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• Fraud and Anomaly Detection using Oracle Data Mining YouTube-like Video

  - by chberger

  I've created and recorded another YouTube-like presentation and "live" demos of Oracle Advanced Analytics Option, this time focusing on Fraud and Anomaly Detection using Oracle Data Mining.  [Note:  It is a large MP4 file that will open and play in place.  The sound quality is weak so you may need to turn up the volume.] Data is your most valuable asset. It represents the entire history of your organization and its interactions with your customers.  Predictive analytics leverages data to discover patterns, relationships and to help you even make informed predictions.   Oracle Data Mining (ODM) automatically discovers relationships hidden in data.  Predictive models and insights discovered with ODM address business problems such as:  predicting customer behavior, detecting fraud, analyzing market baskets, profiling and loyalty.  Oracle Data Mining, part of the Oracle Advanced Analytics (OAA) Option to the Oracle Database EE, embeds 12 high performance data mining algorithms in the SQL kernel of the Oracle Database. This eliminates data movement, delivers scalability and maintains security.  But, how do you find these very important needles or possibly fraudulent transactions and huge haystacks of data? Oracle Data Mining’s 1 Class Support Vector Machine algorithm is specifically designed to identify rare or anomalous records.  Oracle Data Mining's 1-Class SVM anomaly detection algorithm trains on what it believes to be considered “normal” records, build a descriptive and predictive model which can then be used to flags records that, on a multi-dimensional basis, appear to not fit in--or be different.  Combined with clustering techniques to sort transactions into more homogeneous sub-populations for more focused anomaly detection analysis and Oracle Business Intelligence, Enterprise Applications and/or real-time environments to "deploy" fraud detection, Oracle Data Mining delivers a powerful advanced analytical platform for solving important problems.  With OAA/ODM you can find suspicious expense report submissions, flag non-compliant tax submissions, fight fraud in healthcare claims and save huge amounts of money in fraudulent claims  and abuse.   This presentation and several brief demos will show Oracle Data Mining's fraud and anomaly detection capabilities.  

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• How to export 3D models that consist of several parts (eg. turret on a tank)?

  - by Will

  What are the standard alternatives for the mechanics of attaching turrets and such to 3D models for use in-game? I don't mean the logic, but rather the graphics aspects. My naive approach is to extend the MD2-like format that I'm using (blender-exported using a script) to include a new set of properties for a mesh that: is anchored in another 'parent' mesh. The anchor is a point and normal in the parent mesh and a point and normal in the child mesh; these will always be colinear, giving the child rotation but not translation relative to the parent point. has a normal that is aligned with a 'target'. Classically this target is the enemy that is being engaged, but it might be some other vector e.g. 'the wind' (for sails and flags (and smoke, which is a particle system but the same principle applies)) or 'upwards' (e.g. so bodies of riders bend properly when riding a horse up an incline etc). that the anchor and target alignments have maximum and minimum and a speed coeff. there is game logic for multiple turrets and on a model and deciding which engages which enemy. 'primary' and 'secondary' or 'target0' ... 'targetN' or some such annotation will be there. So to illustrate, a classic tank would be made from three meshes; a main body mesh, a turret mesh that is anchored to the top of the main body so it can spin only horizontally and a barrel mesh that is anchored to the front of the turret and can only move vertically within some bounds. And there might be a forth flag mesh on top of the turret that is aligned with 'wind' where wind is a function the engine solves that merges environment's wind angle with angle the vehicle is travelling in an velocity, or something fancy. This gives each mesh one degree of freedom relative to its parent. Things with multiple degrees of freedom can be modelled by zero-vertex connecting meshes perhaps? This is where I think the approach I outlined begins to feel inelegant, yet perhaps its still a workable system? This is why I want to know how it is done in professional games ;) Are there better approaches? Are there formats that already include this information? Is this routine?

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• Ray Intersecting Plane Formula in C++/DirectX

  - by user4585

  I'm developing a picking system that will use rays that intersect volumes and I'm having trouble with ray intersection versus a plane. I was able to figure out spheres fairly easily, but planes are giving me trouble. I've tried to understand various sources and get hung up on some of the variables used within their explanations. Here is a snippet of my code: bool Picking() { D3DXVECTOR3 vec; D3DXVECTOR3 vRayDir; D3DXVECTOR3 vRayOrig; D3DXVECTOR3 vROO, vROD; // vect ray obj orig, vec ray obj dir D3DXMATRIX m; D3DXMATRIX mInverse; D3DXMATRIX worldMat; // Obtain project matrix D3DXMATRIX pMatProj = CDirectXRenderer::GetInstance()->Director()->Proj(); // Obtain mouse position D3DXVECTOR3 pos = CGUIManager::GetInstance()->GUIObjectList.front().pos; // Get window width & height float w = CDirectXRenderer::GetInstance()->GetWidth(); float h = CDirectXRenderer::GetInstance()->GetHeight(); // Transform vector from screen to 3D space vec.x = (((2.0f * pos.x) / w) - 1.0f) / pMatProj._11; vec.y = -(((2.0f * pos.y) / h) - 1.0f) / pMatProj._22; vec.z = 1.0f; // Create a view inverse matrix D3DXMatrixInverse(&m, NULL, &CDirectXRenderer::GetInstance()->Director()->View()); // Determine our ray's direction vRayDir.x = vec.x * m._11 + vec.y * m._21 + vec.z * m._31; vRayDir.y = vec.x * m._12 + vec.y * m._22 + vec.z * m._32; vRayDir.z = vec.x * m._13 + vec.y * m._23 + vec.z * m._33; // Determine our ray's origin vRayOrig.x = m._41; vRayOrig.y = m._42; vRayOrig.z = m._43; D3DXMatrixIdentity(&worldMat); //worldMat = aliveActors[0]->GetTrans(); D3DXMatrixInverse(&mInverse, NULL, &worldMat); D3DXVec3TransformCoord(&vROO, &vRayOrig, &mInverse); D3DXVec3TransformNormal(&vROD, &vRayDir, &mInverse); D3DXVec3Normalize(&vROD, &vROD); When using this code I'm able to detect a ray intersection via a sphere, but I have questions when determining an intersection via a plane. First off should I be using my vRayOrig & vRayDir variables for the plane intersection tests or should I be using the new vectors that are created for use in object space? When looking at a site like this for example: http://www.tar.hu/gamealgorithms/ch22lev1sec2.html I'm curious as to what D is in the equation AX + BY + CZ + D = 0 and how does it factor in to determining a plane intersection? Any help will be appreciated, thanks.

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• Is 2 lines of push/pop code for each pre-draw-state too many?

  - by Griffin

  I'm trying to simplify vector graphics management in XNA; currently by incorporating state preservation. 2X lines of push/pop code for X states feels like too many, and it just feels wrong to have 2 lines of code that look identical except for one being push() and the other being pop(). The goal is to eradicate this repetitiveness,and I hoped to do so by creating an interface in which a client can give class/struct refs in which he wants restored after the rendering calls. Also note that many beginner-programmers will be using this, so forcing lambda expressions or other advanced C# features to be used in client code is not a good idea. I attempted to accomplish my goal by using Daniel Earwicker's Ptr class: public class Ptr<T> { Func<T> getter; Action<T> setter; public Ptr(Func<T> g, Action<T> s) { getter = g; setter = s; } public T Deref { get { return getter(); } set { setter(value); } } } an extension method: //doesn't work for structs since this is just syntatic sugar public static Ptr<T> GetPtr <T> (this T obj) { return new Ptr<T>( ()=> obj, v=> obj=v ); } and a Push Function: //returns a Pop Action for later calling public static Action Push <T> (ref T structure) where T: struct { T pushedValue = structure; //copies the struct data Ptr<T> p = structure.GetPtr(); return new Action( ()=> {p.Deref = pushedValue;} ); } However this doesn't work as stated in the code. How might I accomplish my goal? Example of code to be refactored: protected override void RenderLocally (GraphicsDevice device) { if (!(bool)isCompiled) {Compile();} //TODO: make sure state settings don't implicitly delete any buffers/resources RasterizerState oldRasterState = device.RasterizerState; DepthFormat oldFormat = device.PresentationParameters.DepthStencilFormat; DepthStencilState oldBufferState = device.DepthStencilState; { //Rendering code } device.RasterizerState = oldRasterState; device.DepthStencilState = oldBufferState; device.PresentationParameters.DepthStencilFormat = oldFormat; }

