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• Perfect Forwarding to async lambda

  - by Alexander Kondratskiy

  I have a function template, where I want to do perfect forwarding into a lambda that I run on another thread. Here is a minimal test case which you can directly compile: #include <thread> #include <future> #include <utility> #include <iostream> #include <vector> /** * Function template that does perfect forwarding to a lambda inside an * async call (or at least tries to). I want both instantiations of the * function to work (one for lvalue references T&, and rvalue reference T&&). * However, I cannot get the code to compile when calling it with an lvalue. * See main() below. */ template <typename T> std::string accessValueAsync(T&& obj) { std::future<std::string> fut = std::async(std::launch::async, [](T&& vec) mutable { return vec[0]; }, std::forward<T>(obj)); return fut.get(); } int main(int argc, char const *argv[]) { std::vector<std::string> lvalue{"Testing"}; // calling with what I assume is an lvalue reference does NOT compile std::cout << accessValueAsync(lvalue) << std::endl; // calling with rvalue reference compiles std::cout << accessValueAsync(std::move(lvalue)) << std::endl; // I want both to compile. return 0; } For the non-compiling case, here is the last line of the error message which is intelligible: main.cpp|13 col 29| note: no known conversion for argument 1 from ‘std::vector<std::basic_string<char> >’ to ‘std::vector<std::basic_string<char> >&’ I have a feeling it may have something to do with how T&& is deduced, but I can't pinpoint the exact point of failure and fix it. Any suggestions? Thank you! EDIT: I am using gcc 4.7.0 just in case this could be a compiler issue (probably not)

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• Quaternion Cameras and projectile vectors

  - by Tom J Nowell

  In our software we have a camera based on mouse movement, and a quarternion at its heart. We want to fire projectiles from this position, which we can do, however we want to use the camera to aim. The projectile takes a vector which it will add to its position each game frame. How do we acquire such a vector from a given camera/quaternion?

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• Best way to have common class shared by both C++ and Ruby?

  - by shuttle87

  I am currently working on a project where a team of us are designing a game, all of us are proficient in ruby and some (but not all) of us are proficient in c++. Initially we made the backend in ruby but we ported it to c++ for more speed. The c++ port of the backend has exactly the same features and algorithms as the original ruby code. However we still have a bunch of code in ruby that does useful things but we want it to now get the data from the c++ classes. Our first thought was that we could save some of the data structures in something like XML or redis and call that, but some of the developers don't like that idea. We don't need anything particularly complex data structures to be passed between the different parts of the code, just tuples, strings and ints. Is there any way of integrating the ruby code so that it can call the c++ stuff natively? Will we need to embed code? Will we have to make a ruby extension? If so are there any good resources/tutorials you could suggest? For example say we have this code in the c++ backend: class The_game{ private: bool printinfo; //print the player diagnostic info at the beginning if true int numplayers; std::vector<Player*> players; string current_action; int action_is_on; // the index of the player in the players array that the action is now on //more code here public: Table(std::vector<Player *> in_players, std::vector<Statistics *> player_stats ,const int in_numplayers); ~Table(); void play_game(); History actions_history; }; class History{ private: int action_sequence_number; std::vector<Action*> hand_actions; public: void print_history(); void add_action(Action* the_action_to_be_added); int get_action_sequence_number(){ return action_sequence_number;} bool history_actions_are_equal(); int last_action_size(int street,int number_of_actions_ago); History(); ~History(); }; Is there any way to natively call something in the actions_history via The_game object in ruby? (The objects in the original ruby code all had the same names and functionality) By this I mean: class MyRubyClass def method1(arg1) puts arg1 self.f() # ... but still available puts cpp_method.the_current_game.actions_history.get_action_sequence_number() end # Constructor: def initialize(arg) puts "In constructor with arg #{arg}" #get the c++ object here and call it cpp_method end end Is this possible? Any advice or suggestions are appreciated.

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• Matlab - Find point of intersection between two vectors

  - by Silv3rSurf

  I have a very simple matlab question. What is the easiest way to find the point of intersection between two vectors. I am not familiar with the various matlab fuctions -- it seems like there should be one for this. For example if I have one vector from (0,0) to (6,6) and another vector from (0,6) to (6,0), I need to determine that they intersect at (3,3) Thanks.

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• length between 2 values

  - by alex

  In R, what is the most efficient way to count the length between 2 values. for example, i have vector x , which are all randomly choose from 1 to 100, how can i find out the length between the first"2" and first"40", x=(1,2,3,4,5,6,7,40,1,2,3,21,4,1,23,4,43,23,4,12,3,43,5,36,3,45,12,31,3,4,23,41,23,5,53,45,3,7,6,36) for this vector, the answer should be 5 and 6

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• How do I calculate the average direction of two vectors

  - by Mike Broughton

  Hi, I am writing and opengl based iphone app and would like to allow a user to translate around a view based on the direction that they move two fingers on the screen. For one finger I know I could just calculate the vector from the start position to the current position of the users finger and then find the unit vector of this to get just the direction, but I don't know how I would do this for two fingers, I don't think adding the components of the vectors and calculating the average would work so I'm pretty much stuck... thanks in advance

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• C++: Syntax error C2061: Unexpected identifier

  - by Rosarch

  What's wrong with this line of code? bar foo(vector<odp> ftw); It produces error C2061: syntax error: identifier 'vector'

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• Can IDL create a contour plot colorbar like this?

  - by Carthage

  At the bottom of this image, you'll see a nice colorbar that matches the colors of the graph correctly: http://stribog.cc.umanitoba.ca/ceos/20100517_00z_prod/ I couldn't find anything that created a color bar with exactly the colors I wanted, it always seemed to involve a spectrum that included colors I didn't use. I have a vector of colors I use for my data. Is there I way I can use that vector to create a color bar with only those colors?

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• Best way to render Tesselated Objects (OpenGL)

  - by user146780

  I'm using the GLUTesselator for Polygons. Right now the vertex callback does glvertex2f and gltex2f. Would it be better simply to collect the verticies from the vertex callback in a std::vector then use gldrawarrays()? Or would this actually be less efficient since it has to put the verts and texture coordinates in a vector? Thanks

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• Best Java thread-safe locking mechanism for collections?

  - by Simon

  What would be the least-slow thread-safe mechanism for controlling multiple accesses to a collection in Java? I am adding objects to the top of a collection and i am very unsure what would be the best performing collection. Would it be a vector or a queue? I originally thought an ArrayList would be fast but i ran some experiments and it was very slow. EDIT: In my insertion testing a Vector delared using volatile seems to be the fastest?

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• Split a binary file into chunks c++

  - by L4nce0

  I've been bashing my head against trying to first divide up a file into chunks, for the purpose of sending over sockets. I can read / write a file easily without splitting it into chunks. The code below runs, works, kinda. It will write a textfile and has a garbage character. Which if this was just for txt, no problem. Jpegs aren't working with said garbage. Been at it for a few days, so I've done my research, and it's time to get some help. I do want to stick strictly to binary readers, as this need to handle any file. I've seen a lot of slick examples out there. (none of them worked for me with jpgs) Mostly something along the lines of while(file)... I subscribe to the, if you know the size, use a for-loop, not a while-loop camp. Thank you for the help!! vector<char*> readFile(const char* fn){ vector<char*> v; ifstream::pos_type size; char * memblock; ifstream file; file.open(fn,ios::in|ios::binary|ios::ate); if (file.is_open()) { size = fileS(fn); file.seekg (0, ios::beg); int bs = size/3; // arbitrary. Actual program will use the socket send size int ws = 0; int i = 0; for(i = 0; i < size; i+=bs){ if(i+bs > size) ws = size%bs; else ws = bs; memblock = new char [ws]; file.read (memblock, ws); v.push_back(memblock); } } else{ exit(-4); } return v; } int main(int argc, char **argv) { vector<char*> v = readFile("foo.txt"); ofstream myFile ("bar.txt", ios::out | ios::binary); for(vector<char*>::iterator it = v.begin(); it!=v.end(); ++it ){ myFile.write(*it,strlen(*it)); } }

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• OpenGL directional light creating black spots

