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• How to skip index in for loop in Python?

  - by System Matrix

  How to achieve following in Python? C code: for(i=0;i<5;i++) { if( i == 2 ) { i++; } } Basically skipping index?

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• How can I change the tick marks scale in MATLAB?

  - by Wires

  Hey, I have a matrix A which I am plotting using imagesc(A). The matrix is a 512 X 512 matrix, but I need the axes to be labeled from 0 to 4000 instead of 0 to 512. I can't seem to find where I can change this instead of just changing from where to where the points are plotted!

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• OpenGL multiple threads, variable handling [closed]

  - by toeplitz

  I have written an OpenGL program which runs in the following way: Main: - Initialize SDL - Create thread which has the OpenGL context: - Renderloop - Set camera (view) matrix with glUniform. - glDrawElements() .... etc. - Swapbuffers(); - Main SDL loop handling input events and such. - Update camera matrix of type glm::mat4. This is how I pass my camera object to the class that handles opengl. Camera *cam = new Camera(); gl.setCam(cam); where void setCam(Camera *camera) { this->camera = camera; } For rendering in the opengl context thread, this happens: glm::mat4 modelView = camera->view * model; glUniformMatrix4fv(shader->bindUniform("modelView"), 1, GL_FALSE, glm::value_ptr(modelView)); In the main program where my SDL and other things are handles I then recompute the view matrix. This his working fine without me using any mutex locks. Is this correct? On the other hand, I add objects to my scene by an "upload queue" and in this case I have to mutex lock my upload queue vector (vector class type) when adding items to it or else the program crashes. In summary: I recompute my matrix in a different thread and then use it in the opengl thread without any mutex lock. Why is this working? Edit: I think my question is similar to what was asked here: Should I lock a variable in one thread if I only need it's value in other threads, and why does it work if I don't?, only in my case it is even more simple with only one matrix being changed.

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• How to split up input from System.in

  - by zzaw

  Alright so I'm working on something where I take input from System.in; the first line is an int (n) representing the size of a matrix. The next n lines are the matrix itself like so: 10 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 1 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 1 0 1 0 0 0 0 0 0 0 0 1 0 0 1 1 0 0 1 0 0 0 0 0 1 0 0 0 0 0 0 0 1 1 0 0 0 1 1 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 The problem is there may be multiple matrix's in a single input, so the next line would have another int and the corresponding matrix underneath until it hits a line with a single 0. I then have to pass each matrix along with the size at the top as a BufferedReader to a method which adds the numbers to a 2D array. I'm just a little unsure on how to split the input up and send it to the method. Would making a new BufferedReader using skip() and specifying a size each time work? The biggest problem I seem to be running into is reading the size but then the size being excluded as it has already been read. Cheers

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• C# Neural Networks with Encog

