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  • Sparse (Pseudo) Infinite Grid Data Structure for Web Game

    - by Ming
    I'm considering trying to make a game that takes place on an essentially infinite grid. The grid is very sparse. Certain small regions of relatively high density. Relatively few isolated nonempty cells. The amount of the grid in use is too large to implement naively but probably smallish by "big data" standards (I'm not trying to map the Internet or anything like that) This needs to be easy to persist. Here are the operations I may want to perform (reasonably efficiently) on this grid: Ask for some small rectangular region of cells and all their contents (a player's current neighborhood) Set individual cells or blit small regions (the player is making a move) Ask for the rough shape or outline/silhouette of some larger rectangular regions (a world map or region preview) Find some regions with approximately a given density (player spawning location) Approximate shortest path through gaps of at most some small constant empty spaces per hop (it's OK to be a bad approximation often, but not OK to keep heading the wrong direction searching) Approximate convex hull for a region Here's the catch: I want to do this in a web app. That is, I would prefer to use existing data storage (perhaps in the form of a relational database) and relatively little external dependency (preferably avoiding the need for a persistent process). Guys, what advice can you give me on actually implementing this? How would you do this if the web-app restrictions weren't in place? How would you modify that if they were? Thanks a lot, everyone!

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  • Grid overlayed on image using javascript, need help getting grid coordinates.

    - by Alos
    Hi I am fairly new to javascript and could use some help, I am trying to overlay a grid on top of an image and then be able to have the user click on the grid and get the grid coordinate from the box that the user clicked. I have been working with the code from the following stackoverflow question: Creating a grid overlay over image. link text Here is the code that I have so far: <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> </script> <script type="text/javascript"> var SetGrid = function(el, sz, nr, nc){ //get number of rows/columns according to the 'grid' size //numcols = el.getSize().x/sz; //numrows = el.getSize().y/sz; numcols = 48; numrows = 32; //create table element for injecting cols/rows var gridTable = new Element('table', { 'id' : 'gridTable', 'styles' : { 'width' : el.getSize().x, 'height' : el.getSize().y, 'top' : el.getCoordinates().top, 'left' : el.getCoordinates().left } }); //inject rows/cols into gridTable for (row = 1; row<=numrows; row++){ thisRow = new Element('tr', { 'id' : row, 'class' : 'gridRow' }); for(col = 1; col<=numcols; col++){ thisCol = new Element('td', { 'id' : col, 'class' : 'gridCol0' }); //each cell gets down/up over event... down starts dragging|up stops|over draws area if down was fired thisCol.addEvents({ 'mousedown' : function(){ dragFlag = true; startRow = this.getParent().get('id'); startCol = this.get('id'); }, 'mouseup' : function(){ dragFlag = false; }, 'mouseover' : function(){ if (dragFlag==true){ this.set('class', 'gridCol'+$$('#lvlSelect .on').get('value')); } }, 'click' : function(){ //this.set('class', 'gridCol'+$$('#lvlSelect .on').get('id').substr(3, 1) ); str = $$('#lvlSelect .on').get('id'); alert(str.substr(2, 3)); } }); thisCol.inject(thisRow, 'bottom'); }; thisRow.inject(gridTable, 'bottom'); }; gridTable.inject(el.getParent()); } //sens level selector func var SetSensitivitySelector = function(el, sz, nr, nc){ $$('#lvlSelect ul li').each(function(el){ el.addEvents({ 'click' : function(){ $$('#lvlSelect ul li').set('class', ''); this.set('class', 'on'); }, 'mouseover' : function(){ el.setStyle('cursor','pointer'); }, 'mouseout' : function(){ el.setStyle('cursor',''); } }); }); } //execute window.addEvent('load', function(){ SetGrid($('imagetomap'), 32); SetSensitivitySelector(); }); var gridSize = { x: 48, y: 32 }; var img = document.getElementById('imagetomap'); img.onclick = function(e) { if (!e) e = window.event; alert(Math.floor(e.offsetX/ gridSize.x) + ', ' + Math.floor(e.offsetY / gridSize.y)); } </script> <style> #imagetomapdiv { float:left; display: block; } #gridTable { border:1px solid red; border-collapse:collapse; position:absolute; z-index:5; } #gridTable td { opacity:0.2; filter:alpha(opacity=20); } #gridTable .gridCol0 { border:1px solid gray; background-color: none; } #gridTable .gridCol1 { border:1px solid gray; background-color: green; } #gridTable .gridCol2 { border:1px solid gray; background-color: blue; } #gridTable .gridCol3 { border:1px solid gray; background-color: yellow; } #gridTable .gridCol4 { border:1px solid gray; background-color: orange; } #gridTable .gridCol5 { border:1px solid gray; background-color: red; } #lvlSelect ul {float: left; display:block; position:relative; margin-left: 20px; padding: 10px; } #lvlSelect ul li { width:40px; text-align:center; display:block; border:1px solid black; position:relative; padding: 10px; list-style:none; opacity:0.2; filter:alpha(opacity=20); } #lvlSelect ul li.on { opacity:1; filter:alpha(opacity=100); } #lvlSelect ul #li0 { background-color: none; } #lvlSelect ul #li1 { background-color: green; } #lvlSelect ul #li2 { background-color: blue; } #lvlSelect ul #li3 { background-color: yellow; } #lvlSelect ul #li4 { background-color: orange; } #lvlSelect ul #li5 { background-color: red; } </style> </div> <div id="lvlSelect"> <ul> <li value="0" id="li0">0</li> <li value="1" id="li1">1</li> <li value="2" id="li2">2</li> <li value="3" id="li3">3</li> <li value="4" id="li4">4</li> <li value="5" id="li5" class="on">5</li> </ul> </div> In this example the grid box changes color when the image is grid box is clicked, but I would like to be able to have the coordinates of the box. Any help would be great. Thank you

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  • OpenGL, problems with GL_MODELVIEW GL_PROJECTION...

