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• How to improve batching performance

  - by user4241

  Hello, I am developing a sprite based 2D game for mobile platform(s) and I'm using OpenGL (well, actually Irrlicht) to render graphics. First I implemented sprite rendering in a simple way: every game object is rendered as a quad with its own GPU draw call, meaning that if I had 200 game objects, I made 200 draw calls per frame. Of course this was a bad choice and my game was completely CPU bound because there is a little CPU overhead assosiacted in every GPU draw call. GPU stayed idle most of the time. Now, I thought I could improve performance by collecting objects into large batches and rendering these batches with only a few draw calls. I implemented batching (so that every game object sharing the same texture is rendered in same batch) and thought that my problems are gone... only to find out that my frame rate was even lower than before. Why? Well, I have 200 (or more) game objects, and they are updated 60 times per second. Every frame I have to recalculate new position (translation and rotation) for vertices in CPU (GPU on mobile platforms does not support instancing so I can't do it there), and doing this calculation 48000 per second (200*60*4 since every sprite has 4 vertices) simply seems to be too slow. What I could do to improve performance? All game objects are moving/rotating (almost) every frame so I really have to recalculate vertex positions. Only optimization that I could think of is a look-up table for rotations so that I wouldn't have to calculate them. Would point sprites help? Any nasty hacks? Anything else? Thanks.

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• How to fix issue with my 3D first person camera?

  - by dxCUDA

  My camera moves and rotates, but relative to the worlds origin, instead of the players. I am having difficulty rotating the camera and then translating the camera in the direction relative to the camera facing angle. I have been able to translate the camera and rotate relative to the players origin, but not then rotate and translate in the direction relative to the cameras facing direction. My goal is to have a standard FPS-style camera. float yaw, pitch, roll; D3DXMATRIX rotationMatrix; D3DXVECTOR3 Direction; D3DXMATRIX matRotAxis,matRotZ; D3DXVECTOR3 RotAxis; // Set the yaw (Y axis), pitch (X axis), and roll (Z axis) rotations in radians. pitch = m_rotationX * 0.0174532925f; yaw = m_rotationY * 0.0174532925f; roll = m_rotationZ * 0.0174532925f; up = D3DXVECTOR3(0.0f, 1.0f, 0.0f);//Create the up vector //Build eye ,lookat and rotation vectors from player input data eye = D3DXVECTOR3(m_fCameraX, m_fCameraY, m_fCameraZ); lookat = D3DXVECTOR3(m_fLookatX, m_fLookatY, m_fLookatZ); rotation = D3DXVECTOR3(m_rotationX, m_rotationY, m_rotationZ); D3DXVECTOR3 camera[3] = {eye,//Eye lookat,//LookAt up };//Up RotAxis.x = pitch; RotAxis.y = yaw; RotAxis.z = roll; D3DXVec3Normalize(&Direction, &(camera[1] - camera[0]));//Direction vector D3DXVec3Cross(&RotAxis, &Direction, &camera[2]);//Strafe vector D3DXVec3Normalize(&RotAxis, &RotAxis); // Create the rotation matrix from the yaw, pitch, and roll values. D3DXMatrixRotationYawPitchRoll(&matRotAxis, pitch,yaw, roll); //rotate direction D3DXVec3TransformCoord(&Direction,&Direction,&matRotAxis); //Translate up vector D3DXVec3TransformCoord(&camera[2], &camera[2], &matRotAxis); //Translate in the direction of player rotation D3DXVec3TransformCoord(&camera[0], &camera[0], &matRotAxis); camera[1] = Direction + camera[0];//Avoid gimble locking D3DXMatrixLookAtLH(&in_viewMatrix, &camera[0], &camera[1], &camera[2]);

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• Rotation of bitmap using a frame by frame animation

