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• Billboarding + aligning with velocity direction

  - by roxlu

  I'm working on a particle system where I'm orientating the billboard using the inverted orientation matrix of my camera. This works quite well and my quad are rotated correctly towards the camera. But, now I want to to rotate the quads in such a way that they point towards the direction they are going to. In 2D this can be done by normalizing the velocity vector and using that vector for a rotation around the Z-axis (where vel.x = cos(a) and vel.y = sin(a)). But how does this work in 3D? Thanks roxlu

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• "Marching cubes" voxel terrain - triplanar texturing with depth?

  - by Dan the Man

  I am currently working on a voxel terrain that uses the marching cubes algorithm for polygonizing the scalar field of voxels. I am using a triplanar texturing shader for texturing. say I have a grass texture set to the Y axis and a dirt texture for both the X and Z axes. Now, when my player digs downwards, it still appears as grass. How would I make it to appear as dirt? I have been thinking about this for a while, and the only thing I can think of to make this effect, would be to mark vertices that have been dug with a certain vertex color. When it has that vertex color, the shader would apply that dirt texture to the vertices marked. Is there a better method?

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• Factors to consider when building an algorithm for gun recoil

  - by Nate Bross

  What would be a good algorithm for calculating the recoil of a shooting guns cross-hairs? What I've got now, is something like this: Define min/max recoil based on weapon size Generate random number of "delta" movement Apply random value to X, Y, or both of cross-hairs (only "up" on the Y axis) Multiply new delta based on time from the previous shot (more recoil for full-auto) What I'm worried about is that this feels rather predicable, what other factors should one take into account when building recoil? While I'd like it to be somewhat predictable, I'd also like to keep players on their toes. I'm thinking about increasing the min/max recoil values by a large amount (relatively) and adding a weighting, so large recoils will be more rare -- it seems like a lot of effort to go into something I felt would be simple. Maybe this is just something that needs to be fine-tuned with additional playtesting, and more playtesters? I think that it's important to note, that the recoil will be a large part of the game, and is a key factor in the game being fun/challenging or not.

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• as3 3D camera lookat

  - by Johannes Jensen

  I'm making a 3D camera scene in Flash, draw using drawTriangles() and rotated and translated using a Matrix3D. I've got the camera to look after a specific point, but only on the Y-axis, using the x and z coordinates, here is my code so far: var dx:Number = camera.x - lookAt.x; var dy:Number = camera.y - lookAt.y; var dz:Number = camera.z - lookAt.z; camera.rotationY = Math.atan2(dz, dx) * (180 / Math.PI) + 270; so no matter the x or z position, the point is always on the mid of the screen, IF and only if y matches with the camera. So what I need is to calculate the rotationX (which are measured in degrees not radians), and I was wondering how I would do this?

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• How to flip a BC6/BC7 texture?

  - by postgoodism

  I have some code to load DDS image files into OpenGL textures, and I'd like to extend it to support the BC6 and BC7 compressed formats introduced in D3D11. Since DirectX and OpenGL disagree about whether a texture's origin is in the upper-left or lower-left corner, my DDS loader flips each image's pixels along the Y axis before passing the pixels to OpenGL. Flipping compressed textures presents an additional wrinkle: in addition to flipping each row of 4x4-pixel blocks, you also need to flip the pixels within each block. I found code here to flip BC1/BC2/BC3 blocks, and from the block diagrams on MSDN it was easy to adapt the BC3-flipping code to handle BC4 and BC5. The BC6 and BC7 formats look significantly more intimidating, though. Is there a similar bit-twiddling trick to flip these formats, or would I have to fully decompress and recompress each block?

