find anything of use (Im not a very good debugger anyway) I would appreciate any help, thanks a lot! Important code: D3DXMatrixIdentity(&World); D3DXVECTOR3 rotaxisX = D3DXVECTOR3(1.0f, 0.0f, 0.0f); D3DXVECTOR3 rotaxisY = D3DXVECTOR3(0.0f, 1.0f, 0.0f); D3DXVECTOR3 rotaxisZ = D3DXVECTOR3(0.0f, 0.0f, 1.0f); D3DXMATRIX temprot1, temprot2, temprot3; D3DXMatrixRotationAxis(&temprot1, &rotaxisX, 0); D3DXMatrixRotationAxis(&temprot2, &rotaxisY, 0); D3DXMatrixRotationAxis(&temprot3, &rotaxisZ, 0); Rotation = temprot1 *temprot2 * temprot3; D3DXMatrixTranslation(&Translation, 0.0f, 10.0f, 0.0f); D3DXMatrixScaling(&Scale, 0.02f, 0.02f, 0.02f); //Set objs world space using the transformations World = Translation * Rotation * Scale; shader: cbuffer cbPerObject { matrix worldMatrix; matrix viewMatrix; matrix projectionMatrix; }; // Change the position vector to be 4 units for proper matrix calculations. input.position.w = 1.0f; // Calculate the position of the vertex against the world, view, and projection matrices. output.position = mul(input.position, worldMatrix); output.position = mul(output.position, viewMatrix); output.position = mul(output.position, projectionMatrix);

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• How do I adjust the origin of rotation for a group of sprites?

  - by Jon

  I am currently grouping sprites together, then applying a rotation transformation on draw: private void UpdateMatrix(ref Vector2 origin, float radians) { Vector3 matrixorigin = new Vector3(origin, 0); _rotationMatrix = Matrix.CreateTranslation(-matrixorigin) * Matrix.CreateRotationZ(radians) * Matrix.CreateTranslation(matrixorigin); } Where the origin is the Centermost point of my group of sprites. I apply this transformation to each sprite in the group. My problem is that when I adjust the point of origin, my entire sprite group will re-position itself on screen. How could I differentiate the point of rotation used in the transformation, from the position of the sprite group? Is there a better way of creating this transformation matrix? EDIT Here is the relevant part of the Draw() function: Matrix allTransforms = _rotationMatrix * camera.GetTransformation(); spriteBatch.Begin(SpriteSortMode.BackToFront, null, null, null, null, null, allTransforms); for (int i = 0; i < _map.AllParts.Count; i++) { for (int j = 0; j < _map.AllParts[0].Count; j++) { spriteBatch.Draw(_map.AllParts[i][j].Texture, _map.AllParts[i][j].Position, null, Color.White, 0, _map.AllParts[i][j].Origin, 1.0f, SpriteEffects.None, 0f); } } This all works fine, again, the problem is that when a rotation is set and the point of origin is changed, the sprite group's position is offset on screen. I am trying to figure out a way to adjust the point of origin without causing a shift in position. EDIT 2 At this point, I'm looking for workarounds as this is not working. Does anyone know of a better way to rotate a group of sprites in XNA? I need a method that will allow me to modify the point of rotation (origin) without affecting the position of the sprite group on screen.

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• Scaling along an arbitrary axis (Dealing with non-uniform scale)

  - by Jon

  I'm trying to build my own little engine to get more familiar with the concepts of 3D programming. I have a transform class that on each frame it creates a Scaling Matrix (S), a Rotation Matrix from a Quaternion (R) and concatenates them together (S*R). Once i have SR, I insert the translation values into the bottom of the three columns. So i end up with a transformation matrix that looks like: [SR SR SR 0] [SR SR SR 0] [SR SR SR 0] [tx ty tz 1] This works perfectly in all cases except when rotating an object that has a non-uniform scale. For example a unit cube with ScaleX = 4, ScaleY = 2, ScaleZ = 1 will give me a rectangular box that is 4 times as wide as the depth and twice as high as the depth. If i then translate this around, the box stays the same and looks normal. The problem happens whenever I try to rotate this scaled box. The shape itself becomes distorted and it appears as though the Scale factors are affecting the object on the World X,Y,Z axis rather than the local X,Y,Z axis of the object. I've done some pretty extensive research through a variety of textbooks (Eberly, Moller/Hoffman, Phar etc) and there isn't a ton there to go off of. Online, most of the answers say to avoid non-uniform scaling which I understand the desire to avoid it, but I'd still like to figure out how to support it. The only thing I can think off is that when constructing a Scale Matrix: [sx 0 0 0] [0 sy 0 0] [0 0 sz 0] [0 0 0 1] This is scaling along the World Axis instead of the object's local Direction, Up and Right vectors or it's local Z, Y, X axis. Does anyone have any tips or ideas on how to handle construction a transformation matrix that allows for non-uniform scaling and rotation? Thanks!