    - by Marcos Roriz
    Guys, I'm trying to finish up my homework but I'm having some problems here on these models on openGL... any Idea why is my draw not happening? One thing that strange is that if I change to gluPerspective it works.. #include <GL/glut.h> #include <stdlib.h> #include <stdio.h> static int shoulder = 0; static int elbow = 0; void init(void) { glClearColor(1.0, 1.0, 1.0, 0.0); } void display(void) { glClear(GL_COLOR_BUFFER_BIT); glPushMatrix(); /* BASE */ glRotatef((GLfloat) shoulder, 0.0, 0.0, 1.0); glTranslatef(1.0, 0.0, 0.0); glPushMatrix(); //glScalef(2.0, 0.4, 1.0); glBegin(GL_QUADS); glColor3f(0, 0, 0); glVertex2f(0.0, 0.0); glVertex2f(0.0, 10.0); glVertex2f(10.0, 10.0); glVertex2f(10.0, 0.0); glEnd(); glPopMatrix(); glPopMatrix(); glutSwapBuffers(); } void reshape(int w, int h) { glViewport(0, 0, (GLsizei) w, (GLsizei) h); glMatrixMode(GL_PROJECTION); glLoadIdentity(); glOrtho((GLfloat)-w/2, (GLfloat)w/2, (GLfloat)-h/2, (GLfloat)h/2, -1.0, 1.0); // modo de projecao ortogonal glMatrixMode(GL_MODELVIEW); glLoadIdentity(); glTranslatef(0.0, 0.0, -5.0); } void keyboard(unsigned char key, int x, int y) { switch (key) { case 's': shoulder = (shoulder + 5) % 360; glutPostRedisplay(); break; case 'S': shoulder = (shoulder - 5) % 360; glutPostRedisplay(); break; case 'e': elbow = (elbow + 5) % 360; glutPostRedisplay(); break; case 'E': elbow = (elbow - 5) % 360; glutPostRedisplay(); break; case 27: exit(0); break; default: break; } } int main(int argc, char** argv) { glutInit(&argc, argv); glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB); glutInitWindowSize(800, 400); glutInitWindowPosition(100, 100); glutCreateWindow(argv[0]); init(); glutDisplayFunc(display); glutReshapeFunc(reshape); glutKeyboardFunc(keyboard); glutMainLoop(); return 0; }

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  • Is there a substitute for blockproc in Matlab?

    - by SetchSen
    I've been using blockproc for processing images blockwise. Unfortunately, blockproc is part of the Image Processing Toolbox, which I don't have on my personal computer. Is there a combination of functions in base Matlab that can substitute for blockproc? My initial guess was to use im2col to transform each block into columns, and then arrayfun to process each column. Then I realized that im2col is also a part of the Image Processing Toolbox, so that doesn't solve my problem.

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  • Is there a name for this type of algorithm?

    - by rehanift
    I have a 2 dimensional array forming a table: [color][number][shape ] ------------------------- [black][10 ][square ] [black][10 ][circle ] [red ][05 ][triangle] [red ][04 ][triangle] [green][11 ][oval ] and what I want to do is group largest common denominators, such that we get: 3 groups group #1: color=black, number=10, shapes = [square, circle] group #2: color=red, shape=triange, numbers = [05,04] group #3: color=green, number=11, shape = oval I wrote code that will handle a 2 "column" scenario, then I needed to adjusted it for 3 and I was figuring I might as well do it for n. I wanted to check first if there is some literature around this but I can't think of what to start looking for!

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  • How to interpolate rotations?

    - by uhuu
    I have two vectors describing rotations; a start rotation A and a target rotation B. How would I best go about interpolating A by a factor F to approach B? Using a simple lerp on the vectors fails to work when more than one dimension needs to be interpolated (i.e. produces undesirable rotations). Maybe building quaternions from the rotation vectors and using slerp is the way to go. But how, then, could I extract a vector describing the new rotation from the resulting quaternion? Thanks in advance.

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  • Is it possible to shuffle a 2D matrix while preserving row AND column frequencies?

