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• Programmatically creating vector arrows in KML

  - by mettadore

  Does anyone have any practical examples of programmatically drawing icons as vectors in KML? Specifically, I have data with a magnitude and an azimuth at given coordinates, and I would like to have icons (or another graphical element) generated based on these values. Some thoughts on how I might approach it: Image directory (a brute force way): Make an image director of 360 different image files (probably batch rotate a single image) each pointing in a cooresponding azimuth. I've seen things like "Excel to KML," but am looking for code that I can use within a program, rather than a web utility. Issue: Arrow does not contain magnitude context, so that would have to be a label. I'd rather dynamically lengthen the arrow. Line creation in KML: Perhaps create a formula that creates a line with the origin at the coordinate points, with the length of the line proportional to the magnitute, and angled according to azimuth. There would then be two more lines, perhaps 30 degrees or so extending from the end of the previous line to make the arrow head. Issues: Not a separate image icon, so not sure how it would work in KML. Also not sure how easy it would be to generate this algorithm. Separate image generation: Perhaps create a PHP file that uses imagemagick or something similar to dynamically generate a .png file in a similar method to the above, and then link to the icon using the URI "domain.tld/imagegen.php?magnitude=magvalue&azimuth=azmvalue". Issue: Still have the problem of actually writing the algorithm for image generation. So, the question: has anyone else come up with solutions for programmatic vector (rather than merely arrow) generation?

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• AndEngine VS Android's Canvas VS OpenGLES - For rendering a 2D indoor vector map

  - by Orchestrator

  This is a big issue for me I'm trying to figure out for a long time already. I'm working on an application that should include a 2D vector indoor map in it. The map will be drawn out from an .svg file that will specify all the data of the lines, curved lines (path) and rectangles that should be drawn. My main requirement from the map are Support touch events to detect where exactly the finger is touching. Great image quality especially when considering the drawings of curved and diagonal lines (anti-aliasing) Optional but very nice to have - Built in ability to zoom, pan and rotate. So far I tried AndEngine and Android's canvas. With AndEngine I had troubles with implementing anti-aliasing for rendering smooth diagonal lines or drawing curved lines, and as far as I understand, this is not an easy thing to implement in AndEngine. Though I have to mention that AndEngine's ability to zoom in and pan with the camera instead of modifying the objects on the screen was really nice to have. I also had some little experience with the built in Android's Canvas, mainly with viewing simple bitmaps, but I'm not sure if it supports all of these things, and especially if it would provide smooth results. Last but no least, there's the option of just plain OpenGLES 1 or 2, that as far as I understand, with enough work should be able to support all the features I require. However it seems like something that would be hard to implement. And I've never programmed in OpenGL or anything like it, but I'm willing very much to learn. To sum it all up, I need a platform that would provide me with the ability to do the 3 things I mentioned before, but also very important - To allow me to implement this feature as fast as possible. Any kind of answer or suggestion would be very much welcomed as I'm very eager to solve this problem! Thanks!

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• In .NET, What Is Fastest Way to Initialize Multi-Dimensional Array to Non-Default Value

  - by AMissico

  How do I initialize a multi-dimensional array of a primitive type as fast as possible? I am stuck with using multi-dimensional arrays. My problem is performance. The following routine initializes a 100x100 array in approx. 500 ticks. Removing the int.MaxValue initialization results in approx. 180 ticks just for the looping. Approximately 100 ticks to create the array without looping and without initializing to int.MaxValue. Routines similiar to this are called a few tens-of-thousands to several million times. I am open to suggestions on how to optimize this non-default initialization of an array. One idea I had is to use a smaller primitive type when available. For instance, using byte instead of int, saves 100 ticks. I would be happy with this, but I am hoping that I don't have to change the primitive data type. public int[,] CreateArray(Size size) { int[,] array = new int[size.Width, size.Height]; for (int x = 0; x < size.Width; x++) { for (int y = 0; y < size.Height; y++) { array[x, y] = int.MaxValue; } } return array; }

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• Converting Single dimensional vector or array to two dimension in Matlab