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• How to optimise mesh data

  - by Wardy

  So i have some procedurally generated mesh data and i want to reduce it down to its minimum number of verts. In case it matters this is a unity project. Working on the basis of a simple example, lets assume a typical flat surface of points 2 by 3. The point / vertex at [1,1] is used in many triangles. I've generated mesh for a voxel type engine that adds verts to a list based on face visiblility and now I want to remove all the duplicates. Can anyone come up with an efficient way of doing this because what i have is sooo bad its not even funny (and i don't even think it's logically correct) ... private void Optimize() { Vector3 v; Vector3 v2; for (int i = 0; i < Vertices.Count; i++) { v = Vertices[i]; for (int j = i+1; j < Vertices.Count; j++) { v2 = Vertices[j]; if (v.x == v2.x && v.y == v2.y && v.z == v2.z) { for (int ind = 0; ind < Indices.Count; ind++) { if (Indices[ind] == j) { Indices[ind] = i; } else if (Indices[ind] > j && Indices[ind] > 0) Indices[ind]--; } Vertices.RemoveAt(j); Uvs.RemoveAt(j); Normals.RemoveAt(j); } } } } EDIT: Ok i managed to get this (code sample above updated) to render an "optimised" set of verts but the UV data is all wrong now, which would make sense because i'm basically just removing any UV Vector that represents a UV coord for a removed vert and not actually considering what I need to do to "fix the tri" so to speak. The code now seemingly does work but its quite time consuming, still looking to further optimise.

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• How can I achieve a 3D-like effect with spritebatch's rotation and scale parameters

  - by Alic44

  I'm working on a 2d game with a top-down perspective similar to Secret of Mana and the 2D Final Fantasy games, with one big difference being that it's an action rpg using a 3-dimensional physics engine. I'm trying to draw an aimer graphic (basically an arrow) at my characters' feet when they're aiming a ranged weapon. At first I just converted the character's aim vector to radians and passed that into spritebatch, but there was a problem. The position of every object in my world is scaled for perspective when it's drawn to the screen. So if the physics engine coordinates are (1, 0, 1), the screen coords are actually (1, .707) -- the Y and Z axis are scaled by a perspective factor of .707 and then added together to get the screen coordinates. This meant that the direction the aimer graphic pointed (thanks to its rotation value passed into spritebatch) didn't match up with the direction the projectile actually traveled over time. Things looked fine when the characters fired left, right, up, or down, but if you fired on a diagonal the perspective of the physics engine didn't match with the simplistic way I was converting the character's aim direction to a screen rotation. Ok, fast forward to now: I've got the aimer's rotation matched up with the path the projectile will actually take, which I'm doing by decomposing a transform matrix which I build from two rotation matrices (one to represent the aimer's rotation, and one to represent the camera's 45 degree rotation on the x axis). My question is, is there a way to get not just rotation from a series of matrix transformations, but to also get a Vector2 scale which would give the aimer the appearance of being a 3d object, being warped by perspective? Orthographic perspective is what I'm going for, I think. So, the aimer arrow would get longer when facing sideways, and shorter when facing north and south because of the perspective. At the same time, it would get wider when facing north and south, and less wide when facing right or left. I'd like to avoid actually drawing the aimer texture in 3d because I'm still using spritebatch's layerdepth parameter at this point in my project, and I don't want to have to figure out how to draw a 3d object within the depth sorting system I already have. I can provide code and more details if this is too vague as a question... This is my first post on stack exchange. Thanks a lot for reading! Note: (I think) I realize it can't be a technically correct 3D perspective, because the spritebatch's vector2 scaling argument doesn't allow for an object to be skewed the way it actually should be. What I'm really interested in is, is there a good way to fake the effect, or should I just drop it and not scale at all? Edit to clarify without the help of a picture (apparently I can't post them yet): I want the aimer arrow to look like it has been painted on the ground at the character's feet, so it should appear to be drawn on the ground plane (in my case the XZ plane) which should be tilted at a 45 degree angle (around the X axis) from the viewing perspective. Alex

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• C++ and SDL resource management for 2D game

  - by KuruptedMagi

  My first question is about stateManagers. I do not use the singleton pattern (read many random posts with various reasons not to use it), I have gameStateManager which runs the pointer cCurrentGameState-render(), etc. I want to make a transitioning game, this engine should ideally cover both a platformer and a bird's eye RPG (with some recoding, I just mean the base engine), both of which will load different levels and events, such as world map, dungeon, shops, etc. So I then thought, rather then having to store all this data within all the states, I would break the engine into gameStates, and playStates... when gameState reaches gameStatePlay(), gameStatePlay simply runs the usual handleInput, logic, and render for the playStates, just as the low level gameStateManager does. This lets me store all the player data within the base playstate class without storing useless data in the gameStates. Now I have added a seperate mapEditor, which uses editorStates from gameStateEditor. Is this too much usage of the gameState concept? It seems to work pretty well for me, so I was wondering if I am too far off a common implementation of this. My second question is on image resources. I have my sprite class with nothing but static members, mainly loadImage, applySurface, and my screen pointer. I also have a map pairing imageName enums with actual SDL_Surface pointers, and one pairing clipNumber enums with a wrapper class for a vector of clips, so that each reference in the map can have different amounts of clips with different sizes. I thought it would be better to store all these images, and screen within one static body, since 20 different goblins all use the same sprite sheet, and all need to print to the same screen, and of course, this way I do not need to pass my screen reference to every little entity. The imageMap seems to work very well, I can even add the ability to search through the map at creation of entity type to see if a particular image at creation, creating if it doesnt exist, and destroying the image if the last entity that needs it was just destroyed. The vectored clip map however, seems to take too long to initialize, so if i run past the state that initializes them to fast, the game crashes <. Plus, the clip map call is half of this line =P SPRITE::applySurface( cEditorMap.cTiles[x][y].iX, cEditorMap.cTiles[x][y].iY, SPRITE::mImages[ IMAGE_TILEMAP ], SPRITE::screen, SPRITE::mImageClips[IMAGE_TILEMAP]->clips.at( cEditorMap.cTiles[x][y].iTileType ) ); Again, do I have the right idea? I like the imageMap, but am I better off with each entity storing its own clips? My last question is about collision detection. I only grasp the basics, will look at per-pixel and circular soon, but how can I determine which side the collision comes from with just the basic square collision detection, I tried breaking each entity into 4 collision zones, but that just gave me problems with walking through walls and the like <. Also, is per-pixel color collision a good way to decide what collision just occured, or is checking multiple colors for multiple entities too taxing each cycle?

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• Simple thruster like behaviour when rotating sprite

  - by ensamgud

  I'm prototyping some 2D game concepts with XNA and have added some basic keyboard inputs to control a triangle sprite. When I press key up the sprite accelerates in it's current facing direction, when I release the key it brakes down. For rotation, when I press left/right keys I rotate the sprite. Currently the sprite immedately changes direction when I rotate it. What I want is for it to keep moving in the same direction when I rotate, until I hit key up, adding thrust in whatever direction the sprite is pointing at. This would simulate thrusters on a classic space shooter like Asteroids. I'm adding an image to describe the behaviour I'm after and some code samples of how I'm doing things at the moment. This is my player struct, holding information of the sprite. public struct PlayerData { public Vector2 Position; // where to draw the sprite public Vector2 Direction; // travel direction of sprite public float Angle; // rotation of sprite public float Velocity; public float Acceleration; public float Decelleration; public float RotationAcceleration; public float RotationDecceleration; public float TopSpeed; public float Scale; } This is how I'm currently handling thrusting / braking (when pressing/releasing key up) (simplified, removed some bounds checking etc): player.Velocity += player.Acceleration * 0.1f; player.Velocity -= player.Acceleration * 0.1f; And when I rotate the sprite left and right: player.Angle -= player.RotationAcceleration * 0.1f; player.Angle += player.RotationAcceleration * 0.1f; This runs in the update loop, keeps the direction updated and updates the position: Vector2 up = new Vector2(0f, -1f); Matrix rotMatrix = Matrix.CreateRotationZ(player.Angle); player.Direction = Vector2.Transform(up, rotMatrix); player.Direction *= player.Velocity; player.Position += player.Direction; I am following along various beginner tutorials and haven't found any describing this, but I have tried some on my own without success. Do I need to change my velocity and acceleration fields to Vectors instead of floats to accomplish this type of movement? I realise my Angle and the Direction vector is currently tied together and I need to disconnect these somehow to be able to rotate freely without changing the direction of the movement, but I can't quite figure out how to do this while keeping the acceleration/decceleration functional. Would appreciate an explanation rather than pure code samples. Thanks,

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• I need help with specific types of movement.