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• Tips for adapting Date table to Power View forecasting #powerview #powerbi

  - by Marco Russo (SQLBI)

  During the keynote of the PASS Business Analytics Conference, Amir Netz presented the new forecasting capabilities in Power View for Office 365. I immediately tried the new feature (which was immediately available, a welcome surprise in a Microsoft announcement for a new release) and I had several issues trying to use existing data models. The forecasting has a few requirements that are not compatible with the “best practices” commonly used for a calendar table until this announcement. For example, if you have a Year-Month-Day hierarchy and you want to display a line chart aggregating data at the month level, you use a column containing month and year as a string (e.g. May 2014) sorted by a numeric column (such as 201405). Such a column cannot be used in the x-axis of a line chart for forecasting, because you need a date or numeric column. There are also other requirements and I wrote the article Prepare Data for Power View Forecasting in Power BI on SQLBI, describing how to create columns that can be used with the new forecasting capabilities in Power View for Office 365.

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• Problem using glm::lookat

  - by omikun

  I am trying to rotate a sprite so it is always facing a 3D camera. Object GLfloat vertexData[] = { // X Y Z U V 0.0f, 0.8f, 0.0f, 0.5f, 1.0f, -0.8f,-0.8f, 0.0f, 0.0f, 0.0f, 0.8f,-0.8f, 0.0f, 1.0f, 0.0f, }; Per frame transform glm::mat4 newTransform = glm::lookAt(glm::vec3(0), gCamera.position(), gCamera.up()); shaders->setUniform("camera", gCamera.matrix()); shaders->setUniform("model", newTransform); In the vertex shader: gl_Position = camera * model * vec4(vert, 1); The object will track the camera if I move the camera up or down, but if I move the camera left/right (spin the camera around the object's y axis), it will rotate in the other direction so I end up seeing its front twice and its back twice as I rotate around it 360. If I use -gCamera.up() instead, it would track the camera side to side, but spin the opposite direction when I move the camera up/down. What am I doing wrong?

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• How to position a sprite in a 2D animation skeleton?

  - by Paul Manta

  Given two joints that define a bone, I would like to know how to decide where, between those two joints, I should draw the sprite. This should be a fairly simple thing to solve, but there is one thing that I am not sure about. After I've determined the rotation of the sprite (which is the absolute angle the joints form with the x-axis), I also need to determine the origin point from where I need to start drawing the transformed image. So how should I position the sprite between the two joints? Should I make the center of the image be the midpoint between the two joints, or should I make one the of the joints be the origin? Do these things matter that much (could the wrong positioning make the sprite move oddly during the animation)?

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• How can I get six Xbox controllers to provide input to an HTML5 game?

  - by Daniel X Moore

  I'm creating a six player HTML 5 game designed to be played locally (Red Ice). I've previous set up handling 7 Wiimotes using something along the lines of Joy2Key to map each input for each player to a separate keyboard key, but Wiimotes are pretty hard on the hands for these types of games and not very ergonomic so I thought I'd try and get Xbox controller support. I don't believe that any simple key mapping solution will work due to the nature of the directional stick. My inclination is that this will require a browser plugin and if so I'd prefer to write the plugin for Google Chrome. How do I create a Chrome browser plugin to handle multiple Xbox controllers or is there some other way? Please do not answer this question saying it can't be done, because it absolutely can. EDIT: I don't believe any keymapping/mouse simulating solution will work unless it can reliably distinguish six axis of inputs, one per player.

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• Physics in carrom like game using cocos2d + Box2D

  - by Raj

  I am working on carrom like game using cocos2d + Box2D. I set world gravity(0,0), want gravity in z-axis. I set following values for coin and striker body: Coin body (circle with radius - 15/PTM_RATIO): density = 20.0f; friction = 0.4f; restitution = 0.6f; Striker body (circle with radius - 15/PTM_RATIO): density = 25.0f; friction = 0.6f; restitution = 0.3f; Output is not smooth. When I apply ApplyLinearImpulse(force,position) the coin movement looks like floating in the air - takes too much time to stop. What values for coin and striker make it look like real carrom?