  - by pac

  Well I do not know if I used the exact term. I tried to find an answer on the net. Here is what i need: I have a vector a = 1 4 7 2 5 8 3 6 9 If I do a(4) the value is 4. So it is reading first column top to buttom then continuing to next .... I don't know why. However, What I need is to call it using two indices. As row and column: a(3,2)= 4 or even better if i can call it in the following way: a{3}(2)=4 What is this process really called (want to learn) and how to perform in matlab. I thought of a loop. Is there a built in function Thanks a lot Check this: a = 18 18 16 18 18 18 16 0 0 0 16 16 18 0 18 16 0 18 18 16 18 0 18 18 0 16 0 0 0 18 18 0 18 18 16 0 16 0 18 18 >> a(4) ans = 18 >> a(5) ans = 18 >> a(10) ans = 18 I tried reshape. it is reshaping not converting into 2 indeces

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• Caching vector addition over changing collections

  - by DRMacIver

  I have the following setup: I have a largish number of uuids (currently about 10k but expected to grow unboundedly - they're user IDs) and a function f : id - sparse vector with 32-bit integer values (no need to worry about precision). The function is reasonably expensive (not outrageously so, but probably on the order of a few 100ms for a given id). The dimension of the sparse vectors should be assumed to be infinite, as new dimensions can appear over time, but in practice is unlikely to ever exceed about 20k (and individual results of f are unlikely to have more than a few hundred non-zero values). I want to support the following operations efficiently: add a new ID to the collection invalidate an existing ID retrieve sum f(id) in O(changes since last retrieval) i.e. I want to cache the sum of the vectors in a way that's reasonable to do incrementally. One option would be to support a remove ID operation and treat invalidation as a remove followed by an add. The problem with this is that it requires us to keep track of all the old values of f, which is expensive in space. I potentially need to use many instances of this sort of cached structure, so I would like to avoid that. The likely usage pattern is that new IDs are added at a fairly continuous rate and are frequently invalidated at first. Ids which have been invalidated recently are much more likely to be invalidated again than ones which have remained valid for a long time, but in principle an old Id can still be invalidated. Ideally I don't want to do this in memory (or at least I want a way that lets me save the result to disk efficiently), so an idea which lets me piggyback off an existing DB implementation of some sort would be especially appreciated.

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• Fill lower matrix with vector by row, not column

  - by mhermans

  I am trying to read in a variance-covariance matrix written out by LISREL in the following format in a plain text, whitespace separated file: 0.23675E+01 0.86752E+00 0.28675E+01 -0.36190E+00 -0.36190E+00 0.25381E+01 -0.32571E+00 -0.32571E+00 0.84425E+00 0.25598E+01 -0.37680E+00 -0.37680E+00 0.53136E+00 0.47822E+00 0.21120E+01 -0.37680E+00 -0.37680E+00 0.53136E+00 0.47822E+00 0.91200E+00 0.21120E+01 This is actually a lower diagonal matrix (including diagonal): 0.23675E+01 0.86752E+00 0.28675E+01 -0.36190E+00 -0.36190E+00 0.25381E+01 -0.32571E+00 -0.32571E+00 0.84425E+00 0.25598E+01 -0.37680E+00 -0.37680E+00 0.53136E+00 0.47822E+00 0.21120E+01 -0.37680E+00 -0.37680E+00 0.53136E+00 0.47822E+00 0.91200E+00 0.21120E+01 I can read in the values correctly with scan() or read.table(fill=T). I am however not able to correctly store the read-in vector in a matrix. The following code S <- diag(6) S[lower.tri(S,diag=T)] <- d fills the lower matrix by column, while it should fill it by row. Using matrix() does allow for the option byrow=TRUE, but this will fill in the whole matrix, not just the lower half (with diagonal). Is it possible to have both: only fill the lower matrix (with diagonal) and do it by row? (separate issue I'm having: LISREL uses 'D+01' while R only recognises 'E+01' for scientific notation. Can you change this in R to accept also 'D'?)

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• Dynamic Array of Objects Sans Vector Class

  - by Connor Black

  I am doing a homework assignment for my summer OO class and we need to write two classes. One is called Sale and the other is called Register. I've written my Sale class; here's the .h file: enum ItemType {BOOK, DVD, SOFTWARE, CREDIT}; class Sale { public: Sale(); // default constructor, // sets numerical member data to 0 void MakeSale(ItemType x, double amt); ItemType Item(); // Returns the type of item in the sale double Price(); // Returns the price of the sale double Tax(); // Returns the amount of tax on the sale double Total(); // Returns the total price of the sale void Display(); // outputs sale info private: double price; // price of item or amount of credit double tax; // amount of sales tax double total; // final price once tax is added in. ItemType item; // transaction type }; For the Register class we need to include a dynamic array of Sale objects in our member data. We cannot use the vector class. How is this done? Here's my 'Register' '.h' class Register{ public: Register(int ident, int amount); ~Register(); int GetID(){return identification;} int GetAmount(){return amountMoney;} void RingUpSale(ItemType item, int basePrice); void ShowLast(); void ShowAll(); void Cancel(); int SalesTax(int n); private: int identification; int amountMoney; };

