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• Scheduling algorithm optimized to execute during low usage periods.

  - by The Rook

  Lets say there is a Web Application serving mostly one country. Because of normal sleep habits website traffic follows a Sine wave, where 1 period lasts 24 hours and the lowest part of the wave is at about midnight. Is there a scheduling algorithm optimized to execute during low usage periods? I am thinking of this as a liquid that is "pored into" this sine wave to flatten out resource usage. A ideal algorithm would take the integral of this empty space. If the same tasks need to be run daily the amount of resources consumed by previous executions could be used to predict future usage by looking at the rate in which resource usage is increasing. By knowing the amount of resources required this algorithm could fill in this empty space while leaving as much buffer as possible on either side such that its interference was reduced as much as possible. It would also be possible to detect if there isn't enough resources before execution begins, this opens the door for a cloud to help out. Does anything like this exist? Or should I build it into an existing scheduler like quartz and make it open source?

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• Dual Monitors don't wake up...

  - by serhio

  Recently I put my second monitor on my computer. I have now two connections on my ATI graphic card: a VGA and newly added a DVI one. like this: Sine that, I need to start my computer with monitors powered ON, because if I do it after, thay does not "get up" and says that is "no video entry". Also, if I switch OFF my monitors when computer works, switching ON lets them in the sleep state... How can I fix this issue.

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• Box2D Platform body not moving player body along with it

  - by onedayitwillmake

  I am creating a game using Box2D (Javascript implementation) - and I added the ability to have a static platform, that is moved along an axis as a function of a sine. My problem is when the player lands on the platform, as the platform moves along the X axis - the player is not moved along with it, as you visually would expect. The player can land on the object, and if it hits the side of the object, it does colide with it and is pushed. This image might explain better than I did: After jumping on to the red platform the player character will fall off as the platform moves to the right UPDATE: Here is a live demo showing the problem: http://onedayitwillmake.com/ChuClone/slideexample.php

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• 2D wave-like sprite movement XNA

  - by TheBroodian

  I'm trying to create a particle that will 'circle' my character. When the particle is created, it's given a random position in relation to my character, and a box to provide boundaries for how far left or right this particle should circle. When I use the phrase 'circle', I'm referring to a simulated circling, i.e., when moving to the right, the particle will appear in front of my character, when passing back to the left, the particle will appear behind my character. That may have been too much context, so let me cut to the chase: In essence, the path I would like my particle to follow would be akin to a sine wave, with the left and right sides of the provided rectangle being the apexes of the wave. The trouble I'm having is that the position of the particle will be random, so it will never be produced at the same place within the wave twice, but I have no idea how to create this sort of behavior procedurally.

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• Deformation of Sphere using Transformations

  - by Mert Toka

  I have a graphic related question. I need to have a transformation matrix that I have no idea about what it is. The problem is to create right image from the right sphere. I created those images in Maya, but I need some matrices for the graphics course. Here is the image: Our professor told us to use some sine and cosine in our transformations, but I have no idea what he meant. I thought of intersecting a plane from the grid(that is xz plane) and sphere, and then scaling down the resulting circle. Would that work? I also checked this paper, however it looks like a bit advanced for me. Another thing is I guess that paper is not about the same type of information I was looking for. It would be great if you could help me.

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• License for library developed with commercial program

  - by Overv

  I'm developing a commercial application that largely depends on the functionality of a library that will be developed with it. I'd like to open-source this library, because it offers functionality that is not found elsewhere and can be useful in other applications. However, I will also use it in my own commercial application. I don't want to publish the source of the main application, but it is definitely not a derived work (think of calculator app using GPL licensed library to calculate sine). And if someone else commercially uses the library, I want to require them to publish any changes made. Is the GPL license suitable for this or is LGPL perhaps what I need?

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• How to tile multiple procedurally generated textures?

  - by Burhuc

  I'm trying to develop a procedural tile generator for a game, mostly for the ground tiles, instead of using "hand-drawn" tiles. To achieve this I'm using Perlin noise and a sine wave with multiple parameters, which already gives me pretty nice results. I don't want to generate 1 tile and repeat that one forever for one ground type, but I want to avoid recurrences, so I'm generating n different tiles. The problem I'm having now is that I want to tile the generated textures (smooth transitions). At the moment I have this: 4 256x256 textures. I thought a simple method would be to just add the positions of the different tiles to the noise generation algorithm, so that, when creating the 4 256x256 textures, it would behave like it would create a 512x512 texture, but that somehow didn't work as intented. So how can I tile those textures?

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• implement a coverflow UI in an Android web application

  - by ravidor

  I am trying to build a coverflow UI on an Android web application using HTML,CSS, JavaScript and some images. CSS 3D transforms, which are supported in Safari sine 2009 and on the iPhone since version 2.0, is not supported well on the Android. worse then that, the implementation is buggy on Android 2.1 and Android 2.2, and in each version in a different way. Any idea how can I build a coverflow UI on an Android web application using HTML,CSS, JavaScript and some images without CSS 3D transforms?