  - by AnonymousDeveloper

  I probably ought to start by saying that I suspect the problem is that one of my vectors is not in the correct "space", but I don't know for sure. I am having a strange problem with a directional light. When I move the camera away from (0.0, 0.0, 0.0) it creates tiny black spots that grow larger as the distance increases. I apologize ahead of time for the length of the code. Vertex shader: #version 410 core in vec3 vf_normal; in vec3 vf_bitangent; in vec3 vf_tangent; in vec2 vf_textureCoordinates; in vec3 vf_vertex; out vec3 tc_normal; out vec3 tc_bitangent; out vec3 tc_tangent; out vec2 tc_textureCoordinates; out vec3 tc_vertex; uniform mat3 vf_m_normal; uniform mat4 vf_m_model; uniform mat4 vf_m_mvp; uniform mat4 vf_m_projection; uniform mat4 vf_m_view; uniform float vf_te_inner; uniform float vf_te_outer; void main() { tc_normal = vf_normal; tc_bitangent = vf_bitangent; tc_tangent = vf_tangent; tc_textureCoordinates = vf_textureCoordinates; tc_vertex = vf_vertex; gl_Position = vf_m_mvp * vec4(vf_vertex, 1.0); } Tessellation Control shader: #version 410 core layout (vertices = 3) out; in vec3 tc_normal[]; in vec3 tc_bitangent[]; in vec3 tc_tangent[]; in vec2 tc_textureCoordinates[]; in vec3 tc_vertex[]; out vec3 te_normal[]; out vec3 te_bitangent[]; out vec3 te_tangent[]; out vec2 te_textureCoordinates[]; out vec3 te_vertex[]; uniform float vf_te_inner; uniform float vf_te_outer; uniform vec4 vf_l_color; uniform vec3 vf_l_position; uniform mat4 vf_m_depthBias; uniform mat4 vf_m_model; uniform mat4 vf_m_mvp; uniform mat4 vf_m_projection; uniform mat4 vf_m_view; uniform sampler2D vf_t_diffuse; uniform sampler2D vf_t_normal; uniform sampler2DShadow vf_t_shadow; uniform sampler2D vf_t_specular; #define ID gl_InvocationID float getTessLevelInner(float distance0, float distance1) { float avgDistance = (distance0 + distance1) / 2.0; return clamp((vf_te_inner - avgDistance), 1.0, vf_te_inner); } float getTessLevelOuter(float distance0, float distance1) { float avgDistance = (distance0 + distance1) / 2.0; return clamp((vf_te_outer - avgDistance), 1.0, vf_te_outer); } void main() { te_normal[gl_InvocationID] = tc_normal[gl_InvocationID]; te_bitangent[gl_InvocationID] = tc_bitangent[gl_InvocationID]; te_tangent[gl_InvocationID] = tc_tangent[gl_InvocationID]; te_textureCoordinates[gl_InvocationID] = tc_textureCoordinates[gl_InvocationID]; te_vertex[gl_InvocationID] = tc_vertex[gl_InvocationID]; float eyeToVertexDistance0 = distance(vec3(0.0), vec4(vf_m_view * vec4(tc_vertex[0], 1.0)).xyz); float eyeToVertexDistance1 = distance(vec3(0.0), vec4(vf_m_view * vec4(tc_vertex[1], 1.0)).xyz); float eyeToVertexDistance2 = distance(vec3(0.0), vec4(vf_m_view * vec4(tc_vertex[2], 1.0)).xyz); gl_TessLevelOuter[0] = getTessLevelOuter(eyeToVertexDistance1, eyeToVertexDistance2); gl_TessLevelOuter[1] = getTessLevelOuter(eyeToVertexDistance2, eyeToVertexDistance0); gl_TessLevelOuter[2] = getTessLevelOuter(eyeToVertexDistance0, eyeToVertexDistance1); gl_TessLevelInner[0] = getTessLevelInner(eyeToVertexDistance2, eyeToVertexDistance0); } Tessellation Evaluation shader: #version 410 core layout (triangles, equal_spacing, cw) in; in vec3 te_normal[]; in vec3 te_bitangent[]; in vec3 te_tangent[]; in vec2 te_textureCoordinates[]; in vec3 te_vertex[]; out vec3 g_normal; out vec3 g_bitangent; out vec4 g_patchDistance; out vec3 g_tangent; out vec2 g_textureCoordinates; out vec3 g_vertex; uniform float vf_te_inner; uniform float vf_te_outer; uniform vec4 vf_l_color; uniform vec3 vf_l_position; uniform mat4 vf_m_depthBias; uniform mat4 vf_m_model; uniform mat4 vf_m_mvp; uniform mat3 vf_m_normal; uniform mat4 vf_m_projection; uniform mat4 vf_m_view; uniform sampler2D vf_t_diffuse; uniform sampler2D vf_t_displace; uniform sampler2D vf_t_normal; uniform sampler2DShadow vf_t_shadow; uniform sampler2D vf_t_specular; vec2 interpolate2D(vec2 v0, vec2 v1, vec2 v2) { return vec2(gl_TessCoord.x) * v0 + vec2(gl_TessCoord.y) * v1 + vec2(gl_TessCoord.z) * v2; } vec3 interpolate3D(vec3 v0, vec3 v1, vec3 v2) { return vec3(gl_TessCoord.x) * v0 + vec3(gl_TessCoord.y) * v1 + vec3(gl_TessCoord.z) * v2; } float amplify(float d, float scale, float offset) { d = scale * d + offset; d = clamp(d, 0, 1); d = 1 - exp2(-2*d*d); return d; } float getDisplacement(vec2 t0, vec2 t1, vec2 t2) { float displacement = 0.0; vec2 textureCoordinates = interpolate2D(t0, t1, t2); vec2 vector = ((t0 + t1 + t2) / 3.0); float sampleDistance = sqrt((vector.x * vector.x) + (vector.y * vector.y)); sampleDistance /= ((vf_te_inner + vf_te_outer) / 2.0); displacement += texture(vf_t_displace, textureCoordinates).x; displacement += texture(vf_t_displace, textureCoordinates + vec2(-sampleDistance, -sampleDistance)).x; displacement += texture(vf_t_displace, textureCoordinates + vec2(-sampleDistance, sampleDistance)).x; displacement += texture(vf_t_displace, textureCoordinates + vec2( sampleDistance, sampleDistance)).x; displacement += texture(vf_t_displace, textureCoordinates + vec2( sampleDistance, -sampleDistance)).x; return (displacement / 5.0); } void main() { g_normal = normalize(interpolate3D(te_normal[0], te_normal[1], te_normal[2])); g_bitangent = normalize(interpolate3D(te_bitangent[0], te_bitangent[1], te_bitangent[2])); g_patchDistance = vec4(gl_TessCoord, (1.0 - gl_TessCoord.y)); g_tangent = normalize(interpolate3D(te_tangent[0], te_tangent[1], te_tangent[2])); g_textureCoordinates = interpolate2D(te_textureCoordinates[0], te_textureCoordinates[1], te_textureCoordinates[2]); g_vertex = interpolate3D(te_vertex[0], te_vertex[1], te_vertex[2]); float displacement = getDisplacement(te_textureCoordinates[0], te_textureCoordinates[1], te_textureCoordinates[2]); float d2 = min(min(min(g_patchDistance.x, g_patchDistance.y), g_patchDistance.z), g_patchDistance.w); d2 = amplify(d2, 50, -0.5); g_vertex += g_normal * displacement * 0.1 * d2; gl_Position = vf_m_mvp * vec4(g_vertex, 1.0); } Geometry shader: #version 410 core layout (triangles) in; layout (triangle_strip, max_vertices = 3) out; in vec3 g_normal[3]; in vec3 g_bitangent[3]; in vec4 g_patchDistance[3]; in vec3 g_tangent[3]; in vec2 g_textureCoordinates[3]; in vec3 g_vertex[3]; out vec3 f_tangent; out vec3 f_bitangent; out vec3 f_eyeDirection; out vec3 f_lightDirection; out vec3 f_normal; out vec4 f_patchDistance; out vec4 f_shadowCoordinates; out vec2 f_textureCoordinates; out vec3 f_vertex; uniform vec4 vf_l_color; uniform vec3 vf_l_position; uniform mat4 vf_m_depthBias; uniform mat4 vf_m_model; uniform mat4 vf_m_mvp; uniform mat3 vf_m_normal; uniform mat4 vf_m_projection; uniform mat4 vf_m_view; uniform sampler2D vf_t_diffuse; uniform sampler2D vf_t_normal; uniform sampler2DShadow vf_t_shadow; uniform sampler2D vf_t_specular; void main() { int index = 0; while (index < 3) { vec3 vertexNormal_cameraspace = vf_m_normal * normalize(g_normal[index]); vec3 vertexTangent_cameraspace = vf_m_normal * normalize(f_tangent); vec3 vertexBitangent_cameraspace = vf_m_normal * normalize(f_bitangent); mat3 TBN = transpose(mat3( vertexTangent_cameraspace, vertexBitangent_cameraspace, vertexNormal_cameraspace )); vec3 eyeDirection = -(vf_m_view * vf_m_model * vec4(g_vertex[index], 1.0)).xyz; vec3 lightDirection = normalize(-(vf_m_view * vec4(vf_l_position, 1.0)).xyz); f_eyeDirection = TBN * eyeDirection; f_lightDirection = TBN * lightDirection; f_normal = normalize(g_normal[index]); f_patchDistance = g_patchDistance[index]; f_shadowCoordinates = vf_m_depthBias * vec4(g_vertex[index], 1.0); f_textureCoordinates = g_textureCoordinates[index]; f_vertex = (vf_m_model * vec4(g_vertex[index], 1.0)).xyz; gl_Position = gl_in[index].gl_Position; EmitVertex(); index ++; } EndPrimitive(); } Fragment shader: #version 410 core in vec3 f_bitangent; in vec3 f_eyeDirection; in vec3 f_lightDirection; in vec3 f_normal; in vec4 f_patchDistance; in vec4 f_shadowCoordinates; in vec3 f_tangent; in vec2 f_textureCoordinates; in vec3 f_vertex; out vec4 fragColor; uniform vec4 vf_l_color; uniform vec3 vf_l_position; uniform mat4 vf_m_depthBias; uniform mat4 vf_m_model; uniform mat4 vf_m_mvp; uniform mat4 vf_m_projection; uniform mat4 vf_m_view; uniform sampler2D vf_t_diffuse; uniform sampler2D vf_t_normal; uniform sampler2DShadow vf_t_shadow; uniform sampler2D vf_t_specular; vec2 poissonDisk[16] = vec2[]( vec2(-0.94201624, -0.39906216), vec2( 0.94558609, -0.76890725), vec2(-0.09418410, -0.92938870), vec2( 0.34495938, 0.29387760), vec2(-0.91588581, 0.45771432), vec2(-0.81544232, -0.87912464), vec2(-0.38277543, 0.27676845), vec2( 0.97484398, 0.75648379), vec2( 0.44323325, -0.97511554), vec2( 0.53742981, -0.47373420), vec2(-0.26496911, -0.41893023), vec2( 0.79197514, 0.19090188), vec2(-0.24188840, 0.99706507), vec2(-0.81409955, 0.91437590), vec2( 0.19984126, 0.78641367), vec2( 0.14383161, -0.14100790) ); float random(vec3 seed, int i) { vec4 seed4 = vec4(seed,i); float dot_product = dot(seed4, vec4(12.9898, 78.233, 45.164, 94.673)); return fract(sin(dot_product) * 43758.5453); } float amplify(float d, float scale, float offset) { d = scale * d + offset; d = clamp(d, 0, 1); d = 1 - exp2(-2.0 * d * d); return d; } void main() { vec3 lightColor = vf_l_color.xyz; float lightPower = vf_l_color.w; vec3 materialDiffuseColor = texture(vf_t_diffuse, f_textureCoordinates).xyz; vec3 materialAmbientColor = vec3(0.1, 0.1, 0.1) * materialDiffuseColor; vec3 materialSpecularColor = texture(vf_t_specular, f_textureCoordinates).xyz; vec3 n = normalize(texture(vf_t_normal, f_textureCoordinates).rgb * 2.0 - 1.0); vec3 l = normalize(f_lightDirection); float cosTheta = clamp(dot(n, l), 0.0, 1.0); vec3 E = normalize(f_eyeDirection); vec3 R = reflect(-l, n); float cosAlpha = clamp(dot(E, R), 0.0, 1.0); float visibility = 1.0; float bias = 0.005 * tan(acos(cosTheta)); bias = clamp(bias, 0.0, 0.01); for (int i = 0; i < 4; i ++) { float shading = (0.5 / 4.0); int index = i; visibility -= shading * (1.0 - texture(vf_t_shadow, vec3(f_shadowCoordinates.xy + poissonDisk[index] / 3000.0, (f_shadowCoordinates.z - bias) / f_shadowCoordinates.w))); }\n" fragColor.xyz = materialAmbientColor + visibility * materialDiffuseColor * lightColor * lightPower * cosTheta + visibility * materialSpecularColor * lightColor * lightPower * pow(cosAlpha, 5); fragColor.w = texture(vf_t_diffuse, f_textureCoordinates).w; } The following images should be enough to give you an idea of the problem. Before moving the camera: Moving the camera just a little. Moving it to the center of the scene.