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• Convert binary unsigned vector to dec list

  - by Juan

  This code convert a unsigned long vector variable cR1 to NB_ERRORS numbers (in 'a' variable I print these numbers). for (l = 0; l < NB_ERRORS; ++l) { k = (l * EXT_DEGREE) / BIT_SIZE_OF_LONG; j = (l * EXT_DEGREE) % BIT_SIZE_OF_LONG; a = cR1[k] >> j; if(j + EXT_DEGREE > BIT_SIZE_OF_LONG) a ^= cR1[k + 1] << (BIT_SIZE_OF_LONG - j); a &= ((1 << EXT_DEGREE) - 1); printf("\na=%d\n",a); } For example I am have a cR1 with two elements that follow: 0,0,1,1,0,1,0,0,0,0,1,0,0,1,1,1,1,1,0,0,1,1,1,1,0,0,0,1,1,0,0,0,1,0,1,1,0,0,1,0,1,1,1,0,0,1,0,0,1,0,1,0,1,1,1,0,1,0,0,1,1,1,1,0, executing that code I get (44), (228, (243), (24), (77), (39), (117), (121). This code convert from right to left, I want modify to convert from right to left, Where I will be able to modify this? pdta: In the example case EXT_DEGREE = 8, BIT_SIZE_OF_LONG = 32

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• WPF 3D extrude "a bitmap"

  - by Bgnt44

  Hi, I'm looking for a way to simulate a projector in wpf 3D : i've these "in" parameters : beam shape : a black and white bitmap file beam size ( ex : 30 °) beam color beam intensity ( dimmer ) projector position (x,y,z) beam position (pan(x),tilt(y) relative to projector) First i was thinking of using light object but it seem that wpf can't do that So, now i think that i can make for each projector a polygon from my bitmap... First i need to convert the black and white bitmap to vector. Only Simple shape ( bubble, line,dot,cross ...) Is there any WPF way to do that ? Or maybe a external program file (freeware); then i need to build the polygon, with the shape of the converted bitmap , color , size , orientation in parameter. i don't know how can i defined the lenght of the beam , and if it can be infiny ... To show the beam result, i think of making a room ( floor , wall ...) and beam will end to these wall... i don't care of real light render ( dispersion ...) but the scene render has to be real time and at least 15 times / second (with probably from one to 100 projectors at the same time), information about position, angle,shape,color will be sent for each render... Well so, i need sample for that, i guess that all of these things could be useful for other people If you have sample code : Convert Bitmap to vector Extrude vectors from one point with a angle parameter until collision of a wall Set x,y position of the beam depend of the projector position Set Alpha intensity of the beam, color Maybe i'm totally wrong and WPF is not ready for that , so advise me about other way ( xna,d3D ) with sample of course ;-) Thanks you

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• Diffie-Hellman -- Primitive root mod n -- cryptography question.

  - by somewhat confused

  In the below snippet, please explain starting with the first "for" loop what is happening and why. Why is 0 added, why is 1 added in the second loop. What is going on in the "if" statement under bigi. Finally explain the modPow method. Thank you in advance for meaningful replies. public static boolean isPrimitive(BigInteger m, BigInteger n) { BigInteger bigi, vectorint; Vector<BigInteger> v = new Vector<BigInteger>(m.intValue()); int i; for (i=0;i<m.intValue();i++) v.add(new BigInteger("0")); for (i=1;i<m.intValue();i++) { bigi = new BigInteger("" + i); if (m.gcd(bigi).intValue() == 1) v.setElementAt(new BigInteger("1"), n.modPow(bigi,m).intValue()); } for (i=0;i<m.intValue();i++) { bigi = new BigInteger("" + i); if (m.gcd(bigi).intValue() == 1) { vectorint = v.elementAt(bigi.intValue()); if ( vectorint.intValue() == 0) i = m.intValue() + 1; } } if (i == m.intValue() + 2) return false; else return true; }

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• With Go, how to append unknown number of byte into a vector and get a slice of bytes?