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• D3DXMatrixDecompose gives different quaternion than D3DXQuaternionRotationMatrix

  - by Fraser

  In trying to solve this problem, I tracked down the problem to the conversion of the rotation matrix to quaternion. In particular, consider the following matrix: -0.02099178 0.9997436 -0.008475631 0 0.995325 0.02009799 -0.09446743 0 0.09427284 0.01041905 0.9954919 0 0 0 0 1 SlimDX.Quaternion.RotationMatrix (which calls D3DXQuaternionRotationMatrix gives a different answer than SlimDX.Matrix.Decompose (which uses D3DXMatrixDecompose). The answers they give (after being normalized) are: X Y Z W Quaternion.RotationMatrix -0.05244324 0.05137424 0.002209336 0.9972991 Matrix.Decompose 0.6989997 0.7135442 -0.03674842 -0.03006023 Which are totally different (note the signs of X, Z, and W are different). Note that these aren't q/-q (two quaternions that represent the same rotation); they face completely different directions. I've noticed that with matrices for rotations very close to that one (successive frames in the animation) that the Matrix.Decompose version gives a solution that flips around wildly and occasionally goes into the desired position, while the Quaternion.RotationMatrix version gives solutions that are stable but go in the wrong direction. This is only for the right arm in my animation -- for the left arm, both functions give the correct solution, which is the same quaternion within error tolerances. This makes me think that there's some sort of numeric instability or weird stuff with signs going on. I tried implementing this and then this, but both gave me a completely incorrect solution (even for the matricies where the SlimDX ones were working correctly) -- maybe the rows and columns are flipped?

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• Rotation matrix for a 3D vector

  - by Shashwat

  I have a direction vector on which I have to apply some rotation to align it to positive z-axis. To use Matrix.CreateRotationX(angle) of XNA, I need the angle for which I'd have to compute cos or tan inverse. I think this is a complex task to do. Also, eventually those are also converted to sin(angle) and cos(angle) in the matrix. Is there any inbuilt way to create rotation matrix from a 3D vector? However, I can write the function but still asking if there is one already there.

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• Translating an object along its heading

  - by Kuros

  I am working on a simulation that requires me to have several objects moving around in 3D space (text output of their current position on the grid and heading is fine, I do not need graphics), and I am having some trouble getting objects to move along their relative headings. I have a basic understanding of vectors and matrices. I am using a vector to represent their position, and I am also using Euler Angles. I can translate one of my entities with a matrix along whatever axis, and I can alter their heading. For example, if I have an entity at (order is XYZ) 1, 1, 1, with a heading of 0, I can apply a translation matrix to get them to talk to 1, 1, 2 fine. However, if I change their heading to 270, they still walk to 1, 1, 3, instead of 2, 1, 2 as I desire. I have a feeling that my problem lies in not translating my matrix from world space to object space, but I am not sure how to go about that. How can I do this? Addition: I am using 3D vectors to represent their current position and their heading (using the three euler angles). For now, all I want to do is have an entity walk in a square, reporting their current position at each step. So, assuming it starts at 10, 10, 10 I want it to walk as follows: 10,10,10 -> 10, 10, 15 10, 10, 15 -> 5, 10, 15 5, 10, 15 -> 5, 10, 10 5, 10, 10 -> 10, 10, 10 My 1 Z unit translation matrix is as follows: [1 0 0 0] [0 1 0 0] [0 0 1 1] [0 0 0 1] My rotation matrix is as follows: [0 0 1 0] [0 1 0 0] [-1 0 0 0] [0 0 0 1]