  - by pengume

  Hey every one I know this has probably been asked a ton of times but I just wanted to clarify if I am approaching this correctly, since I ran into some problems rotating a bitmap. So basically I have one large bitmap that has four frames drawn on it and I only draw one at a time by looping through the bitmap by increments to animate walking. I can get the bitmap to rotate correctly when it is not moving but once the animation starts it starts to cut off alot of the image and sometimes becomes very fuzzy. I have tried public void draw(Canvas canvas,int pointerX, int pointerY) { Matrix m; if (setRotation){ // canvas.save(); m = new Matrix(); m.reset(); // spriteWidth and spriteHeight are for just the current frame showed m.setTranslate(spriteWidth / 2, spriteHeight / 2); //get and set rotation for ninja based off of joystick m.preRotate((float) GameControls.getRotation()); //create the rotated bitmap flipedSprite = Bitmap.createBitmap(bitmap , 0, 0,bitmap.getWidth(),bitmap.getHeight() , m, true); //set new bitmap to rotated ninja setBitmap(flipedSprite); // canvas.restore(); Log.d("Ninja View", "angle of rotation= " +(float) GameControls.getRotation()); setRotation = false; } And then the Draw Method here // create the destination rectangle for the ninjas current animation frame // pointerX and pointerY are from the joystick moving the ninja around destRect = new Rect(pointerX, pointerY, pointerX + spriteWidth, pointerY + spriteHeight); canvas.drawBitmap(bitmap, getSourceRect(), destRect, null); The animation is four frames long and gets incremented by 66 (the size of one of the frames on the bitmap) for every frame and then back to 0 at the end of the loop.

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• Orthographic Projection Issue

  - by Nick

  I have a problem with my Ortho Matrix. The engine uses the perspective projection fine but for some reason the Ortho matrix is messed up. (See screenshots below). Can anyone understand what is happening here? At the min I am taking the Projection matrix * Transform (Translate, rotate, scale) and passing to the Vertex shader to multiply the Vertices by it. VIDEO Shows the same scene, rotating on the Y axis. http://youtu.be/2feiZAIM9Y0 void Matrix4f::InitOrthoProjTransform(float left, float right, float top, float bottom, float zNear, float zFar) { m[0][0] = 2 / (right - left); m[0][1] = 0; m[0][2] = 0; m[0][3] = 0; m[1][0] = 0; m[1][1] = 2 / (top - bottom); m[1][2] = 0; m[1][3] = 0; m[2][0] = 0; m[2][1] = 0; m[2][2] = -1 / (zFar - zNear); m[2][3] = 0; m[3][0] = -(right + left) / (right - left); m[3][1] = -(top + bottom) / (top - bottom); m[3][2] = -zNear / (zFar - zNear); m[3][3] = 1; } This is what happens with Ortho Matrix: This is the Perspective Matrix:

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• How can I move a polygon edge 1 unit away from the center?

  - by Stephen

  Let's say I have a polygon class that is represented by a list of vector classes as vertices, like so: var Vector = function(x, y) { this.x = x; this.y = y; }, Polygon = function(vectors) { this.vertices = vectors; }; Now I make a polygon (in this case, a square) like so: var poly = new Polygon([ new Vector(2, 2), new Vector(5, 2), new Vector(5, 5), new Vector(2, 5) ]); So, the top edge would be [poly.vertices[0], poly.vertices[1]]. I need to stretch this polygon by moving each edge away from the center of the polygon by one unit, along that edge's normal. The following example shows the first edge, the top, moved one unit up: The final polygon should look like this new one: var finalPoly = new Polygon([ new Vector(1, 1), new Vector(6, 1), new Vector(6, 6), new Vector(1, 6) ]); It is important that I iterate, moving one edge at a time, because I will be doing some collision tests after moving each edge. Here is what I tried so far (simplified for clarity), which fails triumphantly: for(var i = 0; i < vertices.length; i++) { var a = vertices[i], b = vertices[i + 1] || vertices[0]; // in case of final vertex var ax = a.x, ay = a.y, bx = b.x, by = b.y; // get some new perpendicular vectors var a2 = new Vector(-ay, ax), b2 = new Vector(-by, bx); // make into unit vectors a2.convertToUnitVector(); b2.convertToUnitVector(); // add the new vectors to the original ones a.add(a2); b.add(b2); // the rest of the code, collision tests, etc. } This makes my polygon start slowly rotating and sliding to the left, instead of what I need. Finally, the example shows a square, but the polygons in question could be anything. They will always be convex, and always with vertices in clockwise order.