  - by IronGiraffe

  I'm adding movable crates to my game and I need some help with my movement code. The way I've set up my movement code the crate's X and Y are moved according to a vector2 unless it hits a wall. Here's the movement code: if (frameCount % (delay / 2) == 0) { for (int i = 0; i < Math.Abs(cSpeed.X); i++) { if (!Level.PlayerHit(new Rectangle(crateBounds.X + (Math.Sign(cSpeed.X) * 32), crateBounds.Y, crateBounds.Width, crateBounds.Height))) { if (!Level.CollideTiles(crateBounds.X + (Math.Sign(cSpeed.X) * 32), crateBounds.Y, crateBounds.Width, crateBounds.Height)) { if (cSpeed.X != 0) { crateBounds.X += Math.Sign(cSpeed.X); } else { Equalize(2); } } else { cSpeed.X = 0f; } } else { if (!Level.CollideTiles(crateBounds.X - (Math.Sign(cSpeed.X) * 32), crateBounds.Y, crateBounds.Width, crateBounds.Height)) { if (cSpeed.X != 0) { crateBounds.X -= Math.Sign(cSpeed.X); } else { Equalize(2); } } else { cSpeed.X = 0f; } } } for (int i = 0; i < Math.Abs(cSpeed.Y); i++) { if (!Level.PlayerHit(new Rectangle(crateBounds.X, crateBounds.Y + Math.Sign(cSpeed.Y), crateBounds.Width, crateBounds.Height))) { if (!Level.CollideTiles(crateBounds.X, crateBounds.Y + Math.Sign(cSpeed.Y), crateBounds.Width, crateBounds.Height)) { crateBounds.Y += Math.Sign(cSpeed.Y); } else { cSpeed.Y = 0f; } } else { if (!Level.CollideTiles(crateBounds.X, crateBounds.Y - Math.Sign(cSpeed.Y), crateBounds.Width, crateBounds.Height)) { crateBounds.Y -= Math.Sign(cSpeed.Y); } else { cSpeed.Y = 0f; } } } } The frameCount and delay variables just slow down the movement somewhat. Anyway, I've added a tool to my game that acts as a gravity well (drawing objects into it's center; the closer they get to the center the faster they go) and what I'm trying to do is make it so that the crate will bounce off the player (and vice versa) when they collide. Thus far, my code only keeps the crate and player from getting stuck inside each other (the player can still get stuck under the crate, but I'll fix that later.) So what I'd like to know is how I can best make the crate bounce off the player. The other movement problem I'm having is related to another tool which allows the player to pick up crates and move around with them. The problem is that the crate's movement while being carried isn't tied to the movement script (it moves the crate itself, instead of adding to speed), which makes the crate go through walls and such. I know what I have to do: make the crate's speed match the player's speed while the player is holding it, but I need the crate to snap to a certain position (just in front of the player) when the player grabs it and it needs to switch to another position (just in front of the player on the other side) when they player faces the other direction while holding it. What would be the best way to make it switch places while keeping all the movement tied to the speed vector?

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• How to send multiple MVP matrices to a vertex shader in OpenGL ES 2.0

  - by Carbon Crystal

  I'm working my way through optimizing the rendering of sprites in a 2D game using OpenGL ES and I've hit the limit of my knowledge when it comes to GLSL and vertex shaders. I have two large float buffers containing my vertex coordinates and texture coordinates (eventually this will be one buffer) for multiple sprites in order to perform a single glDrawArrays call. This works but I've hit a snag when it comes to passing the transformation matrix into the vertex shader. My shader code is: uniform mat4 u_MVPMatrix; attribute vec4 a_Position; attribute vec2 a_TexCoordinate; varying vec2 v_TexCoordinate; void main() { v_TexCoordinate = a_TexCoordinate; gl_Position = u_MVPMatrix * a_Position; } In Java (Android) I am using a FloatBuffer to store the vertex/texture data and this is provided to the shader like so: mGlEs20.glVertexAttribPointer(mVertexHandle, Globals.GL_POSITION_VERTEX_COUNT, GLES20.GL_FLOAT, false, 0, mVertexCoordinates); mGlEs20.glVertexAttribPointer(mTextureCoordinateHandle, Globals.GL_TEXTURE_VERTEX_COUNT, GLES20.GL_FLOAT, false, 0, mTextureCoordinates); (The Globals.GL_POSITION_VERTEX_COUNT etc are just integers with the value of 2 right now) And I'm passing the MVP (Model/View/Projection) matrix buffer like this: GLES20.glUniformMatrix4fv(mMVPMatrixHandle, 1, false, mModelCoordinates); (mModelCoordinates is a FloatBuffer containing 16-float sequences representing the MVP matrix for each sprite) This renders my scene but all the sprites share the same transformation, so it's obviously only picking the first 16 elements from the buffer which makes sense since I am passing in "1" as the second parameter. The documentation for this method says: "This should be 1 if the targeted uniform variable is not an array of matrices, and 1 or more if it is an array of matrices." So I tried modifying the shader with a fixed size array large enough to accomodate most of my scenarios: uniform mat4 u_MVPMatrix[1000]; But this lead to an error in the shader: cannot convert from 'uniform array of 4X4 matrix of float' to 'Position 4-component vector of float' This just seems wrong anyway as it's not clear to me how the shader would know when to transition to the next matrix anyway. Anyone have an idea how I can get my shader to pick up a different MVP matrix (i.e. the NEXT 16 floats) from my MVP buffer for every 4 vertices it encounters? (I am using GL_TRIANGLE_STRIP so each sprite has 4 vertices). Thanks!

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• Best way to determine surface normal for a group of pixels?

  - by Paul Renton

  One of my current endeavors is creating a 2D destructible terrain engine for iOS Cocos2D (See https://github.com/crebstar/PWNDestructibleTerrain ). It is in an infant stages no doubt, but I have made significant progress since starting a couple weeks ago. However, I have run into a bit of a performance road block with calculating surface normals. Note: For my destructible terrain engine, an alpha of 0 is considered to not be solid ground. The method posted below works just great given small rectangles, such as n < 30. Anything above 30 causes a dip in the frame rate. If you approach 100x100 then you might as well read a book while the sprite attempts to traverse the terrain. At the moment this is the best I can come up with for altering the angle on a sprite as it roams across terrain (to get the angle for a sprite's orientation just take dot product of 100 * normal * (1,0) vector). -(CGPoint)getAverageSurfaceNormalAt:(CGPoint)pt withRect:(CGRect)area { float avgX = 0; float avgY = 0; ccColor4B color = ccc4(0, 0, 0, 0); CGPoint normal; float len; for (int w = area.size.width; w >= -area.size.width; w--) { for (int h = area.size.height; h >= -area.size.height; h--) { CGPoint pixPt = ccp(w + pt.x, h + pt.y); if ([self pixelAt:pixPt colorCache:&color]) { if (color.a != 0) { avgX -= w; avgY -= h; } // end inner if } // end outer if } // end inner for } // end outer for len = sqrtf(avgX * avgX + avgY * avgY); if (len == 0) { normal = ccp(avgX, avgY); } else { normal = ccp(avgX/len, avgY/len); } // end if return normal; } // end get My problem is I have sprites that require larger rectangles in order for their movement to look realistic. I considered doing a cache of all surface normals, but this lead to issues of knowing when to recalculate the surface normals and these calculations also being quite expensive (also how large should the blocks be?). Another smaller issue is I don't know how to properly treat the case when length is = 0. So I am stuck... Any advice from the community would be greatly appreciated! Is my method the best possible one? Or should I rethink the algorithm? I am new to game development and always looking to learn new tips and tricks.