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• trigonometric functions in sqlite in iphone sdk

  - by Saurabh

  Hi is there a way to get sine and cosine of a value in sqlite query in iphone sdk? when ever i tried to use sin() in my query sqlite reported that no such function exists. Any help would be much appreciated! Thanks Saurabh

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• How to produce precisely-timed tone and silence in C#

  - by Bob Denny

  I have a C# project that plays Morse code for RSS feeds. I write it using Managed DirectX, only to discover that Managed DirectX is old and deprecated. The task I have is to play pure sine wave bursts interspersed with silence periods (the code) which are precisely timed as to their duration. I need to be able to call a function which plays a pure tone for so many milliseconds, then Thread.Sleep() then play another, etc. At its fastest, the tones and spaces can be as short as 40ms. It's working quite well in Managed DirectX. To get the precisely timed tone I create 1 sec. of sine wave into a secondary buffer, then to play a tone of a certain duration I seek forward to within x milliseconds of the end of the buffer then play. I've tried System.Media.SoundPlayer. It's a loser because you have to Play(), Sleep(), then Stop() for arbitrary tone lengths. The result is a tone that is too long, variable by CPU load. It takes an indeterminate amount of time to actually stop the tone. I then embarked on a lengthy attempt to use NAudio 1.3. I ended up with a memory resident stream providing the tone data, and again seeking forward leaving the desired length of tone remaining in the stream, then playing. This worked OK on the DirectSoundOut class for a while (see below) but the WaveOut class quickly dies with an internal assert saying that buffers are still on the queue despite PlayerStopped = true. This is odd since I play to the end then put a wait of the same duration between the end of the tone and the start of the next. You'd think that 80ms after starting Play of a 40 ms tone that it wouldn't have buffers on the queue. DirectSoundOut works well for a while, but its problem is that for every tone burst Play() it spins off a separate thread. Eventually (5 min or so) it just stops working. You can see thread after thread after thread exiting in the Output window while running the project in VS2008 IDE. I don't create new objects during playing, I just Seek() the tone stream then call Play() over and over, so I don't think it's a problem with orphaned buffers/whatever piling up till it's choked. I'm out of patience on this one, so I'm asking in the hopes that someone here has faced a similar requirement and can steer me in a direction with a likely solution. Thanks in advance...

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• How to produce precisely-timed tone and silence?

  - by Bob Denny

  I have a C# project that plays Morse code for RSS feeds. I write it using Managed DirectX, only to discover that Managed DirectX is old and deprecated. The task I have is to play pure sine wave bursts interspersed with silence periods (the code) which are precisely timed as to their duration. I need to be able to call a function which plays a pure tone for so many milliseconds, then Thread.Sleep() then play another, etc. At its fastest, the tones and spaces can be as short as 40ms. It's working quite well in Managed DirectX. To get the precisely timed tone I create 1 sec. of sine wave into a secondary buffer, then to play a tone of a certain duration I seek forward to within x milliseconds of the end of the buffer then play. I've tried System.Media.SoundPlayer. It's a loser because you have to Play(), Sleep(), then Stop() for arbitrary tone lengths. The result is a tone that is too long, variable by CPU load. It takes an indeterminate amount of time to actually stop the tone. I then embarked on a lengthy attempt to use NAudio 1.3. I ended up with a memory resident stream providing the tone data, and again seeking forward leaving the desired length of tone remaining in the stream, then playing. This worked OK on the DirectSoundOut class for a while (see below) but the WaveOut class quickly dies with an internal assert saying that buffers are still on the queue despite PlayerStopped = true. This is odd since I play to the end then put a wait of the same duration between the end of the tone and the start of the next. You'd think that 80ms after starting Play of a 40 ms tone that it wouldn't have buffers on the queue. DirectSoundOut works well for a while, but its problem is that for every tone burst Play() it spins off a separate thread. Eventually (5 min or so) it just stops working. You can see thread after thread after thread exiting in the Output window while running the project in VS2008 IDE. I don't create new objects during playing, I just Seek() the tone stream then call Play() over and over, so I don't think it's a problem with orphaned buffers/whatever piling up till it's choked. I'm out of patience on this one, so I'm asking in the hopes that someone here has faced a similar requirement and can steer me in a direction with a likely solution.

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• Creating simple waveforms with CoreAudio

  - by Koning Baard

  I am new to CoreAudio, and I would like to output a simple sine wave and square wave with a given frequency and amplitude through the speakers using CA. I don't want to use sound files as I want to synthesize the sound. What do I need to do this? And can you give me an example or tutorial? Thanks.

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• dynamically decorating objects in c#

  - by Oren Mazor

  is it possible to easily and dynamically decorate an object? for example, lets say I have a List<PointF>. this list is actually a plot of the sine function. I'd like to go through these points and add a flag to each PointF of whether it's a peak or not. but I don't want to create a new extended SpecialPointF or whatever, that has a boolean property. judge me all you want for being lazy, but laziness is how awesome ideas are born (also bad ideas)

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• Applications: The Mathematics of Movement, Part 2