  - by Stephen Hsu

  I'm trying to encode a large number to a list of bytes(uint8 in Go). The number of bytes is unknown, so I'd like to use vector. But Go doesn't provide vector of byte, what can I do? And is it possible to get a slice of such a byte vector? I intends to implement data compression. Instead of store small and large number with the same number of bytes, I'm implements a variable bytes that uses less bytes with small number and more bytes with large number. My code can not compile, invalid type assertion: 1 package main 2 3 import ( 4 //"fmt" 5 "container/vector" 6 ) 7 8 func vbEncodeNumber(n uint) []byte{ 9 bytes := new(vector.Vector) 10 for { 11 bytes.Push(n % 128) 12 if n < 128 { 13 break 14 } 15 n /= 128 16 } 17 bytes.Set(bytes.Len()-1, bytes.Last().(byte)+byte(128)) 18 return bytes.Data().([]byte) // <- 19 } 20 21 func main() { vbEncodeNumber(10000) } I wish to writes a lot of such code into binary file, so I wish the func can return byte array. I haven't find a code example on vector.

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• error C2512 in precompiled header file?

  - by SoloMael

  I'm having a ridiculously strange problem. When I try to run the program below, there's an error message that says: "error C2512: 'Record' : no appropriate default constructor available". And when I double-click it, it directs me to a precompiled read-only header file named "xmemory0". Do they expect me to change a read-only file? Here's the segment of code in the file it directs me to: void construct(_Ty *_Ptr) { // default construct object at _Ptr ::new ((void *)_Ptr) _Ty(); // directs me to this line } Here's the program: #include <iostream> #include <vector> #include <string> using namespace std; const int NG = 4; // number of scores struct Record { string name; // student name int scores[NG]; double average; // Calculate the average // when the scores are known Record(int s[], double a) { double sum = 0; for(int count = 0; count != NG; count++) { scores[count] = s[count]; sum += scores[count]; } average = a; average = sum / NG; } }; int main() { // Names of the class string names[] = {"Amy Adams", "Bob Barr", "Carla Carr", "Dan Dobbs", "Elena Evans"}; // exam scores according to each student int exams[][NG]= { {98, 87, 93, 88}, {78, 86, 82, 91}, {66, 71, 85, 94}, {72, 63, 77, 69}, {91, 83, 76, 60}}; vector<Record> records(5); return 0; }

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• gluLookAt vectors and FPS-style camera

  - by Kevin Pamplona

  I am attempting to implemented an FPS-style camera by updating three vectors: EYE, DIR, UP. These vectors are the same that are used by gluLookAt (since gluLookAt is specified by the position of the camera, the direction it is looking at, and an up vector). I have already implemented the left-right and up-down strafing movements, but I'm having a lot of trouble understanding the math behind making the camera look-around while remaining stationary. In this case, the EYE vector remains the same, while I must update DIR and UP. Below is the code I tried, but it doesn't seem to work properly. Any suggestions? Thanks. void Transform::left(float degrees, vec3& dir, vec3& up) { vec3 axis; axis = glm::normalize(up); mat3 R = rotate(-degrees, axis); dir = R*dir; dir = R*up; }; void Transform::up(float degrees, vec3& dir, vec3& up) { vec3 axis; axis=glm::normalize(glm::cross(dir,up)); mat3 R = rotate(-degrees, axis); dir = R*dir-; up = R*up; };

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• How to animate a path like it's being drawn, dot by dot? (Raphael.js)

  - by Anton

  How to animate a vector path like it's being drawn by hand? In other words, slowly show the path pixel by pixel. I'm using Raphaël.js, but if your answer is not library specific—like maybe there's some general programming pattern for doing that kind of thing (I'm fairly new to vector animation)—it's welcome! Update I know it's easy to do with straight paths, as easy as an example on that page:: path("M114 253").animate({path: "M114 253 L 234 253"}); But try to change code on that page, say, this way:: path("M114 26").animate({path: "M114 26 C 24 23 234 253 234 253"}); And you'll see what I mean. Path is certainly animated from it initial state (point "M114 26") to the end state (curve "C 24 23 234 253 234 253" starting on point "M114 26"), but not in a way specified in question, not like it's being drawn. (Sorry for not making clear from the start that I don't mean animating straight lines.) I don't see how animateAlong can do that either. It can animate an object along a path, and how can I make this path to gradually show itself while object is being animated along it?

