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  • How can I calculate the angle between two 2D vectors?

    - by Error 454
    I am working on some movement AI where there are no obstacles and movement is restricted to the XY plane. I am calculating two vectors, v, the facing direction of ship 1, and w, the vector pointing from the position of ship 1 to ship 2. I am then calculating the angle between these two vectors using the formula arccos((v · w) / (|v| · |w|)) The problem I'm having is that arccos only returns values between 0° and 180°. This makes it impossible to determine whether I should turn left or right to face the other ship. Is there a better way to do this?

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  • Slide 2d Vector to destination over a period of time

    - by SchautDollar
    I am making a library of GUI controls for games I make with XNA. I am currently developing the library as I make a game so I can test the features and find errors/bugs and hopefully smash them right away. My current issue is on a slide feature I want to implement for my base class that all controls inherit. My goal is to get the control to slide to a specified point over a specified amount of time. Here is the #region containing the code #region Slide private bool sliding; private Vector2 endPoint; private float slideTimeLeft; private float speed; private bool wasEnabled; private Vector2 slideDirection; private float slideDistance; public void Slide(Vector2 startPoint, Vector2 endPoint, float slideTime) { this.location = startPoint; Slide(endPoint,slideTime); } public void Slide(Vector2 endPoint, float slideTime) { this.wasEnabled = this.enabled; this.enabled = false; this.sliding = true; Vector2 tempLength = endPoint - this.location; this.slideDistance = tempLength.Length(); //Was this.slideDistance = (float)Math.Sqrt(tempLength.LengthSquared()); this.speed = slideTime / this.slideDistance; this.endPoint = endPoint; this.slideTimeLeft = slideTime; } private void UpdateSlide(GameTime gameTime) { if (this.sliding) { this.slideTimeLeft -= gameTime.ElapsedGameTime.Milliseconds; if (this.slideTimeLeft >= 0 ) { if ((this.endPoint-this.location).Length() != 0){//Was if (this.endPoint.LengthSquared() > 0 || this.location.LengthSquared() > 0) { this.slideDirection = Vector2.Normalize(this.endPoint - this.location); } this.location += this.slideDirection * speed * gameTime.ElapsedGameTime.Milliseconds;//This is where I believe the issue is, but I'm not sure. It seems right to me... (Even though it doesn't work) } else { this.enabled = this.wasEnabled; this.location = this.endPoint;//After time, the controls position will get set to be the endpoint. this.sliding = false; } } } #endregion this.location is the location of the control elsewhere defined in the class. I have looked at this blog as a huge reference and have googled around quite and have looked on many forums but can't find anything that shows how to implement it. Please and Thanks for your time! EDIT: I have switched this line "this.location += this.slideDirection * speed * gameTime.ElapsedGameTime.Milliseconds;" several times to see what it does. My issue is getting the control to smoothly move to the end location. It moves after the time has expired, but It doesn't move other then that except flash in my face. EDIT2: I have used the first slide method with 3 parameters and it works except it doesn't do it in a period of time and once it gets to its destination, it starts moving randomly towards the previous location and the end location.

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  • How to pronounce "std" as in "std::vector"

    - by Lex Fridman
    In C++, the STL (standard template library) includes a namespace std that contains the many data structures and algorithms that we all know and love. I've always pronounced this namespace just like sexually transmitted diseases: S T D. But then I listened to this excellent series of lectures by Stephan T. Lavavej and he pronounces it "stood". Which is the "correct" pronunciation or at least what is that most commonly used one?