  - by TechTwaddle

  In part 1 of this series we saw how we can make the marble move towards the click point, with a fixed speed. In this post we’ll see, first, how to get rid of Atan2(), sine() and cosine() in our calculations, and, second, reducing the speed of the marble as it approaches the destination, so it looks like the marble is easing into it’s final position. As I mentioned in one of the previous posts, this is achieved by making the speed of the marble a function of the distance between the marble and the destination point. Getting rid of Atan2(), sine() and cosine() Ok, to be fair we are not exactly getting rid of these trigonometric functions, rather, replacing one form with another. So instead of writing sin(?), we write y/length. You see the point. So instead of using the trig functions as below, double x = destX - marble1.x; double y = destY - marble1.y; //distance between destination and current position, before updating marble position distanceSqrd = x * x + y * y; double angle = Math.Atan2(y, x); //Cos and Sin give us the unit vector, 6 is the value we use to magnify the unit vector along the same direction incrX = speed * Math.Cos(angle); incrY = speed * Math.Sin(angle); marble1.x += incrX; marble1.y += incrY; we use the following, double x = destX - marble1.x; double y = destY - marble1.y; //distance between destination and marble (before updating marble position) lengthSqrd = x * x + y * y; length = Math.Sqrt(lengthSqrd); //unit vector along the same direction as vector(x, y) unitX = x / length; unitY = y / length; //update marble position incrX = speed * unitX; incrY = speed * unitY; marble1.x += incrX; marble1.y += incrY; so we replaced cos(?) with x/length and sin(?) with y/length. The result is the same.   Adding oomph to the way it moves In the last post we had the speed of the marble fixed at 6, double speed = 6; to make the marble decelerate as it moves, we have to keep updating the speed of the marble in every frame such that the speed is calculated as a function of the length. So we may have, speed = length/12; ‘length’ keeps decreasing as the marble moves and so does speed. The Form1_MouseUp() function remains the same as before, here is the UpdatePosition() method, private void UpdatePosition() {     double incrX = 0, incrY = 0;     double lengthSqrd = 0, length = 0, lengthSqrdNew = 0;     double unitX = 0, unitY = 0;     double speed = 0;     double x = destX - marble1.x;     double y = destY - marble1.y;     //distance between destination and marble (before updating marble position)     lengthSqrd = x * x + y * y;     length = Math.Sqrt(lengthSqrd);     //unit vector along the same direction as vector(x, y)     unitX = x / length;     unitY = y / length;     //speed as a function of length     speed = length / 12;     //update marble position     incrX = speed * unitX;     incrY = speed * unitY;     marble1.x += incrX;     marble1.y += incrY;     //check for bounds     if ((int)marble1.x < MinX + marbleWidth / 2)     {         marble1.x = MinX + marbleWidth / 2;     }     else if ((int)marble1.x > (MaxX - marbleWidth / 2))     {         marble1.x = MaxX - marbleWidth / 2;     }     if ((int)marble1.y < MinY + marbleHeight / 2)     {         marble1.y = MinY + marbleHeight / 2;     }     else if ((int)marble1.y > (MaxY - marbleHeight / 2))     {         marble1.y = MaxY - marbleHeight / 2;     }     //distance between destination and marble (after updating marble position)     x = destX - (marble1.x);     y = destY - (marble1.y);     lengthSqrdNew = x * x + y * y;     /*      * End Condition:      * 1. If there is not much difference between lengthSqrd and lengthSqrdNew      * 2. If the marble has moved more than or equal to a distance of totLenToTravel (see Form1_MouseUp)      */     x = startPosX - marble1.x;     y = startPosY - marble1.y;     double totLenTraveledSqrd = x * x + y * y;     if ((int)totLenTraveledSqrd >= (int)totLenToTravelSqrd)     {         System.Console.WriteLine("Stopping because Total Len has been traveled");         timer1.Enabled = false;     }     else if (Math.Abs((int)lengthSqrd - (int)lengthSqrdNew) < 4)     {         System.Console.WriteLine("Stopping because no change in Old and New");         timer1.Enabled = false;     } } A point to note here is that, in this implementation, the marble never stops because it travelled a distance of totLenToTravelSqrd (first if condition). This happens because speed is a function of the length. During the final few frames length becomes very small and so does speed; and so the amount by which the marble shifts is quite small, and the second if condition always hits true first. I’ll end this series with a third post. In part 3 we will cover two things, one, when the user clicks, the marble keeps moving in that direction, rebounding off the screen edges and keeps moving forever. Two, when the user clicks on the screen, the marble moves towards it, with it’s speed reducing by every frame. It doesn’t come to a halt when the destination point is reached, instead, it continues to move, rebounds off the screen edges and slowly comes to halt. The amount of time that the marble keeps moving depends on how far the user clicks from the marble. I had mentioned this second situation here. Finally, here’s a video of this program running,

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• Problem Implementing Texture on Libgdx Mesh of Randomized Terrain