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• C++/boost generator module, feedback/critic please

  - by aaa

  hello. I wrote this generator, and I think to submit to boost people. Can you give me some feedback about it it basically allows to collapse multidimensional loops to flat multi-index queue. Loop can be boost lambda expressions. Main reason for doing this is to make parallel loops easier and separate algorithm from controlling structure (my fieldwork is computational chemistry where deep loops are common) 1 #ifndef _GENERATOR_HPP_ 2 #define _GENERATOR_HPP_ 3 4 #include <boost/array.hpp> 5 #include <boost/lambda/lambda.hpp> 6 #include <boost/noncopyable.hpp> 7 8 #include <boost/mpl/bool.hpp> 9 #include <boost/mpl/int.hpp> 10 #include <boost/mpl/for_each.hpp> 11 #include <boost/mpl/range_c.hpp> 12 #include <boost/mpl/vector.hpp> 13 #include <boost/mpl/transform.hpp> 14 #include <boost/mpl/erase.hpp> 15 16 #include <boost/fusion/include/vector.hpp> 17 #include <boost/fusion/include/for_each.hpp> 18 #include <boost/fusion/include/at_c.hpp> 19 #include <boost/fusion/mpl.hpp> 20 #include <boost/fusion/include/as_vector.hpp> 21 22 #include <memory> 23 24 /** 25 for loop generator which can use lambda expressions. 26 27 For example: 28 @code 29 using namespace generator; 30 using namespace boost::lambda; 31 make_for(N, N, range(bind(std::max<int>, _1, _2), N), range(_2, _3+1)); 32 // equivalent to pseudocode 33 // for l=0,N: for k=0,N: for j=max(l,k),N: for i=k,j 34 @endcode 35 36 If range is given as upper bound only, 37 lower bound is assumed to be default constructed 38 Lambda placeholders may only reference first three indices. 39 */ 40 41 namespace generator { 42 namespace detail { 43 44 using boost::lambda::constant_type; 45 using boost::lambda::constant; 46 47 /// lambda expression identity 48 template<class E, class enable = void> 49 struct lambda { 50 typedef E type; 51 }; 52 53 /// transform/construct constant lambda expression from non-lambda 54 template<class E> 55 struct lambda<E, typename boost::disable_if< 56 boost::lambda::is_lambda_functor<E> >::type> 57 { 58 struct constant : boost::lambda::constant_type<E>::type { 59 typedef typename boost::lambda::constant_type<E>::type base_type; 60 constant() : base_type(boost::lambda::constant(E())) {} 61 constant(const E &e) : base_type(boost::lambda::constant(e)) {} 62 }; 63 typedef constant type; 64 }; 65 66 /// range functor 67 template<class L, class U> 68 struct range_ { 69 typedef boost::array<int,4> index_type; 70 range_(U upper) : bounds_(typename lambda<L>::type(), upper) {} 71 range_(L lower, U upper) : bounds_(lower, upper) {} 72 73 template< typename T, size_t N> 74 T lower(const boost::array<T,N> &index) { 75 return bound<0>(index); 76 } 77 78 template< typename T, size_t N> 79 T upper(const boost::array<T,N> &index) { 80 return bound<1>(index); 81 } 82 83 private: 84 template<bool b, typename T> 85 T bound(const boost::array<T,1> &index) { 86 return (boost::fusion::at_c<b>(bounds_))(index[0]); 87 } 88 89 template<bool b, typename T> 90 T bound(const boost::array<T,2> &index) { 91 return (boost::fusion::at_c<b>(bounds_))(index[0], index[1]); 92 } 93 94 template<bool b, typename T, size_t N> 95 T bound(const boost::array<T,N> &index) { 96 using boost::fusion::at_c; 97 return (at_c<b>(bounds_))(index[0], index[1], index[2]); 98 } 99 100 boost::fusion::vector<typename lambda<L>::type, 101 typename lambda<U>::type> bounds_; 102 }; 103 104 template<typename T, size_t N> 105 struct for_base { 106 typedef boost::array<T,N> value_type; 107 virtual ~for_base() {} 108 virtual value_type next() = 0; 109 }; 110 111 /// N-index generator 112 template<typename T, size_t N, class R, class I> 113 struct for_ : for_base<T,N> { 114 typedef typename for_base<T,N>::value_type value_type; 115 typedef R range_tuple; 116 for_(const range_tuple &r) : r_(r), state_(true) { 117 boost::fusion::for_each(r_, initialize(index)); 118 } 119 /// @return new generator 120 for_* new_() { return new for_(r_); } 121 /// @return next index value and increment 122 value_type next() { 123 value_type next; 124 using namespace boost::lambda; 125 typename value_type::iterator n = next.begin(); 126 typename value_type::iterator i = index.begin(); 127 boost::mpl::for_each<I>(*(var(n))++ = var(i)[_1]); 128 129 state_ = advance<N>(r_, index); 130 return next; 131 } 132 /// @return false if out of bounds, true otherwise 133 operator bool() { return state_; } 134 135 private: 136 /// initialize indices 137 struct initialize { 138 value_type &index_; 139 mutable size_t i_; 140 initialize(value_type &index) : index_(index), i_(0) {} 141 template<class R_> void operator()(R_& r) const { 142 index_[i_++] = r.lower(index_); 143 } 144 }; 145 146 /// advance index[0:M) 147 template<size_t M> 148 struct advance { 149 /// stop recursion 150 struct stop { 151 stop(R r, value_type &index) {} 152 }; 153 /// advance index 154 /// @param r range tuple 155 /// @param index index array 156 advance(R &r, value_type &index) : index_(index), i_(0) { 157 namespace fusion = boost::fusion; 158 index[M-1] += 1; // increment index 159 fusion::for_each(r, *this); // update indices 160 state_ = index[M-1] >= fusion::at_c<M-1>(r).upper(index); 161 if (state_) { // out of bounds 162 typename boost::mpl::if_c<(M > 1), 163 advance<M-1>, stop>::type(r, index); 164 } 165 } 166 /// apply lower bound of range to index 167 template<typename R_> void operator()(R_& r) const { 168 if (i_ >= M) index_[i_] = r.lower(index_); 169 ++i_; 170 } 171 /// @return false if out of bounds, true otherwise 172 operator bool() { return state_; } 173 private: 174 value_type &index_; ///< index array reference 175 mutable size_t i_; ///< running index 176 bool state_; ///< out of bounds state 177 }; 178 179 value_type index; 180 range_tuple r_; 181 bool state_; 182 }; 183 184 185 /// polymorphic generator template base 186 template<typename T,size_t N> 187 struct For : boost::noncopyable { 188 typedef boost::array<T,N> value_type; 189 /// @return next index value and increment 190 value_type next() { return for_->next(); } 191 /// @return false if out of bounds, true otherwise 192 operator bool() const { return for_; } 193 protected: 194 /// reset smart pointer 195 void reset(for_base<T,N> *f) { for_.reset(f); } 196 std::auto_ptr<for_base<T,N> > for_; 197 }; 198 199 /// range [T,R) type 200 template<typename T, typename R> 201 struct range_type { 202 typedef range_<T,R> type; 203 }; 204 205 /// range identity specialization 206 template<typename T, class L, class U> 207 struct range_type<T, range_<L,U> > { 208 typedef range_<L,U> type; 209 }; 210 211 namespace fusion = boost::fusion; 212 namespace mpl = boost::mpl; 213 214 template<typename T, size_t N, class R1, class R2, class R3, class R4> 215 struct range_tuple { 216 // full range vector 217 typedef typename mpl::vector<R1,R2,R3,R4> v; 218 typedef typename mpl::end<v>::type end; 219 typedef typename mpl::advance_c<typename mpl::begin<v>::type, N>::type pos; 220 // [0:N) range vector 221 typedef typename mpl::erase<v, pos, end>::type t; 222 // transform into proper range fusion::vector 223 typedef typename fusion::result_of::as_vector< 224 typename mpl::transform<t,range_type<T, mpl::_1> >::type 225 >::type type; 226 }; 227 228 229 template<typename T, size_t N, 230 class R1, class R2, class R3, class R4, 231 class O> 232 struct for_type { 233 typedef typename range_tuple<T,N,R1,R2,R3,R4>::type range_tuple; 234 typedef for_<T, N, range_tuple, O> type; 235 }; 236 237 } // namespace detail 238 239 240 /// default index order, [0:N) 241 template<size_t N> 242 struct order { 243 typedef boost::mpl::range_c<size_t,0, N> type; 244 }; 245 246 /// N-loop generator, 0 < N <= 5 247 /// @tparam T index type 248 /// @tparam N number of indices/loops 249 /// @tparam R1,... range types 250 /// @tparam O index order 251 template<typename T, size_t N, 252 class R1, class R2 = void, class R3 = void, class R4 = void, 253 class O = typename order<N>::type> 254 struct for_ : detail::for_type<T, N, R1, R2, R3, R4, O>::type { 255 typedef typename detail::for_type<T, N, R1, R2, R3, R4, O>::type base_type; 256 typedef typename base_type::range_tuple range_tuple; 257 for_(const range_tuple &range) : base_type(range) {} 258 }; 259 260 /// loop range [L:U) 261 /// @tparam L lower bound type 262 /// @tparam U upper bound type 263 /// @return range 264 template<class L, class U> 265 detail::range_<L,U> range(L lower, U upper) { 266 return detail::range_<L,U>(lower, upper); 267 } 268 269 /// make 4-loop generator with specified index ordering 270 template<typename T, class R1, class R2, class R3, class R4, class O> 271 for_<T, 4, R1, R2, R3, R4, O> 272 make_for(R1 r1, R2 r2, R3 r3, R4 r4, const O&) { 273 typedef for_<T, 4, R1, R2, R3, R4, O> F; 274 return F(F::range_tuple(r1, r2, r3, r4)); 275 } 276 277 /// polymorphic generator template forward declaration 278 template<typename T,size_t N> 279 struct For; 280 281 /// polymorphic 4-loop generator 282 template<typename T> 283 struct For<T,4> : detail::For<T,4> { 284 /// generator with default index ordering 285 template<class R1, class R2, class R3, class R4> 286 For(R1 r1, R2 r2, R3 r3, R4 r4) { 287 this->reset(make_for<T>(r1, r2, r3, r4).new_()); 288 } 289 /// generator with specified index ordering 290 template<class R1, class R2, class R3, class R4, class O> 291 For(R1 r1, R2 r2, R3 r3, R4 r4, O o) { 292 this->reset(make_for<T>(r1, r2, r3, r4, o).new_()); 293 } 294 }; 295 296 } 297 298 299 #endif /* _GENERATOR_HPP_ */

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• Instruments memory leak iphone