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  • iPhone OpenGL ES: How do I use gravity vector to correctly transform scene for augmented reality

    - by gpdawson
    I'm trying figure out how to get an OpenGL specified object to be displayed correctly according to the device orientation (ie. according to the gravity vector from the accelerometer, and heading from compass). The GLGravity sample project has an example which is almost like this (despite ignoring heading), but it has some glitches. For example, the teapot jumps 180deg as the device viewing angle crosses the horizon, and it also rotates spuriously if you tilt the device from portrait into landscape. This is fine for the context of this app, as it just shows off an object and it doesn't matter that it does these things. But it means that the code just doesn't work when you attempt to emulate real life viewing of an OpenGL object according to the device's orientation. What happens is that it almost works, but the heading rotation you apply from the compass gets "corrupted" by the spurious additional rotations seen in the GLGravity example project. Can anyone provide sample code that shows how to adjust correctly for the device orientation (ie. gravity vector), or to fix the GLGravity example so that it doesn't include spurious heading changes? //Clear matrix to be used to rotate from the current referential to one based on the gravity vector bzero(matrix, sizeof(matrix)); matrix[3][3] = 1.0; //Setup first matrix column as gravity vector matrix[0][0] = accel[0] / length; matrix[0][1] = accel[1] / length; matrix[0][2] = accel[2] / length; //Setup second matrix column as an arbitrary vector in the plane perpendicular to the gravity vector {Gx, Gy, Gz} defined by by the equation "Gx * x + Gy * y + Gz * z = 0" in which we arbitrarily set x=0 and y=1 matrix[1][0] = 0.0; matrix[1][1] = 1.0; matrix[1][2] = -accel[1] / accel[2]; length = sqrtf(matrix[1][0] * matrix[1][0] + matrix[1][1] * matrix[1][1] + matrix[1][2] * matrix[1][2]); matrix[1][0] /= length; matrix[1][1] /= length; matrix[1][2] /= length; //Setup third matrix column as the cross product of the first two matrix[2][0] = matrix[0][1] * matrix[1][2] - matrix[0][2] * matrix[1][1]; matrix[2][1] = matrix[1][0] * matrix[0][2] - matrix[1][2] * matrix[0][0]; matrix[2][2] = matrix[0][0] * matrix[1][1] - matrix[0][1] * matrix[1][0]; //Finally load matrix glMultMatrixf((GLfloat*)matrix);

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  • Fastest way to write large STL vector to file using STL

    - by ljubak
    I have a large vector (10^9 elements) of chars, and I was wondering what is the fastest way to write such vector to a file. So far I've been using next code: vector<char> vs; // ... Fill vector with data ofstream outfile("nanocube.txt", ios::out | ios::binary); ostream_iterator<char> oi(outfile, '\0'); copy(vs.begin(), vs.end(), oi); For this code it takes approximately two minutes to write all data to file. The actual question is: "Can I make it faster using STL and how"?

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  • Easier debugging stl array

    - by bobobobo
    In MSVC++ I have a vector. Whenever you go out of bounds of the vector (in debug mode, launched as "Start Debugging"), when you step out of bounds of the vector the program halts with a dialog box: Microsoft Visual C++ Debug Library ==== Debug Assertion Failed! Expression: Vector subscript out of range Abort | Retry | Ignore So what I want though is the MSVC++ debugger within visual studio to STOP AT THE LINE WHERE THE OUT OF BOUNDS OCCURRED, not give me this dialog box. How can I cause the program to "break" properly and be able to step through code /inspect variables when an out of bounds occurs on an STL vector?

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  • Loopless function calls on vector/matrix members in Matlab/Octave

    - by Sint
    I came into matrix world from loop world(C, etc) I would like to call a function on each individual member of a vector/matrix, and return the resulting vector/matrix. This is how I currently do it: function retval = gauss(v, a, b, c) for i = 1:length(v) retval(i) = a*(e^(-(v(i)-b)*(v(i)-b)/(2*c*c))); endfor endfunction Example usage: octave:47> d=[1:1000]; octave:48> mycurve=gauss(d, 1, 500, 100); Now, all advice on Matlab/Octave says: STOP whenever you catch yourself using loops and think of a better way of doing it. Thus, my question: Can one call a function on each member of a vector/matrix and return the result in a new vector/matrix all at once without using explicit loops? That is I am looking for something like this: function retval = newfun(v) retval = 42*(v^23); endfunction Perhaps, it is just syntactic sugar, that is all, but still would be useful to know.