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• Unity3d: calculate the result of a transform without modifying transform object itself

  - by Heisenbug

  I'm in the following situation: I need to move an object in some way, basically rotating it around its parent local position, or translating it in its parent local space (I know how to do this). The amount of rotation and translation is know at runtime (it depends on several factors, the speed of the object, enviroment factors, etc..). The problem is the following: I can perform this transformation only if the result position of the transformed object fit some criterias. An example could be this: the distance between the position before and after the transformation must be less than a given threshold. (Actually the conditions could be several and more complex) The problem is that if I use Transform.Rotate and Transform.Translate methods of my GameObject, I will loose the original Transform values. I think I can't copy the original Transform using instantiate for performance issues. How can I perform such a task? I think I have more or less 2 possibilities: First Don't modify the GameObject position through Transform. Calculate which will be the position after the transform. If the position is legal, modify transform through Translate and Rotate methods Second Store the original transform someway. Transform the object using Translate and Rotate. If the transformed position is illegal, restore the original one.

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• Logrotate Successful, original file goes back to original size

  - by drewrockshard

  Has anyone had any issues with logrotate before that causes a log file to get rotated and then go back to the same size it originally was? Here's my findings: Logrotate Script: /var/log/mylogfile.log { rotate 7 daily compress olddir /log_archives missingok notifempty copytruncate } Verbose Output of Logrotate: copying /var/log/mylogfile.log to /log_archives/mylogfile.log.1 truncating /var/log/mylogfile.log compressing log with: /bin/gzip removing old log /log_archives/mylogfile.log.8.gz Log file after truncate happens [root@server ~]# ls -lh /var/log/mylogfile.log -rw-rw-r-- 1 part1 part1 0 Jan 11 17:32 /var/log/mylogfile.log Literally Seconds Later: [root@server ~]# ls -lh /var/log/mylogfile.log -rw-rw-r-- 1 part1 part1 3.5G Jan 11 17:32 /var/log/mylogfile.log RHEL Version: [root@server ~]# cat /etc/redhat-release Red Hat Enterprise Linux ES release 4 (Nahant Update 4) Logrotate Version: [root@DAA21529WWW370 ~]# rpm -qa | grep logrotate logrotate-3.7.1-10.RHEL4 Few Notes: Service can't be restarted on the fly, so that's why I'm using copytruncate Logs are rotating every night, according to the olddir directory having log files in it from each night.

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• apache generating to many rotatelogs.exe on Windows?

  - by Patrick

  I'm seeing some odd behavior with Apache's rotatelogs.exe. On one of my servers I'm seeing multiple rotatelogs.exe counting into the 100's. Normally I usually only see 6 which I can rationalize to the 3 logs I have rotating. Does anyone know why this might be happening and how I can prevent it from happening. When the rotatelogs.exe processes get up into the 100's everything slows down and Apache is effectively shutdown because it can't process requests anymore. We are using the following line in our httpd.conf file: ErrorLog "|\"C:/Program Files/Apache2/bin/rotatelogs.exe\" \"C:/Program Files/Apache2/logs/error_log.%Y-%m-%d-%H_%M_%S\" 20M" Thanks in advance for the help!

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• logrotate by size outside the daily schedule

  - by Josh Smeaton

  We have a couple of applications that generate huge log files. It's not enough to rotate those logs daily, so I created the following logrotate conf: /var/log/ourapp/*log { compress copytruncate missingok size 200M rotate 10 } The idea is that we can keep 2GB of logs for this one application, no matter how quickly those files are filling up. The problem, though, is that logrotate only runs once daily. AFAIK, when logrotate kicks off at 4am, it will check to see that the size is at least 200M and rotate it if so. Ideally logrotate would run every minute, check the size, and rotate if the size is greater. Is there a standard way for rotating based on size outside of the daily cron schedule?

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• Obtaining a world point from a screen point with an orthographic projection

  - by vargonian

  I assumed this was a straightforward problem but it has been plaguing me for days. I am creating a 2D game with an orthographic camera. I am using a 3D camera rather than just hacking it because I want to support rotating, panning, and zooming. Unfortunately the math overwhelms me when I'm trying to figure out how to determine if a clicked point intersects a bounds (let's say rectangular) in the game. I was under the impression that I could simply transform the screen point (the clicked point) by the inverse of the camera's View * Projection matrix to obtain the world coordinates of the clicked point. Unfortunately this is not the case at all; I get some point that seems to be in some completely different coordinate system. So then as a sanity check I tried taking an arbitrary world point and transforming it by the camera's View*Projection matrices. Surely this should get me the corresponding screen point, but even that didn't work, and it is quickly shattering any illusion I had that I understood 3D coordinate systems and the math involved. So, if I could form this into a question: How would I use my camera's state information (view and projection matrices, for instance) to transform a world point to a screen point, and vice versa? I hope the problem will be simpler since I'm using an orthographic camera and can make several assumptions from that. I very much appreciate any help. If it makes a difference, I'm using XNA Game Studio.