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• Managing inverse relationships without CoreData

  - by Nathaniel Martin

  This is a question for Objective-J/Cappuccino, but I added the cocoa tag since the frameworks are so similar. One of the downsides of Cappuccino is that CoreData hasn't been ported over yet, so you have to make all your model objects manually. In CoreData, your inverse relationships get managed automatically for you... if you add an object to a to-many relationship in another object, you can traverse the graph in both directions. Without CoreData, is there any clean way to setup those inverse relationships automatically? For a more concrete example, let's take the typical Department and Employees example. To use rails terminology, a Department object has-many Employees, and an Employee belongs-to a Department. So our Department model has an NSMutableSet (or CPMutableSet ) "employees" that contains a set of Employees, and our Employee model has a variable "department" that points back to the Department model that owns it. Is there an easy way to make it so that, when I add a new Employee model into the set, the inverse relationship (employee.department) automatically gets set? Or the reverse: If I set the department model of an employee, then it automatically gets added to that department's employee set? Right know I'm making an object, "ValidatedModel" that all my models subclass, which adds a few methods that setup the inverse relationships, using KVO. But I'm afraid that I'm doing a lot of pointless work, and that there's already an easier way to do this. Can someone put my concerns to rest?

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• Inverse Logistic Function / Reverse Sigmoid Function

  - by Chanq

  I am currently coding up a fuzzy logic library in java. I have found the equations for all the standard functions - Grade, inverseGrade, Triangle, Trapezoid, Gaussian. However, I can't find the inverse of the sigmoid/ logistic function. The way I have written the logistic function is java is : //f(x) = 1/(1+e(-x)) public double logistic(double x){ return (1/(1+(Math.exp(-x))); } But I can't work out or find the inverse anywhere. My algebraic/calculus abilities are fairly limited, hence why I haven't been able to work out the inverse of the function. Any hints or pointers would be a big help. Thanks

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• TSQL Challenge 30 - A Matrix Transposition challenge in TSQL

  This is a matrix transposition challenge. Your job is to change the position of the numbres in a 5x5 matrix. SQL Server monitoring made easy "Keeping an eye on our many SQL Server instances is much easier with SQL Response." Mike Lile.Download a free trial of SQL Response now.

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• TIP: Half Size Triangular Matrix

  Learn about a technique that allows you to use half the data storage when you have a symmetric distance matrix or other similar triangular matrix.

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• Matrix Math in SQL

  Relational Datbases have tables as data structures, not arrays. This makes it tricky and slow to do matrix operations, but it doesn't mean it is impossible to do. Joe gives the Celko Slant on how to go about doing Matrix Math in SQL. 12 essential tools for database professionalsThe SQL Developer Bundle contains 12 tools designed with the SQL Server developer and DBA in mind. Try it now.

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• Android Rotate Matrix

  - by jitm

  Hello, I have matrix. This matrix represents array x and y coordinates. For example float[] src = {7,1,7,2,7,3,7,4}; I need to rotate this coordinates to 90 degrees. I use android.graphics.Matrix like this: float[] src = {7,1,7,2,7,3,7,4}; float[] dist = new float[8]; Matrix matrix = new Matrix(); matrix.preRotate(90.0f); matrix.mapPoints(dist,src); after operation rotate I have array with next values -1.0 7.0 -2.0 7.0 -3.0 7.0 -4.0 7.0 Its is good for area with 360 degrees. And how do rotate in area from 0 to 90? I need set up center of circle in this area but how ? Thanks.

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• How to browse a Matrix returned by the OpenCV2.0 Canny() function ?