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• Point line collision reaction

  - by user4523

  I am trying to program point line segment collision detection and reaction. I am doing this for fun and to learn. The point moves (it has a velocity, and can be controlled by the user), whilst the lines are strait and stationary. The lines are not axis aligned. Everything is in 2D. It is quite straight forward to work out if a collision has occurred. For each frame, the point moves from A to B. AB is a line, and if it crosses the line segment, a collision has occurred (or will occur) and I am able to work out the point of intersection (poi). The problem I am having is with the reaction. Ideally I would like the point to be prevented from moving across the line. In one frame, I can move the point back to the poi (or only alow it to move as far as the poi), and alter the velocity. The problem I am having with this approach (I think) is that, next frame the user may try to cross the line again. Although the point is on the poi, the point may not be exactly on the line. Since it is not axis aligned, I think there is always some subtle rounding issue (A float representation of a point on a line might be rounded to a point that is slightly on one side or the other). Because of this, next frame the path might not intersect the line (because it can start on the other side and move away from it) and the point is effectively allowed to cross the line. Firstly, does the analysis sound correct? Having accepted (maybe) that I cannot always exactly position the point on the line, I tried to move the point away from the line slightly (either along the normal to the line, or along the path vector). I then get a problem at edges. Attempting to fix one collision by moving the point away from the line (even slightly) can cause it to cross another line (one shape I am dealing with is a star, with sharp corners). This can mean that the solution to one collision inadvertently creates another collision, which is ignored. Again, does this sound correct? Anyway, whatever I try, I am having difficulty with edges, and the point is occasionally able to penetrate the polygons and cross lines, which is undesirable. Whilst I can find a lot of information about collision detection on the web (and on this site) I can find precious little information on collision reaction. Does any one know of any good point line collision reaction tutorials? Or is my approach too flawed/over complicated?

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• How to snap a 2D Quad to the mouse cursor using OpenGL 3.0/WIN32?

  - by NoobScratcher

  I've been having issues trying to snap a 2D Quad to the mouse cursor position I'm able : 1.) To get values into posX, posY, posZ 2.) Translate with the values from those 3 variables But the quad positioning I'm not able to do correctly in such a way that the 2D Quad is near the mouse cursor using those values from those 3 variables eg."posX, posY, posZ" I need the mouse cursor in the center of the 2D Quad. I'm hoping someone can help me achieve this. I've tried searching around with no avail. Heres the function that is ment to do the snapping but instead creates weird flicker or shows nothing at all only the 3d models show up : void display() { glClearColor(0.0,0.0,0.0,1.0); glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT); for(std::vector<GLuint>::iterator I = cube.begin(); I != cube.end(); ++I) { glCallList(*I); } if(DrawArea == true) { glReadPixels(winX, winY, 1, 1, GL_DEPTH_COMPONENT, GL_FLOAT, &winZ); cerr << winZ << endl; glGetDoublev(GL_MODELVIEW_MATRIX, modelview); glGetDoublev(GL_PROJECTION_MATRIX, projection); glGetIntegerv(GL_VIEWPORT, viewport); gluUnProject(winX, winY, winZ , modelview, projection, viewport, &posX, &posY, & posZ); glBindTexture(GL_TEXTURE_2D, DrawAreaTexture); glPixelStorei(GL_UNPACK_ALIGNMENT, 1); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST); glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_DECAL); glTexImage2D (GL_TEXTURE_2D, 0, GL_RGB, DrawAreaSurface->w, DrawAreaSurface->h, 0, GL_RGBA, GL_UNSIGNED_BYTE, DrawAreaSurface->pixels); glEnable(GL_TEXTURE_2D); glBindTexture(GL_TEXTURE_2D, DrawAreaTexture); glTranslatef(posX , posY, posZ); glBegin(GL_QUADS); glTexCoord2f (0.0, 0.0); glVertex3f(0.5, 0.5, 0); glTexCoord2f (1.0, 0.0); glVertex3f(0, 0.5, 0); glTexCoord2f (1.0, 1.0); glVertex3f(0, 0, 0); glTexCoord2f (0.0, 1.0); glVertex3f(0.5, 0, 0); glEnd(); } SwapBuffers(hDC); } I'm using : OpenGL 3.0 WIN32 API C++ GLSL if you really want the full source here it is - http://pastebin.com/1Ncm9HNf , Its pretty messy.

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• Collision rectangle response

  - by dotty

  I'm having difficulties getting a moveable rectangle to collide with more than one rectangle. I'm using SFML and it has a handy function called Intersect() which takes 2 rectangles and returns the intersections. I have a vector full of rectangles which I want my moveable rectangle to collide with. I'm looping through this using the following code (p is the moveble rectangle). IsCollidingWith returns a bool but also uses SFML's Interesect to work out the intersections. while(unsigned i = 0; i!= testRects.size(); i++){ if(p.IsCollidingWith(testRects[i]){ p.Collide(testRects[i]); } } and the actual Collide() code void gameObj::collide( gameObj collidingObject ){ printf("%f %f\n", this->colliderResult.width, this->colliderResult.height); if (this->colliderResult.width < this->colliderResult.height) { // collided on X if (this->getCollider().left < collidingObject.getCollider().left ) { this->move( -this->colliderResult.width , 0); }else { this->move( this->colliderResult.width, 0 ); } } if(this->colliderResult.width > this->colliderResult.height){ if (this->getCollider().top < collidingObject.getCollider().top ) { this->move( 0, -this->colliderResult.height); }else { this->move( 0, this->colliderResult.height ); } } } and the IsCollidingWith() code is bool gameObj::isCollidingWith( gameObj testObject ){ if (this->getCollider().intersects( testObject.getCollider(), this->colliderResult )) { return true; }else { return false; } } This works fine when there's only 1 Rect in the scene. However, when there's move than one Rect it causes issue when working out 2 collisions at once. Any idea how to deal with this correctly? I have uploaded a video to youtube to show my problem. The console on the far-right shows the width and height of the intersections. You can see on the console that it's trying to calculate 2 collisions at once, I think this is where the problem is being caused. The youtube video is at http://www.youtube.com/watch?v=fA2gflOMcAk also , this image also seems to illustrate the problem nicely. Can someone please help, I've been stuck on this all weekend!

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• 2D collision resolving

  - by Philippe Paré

  I've just worked out an AABB collision algorithm for my 2D game and I was very satisfied until I found out it only works properly with movements of 1 in X and 1 in Y... here it is: public bool Intersects(Rectanglef rectangle) { return this.Left < rectangle.Right && this.Right > rectangle.Left && this.Top < rectangle.Bottom && this.Bottom > rectangle.Top; } public bool IntersectsAny(params Rectanglef[] rectangles) { for (int i = 0; i < rectangles.Length; i++) { if (this.Left < rectangles[i].Right && this.Right > rectangles[i].Left && this.Top < rectangles[i].Bottom && this.Bottom > rectangles[i].Top) return true; } return false; } and here is how I use it in the update function of my player : public void Update(GameTime gameTime) { Rectanglef nextPosX = new Rectanglef(AABB.X, AABB.Y, AABB.Width, AABB.Height); Rectanglef nextPosY; if (Input.Key(Key.Left)) nextPosX.X--; if (Input.Key(Key.Right)) nextPosX.X++; bool xFree = !nextPosX.IntersectsAny(Boxes.ToArray()); if (xFree) nextPosY = new Rectanglef(nextPosX.X, nextPosX.Y, nextPosX.Width, nextPosX.Height); else nextPosY = new Rectanglef(AABB.X, AABB.Y, AABB.Width, AABB.Height); if (Input.Key(Key.Up)) nextPosY.Y--; if (Input.Key(Key.Down)) nextPosY.Y++; bool yFree = !nextPosY.IntersectsAny(Boxes.ToArray()); if (yFree) AABB = nextPosY; else if (xFree) AABB = nextPosX; } What I'm having trouble with, is a system where I can give float values to my movement and make it so there's a smooth acceleration. Do I have to retrieve the collision rectangle (the rectangle created by the other two colliding)? or should I do some sort of vector and go along this axis until I reach the collision? Thanks a lot!