  - by BrotherJack

  I'm having problems understanding how to apply a texture to a non-rectangular object. The following code creates textures such as this: from the debug renderer I think I've got the physical shape of the "earth" correct. However, I don't know how to apply a texture to it. I have a 50x50 pixel image (in the environment constructor as "dirt.png"), that I want to apply to the hills. I have a vague idea that this seems to involve the mesh class and possibly a ShapeRenderer, but the little i'm finding online is just confusing me. Bellow is code from the class that makes and regulates the terrain and the code in a separate file that is supposed to render it (but crashes on the mesh.render() call). Any pointers would be appreciated. public class Environment extends Actor{ Pixmap sky; public Texture groundTexture; Texture skyTexture; double tankypos; //TODO delete, temp public Tank etank; //TODO delete, temp int destructionRes; // how wide is a static pixel private final float viewWidth; private final float viewHeight; private ChainShape terrain; public Texture dirtTexture; private World world; public Mesh terrainMesh; private static final String LOG = Environment.class.getSimpleName(); // Constructor public Environment(Tank tank, FileHandle sfileHandle, float w, float h, int destructionRes) { world = new World(new Vector2(0, -10), true); this.destructionRes = destructionRes; sky = new Pixmap(sfileHandle); viewWidth = w; viewHeight = h; skyTexture = new Texture(sky); terrain = new ChainShape(); genTerrain((int)w, (int)h, 6); Texture tankSprite = new Texture(Gdx.files.internal("TankSpriteBase.png")); Texture turretSprite = new Texture(Gdx.files.internal("TankSpriteTurret.png")); tank = new Tank(0, true, tankSprite, turretSprite); Rectangle tankrect = new Rectangle(300, (int)tankypos, 44, 45); tank.setRect(tankrect); BodyDef terrainDef = new BodyDef(); terrainDef.type = BodyType.StaticBody; terrainDef.position.set(0, 0); Body terrainBody = world.createBody(terrainDef); FixtureDef fixtureDef = new FixtureDef(); fixtureDef.shape = terrain; terrainBody.createFixture(fixtureDef); BodyDef tankDef = new BodyDef(); Rectangle rect = tank.getRect(); tankDef.type = BodyType.DynamicBody; tankDef.position.set(0,0); tankDef.position.x = rect.x; tankDef.position.y = rect.y; Body tankBody = world.createBody(tankDef); FixtureDef tankFixture = new FixtureDef(); PolygonShape shape = new PolygonShape(); shape.setAsBox(rect.width*WORLD_TO_BOX, rect.height*WORLD_TO_BOX); fixtureDef.shape = shape; dirtTexture = new Texture(Gdx.files.internal("dirt.png")); etank = tank; } private void genTerrain(int w, int h, int hillnessFactor){ int width = w; int height = h; Random rand = new Random(); //min and max bracket the freq's of the sin/cos series //The higher the max the hillier the environment int min = 1; //allocating horizon for screen width Vector2[] horizon = new Vector2[width+2]; horizon[0] = new Vector2(0,0); double[] skyline = new double[width]; //TODO skyline necessary as an array? //ratio of amplitude of screen height to landscape variation double r = (int) 2.0/5.0; //number of terms to be used in sine/cosine series int n = 4; int[] f = new int[n*2]; //calculating omegas for sine series for(int i = 0; i < n*2 ; i ++){ f[i] = rand.nextInt(hillnessFactor - min + 1) + min; } //amp is the amplitude of the series int amp = (int) (r*height); double lastPoint = 0.0; for(int i = 0 ; i < width; i ++){ skyline[i] = 0; for(int j = 0; j < n; j++){ skyline[i] += ( Math.sin( (f[j]*Math.PI*i/height) ) + Math.cos(f[j+n]*Math.PI*i/height) ); } skyline[i] *= amp/(n*2); skyline[i] += (height/2); skyline[i] = (int)skyline[i]; //TODO Possible un-necessary float to int to float conversions tankypos = skyline[i]; horizon[i+1] = new Vector2((float)i, (float)skyline[i]); if(i == width) lastPoint = skyline[i]; } horizon[width+1] = new Vector2(800, (float)lastPoint); terrain.createChain(horizon); terrain.createLoop(horizon); //I have no idea if the following does anything useful :( terrainMesh = new Mesh(true, (width+2)*2, (width+2)*2, new VertexAttribute(Usage.Position, (width+2)*2, "a_position")); float[] vertices = new float[(width+2)*2]; short[] indices = new short[(width+2)*2]; for(int i=0; i < (width+2); i+=2){ vertices[i] = horizon[i].x; vertices[i+1] = horizon[i].y; indices[i] = (short)i; indices[i+1] = (short)(i+1); } terrainMesh.setVertices(vertices); terrainMesh.setIndices(indices); } Here is the code that is (supposed to) render the terrain. @Override public void render(float delta) { Gdx.gl.glClearColor(1, 1, 1, 1); Gdx.gl.glClear(GL10.GL_COLOR_BUFFER_BIT); // tell the camera to update its matrices. camera.update(); // tell the SpriteBatch to render in the // coordinate system specified by the camera. backgroundStage.draw(); backgroundStage.act(delta); uistage.draw(); uistage.act(delta); batch.begin(); debugRenderer.render(this.ground.getWorld(), camera.combined); batch.end(); //Gdx.graphics.getGL10().glEnable(GL10.GL_TEXTURE_2D); ground.dirtTexture.bind(); ground.terrainMesh.render(GL10.GL_TRIANGLE_FAN); //I'm particularly lost on this ground.step(); }

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• Latency, Ping and Other Questions

  - by Paulo Cassiano

  In a high traffic application, like an online auction system, few ms could determine 'to win or 'to lose' the 'battle'. I'm from Brazil. Here, I 'ping' local sites - like UOL - and receive replies in ~ 11ms. When I 'ping' US sites - like RackSpace - I receive replies in ~ 130 ms! The point is: I need a (very good like RackSpace [1]) infra-structure to host my killer online auction application, but there's no (RackSpace like) options in Brazil... Assuming that all users are located here, in Brazil, is it 'sine qua non' condition to host my application here, in Brazil? I think ~130 ms is a very high latency but, all users will receive this reply, sure? Well, where should I host my application? [1] Feel free to point me to any other very good host option other than RackSpace. I've cited it because I only know these guys...