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• Rotate sphere in Javascript / three.js while moving on x/z axes

  - by kaipr

  I have a sphere/ball in three.js which I want to "roll" arround on a x/z axis. For the z axe I could simply do this no matter what the current x and y rotation is: sphere.roll_z = function(distance) { sphere.position.z += distance; sphere.rotation.x += distance > 0 ? 0.05 : -0.05; } But how can I roll it along the x axe? And how could I properly do the roll_z? I've found a lot about quateration and matrixes, but I can't figure out how to use them properly to achieve my (rather simple) goal. I'm aware that I have to update multiple rotations and that I have to calculate how far to rotate the sphere to match the distance, but the "how" is the question. It's probably just lack of mathematical skills which I should train, but a working example/short explanation would help alot to start with.

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• Convert rotation from Right handed System to left handed

  - by Hector Llanos

  I have Euler angles from a right handed system that I am trying to convert to a left handed system. All the information that I have read online says that to convert it simply multiply the axis and the angle in the correct order and it should work. In other words, Z * Y * X. When I do this what I see in Maya, and in engine still do not match up. This is what I have so far: static Quaternion ConvertToRightHand(Vector3 Euler) { Quaternion x = Quaternion.AngleAxis(-Euler.x, Vector3.right); Quaternion y = Quaternion.AngleAxis(Euler.y, Vector3.up); Quaternion z = Quaternion.AngleAxis(Euler.z, Vector3.forward); return (z * y * x); } Keeping the -Euler.x helps keep the object pointing up correctly, but when I pass ( 0,0,0) to face in the -z, it faces in the +z. Help :/

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• Rotation based on x coordinate and x velocity?

  - by Lewis

  -(void) accelerometer:(UIAccelerometer *)accelerometer didAccelerate:(UIAcceleration *)acceleration { float deceleration = 0.3f, sensitivity = 8.0f, maxVelocity = 150; // adjust velocity based on current accelerometer acceleration playerVelocity.x = playerVelocity.x * deceleration + acceleration.x * sensitivity; // we must limit the maximum velocity of the player sprite, in both directions (positive & negative values) playerVelocity.x = fmaxf(fminf(playerVelocity.x, maxVelocity), -maxVelocity); } Hi, I want to rotate my sprite based on the velocity and accelerometer input. My sprite can move along the X axis like so: <--------- sprite ----------- But it always faces forwards, if it is moving left I want it to point slightly to the left, the degree of how far it is pointing to be judged from the velocity. This should also work for the right. I tried using atan but as the y velocity and position is always the same the function returns 0, which doesn't rotate it at all. Any ideas? Regards, Lewis.

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• Timing Calculations for Opengl ES 2.0 draw calls

  - by Arun AC

  I am drawing a cube in OpenGL ES 2.0 in Linux. I am calculating the time taken for each frame using below function #define NANO 1000000000 #define NANO_TO_MICRO(x) ((x)/1000) uint64_t getTick() { struct timespec stCT; clock_gettime(CLOCK_MONOTONIC, &stCT); uint64_t iCurrTimeNano = (1000000000 * stCT.tv_sec + stCT.tv_nsec); // in Nano Secs uint64_t iCurrTimeMicro = NANO_TO_MICRO(iCurrTimeNano); // in Micro Secs return iCurrTimeMicro; } I am running my code for 100 frames with simple x-axis rotation. I am getting around 200 to 220 microsecs per frame. that means am i getting around (1/220microsec = 4545) FPS Is my GPU is that fast? I strongly doubt this result. what went wrong in the code? Regards, Arun AC

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• Ever wonder why Earth spins?

