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  • Offset Forward vector of object based on Rotation

    - by Taylor
    I'm using the Bullet 3D physics engine in a iOS application running openGL ES 1.1 Currently I'm accepting info from the gyroscope to allow the user to "look around" a 3d world that follows a bouncing ball (note: it only takes in the yaw to look around 360 degrees). Im also accepting information from the accelerometer based on the tilt to push the ball. As of right now, to move forward, the user tilts the devise forward (using the accelerometer); to move to the right, the user tilts the devise to the right and so on. The forward vector is currently along it's local Z-axis. The problem is that I want to change the ball bounce based on where the user has changed the view. If I change the view, the ball bounces in the fixed direction. I want to change the forward facing direction so that when a user changes the view (say to the look at the right of the world, the user rotates the device), tilting the devise forward will result in a forward force in that direction. Basically, I want the forward vector to take the rotation into consideration. Sorry if I didn't explain the issue well enough, its kind of confusing to write down.

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  • Rewrite probabilities as boolean algebra

    - by Magsol
    I'm given three binary random variables: X, Y, and Z. I'm also given the following: P(Z | X) P(Z | Y) P(X) P(Y) I'm then supposed to determine whether or not it is possible to find P(Z | Y, X). I've tried rewriting the solution in the form of Bayes' Theorem and have gotten nowhere. Given that these are boolean random variables, is it possible to rewrite the system in terms of boolean algebra? I understand that the conditionals can be mapped to boolean implications (x -> y, or !x + y), but I'm unsure how this would translate in terms of the overall problem I'm trying to solve. (yes, this is a homework problem, but here I'm much more interested in how to formally solve this problem than what the solution is...I also figured this question would be entirely too simple for MathOverflow)

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  • How do I intiailize the vector I have defined in my header file?

    - by FrankTheTank
    I have the following in my Puzzle.h class Puzzle { private: vector<int> puzzle; public: Puzzle() : puzzle (16) {} bool isSolved(); void shuffle(vector<int>& ); }; and then my Puzzle.cpp looks like: Puzzle::Puzzle() { // Initialize the puzzle (0,1,2,3,...,14,15) for(int i = 0; i <= puzzle.size(); i++) { puzzle[i] = i; } } // ... other methods Am I using the initiailizer list wrong in my header file? I would like to define a vector of ints and initialize its size to that of 16. How should I do this? G++ Output: Puzzle.cpp:16: error: expected unqualified-id before ')' token Puzzle.cpp: In constructor `Puzzle::Puzzle()': Puzzle.cpp:16: error: expected `)' at end of input Puzzle.cpp:16: error: expected `{' at end of input Puzzle.cpp: At global scope: Puzzle.cpp:24: error: redefinition of `Puzzle::Puzzle()' Puzzle.cpp:16: error: `Puzzle::Puzzle()' previously defined here

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  • Calculate lookat vector from position and Euler angles

    - by Jaap
    I've implemented an FPS style camera, with the camera consisting of a position vector, and Euler angles pitch and yaw (x and y rotations). After setting up the projection matrix, I then translate to camera coordinates by rotating, then translating to the inverse of the camera position: // Load projection matrix glMatrixMode(GL_PROJECTION); glLoadIdentity(); // Set perspective gluPerspective(m_fFOV, m_fWidth/m_fHeight, m_fNear, m_fFar); // Load modelview matrix glMatrixMode(GL_MODELVIEW); glLoadIdentity(); // Position camera glRotatef(m_fRotateX, 1.0, 0.0, 0.0); glRotatef(m_fRotateY, 0.0, 1.0, 0.0); glTranslatef(-m_vPosition.x, -m_vPosition.y, -m_vPosition.z); Now I've got a few viewports set up, each with its own camera, and from every camera I render the position of the other cameras (as a simple box). I'd like to also draw the view vector for these cameras, except I haven't a clue how to calculate the lookat vector from the position and Euler angles. I've tried to multiply the original camera vector (0, 0, -1) by a matrix representing the camera rotations then adding the camera position to the transformed vector, but that doesn't work at all (most probably because I'm way off base): vector v1(0, 0, -1); matrix m1 = matrix::IDENTITY; m1.rotate(m_fRotateX, 0, 0); m1.rotate(0, m_fRotateY, 0); vector v2 = v1 * m1; v2 = v2 + m_vPosition; // add camera position vector glBegin(GL_LINES); glVertex3fv(m_vPosition); glVertex3fv(v2); glEnd(); What I'd like is to draw a line segment from the camera towards the lookat direction. I've looked all over the place for examples of this, but can't seem to find anything. Thanks a lot!