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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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• (Quaternion based) Trouble moving foward based on model rotation

  - by ChocoMan

  Using quaternions, I'm having trouble moving my model in its facing direction. Currently the model moves can move in all cardinal directions with no problems. The problem comes when I rotate the move as it still travelling in the direction of world space. Meaning, if I'm moving forward, backward or any other direction while rotating the model, the model acts like its a figure skater spinning while traveling in the same direction. How do I update the direction of travel proper with the facing direction of the model? Rotates model on Y-axis: Yaw = pController.ThumbSticks.Right.X * MathHelper.ToRadians(speedAngleMAX); AddRotation = Quaternion.CreateFromYawPitchRoll(yaw, 0, 0); ModelLoad.MRotation *= AddRotation; MOrientation = Matrix.CreateFromQuaternion(ModelLoad.MRotation); Moves model forward: // Move Forward if (pController.IsButtonDown(Buttons.LeftThumbstickUp)) { SpeedX = (float)(Math.Sin(ModelLoad.ModelRotation)) * FWDSpeedMax * pController.ThumbSticks.Left.Y * (float)gameTime.ElapsedGameTime.TotalSeconds; SpeedZ = (float)(Math.Cos(ModelLoad.ModelRotation)) * FWDSpeedMax * pController.ThumbSticks.Left.Y * (float)gameTime.ElapsedGameTime.TotalSeconds; // Update model position ModelLoad._modelPos += Vector3.Forward * SpeedZ; ModelLoad._modelPos += Vector3.Left * SpeedX; }

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• Tinkerforge Rotation/LCD & JavaFX Plans

  - by Geertjan

  The first time I integrated two Tinkerforge bricklets, the day before yesterday, was pretty cool: import com.tinkerforge.BrickMaster; import com.tinkerforge.BrickletLCD20x4; import com.tinkerforge.BrickletRotaryPoti; import com.tinkerforge.IPConnection; import java.util.Calendar; public class TFConnectionDemo { private static final String HOST = "localhost"; private static final int PORT = 4223; private static final String MASTERBRICKUID = "somethingabc"; private static final String LCDUID = "somethingabc"; private static final String ROTIUID = "somethingabc"; private static IPConnection ipc; private static BrickMaster master = new BrickMaster(MASTERBRICKUID); private static BrickletLCD20x4 lcd = new BrickletLCD20x4(LCDUID); private static BrickletRotaryPoti poti = new BrickletRotaryPoti(ROTIUID); public static void main(String[] args) { try { ipc = new IPConnection(HOST, PORT); ipc.addDevice(master); ipc.addDevice(lcd); ipc.addDevice(poti); poti.setPositionCallbackPeriod(50); poti.addListener(new BrickletRotaryPoti.PositionListener() { @Override public void position(short position) { lcd.clearDisplay(); Calendar cal = Calendar.getInstance(); lcd.writeLine((short) 0, (short) 0, cal.getTime().toString()); lcd.writeLine((short) 1, (short) 0, "Rotation: " + position); } }); } catch (Exception e) { } } } The result is that the display text in the LCD bricklet changes while I turn the rotation bricklet: Now imagine that you have some JavaFX charts and, while you turn the rotation bricklet (i.e., the dial thing that I'm turning above), the values of the charts change. That would be pretty cool because you'd be able to animate the JavaFX charts by rotating an object externally, i.e., without even touching the keyboard. That would be pretty cool to see and shouldn't be hard to implement.

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• Camera Collision inside the room model