  - by Gopinath

  Have you ever wonder why Earth spins on its axis and completes a revolution every day? Is there any force that keeps Earth spinning? Is that because of  Gravity or any Magnetic force? Check out this video to learn why Earth spins and the basics of physics behind the magic If you find that above video is in simple English and it’s not convincing physicist inside you, lets hear from a NASA scientist in the embedded video. A NASA scientist explains how Earth rotation has started, how fast it was billions of years ago and what caused it to slow down to 24 hours to complete a revolution   Thanks @pinaldev

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• Analog sticks not working, qtsixa+PCSX combination

  - by Otto Boström

  A few days ago I finally got my PS3 controller to work with QtSixA, and then in PCSX after some tweaking with the controls. But, I haven't figured out how on earth I will be able to get the analog sticks working. I've been triyng to add them in the controls for all angles in PCSX, where you move the analog stick the way it's supposed to be and then clicking a button to change the setting. I've enabled joysticks in the options for the controller, and my options in my controller are: [x] Enable buttons [x] Enable sensitive buttons [x] Enable Axis [ ] Enable accellerometers [ ] Enable Acceleration [ ] Enable Speed [ ] Enable position The controller is a standard PS3 controller, Dualshock 3. Plugged in with USB cable. Thanks in forehand!

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• Texturize a shape of multiple triangles in 2D

  - by Deukalion

  This is an example of a shape consisting of multiple points, triangles and eventually a shape: Red Dots = Vector3 (X, Y, Z) or Vector2 (X, Y) If I have a Texture of a certain size, how do I texturize this area in the best way so that the texture inside the shape matches the shape and does not overlap anywhere? Perhaps also with a chance to scale the texture in case it's too small or to big for the shape, but still so that it gets rendered correctly. Do I treat the shape as a rectangle? Figure out it's 4 corners? Or do I calculate the distance between Center - (Texture Width / 2) and Point (to see how "many" times the texture can fit between on that axis to estimate at what Coordinates the Texture should be at that certain point? I've looked at Texture Mapping but haven't found any concrete examples that it explains it well, it's also confusing with 0.0-1.0 values for Texture Coordinates.

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• Constrained/penalized distance function

  - by sigma.z.1980

  Assume a character is located on a n by n grid and has to reach a certain entry on that grid. Its current position is (x1,y1). Also on the same grid is an enemy with coordinates (x2,y2). Each step algorithm randomly generates new candidate locations for the hero (if there are k candidates then there is a kx2 matrix of new potential locations. What I need is some distance objective function to compare the candidates. I'm currently using d1 - c * d2, where d1 is distance to the objective (measure in terms of number of pixels for each axis), d2 is distance to the enemy and c is some coefficient (this is very much like a set-up for Lagrangian). It's not working very well though. I'd be quite keen to learn how what constrained distance function are used for similar cases. Any suggestions are very much appreciated.