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  • C++: select argmax over vector of classes w.r.t. arbitrary expression

    - by karpathy
    Hello, I have trouble describing my problem so I'll give an example: I have a class description that has a couple of variables in it, for example: class A{ float a, b, c, d; } Now, I maintain a vector<A> that contains many of these classes. What I need to do very very often is to find the object inside this vector that satisfies that one of it's parameters is maximal w.r.t to the others. i.e code looks something like: int maxi=-1; float maxa=-1000; for(int i=0;i<vec.size();i++){ res= vec[i].a; if(res > maxa) { maxa= res; maxi=i; } } return vec[maxi]; However, sometimes I need to find class with maximal a, sometimes with maximal b, sometimes the class with maximal 0.8*a + 0.2*b, sometimes I want a maximal a*VAR + b, where VAR is some variable that is assigned in front, etc. In other words, I need to evaluate an expression for every class, and take the max. I find myself copy-pasting this everywhere, and only changing the single line that defines res. What makes it even more complicated is that even the name of the vector changes. Sometimes it's vec, sometimes it can be something else. I have many vectors that contain A's. This could be changed if this makes the problem too hard. Is there some nice way to avoid this insanity in C++? What's the neatest way to handle this? Thank you!

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  • how to pass vector of string to foo(char const *const *const)?

    - by user347208
    Hi, This is my first post so please be nice. I searched in this forum and googled but I still can not find the answer. This problem has bothered me for more than a day, so please give me some help. Thank you. I need to pass a vector of string to a library function foo(char const *const *const). I can not pass the &Vec[0] since it's a pointer to a string. Therefore, I have an array and pass the c_str() to that array. The following is my code (aNames is the vector of string): const char* aR[aNames.size()]; std::transform(aNames.begin(), aNames.end(), aR, boost::bind(&std::string::c_str, _1)); foo(aR); However, it seems it causes some undefined behavior: If I run the above code, then the function foo throw some warnings about illegal characters ('èI' blablabla) in aR. If I print aR before function foo like this: std::copy(aR, aR+rowNames.size(), std::ostream_iterator<const char*>(std::cout, "\n")); foo(aR); Then, everything is fine. My questions are: Does the conversion causes undefined behavior? If so, why? What is the correct way to pass vector of string to foo(char const *const *const)? Thank you very much for your help!

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  • Why can't my vector access the variables in my nested structs?

    - by chucknorris
    #include<iostream> #include<vector> #include<string> #include<list> using namespace std; struct record{ int id; string fName; }; struct cells{ list<record> rec; }; vector<cells> hp; int main() { **hp.front().rec.front().fName = "jon"; return 0; } I have 2 structs. The first struct, struct record, is composed of 2 regular variables. In struct 2, I have a linked list of type "record", which includes all the variable listed in struct 1. Why is it that when ever I attempt to access a variable in the structs, using my vector, I get the error "linked list iterator not dereferencable?"

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  • Textures quality issues with Libgdx

    - by user1876708
    I have drawn several vector objets and characters ( in Adobe Illustrator ) for my game on Android. They are all scalable at any size without any quality losses ( of course it's vector ^^ ). I have tried to simulate my gameboard directly on Illustrator just before setting my assests on libdgx to implement them in my game. I set all the objects at the good size, so that they fit perfectly on my XHDPI device I am running my test on. As you can see it works great ( for me at least ^^ ), the PNG quality is good for me, as expected ! So I have edited all my PNG at this size, set my assets on libgdx and build my game apk. And here is a screenshot of my gameboard ( don't pay attention at the differences of placing and objects, but check at the objets presents on both screenshot ). As you can see, I have a loss of my PNG quality in the game. It can be seen clealry on the hedgehog PNG, but also ( but not as obvious ) on the mushroom ( check at the outline ) and the hole PNG. If you really pay attention, on every objects, you can see pixels that are not visible on my first screenshot. And I just can't figure out why this is happening Oo If you have any ideas, you are very welcome ! Thanks. PS : You can check more clearly the 2 gameboard on this two links ( look at them at 100%, display at high resolution ) : Good quality link, from Illustrator Poor quality link, from the game Second phase of tests : We display an object ( the hedgehog ) on our main menu screen to see how it looks like. The things is that it looks like he is suppose to, which means, high quality with no pixels. The hedgehog PNG is coming from an atlas : layer.addActor(hedgehog); No loss of quality with this method So we think the problem is comming from the method we are using to display it on our gameboard : blocks[9][3] = new Block(TextureUtils.hedgehog, new Vector2(9, 3)); the block is getting the size from the vector we are associating to it, but we have a loss of quality with this method.