  - by user290613

  Hi all, I've been browsing the web to get an answer but no way to put my hand on it. I call the Canny function that fills me a matrix Canny(src, dst, 220, 299, 3 ); the dst variable is now a Matrix that is according to me of type CV_8UC1, 8bit, 1channel. Now I would like to browse this matrix according to rows and columns, so there was a trick that I've seen on stackoverflow dst.at<uchar*>(3, 5) In my case it crashes. (Assertion Failed, unknown function, cxmat.hpp line 450) My matrix information are myMatrix.width() = 181 myMatrix.height() = 65 One more thing, when I do std::cout << dst.depth() << std::endl; It always retrieves me 0 and not 8 (which I guess Im suppose to get) Thank you very much for all who will reply,

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• Multithreaded Multiplication of Large Non-sparse, Non-square Matrices in C/C++

  - by andand

  All, I'm looking for recommendations for C or C++ libraries (preferably open source) that use multi-threaded techniques to multiply large, non-square, (e.g. 65536xn in size where n < 65536) non-sparse matrices. Thanks. -&&

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• Simple matrix example using C++ template class

  - by skyeagle

  I am trying to write a trivial Matrix class, using C++ templates in an attempt to brush up my C++, and also to explain something to a fellow coder. This is what I have som far: template class<T> class Matrix { public: Matrix(const unsigned int rows, const unsigned int cols); Matrix(const Matrix& m); Matrix& operator=(const Matrix& m); ~Matrix(); unsigned int getNumRows() const; unsigned int getNumCols() const; template <class T> T getCellValue(unsigned int row, unsigned col) const; template <class T> void setCellValue(unsigned int row, unsigned col, T value) const; private: // Note: intentionally NOT using smart pointers here ... T * m_values; }; template<class T> inline T Matrix::getCellValue(unsigned int row, unsigned col) const { } template<class T> inline void Matrix::setCellValue(unsigned int row, unsigned col, T value) { } I'm stuck on the ctor, since I need to allocate a new[] T, it seems like it needs to be a template method - however, I'm not sure I have come accross a templated ctor before. How can I implemnt the ctor?

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• Multithreaded Multiplication a Large Non-sparse, Non-square Matrices in C/C++

  - by andand

  All, I'm looking for recommendations for C or C++ libraries (preferably open source) that use multi-threaded techniques to multiply large, non-square, (e.g. 65536xn in size where n < 65536) non-sparse matrices. Thanks. -&&

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• How can I find the dimensions of a matrix in Python?

  - by PBD10017

  How can I find the dimensions of a matrix in Python. Len(A) returns only one variable. Edit: Hi Thanks. close = dataobj.get_data(timestamps, symbols, closefield) Is (I assume) generating a matrix of integers (less likely strings). I need to find the size of that matrix, so I can run some tests without having to iterate through all of the elements. As far as the data type goes, I assume it's an array of arrays (or list of lists).

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• averaging matrix efficiently

  - by user248237

  in Python, given an n x p matrix, e.g. 4 x 4, how can I return a matrix that's 4 x 2 that simply averages the first two columns and the last two columns for all 4 rows of the matrix? e.g. given: a = array([[1, 2, 3, 4], [5, 6, 7, 8], [9, 10, 11, 12], [13, 14, 15, 16]]) return a matrix that has the average of a[:, 0] and a[:, 1] and the average of a[:, 2] and a[:, 3]. I want this to work for an arbitrary matrix of n x p assuming that the number of columns I am averaging of n is obviously evenly divisible by n. let me clarify: for each row, I want to take the average of the first two columns, then the average of the last two columns. So it would be: 1 + 2 / 2, 3 + 4 / 2 <- row 1 of new matrix 5 + 6 / 2, 7 + 8 / 2 <- row 2 of new matrix, etc. which should yield a 4 by 2 matrix rather than 4 x 4. thanks.

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• how to retain the animated position in opengl es 2.0

