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Search found 614 results on 25 pages for 'vectors'.

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  • writing an autopilot for a 2d game with newtonian physics

    - by Jargo
    The subject says it all. I am making a 2d space game with newtonian physics and I need pointers on how to write an autopilot for it. The requirements are best explained by an example. There is a target object which has speed- and position-vectors and there a spaceship that is controlled by the autopilot. This spaceship also have speed, position and maximum acceleration. The autopilot needs to control the ship that it either collides with the target, Or intercepts the target so that the ship has matching speed and position with the target. Could someone give me some pointers how to achieve this behavior or perhaps even an ready implementation? I am sure someone has written something like this before and there is no point in reinventing the wheel.

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  • Why does my FPS drop gradually over time?

    - by mmankt
    I'm working on this game: yt alpha preview I came into a huge game-breaking problem - after 10-15 min of gameplay the FPS drops from 60 to 30 and is very unstable. I'm using tons of physics and particles, I'm deleting and nulling everything I can after it's supposed to be removed, I remove objects from vectors etc. The memory usage is stable at around 150mb so a leak is unlikely (or invisible?)- after a round ends and I delete everything, play a new round and performance is still terrible. I spent two days trying to figure this out and I just can't fix it. Maybe I'm missing something? I know it's hard to help with no code but I would just have to post my whole source.

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  • How can I stop pixel seams appearing in adjacent mesh boundaries due to floating point imprecision?

    - by ufomorace
    Graphics cards are mathematically imprecise. So when some meshes are joined by their borders, the graphics card often makes mistakes and decides that some pixels at the seam represent neither object, and unwanted pixels appear. It's a natural behaviour on all graphics cards. How are such worries avoided in Pro Games? Batching? Shaders? Different tangent vectors? Merging? Overlaping seams? Dark backgrounds? Extra vertices at borders? Z precision? Camera distance tweaks? Screencap of a fix that ended up not working:

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  • How do professional games avoid showing pixel seams in adjacent mesh boundaries due to decimal imprecision?

    - by ufomorace
    Graphics cards are mathematically imprecise. So when some meshes are joined by their borders, the graphics card often makes mistakes and decides that some pixels at the seam represent neither object, and unwanted pixels appear. It's a natural behaviour on all graphics cards. How are such worries avoided in Pro Games? Batching? Shaders? Different tangent vectors? Merging? Overlaping seams? Dark backgrounds? Extra vertices at borders? Z precision? Camera distance tweaks? Screencap of a fix that ended up not working:

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  • A separate solution for types, etc?

    - by hayer
    I'm currently in progress updating some engine-code(which does not work, so it is more like creating a engine). I've decided to swap over to SFML(instead of my own crappy renderer, window manager, and audio), Box2d(since I need physics, but have none), and some small utils I've built myself. The problem is that each of the project mentioned over use different types for things like Vector2, etc. So to the question; Is it a good idea to replace box2d and SFML vectors with my own vector class? (Which is one of my better implementations) My idea then was to have a seperate .lib with all my classes that should be shared between all the projects in the solution.

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  • Managing different utility classes between engine and libraries

    - by hayer
    I'm currently in updating some engine code (which does not work, so it is more like creating a engine). I've decided to swap over to SFML (instead of my own crappy renderer, window manager, and audio), Box2D (since I need physics, but have none), and some small utilities I've built myself. The problem is that each of the project mentioned over use different types for things like Vector2, etc. So to the question: is it a good idea to replace Box2D and SFML vectors with my own vector class (which is one of my better implementations)? My idea then was to have a separate .lib with all my classes that should be shared between all the projects in the solution.

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  • Meet-in-the-Middle Atack on an NTRU Private key

    - by Elena Kirshanova
    Hello everyone. I was wondering if anyone could tell me how to represent the enumeration of vectors of privite key f in a Meet-In-the-Middle Attack on an NTRU Private key. I can not understand the example, given here http://securityinnovation.com/cryptolab/pdf/NTRUTech004v2.pdf I'll be very thankful if anyone could show an example in detail.

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  • C++: Appending a vector to a vector

    - by sub
    Assuming I have 2 STL vectors: vector<int> a; vector<int> b; Let's also say the both have around 30 elements. How do I add the vector b to the end of vector a? The dirty way would be iterating through b and adding each element via push_back, though I wouldn't like to do that!