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• Can't get sprite to rotate correctly?

  - by rphello101

  I'm attempting to play with graphics using Java/Slick 2d. I'm trying to get my sprite to rotate to wherever the mouse is on the screen and then move accordingly. I figured the best way to do this was to keep track of the angle the sprite is at since I have to multiply the cosine/sine of the angle by the move speed in order to get the sprite to go "forwards" even if it is, say, facing 45 degrees in quadrant 3. However, before I even worry about that, I'm having trouble even getting my sprite to rotate in the first place. Preliminary console tests showed that this code worked, but when applied to the sprite, it just kind twitches. Anyone know what's wrong? int mX = Mouse.getX(); int mY = HEIGHT - Mouse.getY(); int pX = sprite.x; int pY = sprite.y; int tempY, tempX; double mAng, pAng = sprite.angle; double angRotate=0; if(mX!=pX){ tempY=pY-mY; tempX=mX-pX; mAng = Math.toDegrees(Math.atan2(Math.abs((tempY)),Math.abs((tempX)))); if(mAng==0 && mX<=pX) mAng=180; } else{ if(mY>pY) mAng=270; else mAng=90; } //Calculations if(mX<pX&&mY<pY){ //If in Q2 mAng = 180-mAng; } if(mX<pX&&mY>pY){ //If in Q3 mAng = 180+mAng; } if(mX>pX&&mY>pY){ //If in Q4 mAng = 360-mAng; } angRotate = mAng-pAng; sprite.angle = mAng; sprite.image.setRotation((float)angRotate);

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• Adding 2D vector movement with rotation applied

  - by Michael Zehnich

  I am trying to apply a slight sine wave movement to objects that float around the screen to make them a little more interesting. I would like to apply this to the objects so that they oscillate from side to side, not front to back (so the oscillation does not affect their forward velocity). After reading various threads and tutorials, I have come to the conclusion that I need to create and add vectors, but I simply cannot come up with a solution that works. This is where I'm at right now, in the object's update method (updated based on comments): Vector2 oldPosition = new Vector2(spritePos.X, spritePos.Y); //note: newPosition is initially set in the constructor to spritePos.x/y Vector2 direction = newPosition - oldPosition; Vector2 perpendicular = new Vector2(direction.Y, -direction.X); perpendicular.Normalize(); sinePosAng += 0.1f; perpendicular.X += 2.5f * (float)Math.Sin(sinePosAng); spritePos.X += velocity * (float)Math.Cos(radians); spritePos.Y += velocity * (float)Math.Sin(radians); spritePos += perpendicular; newPosition = spritePos;

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• Spherical to Cartesian Coordinates

  - by user1258455

  Well I'm reading the Frank's Luna DirectX10 book and, while I'm trying to understand the first demo, I found something that's not very clear at least for me. In the updateScene method, when I press A, S, W or D, the angles mTheta and mPhi change, but after that, there are three lines of code that I don't understand exactly what they do: // Convert Spherical to Cartesian coordinates: mPhi measured from +y // and mTheta measured counterclockwise from -z. float x = 5.0f*sinf(mPhi)*sinf(mTheta); float z = -5.0f*sinf(mPhi)*cosf(mTheta); float y = 5.0f*cosf(mPhi); I mean, this explains that they do, it says that it converts the spherical coordinates to cartesian coordinates, but, mathematically, why? why the x value is calculated by the product of the sins of both angles? And the z by the product of the sine and cosine? and why the y just uses the cosine? After that, those values (x, y and z) are used to build the view matrix. The book doesn't explain (mathematically) why those values are calculated like that (and I didn't find anything to help me to understand it at the first Part of the book: "Mathematical prerequisites"), so it would be good if someone could explain me what exactly happen in those code lines or just give me a link that helps me to understand the math part. Thanks in advance!

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• Cube rotation DX10

  - by German

  Well I'm reading the Frank's Luna DirectX10 book and, while I'm trying to understand the first demo, I found something that's not very clear at least for me. In the updateScene method, when I press A, S, W or D, the angles mTheta and mPhi change, but after that, there are three lines of code that I don't understand exactly what they do: // Convert Spherical to Cartesian coordinates: mPhi measured from +y // and mTheta measured counterclockwise from -z. float x = 5.0f*sinf(mPhi)*sinf(mTheta); float z = -5.0f*sinf(mPhi)*cosf(mTheta); float y = 5.0f*cosf(mPhi); I mean, this explains that they do, it says that it converts the spherical coordinates to cartesian coordinates, but, mathematically, why? why the x value is calculated by the product of the sins of both angles? And the z by the product of the sine and cosine? and why the y just uses the cosine? After that, those values (x, y and z) are used to build the view matrix. The book doesn't explain (mathematically) why those values are calculated like that (and I didn't find anything to help me to understand it at the first Part of the book: "Mathematical prerequisites"), so it would be good if someone could explain me what exactly happen in those code lines or just give me a link that helps me to understand the math part. Thanks in advance!

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• 11415 compile errors FTW?!