  - by dubbeat

  Hi, I posted this problem a few days ago but it was very muddled and my question wasnt very clear so I removed it. I've been digging around and the memory leak is still persiting. Hopefully this attempt will be clearer. First off I've run the static analyzer and it reports no memory leaks. I then ran Instruments and it pointed to a memory leak at this line of code. As far as I can see there is no memory leak. featured=[[UILabel alloc]initWithFrame:CGRectMake(130,15, 200, 15)]; //[featured setFont:[UIFont UIFontboldSystemFontOfSize:20]]; featured.font = [UIFont boldSystemFontOfSize:20]; featured.backgroundColor= [UIColor clearColor]; featured.textColor=[UIColor blackColor]; featured.text= @"Featured Promo"; [self.view addSubview:featured]; [featured release]; featured=nil; If I comment out the above code Instruments reports another memory leak in another block of code where there is no discernible leak. UIButton *populartbutton = [[UIButton buttonWithType:UIButtonTypeRoundedRect]]; populartbutton.frame = CGRectMake(112, 145, 90, 22); // size and position of button [populartbutton setTitle:@"Popular" forState:UIControlStateNormal]; populartbutton.backgroundColor = [UIColor clearColor]; populartbutton.adjustsImageWhenHighlighted = YES; [populartbutton addTarget:self action:@selector(getpopular:) forControlEvents:UIControlEventTouchUpInside]; [self.view addSubview:populartbutton]; Instruments also says Responsible Library = Core Graphics Responsible Frame = open_handle_to_dylib_path This Is the stack trace. 53 Promo start 52 Promo main /Users/..2/main.m:14 51 UIKit UIApplicationMain 50 UIKit -[UIApplication _run] 49 CoreFoundation CFRunLoopRunInMode 48 CoreFoundation CFRunLoopRunSpecific 47 GraphicsServices PurpleEventCallback 46 UIKit _UIApplicationHandleEvent 45 UIKit -[UIApplication sendEvent:] 44 UIKit -[UIApplication handleEvent:withNewEvent:] 43 UIKit -[UIApplication _reportAppLaunchFinished] 42 QuartzCore CA::Transaction::commit() 41 QuartzCore CA::Context::commit_transaction(CA::Transaction*) 40 QuartzCore CALayerLayoutIfNeeded 39 QuartzCore -[CALayer layoutSublayers] 38 UIKit -[UILayoutContainerView layoutSubviews] 37 UIKit -[UINavigationController _startDeferredTransitionIfNeeded] 36 UIKit -[UINavigationController _startTransition:fromViewController:toViewController:] 35 UIKit -[UINavigationController _layoutViewController:] 34 UIKit -[UINavigationController_computeAndApplyScrollContentInsetDeltaForViewController:] 33 UIKit -[UIViewController contentScrollView] 32 UIKit -[UIViewController view] 31 Promo -[FeaturedLevelViewController viewDidLoad] /Users/..s/FeaturedLevelViewController.m:67 // THIS IS MY CLASS WHERE THE CODE SAMPLES ABOVE ARE FROM 30 UIKit -[UILabel initWithFrame:] 29 UIKit -[UILabel _commonInit] 28 UIKit +[UILabel defaultFont] 27 UIKit +[UIFont systemFontOfSize:] 26 GraphicsServices GSFontCreateWithName 25 CoreGraphics CGFontCreateWithName 24 CoreGraphics CGFontCreateWithFontName 23 CoreGraphics CGFontFinderGetDefault 22 CoreGraphics CGFontGetVTable 21 libSystem.B.dylib pthread_once 20 CoreGraphics load_vtable 19 CoreGraphics load_library 18 CoreGraphics CGLibraryLoadFunction 17 CoreGraphics load_function 16 CoreGraphics open_handle_to_dylib_path 15 libSystem.B.dylib dlopen 14 dyld dlopen 13 dyld dyld::link(ImageLoader*, bool, ImageLoader::RPathChain const&) 12 dyld ImageLoader::link(ImageLoader::LinkContext const&, bool, bool, ImageLoader::RPathChain const&) 11 dyld ImageLoader::recursiveLoadLibraries(ImageLoader::LinkContext const&, bool, ImageLoader::RPathChain const&) 10 dyld dyld::libraryLocator(char const*, bool, char const*, ImageLoader::RPathChain const*) 9 dyld dyld::load(char const*, dyld::LoadContext const&) 8 dyld dyld::loadPhase0(char const*, dyld::LoadContext const&, std::vector<char const*, std::allocator<char const*> >*) 7 dyld dyld::loadPhase1(char const*, dyld::LoadContext const&, std::vector<char const*, std::allocator<char const*> >*) 6 dyld dyld::loadPhase3(char const*, dyld::LoadContext const&, std::vector<char const*, std::allocator<char const*> >*) 5 dyld dyld::loadPhase4(char const*, dyld::LoadContext const&, std::vector<char const*, std::allocator<char const*> >*) 4 dyld dyld::loadPhase5(char const*, dyld::LoadContext const&, std::vector<char const*, std::allocator<char const*> >*) 3 dyld dyld::mkstringf(char const*, ...) 2 dyld strdup 1 dyld malloc 0 libSystem.B.dylib malloc I'm really not too sure how to use this information to fix the problem so any guidance would be appreciated. Perhaps the answer is in the trace but I just don't know what to look for? EDIT:: The above stack trace is when running on the simulator. The following is from running on a device. This trace does not point to any of my own classes 23 Promo 0x0 22 libSystem.B.dylib _pthread_body 21 Foundation __NSThread__main__ 20 Foundation +[NSThread exit] 19 libSystem.B.dylib _pthread_exit 18 libSystem.B.dylib _pthread_tsd_cleanup 17 QuartzCore CA::Transaction::release_thread(void*) 16 QuartzCore CA::Transaction::commit() 15 QuartzCore CA::Context::commit_transaction(CA::Transaction*) 14 QuartzCore CALayerDisplayIfNeeded 13 QuartzCore -[CALayer display] 12 QuartzCore -[CALayer _display] 11 QuartzCore CABackingStoreUpdate 10 QuartzCore backing_callback(CGContext*, void*) 9 QuartzCore -[CALayer drawInContext:] 8 UIKit -[UIView(CALayerDelegate) drawLayer:inContext:] 7 UIKit -[UILabel drawRect:] 6 UIKit -[UILabel drawTextInRect:] 5 UIKit -[UILabel _drawTextInRect:baselineCalculationOnly:] 4 UIKit -[NSString(UIStringDrawing) drawAtPoint:forWidth:withFont:lineBreakMode:] 3 UIKit -[NSString(UIStringDrawing) drawAtPoint:forWidth:withFont:lineBreakMode:letterSpacing:includeEmoji:] 2 WebCore WKSetCurrentGraphicsContext 1 WebCore CurrentThreadContext() 0 libSystem.B.dylib calloc

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• Boost::Interprocess Container Container Resizing No Default Constructor

  - by CuppM

  Hi, After combing through the Boost::Interprocess documentation and Google searches, I think I've found the reason/workaround to my issue. Everything I've found, as I understand it, seems to be hinting at this, but doesn't come out and say "do this because...". But if anyone can verify this I would appreciate it. I'm writing a series of classes that represent a large lookup of information that is stored in memory for fast performance in a parallelized application. Because of the size of data and multiple processes that run at a time on one machine, we're using Boost::Interprocess for shared memory to have a single copy of the structures. I looked at the Boost::Interprocess documentation and examples, and they typedef classes for shared memory strings, string vectors, int vector vectors, etc. And when they "use" them in their examples, they just construct them passing the allocator and maybe insert one item that they've constructed elsewhere. Like on this page: http://www.boost.org/doc/libs/1_42_0/doc/html/interprocess/allocators_containers.html So following their examples, I created a header file with typedefs for shared memory classes: namespace shm { namespace bip = boost::interprocess; // General/Utility Types typedef bip::managed_shared_memory::segment_manager segment_manager_t; typedef bip::allocator<void, segment_manager_t> void_allocator; // Integer Types typedef bip::allocator<int, segment_manager_t> int_allocator; typedef bip::vector<int, int_allocator> int_vector; // String Types typedef bip::allocator<char, segment_manager_t> char_allocator; typedef bip::basic_string<char, std::char_traits<char>, char_allocator> string; typedef bip::allocator<string, segment_manager_t> string_allocator; typedef bip::vector<string, string_allocator> string_vector; typedef bip::allocator<string_vector, segment_manager_t> string_vector_allocator; typedef bip::vector<string_vector, string_vector_allocator> string_vector_vector; } Then for one of my lookup table classes, it's defined something like this: class Details { public: Details(const shm::void_allocator & alloc) : m_Ids(alloc), m_Labels(alloc), m_Values(alloc) { } ~Details() {} int Read(BinaryReader & br); private: shm::int_vector m_Ids; shm::string_vector m_Labels; shm::string_vector_vector m_Values; }; int Details::Read(BinaryReader & br) { int num = br.ReadInt(); m_Ids.resize(num); m_Labels.resize(num); m_Values.resize(num); for (int i = 0; i < num; i++) { m_Ids[i] = br.ReadInt(); m_Labels[i] = br.ReadString().c_str(); int count = br.ReadInt(); m_Value[i].resize(count); for (int j = 0; j < count; j++) { m_Value[i][j] = br.ReadString().c_str(); } } } But when I compile it, I get the error: 'boost::interprocess::allocator<T,SegmentManager>::allocator' : no appropriate default constructor available And it's due to the resize() calls on the vector objects. Because the allocator types do not have a empty constructor (they take a const segment_manager_t &) and it's trying to create a default object for each location. So in order for it to work, I have to get an allocator object and pass a default value object on resize. Like this: int Details::Read(BinaryReader & br) { shm::void_allocator alloc(m_Ids.get_allocator()); int num = br.ReadInt(); m_Ids.resize(num); m_Labels.resize(num, shm::string(alloc)); m_Values.resize(num, shm::string_vector(alloc)); for (int i = 0; i < num; i++) { m_Ids[i] = br.ReadInt(); m_Labels[i] = br.ReadString().c_str(); int count = br.ReadInt(); m_Value[i].resize(count, shm::string(alloc)); for (int j = 0; j < count; j++) { m_Value[i][j] = br.ReadString().c_str(); } } } Is this the best/correct way of doing it? Or am I missing something. Thanks!