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• Best Practice Method for Including Images in a DataGrid using MVVM

  - by Killercam

  All, I have a WPF DataGrid. This DataGrid shows files ready for compilation and should also show the progress of my compiler as it compiles the files. The format of the DataGrid is Image|File Path|State -----|---------|----- * |C:\AA\BB |Compiled & |F:PP\QQ |Failed > |G:HH\LL |Processing .... The problem is the image column (the *, &, and are for representation only). I have a ResourceDictionary that contains hundreds of vector images as Canvas objects: <ResourceDictionary xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"> <Canvas x:Key="appbar_acorn" Width="48" Height="48" Clip="F1 M 0,0L 48,0L 48,48L 0,48L 0,0"> <Path Width="22.3248" Height="25.8518" Canvas.Left="13.6757" Canvas.Top="11.4012" Stretch="Fill" Fill="{DynamicResource BlackBrush}" Data="F1 M 16.6309,18.6563C 17.1309,8.15625 29.8809,14.1563 29.8809,14.1563C 30.8809,11.1563 34.1308,11.4063 34.1308,11.4063C 33.5,12 34.6309,13.1563 34.6309,13.1563C 32.1309,13.1562 31.1309,14.9062 31.1309,14.9062C 41.1309,23.9062 32.6309,27.9063 32.6309,27.9062C 24.6309,24.9063 21.1309,22.1562 16.6309,18.6563 Z M 16.6309,19.9063C 21.6309,24.1563 25.1309,26.1562 31.6309,28.6562C 31.6309,28.6562 26.3809,39.1562 18.3809,36.1563C 18.3809,36.1563 18,38 16.3809,36.9063C 15,36 16.3809,34.9063 16.3809,34.9063C 16.3809,34.9063 10.1309,30.9062 16.6309,19.9063 Z "/> </Canvas> </ResourceDictionary> Now, I want to be able to include these in my image column and change them at run-time. I was going to attempt to do this by setting up a property in my View Model that was of type Image and binding this to my View via: <DataGrid.Columns> <DataGridTemplateColumn Header="" Width="SizeToCells" IsReadOnly="True"> <DataGridTemplateColumn.CellTemplate> <DataTemplate> <Image Source="{Binding Canvas}"/> </DataTemplate> </DataGridTemplateColumn.CellTemplate> </DataGridTemplateColumn> </DataGrid.Columns> Where in the View Model I have the appropriate property. Now, I was told this is not 'pure' MVVM. I don't fully accept this, but I want to know if there is a better way of doing this. Say, binding to an enum and using a converter to get the image? Any advice would be appreciated.

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• How should game objects be aware of each other?

  - by Jefffrey

  I find it hard to find a way to organize game objects so that they are polymorphic but at the same time not polymorphic. Here's an example: assuming that we want all our objects to update() and draw(). In order to do that we need to define a base class GameObject which have those two virtual pure methods and let polymorphism kicks in: class World { private: std::vector<GameObject*> objects; public: // ... update() { for (auto& o : objects) o->update(); for (auto& o : objects) o->draw(window); } }; The update method is supposed to take care of whatever state the specific class object needs to update. The fact is that each objects needs to know about the world around them. For example: A mine needs to know if someone is colliding with it A soldier should know if another team's soldier is in proximity A zombie should know where the closest brain, within a radius, is For passive interactions (like the first one) I was thinking that the collision detection could delegate what to do in specific cases of collisions to the object itself with a on_collide(GameObject*). Most of the the other informations (like the other two examples) could just be queried by the game world passed to the update method. Now the world does not distinguish objects based on their type (it stores all object in a single polymorphic container), so what in fact it will return with an ideal world.entities_in(center, radius) is a container of GameObject*. But of course the soldier does not want to attack other soldiers from his team and a zombie doesn't case about other zombies. So we need to distinguish the behavior. A solution could be the following: void TeamASoldier::update(const World& world) { auto list = world.entities_in(position, eye_sight); for (const auto& e : list) if (auto enemy = dynamic_cast<TeamBSoldier*>(e)) // shoot towards enemy } void Zombie::update(const World& world) { auto list = world.entities_in(position, eye_sight); for (const auto& e : list) if (auto enemy = dynamic_cast<Human*>(e)) // go and eat brain } but of course the number of dynamic_cast<> per frame could be horribly high, and we all know how slow dynamic_cast can be. The same problem also applies to the on_collide(GameObject*) delegate that we discussed earlier. So what it the ideal way to organize the code so that objects can be aware of other objects and be able to ignore them or take actions based on their type?

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• How to snap a 2D Quad to the mouse cursor using OpenGL 3.0?

  - by NoobScratcher

  I've been having issues trying to snap a 2D Quad to the mouse cursor position I'm able : 1.) To get values into posX, posY, posZ 2.) Translate with the values from those 3 variables But the quad positioning I'm not able to do correctly in such a way that the 2D Quad is near the mouse cursor using those values from those 3 variables eg."posX, posY, posZ" I need the mouse cursor in the center of the 2D Quad. I'm hoping someone can help me achieve this. I've tried searching around with no avail. Heres the function that is ment to do the snapping but instead creates weird flicker or shows nothing at all only the 3d models show up : void display() { glClearColor(0.0,0.0,0.0,1.0); glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT); for(std::vector<GLuint>::iterator I = cube.begin(); I != cube.end(); ++I) { glCallList(*I); } if(DrawArea == true) { glReadPixels(winX, winY, 1, 1, GL_DEPTH_COMPONENT, GL_FLOAT, &winZ); cerr << winZ << endl; glGetDoublev(GL_MODELVIEW_MATRIX, modelview); glGetDoublev(GL_PROJECTION_MATRIX, projection); glGetIntegerv(GL_VIEWPORT, viewport); gluUnProject(winX, winY, winZ , modelview, projection, viewport, &posX, &posY, & posZ); glBindTexture(GL_TEXTURE_2D, DrawAreaTexture); glPixelStorei(GL_UNPACK_ALIGNMENT, 1); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST); glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_DECAL); glTexImage2D (GL_TEXTURE_2D, 0, GL_RGB, DrawAreaSurface->w, DrawAreaSurface->h, 0, GL_RGBA, GL_UNSIGNED_BYTE, DrawAreaSurface->pixels); glEnable(GL_TEXTURE_2D); glBindTexture(GL_TEXTURE_2D, DrawAreaTexture); glTranslatef(posX , posY, posZ); glBegin(GL_QUADS); glTexCoord2f (0.0, 0.0); glVertex3f(0.5, 0.5, 0); glTexCoord2f (1.0, 0.0); glVertex3f(0, 0.5, 0); glTexCoord2f (1.0, 1.0); glVertex3f(0, 0, 0); glTexCoord2f (0.0, 1.0); glVertex3f(0.5, 0, 0); glEnd(); } SwapBuffers(hDC); } I'm using : OpenGL 3.0 WIN32 API C++ GLSL if you really want the full source here it is - http://pastebin.com/1Ncm9HNf , Its pretty messy.

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• Getting current time in milliseconds

  - by user90293423

  How to get the current time in milliseconds? I'm working on a hacking simulation game and when ever someone connects to another computer/NPC, a login screen popups with a button on the side called BruteForce. When BruteForce is clicked, what i want the program to do is, calculate how many seconds cracking the password is going to take based on the player's CPU speed but that's the easy part. The hard part is i want to enter a character in the password's box every X milliseconds based on a TimeToCrack divided by PasswordLength formula. But since i don't know how to find how many milliseconds have elapsed since the second has passed, the program waits until the CurrentTime is higher than the TimeBeforeTheLoopStarted + HowLongItTakesToTypeaCharacter which is always going to be a second. How would you handle my problems? I've commented the game breaking part. std::vector<QString> hardware = user.getHardware(); QString CPU = hardware[0]; unsigned short Speed = 0; if(CPU == "OMG SingleCore 1.8GHZ"){ Speed = 2; } const short passwordLength = password.length(); /* It's equal to 16 */ int Time = passwordLength / Speed; double TypeSpeed = Time / passwordLength; time_t t = time(0); struct tm * now = localtime(&t); unsigned short EndTime = (now->tm_sec + Time) % 60; unsigned short CurrentTime = 0; short i = passwordLength - 1; do{ t = time(0); now = localtime(&t); CurrentTime = now->tm_sec; do{ t = time(0); now = localtime(&t); }while(now->tm_sec < CurrentTime + TypeSpeed); /* Highly flawed */ /* Do this while your integer value is under this double value */ QString tempPass = password; tempPass.chop(i); ui->lineEdit_2->setText(tempPass); i--; }while(CurrentTime != EndTime);