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• Firefox extension object instantiating

  - by Michael

  I want my javascript object to be initialized just once, so each new browser window will not create new data items, new functions, etc... usually we initialize the code at the end of main javascript using load window.addEventListener("load", main.onLoad, false); so once the second browser window opened, the initialization code will start from scratch. However, I would like to re-use the existing object on consequent browsers. Any mechanism that I can use?

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• objective-c default init method for class?

  - by Alex

  Hello, I have two differing methods for initializing my objective-c class. One is the default, and one takes a configuration parameter. Now, I'm pretty green when it comes to objective-c, but I've implemented these methods and I'm wondering if there's a better (more correct/in good style) way to handle initialization than the way I have done it. Meaning, did I write these initialization functions in accordance with standards and good style? It just doesn't feel right to check for the existence of selfPtr and then return based on that. Below are my class header and implementation files. Also, if you spot anything else that is wrong or evil, please let me know. I am a C++/Javascript developer who is learning objective-c as hobby and would appreciate any tips that you could offer. #import <Cocoa/Cocoa.h> // class for raising events and parsing returned directives @interface awesome : NSObject { // silence is golden. Actually properties are golden. Hence this emptiness. } // properties @property (retain) SBJsonParser* parser; @property (retain) NSString* eventDomain; @property (retain) NSString* appid // constructors -(id) init; -(id) initWithAppId:(id) input; // destructor -(void) dealloc; @end #import "awesome.h" #import "JSON.h" @implementation awesome - (id) init { if (self = [super init]) { // if init is called directly, just pass nil to AppId contructor variant id selfPtr = [self initWithAppId:nil]; } if (selfPtr) { return selfPtr; } else { return self; } } - (id) initWithAppId:(id) input { if (self = [super init]) { if (input = nil) { input = [[NSString alloc] initWithString:@"a369x123"]; } [self setAppid:input]; [self setEventDomain:[[NSString alloc] initWithString:@"desktop"]]; } return self; } // property synthesis @synthesize parser; @synthesize appid; @synthesize eventDomain; // destructor - (void) dealloc { self.parser = nil; self.appid = nil; self.eventDomain = nil; [super dealloc]; } @end Thanks!

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• Fixed strptime exception with thread lock, but slows down the program

  - by eWizardII

  I have the following code, which when is running inside of a thread (the full code is here - https://github.com/eWizardII/homobabel/blob/master/lovebird.py) for null in range(0,1): while True: try: with open('C:/Twitter/tweets/user_0_' + str(self.id) + '.json', mode='w') as f: f.write('[') threadLock.acquire() for i, seed in enumerate(Cursor(api.user_timeline,screen_name=self.ip).items(200)): if i>0: f.write(", ") f.write("%s" % (json.dumps(dict(sc=seed.author.statuses_count)))) j = j + 1 threadLock.release() f.write("]") except tweepy.TweepError, e: with open('C:/Twitter/tweets/user_0_' + str(self.id) + '.json', mode='a') as f: f.write("]") print "ERROR on " + str(self.ip) + " Reason: ", e with open('C:/Twitter/errors_0.txt', mode='a') as a_file: new_ii = "ERROR on " + str(self.ip) + " Reason: " + str(e) + "\n" a_file.write(new_ii) break Now without the thread lock I generate the following error: Exception in thread Thread-117: Traceback (most recent call last): File "C:\Python27\lib\threading.py", line 530, in __bootstrap_inner self.run() File "C:/Twitter/homobabel/lovebird.py", line 62, in run for i, seed in enumerate(Cursor(api.user_timeline,screen_name=self.ip).items(200)): File "build\bdist.win-amd64\egg\tweepy\cursor.py", line 110, in next self.current_page = self.page_iterator.next() File "build\bdist.win-amd64\egg\tweepy\cursor.py", line 85, in next items = self.method(page=self.current_page, *self.args, **self.kargs) File "build\bdist.win-amd64\egg\tweepy\binder.py", line 196, in _call return method.execute() File "build\bdist.win-amd64\egg\tweepy\binder.py", line 182, in execute result = self.api.parser.parse(self, resp.read()) File "build\bdist.win-amd64\egg\tweepy\parsers.py", line 75, in parse result = model.parse_list(method.api, json) File "build\bdist.win-amd64\egg\tweepy\models.py", line 38, in parse_list results.append(cls.parse(api, obj)) File "build\bdist.win-amd64\egg\tweepy\models.py", line 49, in parse user = User.parse(api, v) File "build\bdist.win-amd64\egg\tweepy\models.py", line 86, in parse setattr(user, k, parse_datetime(v)) File "build\bdist.win-amd64\egg\tweepy\utils.py", line 17, in parse_datetime date = datetime(*(time.strptime(string, '%a %b %d %H:%M:%S +0000 %Y')[0:6])) File "C:\Python27\lib\_strptime.py", line 454, in _strptime_time return _strptime(data_string, format)[0] File "C:\Python27\lib\_strptime.py", line 300, in _strptime _TimeRE_cache = TimeRE() File "C:\Python27\lib\_strptime.py", line 188, in __init__ self.locale_time = LocaleTime() File "C:\Python27\lib\_strptime.py", line 77, in __init__ raise ValueError("locale changed during initialization") ValueError: locale changed during initialization The problem is with thread lock on, each thread runs itself serially basically, and it takes way to long for each loop to run for there to be any advantage to having a thread anymore. So if there isn't a way to get rid of the thread lock, is there a way to have it run the for loop inside of the try statement faster?