    - by j_random_hacker
    Suppose I have a 2D array like the following: GACTG AGATA TCCGA Each array element is taken from a small finite set (in my case, DNA nucleotides -- {A, C, G, T}). I would like to randomly shuffle this array somehow while preserving both row and column nucleotide frequencies. Is this possible? Can it be done efficiently? [EDIT]: By this I mean I want to produce a new matrix where each row has the same number of As, Cs, Gs and Ts as the corresponding row of the original matrix, and where each column has the same number of As, Cs, Gs and Ts as the corresponding column of the original matrix. Permuting the rows or columns of the original matrix will not achieve this in general. (E.g. for the example above, the top row has 2 Gs, and 1 each of A, C and T; if this row was swapped with row 2, the top row in the resulting matrix would have 3 As, 1 G and 1 T.) It's simple enough to preserve just column frequencies by shuffling a column at a time, and likewise for rows. But doing this will in general alter the frequencies of the other kind. My thoughts so far: If it's possible to pick 2 rows and 2 columns so that the 4 elements at the corners of this rectangle have the pattern XY YX for some pair of distinct elements X and Y, then replacing these 4 elements with YX XY will maintain both row and column frequencies. In the example at the top, this can be done for (at least) rows 1 and 2 and columns 2 and 5 (whose corners give the 2x2 matrix AG;GA), and for rows 1 and 3 and columns 1 and 4 (whose corners give GT;TG). Clearly this could be repeated a number of times to produce some level of randomisation. Generalising a bit, any "subrectangle" induced by a subset of rows and a subset of columns, in which the frequencies of all rows are the same and the frequencies of all columns are the same, can have both its rows and columns permuted to produce a valid complete rectangle. (Of these, only those subrectangles in which at least 1 element is changed are actually interesting.) Big questions: Are all valid complete matrices reachable by a series of such "subrectangle rearrangements"? I suspect the answer is yes. Are all valid subrectangle rearrangements decomposable into a series of 2x2 swaps? I suspect the answer is no, but I hope it's yes, since that would seem to make it easier to come up with an efficient algorithm. Can some or all of the valid rearrangements be computed efficiently? This question addresses a special case in which the set of possible elements is {0, 1}. The solutions people have come up with there are similar to what I have come up with myself, and are probably usable, but not ideal as they require an arbitrary amount of backtracking to work correctly. Also I'm concerned that only 2x2 swaps are considered. Finally, I would ideally like a solution that can be proven to select a matrix uniformly at random from the set of all matrices having identical row frequencies and column frequencies to the original. I know, I'm asking for a lot :)

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  • Two dimensional strings in C++

    - by dada
    I want to write something like 2d strings in C++. I tried with : vector< vector<string> > table; int m,n,i,j; string s; cin>>n>>m; for(i=0;i<n;i++) { for(j=0;j<m;j++) { cin>>s; table[i][j] = s; } } cout << "\n\n\n\n"; for(i=0;i<n;i++) { for(j=0;j<m;j++) { cout<<table[i][j]<<" "; } cout<<"\n"; } no compile errors, but when i enter input like: 10 20 .....#.............. .....#.............. .....#.............. .....#.............. ######.............. .......###.......... .......#.#.......... .......###...####### .............#.....# .............####### It gives me segmentation fault. Why ? What's wrong ? And how it should be done so it would work correctly ? Thank you.

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  • How can I use from ismember

    - by ahmad hosseini
    Assuming A=[32512199.30 5401000.29 347.33 32512199.69 5401000.45 347.39 32512199.67 5401001.32 353.58 32512199.96 5401001.50 346.99 32512196.71 5401001.69 346.62 ] and B=[32512199.30 5401000.29 347.33 32512199.69 5401000.45 347.39 32512199.67 5401001.32 347.00 32512198.85 5401000.91 347.25 32512196.71 5401001.69 346.87 ] I want using ismember extract the rows that have same X and Y and different Z. X is first column, Y is the second and Z is third. in A and B I want extract from A 32512199.67 5401001.32 353.58 and 32512196.71 5401001.69 346.62 OR from B 32512199.67 5401001.32 347.00 and 32512196.71 5401001.69 346.87 How can I do it?

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  • Help with calculation to steer ship in 3d space

    - by Aaron Anodide
    I'm a beginner using XNA to try and make a 3D Asteroids game. I'm really close to having my space ship drive around as if it had thrusters for pitch and yaw. The problem is I can't quite figure out how to translate the rotations, for instance, when I pitch forward 45 degrees and then start to turn - in this case there should be rotation being applied to all three directions to get the "diagonal yaw" - right? I thought I had it right with the calculations below, but they cause a partly pitched forward ship to wobble instead of turn.... :( Here's current (almost working) calculations for the Rotation acceleration: float accel = .75f; // Thrust +Y / Forward if (currentKeyboardState.IsKeyDown(Keys.I)) { this.ship.AccelerationY += (float)Math.Cos(this.ship.RotationZ) * accel; this.ship.AccelerationX += (float)Math.Sin(this.ship.RotationZ) * -accel; this.ship.AccelerationZ += (float)Math.Sin(this.ship.RotationX) * accel; } // Rotation +Z / Yaw if (currentKeyboardState.IsKeyDown(Keys.J)) { this.ship.RotationAccelerationZ += (float)Math.Cos(this.ship.RotationX) * accel; this.ship.RotationAccelerationY += (float)Math.Sin(this.ship.RotationX) * accel; this.ship.RotationAccelerationX += (float)Math.Sin(this.ship.RotationY) * accel; } // Rotation -Z / Yaw if (currentKeyboardState.IsKeyDown(Keys.K)) { this.ship.RotationAccelerationZ += (float)Math.Cos(this.ship.RotationX) * -accel; this.ship.RotationAccelerationY += (float)Math.Sin(this.ship.RotationX) * -accel; this.ship.RotationAccelerationX += (float)Math.Sin(this.ship.RotationY) * -accel; } // Rotation +X / Pitch if (currentKeyboardState.IsKeyDown(Keys.F)) { this.ship.RotationAccelerationX += accel; } // Rotation -X / Pitch if (currentKeyboardState.IsKeyDown(Keys.D)) { this.ship.RotationAccelerationX -= accel; } I'm combining that with drawing code that does a rotation to the model: public void Draw(Matrix world, Matrix view, Matrix projection, TimeSpan elsapsedTime) { float seconds = (float)elsapsedTime.TotalSeconds; // update velocity based on acceleration this.VelocityX += this.AccelerationX * seconds; this.VelocityY += this.AccelerationY * seconds; this.VelocityZ += this.AccelerationZ * seconds; // update position based on velocity this.PositionX += this.VelocityX * seconds; this.PositionY += this.VelocityY * seconds; this.PositionZ += this.VelocityZ * seconds; // update rotational velocity based on rotational acceleration this.RotationVelocityX += this.RotationAccelerationX * seconds; this.RotationVelocityY += this.RotationAccelerationY * seconds; this.RotationVelocityZ += this.RotationAccelerationZ * seconds; // update rotation based on rotational velocity this.RotationX += this.RotationVelocityX * seconds; this.RotationY += this.RotationVelocityY * seconds; this.RotationZ += this.RotationVelocityZ * seconds; Matrix translation = Matrix.CreateTranslation(PositionX, PositionY, PositionZ); Matrix rotation = Matrix.CreateRotationX(RotationX) * Matrix.CreateRotationY(RotationY) * Matrix.CreateRotationZ(RotationZ); model.Root.Transform = rotation * translation * world; model.CopyAbsoluteBoneTransformsTo(boneTransforms); foreach (ModelMesh mesh in model.Meshes) { foreach (BasicEffect effect in mesh.Effects) { effect.World = boneTransforms[mesh.ParentBone.Index]; effect.View = view; effect.Projection = projection; effect.EnableDefaultLighting(); } mesh.Draw(); } }