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  • How do I rename an R object?

    - by Milktrader
    I'm using the quantmod package to import financial series data from Yahoo. library(quantmod) getSymbols("^GSPC") [1] "GSPC" I'd like to change the name of object "GSPC" to "SPX". I've tried the rename function in the reshape package, but it only changes the variable names. The "GSPC" object has vectors GSPC.Open, GSPC.High, etc. I'd like my renaming of "GSPC" to "SPX" to also change GSPC.Open to SPX.Open and so on.

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  • How do bezier handles work?

    - by user146780
    On Wikipedia I found information about bezier curves and made a function to generate the inbetween points for a bezier polygon. I noticed that Expression Design uses bezier handles. This allows a circle to be made with 4 points each with a bezier handle. I'm just not sure mathematically how this works in relation with the formula for bezier point at time T. How do these handle vectors work to modify the shape? Basically what's there relation to the bezier formula? Thanks

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  • How can I partition a vector?

    - by Karsten W.
    How can I build a function slice(x, n=2) which would return a list of vectors where each vector except maybe the last has size n, i.e. slice(letters, 10) would return list(c("a", "b", "c", "d", "e", "f", "g", "h", "i", "j"), c("k", "l", "m", "n", "o", "p", "q", "r", "s", "t"), c("u", "v", "w", "x", "y", "z")) ?

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  • Faster Matrix Multiplication in C#

    - by Kyle Lahnakoski
    I have as small c# project that involves matrices. I am processing large amounts of data by splitting it into n-length chunks, treating the chucks as vectors, and multiplying by a Vandermonde** matrix. The problem is, depending on the conditions, the size of the chucks and corresponding Vandermonde** matrix can vary. I have a general solution which is easy to read, but way too slow: public byte[] addBlockRedundancy(byte[] data) { if (data.Length!=numGood) D.error("Expecting data to be just "+numGood+" bytes long"); aMatrix d=aMatrix.newColumnMatrix(this.mod, data); var r=vandermonde.multiplyBy(d); return r.ToByteArray(); }//method This can process about 1/4 megabytes per second on my i5 U470 @ 1.33GHz. I can make this faster by manually inlining the matrix multiplication: int o=0; int d=0; for (d=0; d<data.Length-numGood; d+=numGood) { for (int r=0; r<numGood+numRedundant; r++) { Byte value=0; for (int c=0; c<numGood; c++) { value=mod.Add(value, mod.Multiply(vandermonde.get(r, c), data[d+c])); }//for output[r][o]=value; }//for o++; }//for This can process about 1 meg a second. (Please note the "mod" is performing operations over GF(2^8) modulo my favorite irreducible polynomial.) I know this can get a lot faster: After all, the Vandermonde** matrix is mostly zeros. I should be able to make a routine, or find a routine, that can take my matrix and return a optimized method which will effectively multiply vectors by the given matrix, but faster. Then, when I give this routine a 5x5 Vandermonde matrix (the identity matrix), there is simply no arithmetic to perform, and the original data is just copied. ** Please note: What I use the term "Vandermonde", I actually mean an Identity matrix with some number of rows from the Vandermonde matrix appended (see comments). This matrix is wonderful because of all the zeros, and because if you remove enough rows (of your choosing) to make it square, it is an invertible matrix. And, of course, I would like to use this same routine to convert any one of those inverted matrices into an optimized series of instructions. How can I make this matrix multiplication faster? Thanks! (edited to correct my mistake with Vandermonde matrix)

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  • What C++ pitfalls should I avoid ?

    - by Craig H
    I remember first learning about vectors in the STL and after some time, I wanted to use a vector of bools for one of my projects. After seeing some strange behavior and doing some research, I learned that a vector of bools is not really a vector of bools. Anyone out there have any other common pitfalls to avoid in C++?