  - by JoshReuben

  Neural Networks ·       I recently read a book Introduction to Neural Networks for C# , by Jeff Heaton. http://www.amazon.com/Introduction-Neural-Networks-C-2nd/dp/1604390093/ref=sr_1_2?ie=UTF8&s=books&qid=1296821004&sr=8-2-spell. Not the 1st ANN book I've perused, but a nice revision.   ·       Artificial Neural Networks (ANNs) are a mechanism of machine learning – see http://en.wikipedia.org/wiki/Artificial_neural_network , http://en.wikipedia.org/wiki/Category:Machine_learning ·       Problems Not Suited to a Neural Network Solution- Programs that are easily written out as flowcharts consisting of well-defined steps, program logic that is unlikely to change, problems in which you must know exactly how the solution was derived. ·       Problems Suited to a Neural Network – pattern recognition, classification, series prediction, and data mining. Pattern recognition - network attempts to determine if the input data matches a pattern that it has been trained to recognize. Classification - take input samples and classify them into fuzzy groups. ·       As far as machine learning approaches go, I thing SVMs are superior (see http://en.wikipedia.org/wiki/Support_vector_machine ) - a neural network has certain disadvantages in comparison: an ANN can be overtrained, different training sets can produce non-deterministic weights and it is not possible to discern the underlying decision function of an ANN from its weight matrix – they are black box. ·       In this post, I'm not going to go into internals (believe me I know them). An autoassociative network (e.g. a Hopfield network) will echo back a pattern if it is recognized. ·       Under the hood, there is very little maths. In a nutshell - Some simple matrix operations occur during training: the input array is processed (normalized into bipolar values of 1, -1) - transposed from input column vector into a row vector, these are subject to matrix multiplication and then subtraction of the identity matrix to get a contribution matrix. The dot product is taken against the weight matrix to yield a boolean match result. For backpropogation training, a derivative function is required. In learning, hill climbing mechanisms such as Genetic Algorithms and Simulated Annealing are used to escape local minima. For unsupervised training, such as found in Self Organizing Maps used for OCR, Hebbs rule is applied. ·       The purpose of this post is not to mire you in technical and conceptual details, but to show you how to leverage neural networks via an abstraction API - Encog   Encog ·       Encog is a neural network API ·       Links to Encog: http://www.encog.org , http://www.heatonresearch.com/encog, http://www.heatonresearch.com/forum ·       Encog requires .Net 3.5 or higher – there is also a Silverlight version. Third-Party Libraries – log4net and nunit. ·       Encog supports feedforward, recurrent, self-organizing maps, radial basis function and Hopfield neural networks. ·       Encog neural networks, and related data, can be stored in .EG XML files. ·       Encog Workbench allows you to edit, train and visualize neural networks. The Encog Workbench can generate code. Synapses and layers ·       the primary building blocks - Almost every neural network will have, at a minimum, an input and output layer. In some cases, the same layer will function as both input and output layer. ·       To adapt a problem to a neural network, you must determine how to feed the problem into the input layer of a neural network, and receive the solution through the output layer of a neural network. ·       The Input Layer - For each input neuron, one double value is stored. An array is passed as input to a layer. Encog uses the interface INeuralData to hold these arrays. The class BasicNeuralData implements the INeuralData interface. Once the neural network processes the input, an INeuralData based class will be returned from the neural network's output layer. ·       convert a double array into an INeuralData object : INeuralData data = new BasicNeuralData(= new double[10]); ·       the Output Layer- The neural network outputs an array of doubles, wraped in a class based on the INeuralData interface. ·        The real power of a neural network comes from its pattern recognition capabilities. The neural network should be able to produce the desired output even if the input has been slightly distorted. ·       Hidden Layers– optional. between the input and output layers. very much a “black box”. If the structure of the hidden layer is too simple it may not learn the problem. If the structure is too complex, it will learn the problem but will be very slow to train and execute. Some neural networks have no hidden layers. The input layer may be directly connected to the output layer. Further, some neural networks have only a single layer. A single layer neural network has the single layer self-connected. ·       connections, called synapses, contain individual weight matrixes. These values are changed as the neural network learns. Constructing a Neural Network ·       the XOR operator is a frequent “first example” -the “Hello World” application for neural networks. ·       The XOR Operator- only returns true when both inputs differ. 0 XOR 0 = 0 1 XOR 0 = 1 0 XOR 1 = 1 1 XOR 1 = 0 ·       Structuring a Neural Network for XOR  - two inputs to the XOR operator and one output. ·       input: 0.0,0.0 1.0,0.0 0.0,1.0 1.0,1.0 ·       Expected output: 0.0 1.0 1.0 0.0 ·       A Perceptron - a simple feedforward neural network to learn the XOR operator. ·       Because the XOR operator has two inputs and one output, the neural network will follow suit. Additionally, the neural network will have a single hidden layer, with two neurons to help process the data. The choice for 2 neurons in the hidden layer is arbitrary, and often comes down to trial and error. ·       Neuron Diagram for the XOR Network ·       ·       The Encog workbench displays neural networks on a layer-by-layer basis. ·       Encog Layer Diagram for the XOR Network:   ·       Create a BasicNetwork - Three layers are added to this network. the FinalizeStructure method must be called to inform the network that no more layers are to be added. The call to Reset randomizes the weights in the connections between these layers. var network = new BasicNetwork(); network.AddLayer(new BasicLayer(2)); network.AddLayer(new BasicLayer(2)); network.AddLayer(new BasicLayer(1)); network.Structure.FinalizeStructure(); network.Reset(); ·       Neural networks frequently start with a random weight matrix. This provides a starting point for the training methods. These random values will be tested and refined into an acceptable solution. However, sometimes the initial random values are too far off. Sometimes it may be necessary to reset the weights again, if training is ineffective. These weights make up the long-term memory of the neural network. Additionally, some layers have threshold values that also contribute to the long-term memory of the neural network. Some neural networks also contain context layers, which give the neural network a short-term memory as well. The neural network learns by modifying these weight and threshold values. ·       Now that the neural network has been created, it must be trained. Training a Neural Network ·       construct a INeuralDataSet object - contains the input array and the expected output array (of corresponding range). Even though there is only one output value, we must still use a two-dimensional array to represent the output. public static double[][] XOR_INPUT ={ new double[2] { 0.0, 0.0 }, new double[2] { 1.0, 0.0 }, new double[2] { 0.0, 1.0 }, new double[2] { 1.0, 1.0 } };   public static double[][] XOR_IDEAL = { new double[1] { 0.0 }, new double[1] { 1.0 }, new double[1] { 1.0 }, new double[1] { 0.0 } };   INeuralDataSet trainingSet = new BasicNeuralDataSet(XOR_INPUT, XOR_IDEAL); ·       Training is the process where the neural network's weights are adjusted to better produce the expected output. Training will continue for many iterations, until the error rate of the network is below an acceptable level. Encog supports many different types of training. Resilient Propagation (RPROP) - general-purpose training algorithm. All training classes implement the ITrain interface. The RPROP algorithm is implemented by the ResilientPropagation class. Training the neural network involves calling the Iteration method on the ITrain class until the error is below a specific value. The code loops through as many iterations, or epochs, as it takes to get the error rate for the neural network to be below 1%. Once the neural network has been trained, it is ready for use. ITrain train = new ResilientPropagation(network, trainingSet);   for (int epoch=0; epoch < 10000; epoch++) { train.Iteration(); Debug.Print("Epoch #" + epoch + " Error:" + train.Error); if (train.Error > 0.01) break; } Executing a Neural Network ·       Call the Compute method on the BasicNetwork class. Console.WriteLine("Neural Network Results:"); foreach (INeuralDataPair pair in trainingSet) { INeuralData output = network.Compute(pair.Input); Console.WriteLine(pair.Input[0] + "," + pair.Input[1] + ", actual=" + output[0] + ",ideal=" + pair.Ideal[0]); } ·       The Compute method accepts an INeuralData class and also returns a INeuralData object. Neural Network Results: 0.0,0.0, actual=0.002782538818034049,ideal=0.0 1.0,0.0, actual=0.9903741937121177,ideal=1.0 0.0,1.0, actual=0.9836807956566187,ideal=1.0 1.0,1.0, actual=0.0011646072586172778,ideal=0.0 ·       the network has not been trained to give the exact results. This is normal. Because the network was trained to 1% error, each of the results will also be within generally 1% of the expected value.