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  • Unity: parallel vectors and cross product, how to compare vectors

    - by Heisenbug
    I read this post explaining a method to understand if the angle between 2 given vectors and the normal to the plane described by them, is clockwise or anticlockwise: public static AngleDir GetAngleDirection(Vector3 beginDir, Vector3 endDir, Vector3 upDir) { Vector3 cross = Vector3.Cross(beginDir, endDir); float dot = Vector3.Dot(cross, upDir); if (dot > 0.0f) return AngleDir.CLOCK; else if (dot < 0.0f) return AngleDir.ANTICLOCK; return AngleDir.PARALLEL; } After having used it a little bit, I think it's wrong. If I supply the same vector as input (beginDir equal to endDir), the cross product is zero, but the dot product is a little bit more than zero. I think that to fix that I can simply check if the cross product is zero, means that the 2 vectors are parallel, but my code doesn't work. I tried the following solution: Vector3 cross = Vector3.Cross(beginDir, endDir); if (cross == Vector.zero) return AngleDir.PARALLEL; And it doesn't work because comparison between Vector.zero and cross is always different from zero (even if cross is actually [0.0f, 0.0f, 0.0f]). I tried also this: Vector3 cross = Vector3.Cross(beginDir, endDir); if (cross.magnitude == 0.0f) return AngleDir.PARALLEL; it also fails because magnitude is slightly more than zero. So my question is: given 2 Vector3 in Unity, how to compare them? I need the elegant equivalent version of this: if (beginDir.x == endDir.x && beginDir.y == endDir.y && beginDir.z == endDir.z) return true;

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  • Android - big game universe

    - by user1641923
    I am new to an Android development, though I have much experience with Java, C++, PHP programming and a bit experience with vector graphics too (basic 3d Studio Max, Flash, etc). I am starting to work on an Android game. It is going to be a 2D space shooter/RPG, and I am not going to use any game engines and any 3D party libs. I really want to create a very large game universe, or even pseudo-infinite (without visible borders, as if it were a 2D projection of a sphere). It should include 10-12 clusters of 7-8 planets/other space objects and random amount of single asteroids/comets, which player can interact with and also not interactive background. I am looking for a least complicated aproach to create such a universe. My current ideas are: Simply create bitmaps with space scenery background so that they can be tiled seamlessly repeated and construct my 2D universe of this tiles, then place interactive objects (planets, other spaceships) on it. Using vector graphics. I would have a solid color background, some random background objects and gradients here and there. My problems here: Lack of knowledge of how well vector graphics is integrated in Android. Performance? Memory usage? Does Android manage big bitmaps well? Do all of the bitmaps have to be in memory during all game process? I am interested in technical details regarding each of the ideas and a suggestion, which I should go with.