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• Routes on a sphere surface - Find geodesic?

  - by CaNNaDaRk

  I'm working with some friends on a browser based game where people can move on a 2D map. It's been almost 7 years and still people play this game so we are thinking of a way to give them something new. Since then the game map was a limited plane and people could move from (0, 0) to (MAX_X, MAX_Y) in quantized X and Y increments (just imagine it as a big chessboard). We believe it's time to give it another dimension so, just a couple of weeks ago, we began to wonder how the game could look with other mappings: Unlimited plane with continous movement: this could be a step forward but still i'm not convinced. Toroidal World (continous or quantized movement): sincerely I worked with torus before but this time I want something more... Spherical world with continous movement: this would be great! What we want Users browsers are given a list of coordinates like (latitude, longitude) for each object on the spherical surface map; browsers must then show this in user's screen rendering them inside a web element (canvas maybe? this is not a problem). When people click on the plane we convert the (mouseX, mouseY) to (lat, lng) and send it to the server which has to compute a route between current user's position to the clicked point. What we have We began writing a Java library with many useful maths to work with Rotation Matrices, Quaternions, Euler Angles, Translations, etc. We put it all together and created a program that generates sphere points, renders them and show them to the user inside a JPanel. We managed to catch clicks and translate them to spherical coords and to provide some other useful features like view rotation, scale, translation etc. What we have now is like a little (very little indeed) engine that simulates client and server interaction. Client side shows points on the screen and catches other interactions, server side renders the view and does other calculus like interpolating the route between current position and clicked point. Where is the problem? Obviously we want to have the shortest path to interpolate between the two route points. We use quaternions to interpolate between two points on the surface of the sphere and this seemed to work fine until i noticed that we weren't getting the shortest path on the sphere surface: We though the problem was that the route is calculated as the sum of two rotations about X and Y axis. So we changed the way we calculate the destination quaternion: We get the third angle (the first is latitude, the second is longitude, the third is the rotation about the vector which points toward our current position) which we called orientation. Now that we have the "orientation" angle we rotate Z axis and then use the result vector as the rotation axis for the destination quaternion (you can see the rotation axis in grey): What we got is the correct route (you can see it lays on a great circle), but we get to this ONLY if the starting route point is at latitude, longitude (0, 0) which means the starting vector is (sphereRadius, 0, 0). With the previous version (image 1) we don't get a good result even when startin point is 0, 0, so i think we're moving towards a solution, but the procedure we follow to get this route is a little "strange" maybe? In the following image you get a view of the problem we get when starting point is not (0, 0), as you can see starting point is not the (sphereRadius, 0, 0) vector, and as you can see the destination point (which is correctly drawn!) is not on the route. The magenta point (the one which lays on the route) is the route's ending point rotated about the center of the sphere of (-startLatitude, 0, -startLongitude). This means that if i calculate a rotation matrix and apply it to every point on the route maybe i'll get the real route, but I start to think that there's a better way to do this. Maybe I should try to get the plane through the center of the sphere and the route points, intersect it with the sphere and get the geodesic? But how? Sorry for being way too verbose and maybe for incorrect English but this thing is blowing my mind! EDIT: This code version is related to the first image: public void setRouteStart(double lat, double lng) { EulerAngles tmp = new EulerAngles ( Math.toRadians(lat), 0, -Math.toRadians(lng)); //set route start Quaternion qtStart.setInertialToObject(tmp); //do other stuff like drawing start point... } public void impostaDestinazione(double lat, double lng) { EulerAngles tmp = new AngoliEulero( Math.toRadians(lat), 0, -Math.toRadians(lng)); qtEnd.setInertialToObject(tmp); //do other stuff like drawing dest point... } public V3D interpolate(double totalTime, double t) { double _t = t/totalTime; Quaternion q = Quaternion.Slerp(qtStart, qtEnd, _t); RotationMatrix.inertialQuatToIObject(q); V3D p = matInt.inertialToObject(V3D.Xaxis.scale(sphereRadius)); //other stuff, like drawing point ... return p; } //mostly taken from a book! public static Quaternion Slerp(Quaternion q0, Quaternion q1, double t) { double cosO = q0.dot(q1); double q1w = q1.w; double q1x = q1.x; double q1y = q1.y; double q1z = q1.z; if (cosO < 0.0f) { q1w = -q1w; q1x = -q1x; q1y = -q1y; q1z = -q1z; cosO = -cosO; } double sinO = Math.sqrt(1.0f - cosO*cosO); double O = Math.atan2(sinO, cosO); double oneOverSinO = 1.0f / senoOmega; k0 = Math.sin((1.0f - t) * O) * oneOverSinO; k1 = Math.sin(t * O) * oneOverSinO; // Interpolate return new Quaternion( k0*q0.w + k1*q1w, k0*q0.x + k1*q1x, k0*q0.y + k1*q1y, k0*q0.z + k1*q1z ); } A little dump of what i get (again check image 1): Route info: Sphere radius and center: 200,000, (0.0, 0.0, 0.0) Route start: lat 0,000 °, lng 0,000 ° @v: (200,000, 0,000, 0,000), |v| = 200,000 Route end: lat 30,000 °, lng 30,000 ° @v: (150,000, 86,603, 100,000), |v| = 200,000 Qt dump: (w, x, y, z), rot. angle°, (x, y, z) rot. axis Qt start: (1,000, 0,000, -0,000, 0,000); 0,000 °; (1,000, 0,000, 0,000) Qt end: (0,933, 0,067, -0,250, 0,250); 42,181 °; (0,186, -0,695, 0,695) Route start: lat 30,000 °, lng 10,000 ° @v: (170,574, 30,077, 100,000), |v| = 200,000 Route end: lat 80,000 °, lng -50,000 ° @v: (22,324, -26,604, 196,962), |v| = 200,000 Qt dump: (w, x, y, z), rot. angle°, (x, y, z) rot. axis Qt start: (0,962, 0,023, -0,258, 0,084); 31,586 °; (0,083, -0,947, 0,309) Qt end: (0,694, -0,272, -0,583, -0,324); 92,062 °; (-0,377, -0,809, -0,450)

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• getline won't let me type, c++

  - by Stijn

  I try to get the name of a game the users chooses and store it in a vector. I use getline so the user can use a space. When I try to type a new game to add it won't let me. It automaticly displays me games library. Please tell me what I do wrong. Problem is at if(action == "add") Here's my code: #include <iostream> #include <string> #include <vector> #include <algorithm> #include <ctime> #include <cstdlib> using namespace std; int main() { vector<string>::const_iterator myIterator; vector<string>::const_iterator iter; vector<string> games; games.push_back("Crysis 2"); games.push_back("GodOfWar 3"); games.push_back("FIFA 12"); cout <<"Welcome to your Games Library.\n"; cout <<"\nThese are your games:\n"; for (iter = games.begin(); iter != games.end(); ++iter) { cout <<*iter <<endl; } //the loop! string action; string newGame; cout <<"\n-Type 'exit' if you want to quit.\n-Type 'add' if you want to add a game.\n-Type 'delete' if you want to delete a game.\n-Type 'find' if you want to search a game.\n-Type 'game' if you don't know what game to play.\n-Type 'show' if you want to view your library."; while (action != "exit") { cout <<"\n\nWhat do you want to do: "; cin >> action; //problem is here if (action == "add") { cout <<"\nType the name of the game you want to add: "; getline (cin, newGame); games.push_back(newGame); for (iter = games.begin(); iter != games.end(); ++iter) { cout <<*iter <<endl; } continue; } else if (action == "show") { cout <<"\nThese are your games:\n"; for (iter = games.begin(); iter != games.end(); ++iter) { cout <<*iter <<endl; } } else if (action == "delete") { cout <<"Type the name of the game you want to delete: "; cin >> newGame; getline (cin, newGame); iter = find(games.begin(), games.end(), newGame); if(iter != games.end()) { games.erase(iter); cout <<"\nGame deleted!"; } else { cout<<"\nGame not found."; } continue; } else if (action == "find") { cout <<"Which game you want to look for in your library: "; cin >> newGame; getline (cin, newGame); iter = find(games.begin(), games.end(), newGame); if (iter != games.end()) { cout << "Game found.\n"; } else { cout << "Game not found.\n"; } continue; } else if (action == "game") { srand(static_cast<unsigned int>(time(0))); random_shuffle(games.begin(), games.end()); cout << "\nWhy don't you play " << games[0]; continue; } else if (action == "quit") { cout <<"\nRemember to have fun while gaming!!\n"; break; } else { cout <<"\nCommand not found"; } } return 0; }