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• How to make a player stay within bounds of world with 2D Camera

  - by Craig

  Im creating a simple top down survival game. At the moment, i have the sprite which is a ship and moves by rotating left or right then going forward in that direction. I have implemented a 2D camera, its always centered on the player. However, when i move towards the bounds of the world that the sprite is in it just keeps on going :( How to i sort it that it stops at the edge of the world and cant go beyond it? Cheers :) Below is the main game class using System; using System.Collections.Generic; using System.Linq; using Microsoft.Xna.Framework; using Microsoft.Xna.Framework.Audio; using Microsoft.Xna.Framework.Content; using Microsoft.Xna.Framework.GamerServices; using Microsoft.Xna.Framework.Graphics; using Microsoft.Xna.Framework.Input; using Microsoft.Xna.Framework.Media; namespace GamesCoursework_1 { /// <summary> /// This is the main type for your game /// </summary> public class Game1 : Microsoft.Xna.Framework.Game { GraphicsDeviceManager graphics; SpriteBatch spriteBatch; // player variables Texture2D Ship; Vector2 Ship_Position; float Ship_Rotation = 0.0f; Vector2 Ship_Origin; Vector2 Ship_Velocity; const float tangentialVelocity = 4f; float friction = 0.05f; static Point CameraViewport = new Point(800, 800); Camera2d cam = new Camera2d((int)CameraViewport.X, (int)CameraViewport.Y); //Size of world static Point worldSize = new Point(1600, 1600); // Screen variables static Point worldCenter = new Point(worldSize.X / 2, worldSize.Y / 2); Rectangle playerBounds = new Rectangle(CameraViewport.X / 2, CameraViewport.Y / 2, worldSize.X - CameraViewport.X, worldSize.Y - CameraViewport.Y); Rectangle worldBounds = new Rectangle(0, 0, worldSize.X, worldSize.Y); Texture2D background; public Game1() { graphics = new GraphicsDeviceManager(this); graphics.PreferredBackBufferWidth = CameraViewport.X; graphics.PreferredBackBufferHeight = CameraViewport.Y; Content.RootDirectory = "Content"; } /// <summary> /// Allows the game to perform any initialization it needs to before starting to run. /// This is where it can query for any required services and load any non-graphic /// related content. Calling base.Initialize will enumerate through any components /// and initialize them as well. /// </summary> protected override void Initialize() { // TODO: Add your initialization logic here base.Initialize(); } /// <summary> /// LoadContent will be called once per game and is the place to load /// all of your content. /// </summary> protected override void LoadContent() { // Create a new SpriteBatch, which can be used to draw textures. spriteBatch = new SpriteBatch(GraphicsDevice); // TODO: use this.Content to load your game content here Ship = Content.Load<Texture2D>("Ship"); Ship_Origin.X = Ship.Width / 2; Ship_Origin.Y = Ship.Height / 2; background = Content.Load<Texture2D>("aus"); Ship_Position = new Vector2(worldCenter.X, worldCenter.Y); cam.Pos = Ship_Position; cam.Zoom = 1f; } /// <summary> /// UnloadContent will be called once per game and is the place to unload /// all content. /// </summary> protected override void UnloadContent() { // TODO: Unload any non ContentManager content here } /// <summary> /// Allows the game to run logic such as updating the world, /// checking for collisions, gathering input, and playing audio. /// </summary> /// <param name="gameTime">Provides a snapshot of timing values.</param> protected override void Update(GameTime gameTime) { // Allows the game to exit if (GamePad.GetState(PlayerIndex.One).Buttons.Back == ButtonState.Pressed) this.Exit(); // TODO: Add your update logic here Ship_Position = Ship_Velocity + Ship_Position; keyPressed(); base.Update(gameTime); } /// <summary> /// This is called when the game should draw itself. /// </summary> /// <param name="gameTime">Provides a snapshot of timing values.</param> protected override void Draw(GameTime gameTime) { GraphicsDevice.Clear(Color.CornflowerBlue); // TODO: Add your drawing code here spriteBatch.Begin(SpriteSortMode.Deferred, BlendState.AlphaBlend, null, null, null,null, cam.get_transformation(GraphicsDevice)); spriteBatch.Draw(background, Vector2.Zero, Color.White); spriteBatch.Draw(Ship, Ship_Position, Ship.Bounds, Color.White, Ship_Rotation, Ship_Origin, 1.0f, SpriteEffects.None, 0f); spriteBatch.End(); base.Draw(gameTime); } private void Ship_Move(Vector2 move) { Ship_Position += move; } private void keyPressed() { KeyboardState keyState; // Move right keyState = Keyboard.GetState(); if (keyState.IsKeyDown(Keys.Right)) { Ship_Rotation = Ship_Rotation + 0.1f; } if (keyState.IsKeyDown(Keys.Left)) { Ship_Rotation = Ship_Rotation - 0.1f; } if (keyState.IsKeyDown(Keys.Up)) { Ship_Velocity.X = (float)Math.Cos(Ship_Rotation) * tangentialVelocity; Ship_Velocity.Y = (float)Math.Sin(Ship_Rotation) * tangentialVelocity; if ((int)Ship_Position.Y < playerBounds.Bottom && (int)Ship_Position.Y > playerBounds.Top) cam._pos.Y = Ship_Position.Y; if ((int)Ship_Position.X > playerBounds.Left && (int)Ship_Position.X < playerBounds.Right) cam._pos.X = Ship_Position.X; //tried world bounds here if (!worldBounds.Contains(new Point((int)Ship_Position.X, (int)Ship_Position.Y))) Ship_Position -= new Vector2(0.0f, -tangentialVelocity * 2); if (!worldBounds.Contains(new Point((int)Ship_Position.X, (int)Ship_Position.Y))) Ship_Position -= new Vector2(0.0f, 2 * tangentialVelocity); } else if(Ship_Velocity != Vector2.Zero) { float i = Ship_Velocity.X; float j = Ship_Velocity.Y; Ship_Velocity.X = i -= friction * i; Ship_Velocity.Y = j -= friction * j; if ((int)Ship_Position.Y < playerBounds.Bottom && (int)Ship_Position.Y > playerBounds.Top) cam._pos.Y = Ship_Position.Y; if ((int)Ship_Position.X > playerBounds.Left && (int)Ship_Position.X < playerBounds.Right) cam._pos.X = Ship_Position.X; } if (keyState.IsKeyDown(Keys.Q)) { if (cam.Zoom < 2f) cam.Zoom += 0.05f; } if (keyState.IsKeyDown(Keys.A)) { if (cam.Zoom > 0.3f) cam.Zoom -= 0.05f; } } } } my 2d camera class using System; using System.Collections.Generic; using System.Linq; using System.Text; using Microsoft.Xna.Framework; using Microsoft.Xna.Framework.Graphics; namespace GamesCoursework_1 { public class Camera2d { protected float _zoom; // Camera Zoom public Matrix _transform; // Matrix Transform public Vector2 _pos; // Camera Position protected float _rotation; // Camera Rotation public int _viewportWidth, _viewportHeight; // viewport size public Camera2d(int ViewportWidth, int ViewportHeight) { _zoom = 1.0f; _rotation = 0.0f; _pos = Vector2.Zero; _viewportWidth = ViewportWidth; _viewportHeight = ViewportHeight; } // Sets and gets zoom public float Zoom { get { return _zoom; } set { _zoom = value; if (_zoom < 0.1f) _zoom = 0.1f; } // Negative zoom will flip image } public float Rotation { get { return _rotation; } set { _rotation = value; } } // Auxiliary function to move the camera public void Move(Vector2 amount) { _pos += amount; } // Get set position public Vector2 Pos { get { return _pos; } set { _pos = value; } } public Matrix get_transformation(GraphicsDevice graphicsDevice) { _transform = // Thanks to o KB o for this solution Matrix.CreateTranslation(new Vector3(-_pos.X, -_pos.Y, 0)) * Matrix.CreateRotationZ(Rotation) * Matrix.CreateScale(new Vector3(Zoom, Zoom, 1)) * Matrix.CreateTranslation(new Vector3(_viewportWidth * 0.5f, _viewportHeight * 0.5f, 0)); return _transform; } } }