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  • stringstream problem - vector iterator not dereferencable

    - by andreas
    Hello I've got a problem with the following code snippet. It is related to the stringstream "stringstream css(cv.back())" bit. If it is commented out the program will run ok. It is really weird, as I keep getting it in some of my programs, but if I just create a console project the code will run fine. In some of my Win32 programs it will and in some it won't (then it will return "vector iterator not dereferencable" but it will compile just fine). Any ideas at all would be really appreciated. Thanks! vector<double> cRes(2); vector<double> pRes(2); int readTimeVects2(vector<double> &cRes, vector<double> &pRes){ string segments; vector<string> cv, pv, chv, phv; ifstream cin("cm.txt"); ifstream pin("pw.txt"); ifstream chin("hm.txt"); ifstream phin("hw.txt"); while (getline(cin,segments,'\t')) { cv.push_back(segments); } while (getline(pin,segments,'\t')) { pv.push_back(segments); } while (getline(chin,segments,'\t')) { chv.push_back(segments); } while (getline(phin,segments,'\t')) { phv.push_back(segments); } cin.close(); pin.close(); chin.close(); phin.close(); stringstream phss(phv.front()); phss >> pRes[0]; phss.clear(); stringstream chss(chv.front()); chss >> cRes[0]; chss.clear(); stringstream pss(pv.back()); pss >> pRes[1]; pss.clear(); stringstream css(cv.back()); css >> cRes[1]; css.clear(); return 0; }

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  • Getting a char array from a vector<int>?

    - by Legend
    I am trying to pass a value from C++ to TCL. As I cannot pass pointers without the use of some complicated modules, I was thinking of converting a vector to a char array and then passing this as a null terminated string (which is relatively easy). I have a vector as follows: 12, 32, 42, 84 which I want to convert into something like: "12 32 42 48" The approach I am thinking of is to use an iterator to iterate through the vector and then convert each integer into its string representation and then add it into a char array (which is dynamically created initially by passing the size of the vector). Is this the right way or is there a function that already does this?

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  • Initialization of std::vector<unsigned int> with a list of consecutive unsigned integers

    - by Thomas
    I want to use a special method to initialize a std::vector<unsigned int> which is described in a C++ book I use as a reference (the German book 'Der C++ Programmer' by Ulrich Breymann, in case that matters). In that book is a section on sequence types of the STL, referring in particular to list, vector and deque. In this section he writes that there are two special constructors of such sequence types, namely, if Xrefers to such a type, X(n, t) // creates a sequence with n copies of t X(i, j) // creates a sequence from the elements of the interval [i, j) I want to use the second one for an interval of unsigned int, that is std::vector<unsigned int> l(1U, 10U); to get a list initialized with {1,2,...,9}. What I get, however, is a vector with one unsigned int with value 10 :-| Does the second variant exist, and if yes, how do I force that it is called?

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  • How do I find hash value of a 3D vector ?

    - by brainydexter
    I am trying to perform broad-phase collision detection with a fixed-grid size approach. Thus, for each entity's position: (x,y,z) (each of type float), I need to find which cell does the entity lie in. I then intend to store all the cells in a hash-table and then iterate through to report (if any) collisions. So, here is what I am doing: Grid-cell's position: (int type) (Gx, Gy, Gz) = (x / M, y / M, z / M) where M is the size of the grid. Once, I have a cell, I'd like to add it to a hash-table with its key being a unique hash based on (Gx, Gy, Gz) and the value being the cell itself. Now, I cannot think of a good hash function and I need some help with that. Can someone please suggest me a good hash function? Thanks

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  • C++ stack for multiple data types (RPN vector calculator)