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• That Escalated Quickly

  - by Jesse Taber

  Originally posted on: http://geekswithblogs.net/GruffCode/archive/2014/05/17/that-escalated-quickly.aspxI have been working remotely out of my home for over 4 years now. All of my coworkers during that time have also worked remotely. Lots of folks have written about the challenges inherent in facilitating communication on remote teams and strategies for overcoming them. A popular theme around this topic is the notion of “escalating communication”. In this context “escalating” means taking a conversation from one mode of communication to a different, higher fidelity mode of communication. Here are the five modes of communication I use at work in order of increasing fidelity: Email – This is the “lowest fidelity” mode of communication that I use. I usually only check it a few times a day (and I’m trying to check it even less frequently than that) and I only keep items in my inbox if they represent an item I need to take action on that I haven’t tracked anywhere else. Forums / Message boards – Being a developer, I’ve gotten into the habit of having other people look over my code before it becomes part of the product I’m working on. These code reviews often happen in “real time” via screen sharing, but I also always have someone else give all of the changes another look using pull requests. A pull request takes my code and lets someone else see the changes I’ve made side-by-side with the existing code so they can see if I did anything dumb. Pull requests can facilitate a conversation about the code changes in an online-forum like style. Some teams I’ve worked on also liked using tools like Trello or Google Groups to have on-going conversations about a topic or task that was being worked on. Chat & Instant Messaging  - Chat and instant messaging are the real workhorses for communication on the remote teams I’ve been a part of. I know some teams that are co-located that also use it pretty extensively for quick messages that don’t warrant walking across the office to talk with someone but reqire more immediacy than an e-mail. For the purposes of this post I think it’s important to note that the terms “chat” and “instant messaging” might insinuate that the conversation is happening in real time, but that’s not always true. Modern chat and IM applications maintain a searchable history so people can easily see what might have been discussed while they were away from their computers. Voice, Video and Screen sharing – Everyone’s got a camera and microphone on their computers now, and there are an abundance of services that will let you use them to talk to other people who have cameras and microphones on their computers. I’m including screen sharing here as well because, in my experience, these discussions typically involve one or more people showing the other participants something that’s happening on their screen. Obviously, this mode of communication is much higher-fidelity than any of the ones listed above. Scheduled meetings are typically conducted using this mode of communication. In Person – No matter how great communication tools become, there’s no substitute for meeting with someone face-to-face. However, opportunities for this kind of communcation are few and far between when you work on a remote team. When a conversation gets escalated that usually means it moves up one or more positions on this list. A lot of people advocate jumping to #4 sooner than later. Like them, I used to believe that, if it was possible, organizing a call with voice and video was automatically better than any kind of text-based communication could be. Lately, however, I’m becoming less convinced that escalating is always the right move. Working Asynchronously Last year I attended a talk at our local code camp given by Drew Miller. Drew works at GitHub and was talking about how they use GitHub internally. Many of the folks at GitHub work remotely, so communication was one of the main themes in Drew’s talk. During the talk Drew used the phrase, “asynchronous communication” to describe their use of chat and pull request comments. That phrase stuck in my head because I hadn’t heard it before but I think it perfectly describes the way in which remote teams often need to communicate. You don’t always know when your co-workers are at their computers or what hours (if any) they are working that day. In order to work this way you need to assume that the person you’re talking to might not respond right away. You can’t always afford to wait until everyone required is online and available to join a voice call, so you need to use text-based, persistent forms of communication so that people can receive and respond to messages when they are available. Going back to my list from the beginning of this post for a second, I characterize items #1-3 as being “asynchronous” modes of communication while we could call items #4 and #5 “synchronous”. When communication gets escalated it’s almost always moving from an asynchronous mode of communication to a synchronous one. Now, to the point of this post: I’ve become increasingly reluctant to escalate from asynchronous to synchronous communication for two primary reasons: 1 – You can often find a higher fidelity way to convey your message without holding a synchronous conversation 2 - Asynchronous modes of communication are (usually) persistent and searchable. You Don’t Have to Broadcast Live Let’s start with the first reason I’ve listed. A lot of times you feel like you need to escalate to synchronous communication because you’re having difficulty describing something that you’re seeing in words. You want to provide the people you’re conversing with some audio-visual aids to help them understand the point that you’re trying to make and you think that getting on Skype and sharing your screen with them is the best way to do that. Firing up a screen sharing session does work well, but you can usually accomplish the same thing in an asynchronous manner. For example, you could take a screenshot and annotate it with some text and drawings to illustrate what it is you’re seeing. If a screenshot won’t work, taking a short screen recording while your narrate over it and posting the video to your forum or chat system along with a text-based description of what’s in the recording that can be searched for later can be a great way to effectively communicate with your team asynchronously. I Said What?!? Now for the second reason I listed: most asynchronous modes of communication provide a transcript of what was said and what decisions might have been made during the conversation. There have been many occasions where I’ve used the search feature of my team’s chat application to find a conversation that happened several weeks or months ago to remember what was decided. Unfortunately, I think the benefits associated with the persistence of communicating asynchronously often get overlooked when people decide to escalate to a in-person meeting or voice/video call. I’m becoming much more reluctant to suggest a voice or video call if I suspect that it might lead to codifying some kind of design decision because everyone involved is going to hang up the call and immediately forget what was decided. I recognize that you can record and archive these types of interactions, but without being able to search them the recordings aren’t terribly useful. When and How To Escalate I don’t mean to imply that communicating via voice/video or in person is never a good idea. I probably jump on a Skype call with a co-worker at least once a day to quickly hash something out or show them a bit of code that I’m working on. Also, meeting in person periodically is really important for remote teams. There’s no way around the fact that sometimes it’s easier to jump on a call and show someone my screen so they can see what I’m seeing. So when is it right to escalate? I think the simplest way to answer that is when the communication starts to feel painful. Everyone’s tolerance for that pain is different, but I think you need to let it hurt a little bit before jumping to synchronous communication. When you do escalate from asynchronous to synchronous communication, there are a couple of things you can do to maximize the effectiveness of the communication: Takes notes – This is huge and yet I’ve found that a lot of teams don’t do this. If you’re holding a meeting with  > 2 people you should have someone taking notes. Taking notes while participating in a meeting can be difficult but there are a few strategies to deal with this challenge that probably deserve a short post of their own. After the meeting, make sure the notes are posted to a place where all concerned parties (including those that might not have attended the meeting) can review and search them. Persist decisions made ASAP – If any decisions were made during the meeting, persist those decisions to a searchable medium as soon as possible following the conversation. All the teams I’ve worked on used a web-based system for tracking the on-going work and a backlog of work to be done in the future. I always try to make sure that all of the cards/stories/tasks/whatever in these systems always reflect the latest decisions that were made as the work was being planned and executed. If held a quick call with your team lead and decided that it wasn’t worth the effort to build real-time validation into that new UI you were working on, go and codify that decision in the story associated with that work immediately after you hang up. Even better, write it up in the story while you are both still on the phone. That way when the folks from your QA team pick up the story to test a few days later they’ll know why the real-time validation isn’t there without having to invoke yet another conversation about the work. Communicating Well is Hard At this point you might be thinking that communicating asynchronously is more difficult than having a live conversation. You’re right: it is more difficult. In order to communicate effectively this way you need to very carefully think about the message that you’re trying to convey and craft it in a way that’s easy for your audience to understand. This is almost always harder than just talking through a problem in real time with someone; this is why escalating communication is such a popular idea. Why wouldn’t we want to do the thing that’s easier? Easier isn’t always better. If you and your team can get in the habit of communicating effectively in an asynchronous manner you’ll find that, over time, all of your communications get less painful because you don’t need to re-iterate previously made points over and over again. If you communicate right the first time, you often don’t need to rehash old conversations because you can go back and find the decisions that were made laid out in plain language. You’ll also find that you get better at doing things like writing useful comments in your code, creating written documentation about how the feature that you just built works, or persuading your team to do things in a certain way.

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• SSH public key authentication -- always require users to generate their own keypair?

  - by schinazi

  I was working with a partner today that I needed to upload files to my server using scp. I have passwords turned off in the server's SSH configuration, so I wanted them to use public key authentication. I generated the keypair for them on the server and gave them the private key and put the public key in the appropriate authorized_keys file. After a bunch of problems with them setting up their job, they finally got a more experienced sysadmin involved on their end, and he scolded me for handling the key generation this way. He said that by giving them a private key generated on my system, I had enabled them to do a brute-force attack against other keys generated on the same server. I even asked him "so if I have an account on a server, and I can log in with a password but I want to automate something and I generate a keypair on that system, does that then give me an attack vector for brute forcing other users' keys?" and he said yes. I've never heard of this, is it true? Can anyone point me to a discussion of this attack? Thanks in advance.