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  • Servlet stops without giving any exception

    - by Fahim
    Hi, I have implemented a Servlet hosted on Tomcat 6 server on Mandriva Linux. I have been able to make the client communicate with the Servlet. In response to a request the Servlet tries to instantiate a another class (named KalmanFilter) located in the same directory. The KalmanFilter tries to create four Matrices (using Jama Matrix package). But at this point Servlet stops without giving any exception ! However, from another test code in the same directory I have been able to create instance of KalmanFilter class, and proceed without any error. The problem occurs only when my Servlet tries to instantiate the KalmanFilter class and create the matrices. Any idea? Below are the codes: MyServlet.java import javax.servlet.*; import javax.servlet.http.*; import java.io.*; import java.util.*; public class MyServlet extends HttpServlet { public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException{ doGet(request, response); } public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException{ PrintWriter out = null; //response.getWriter(); try{ System.out.println("creating new KalmanFilter"); KalmanFilter filter = new KalmanFilter(); out = response.getWriter(); out.print("filter created"); }catch(Exception ex){ ex.printStackTrace(); System.out.println("Exception in doGet(): " + ex.getMessage()); ex.printStackTrace(out); } } } KalmanFilter.java import Jama.Matrix; public class KalmanFilter { protected Matrix X, X0; protected Matrix F, Q; //protected Matrix F, B, U, Q; protected Matrix H, R; protected Matrix P, P0; private final double EPSILON = 0.001; public KalmanFilter(){ System.out.println("from constructor of KalmanFilter"); createInitialMatrices(); } private void createInitialMatrices(){ System.out.println("from KalmanFilter.createInitialMatrices()"); double[][] pVals = { {1.0, 0.0}, {0.0, 1.0} }; double[][] qVals = { {EPSILON, EPSILON}, {EPSILON, EPSILON} }; double[][] hVals = { {1.0, 0.0}, {0.0, 1.0}, {1.0, 0.0}, {0.0, 1.0} }; double[][] xVals = { {0.0}, {0.0}, }; System.out.println("creating P Q H X matrices in createInitialMatrices()"); try{ this.P = new Matrix(pVals); System.out.println("created P matrix in createInitialMatrices()"); this.Q = new Matrix(qVals); System.out.println("created Q matrix in createInitialMatrices()"); this.H = new Matrix(hVals); System.out.println("created H matrix in createInitialMatrices()"); this.X = new Matrix(xVals); System.out.println("created X matrix in createInitialMatrices()"); System.out.println("created P Q H X matrices in createInitialMatrices()"); }catch(Exception e){ System.out.println("Exception from createInitialMatrices()"+ e.getMessage()); e.printStackTrace(); } System.out.println("returning from createInitialMatrices()"); } }