  - by Koning Baard

  Hello. This is something I've really never seen but, I downloaded the source code of the sine wave example at http://www.audiosynth.com/sinewavedemo.html . It is in an old Project Builder Project format, and I want to compile it with Xcode (GCC). However, Xcode gives me 11415 compile errors. The first few are (all in the precompilation of AppKit.h): /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObject.h:31:0 /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObject.h:31: error: expected identifier or '(' before '-' token /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObject.h:33:0 /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObject.h:33: error: expected identifier or '(' before '-' token /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObject.h:35:0 /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObject.h:35: error: expected identifier or '(' before '-' token /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObject.h:36:0 /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObject.h:36: error: expected identifier or '(' before '-' token /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObject.h:37:0 /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObject.h:37: error: expected identifier or '(' before '-' token /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObject.h:38:0 /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObject.h:38: error: expected identifier or '(' before '-' token /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObject.h:40:0 /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObject.h:40: error: expected identifier or '(' before '-' token /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObject.h:42:0 /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObject.h:42: error: expected identifier or '(' before '@' token /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObject.h:48:0 /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObject.h:48: error: expected identifier or '(' before '@' token /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObject.h:54:0 /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObject.h:54: error: expected identifier or '(' before '@' token /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObject.h:59:0 /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObject.h:59: error: expected identifier or '(' before '-' token /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObject.h:61:0 /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObject.h:61: error: expected identifier or '(' before '@' token /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObject.h:69:0 /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObject.h:69: error: expected identifier or '(' before '+' token /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObject.h:71:0 /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObject.h:71: error: expected identifier or '(' before '+' token /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSValue.h:39:0 /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSValue.h:39: error: expected identifier or '(' before '-' token /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSValue.h:40:0 /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSValue.h:40: error: expected identifier or '(' before '-' token /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSValue.h:41:0 /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSValue.h:41: error: expected identifier or '(' before '-' token /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSValue.h:42:0 /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSValue.h:42: error: expected identifier or '(' before '-' token /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSValue.h:43:0 /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSValue.h:43: error: expected identifier or '(' before '-' token /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSValue.h:44:0 /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSValue.h:44: error: expected identifier or '(' before '-' token /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSValue.h:45:0 /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSValue.h:45: error: expected identifier or '(' before '-' token /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSValue.h:46:0 /Developer/SDKs/MacOSX10.6.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSValue.h:46: error: expected identifier or '(' before '-' token Some of the code is: HAL.c /* * HAL.c * Sinewave * * Created by james on Fri Apr 27 2001. * Copyright (c) 2001 __CompanyName__. All rights reserved. * */ #include "HAL.h" #include "math.h" appGlobals gAppGlobals; OSStatus appIOProc (AudioDeviceID inDevice, const AudioTimeStamp* inNow, const AudioBufferList* inInputData, const AudioTimeStamp* inInputTime, AudioBufferList* outOutputData, const AudioTimeStamp* inOutputTime, void* device); #define FailIf(cond, handler) \ if (cond) { \ goto handler; \ } #define FailWithAction(cond, action, handler) \ if (cond) { \ { action; } \ goto handler; \ } // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ // HAL Sample Code ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ //#define noErr 0 //#define false 0 OSStatus SetupHAL (appGlobalsPtr globals) { OSStatus err = noErr; UInt32 count, bufferSize; AudioDeviceID device = kAudioDeviceUnknown; AudioStreamBasicDescription format; // get the default output device for the HAL count = sizeof(globals->device); // it is required to pass the size of the data to be returned err = AudioHardwareGetProperty(kAudioHardwarePropertyDefaultOutputDevice, &count, (void *) &device); fprintf(stderr, "kAudioHardwarePropertyDefaultOutputDevice %d\n", err); if (err != noErr) goto Bail; // get the buffersize that the default device uses for IO count = sizeof(globals->deviceBufferSize); // it is required to pass the size of the data to be returned err = AudioDeviceGetProperty(device, 0, false, kAudioDevicePropertyBufferSize, &count, &bufferSize); fprintf(stderr, "kAudioDevicePropertyBufferSize %d %d\n", err, bufferSize); if (err != noErr) goto Bail; // get a description of the data format used by the default device count = sizeof(globals->deviceFormat); // it is required to pass the size of the data to be returned err = AudioDeviceGetProperty(device, 0, false, kAudioDevicePropertyStreamFormat, &count, &format); fprintf(stderr, "kAudioDevicePropertyStreamFormat %d\n", err); fprintf(stderr, "sampleRate %g\n", format.mSampleRate); fprintf(stderr, "mFormatFlags %08X\n", format.mFormatFlags); fprintf(stderr, "mBytesPerPacket %d\n", format.mBytesPerPacket); fprintf(stderr, "mFramesPerPacket %d\n", format.mFramesPerPacket); fprintf(stderr, "mChannelsPerFrame %d\n", format.mChannelsPerFrame); fprintf(stderr, "mBytesPerFrame %d\n", format.mBytesPerFrame); fprintf(stderr, "mBitsPerChannel %d\n", format.mBitsPerChannel); if (err != kAudioHardwareNoError) goto Bail; FailWithAction(format.mFormatID != kAudioFormatLinearPCM, err = paramErr, Bail); // bail if the format is not linear pcm // everything is ok so fill in these globals globals->device = device; globals->deviceBufferSize = bufferSize; globals->deviceFormat = format; Bail: return (err); } /* struct AudioStreamBasicDescription { Float64 mSampleRate; // the native sample rate of the audio stream UInt32 mFormatID; // the specific encoding type of audio stream UInt32 mFormatFlags; // flags specific to each format UInt32 mBytesPerPacket; // the number of bytes in a packet UInt32 