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• Using a boost::fusion::map in boost::spirit::karma

  - by user1097105

  I am using boost spirit to parse some text files into a data structure and now I am beginning to generate text from this data structure (using spirit karma). One attempt at a data structure is a boost::fusion::map (as suggested in an answer to this question). But although I can use boost::spirit::qi::parse() and get data in it easily, when I tried to generate text from it using karma, I failed. Below is my attempt (look especially at the "map_data" type). After some reading and playing around with other fusion types, I found boost::fusion::vector and BOOST_FUSION_DEFINE_ASSOC_STRUCT. I succeeded to generate output with both of them, but they don't seem ideal: in vector you cannot access a member using a name (it is like a tuple) -- and in the other solution, I don't think I need both ways (member name and key type) to access the members. #include <iostream> #include <string> #include <boost/spirit/include/karma.hpp> #include <boost/fusion/include/map.hpp> #include <boost/fusion/include/make_map.hpp> #include <boost/fusion/include/vector.hpp> #include <boost/fusion/include/as_vector.hpp> #include <boost/fusion/include/transform.hpp> struct sb_key; struct id_key; using boost::fusion::pair; typedef boost::fusion::map < pair<sb_key, int> , pair<id_key, unsigned long> > map_data; typedef boost::fusion::vector < int, unsigned long > vector_data; #include <boost/fusion/include/define_assoc_struct.hpp> BOOST_FUSION_DEFINE_ASSOC_STRUCT( (), assocstruct_data, (int, a, sb_key) (unsigned long, b, id_key)) namespace karma = boost::spirit::karma; template <typename X> std::string to_string ( const X& data ) { std::string generated; std::back_insert_iterator<std::string> sink(generated); karma::generate_delimited ( sink, karma::int_ << karma::ulong_, karma::space, data ); return generated; } int main() { map_data d1(boost::fusion::make_map<sb_key, id_key>(234, 35314988526ul)); vector_data d2(boost::fusion::make_vector(234, 35314988526ul)); assocstruct_data d3(234,35314988526ul); std::cout << "map_data as_vector: " << boost::fusion::as_vector(d1) << std::endl; //std::cout << "map_data to_string: " << to_string(d1) << std::endl; //*FAIL No 1* std::cout << "at_key (sb_key): " << boost::fusion::at_key<sb_key>(d1) << boost::fusion::at_c<0>(d1) << std::endl << std::endl; std::cout << "vector_data: " << d2 << std::endl; std::cout << "vector_data to_string: " << to_string(d2) << std::endl << std::endl; std::cout << "assoc_struct as_vector: " << boost::fusion::as_vector(d3) << std::endl; std::cout << "assoc_struct to_string: " << to_string(d3) << std::endl; std::cout << "at_key (sb_key): " << boost::fusion::at_key<sb_key>(d3) << d3.a << boost::fusion::at_c<0>(d3) << std::endl; return 0; } Including the commented line gives lots of pages of compilation errors, among which notably something like: no known conversion for argument 1 from ‘boost::fusion::pair’ to ‘double’ no known conversion for argument 1 from ‘boost::fusion::pair’ to ‘float’ Might it be that to_string needs the values of the map_data, and not the pairs? Though I am not good with templates, I tried to get a vector from a map using transform in the following way template <typename P> struct take_second { typename P::second_type operator() (P p) { return p.second; } }; // ... inside main() pair <char, int> ff(32); std::cout << "take_second (expect 32): " << take_second<pair<char,int>>()(ff) << std::endl; std::cout << "transform map_data and to_string: " << to_string(boost::fusion::transform(d1, take_second<>())); //*FAIL No 2* But I don't know what types am I supposed to give when instantiating take_second and anyway I think there must be an easier way to get (iterate over) the values of a map (is there?) If you answer this question, please also give your opinion on whether using an ASSOC_STRUCT or a map is better.

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• Gradient algororithm produces little white dots

  - by user146780

  I'm working on an algorithm to generate point to point linear gradients. I have a rough, proof of concept implementation done: GLuint OGLENGINEFUNCTIONS::CreateGradient( std::vector<ARGBCOLORF> &input,POINTFLOAT start, POINTFLOAT end, int width, int height,bool radial ) { std::vector<POINT> pol; std::vector<GLubyte> pdata(width * height * 4); std::vector<POINTFLOAT> linearpts; std::vector<float> lookup; float distance = GetDistance(start,end); RoundNumber(distance); POINTFLOAT temp; float incr = 1 / (distance + 1); for(int l = 0; l < 100; l ++) { POINTFLOAT outA; POINTFLOAT OutB; float dirlen; float perplen; POINTFLOAT dir; POINTFLOAT ndir; POINTFLOAT perp; POINTFLOAT nperp; POINTFLOAT perpoffset; POINTFLOAT diroffset; dir.x = end.x - start.x; dir.y = end.y - start.y; dirlen = sqrt((dir.x * dir.x) + (dir.y * dir.y)); ndir.x = static_cast<float>(dir.x * 1.0 / dirlen); ndir.y = static_cast<float>(dir.y * 1.0 / dirlen); perp.x = dir.y; perp.y = -dir.x; perplen = sqrt((perp.x * perp.x) + (perp.y * perp.y)); nperp.x = static_cast<float>(perp.x * 1.0 / perplen); nperp.y = static_cast<float>(perp.y * 1.0 / perplen); perpoffset.x = static_cast<float>(nperp.x * l * 0.5); perpoffset.y = static_cast<float>(nperp.y * l * 0.5); diroffset.x = static_cast<float>(ndir.x * 0 * 0.5); diroffset.y = static_cast<float>(ndir.y * 0 * 0.5); outA.x = end.x + perpoffset.x + diroffset.x; outA.y = end.y + perpoffset.y + diroffset.y; OutB.x = start.x + perpoffset.x - diroffset.x; OutB.y = start.y + perpoffset.y - diroffset.y; for (float i = 0; i < 1; i += incr) { temp = GetLinearBezier(i,outA,OutB); RoundNumber(temp.x); RoundNumber(temp.y); linearpts.push_back(temp); lookup.push_back(i); } for (unsigned int j = 0; j < linearpts.size(); j++) { if(linearpts[j].x < width && linearpts[j].x >= 0 && linearpts[j].y < height && linearpts[j].y >=0) { pdata[linearpts[j].x * 4 * width + linearpts[j].y * 4 + 0] = (GLubyte) j; pdata[linearpts[j].x * 4 * width + linearpts[j].y * 4 + 1] = (GLubyte) j; pdata[linearpts[j].x * 4 * width + linearpts[j].y * 4 + 2] = (GLubyte) j; pdata[linearpts[j].x * 4 * width + linearpts[j].y * 4 + 3] = (GLubyte) 255; } } lookup.clear(); linearpts.clear(); } return CreateTexture(pdata,width,height); } It works as I would expect most of the time, but at certain angles it produces little white dots. I can't figure out what does this. This is what it looks like at most angles (good) http://img9.imageshack.us/img9/5922/goodgradient.png But once in a while it looks like this (bad): http://img155.imageshack.us/img155/760/badgradient.png What could be causing the white dots? Is there maybe also a better way to generate my gradients if no solution is possible for this? Thanks

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• Inspire Geek Love with These Hilarious Geek Valentines