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• Software to consolidate contacts from multiple sources?

  - by Neil

  I'm looking for an app that can take my contacts from Gmail, Facebook, and my mobile phone, to come up with one consolidated address book that, for each contact, contains the name, email address, facebook username, and mobile number, and if possible, export this data to the Mac Address Book. Is there any app that can do this? Online or offline will do. Currently, I've been only able to find apps that need to be hosted on my own server, such as the ones below. Isn't there any standalone desktop or web app? knowee[dot]net/ noserub[dot]com/ diso-project[dot]org/

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• Import GraphViz graph to Microsoft Word 14

  - by rmetzger

  I have created a GraphViz dot-file to visualize a data flow. I have to write a documentation using Microsoft Word and I'd like to include the graph in the document. For some wired reason, MS Word is not able to import SVG files. Then, I generated a .eps file using dot -Teps plan.dot -o plan.eps But once imported into Word, the picture looks horrible. I also tried to convert the svg to wmf using Inkscape. It also looked horrible. Is there a clean way to generate a file using GraphViz that Word can read?

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• Similar But Not The Same

  - by rickramsey

  A few weeks ago we published an article that explained how to use Oracle Solaris Cluster 3.3 5/11 to provide a virtual, multitiered architecture for Oracle Real Application Cluster (Oracle RAC) 11.2.0.2. We called it ... How to Deploy Oracle RAC on Zone Clusters Welllllll ... we just published another article just like it. Except that it's different. The earlier article was for Oracle RAC 11.2.0.2. This one is for Oracle RAC 11.2.0.3. This one describes how to do the same thing as the earlier one --create an Oracle Solaris Zone cluster, install and configure Oracle Grid Infrastructure and Oracle RAC in the zone cluster, and create an Oracle Solaris Cluster resource for Oracle RAC-- but for version 11.2.0.3 of Oracle RAC. Even though the objective is the same, and the version is only a dot-dot-dot release away, the process is quite different. So we decided to call it: How to Deploy Oracle RAC 11.2.0.3 on Zone Clusters Hope you can keep the different versions clear in your head. If not, let me know, and I'll try to make them easier to distinguish. - Rick Website Newsletter Facebook Twitter

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• Missing z-axis rotation for transforming between two vectors

  - by Steve Baughman

  I'm trying to rotate a cube so that it's facing up, but am getting hung up on the final implementation details. It now reliably will rotate the x,y axis to the correct side, but the z-axis is never rotating (See photos of before and after rotation). When I'm using the code below I always get '0' for my rotationVector.z. What am I missing here? // Define lookAt vector lookAtVector = GLKVector3Make(0,0,1); // Define axes vectors axes[0] = GLKVector3Make(0,0,1); axes[1] = GLKVector3Make(-1,0,0); axes[2] = GLKVector3Make(0,1,0); axes[3] = GLKVector3Make(1,0,0); axes[4] = GLKVector3Make(0,-1,0); axes[5] = GLKVector3Make(0,0,-1); CGFloat highest_dot = -1.0; GLKVector3 closest_axis; for(int i = 0; i < 6; i++) { // multiply cube's axes by existing matrix GLKVector3 axis = GLKMatrix4MultiplyVector3(matrix, axes[i]); CGFloat dot = GLKVector3DotProduct(axis, lookAtVector); if(dot > highest_dot) { closest_axis = axis; highest_dot = dot; } } GLKVector3 rotationVector = GLKVector3CrossProduct(closest_axis, lookAtVector); // Get angle between vectors CGFloat angle = atan2(GLKVector3Length(rotationVector), GLKVector3DotProduct(closest_axis, lookAtVector)); // normalize the rotation vector rotationVector = GLKVector3Normalize(rotationVector); // Create transform CATransform3D rotationTransform = CATransform3DMakeRotation(angle, rotationVector.x, rotationVector.y, rotationVector.z); // add rotation transform to existing transformation baseTransform = CATransform3DConcat(baseTransform, rotationTransform); return baseTransform; Before 3d Rotation After 3d Rotation Implementation based on this post