    - by Arrieta
    Hello: I have designed a quick and basic vector arithmetic library in C++. I call the program from the command line when I need a rapid cross product, or angle between vectors. I don't use Matlab or Octave or related, because the startup time is larger than the computation time. Again, this is for very basic operations. I am extending this program, and I will make it work as an RPN calculator, for operations of the type: 1 2 3 4 5 6 x out: -3 6 -3 (give one vector, another vector, and the "cross" operator; spit out the cross product) The stack must accept 3d vectors or scalars, for operations like: 1 2 3 2 * out: 2 4 6 The lexer and parser for this mini-calculator are trivial, but I cannot seem to think of a good way for creating the internal stack. How would you create a stack of for containing vectors or doubles (I rolled up my own very simple vector class - less than one hundred lines and it does everything I need). How can I create a simple stack which accepts elements of class Vector or type double? Thank you.

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  • Is there a decent vector / spline library for php?

    - by Brendan Heywood
    Does anyone know of the best way to render clean vectors into a php image and then serve it as a jpeg/png? Specifically I want to draw lines, polygons and splines which are anti-aliased and then serve them up as jpegs. Preferably also with an alpha option when rendering. What would be spectacular is a php library with a similar API to Raphael (without the animation) - not only because Raphael has a great API but also because I'm already using it on my website for the dynamic bits but also need to bake jpeg's in parallel for static consumption.

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  • How to make std::vector's operator[] compile doing bounds checking in DEBUG but not in RELEASE

    - by Edison Gustavo Muenz
    I'm using Visual Studio 2008. I'm aware that std::vector has bounds checking with the at() function and has undefined behaviour if you try to access something using the operator [] incorrectly (out of range). I'm curious if it's possible to compile my program with the bounds checking. This way the operator[] would use the at() function and throw a std::out_of_range whenever something is out of bounds. The release mode would be compiled without bounds checking for operator[], so the performance doesn't degrade. I came into thinking about this because I'm migrating an app that was written using Borland C++ to Visual Studio and in a small part of the code I have this (with i=0, j=1): v[i][j]; //v is a std::vector<std::vector<int> > The size of the vector 'v' is [0][1] (so element 0 of the vector has only one element). This is undefined behaviour, I know, but Borland is returning 0 here, VS is crashing. I like the crash better than returning 0, so if I can get more 'crashes' by the std::out_of_range exception being thrown, the migration would be completed faster (so it would expose more bugs that Borland was hiding).

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  • In ActionScript, Is there a way to check if an input argument is a valid Vector of any type?

    - by ty
    In the following code: var a:Vector.<int> ... var b:Vector.<String> ... var c:Vector.<uint> ... var c:Vector.<MyOwnClass> ... function verifyArrayLike(arr:*):Boolean { return (arr is Array || arr is Vector) } verifyArrayLike(a); verifyArrayLike(b); ... What I'm looking for is something like _var is Vector.<*> But Vector.<*> is not a valid expression, even Vector. can not be placed at the right side of operators. Is there a way to check if an input argument is a valid Vector of any type?

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  • Codebase for making a Flash-based interactive map with SVG vector data?

    - by Mike
    I'm looking for a way to take SVG path info (basically a string of coordinates) and dynamically draw it with Actionscript. Icing on the cake would be if those shapes could detect mouse events to trigger JS and dynamically change their appearance (fill, stroke, etc...). I'm currently trying something similar to this (http://raphaeljs.com/australia.html) using SVG but it's just too slow in IE. I've also tried Google's SVG Web (http://code.google.com/p/svgweb/) which basically does exactly what I'm looking for (it converts SVG to Flash in IE) but again, it's sloooooow - which is why I'm considering doing the whole shebang in Flash. Anyone know of some links to point me in the right direction?