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  • Incremental PCA

    - by smichak
    Hi, Lately, I've been looking into an implementation of an incremental PCA algorithm in python - I couldn't find something that would meet my needs so I did some reading and implemented an algorithm I found in some paper. Here is the module's code - the relevant paper on which it is based is mentioned in the module's documentation. I would appreciate any feedback from people who are interested in this. Micha #!/usr/bin/env python """ Incremental PCA calculation module. Based on P.Hall, D. Marshall and R. Martin "Incremental Eigenalysis for Classification" which appeared in British Machine Vision Conference, volume 1, pages 286-295, September 1998. Principal components are updated sequentially as new observations are introduced. Each new observation (x) is projected on the eigenspace spanned by the current principal components (U) and the residual vector (r = x - U(U.T*x)) is used as a new principal component (U' = [U r]). The new principal components are then rotated by a rotation matrix (R) whose columns are the eigenvectors of the transformed covariance matrix (D=U'.T*C*U) to yield p + 1 principal components. From those, only the first p are selected. """ __author__ = "Micha Kalfon" import numpy as np _ZERO_THRESHOLD = 1e-9 # Everything below this is zero class IPCA(object): """Incremental PCA calculation object. General Parameters: m - Number of variables per observation n - Number of observations p - Dimension to which the data should be reduced """ def __init__(self, m, p): """Creates an incremental PCA object for m-dimensional observations in order to reduce them to a p-dimensional subspace. @param m: Number of variables per observation. @param p: Number of principle components. @return: An IPCA object. """ self._m = float(m) self._n = 0.0 self._p = float(p) self._mean = np.matrix(np.zeros((m , 1), dtype=np.float64)) self._covariance = np.matrix(np.zeros((m, m), dtype=np.float64)) self._eigenvectors = np.matrix(np.zeros((m, p), dtype=np.float64)) self._eigenvalues = np.matrix(np.zeros((1, p), dtype=np.float64)) def update(self, x): """Updates with a new observation vector x. @param x: Next observation as a column vector (m x 1). """ m = self._m n = self._n p = self._p mean = self._mean C = self._covariance U = self._eigenvectors E = self._eigenvalues if type(x) is not np.matrix or x.shape != (m, 1): raise TypeError('Input is not a matrix (%d, 1)' % int(m)) # Update covariance matrix and mean vector and centralize input around # new mean oldmean = mean mean = (n*mean + x) / (n + 1.0) C = (n*C + x*x.T + n*oldmean*oldmean.T - (n+1)*mean*mean.T) / (n + 1.0) x -= mean # Project new input on current p-dimensional subspace and calculate # the normalized residual vector g = U.T*x r = x - (U*g) r = (r / np.linalg.norm(r)) if not _is_zero(r) else np.zeros_like(r) # Extend the transformation matrix with the residual vector and find # the rotation matrix by solving the eigenproblem DR=RE U = np.concatenate((U, r), 1) D = U.T*C*U (E, R) = np.linalg.eigh(D) # Sort eigenvalues and eigenvectors from largest to smallest to get the # rotation matrix R sorter = list(reversed(E.argsort(0))) E = E[sorter] R = R[:,sorter] # Apply the rotation matrix U = U*R # Select only p largest eigenvectors and values and update state self._n += 1.0 self._mean = mean self._covariance = C self._eigenvectors = U[:, 0:p] self._eigenvalues = E[0:p] @property def components(self): """Returns a matrix with the current principal components as columns. """ return self._eigenvectors @property def variances(self): """Returns a list with the appropriate variance along each principal component. """ return self._eigenvalues def _is_zero(x): """Return a boolean indicating whether the given vector is a zero vector up to a threshold. """ return np.fabs(x).min() < _ZERO_THRESHOLD if __name__ == '__main__': import sys def pca_svd(X): X = X - X.mean(0).repeat(X.shape[0], 0) [_, _, V] = np.linalg.svd(X) return V N = 1000 obs = np.matrix([np.random.normal(size=10) for _ in xrange(N)]) V = pca_svd(obs) print V[0:2] pca = IPCA(obs.shape[1], 2) for i in xrange(obs.shape[0]): x = obs[i,:].transpose() pca.update(x) U = pca.components print U

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  • Quaternion Camera Orbiting around a Sphere

    - by jessejuicer
    Background: I'm trying to create a game where the camera is always rotating around a single sphere. I'm using the DirectX D3DX math functions in C++ on Windows. The Problem: I cannot get both the camera position and orientation both working properly at the same time. Either one works but not both together. Here's the code for my quaternion camera that revolves around a sphere, always looking at the centerpoint of the sphere, ... as far as I understand it (but which isn't working properly): (I'm only going to present rotation around the X axis here, to simplify this post) Whenever the UP key is pressed or held down, the camera should rotate around the X axis, while looking at the centerpoint of the sphere (which is at 0,0,0 in the world). So, I build a quaternion that represents a small angle of rotation around the x axis like this (where 'deltaAngle' is a small enough number for a slow rotation): D3DXVECTOR3 rotAxis; D3DXQUATERNION tempQuat; tempQuat.x = 0.0f; tempQuat.y = 0.0f; tempQuat.z = 0.0f; tempQuat.w = 1.0f; rotAxis.x = 1.0f; rotAxis.y = 0.0f; rotAxis.z = 0.0f; D3DXQuaternionRotationAxis(&tempQuat, &rotAxis, deltaAngle); ...and I accumulate the result into the camera's current orientation quat, like this: D3DXQuaternionMultiply(&cameraOrientationQuat, &cameraOrientationQuat, &tempQuat); ...which all works fine. Now I need to build a view matrix to pass to DirectX SetTransform function. So I build a rotation matrix from the camera orientation quat as follows: D3DXMATRIXA16 rotationMatrix; D3DXMatrixIdentity(&rotationMatrix); D3DXMatrixRotationQuaternion(&rotationMatrix, &cameraOrientationQuat); ...Now (as seen below) if I just transpose that rotationMatrix and plug it into the 3x3 section of the view matrix, then negate the camera's position and plug it into the translation section of the view matrix, the rotation magically works. Perfectly. (even when I add in rotations for all three axes). There's no gimbal lock, just a smooth rotation all around in any direction. BUT- this works even though I never change the camera's position. At all. Which sorta blows my mind. I even display the camera position and can watch it stay constant at it's starting point (0.0, 0.0, -4000.0). It never moves, but the rotation around the sphere is perfect. I don't understand that. For proper view rotation, the camera position should be revolving around the sphere. Here's the rest of building the view matrix (I'll talk about the commented code below). Note that the camera starts out at (0.0, 0.0, -4000.0) and m_camDistToTarget is 4000.0: /* D3DXVECTOR3 vec1; D3DXVECTOR4 vec2; vec1.x = 0.0f; vec1.y = 0.0f; vec1.z = -1.0f; D3DXVec3Transform(&vec2, &vec1, &rotationMatrix); g_cameraActor->pos.x = vec2.x * g_cameraActor->m_camDistToTarget; g_cameraActor->pos.y = vec2.y * g_cameraActor->m_camDistToTarget; g_cameraActor->pos.z = vec2.z * g_cameraActor->m_camDistToTarget; */ D3DXMatrixTranspose(&g_viewMatrix, &rotationMatrix); g_viewMatrix._41 = -g_cameraActor->pos.x; g_viewMatrix._42 = -g_cameraActor->pos.y; g_viewMatrix._43 = -g_cameraActor->pos.z; g_viewMatrix._44 = 1.0f; g_direct3DDevice9->SetTransform( D3DTS_VIEW, &g_viewMatrix ); ...(The world matrix is always an identity, and the perspective projection works fine). ...So, without the commented code being compiled, the rotation works fine. But to be proper, for obvious reasons, the camera position should be rotating around the sphere, which it currently is not. That's what the commented code is supposed to do. And when I add in that chunk of code to do that, and look at all the data as I hold the keys down (using UP, DOWN, LEFT, RIGHT to rotate different directions) all the values look correct! The camera position is rotating around the sphere just fine, and I can watch that happen visually too. The problem is that the camera orientation does not lookat the center of the sphere. It always looks straight forward down the z axis (toward positive z) as it revolves around the sphere. Yet the values of both the rotation matrix and the view matrix seem to be behaving correctly. (The view matrix orientation is the same as the rotation matrix, just transposed). For instance if I just hold down the key to spin around the x axis, I can watch the values of the three axes represented in the view matrix (x, y, and z axes)... view x-axis stays at (1.0, 0.0, 0.0), and view y-axis and z-axis both spin around the x axis just fine. All the numbers are changing as they should be... well, almost. As far as I can tell, the position of the view matrix is spinning around the sphere one direction (like clockwise), and the orientation (the axes in the view matrix) are spinning the opposite direction (like counter-clockwise). Which I guess explains why the orientation appears to stay straight ahead. I know the position is correct. It revolves properly. It's the orientation that's wrong. Can anyone see what am I doing wrong? Am I using these functions incorrectly? Or is my algorithm flawed? As usual I've been combing my code for simple mistakes for many hours. I'm willing to post the actual code, and a video of the behavior, but that will take much more effort. Thought I'd ask this way first.