  - by sanddy

  I am having a problem in Calculating the camera collision for my Room model which consists of sofa, tables and other models. The users shall be moving the camera front, back, rotating so i need to make sure that the camera does not collide with any of the models with in the room. I have treated all my models inside the room by BoundingBox[] and the camera by BoundingSphere. So, far i have implemented collision by looking into the tutorial from http://www.toymaker.info/Games/XNA/html/xna_model_collisions.html which was great. But, I guess the problem lies in the Transformation part. I debugged and found some points to be at Vector(-XXX,-XXX,-XXX) where X is digit. Also i found my radius of some models where too large(in thousand, i just looked into its radius value before converting to BoundingBox). Do I need to scale the model for collision??? Below are my code:- On My LoadContent(): Matrix[] transforms = new Matrix[myModel.Bones.Count]; myModel.CopyAbsoluteBoneTransformsTo(transforms); int index = 0; box = new List<BoundingBox>(); BoundingBox worldModel = Utility.CalculateBoundingBox(myModel); foreach (ModelMesh mesh in myModel.Meshes) { Vector3[] obb = new Vector3[8]; worldModel.GetCorners(obb); Vector3[] asdf = (Vector3[])obb.Clone(); Vector3.Transform(obb, ref transforms[mesh.ParentBone.Index], obb); BoundingBox worldBox = BoundingBox.CreateFromPoints(obb); box.Add(worldBox); index++; } On CameraPosition Update: BoundingSphere bs = new BoundingSphere(this.cameraPos, 5.0f); if (RoomWalkthrough.Utility.CheckCollision(bs, bb)) { // Do Something } Please Help.

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• Unity3D: How to make the camera focus a moving game object with ITween?

  - by nathan

  I'm trying to write a solar system with Unity3D. Planets are sphere game objects rotating around another sphere game object representing the star. What i want to achieve is let the user click on a planet and then zoom the camera on this planet and then make the camera follow and keep it centered on the screen while it keep moving around the star. I decided to use iTween library and so far i was able to create the zoom effect using iTween.MoveUpdate. My problem is that the focused planet does not say properly centered as it moves. Here is the relevant part of my script: void Update () { if (Input.GetButtonDown("Fire1")) { Ray ray = Camera.main.ScreenPointToRay(Input.mousePosition); RaycastHit hit; if (Physics.Raycast(ray, out hit, Mathf.Infinity, concernedLayers)) { selectedPlanet = hit.collider.gameObject; } } } void LateUpdate() { if (selectedPlanet != null) { Vector3 pos = selectedPlanet.transform.position; pos.z = selectedPlanet.transform.position.z - selectedPlanet.transform.localScale.z; pos.y = selectedPlanet.transform.position.y; iTween.MoveUpdate(Camera.main.gameObject, pos, 2); } } What do i need to add to this script to make the selected planet stay centered on the screen? I hosted my current project as a webplayer application so you see what's going wrong. You can access it here.

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• Cocos2d/Cocos2d-x Attaching an arrow (sprite) to another body sprite (person)

  - by Satchmo Brown

  I am trying to set up a simple bow and arrow game. When the arrow hits the enemy body, the arrow's body is deleted and the arrow sprite continues to update, keeping the position correct in relation to the enemy it hit. Picture an arrow sticking into a body and that body still rotating and moving. My problem is that the rotation is completely wrong when the enemy rotates. I know how to do this in 3d with matrix transformation but I can't seem to figure it out in 2d with Cocos. Here is my method. I save offset at which the arrow hit the enemy. Every frame, I make the rotation of the sprite match the rotation of the enemy. Then, I apply the offset I took initially which is where the arrow hit the enemy. When they rotate, they rotate about their respective anchors and I am wondering if I need to set the anchor of the arrow to the center of the sprite. Does anyone know of an easy way to do this. If not, I will try to create an algorithm where the anchor is set to the offset divided by the width and height of the sprite image hopefully giving me the correct anchor values. Then I assume I need to reposition the sprite. Does anyone have a simpler way to do this?

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• How to rotate html5 canvas as page background?

  - by Sebastian P.R. Gingter

  Hi, I want to achieve the following: Image a white sheet of paper on a black desk. Then rotate the paper a little bit to the left (like, 25 degrees). Now you still have the black desk, and a rotated white box on it. In this rotated white box I want to place non-rotated normal html content like text, tables, div's etc. I already have a problem at the very first step: rotating a rectangle. This is my code so far: <html> <head> <script> function draw() { var canvas=document.getElementById("myCanvas"); var c=canvas.getContext("2d"); c.fillStyle = '#00'; c.fillRect(100, 100, 100, 100); c.rotate(20); c.fillStyle = '#ff0000'; c.fillRect(150, 150, 10, 10); } </script> </head> <body onload="draw()"> <canvas id="myCanvas" width="500" height="500"></canvas> </body> </html> With this, I see only a normal black box. Nothing else. I assume there should be a red, rotated box too, but there's nothing. What is the best approach to reach this and to have it as a (scaling) background for my web page?