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• why we can't initialize a servlet using constructor itself?

  - by Reddy

  Why do we have to override init() method in Servlets while we can do the initialization in the constructor and have web container call the constructor passing ServletConfig reference to servlet while calling constructor? Ofcourse container has to use reflection for this but container has to use reflection anyway to call a simple no-arg constructor

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• Incorrect results for frustum cull

  - by DeadMG

  Previously, I had a problem with my frustum culling producing too optimistic results- that is, including many objects that were not in the view volume. Now I have refactored that code and produced a cull that should be accurate to the actual frustum, instead of an axis-aligned box approximation. The problem is that now it never returns anything to be in the view volume. As the mathematical support library I'm using does not provide plane support functions, I had to code much of this functionality myself, and I'm not really the mathematical type, so it's likely that I've made some silly error somewhere. As follows is the relevant code: class Plane { public: Plane() { r0 = Math::Vector(0,0,0); normal = Math::Vector(0,1,0); } Plane(Math::Vector p1, Math::Vector p2, Math::Vector p3) { r0 = p1; normal = Math::Cross((p2 - p1), (p3 - p1)); } Math::Vector r0; Math::Vector normal; }; This class represents one plane as a point and a normal vector. class Frustum { public: Frustum( const std::array<Math::Vector, 8>& points ) { planes[0] = Plane(points[0], points[1], points[2]); planes[1] = Plane(points[4], points[5], points[6]); planes[2] = Plane(points[0], points[1], points[4]); planes[3] = Plane(points[2], points[3], points[6]); planes[4] = Plane(points[0], points[2], points[4]); planes[5] = Plane(points[1], points[3], points[5]); } Plane planes[6]; }; The points are passed in order where (the inverse of) each bit of the index of each point indicates whether it's the left, top, and back of the frustum, respectively. As such, I just picked any three points where they all shared one bit in common to define the planes. My intersection test is as follows (based on this): bool Intersects(Math::AABB lhs, const Frustum& rhs) const { for(int i = 0; i < 6; i++) { Math::Vector pvertex = lhs.TopRightFurthest; Math::Vector nvertex = lhs.BottomLeftClosest; if (rhs.planes[i].normal.x <= -0.0f) { std::swap(pvertex.x, nvertex.x); } if (rhs.planes[i].normal.y <= -0.0f) { std::swap(pvertex.y, nvertex.y); } if (rhs.planes[i].normal.z <= -0.0f) { std::swap(pvertex.z, nvertex.z); } if (Math::Dot(rhs.planes[i].r0, nvertex) < 0.0f) { return false; } } return true; } Also of note is that because I'm using a left-handed co-ordinate system, I wrote my Cross function to return the negative of the formula given on Wikipedia. Any suggestions as to where I've made a mistake?

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• Does reserving capacity incur two allocations or just one?

  - by FredOverflow

  std::vector<T> vec; // line #1 vec.reserve(100); // line #2 I am wondering if line #1 triggers a small allocation (say, memory for 10 Ts), or if the first allocation happens on line #2. Does the standard say anything about that?

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• Why is shrink_to_fit non-binding?