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• Component-wise GLSL vector branching

  - by Gustavo Maciel

  I'm aware that it usually is a BAD idea to operate separately on GLSL vec's components separately. For example: //use instrinsic functions, they do the calculation on 4 components at a time. float dot = v1.x*v2.x + v1.y * v2.y + v1.z * v2.z; //NEVER float dot = dot(v1, v2); //YES //Multiply one by one is not good too, since the ALU can do the 4 components at a time too. vec3 mul = vec3(v1.x * v2.x, v1.y * v2.y, v1.z * v2.z); //NEVER vec3 mul = v1 * v2; I've been struggling thinking, are there equivalent operations for branching? For example: vec4 Overlay(vec4 v1, vec4 v2, vec4 opacity) { bvec4 less = lessThan(v1, vec4(0.5)); vec4 blend; for(int i = 0; i < 4; ++i) { if(less[i]) blend[i] = 2.0 * v1[i]*v2[i]; else blend[i] = 1.0 - 2.0 * (1.0 - v1[i])*(1.0 - v2[i]); } return v1 + (blend-v1)*opacity; } This is a Overlay operator that works component wise. I'm not sure if this is the best way to do it, since I'm afraid these for and if can be a bottleneck later. Tl;dr, Can I branch component wise? If yes, how can I optimize that Overlay function with it?

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• backface culling error (in world space)

  - by acrilige

  I write simple software renderer. In my pipeline i have stage of backface culling. But looks like it has some error (see picture). I perform culling right after world transformation (is it correct?). (i can't insert picture in post coz i don't have enough points, so i just upload it (cube model): http://imageshack.us/photo/my-images/705/bcerror.png/) Vector3F view_dir(0.0f, 0.0f, 1.0f); std::vector<Triangle> to_remove; for (Triangle &t : m_triangles) { Vector4F e1 = t.v2 - t.v1; Vector4F e2 = t.v3 - t.v1; Vector3F normal( e1.y * e2.z - e1.z * e2.y, e1.z * e2.x - e1.x * e2.z, e1.x * e2.y - e1.y * e2.x ); normal.Normalize(); float dot = Dot(view_dir, normal); if (dot <= 0) to_remove.push_back(t); } for (Triangle& t : to_remove) m_triangles.erase(std::remove(m_triangles.begin(), m_triangles.end(), t), m_triangles.end()); Camera sits in origin and points in screen (RH). What is the reason? For better explanation i upload picture with cube rotation screenshots: http://imageshack.us/photo/my-images/842/bcmove.png/ UPDATED: The error occurs only when triangle has non-zero offset from origin UPDATED 2: If i process backface culling in clip space (after transforming all vertices with view and projection matrix), and just check z coordinate of triangle normal - it works perfect... Can i perform culing RIGHT BEFORE view/proj transforms? In this case looks like culling will not depends of projection and it's not right?.. UPDATED 3: I found answer and will post it in two hours - again coz of reputation lack.

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• Quaternion LookAt for camera

  - by Homar

  I am using the following code to rotate entities to look at points. glm::vec3 forwardVector = glm::normalize(point - position); float dot = glm::dot(glm::vec3(0.0f, 0.0f, 1.0f), forwardVector); float rotationAngle = (float)acos(dot); glm::vec3 rotationAxis = glm::normalize(glm::cross(glm::vec3(0.0f, 0.0f, 1.0f), forwardVector)); rotation = glm::normalize(glm::quat(rotationAxis * rotationAngle)); This works fine for my usual entities. However, when I use this on my Camera entity, I get a black screen. If I flip the subtraction in the first line, so that I take the forward vector to be the direction from the point to my camera's position, then my camera works but naturally my entities rotate to look in the opposite direction of the point. I compute the transformation matrix for the camera and then take the inverse to be the View Matrix, which I pass to my OpenGL shaders: glm::mat4 viewMatrix = glm::inverse( cameraTransform->GetTransformationMatrix() ); The orthographic projection matrix is created using glm::ortho. What's going wrong?

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• backface culling error

  - by acrilige

  I write simple software renderer. In my pipeline i have stage of backface culling. But looks like it has some error (see picture). I perform culling right after world transformation. (i can't insert picture in post coz i don't have enough points, so i just upload it (cube model): http://imageshack.us/photo/my-images/705/bcerror.png/) Vector3F view_dir(0.0f, 0.0f, 1.0f); std::vector<Triangle> to_remove; for (Triangle &t : m_triangles) { Vector4F e1 = t.v2 - t.v1; Vector4F e2 = t.v3 - t.v1; Vector3F normal( e1.y * e2.z - e1.z * e2.y, e1.z * e2.x - e1.x * e2.z, e1.x * e2.y - e1.y * e2.x ); normal.Normalize(); float dot = Dot(view_dir, normal); if (dot <= 0) to_remove.push_back(t); } for (Triangle& t : to_remove) m_triangles.erase(std::remove(m_triangles.begin(), m_triangles.end(), t), m_triangles.end()); Camera sits in origin and points in screen (RH). What is the reason?

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• Creating predefinied camera views - How do I move the camera to make sense while using Controller?