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  • Having trouble storing a CRTP based class in a vector

    - by user366834
    Hi, Im not sure if this can be done, im just delving into templates so perhaps my understanding is a bit wrong. I have a Platoon of soldiers, the platoon inherits from a formation to pick up the formations properties, but because i could have as many formations as i can think of I chose to use the CRTP to create the formations, hoping that i could make a vector or array of Platoon to store the platoons in. but, of course, when i make a Platoon, it wont store it in the vector, "types are unrelated" Is there any way around this ? i read about "Veneers" which are similar and that they work with arrays but i cant get it to work, perhaps im missing something. here's some code: (sorry about the formatting, the code is here in my post but its not showing up for some reason ) template < class TBase > class IFormation { public : ~IFormation(){} bool IsFull() { return m_uiMaxMembers == m_uiCurrentMemCount; } protected: unsigned int m_uiCurrentMemCount; unsigned int m_uiMaxMembers; IFormation( unsigned int _uiMaxMembers ): m_uiMaxMembers( _uiMaxMembers ), m_uiCurrentMemCount( 0 ){} // only allow use as a base class. void SetupFormation( std::vector<MySoldier*>& _soldierList ){}; // must be implemented in derived class }; ///////////////////////////////////////////////////////////////////////////////// // PHALANX FORMATION class Phalanx : public IFormation<Phalanx> { public: Phalanx( ): IFormation( 12 ), m_fDistance( 4.0f ) {} ~Phalanx(){} protected: float m_fDistance; // the distance between soldiers void SetupFormation( std::vector<MySoldier*>& _soldierList ); }; /////////////////////////////////////////////////////////////////////////////////// // COLUMN FORMATINO class Column : public IFormation< Column > { public : Column( int _numOfMembers ): IFormation( _numOfMembers ) {} ~Column(); protected: void SetupFormation( std::vector<MySoldier*>& _soldierList ); }; I then use these formations in the platoon class to derive, so that platoon gets the relevant SetupFormation() function: template < class Formation > class Platoon : public Formation { public: **** platoon code here }; everything works great and as expected up until this point. now, as my general can have multiple platoons, I need to store the platoons. typedef Platoon< IFormation<> > TPlatoon; // FAIL typedef std::vector<TPlatoon*> TPlatoons; TPlatoon m_pPlatoons m_pPlatoons.push_back( new Platoon<Phalanx> ); // FAIL, types unrelated. typedef Platoon< IFormation< TPlatoon; fails because i need to specify a template parameter, yet specifying this will only allow me to store platoons created with the same template parameter. so i then created FormationBase class FormationBase { public: virtual bool IsFull() = 0; virtual void SetupFormation( std::vector<MySoldier*>& _soldierList ) = 0; }; and made IFormation publicly inherit from that, and then changed the typedef to typedef Platoon< IFormation< FormationBase > > TPlatoon; but still no love. now in my searches i have not found info that says this is possible - or not possible.

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  • How do I resize a flat vector icon so that it preserves hard edges in Photoshop (CS4)

    - by Adam Singer
    I recently purchased Drew Wilson's Pictos icon library. It is a library of flat, monochromatic icons for use on the web and elsewhere. The only issue is: they're vectors. I know my way around Illustrator a little bit, but ultimately I want to import these icons into Photoshop and resize to various dimensions. The problem I'm having: when I import an icon and resize it to, say, 20x20 pixels, I notice that there is a fair bit of aliasing around the edges of the icon. I'm sure there is some magic number where the edges of these icons will remain crisp, but I can't find any option or setting that will allow me to size these icons properly. Is there a way in Photoshop to snap these icons to the closest size that removes or minimizes the aliasing?