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• Using AutoMySQLBackup on Rackspace Cloud

  - by xref

  Since Rackspace Cloud only allows FTP access it makes using AutoMySQLBackup a little trickier, and while it is at least creating DB dumps I get errors in the backup log: ###### WARNING ###### Errors reported during AutoMySQLBackup execution.. Backup failed Error log below.. .../backups/automysqlbackup: line 1791: /usr/bin/find: Permission denied .../backups/automysqlbackup: line 1855: /usr/bin/find: Permission denied .../backups/automysqlbackup: line 803: /usr/bin/find: Permission denied .../backups/automysqlbackup: line 1972: /usr/bin/du: Permission denied Since files are being created I'm assuming the find command failing has to do with actually rotating out and deleting the old backups? Line 803: find "${CONFIG_backup_dir}/${subfolder}${subsubfolder}" -mtime +"${rotation}" -type f -exec rm {} \; Any ideas for alternatives?

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• Rotate monitor to portrait on Windows Server 2003 with ATI card

  - by user10179

  Does anyone know if it is possible to rotate a monitor from landscape to portrait mode on Windows Server 2003 32-bit with an ATI video card? According to Dell's site, I should be able to rotate my Dell P2310H monitor by installing drivers from their website, but they don't have drivers for Windows Server 2003. I let Windows Update search for the driver (with the driver CD that came with the monitor in my drive) and it did install drivers, but I still don't see any options for rotating. Some people say that the ATI Catalyst Control Center allows for monitor rotation, but I've never been able to run that software on Windows Server 2003. A google search reports that others have the same problem. Has anyone successfully figured out how to rotate a monitor on Windows Server 2003 with an ATI card?

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• Rotate canvas along its center based on user touch - Android

  - by Ganapathy

  I want to rotate the canvas circularly on its center axis based on user touch. i want to rotate based on center but its rotating based on top left corner . so i am able to see only 1/4 for rotation of image. any idea.. Like a old phone dialer . I have tried like as follows onDraw(Canvas canvas){ canvas.save(); // do my rotation canvas.rotate(rotation,0,0); canvas.drawBitmap( ((BitmapDrawable)d).getBitmap(),0,0,p ); canvas.restore(); } @Override public boolean onTouchEvent(MotionEvent e) { float x = e.getX(); float y = e.getY(); updateRotation(x,y); mPreviousX = x; mPreviousY = y; invalidate(); } private void updateRotation(float x, float y) { double r = Math.atan2(x - centerX, centerY - y); rotation = (int) Math.toDegrees(r); }

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• Precision loss when transforming from cartesian to isometric

  - by Justin Skiles

  My goal is to display a tile map in isometric projection. This tile map has 25 tiles across and 25 tiles down. Each tile is 32x32. See below for how I'm accomplishing this. World Space World Space to Screen Space Rotation (45 degrees) Using a 2D rotation matrix, I use the following: double rotation = Math.PI / 4; double rotatedX = ((tileWorldX * Math.Cos(rotation)) - ((tileWorldY * Math.Sin(rotation))); double rotatedY = ((tileWorldX * Math.Sin(rotation)) + (tileWorldY * Math.Cos(rotation))); World Space to Screen Space Scale (Y-axis reduced by 50%) Here I simply scale down the Y value by a factor of 0.5. Problem And it works, kind of. There are some tiny 1px-2px gaps between some of the tiles when rendering. I think there's some precision loss somewhere, or I'm not understanding how to get these tiles to fit together perfectly. I'm not truncating or converting my values to non-decimal types until I absolutely have to (when I pass to the render method, which only takes integers). I'm not sure how to guarantee pixel perfect rendering precision when I'm rotating and scaling on a level of higher precision. Any advice? Do I need to supply for information?

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• Antenna Aligner part 2: Finding the right direction