  - by Arun AC

  I am doing frame based animation for 300 frames in opengl es 2.0 I want a rectangle to translate by +200 pixels in X axis and also scaled up by double (2 units) in the first 100 frames Then, the animated rectangle has to stay there for the next 100 frames. Then, I want the same animated rectangle to translate by +200 pixels in X axis and also scaled down by half (0.5 units) in the last 100 frames. I am using simple linear interpolation to calculate the delta-animation value for each frame. Pseudo code: The below drawFrame() is executed for 300 times (300 frames) in a loop. float RectMVMatrix[4][4] = {1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1 }; // identity matrix int totalframes = 300; float translate-delta; // interpolated translation value for each frame float scale-delta; // interpolated scale value for each frame // The usual code for draw is: void drawFrame(int iCurrentFrame) { // mySetIdentity(RectMVMatrix); // comment this line to retain the animated position. mytranslate(RectMVMatrix, translate-delta, X_AXIS); // to translate the mv matrix in x axis by translate-delta value myscale(RectMVMatrix, scale-delta); // to scale the mv matrix by scale-delta value ... // opengl calls glDrawArrays(...); eglswapbuffers(...); } The above code will work fine for first 100 frames. in order to retain the animated rectangle during the frames 101 to 200, i removed the "mySetIdentity(RectMVMatrix);" in the above drawFrame(). Now on entering the drawFrame() for the 2nd frame, the RectMVMatrix will have the animated value of first frame e.g. RectMVMatrix[4][4] = { 1.01, 0, 0, 2, 0, 1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1 };// 2 pixels translation and 1.01 units scaling after first frame This RectMVMatrix is used for mytranslate() in 2nd frame. The translate function will affect the value of "RectMVMatrix[0][0]". Thus translation affects the scaling values also. Eventually output is getting wrong. How to retain the animated position without affecting the current ModelView matrix? =========================================== I got the solution... Thanks to Sergio. I created separate matrices for translation and scaling. e.g.CurrentTranslateMatrix[4][4], CurrentScaleMatrix[4][4]. Then for every frame, I reset 'CurrentTranslateMatrix' to identity and call mytranslate( CurrentTranslateMatrix, translate-delta, X_AXIS) function. I reset 'CurrentScaleMatrix' to identity and call myscale(CurrentScaleMatrix, scale-delta) function. Then, I multiplied these 'CurrentTranslateMatrix' and 'CurrentScaleMatrix' to get the final 'RectMVMatrix' Matrix for the frame. Pseudo Code: float RectMVMatrix[4][4] = {0}; float CurrentTranslateMatrix[4][4] = {0}; float CurrentScaleMatrix[4][4] = {0}; int iTotalFrames = 300; int iAnimationFrames = 100; int iTranslate_X = 200.0f; // in pixels float fScale_X = 2.0f; float scaleDelta; float translateDelta_X; void DrawRect(int iTotalFrames) { mySetIdentity(RectMVMatrix); for (int i = 0; i< iTotalFrames; i++) { DrawFrame(int iCurrentFrame); } } void getInterpolatedValue(int iStartFrame, int iEndFrame, int iTotalFrame, int iCurrentFrame, float *scaleDelta, float *translateDelta_X) { float fDelta = float ( (iCurrentFrame - iStartFrame) / (iEndFrame - iStartFrame)) float fStartX = 0.0f; float fEndX = ConvertPixelsToOpenGLUnit(iTranslate_X); *translateDelta_X = fStartX + fDelta * (fEndX - fStartX); float fStartScaleX = 1.0f; float fEndScaleX = fScale_X; *scaleDelta = fStartScaleX + fDelta * (fEndScaleX - fStartScaleX); } void DrawFrame(int iCurrentFrame) { getInterpolatedValue(0, iAnimationFrames, iTotalFrames, iCurrentFrame, &scaleDelta, &translateDelta_X) mySetIdentity(CurrentTranslateMatrix); myTranslate(RectMVMatrix, translateDelta_X, X_AXIS); // to translate the mv matrix in x axis by translate-delta value mySetIdentity(CurrentScaleMatrix); myScale(RectMVMatrix, scaleDelta); // to scale the mv matrix by scale-delta value myMultiplyMatrix(RectMVMatrix, CurrentTranslateMatrix, CurrentScaleMatrix);// RectMVMatrix = CurrentTranslateMatrix*CurrentScaleMatrix; ... // opengl calls glDrawArrays(...); eglswapbuffers(...); } I maintained this 'RectMVMatrix' value, if there is no animation for the current frame (e.g. 101th frame onwards). Thanks, Arun AC

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• Find points whose pairwise distances approximate a given distance matrix