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  • Reflection velocity

    - by MindSeeker
    I'm trying to get a moving circular object to bounce (elastically) off of an immovable circular object. Am I doing this right? (The results look right, but I hate to trust that alone, and I can't find a tutorial that tackles this problem and includes the nitty gritty math/code to verify what I'm doing). If it is right, is there a better/faster/more elegant way to do this? Note that the object (this) is the moving circle, and the EntPointer object is the immovable circle. //take vector separating the two centers <x, y>, and then get unit vector of the result: MathVector2d unitnormal = MathVector2d(this -> Retxpos() - EntPointer -> Retxpos(), this -> Retypos() - EntPointer -> Retypos()).UnitVector(); //take tangent <-y, x> of the unitnormal: MathVector2d unittangent = MathVector2d(-unitnormal.ycomp, unitnormal.xcomp); MathVector2d V1 = MathVector2d(this -> Retxvel(), this -> Retyvel()); //Calculate the normal and tangent vector lengths of the velocity: (the normal changes, the tangent stays the same) double LengthNormal = DotProduct(unitnormal, V1); double LengthTangent = DotProduct(unittangent, V1); MathVector2d VelVecNewNormal = unitnormal.ScalarMultiplication(-LengthNormal); //the negative of what it was before MathVector2d VelVecNewTangent = unittangent.ScalarMultiplication(LengthTangent); //this stays the same MathVector2d NewVel = VectorAddition(VelVecNewNormal, VelVecNewTangent); //combine them xvel = NewVel.xcomp; //and then apply them yvel = NewVel.ycomp; Note also that this question is just about velocity, the position code is handled elsewhere (in other words, assume that this code is implemented at the exact moment that the circles begin to overlap). Thanks in advance for your help and time!

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  • Plot vectors with labels in matlab

    - by mad
    I have a Nx62 matrix with N 62-D vectors and a NX1 vector with the labels for the vectors. I am trying to plot these vectors with their labels because I want to see the behavior of these classes when plotted in a 62-dimensional space. The vectors belong to three classes according to the labels of a NX1 vector cited before. How to to that in matlab? when i do plot(vector,classes) the result is very weird to analyse, how to put labels in the graph? The code i am using to get the labels, vectors and plotting is the following: %labels is a vector with labels, vectors is a matrix where each line is a vector [labels,vectors]=libsvmread('features-im1.txt'); when I plot a three dimensional vector is simple a=[1,2,3] plot(a) and then I get the result but now i have a set of vectors and a set of labels, and i want to see the distribution of them, i want to plot each of these labels but also want to identify their classes. How to do that in matlab? EDIT: This code is almost working. The problem is the fact that for each vector and class the plot will assign a color. I just want three colors and three labels, one per class. [class,vector]=libsvmread('features-im1.txt'); %the plot doesn't allow negative and 0 values in the label class=class+2; labels = {'class -1','class 0','class 1'}; h = plot(vector); legend(h,labels{class})

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  • Convert vector interpolation to quaternion interpolation? (Catmull-Rom)

    - by edA-qa mort-ora-y
    I have some existing code which does catmull-rom interpolation on two vectors (facing and up). I'm converting this to use quaternions instead (to replace the two vectors). Is there a general way to convert the vector based interpolation to a quaternion one? The approach I'm using now is to exact the axis and angle from the quanternion. I then interpolate each of those independently and convert back to a quaternion. Is there a more direct method?

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  • Making a Camera look at a target Vector

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

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  • Random Vector within a cone

    - by Paul
    I'm looking to create a random vector within a cone given the radius (base). It feels like I've been traversing through many pages on the internet and still I'm no further forward to getting an answer. I was thinking I could get a point within the base of the cone and have it point towards the apex (then just use the inverse of that for my animation) but this seems like an incredibly long winded approach.

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  • Calculating a circle or sphere along a vector

    - by Sparky
    Updated this post and the one at Math SE (http://math.stackexchange.com/questions/127866/calculating-a-circle-or-sphere-along-a-vector), hope this makes more sense. I previously posted a question (about half an hour ago) involving computations along line segments, but the question and discussion were really off track and not what I was trying to get at. I am trying to work with an FPS engine I am attempting to build in Java. The problem I am encountering is with hitboxing. I am trying to calculate whether or not a "shot" is valid. I am working with several approaches and any insight would be helpful. I am not a native speaker of English nor skilled in Math so please bear with me. Player position is at P0 = (x0,y0,z0), Enemy is at P1 = (x1,y1,z1). I can of course compute the distance between them easily. The target needs a "hitbox" object, which is basically a square/rectangle/mesh either in front of, in, or behind them. Here are the solutions I am considering: I have ruled this out...doesn't seem practical. [Place a "hitbox" a small distance in front of the target. Then I would be able to find the distance between the player and the hitbox, and the hitbox and the target. It is my understanding that you can compute a circle with this information, and I could simply consider any shot within that circle a "hit". However this seems not to be an optimal solution, because it requires you to perform a lot of calculations and is not fully accurate.] Input, please! Place the hitbox "in" the player. This seems like the better solution. In this case what I need is a way to calculate a circle along the vector, at whatever position I wish (in this case, the distance between the two objects). Then I can pick some radius that encompasses the whole player, and count anything within this area a "hit". I am open to your suggestions. I'm trying to do this on paper and have no familiarity with game engines. If any software folk out there think I'm doing this the hard way, I'm open to help! Also - Anyone with JOGL/LWJGL experience, please chime in. Is this making sense?