  - by Deukalion

  I'm trying to understand 3D but the one thing I can't seem to understand is the Camera. Right now I'm rendering four 3D Cubes with textures and I set the Project Matrix: public BasicCamera3D(float fieldOfView, float aspectRatio, float clipStart, float clipEnd, Vector3 cameraPosition, Vector3 cameraLookAt) { projection_fieldOfView = MathHelper.ToRadians(fieldOfView); projection_aspectRatio = aspectRatio; projection_clipstart = clipStart; projection_clipend = clipEnd; matrix_projection = Matrix.CreatePerspectiveFieldOfView(projection_fieldOfView, aspectRatio, clipStart, clipEnd); view_cameraposition = cameraPosition; view_cameralookat = cameraLookAt; matrix_view = Matrix.CreateLookAt(cameraPosition, cameraLookAt, Vector3.Up); } BasicCamera3D gameCamera = new BasicCamera3D(45f, GraphicsDevice.Viewport.AspectRatio, 1.0f, 1000f, new Vector3(0, 0, 8), new Vector3(0, 0, 0)); This creates a sort of "Top-Down" camera, with 8 (still don't get the unit type here - it's not pixels I guess?) But, if I try to position the camera at the side to make "Side-View" or "Reverse Side View" camera, the camera is rotating to much until it's turned around it a couple of times. I render the boxes at: new Vector3(-1, 0, 0) new Vector3(0, 0, 0) new Vector3(1, 0, 0) new Vector3(1, 0, 1) and with the Top-Down camera it shows good, but I don't get how I can make the camera show the side or 45 degrees from top (Like 3rd person action games) because the logic doesn't make sense. Also, since every object you render needs a new BasicEffect with a new projection/view/world - can you still use the "same" camera always so you don't have to create a new View/Matrix and such for each object. It's seems weird. If someone could help me get the camera to navigate around my objects "naturally" so I can be able to set a few predtermined views to choose from it would be really helpful. Are there some sort of algorithm to calculate the view for this and perhaps not simply one value? Examples: Top-Down-View: I have an object at 0, 0, 0 when I turn the right stick on the Xbox 360 Controller it should rotate around that object kind of, not flip and turn upside down, disappear and then magically appear as a tiny dot somewhere I have no clue where it is like it feels like it does now. Side-View: I have an object at 0, 0, 0 when I rotate to sides or up and down, the camera should be able to show a little more of the periphery to each side (depending on which you look at), and the same while moving up or down.

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• How do I apply skeletal animation from a .x (Direct X) file?

  - by Byte56

  Using the .x format to export a model from Blender, I can load a mesh, armature and animation. I have no problems generating the mesh and viewing models in game. Additionally, I have animations and the armature properly loaded into appropriate data structures. My problem is properly applying the animation to the models. I have the framework for applying the models and the code for selecting animations and stepping through frames. From what I understand, the AnimationKeys inside the AnimationSet supplies the transformations to transform the bind pose to the pose in the animated frame. As small example: Animation { {Armature_001_Bone} AnimationKey { 2; //Position 121; //number of frames 0;3; 0.000000, 0.000000, 0.000000;;, 1;3; 0.000000, 0.000000, 0.005524;;, 2;3; 0.000000, 0.000000, 0.022217;;, ... } AnimationKey { 0; //Quaternion Rotation 121; 0;4; -0.707107, 0.707107, 0.000000, 0.000000;;, 1;4; -0.697332, 0.697332, 0.015710, 0.015710;;, 2;4; -0.684805, 0.684805, 0.035442, 0.035442;;, ... } AnimationKey { 1; //Scale 121; 0;3; 1.000000, 1.000000, 1.000000;;, 1;3; 1.000000, 1.000000, 1.000000;;, 2;3; 1.000000, 1.000000, 1.000000;;, ... } } So, to apply frame 2, I would take the position, rotation and scale from frame 2, create a transformation matrix (call it Transform_A) from them and apply that matrix the vertices controlled by Armature_001_Bone at their weights. So I'd stuff TransformA into my shader and transform the vertex. Something like: vertexPos = vertexPos * bones[ int(bfs_BoneIndices.x) ] * bfs_BoneWeights.x; Where bfs_BoneIndices and bfs_BoneWeights are values specific to the current vertex. When loading in the mesh vertices, I transform them by the rootTransform and the meshTransform. This ensures they're oriented and scaled correctly for viewing the bind pose. The problem is when I create that transformation matrix (using the position, rotation and scale from the animation), it doesn't properly transform the vertex. There's likely more to it than just using the animation data. I also tried applying the bone transform hierarchies, still no dice. Basically I end up with some twisted models. It should also be noted that I'm working in openGL, so any matrix transposes that might need to be applied should be considered. What data do I need and how do I combine it for applying .x animations to models?

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• Everything turning black when pitching down

  - by Gordon

  Just a quick questions about something that's occurring in my world. Every time I pitch my camera downward, everything starts turning black, and if I pitch upward, everything sort of intensifies. I'm multiplying my normals by the normal matrix in the shader, and I'm multiplying my lights direction by the model view matrix. If I leave the normal and light dir in world space everything ends up fine. I thought putting them both in view space would not cause those weird things to happen?

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• Making a Camera look at a target Vector

  - by Peteyslatts

  I have a camera that works as long as its stationary. Now I'm trying to create a child class of that camera class that will look at its target. The new addition to the class is a method called SetTarget(). The method takes in a Vector3 target. The camera wont move but I need it to rotate to look at the target. If I just set the target, and then call CreateLookAt() (which takes in position, target, and up), when the object gets far enough away and underneath the camera, it suddenly flips right side up. So I need to transform the up vector, which currently always stays at Vector3.Up. I feel like this has something to do with taking the angle between the old direction vector and the new one (which I know can be expressed by target - position). I feel like this is all really vague, so here's the code for my base camera class: public class BasicCamera : Microsoft.Xna.Framework.GameComponent { public Matrix view { get; protected set; } public Matrix projection { get; protected set; } public Vector3 position { get; protected set; } public Vector3 direction { get; protected set; } public Vector3 up { get; protected set; } public Vector3 side { get { return Vector3.Cross(up, direction); } protected set { } } public BasicCamera(Game game, Vector3 position, Vector3 target, Vector3 up) : base(game) { this.position = position; this.direction = target - position; this.up = up; CreateLookAt(); projection = Matrix.CreatePerspectiveFieldOfView( MathHelper.PiOver4, (float)Game.Window.ClientBounds.Width / (float)Game.Window.ClientBounds.Height, 1, 500); } public override void Update(GameTime gameTime) { // TODO: Add your update code here CreateLookAt(); base.Update(gameTime); } } And this is the code for the class that extends the above class to look at its target. class TargetedCamera : BasicCamera { public Vector3 target { get; protected set; } public TargetedCamera(Game game, Vector3 position, Vector3 target, Vector3 up) : base(game, position, target, up) { this.target = target; } public void SetTarget(Vector3 target) { direction = target - position; } protected override void CreateLookAt() { view = Matrix.CreateLookAt(position, target, up); } }