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• Visual Tree Enumeration

  - by codingbloke

  I feel compelled to post this blog because I find I’m repeatedly posting this same code in silverlight and windows-phone-7 answers in Stackoverflow. One common task that we feel we need to do is burrow into the visual tree in a Silverlight or Windows Phone 7 application (actually more recently I found myself doing this in WPF as well).  This allows access to details that aren’t exposed directly by some controls.  A good example of this sort of requirement is found in the “Restoring exact scroll position of a listbox in Windows Phone 7”  question on stackoverflow.  This required that the scroll position of the scroll viewer internal to a listbox be accessed. A caveat One caveat here is that we should seriously challenge the need for this burrowing since it may indicate that there is a design problem.  Burrowing into the visual tree or indeed burrowing out to containing ancestors could represent significant coupling between module boundaries and that generally isn’t a good idea. Why isn’t this idea just not cast aside as a no-no?  Well the whole concept of a “Templated Control”, which are in extensive use in these applications, opens the coupling between the content of the visual tree and the internal code of a control.   For example, I can completely change the appearance and positioning of elements that make up a ComboBox.  The ComboBox control relies on specific template parts having set names of a specified type being present in my template.  Rightly or wrongly this does kind of give license to writing code that has similar coupling. Hasn’t this been done already? Yes it has.  There are number of blogs already out there with similar solutions.  In fact if you are using Silverlight toolkit the VisualTreeExtensions class already provides this feature.  However I prefer my specific code because of the simplicity principle I hold to.  Only write the minimum code necessary to give all the features needed.  In this case I add just two extension methods Ancestors and Descendents, note I don’t bother with “Get” or “Visual” prefixes.  Also I haven’t added Parent or Children methods nor additional “AndSelf” methods because all but Children is achievable with the addition of some other Linq methods.  I decided to give Descendents an additional overload for depth hence a depth of 1 is equivalent to Children but this overload is a little more flexible than simply Children. So here is the code:- VisualTreeEnumeration public static class VisualTreeEnumeration {     public static IEnumerable<DependencyObject> Descendents(this DependencyObject root, int depth)     {         int count = VisualTreeHelper.GetChildrenCount(root);         for (int i = 0; i < count; i++)         {             var child = VisualTreeHelper.GetChild(root, i);             yield return child;             if (depth > 0)             {                 foreach (var descendent in Descendents(child, --depth))                     yield return descendent;             }         }     }     public static IEnumerable<DependencyObject> Descendents(this DependencyObject root)     {         return Descendents(root, Int32.MaxValue);     }     public static IEnumerable<DependencyObject> Ancestors(this DependencyObject root)     {         DependencyObject current = VisualTreeHelper.GetParent(root);         while (current != null)         {             yield return current;             current = VisualTreeHelper.GetParent(current);         }     } }   Usage examples The following are some examples of how to combine the above extension methods with Linq to generate the other axis scenarios that tree traversal code might require. Missing Axis Scenarios var parent = control.Ancestors().Take(1).FirstOrDefault(); var children = control.Descendents(1); var previousSiblings = control.Ancestors().Take(1)     .SelectMany(p => p.Descendents(1).TakeWhile(c => c != control)); var followingSiblings = control.Ancestors().Take(1)     .SelectMany(p => p.Descendents(1).SkipWhile(c => c != control).Skip(1)); var ancestorsAndSelf = Enumerable.Repeat((DependencyObject)control, 1)     .Concat(control.Ancestors()); var descendentsAndSelf = Enumerable.Repeat((DependencyObject)control, 1)     .Concat(control.Descendents()); You might ask why I don’t just include these in the VisualTreeEnumerator.  I don’t on the principle of only including code that is actually needed.  If you find that one or more of the above  is needed in your code then go ahead and create additional methods.  One of the downsides to Extension methods is that they can make finding the method you actually want in intellisense harder. Here are some real world usage scenarios for these methods:- Real World Scenarios //Gets the internal scrollviewer of a ListBox ScrollViewer sv = someListBox.Descendents().OfType<ScrollViewer>().FirstOrDefault(); // Get all text boxes in current UserControl:- var textBoxes = this.Descendents().OfType<TextBox>(); // All UIElement direct children of the layout root grid:- var topLevelElements = LayoutRoot.Descendents(0).OfType<UIElement>(); // Find the containing `ListBoxItem` for a UIElement:- var container = elem.Ancestors().OfType<ListBoxItem>().FirstOrDefault(); // Seek a button with the name "PinkElephants" even if outside of the current Namescope:- var pinkElephantsButton = this.Descendents()     .OfType<Button>()     .FirstOrDefault(b => b.Name == "PinkElephants"); //Clear all checkboxes with the name "Selector" in a Treeview foreach (CheckBox checkBox in elem.Descendents()     .OfType<CheckBox>().Where(c => c.Name == "Selector")) {     checkBox.IsChecked = false; }   The last couple of examples above demonstrate a common requirement of finding controls that have a specific name.  FindName will often not find these controls because they exist in a different namescope. Hope you find this useful, if not I’m just glad to be able to link to this blog in future stackoverflow answers.