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  • Why wont numpy matrix let me print its rows?

    - by uberjumper
    Okay this is probably a really dumb question, however its really starting to hurt. I have a numpy matrix, and basically i print it out row by row. However i want to make each row be formatted and separated properly. >>> arr = numpy.matrix([[x for x in range(5)] for y in range(5)]) >>> arr matrix([[0, 1, 2, 3, 4], [0, 1, 2, 3, 4], [0, 1, 2, 3, 4], [0, 1, 2, 3, 4], [0, 1, 2, 3, 4]]) Lets say i want to print the first row, and add a '|' between each element: >>> '|'.join(map(str, arr[0,])) '[[0 1 2 3 4]]' Err... >>> '|'.join(map(lambda x: str(x[0]), arr[0])) '[[0 1 2 3 4]]' I am really confused by this behavior why does it do this?

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  • How i store the images pixels in matrix form?

    - by Rajendra Bhole
    Hi, I developing an application in which the pixelize image i want to be store in matrix format. The code is as follows. struct pixel { //unsigned char r, g, b,a; Byte r, g, b; int count; }; (NSInteger) processImage1: (UIImage*) image { // Allocate a buffer big enough to hold all the pixels struct pixel* pixels = (struct pixel*) calloc(1, image.size.width * image.size.height * sizeof(struct pixel)); if (pixels != nil) { // Create a new bitmap CGContextRef context = CGBitmapContextCreate( (void*) pixels, image.size.width, image.size.height, 8, image.size.width * 4, CGImageGetColorSpace(image.CGImage), kCGImageAlphaPremultipliedLast ); NSLog(@"1=%d, 2=%d, 3=%d", CGImageGetBitsPerComponent(image), CGImageGetBitsPerPixel(image),CGImageGetBytesPerRow(image)); if (context != NULL) { // Draw the image in the bitmap CGContextDrawImage(context, CGRectMake(0.0f, 0.0f, image.size.width, image.size.height), image.CGImage); NSUInteger numberOfPixels = image.size.width * image.size.height; I confusing about how to initialize the 2-D matrix in which the matrix store data of pixels.

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  • 3d Model Scaling With Camera

    - by spasarto
    I have a very simple 3D maze program that uses a first person camera to navigate the maze. I'm trying to scale the blocks that make up the maze walls and floor so the corridors seem more roomy to the camera. Every time I scale the model, the camera seems to scale with it, and the corridors always stay the same width. I've tried apply the scale to the model in the content pipe (setting the scale property of the model in the properties window in VS). I've also tried to apply the scale using Matrix.CreateScale(float) using the Scale-Rotate-Transform order with the same result. If I leave the camera speed the same, the camera moves slower, so I know it's traversing a larger distance, but the world doesn't look larger; the camera just seems slower. I'm not sure what part of the code to include since I don't know if it is an issue with my model, camera, or something else. Any hints at what I'm doing wrong? Camera: Projection = Matrix.CreatePerspectiveFieldOfView( MathHelper.PiOver4, _device.Viewport.AspectRatio, 1.0f, 1000.0f ); Matrix camRotMatrix = Matrix.CreateRotationX( _cameraPitch ) * Matrix.CreateRotationY( _cameraYaw ); Vector3 transCamRef = Vector3.Transform( _cameraForward, camRotMatrix ); _cameraTarget = transCamRef + CameraPosition; Vector3 camRotUpVector = Vector3.Transform( _cameraUpVector, camRotMatrix ); View = Matrix.CreateLookAt( CameraPosition, _cameraTarget, camRotUpVector ); Model: World = Matrix.CreateTranslation( Position );