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• rotating spheres

  - by Dave

  I want to continuously rotate 2 spheres, however the rotation does not seem to work. Here is my code: float angle = 0.0f; void light(){ glEnable(GL_LIGHTING); glEnable(GL_LIGHT0); glEnable(GL_LIGHT1); // Create light components GLfloat positionlight1[] = { 9.0, 5.0, 1.0, 0.0 }; GLfloat positionlight2[] = {0.2,2.5,1.3,0.0}; GLfloat light_ambient1[] = { 0.0, 0.0, 1.0, 1.0}; GLfloat light_diffuse[] = { 1.0, 1.0, 1.0, 1.0 }; glLightfv(GL_LIGHT0, GL_AMBIENT, light_ambient1); glLightfv(GL_LIGHT1, GL_DIFFUSE, light_diffuse); glLightfv(GL_LIGHT0, GL_POSITION, positionlight1); glLightfv(GL_LIGHT1, GL_POSITION, positionlight2); } void changeSize(int w, int h) { if (h==0) // Prevent A Divide By Zero By { h=1; // Making Height Equal One } glMatrixMode(GL_PROJECTION); // Select The Projection Matrix glLoadIdentity(); // Reset The Projection Matrix glViewport(0,0,w,h);// Reset The Current Viewport // Calculate The Aspect Ratio Of The Window gluPerspective(45.0f,(GLfloat)w/(GLfloat)h,0.1f,100.0f); glMatrixMode(GL_MODELVIEW); // Select The Modelview Matrix // Reset The Modelview Matrix } void renderScene(void) { glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); glPushMatrix(); //set where to start the current object glTranslatef(0.0,1.2,-6); glRotatef(angle,0,1.2,-6); glutSolidSphere(1,50,50); glPopMatrix(); //end the current object transformations glPushMatrix(); //set where to start the current object glTranslatef(0.0,-2,-6); glRotatef(angle,0,-2,-6); glutSolidSphere(0.5,50,50); glPopMatrix(); //end the current object transformations angle=+0.1; glutSwapBuffers(); } int main(int argc, char **argv) { // init GLUT and create window glutInit(&argc, argv); glutInitDisplayMode(GLUT_DEPTH | GLUT_DOUBLE | GLUT_RGBA); glutInitWindowPosition(100,100); glutInitWindowSize(500,500); glutCreateWindow("Hello World"); // register callbacks light(); glutDisplayFunc(renderScene); glutReshapeFunc(changeSize); glutIdleFunc(renderScene); // enter GLUT event processing loop glutMainLoop(); return 1; } Graphicstest::Graphicstest(void) { } In the renderscene where i draw,translate and rotate my 2 spheres. It does not seem to rotate the spheres continuously. What am i doing wrong?

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• Using Wicked with Devise for a sign up wizard

  - by demondeac11

  I am using devise with wicked to create a sign up wizard, but I am unsure about a problem I am having creating profiles. After a user provides their email & password they are forwarded to a step to create a profile based on whether they have specified they are a shipper or carrier. However I am unsure what the code should be in the controller and the forms to generically create a profile. Here is the code I have for the application: The steps controller: class UserStepsController < ApplicationController include Wicked::Wizard steps :carrier_profile, :shipper_profile def create @user = User.last case step when :carrier_profile @profile = CarrierProfile.create!(:dot => params[:dot]) if @profile.save render_wizard @user else flash[:alert] = "Record not saved" end when :shipper_profile @profile = ShipperProfile.create!(params[:shipper_profile) if @profile.save render_wizard @user else flash[:alert] = "Record not saved" end end end end end def show @user = User.last @carrier_profile = CarrierProfile.new @shipper_profile = ShipperProfile.new case step when :carrier_profile skip_step if @user.shipper? when :shipper_profile skip_step if @user.carrier? end render_wizard end end The form for a carrier profile: <% form_for @carrier_profile , url: wizard_path, method: :post do |f| %> <div> <%= f.label :dot, "Please enter your DOT Number:" %> <%= f.text_field :dot %> </div> <%= f.submit "Next Step", class: "btn btn-primary" %> <% end %> The form for a shipper profile: <% form_for @shipper_profile , url: wizard_path, method: :post do |f| %> <div> <%= f.label :company_name, "What is your company name?" %> <%= f.text_field :company_name %> </div> <%= f.submit "Next Step", class: "btn btn-primary" %> <% end %> The user model: class User < ActiveRecord::Base has_one :carrier_profile has_one :shipper_profile end How would I be able to write a generic new and create method to handle creating both profiles? With the current code it is stating that the user_steps controller has no POST method, although if I run rake routes I find that this is untrue.