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• Tips for adapting Date table to Power View forecasting #powerview #powerbi

  - by Marco Russo (SQLBI)

  During the keynote of the PASS Business Analytics Conference, Amir Netz presented the new forecasting capabilities in Power View for Office 365. I immediately tried the new feature (which was immediately available, a welcome surprise in a Microsoft announcement for a new release) and I had several issues trying to use existing data models. The forecasting has a few requirements that are not compatible with the “best practices” commonly used for a calendar table until this announcement. For example, if you have a Year-Month-Day hierarchy and you want to display a line chart aggregating data at the month level, you use a column containing month and year as a string (e.g. May 2014) sorted by a numeric column (such as 201405). Such a column cannot be used in the x-axis of a line chart for forecasting, because you need a date or numeric column. There are also other requirements and I wrote the article Prepare Data for Power View Forecasting in Power BI on SQLBI, describing how to create columns that can be used with the new forecasting capabilities in Power View for Office 365.

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• How does a BSP tree work for Z sorting?

  - by Jenko

  I'm developing a 3D engine in software, and so I must compute Z sorting manually. I'm currently using the painters algorithm to sort triangles and then drawing them back-to-front. This causes artifacts that I'm trying to correct. Would using a dynamic BSP-tree ensure "correct Z sorting" of triangles? Why? Because the bounding volumes of triangles would be similar? Since I would have a single "world" BSP tree, would I have to remove and re-add any moved/scaled/rotated object into the tree? Is it possible to add triangles into a BSP tree without the expensive cutting process? Why do you need to cut triangles on the axis planes anyway? Is it faster to traverse a BSP tree from any angle, than to sort all tris each draw like the painters algorithm?

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• eGalax Touchscreen not working Jolicloud 1.2

  - by craigsmith86

  I have an eGalax touchscreen on an Acer Aspire One running Jolicloud 1.2 I have had success getting this touchscreen to work correctly on ubuntu 10.04NBR, 11.04 and Kubuntu 12.04 and Puppy Linux, so I am pretty happy with how it SHOULD be done. However, I cannot get it to calibrate correctly or remember calibration settings. I have installed the eGalax utility (all available versions) and it does not recognize the screen. Xinput_calibrator works but the config cannot be made permanent. Problems I have identified: -Joli doesn't have an xorg.conf file and does not use xorg.conf.d for evdev configuration -Setting configs through Hal doesn't work anymore The best I can get is a poorly adjusted touchscreen with a reversed Y axis. Any help greatly appreciated

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• Finding closest object to a location within a specific perpendicular distance to direction vector

  - by Sniper

  I have a location and a direction vector indicating facing, I want to find the closest object to that location that is within some tolerance distance (perpendicular distance) to the ray formed by the location and direction vector. Basically I want to get the object that is being aimed at. I have thought about finding all objects within a box and then finding the closest object to my vector from them results, but I am sure that there is a more efficient way. The Z axis is optional, the objects are most likely within a few meters of the search vector.

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• Ease Rotate RigidBody2D toward arbitrary angle

  - by Plastic Sturgeon

  I'm trying to make a rigidbody2D circle return to an orientation after a collision. But there is a weird behavior I do not expect - it always orients to the same direction. This is what I call in FixedUpdate(): rotationdifference = -halfPI + rigidbody2D.rotation; rigidbody2D.AddTorque (rotationdifference * ease); I would expect this would rotate 90 degrees (1/2 Pi Radians) off of the neutral axis. But it does not. In fact it performs exactly the same as: rotationdifference = rigidbody2D.rotation; rigidbody2D.AddTorque (rotationdifference * ease); What is going on? How would I be able to set an angle I want it to ease towards, and then have it ease towards it when its not colliding with some other force?

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• Box 2D Collision Question

  - by Farooq Arshed

  I am very new to Box 2D Physics world. I wanted to know how to collide 2 bodies when one is Dynamic and other is Kinematic. The whole Scenario is explained below: I have 3 balls in total. I want to balls to remain in their places and the third ball to be able to move. When the third ball hits the other two balls then they should move according to the speed and direction from which they were hit. My gravity of the world is 0 because I only want z-axis gravity. I would also like some one to point me towards some good tutorials regarding Box 2D basics which is language independent. I hope I have explained my scenario well. Thanks for the help in advance.

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