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  • Converting a DrawModel() using BasicEffect to one using Effect

    - by Fibericon
    Take this DrawModel() provided by MSDN: private void DrawModel(Model m) { Matrix[] transforms = new Matrix[m.Bones.Count]; float aspectRatio = graphics.GraphicsDevice.Viewport.Width / graphics.GraphicsDevice.Viewport.Height; m.CopyAbsoluteBoneTransformsTo(transforms); Matrix projection = Matrix.CreatePerspectiveFieldOfView(MathHelper.ToRadians(45.0f), aspectRatio, 1.0f, 10000.0f); Matrix view = Matrix.CreateLookAt(new Vector3(0.0f, 50.0f, Zoom), Vector3.Zero, Vector3.Up); foreach (ModelMesh mesh in m.Meshes) { foreach (BasicEffect effect in mesh.Effects) { effect.EnableDefaultLighting(); effect.View = view; effect.Projection = projection; effect.World = gameWorldRotation * transforms[mesh.ParentBone.Index] * Matrix.CreateTranslation(Position); } mesh.Draw(); } } How would I apply a custom effect to a model with that? Effect doesn't have View, Projection, or World members. This is what they recommend replacing the foreach loop with: foreach (ModelMesh mesh in terrain.Meshes) { foreach (Effect effect in mesh.Effects) { mesh.Draw(); } } Of course, that doesn't really work. What else needs to be done?

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  • HTML5 Canvas Converting between cartesian and isometric coordinates

    - by Amir
    I'm having issues wrapping my head around the Cartesian to Isometric coordinate conversion in HTML5 canvas. As I understand it, the process is two fold: (1) Scale down the y-axis by 0.5, i.e. ctx.scale(1,0.5); or ctx.setTransform(1,0,0,0.5,0,0); This supposedly produces the following matrix: [x; y] x [1, 0; 0, 0.5] (2) Rotate the context by 45 degrees, i.e. ctx.rotate(Math.PI/4); This should produce the following matrix: [x; y] x [cos(45), -sin(45); sin(45), cos(45)] This (somehow) results in the final matrix of ctx.setTransform(2,-1,1,0.5,0,0); which I cannot seem to understand... How is this matrix derived? I cannot seem to produce this matrix by multiplying the scaling and rotation matrices produced earlier... Also, if I write out the equation for the final transformation matrix, I get: newX = 2x + y newY = -x + y/2 But this doesn't seem to be correct. For example, the following code draws an isometric tile at cartesian coordinates (500, 100). ctx.setTransform(2,-1,1,0.5,0,0); ctx.fillRect(500, 100, width*2, height); When I check the result on the screen, the actual coordinates are (285, 215) which do not satisfy the equations I produced earlier... So what is going on here? I would be very grateful if you could: (1) Help me understand how the final isometric transformation matrix is derived; (2) Help me produce the correct equation for finding the on-screen coordinates of an isometric projection. Many thanks and kind regards

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  • XNA- Transforming children

    - by user1806687
    So, I have a Model stored in MyModel, that is made from three meshes. If you loop thrue MyModel.Meshes the first two are children of the third one. And was just wondering, if anyone could tell me where is the problem with my code. This method is called whenever I want to programmaticly change the position of a whole model: public void ChangePosition(Vector3 newPos) { Position = newPos; MyModel.Root.Transform = Matrix.CreateScale(VectorMathHelper.VectorMath(CurrentSize, DefaultSize, '/')) * Matrix.CreateFromAxisAngle(MyModel.Root.Transform.Up, MathHelper.ToRadians(Rotation.Y)) * Matrix.CreateFromAxisAngle(MyModel.Root.Transform.Right, MathHelper.ToRadians(Rotation.X)) * Matrix.CreateFromAxisAngle(MyModel.Root.Transform.Forward, MathHelper.ToRadians(Rotation.Z)) * Matrix.CreateTranslation(Position); Matrix[] transforms = new Matrix[MyModel.Bones.Count]; MyModel.CopyAbsoluteBoneTransformsTo(transforms); int count = transforms.Length - 1; foreach (ModelMesh mesh in MyModel.Meshes) { mesh.ParentBone.Transform = transforms[count]; count--; } } This is the draw method: foreach (ModelMesh mesh in MyModel.Meshes) { foreach (BasicEffect effect in mesh.Effects) { effect.View = camera.view; effect.Projection = camera.projection; effect.World = mesh.ParentBone.Transform; effect.EnableDefaultLighting(); } mesh.Draw(); } The thing is when I call ChangePosition() the first time everything works perfectlly, but as soon as I call it again and again. The first two meshes(children meshes) start to move away from the parent mesh. Another thing I wanted to ask, if I change the scale/rotation/position of a children mesh, and then do CopyAbsoluteBoneTransforms() will children meshes be positioned properlly(at the proper distance) or would achieving that require more math/methods? Thanks in advance

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  • cvWarpPerspective, having transformation matrix, how to extract the quad points?