mFramesPerPacket; // the number of frames in each packet UInt32 mBytesPerFrame; // the number of bytes in a frame UInt32 mChannelsPerFrame; // the number of channels in each frame UInt32 mBitsPerChannel; // the number of bits in each channel }; typedef struct AudioStreamBasicDescription AudioStreamBasicDescription; */ // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ // This is a simple playThru ioProc. It simply places the data in the input buffer back into the output buffer. // Watch out for feedback from Speakers to Microphone OSStatus appIOProc (AudioDeviceID inDevice, const AudioTimeStamp* inNow, const AudioBufferList* inInputData, const AudioTimeStamp* inInputTime, AudioBufferList* outOutputData, const AudioTimeStamp* inOutputTime, void* appGlobals) { appGlobalsPtr globals = appGlobals; int i; double phase = gAppGlobals.phase; double amp = gAppGlobals.amp; double pan = gAppGlobals.pan; double freq = gAppGlobals.freq * 2. * 3.14159265359 / globals->deviceFormat.mSampleRate; int numSamples = globals->deviceBufferSize / globals->deviceFormat.mBytesPerFrame; // assume floats for now.... float *out = outOutputData->mBuffers[0].mData; for (i=0; i<numSamples; ++i) { float wave = sin(phase) * amp; phase = phase + freq; *out++ = wave * (1.0-pan); *out++ = wave * pan; } gAppGlobals.phase = phase; return (kAudioHardwareNoError); } // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ OSStatus StartPlayingThruHAL(appGlobalsPtr globals) { OSStatus err = kAudioHardwareNoError; if (globals->soundPlaying) return 0; globals->phase = 0.0; err = AudioDeviceAddIOProc(globals->device, appIOProc, (void *) globals); // setup our device with an IO proc if (err != kAudioHardwareNoError) goto Bail; err = AudioDeviceStart(globals->device, appIOProc); // start playing sound through the device if (err != kAudioHardwareNoError) goto Bail; globals->soundPlaying = true; // set the playing status global to true Bail: return (err); } // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ OSStatus StopPlayingThruHAL(appGlobalsPtr globals) { OSStatus err = kAudioHardwareNoError; if (!globals->soundPlaying) return 0; err = AudioDeviceStop(globals->device, appIOProc); // stop playing sound through the device if (err != kAudioHardwareNoError) goto Bail; err = AudioDeviceRemoveIOProc(globals->device, appIOProc); // remove the IO proc from the device if (err != kAudioHardwareNoError) goto Bail; globals->soundPlaying = false; // set the playing status global to false Bail: return (err); } Sinewave.m // // a very simple Cocoa CoreAudio app // by James McCartney [email protected] www.audiosynth.com // // Sinewave - this class implements a sine oscillator with dezippered control of frequency, pan and amplitude // #import "Sinewave.h" // define a C struct from the Obj-C object so audio callback can access data typedef struct { @defs(Sinewave); } sinewavedef; // this is the audio processing callback. OSStatus appIOProc (AudioDeviceID inDevice, const AudioTimeStamp* inNow, const AudioBufferList* inInputData, const AudioTimeStamp* inInputTime, AudioBufferList* outOutputData, const AudioTimeStamp* inOutputTime, void* defptr) { sinewavedef* def = defptr; // get access to Sinewave's data int i; // load instance vars into registers double phase = def->phase; double amp = def->amp; double pan = def->pan; double freq = def->freq; double ampz = def->ampz; double panz = def->panz; double freqz = def->freqz; int numSamples = def->deviceBufferSize / def->deviceFormat.mBytesPerFrame; // assume floats for now.... float *out = outOutputData->mBuffers[0].mData; for (i=0; i<numSamples; ++i) { float wave = sin(phase) * ampz; // generate sine wave phase = phase + freqz; // increment phase // write output *out++ = wave * (1.0-panz); // left channel *out++ = wave * panz; // right channel // de-zipper controls panz = 0.001 * pan + 0.999 * panz; ampz = 0.001 * amp + 0.999 * ampz; freqz = 0.001 * freq + 0.999 * freqz; } // save registers back to object def->phase = phase; def->freqz = freqz; def->ampz = ampz; def->panz = panz; return kAudioHardwareNoError; } @implementation Sinewave - (void) setup { OSStatus err = kAudioHardwareNoError; UInt32 count; device = kAudioDeviceUnknown; initialized = NO; // get the default output device for the HAL count = sizeof(device); // it is required to pass the size of the data to be returned err = AudioHardwareGetProperty(kAudioHardwarePropertyDefaultOutputDevice, &count, (void *) &device); if (err != kAudioHardwareNoError) { fprintf(stderr, "get kAudioHardwarePropertyDefaultOutputDevice error %ld\n", err); return; } // get the buffersize that the default device uses for IO count = sizeof(deviceBufferSize); // it is required to pass the size of the data to be returned err = AudioDeviceGetProperty(device, 0, false, kAudioDevicePropertyBufferSize, &count, &deviceBufferSize); if (err != kAudioHardwareNoError) { fprintf(stderr, "get kAudioDevicePropertyBufferSize error %ld\n", err); return; } fprintf(stderr, "deviceBufferSize = %ld\n", deviceBufferSize); // get a description of the data format used by the default device count = sizeof(deviceFormat); // it is required to pass the size of the data to be returned err = AudioDeviceGetProperty(device, 0, false, kAudioDevicePropertyStreamFormat, &count, &deviceFormat); if (err != kAudioHardwareNoError) { fprintf(stderr, "get kAudioDevicePropertyStreamFormat error %ld\n", err); return; } if (deviceFormat.mFormatID != kAudioFormatLinearPCM) { fprintf(stderr, "mFormatID != kAudioFormatLinearPCM\n"); return; } if (!(deviceFormat.mFormatFlags & kLinearPCMFormatFlagIsFloat)) { fprintf(stderr, "Sorry, currently only works with float format....\n"); return; } initialized = YES; fprintf(stderr, "mSampleRate = %g\n", deviceFormat.mSampleRate); fprintf(stderr, "mFormatFlags = %08lX\n", deviceFormat.mFormatFlags); fprintf(stderr, "mBytesPerPacket = %ld\n", deviceFormat.mBytesPerPacket); fprintf(stderr, "mFramesPerPacket = %ld\n", deviceFormat.mFramesPerPacket); fprintf(stderr, "mChannelsPerFrame = %ld\n", deviceFormat.mChannelsPerFrame); fprintf(stderr, "mBytesPerFrame = %ld\n", deviceFormat.mBytesPerFrame); fprintf(stderr, "mBitsPerChannel = %ld\n", deviceFormat.mBitsPerChannel); } - (void)setAmpVal:(double)val { amp = val; } - (void)setFreqVal:(double)val { freq = val * 2. * 3.14159265359 / deviceFormat.mSampleRate; } - (void)setPanVal:(double)val { pan = val; } - (BOOL)start { OSStatus err = kAudioHardwareNoError; sinewavedef *def; if (!initialized) return false; if (soundPlaying) return false; // initialize phase and de-zipper filters. phase = 0.0; freqz = freq; ampz = amp; panz = pan; def = (sinewavedef *)self; err = AudioDeviceAddIOProc(device, appIOProc, (void *) def); // setup our device with an IO proc if (err != kAudioHardwareNoError) return false; err = AudioDeviceStart(device, appIOProc); // start playing sound through the device if (err != kAudioHardwareNoError) return false; soundPlaying = true; // set the playing status global to true return true; } - (BOOL)stop { OSStatus err = kAudioHardwareNoError; if (!initialized) return false; if (!soundPlaying) return false; err = AudioDeviceStop(device, appIOProc); // stop playing sound through the device if (err != kAudioHardwareNoError) return false; err = AudioDeviceRemoveIOProc(device, appIOProc); // remove the IO proc from the device if (err != kAudioHardwareNoError) return false; soundPlaying = false; // set the playing status global to false return true; } @end Can anyone help me compiling this example? I'd really appriciate it. Thanks