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• Windows file locks allowing multiple users to write to open file over network

  - by JPbuntu

  I have 6 windows computers (xp,vista,7) that need to access a samba share (Ubuntu 12.04). I am trying to make it so only one client can open a file at a given time. I thought this was pretty standard behavior of file locks, but I can't get it to work. The way it is right now a file can be open by two users, and changed and saved by either one of them. The last file saved overwrites what ever changes the other user made. At first I thought this was a Samba configuration problem, but I get this behavior even between two windows machines. So far I have only tested: Windows Xp Windows Vista Windows XP Samba << Windows Vista and both give the same behavior. When I tested the Samba configuration, I had set strict locking = yes and get errors logged like this: close_remove_share_mode: Could not get share mode lock for file _prod/part_number_list_COPY.xlsx Eventually all of the files are going to be moved onto the Samba share, so that is the configuration I am most concerned about fixing. Any ideas? Thanks in advance. EDIT: I tested an excel file again, and it is now working properly in both above mentioned cases, I am also no longer getting the above mentioned error. I don't know what happened, perhaps a restart fixed it? (also works with strict locking = no) Although I still need to find a solution for the CAD/CAM files we use, the software is Vector and it does not seem to be using file locks. Is there any software that I can use to manage these files, so two people can't open/edit them at a time? Maybe a windows application that forces file locks? Or a dirt simple version control system? (the only ones I have seen at are too complicated for our needs).

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• Going Paperless

  - by Jesse

  One year ago I came to work for a company where the entire development team is 100% “remote”; we’re spread over 3 time zones and each of us works from home. This seems to be an increasingly popular way for people to work and there are many articles and blog posts out there enumerating the advantages and disadvantages of working this way. I had read a lot about telecommuting before accepting this job and felt as if I had a pretty decent idea of what I was getting into, but I’ve encountered a few things over the past year that I did not expect. Among the most surprising by-products of working from home for me has been a dramatic reduction in the amount of paper that I use on a weekly basis. Hoarding In The Workplace Prior to my current telecommute job I worked in what most would consider pretty traditional office environments. I sat in cubicles furnished with an enormous plastic(ish) modular desks, had a mediocre (at best) PC workstation, and had ready access to a seemingly endless supply of legal pads, pens, staplers and paper clips. The ready access to paper, countless conference room meetings, and abundance of available surface area on my desk and in drawers created a perfect storm for wasting paper. I brought a pad of paper with me to every meeting I ever attended, scrawled some brief notes, and then tore that sheet off to keep next to my keyboard to follow up on any needed action items. Once my immediate need for the notes was fulfilled, that sheet would get shuffled off into a corner of my desk or filed away in a drawer “just in case”. I would guess that for all of the notes that I ever filed away, I might have actually had to dig up and refer to 2% of them (and that’s probably being very generous). That said, on those rare occasions that I did have to dig something up from old notes, it was usually pretty important and I ended up being very glad that I saved them. It was only when I would leave a job or move desks that I would finally gather all those notes together and take them to shredding bin to be disposed of. When I left my last job the amount of paper I had accumulated over my three years there was absurd, and I knew coworkers who had substance-abuse caliber paper wasting addictions that made my bad habit look like nail-biting in comparison. A Product Of My Environment I always hated using all of this paper, but simply couldn’t bring myself to stop. It would look bad if I showed up to an important conference room meeting without a pad of paper. What if someone said something profound! Plus, everyone else always brought paper with them. If you saw someone walking down the hallway with a pad of paper in hand you knew they must be on their way to a conference room meeting. Some people even had fancy looking portfolio notebook sheaths that gave their legal pads all the prestige of a briefcase. No one ever worried about running out of fresh paper because there was an endless supply, and there certainly was no shortage of places to store and file used paper. In short, the traditional office was setup for using tons and tons of paper; it’s baked into the culture there. For that reason, it didn’t take long for me to kick the paper habit once I started working from home. In my home office, desk and drawer space are at a premium. I don’t have the budget (or the tolerance) for huge modular office furniture in my spare bedroom. I also no longer have access to a bottomless pit of office supplies stock piled in cabinets and closets. If I want to use some paper, I have to go out and buy it. Finally (and most importantly), all of the meetings that I have to attend these days are “virtual”. We use instant messaging, VOIP, video conferencing, and e-mail to communicate with each other. All I need to take notes during a meeting is my computer, which I happen to be sitting right in front of all day. I don’t have any hard numbers for this, but my gut feeling is that I actually take a lot more notes now than I ever did when I worked in an office. The big difference is I don’t have to use any paper to do so. This makes it far easier to keep important information safe and organized. The Right Tool For The Job When I first started working from home I tried to find a single application that would fill the gap left by the pen and paper that I always had at my desk when I worked in an office. Well, there are no silver bullets and I’ve evolved my approach over time to try and find the best tool for the job at hand. Here’s a quick summary of how I take notes and keep everything organized. Notepad++ – This is the first application I turn to when I feel like there’s some bit of information that I need to write down and save. I use Launchy, so opening Notepad++ and creating a new file only takes a few keystrokes. If I find that the information I’m trying to get down requires a more sophisticated application I escalate as needed. The Desktop – By default, I save every file or other bit of information to the desktop. Anyone who has ever had to fix their parents computer before knows that this is a dangerous game (any file my mother has ever worked on is saved directly to the desktop and rarely moves anywhere else). I agree that storing things on the desktop isn’t a great long term approach to keeping organized, which is why I treat my desktop a bit like my e-mail inbox. I strive to keep both empty (or as close to empty as I possibly can). If something is on my desktop, it means that it’s something relevant to a task or project that I’m currently working on. About once a week I take things that I’m not longer working on and put them into my ‘Notes’ folder. The ‘Notes’ Folder – As I work on a task, I tend to accumulate multiple files associated with that task. For example, I might have a bit of SQL that I’m working on to gather data for a new report, a quick C# method that I came up with but am not yet ready to commit to source control, a bulleted list of to-do items in a .txt file, etc. If the desktop starts to get too cluttered, I create a new sub-folder in my ‘Notes’ folder. Each sub-folder’s name is the current date followed by a brief description of the task or project. Then all files related to that task or project go into that sub folder. By using the date as the first part of the folder name, these folders are automatically sorted in reverse chronological order. This means that things I worked on recently will generally be near the top of the list. Using the built-in Windows search functionality I now have a pretty quick and easy way to try and find something that I worked on a week ago or six months ago. Dropbox – Dropbox is a free service that lets you store up to 2GB of files “in the cloud” and have those files synced to all of the different computers that you use. My ‘Notes’ folder lives in Dropbox, meaning that it’s contents are constantly backed up and are always available to me regardless of which computer I’m using. They also have a pretty decent iPhone application that lets you browse and view all of the files that you have stored there. The free 2GB edition is probably enough for just storing notes, but I also pay $99/year for the 50GB storage upgrade and keep all of my music, e-books, pictures, and documents in Dropbox. It’s a fantastic service and I highly recommend it. Evernote – I use Evernote mostly to organize information that I access on a fairly regular basis. For example, my Evernote account has a running grocery shopping list, recipes that my wife and I use a lot, and contact information for people I contact infrequently enough that I don’t want to keep them in my phone. I know some people that keep nearly everything in Evernote, but there’s something about it that I find a bit clunky, so I tend to use it sparingly. Google Tasks – One of my biggest paper wasting habits was keeping a running task-list next to my computer at work. Every morning I would sit down, look at my task list, cross off what was done and add new tasks that I thought of during my morning commute. This usually resulted in having to re-copy the task list onto a fresh sheet of paper when I was done. I still keep a running task list at my desk, but I’ve started using Google Tasks instead. This is a dead-simple web-based application for quickly adding, deleting, and organizing tasks in a simple checklist style. You can quickly move tasks up and down on the list (which I use for prioritizing), and even create sub-tasks for breaking down larger tasks into smaller pieces. Balsamiq Mockups – This is a simple and lightweight tool for creating drawings of user interfaces. It’s great for sketching out a new feature, brainstorm the layout of a interface, or even draw up a quick sequence diagram. I’m terrible at drawing, so Balsamiq Mockups not only lets me create sketches that other people can actually understand, but it’s also handy because you can upload a sketch to a common location for other team members to access. I can honestly say that using these tools (and having limited resources at home) have lead me to cut my paper usage down to virtually none. If I ever were to return to a traditional office workplace (hopefully never!) I’d try to employ as many of these applications and techniques as I could to keep paper usage low. I feel far less cluttered and far better organized now.