  - by Chris George

  Last time I managed to get "my first app(tm)" built, published and running on my iPhone. This was really cool, a piece of my code running on my very own device. Ok, so I'm easily pleased! The next challenge was actually trying to determine what it was I wanted this app to do, and how to do it. Reverting back to good old paper and pen, I started sketching out designs for the app. I knew I wanted it to get a list of transmitters, then clicking on a transmitter would display a compass type view, with an arrow pointing the right way. I figured there would not be much point in continuing until I know I could do the graphical part of the project, i.e. the rotating compass, so armed with that reasoning (plus the fact I just wanted to get on and code!), I once again dived into visual studio. Using my friend (google) I found some example code for getting the compass data from the phone using the PhoneGap framework. // onSuccess: Get the current heading // function onSuccess(heading) {    alert('Heading: ' + heading); } navigator.compass.getCurrentHeading(onSuccess, onError); Using the ripple mobile emulator this showed that it was successfully getting the compass heading. But it didn't work when uploaded to my phone. It turns out that the examples I had been looking at were for PhoneGap 1.0, and Nomad uses PhoneGap 1.4.1. In 1.4.1, getCurrentHeading provides a compass object to onSuccess, not just a numeric value, so the code now looks like // onSuccess: Get the current magnetic heading // function onSuccess(heading) {    alert('Heading: ' + heading.magneticHeading); }; navigator.compass.getCurrentHeading(onSuccess, onError); So the lesson learnt from this... read the documentation for the version you are actually using! This does, however, lead to compatibility problems with ripple as it only supports 1.0 which is a real pain. I hope that the ripple system is updated sometime soon.

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• Ubuntu 12.04 LTS won't install - never finishes please help

  - by Richard Higgins

  Want to try Ubuntu after using Windows for 30 years. Tried to install it 5 times on a Lenovo X120e notebook and twice on a Lenovo M57 desktop. No luck, worse than what Microsoft puts you through. I burned 12.04 LTS to disc. It installs up to the "Who Are You?" screen, then stops. Accepted the recommended computer name and lower case user name. I chose "log me in automatically." After that there is no progress bar, no rotating or pulsing button, nothing to indicate the Ubuntu has not died or fallen asleep. Is that how it is written? Never heard of a program that would take a long time to install while a user looked at a locked, dead screen. I just bought the M57 desktop for my son. It came with Ubuntu 10 something. I wanted to upgrade to 12.04 but it crashed, twice, to a DOS screen saying the pc lacked a certain "init" file. Various help screen commands did not help. On the X120e, I thought a partial-failed Ubuntu install was causing the problem, so I removed the drive and deleted the Ubuntu partition and replaced it. But same result. After I fill in my name, accept computer and user name, the "continue" button does not appear to work. I can go "back" but not forward. I have waited torturous hours. It doesn't take more than two hours to install, does it?any It is my own fault because of the high expectations I had for a sensible, hassle-free installation, but I am immensely disappointed. Thank you for any response

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• 3D zooming technique to maintain the relative position of an object on screen

  - by stark

  Is it possible to zoom to a certain point on screen by modifying the field of view and rotating the view of the camera as to keep that point/object in the same place on screen while zooming ? Changing the camera position is not allowed. I projected the 3D pos of the object on screen and remembered it. Then on each frame I calculate the direction to it in camera space and then I construct a rotation matrix to align this direction to Z axis (in cam space). After this, I calculate the direction from the camera to the object in world space and transform this vector with the matrix I obtained earlier and then use this final vector as the camera's new direction. And it's actually "kinda working", the problem is that it is more/less off than the camera's rotation before starting to zoom depending on the area you are trying to zoom in (larger error on edges/corners). It looks acceptable, but I'm not settling for only this. Any suggestions/resources for doing this technique perfectly? If some of you want to explain the math in detail, be my guest, I can understand these things well.

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• Ubuntu 12.04 Precise on Dell Inspirion Duo

  - by Roman M. Kos

  I installed 12.04 version of Ubuntu on my Dell Inspiron Duo. After installing with help of program like UNetBootIn or smth like that. ( Besides i have no problem with kernel panic on chargin on/off like in 11.10. ) After that i followed with steps from here, in the first post here: http://ubuntuforums.org/showthread.php?t=1658635 There left one big problem with touchscreen: When i whant to drag with touchscreen like i`m doing it with mouse (for ex. selecting multile files with mouse) the selectable rectangular doesnot shows while im dragging, when dragging was finished (i put my finger off) it shows the rectangular and hides it. This thing disables all my tries to drag a window or smth else.... Also some time after using touchscreen such things are disabeling: - Often - click from a mouse (after keyboard using functinality restores) - less often - mouse movement disables (sometimes restores sometimes not) - lesser than other - keyboards works but no sygnals accepting (keyoards has indicator, so thay react, mouse of course not) The test from eTouchU utility passes perfeclty. Any idia for solving this problem? P.S.: Im from Ukraine, so sorry if my possible grammar mistakes. P.P.S.: Besides how to know the physicall position of my tabled mode? For automaticall rotating. Like on each rotation do some script.

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