  - by Roger Pate

  The C++0x FCD states in 23.3.6.2 vector capacity: void shrink_to_fit(); Remarks: shrink_to_fit is a non-binding request to reduce capacity() to size(). [Note: The request is non-binding to allow latitude for implementation-specific optimizations. —end note] Why is it non-binding, and what optimizations are intended to be allowed?

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• Formatted input in c++

  - by julz666

  hey, i'm a noob to c++ (and coding in general) i'm looking for an easy way to take two doubles (at once) from the keyboard and store them in a struct i've created called "Point" and then ultimately store the Point into a vector of Points that's a member of a class (called "Polygon"). i know i could do it with a scanf but need to know how to do it with cin. hope that makes sense. thanks in advance julz

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• XSL Transform SVG to VML

  - by kzh

  I don't know anything about VML except that Internet Explorer and other Microsoft products use it and that it is a vector graphics format. Can one use XSLT to transform an SVG document to VML? Or are they too different from one another to make this possible? I know that there exist XSLT documents to transform SVG to XAML.

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• C++: Accessing std::map keys and values

  - by Jay

  How do you access an std::vector of the keys or values of an std::map? Thanks. Edit: I would like to access the actual elements, not just copies of their contents. essentially I want a reference, not a copy. This is essentially what I am wanting to do: std::map<std::string, GLuint> textures_map; // fill map glGenTextures( textures_map.size(), &textures_map.access_values_somehow[0] );

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• Calculating the Angle Between Two vectors Using Dot Product

  - by P. Avery

  I'm trying to calculate the angle between two vectors so that I can rotate a character in the direction of an object in 3D space. I have two vectors( character & object), loc_look, and modelPos respectively. For simplicity's sake I am only trying to rotate along the up axis...yaw. loc_look = D3DXVECTOR3 (0, 0, 1), modelPos = D3DXVECTOR3 (0, 0, 15); I have written this code which seems to be the correct calculations. My problem arises, seemingly, because the rotation I apply to the character's look vector(loc_look) exceeds the value of the object's position (modelPos). Here is my code: BOOL CEntity::TARGET() { if(graphics.m_model->m_enemy) { D3DXVECTOR3 modelPos = graphics.m_model->position; D3DXVec3Normalize(&modelPos, &modelPos); //D3DXVec3Normalize(&loc_look, &loc_look); float dot = D3DXVec3Dot(&loc_look, &modelPos); float yaw = acos(dot); BOOL neg = (loc_look.x > modelPos.x) ? true : false; switch ( neg ) { case false: Yaw(yaw); return true; case true: Yaw(-yaw); return true; } } else return false; } I rotate the character's orientation matrix with the following code: void CEntity::CalculateOrientationMatrix(D3DXMATRIX *orientationMatrix) { D3DXMatrixRotationAxis(&rotY, &loc_up, loc_yaw); D3DXVec3TransformCoord(&loc_look, &loc_look, &rotY); D3DXVec3TransformCoord(&loc_right, &loc_right, &rotY); D3DXMatrixRotationAxis(&rotX, &loc_right, loc_pitch); D3DXVec3TransformCoord(&loc_look, &loc_look, &rotX); D3DXVec3TransformCoord(&loc_up, &loc_up, &rotX); D3DXMatrixRotationAxis(&rotZ, &loc_look, loc_roll); D3DXVec3TransformCoord(&loc_up, &loc_up, &rotZ); D3DXVec3TransformCoord(&loc_right, &loc_right, &rotZ); *orientationMatrix *= rotX * rotY * rotZ; orientationMatrix->_41 = loc_position.x; orientationMatrix->_42 = loc_position.y; orientationMatrix->_43 = loc_position.z; //D3DXVec3Normalize(&loc_look, &loc_look); SetYawPitchRoll(0,0,0); // Reset Yaw, Pitch, & Roll Amounts } Also to note, the modelPos.x increases by 0.1 each iteration so the character will face the object as it moves along the x-axis... Now, when I run program, in the first iteration everything is fine(I haven't rotated the character yet). On the second iteration, the loc_look.x value is greater than the modelPos.x value(I rotated the character too much using the angle specified with the dot product calculations in the TARGET function). Therefore on the second iteration my code will rotate the character left to adjust for the difference in the vectors' x values... How can I tighten up the measurements so that I do not rotate my character's look vector by too great a value?

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