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• SQL Cruise Alaska 2011

  - by Grant Fritchey

  I had the extreme good fortune to get sent on the last SQL Cruise to Alaska. I love my job. In case you don't what this is, SQL Cruise is a trip on a cruise ship during which you get to attend classes while on the boat, learning all about SQL Server and related topics as well as network with the instructors and the other Cruisers. Frankly, it's amazing. Classes ran from Monday, 5/30, to Saturday, 6/4. The networking was constant, between classes, at night on cruise ship, out on excursions in Alaskan rainforests and while snorkeling in ocean waters. Here's a run down of the experience from my point of view. Because I couldn't travel out 2 days early, I missed the BBQ that occurred the day before the cruise when many of the Cruisers received their swag bags. Some of that swag came from Red Gate. I researched what was useful on a cruise like this and purchased small flashlights and binoculars for all the Cruisers. The flashlights were because, depending on your cabin, ships can be very dark. The binoculars were so that the cruisers could watch all the beautiful landscape as it flowed by. I would have liked to have been there when the bags were opened, but I heard from several people that they appreciated the gifts. Cruisers "In" the hot tub. Pictured: Marjory Woody, Michele Grondin, Kyle Brandt, Grant Fritchey, John Halunen Sunday I went to board the ship with my wife. We had a bit of an adventure because I messed up our documents. It all worked out and we got on board to meet up at the back of the boat at one of the outdoor bars with the other Cruisers, thanks to tweets letting everyone know where to go. That was the end of electronic coordination on the trip (connectivity in Alaska was horrible for everyone except AT&T). The Cruisers were a great bunch of people and it was a real honor to meet them and get to spend time with them. After everyone settled into their cabins, our very first activity was a contest, sponsored by Red Gate. The Cruisers, in an effort to get to know each other and the ship, were required to go all over taking various photographs, some of them hilarious. The winning team of three would all win prizes. Some of the significant others helped out and I tagged along with a team that tied for first but lost the coin toss. The winning team consisted of Christina Leo (blog|twitter), Ryan Malcom (twitter), Neil Hambly (blog|twitter). They then had to do math and identify the cabin with the lowest prime number, oh, and get a picture of it and be the first to get back up to the bar where we were waiting. Christina came in first and very happily carried home an Ipad2. Ryan won a 1TB portable hard drive and Neil won a wireless mouse (picture below, note my special SQL Server Central Friday Shirt. Thanks Steve (blog|twitter)). Winners: Christina Leo, Neil Hambly, Ryan Malcolm. Just Lucky: Grant Fritchey Monday morning classes started. Buck Woody (blog|twitter) was a special guest speaker on this cruise. His theme was "Three C's on the High Seas: Career, Communication and Cloud." The first session was all on Career. I'm not going to type out all my notes from the session, but let's just say, if you get the chance to hear Buck talk about how to manage your career, I suggest you attend. I have a ton of blog posts that I'll be putting together over the next several months (yes, months) both here and over on ScaryDBA. I also have a bunch of work I'm going to be doing to get my career performance bumped up a notch or two (and let's face it, that won't be easy). Later on Monday, Tim Ford (blog|twitter) did a session on DMOs. Specifically the session was on Tim's Period Table of DMOs that he has put together, and how to use some of the more interesting DMOs in your day to day job. It was a great session, packed with good information. Next, Brent Ozar (blog|twitter) did a session on how to monitor and guide SAN configuration for the DBA that doesn't have access to the SAN. That was some seriously useful information. Tuesday morning we only had a single class. Kendra Little (blog|twitter) taught us all about "No Lock for Yes Fun".  It was all about the different transaction isolation levels and how they work. There is so often confusion in this area and Kendra does a great job in clarifying the information. Also, she tosses in her excellent drawings to liven up the presentation. Then it was excursion time in Juneau. My wife and I, along with several other Cruisers, took a hike up around the Mendenhall Glacier. It was absolutely beautiful weather and walking through the Alaskan rain forest was a treat. Our guide, Jason, was a great guy and it was a good day of hiking. Wednesday was an all day excursion in Skagway. My wife and I took the "Ghost and Good Time Girls" walking tour that ended up at a bar that used to be a brothel, the Red Onion. It was a great history of the town. We went back out and hit a few museums and exhibits. We also hiked up the side of the mountain to see the Dewey Lake and some great views of the town. Finally we hiked out to the far side of town to see the Gold Rush cemetery. Hiking done we went back to the boat and had a quiet dinner on our own. Thursday we cruised through Glacier Bay and saw at least four different glaciers including sitting next to the Marjory Glacier for  about an hour. It was amazing. Then it got better. We went into class with Buck again, this time to talk about Communication. Again, I've got pages of notes that I'm going to be referring back to for some time to come. This was an excellent opportunity to learn. Snorkelers: Nicole Bertrand, Aaron Bertrand, Grant Fritchey, Neil Hambly, Christina Leo, John Robel, Yanni Robel, Tim Ford Friday we pulled into Ketchikan. A bunch of us went snorkeling. Yes, snorkeling. Yes, in Alaska. Yes, snorkeling in the ocean in Alaska. It was fantastic. They had us put on 7mm thick wet suits (an adventure all by itself) so it was basically warm the entire time we were in the water (except for the occasional squirt of cold water down my back). Before we got in the water a bald eagle flew up and landed about 15 feet in front of us, which was just an incredible event. Then our guide pointed out about 14 other eagles in the area, hanging out in the trees. Wow! The water was pretty clear and there was a ton of things to see. That was absolutely a blast. Back on the boat I presented a session called Execution Plans: The Deep Dive (note the nautical theme). It seemed to go over well and I had several good questions come out of the session that will lead to new blog posts. After I presented, it was Aaron Bertrand's (blog|twitter) turn. He did a session on "What's New in Denali" that provided a lot of great information. He was able to incorporate new things straight out of Tech-Ed, so this was expanded beyond his usual presentation. The man really knows what he's talking about and communicates it well. Saturday we were travelling so there was time for a bunch of classes. Jeremiah Peschka (blog|twitter) did a great overview of some of the NoSQL databases and what they should be used for. The session was called "The Database is Dead" but it was really about how there are specific uses for these databases that SQL Server doesn't fill, but also that these databases can't replace SQL Server in other areas. Again, good material. Brent Ozar presented again with a session on Defensive Indexing. It was an overview of how indexes work and a deep dive into how to apply them appropriately in your databases to better support access. A good session, as you would expect. Then we pulled into Victoria, BC, in Canada and had a nice dinner with several of the Cruisers, including Denny Cherry (blog|twitter). After that it was back to Seattle on Sunday. By the way, the Science Fiction Museum in Seattle isn't a Science Fiction Museum any more. I was very disappointed to discover this. Overall, it was a great experience. I'm extremely appreciative of Red Gate for sending me and for Tim, Brent, Kendra and Jeremiah for having me. The other Cruisers were all amazing people and it was an honor & privilege to meet them and spend time with them. While this was a seriously fun time, it was also a very serious training opportunity with solid information coming from seasoned industry pros.

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• I/O APIC on Virtualbox

  - by RidDeBakTiYar

  I'm trying to use the PIT to do APIC timer calibration, and I want to use the PIT through I/O APIC instead of PIC. On Bochs I get interrupts from the PIT at the asked frequency from the I/O APIC, while on Virtualbox I can't receive a single interrupt. It must be an I/O APIC configuration problem because as I unmask the first PIC entry, the IRQ fires. However that's not what I want. Can you imagine any possible condition that wouldn't make Virtualbox fire the IRQ? I'm not assuming single I/O APIC configuration (even though Virtualbox has only 1). I'm not assuming identity mappings between ISA IRQs and I/O APIC GSIs (using ACPI MADT table to get I/O APIC base address and Int override). I'm setting the Trigger Mode and Polarity bits correctly (on Virtualbox they are set as '00 - default' which means edge high right?). I'm putting the BSP APIC ID into the Destination field (using Physical destination) and vector 0x20. Being the BSP APIC ID 0 on Virtualbox, it ends up with 0x0000000000000020 written to the IOREDTBL. And, just in case I'm getting the wrong values from the Interrupt Override descriptor, I'm setting this value to all the IOREDTBL entries (I know this is very very bad, and it wont be kept as I understand what's going on). The only thing I didn't check out is Local APIC configuration. Actually I'm not writing any value to the BSP LAPIC. Just reading the APIC ID and using it to boot APs through IPIs. And obviously I'm setting bit 11 in the IA32_APIC_BASE MSR to enable the LAPIC. Any ideas? Thanks in advance.

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