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• Visual Studio Talk Show #117 is now online - Microsoft Surface (French)

  http://www.visualstudiotalkshow.com Simon Ferquel et Thomas Lebrun: Microsoft Surface Nous discutons avec Simon Ferquel et Thomas Lebrun du systme informatique "Surface". Surface se prsente l'utilisateur comme une table dont le dessus est constitu d'une surface dot dun affichage tactile "multitouch" qui permet de manipuler un contenu informatique l'aide d'un cran tactile. Thomas Lebrun est architecte et dveloppeur chez Access IT Paris. Il est particulirement intress...Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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• Visual Studio Talk Show #117 is now online - Microsoft Surface (French)

  http://www.visualstudiotalkshow.com Simon Ferquel et Thomas Lebrun: Microsoft Surface Nous discutons avec Simon Ferquel et Thomas Lebrun du systme informatique "Surface". Surface se prsente l'utilisateur comme une table dont le dessus est constitu d'une surface dot dun affichage tactile "multitouch" qui permet de manipuler un contenu informatique l'aide d'un cran tactile. Thomas Lebrun est architecte et dveloppeur chez Access IT Paris. Il est particulirement intress...Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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• Problem with Informix JDBC, MONEY and decimal separator in string literals

  - by Michal Niklas

  I have problem with JDBC application that uses MONEY data type. When I insert into MONEY column: insert into _money_test (amt) values ('123.45') I got exception: Character to numeric conversion error The same SQL works from native Windows application using ODBC driver. I live in Poland and have Polish locale and in my country comma separates decimal part of number, so I tried: insert into _money_test (amt) values ('123,45') And it worked. I checked that in PreparedStatement I must use dot separator: 123.45. And of course I can use: insert into _money_test (amt) values (123.45) But some code is "general", it imports data from csv file and it was safe to put number into string literal. How to force JDBC to use DBMONEY (or simply dot) in literals? My workstation is WinXP. I have ODBC and JDBC Informix client in version 3.50 TC5/JC5. I have set DBMONEY to just dot: DBMONEY=. EDIT: Test code in Jython: import sys import traceback from java.sql import DriverManager from java.lang import Class Class.forName("com.informix.jdbc.IfxDriver") QUERY = "insert into _money_test (amt) values ('123.45')" def test_money(driver, db_url, usr, passwd): try: print("\n\n%s\n--------------" % (driver)) db = DriverManager.getConnection(db_url, usr, passwd) c = db.createStatement() c.execute("delete from _money_test") c.execute(QUERY) rs = c.executeQuery("select amt from _money_test") while (rs.next()): print('[%s]' % (rs.getString(1))) rs.close() c.close() db.close() except: print("there were errors!") s = traceback.format_exc() sys.stderr.write("%s\n" % (s)) print(QUERY) test_money("com.informix.jdbc.IfxDriver", 'jdbc:informix-sqli://169.0.1.225:9088/test:informixserver=ol_225;DB_LOCALE=pl_PL.CP1250;CLIENT_LOCALE=pl_PL.CP1250;charSet=CP1250', 'informix', 'passwd') test_money("sun.jdbc.odbc.JdbcOdbcDriver", 'jdbc:odbc:test', 'informix', 'passwd') Results when I run money literal with dot and comma: C:\db_examples>jython ifx_jdbc_money.py insert into _money_test (amt) values ('123,45') com.informix.jdbc.IfxDriver -------------- [123.45] sun.jdbc.odbc.JdbcOdbcDriver -------------- there were errors! Traceback (most recent call last): File "ifx_jdbc_money.py", line 16, in test_money c.execute(QUERY) SQLException: java.sql.SQLException: [Informix][Informix ODBC Driver][Informix]Character to numeric conversion error C:\db_examples>jython ifx_jdbc_money.py insert into _money_test (amt) values ('123.45') com.informix.jdbc.IfxDriver -------------- there were errors! Traceback (most recent call last): File "ifx_jdbc_money.py", line 16, in test_money c.execute(QUERY) SQLException: java.sql.SQLException: Character to numeric conversion error sun.jdbc.odbc.JdbcOdbcDriver -------------- [123.45]

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• How do I append Word templates to a new document in VB.NET?

  - by Tom

  I'm poking around to see if this app can be done. Basically the end user needs to create a bunch of export documents that are populated from a database. There will be numerous document templates (.dot) and the end result will be the user choosing templates x y and z to include for documentation, click a button and have the app create a new Word document, append the templates, and then populate the templates with the appropriate data. The reason it needs to be done in Word as opposed to something like Crystal Reports is that the user may customize some fields before printing the documents as it can vary from export to export. Is this possible to do through VB.NET (VS 2010)? I assume it is but I'm having difficulty tracking down a solution. Or alternatively is there a better solution? Here's what I have so far (not much I know) Import Microsoft.Office.Interop Public Class Form1 Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click Dim oWord As Word.Application Dim oDoc As Word.Document oWord = CreateObject("Word.Application") oWord.Visible = False oDoc = oWord.Documents.Add 'Open templates x.dot, y.dot, z.dot 'Append above templates to new document created 'Populate new document oWord.Visible = True End Sub End Class Thanks.

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• problem with two key ranges in couchdb

  - by Duasto

  I'm having problem getting the right results in my coordinate system. To explain my system, I have this simple database that have x_axis, y_axis and name columns. I don't need to get all the data, I just need to display some part of it. For example, I have a coordinate system that have 10:10(meaning from x_axis -10 to 10 and from y_axis -10 to 10) and I want to display only 49 coordinates. In sql query I can do it something like this: "select * from coordinate where x_axis = -3 and x_axis <= 3 and y_axis = -3 y_axis <= 3" I tried this function but no success: "by_range": { "map": "function(doc) { emit([doc.x_axis, doc.y_axis], doc) }" } by_range?startkey=[-3,-3]&endkey=[3,3] I got a wrong results of: -3x-3 -3x-2 -3x-1 -3x0 -3x1 -3x2 -3x3 <-- should not display this part -- -3x4 -3x5 -3x6 -3x7 -3x8 -3x9 -3x10 <-- end of should not display this part -- ..... up to 3x3 to give you a better understanding of my project here is the screenshot of that I want to be made: Oops they don't allowed new poster to post an image img96(dot)imageshack(dot)us/img96/5382/coordinates(dot)jpg <<< just change the "(dot)" to "."

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