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  • Nonstatic conversion functions; Casting different types, e.g. DirectX vector to OpenGL vector

    - by Markus
    I am currently working on a game "engine" that needs to move values between a 3D engine, a physics engine and a scripting language. Since I need to apply vectors from the physics engine to 3D objects very often and want to be able to control both the 3D, as well as the physics objects through the scripting system, I need a mechanism to convert a vector of one type (e.g. vector3d<float>) to a vector of the other type (e.g. btVector3). Unfortunately I can make no assumptions on how the classes/structs are laid out, so a simple reinterpret_cast probably won't do. So the question is: Is there some sort of 'static'/non-member casting method to achieve basically this: vector3d<float> operator vector3d<float>(btVector3 vector) { // convert and return } btVector3 operator btVector3(vector3d<float> vector) { // convert and return } Right now this won't compile since casting operators need to be member methods. (error C2801: 'operator foo' must be a non-static member)

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  • Find most right and left point of a horizontal circle in 3d Vector environment

    - by Olivier de Jonge
    I'm drawing a 3D pie chart that is rendered with in 3D vectors, projected to 2D vectors and then drawn on a Graphics object. I want to calculate the most left and right point of the circle The method to create a vector, draw and project to a 2d vector are below. Anyone knows the answer? public class Vector3d { public var x:Number; public var y:Number; public var z:Number; //the angle that the 3D is viewed in tele or wide angle. public static var viewDist:Number = 700; function Vector3d(x:Number, y:Number, z:Number){ this.x = x; this.y = y; this.z = z; } public function project2DNew():Vector { var p:Number = getPerspective(); return new Vector(p * x, p * y); } public function getPerspective():Number{ return viewDist / (this.z + viewDist); } }

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  • accessing nth element (value) of a vector after sorting

    - by memC
    dear experts, This question is an extension of this question I asked. I have a std::vector vec_B.which stores instances of class Foo. The order of elements in this vector changes in the code. Now, I want to access the value of the current "last element" or current 'nth' element of the vector. If I use the code below to get the last element using getLastFoo() method, it doesn't return the correct value. For example, to begin with the last element of the vector has Foo.getNumber() = 9. After sorting it in descending order of num, for the last element, Foo.getNumber() = 0. But with the code below, it still returns 9.. that means it is still pointing to the original element that was the last element. What change should I make to the code below so that "lastFoo" points to the correct last element? class Foo { public: Foo(int i); ~Foo(){}; int getNum(); private: int num; }; Foo:Foo(int i){ num = i; } int Foo::getNum(){ return num; } class B { public: Foo* getLastFoo(); B(); ~B(){}; private: vector<Foo> vec_B; }; B::B(){ int i; for (i = 0; i< 10; i++){ vec_B.push_back(Foo(i)); } // Do some random changes to the vector vec_B so that elements are reordered. For // example rearrange elements in decreasing order of 'num' //... } Foo* B::getLastFoo(){ &vec_B.back(); }; int main(){ B b; Foo* lastFoo; lastFoo = b.getLastFoo() cout<<lastFoo->getNumber(); return 0; }

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  • resort on a std::vector vs std::insert

    - by Abruzzo Forte e Gentile
    I have a sorted std::vector of relative small size ( from 5 to 20 elements ). I used std::vector since the data is continuous so I have speed because of cache. On a specific point I need to remove an element from this vector. I have now a doubt: which is the fastest way to remove this value between the 2 options below? setting that element to 0 and call sort to reorder: this has complexity but elements are on the same cache line. call erase that will copy ( or memcpy who knows?? ) all elements after it of 1 place ( I need to investigate the behind scense of erase ). Do you know which one is faster? I think that the same approach could be thought about inserting a new element without hitting the max capacity of the vector. Regards AFG

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  • C++ vector insights

    - by Sunscreen
    Hi, I am a little bit frustrated of how to use vectors in C++. I use them widely though I am not exactly certail of how I use them. Below are teh questions? If I have a vector lets say: std::vector<CString> v_strMyVector, with (int)v_strMyVector.size > i can I access the i member: v_strMyVector[i] == "xxxx"; ? (it works, though why?) Do i always need to define an iterator to acces to go to the beginning of the vector, and lop on its members ? What is the purpose of an iterator if I have access to all members of the vector directly (see 1)? Thanks in advance, Sun

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