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  • Photoshop vector line

    - by Yuval
    When I use the line tool in Photoshop, it creates a vector layer mask with the shape of that line. When I draw a curved line with the pen tool, the only option I see for making a line out of the path is "Stroke path", which is not vector (raster). How do I create a vector line/curve with the pen tool in Photoshop (CS4)? Thanks!

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  • R: How can I reorder the rows of a matrix, data.frame or vector according to another one.

    - by John
    test1 <- as.matrix(c(1, 2, 3, 4, 5)) row.names(test1) <- c("a", "b", "c", "d", "e") test2 <- as.matrix(c(6, 7, 8, 9, 10)) row.names(test2) <- c("e", "d", "c", "b", "a") test1 [,1] a 1 d 2 c 3 b 4 e 5 test2 [,1] e 6 d 7 c 8 b 9 a 10 How can I reorder test2 so that the rows are in the same order as test1? e.g: test2 [,1] a 10 d 7 c 8 b 9 e 6 I tried to use the reorder function with: reorder (test1, test2) but I could not figure out the correct syntax. I see that reorder takes a vector, and I'm here using a matrix. My real data has one character vector and another as a data.frame. I figured that the data structure would not matter too much for this example above, I just need help with the syntax and can adapt it to my real problem.

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  • How to return a 'read-only' copy of a vector

    - by michael
    Hi, I have a class which has a private attribute vector rectVec; class A { private: vector<Rect> rectVec; }; My question is how can I return a 'read-only' copy of my Vector? I am thinking of doing this: class A { public: const vect<Rect>& getRectVec() { return rectVect; } } Is that the right way? I am thinking this can guard against the callee modify the vector(add/delete Rect in vector), what about the Rect inside the vector?

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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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  • convert orientation vec3 to a rotation matrix

    - by lapin
    I've got a normalized vec3 that represents an orientation. Each frame of animation, an object's orientation changes slightly, so I add a delta vector to the orientation vector and then normalize to find the new orientation. I'd like to convert the vec3 that represents an orientation into a rotation matrix that I can use to orient my object. If it helps, my object is a cone, and I'd like to rotate it about the pointy end, not from its center :) PS I know I should use quaternions because of the gimbal lock problem. If someone can explain quats too, that'd be great :)

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  • How To Use Layer Masks and Vector Masks to Remove Complex Backgrounds in Photoshop

    - by Eric Z Goodnight
    Ever removed a background in Photoshop, only to find want to use parts of that background later? Layer Masks and Vector Masks are the elegant and often misunderstood answer to this common problem. Keep reading to see how they work. In this article, we’ll learn exactly what a Layer Mask is, and two methods to use them in practically any version of Photoshop, including a simpler example for less experienced Photoshop users, and another for more seasoned users who are comfortable with the Pen tool and vectors Latest Features How-To Geek ETC How to Upgrade Windows 7 Easily (And Understand Whether You Should) The How-To Geek Guide to Audio Editing: Basic Noise Removal Install a Wii Game Loader for Easy Backups and Fast Load Times The Best of CES (Consumer Electronics Show) in 2011 The Worst of CES (Consumer Electronics Show) in 2011 HTG Projects: How to Create Your Own Custom Papercraft Toy Outlook2Evernote Imports Notes from Outlook to Evernote Firefox 4.0 Beta 9 Available for Download – Get Your Copy Now The Frustrations of a Computer Literate Watching a Newbie Use a Computer [Humorous Video] Season0nPass Jailbreaks Current Gen Apple TVs IBM’s Jeopardy Playing Computer Watson Shows The Pros How It’s Done [Video] Tranquil Juice Drop Abstract Wallpaper

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