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  • .NET Geometry Library

    - by dewald
    Does anyone know of a good (efficient, nice API, etc.) geometry open source library for .NET? Some of the operations needed: Data Structures Vectors (2D and 3D with floats and doubles) Lines (2D and 3D) Rectangles / Squares / Cubes / Boxes Spheres / Circles N-Sided Polygon Matrices (floats and doubles) Algorithms Intersection calculations Area / Volume calculations

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  • IE and Content-disposition inline vs. extension-token

    - by pinkgothic
    Preamble So IE does Mime-Type sniffing. That part's old news. Suggestions of how to combat it tend to be along the lines of 'supply a content-type IE trusts' (i.e. anything that isn't text/plain or application/octet-stream) or 'add extraneous data at the start of the file that is definitely of the type you're serving'. Now, I'm working on an application that has to allow message attachments (like in e-mails), and we want to close up XSS vectors. IE's mime sniffing is one of those vectors - a text/plain file with html content will trigger as html. Recoding isn't an option at this point, changing the attachments the user has provided can only happen if there is absolutely no doubt about the maliciousness of the file - and someone might want to send HTML as text. Now, Microsoft's MSDN article implies the situation might be easier to fix than advertised: If Internet Explorer knows the Content-Type specified and there is no Content-Disposition data, Internet Explorer performs a "MIME sniff," [...] Great! Except I don't have IE nor current means to reliably install it (I realise this is a fairly sad state for a webdeveloper to be in, I hope to fix this soon) and this is grey theory that I can't quite seem to get confirmed one way or the other. Local sources say that line is hogwash - IE will mime sniff anything that is Content-Disposition: inline / <default> and not specific enough for its tastes in -Type. But what about x-* ('extension-token' in the RFC)? Trying to google for how browsers handle Content-Disposition: <extension-token> hasn't yielded anything (though I may just be doing it wrong, my understanding of Google is seriously slipping lately). I found one question that looked promising, but turned out to be a misunderstanding on side of the thread author, meaning that the train of thought was never actually addressed there. Question(s) Does IE really Mime sniff if you expressly pass Content-Disposition: inline? If so: Does anyone here know how browsers handle Content-Disposition: <extension-token>? If they do this in a way that is for my purposes benign, by presuming it to be synonymous with the default (effectively 'inline', though I hear it's not defined anywhere?), is it specific enough for IE not to Mime sniff? Or am I actually shooting myself in the foot by thinking of pursuing this avenue?

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  • Do I need to check capacity before adding an element to a vector in c++ ?

    - by Cassie
    Hi dear all, I am a newbie to c++ STL vectors so sorry for silly questions in advence. :) In my program, I have a vector which needs to store unknown number of elements. Do I have to check if the vector has achieved its max_size before adding an new element to it ? Will a c++ compiler throw an exception automatically when a program tries to add elements to a full vector ? Thank you very much, Cassie

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  • Can't compare the norm of a vector to 1 in matlab

    - by Ian
    I'm trying to find out wether a matrix is orthonormal. I begin by checking if the vectors are normal by doing for j=1:2; if norm(S:,j) ~= 1; return; % Not normal vector end end But when norm returns 1.0000 comparing that to 1 is true and the function returns, which is not what i want. Any ideas? Thx

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  • SSE SIMD Optimization For Loop

    - by Projectile Fish
    I have some code in a loop for(int i = 0; i < n; i++) { u[i] = c * u[i] + s * b[i]; } So, u and b are vectors of the same length, and c and s are scalars. Is this code a good candidate for vectorization for use with SSE in order to get a speedup?

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  • g++ SSE intrinsics dilemma - value from intrinsic "saturates"