  - by Stephan Kolassa

  Problem. I have a symmetric distance matrix with entries between zero and one, like this one: D = ( 0.0 0.4 0.0 0.5 ) ( 0.4 0.0 0.2 1.0 ) ( 0.0 0.2 0.0 0.7 ) ( 0.5 1.0 0.7 0.0 ) I would like to find points in the plane that have (approximately) the pairwise distances given in D. I understand that this will usually not be possible with strictly correct distances, so I would be happy with a "good" approximation. My matrices are smallish, no more than 10x10, so performance is not an issue. Question. Does anyone know of an algorithm to do this? Background. I have sets of probability densities between which I calculate Hellinger distances, which I would like to visualize as above. Each set contains no more than 10 densities (see above), but I have a couple of hundred sets. What I did so far. I did consider posting at math.SE, but looking at what gets tagged as "geometry" there, it seems like this kind of computational geometry question would be more on-topic here. If the community thinks this should be migrated, please go ahead. This looks like a straightforward problem in computational geometry, and I would assume that anyone involved in clustering might be interested in such a visualization, but I haven't been able to google anything. One simple approach would be to randomly plonk down points and perturb them until the distance matrix is close to D, e.g., using Simulated Annealing, or run a Genetic Algorithm. I have to admit that I haven't tried that yet, hoping for a smarter way. One specific operationalization of a "good" approximation in the sense above is Problem 4 in the Open Problems section here, with k=2. Now, while finding an algorithm that is guaranteed to find the minimum l1-distance between D and the resulting distance matrix may be an open question, it still seems possible that there at least is some approximation to this optimal solution. If I don't get an answer here, I'll mail the gentleman who posed that problem and ask whether he knows of any approximation algorithm (and post any answer I get to that here).

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• Data Movement and the Decision Matrix

  - by BuckWoody

  Maybe it’s my military background, or maybe I’ve always had this predilection, but I like to use two devices when I need to make a complex decision: A checklist and a decision matrix. I like to use a checklist because it ensures that I remember the big bits of what I need to do, and brings up questions or areas that I didn’t think about when evaluating options for the decision. And the decision matrix – that’s the thing I use to actually lay out those options. It’s simply a spreadsheet-like grid (I use Excel, but paper and pencil works as well) that lays out the requirements or advantages for the decision across the top, and the options I have on the left-hand side. Then in the “cells” I put whether or not that option on the left will meet the requirement in that column. I then simply “weight” each cell to organize the choices by best-fit. The right answer (or answers) will float right to the top. I was asked yesterday about options for moving data in SQL Server to another system. There are just dozens of ways to do this, from bcp to Replication, each with certain advantages and costs. But asking the questions for the top row first helped me show the person that it isn’t a particular technology that is important, it’s laying out those requirements and thinking about which elements are more important than the other. For instance, is it more important to have the data moved all the time, or is it OK if that happens once in a while? Does the data have to move in two directions or just one? All of these will help that answer jump right out. Try it sometime – it’s a great learning exercise, since it will force you to focus on filling out the matrix. The answer is out there, Neo. Share this post: email it! | bookmark it! | digg it! | reddit! | kick it! | live it!

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• Binding BoundingSpheres to a world matrix in XNA

  - by NDraskovic

  I made a program that loads the locations of items on the scene from a file like this: using (StreamReader sr = new StreamReader(OpenFileDialog1.FileName)) { String line; while ((line = sr.ReadLine()) != null) { red = line.Split(','); model = row[0]; x = row[1]; y = row[2]; z = row[3]; elements.Add(Convert.ToInt32(model)); data.Add(new Vector3(Convert.ToSingle(x), Convert.ToSingle(y), Convert.ToSingle(z))); sfepheres.Add(new BoundingSphere(new Vector3(Convert.ToSingle(x), Convert.ToSingle(y), Convert.ToSingle(z)), 1f)); } I also have a list of BoundingSpheres (called spheres) that adds a new bounding sphere for each line from the file. In this program I have one item (a simple box) that moves (it has its world matrix called matrixBox), and other items are static entire time (there is a world matrix that holds those elements called simply world). The problem i that when I move the box, bounding spheres move with it. So how can I bind all BoundingSpheres (except the one corresponding to the box) to the static world matrix so that they stay in their place when the box moves?

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