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• Javas Math.sin() produces NaN all the time

  - by milan1612

  Forgive me if this is a dumb beginners problem, but I really don't get it. I have a member variable declared like so: public Double Value; When I assign 3.14159265 to Value and try to compute the sine of it, this happens: system.out.println(Value.toString()); //outputs 3.14159265 Value = Math.sin(Value); system.out.println(Value.toString()); //outputs NaN In fact, this happens with every single value I tried - even with 0! Math.sin() seems to always produce NaN as a result, regardless of the arguments value. The docs say: If the argument is NaN or an infinity, then the result is NaN. But my argument is clearly not NaN or infinity! What the heck is happening there?

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• Math algorithm question

  - by Senica Gonzalez

  I'm not sure if this can be done without some determining factor....but wanted to see if someone knew of a way to do this. I want to create a shifting scale for numbers. Let's say I have the number 26000. I want the outcome of this algorithm to be 6500; or 25% of the original number. But if I have the number 5000, I want the outcome to be 2500; or 50% of the original number. The percentages don't have to be exact, this is just an example. I just want to have like a sine wave sort of thing. As the input number gets higher, the output number is a lower percentage of the input. Does that make sense?

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• Does GIT have evil twin issues?

  - by Senthil A Kumar

  In ClearCase evil twin occurs when two files are found with the same name in two different versions of the directory, and If the element OIDs are different but the names are the same. In GIT the SHA1 id is always unique and file with same name always have different SHA1 id’s. We don’t have a concept of Evil twins, but there are likely cases where there is chance for 2 or more developers creating a file with different contents with same filename in the same directory. During merge, when both files are completely different, there are chances of the developers to keep his changes alone and leave other changes resulting in code loss. Can anyone let me know if there will be issues in GIT similar to ClearCase or sine each SHA1 id is unique there won't be any Evil twin issues in GIT.

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• How to extract semi-precise frequencies from a WAV file using Fourier Transforms

  - by Seisatsu

  Let us say that I have a WAV file. In this file, is a series of sine tones at precise 1 second intervals. I want to use the FFTW library to extract these tones in sequence. Is this particularly hard to do? How would I go about this? Also, what is the bast way to write tones of this kind into a WAV file? I assume I would only need a simple audio library for the output. My language of choice is C

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