    - by Stevecao
    I have the 3x3 transformation matrix that goes through the cvWarpPerspective, I would like to extract the four corner coordinates value. CvMat* M; M = xxxxxxxxxxx ;// Matrix was generated by a certain process cvWarpPerspective( img, transformed, M, CV_INTER_LINEAR + CV_WARP_FILL_OUTLIERS, cvScalarAll( 0 ) ); // this creates a complete black new image transformed, from this image i would like to know the 4 corner coordinates

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  • How to use an adjacency matrix to determine which rows to 'pass' to a function in r?

    - by dubhousing
    New to R, and I have a long-ish question: I have a shapefile/map, and I'm aiming to calculate a certain index for every polygon in that map, based on attributes of that polygon and each polygon that neighbors it. I have an adjacency matrix -- which I think is the same as a "1st-order queen contiguity weights matrix", although I'm not sure -- that describes which polygons border which other polygons, e.g., POLYID A B C D E A 0 0 1 0 1 B 0 0 1 0 0 C 1 1 0 1 0 D 0 0 1 0 1 E 1 0 0 1 0 The above indicates, for instance, that polygons 'C' and 'E' adjoin polygon 'A'; polygon 'B' adjoins only polygon 'C', etc. The attribute table I have has one polygon per row: POLYID TOT L10K 10_15K 15_20K ... A 500 24 30 77 ... Where TOT, L10K, etc. are the variables I use to calculate an index. There are 525 polygons/rows in my data, so I'd like to use the adjacency matrix to determine which rows' attributes to incorporate into the calculation of the index of interest. For now, I can calculate the index when I subset the rows that correspond to one 'bundle' of neighboring polygons, and then use a loop (if it's of interest, I'm calculating the Centile Gap Index, a measure of local income segregation). E.g., subsetting the 'neighborhood' of the Detroit City Schools: Detroit <- UNSD00[c(142,150,164,221,226,236,295,327,157,177,178,364,233,373,418,424,449,451,487),] Then record the marginal column proportions and a running total: catprops <- vector() for(i in 4:19) { catprops[(i-3)]<-sum(Detroit[,i])/sum(Detroit[,3]) } catprops <- as.data.frame(catprops) catprops[,2]<-cumsum(catprops[,1]) Columns 4:19 are the necessary ones in the attribute table. Then I use the following code to calculate the index -- note that the loop has "i in 1:19" because the Detroit subset has 19 polygons. cgidistsum <- 0 for(i in 1:19) { pranks <- vector() for(j in 4:19) { if (Detroit[i,j]==0) pranks <- append(pranks,0) else if (j == 4) pranks <- append(pranks,seq(0,catprops[1,2],by=catprops[1,2]/Detroit[i,j])) else pranks <- append(pranks,seq(catprops[j-4,2],catprops[j-3,2],by=catprops[j-3,1]/Detroit[i,j])) } distpranks <- vector() distpranks<-abs(pranks-median(pranks)) cgidistsum <- cgidistsum + sum(distpranks) } cgi <- (.25-(cgidistsum/sum(Detroit[,3])))/.25 My apologies if I've provided more information than is necessary. I would really like to exploit the adjacency matrix in order to calculate the CGI for each 'bundle' of these rows. If you happen to know how I could started with this, that would be great. and my apologies for any novice mistakes, I'm new to R!

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  • How do I calculate the boundary of the game window after transforming the view?

    - by Cypher
    My Camera class handles zoom, rotation, and of course panning. It's invoked through SpriteBatch.Begin, like so many other XNA 2D camera classes. It calculates the view Matrix like so: public Matrix GetViewMatrix() { return Matrix.Identity * Matrix.CreateTranslation(new Vector3(-this.Spatial.Position, 0.0f)) * Matrix.CreateTranslation(-( this.viewport.Width / 2 ), -( this.viewport.Height / 2 ), 0.0f) * Matrix.CreateRotationZ(this.Rotation) * Matrix.CreateScale(this.Scale, this.Scale, 1.0f) * Matrix.CreateTranslation(this.viewport.Width * 0.5f, this.viewport.Height * 0.5f, 0.0f); } I was having a minor issue with performance, which after doing some profiling, led me to apply a culling feature to my rendering system. It used to, before I implemented the camera's zoom feature, simply grab the camera's boundaries and cull any game objects that did not intersect with the camera. However, after giving the camera the ability to zoom, that no longer works. The reason why is visible in the screenshot below. The navy blue rectangle represents the camera's boundaries when zoomed out all the way (Camera.Scale = 0.5f). So, when zoomed out, game objects are culled before they reach the boundaries of the window. The camera's width and height are determined by the Viewport properties of the same name (maybe this is my mistake? I wasn't expecting the camera to "resize" like this). What I'm trying to calculate is a Rectangle that defines the boundaries of the screen, as indicated by my awesome blue arrows, even after the camera is rotated, scaled, or panned. Here is how I've more recently found out how not to do it: public Rectangle CullingRegion { get { Rectangle region = Rectangle.Empty; Vector2 size = this.Spatial.Size; size *= 1 / this.Scale; Vector2 position = this.Spatial.Position; position = Vector2.Transform(position, this.Inverse); region.X = (int)position.X; region.Y = (int)position.Y; region.Width = (int)size.X; region.Height = (int)size.Y; return region; } } It seems to calculate the right size, but when I render this region, it moves around which will obviously cause problems. It needs to be "static", so to speak. It's also obscenely slow, which causes more of a problem than it solves. What am I missing?

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