    - by Sriram
    Hi, I wrote a simple program to implement SSE intrinsics for computing the inner product of two large (100000 or more elements) vectors. The program compares the execution time for both, inner product computed the conventional way and using intrinsics. Everything works out fine, until I insert (just for the fun of it) an inner loop before the statement that computes the inner product. Before I go further, here is the code: //this is a sample Intrinsics program to compute inner product of two vectors and compare Intrinsics with traditional method of doing things. #include <iostream> #include <iomanip> #include <xmmintrin.h> #include <stdio.h> #include <time.h> #include <stdlib.h> using namespace std; typedef float v4sf __attribute__ ((vector_size(16))); double innerProduct(float* arr1, int len1, float* arr2, int len2) { //assume len1 = len2. float result = 0.0; for(int i = 0; i < len1; i++) { for(int j = 0; j < len1; j++) { result += (arr1[i] * arr2[i]); } } //float y = 1.23e+09; //cout << "y = " << y << endl; return result; } double sse_v4sf_innerProduct(float* arr1, int len1, float* arr2, int len2) { //assume that len1 = len2. if(len1 != len2) { cout << "Lengths not equal." << endl; exit(1); } /*steps: * 1. load a long-type (4 float) into a v4sf type data from both arrays. * 2. multiply the two. * 3. multiply the same and store result. * 4. add this to previous results. */ v4sf arr1Data, arr2Data, prevSums, multVal, xyz; //__builtin_ia32_xorps(prevSums, prevSums); //making it equal zero. //can explicitly load 0 into prevSums using loadps or storeps (Check). float temp[4] = {0.0, 0.0, 0.0, 0.0}; prevSums = __builtin_ia32_loadups(temp); float result = 0.0; for(int i = 0; i < (len1 - 3); i += 4) { for(int j = 0; j < len1; j++) { arr1Data = __builtin_ia32_loadups(&arr1[i]); arr2Data = __builtin_ia32_loadups(&arr2[i]); //store the contents of two arrays. multVal = __builtin_ia32_mulps(arr1Data, arr2Data); //multiply. xyz = __builtin_ia32_addps(multVal, prevSums); prevSums = xyz; } } //prevSums will hold the sums of 4 32-bit floating point values taken at a time. Individual entries in prevSums also need to be added. __builtin_ia32_storeups(temp, prevSums); //store prevSums into temp. cout << "Values of temp:" << endl; for(int i = 0; i < 4; i++) cout << temp[i] << endl; result += temp[0] + temp[1] + temp[2] + temp[3]; return result; } int main() { clock_t begin, end; int length = 100000; float *arr1, *arr2; double result_Conventional, result_Intrinsic; // printStats("Allocating memory."); arr1 = new float[length]; arr2 = new float[length]; // printStats("End allocation."); srand(time(NULL)); //init random seed. // printStats("Initializing array1 and array2"); begin = clock(); for(int i = 0; i < length; i++) { // for(int j = 0; j < length; j++) { // arr1[i] = rand() % 10 + 1; arr1[i] = 2.5; // arr2[i] = rand() % 10 - 1; arr2[i] = 2.5; // } } end = clock(); cout << "Time to initialize array1 and array2 = " << ((double) (end - begin)) / CLOCKS_PER_SEC << endl; // printStats("Finished initialization."); // printStats("Begin inner product conventionally."); begin = clock(); result_Conventional = innerProduct(arr1, length, arr2, length); end = clock(); cout << "Time to compute inner product conventionally = " << ((double) (end - begin)) / CLOCKS_PER_SEC << endl; // printStats("End inner product conventionally."); // printStats("Begin inner product using Intrinsics."); begin = clock(); result_Intrinsic = sse_v4sf_innerProduct(arr1, length, arr2, length); end = clock(); cout << "Time to compute inner product with intrinsics = " << ((double) (end - begin)) / CLOCKS_PER_SEC << endl; //printStats("End inner product using Intrinsics."); cout << "Results: " << endl; cout << " result_Conventional = " << result_Conventional << endl; cout << " result_Intrinsics = " << result_Intrinsic << endl; return 0; } I use the following g++ invocation to build this: g++ -W -Wall -O2 -pedantic -march=i386 -msse intrinsics_SSE_innerProduct.C -o innerProduct Each of the loops above, in both the functions, runs a total of N^2 times. However, given that arr1 and arr2 (the two floating point vectors) are loaded with a value 2.5, the length of the array is 100,000, the result in both cases should be 6.25e+10. The results I get are: Results: result_Conventional = 6.25e+10 result_Intrinsics = 5.36871e+08 This is not all. It seems that the value returned from the function that uses intrinsics "saturates" at the value above. I tried putting other values for the elements of the array and different sizes too. But it seems that any value above 1.0 for the array contents and any size above 1000 meets with the same value we see above. Initially, I thought it might be because all operations within SSE are in floating point, but floating point should be able to store a number that is of the order of e+08. I am trying to see where I could be going wrong but cannot seem to figure it out. I am using g++ version: g++ (GCC) 4.4.1 20090725 (Red Hat 4.4.1-2). Any help on this is most welcome. Thanks, Sriram.

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