  - by Eric Z Goodnight

  Want to send some Geek Love to that special someone? Why not do it with these elementary school throwback valentines, and win their heart this upcoming Valentine’s day—the geek way! Read on to see the simple method to make your own custom Valentines, as well as download a set of eleven ready-made ones any geek guy or gal should be delighted get. It’s amore! How to Make Custom Valentines A size we’ve used for all of our Valentines is a 3” x 4” at 150 dpi. This is fairly low resolution for print, but makes a great graphic to email. With your new image open, Navigate to Edit > Fill and fill your background layer with a rich, red color (or whatever appeals to you.) By setting “Use” to “Foreground color as shown above, you’ll paint whatever foreground color you have in your color picker. Press to select the text tool. Set a few text objects, using whatever fonts appeal to you. Pixel fonts, like this one, are freely downloadable, and we’ve already shared a great list of Valentines fonts. Copy an image from the internet if you’re confident your sweetie won’t mind a bit of fair use of copyrighted imagery. If they do mind, find yourself some great Creative Commons images. to do a free transform on your image, sizing it to whatever dimensions work best for your design. Right click your newly added image layer in your panel and Choose “Blending Effects” to pick a Layer Style. “Stroke” with this setting adds a black line around your image. Also turning on “Outer Glow” with this setting puts a dark black shadow around the top and bottom (and sides, although they are hidden). Add some more text. Double entendre is recommended. Click and hold down on the “Rectangle Tool” to get the “Custom Shape Tool.” The custom shape tool has useful vector shapes built into it. Find the “Shape” dropdown in the menu to find the heart image. Click and drag to create a vector heart shape in your image. Your layers panel is where you can change the color, if it happens to use the wrong one at first. Click the color swatch in your panel, highlighted in blue above. will transform your vector heart. You can also use it to rotate, if you like. Add some details, like this Power or Standby symbol, which can be found in symbol fonts, taken from images online, or drawn by hand. Your Valentine is now ready to be saved as a JPG or PNG and sent to the object of your affection! Keep reading to see a list of 11 downloadable How-To Geek Valentines, including this one and the three from the header image. Download The HTG Set of Valentines Download the HTG Geek Valentines (ZIP) Download the HTG Geek Valentines (ZIP) When he’s not wooing ladies with Valentines cards, you can email the author at [email protected] with your Photoshop and Graphics questions. Your questions may be featured in a future How-To Geek article! Latest Features How-To Geek ETC Inspire Geek Love with These Hilarious Geek Valentines How to Integrate Dropbox with Pages, Keynote, and Numbers on iPad RGB? CMYK? Alpha? What Are Image Channels and What Do They Mean? How to Recover that Photo, Picture or File You Deleted Accidentally How To Colorize Black and White Vintage Photographs in Photoshop How To Get SSH Command-Line Access to Windows 7 Using Cygwin How to Kid Proof Your Computer’s Power and Reset Buttons Microsoft’s Windows Media Player Extension Adds H.264 Support Back to Google Chrome Android Notifier Pushes Android Notices to Your Desktop Dead Space 2 Theme for Chrome and Iron Carl Sagan and Halo Reach Mashup – We Humans are Capable of Greatness [Video] Battle the Necromorphs Once Again on Your Desktop with the Dead Space 2 Theme for Windows 7

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• Skewed: a rotating camera in a simple CPU-based voxel raycaster/raytracer

  - by voxelizr

  TL;DR -- in my first simple software voxel raycaster, I cannot get camera rotations to work, seemingly correct matrices notwithstanding. The result is skewed: like a flat rendering, correctly rotated, however distorted and without depth. (While axis-aligned ie. unrotated, depth and parallax are as expected.) I'm trying to write a simple voxel raycaster as a learning exercise. This is purely CPU based for now until I figure out how things work exactly -- fow now, OpenGL is just (ab)used to blit the generated bitmap to the screen as often as possible. Now I have gotten to the point where a perspective-projection camera can move through the world and I can render (mostly, minus some artifacts that need investigation) perspective-correct 3-dimensional views of the "world", which is basically empty but contains a voxel cube of the Stanford Bunny. So I have a camera that I can move up and down, strafe left and right and "walk forward/backward" -- all axis-aligned so far, no camera rotations. Herein lies my problem. Screenshot #1: correct depth when the camera is still strictly axis-aligned, ie. un-rotated. Now I have for a few days been trying to get rotation to work. The basic logic and theory behind matrices and 3D rotations, in theory, is very clear to me. Yet I have only ever achieved a "2.5 rendering" when the camera rotates... fish-eyey, bit like in Google Streetview: even though I have a volumetric world representation, it seems --no matter what I try-- like I would first create a rendering from the "front view", then rotate that flat rendering according to camera rotation. Needless to say, I'm by now aware that rotating rays is not particularly necessary and error-prone. Still, in my most recent setup, with the most simplified raycast ray-position-and-direction algorithm possible, my rotation still produces the same fish-eyey flat-render-rotated style looks: Screenshot #2: camera "rotated to the right by 39 degrees" -- note how the blue-shaded left-hand side of the cube from screen #2 is not visible in this rotation, yet by now "it really should"! Now of course I'm aware of this: in a simple axis-aligned-no-rotation-setup like I had in the beginning, the ray simply traverses in small steps the positive z-direction, diverging to the left or right and top or bottom only depending on pixel position and projection matrix. As I "rotate the camera to the right or left" -- ie I rotate it around the Y-axis -- those very steps should be simply transformed by the proper rotation matrix, right? So for forward-traversal the Z-step gets a bit smaller the more the cam rotates, offset by an "increase" in the X-step. Yet for the pixel-position-based horizontal+vertical-divergence, increasing fractions of the x-step need to be "added" to the z-step. Somehow, none of my many matrices that I experimented with, nor my experiments with matrix-less hardcoded verbose sin/cos calculations really get this part right. Here's my basic per-ray pre-traversal algorithm -- syntax in Go, but take it as pseudocode: fx and fy: pixel positions x and y rayPos: vec3 for the ray starting position in world-space (calculated as below) rayDir: vec3 for the xyz-steps to be added to rayPos in each step during ray traversal rayStep: a temporary vec3 camPos: vec3 for the camera position in world space camRad: vec3 for camera rotation in radians pmat: typical perspective projection matrix The algorithm / pseudocode: // 1: rayPos is for now "this pixel, as a vector on the view plane in 3d, at The Origin" rayPos.X, rayPos.Y, rayPos.Z = ((fx / width) - 0.5), ((fy / height) - 0.5), 0 // 2: rotate around Y axis depending on cam rotation. No prob since view plane still at Origin 0,0,0 rayPos.MultMat(num.NewDmat4RotationY(camRad.Y)) // 3: a temp vec3. planeDist is -0.15 or some such -- fov-based dist of view plane from eye and also the non-normalized, "in axis-aligned world" traversal step size "forward into the screen" rayStep.X, rayStep.Y, rayStep.Z = 0, 0, planeDist // 4: rotate this too -- 0,zstep should become some meaningful xzstep,xzstep rayStep.MultMat(num.NewDmat4RotationY(CamRad.Y)) // set up direction vector from still-origin-based-ray-position-off-rotated-view-plane plus rotated-zstep-vector rayDir.X, rayDir.Y, rayDir.Z = -rayPos.X - me.rayStep.X, -rayPos.Y, rayPos.Z + rayStep.Z // perspective projection rayDir.Normalize() rayDir.MultMat(pmat) // before traversal, the ray starting position has to be transformed from origin-relative to campos-relative rayPos.Add(camPos) I'm skipping the traversal and sampling parts -- as per screens #1 through #3, those are "basically mostly correct" (though not pretty) -- when axis-aligned / unrotated.

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• How do I get FEATURE_LEVEL_9_3 to work with shaders in Direct3D11?

  - by Dominic

  Currently I'm going through some tutorials and learning DX11 on a DX10 machine (though I just ordered a new DX11 compatible computer) by means of setting the D3D_FEATURE_LEVEL_ setting to 10_0 and switching the vertex and pixel shader versions in D3DX11CompileFromFile to "vs_4_0" and "ps_4_0" respectively. This works fine as I'm not using any DX11-only features yet. I'd like to make it compatible with DX9.0c, which naively I thought I could do by changing the feature level setting to 9_3 or something and taking the vertex/pixel shader versions down to 3 or 2. However, no matter what I change the vertex/pixel shader versions to, it always fails when I try to call D3DX11CompileFromFile to compile the vertex/pixel shader files when I have D3D_FEATURE_LEVEL_9_3 enabled. Maybe this is due to the the vertex/pixel shader files themselves being incompatible for the lower vertex/pixel shader versions, but I'm not expert enough to say. My shader files are listed below: Vertex shader: cbuffer MatrixBuffer { matrix worldMatrix; matrix viewMatrix; matrix projectionMatrix; }; struct VertexInputType { float4 position : POSITION; float2 tex : TEXCOORD0; float3 normal : NORMAL; }; struct PixelInputType { float4 position : SV_POSITION; float2 tex : TEXCOORD0; float3 normal : NORMAL; }; PixelInputType LightVertexShader(VertexInputType input) { PixelInputType output; // Change the position vector to be 4 units for proper matrix calculations. input.position.w = 1.0f; // Calculate the position of the vertex against the world, view, and projection matrices. output.position = mul(input.position, worldMatrix); output.position = mul(output.position, viewMatrix); output.position = mul(output.position, projectionMatrix); // Store the texture coordinates for the pixel shader. output.tex = input.tex; // Calculate the normal vector against the world matrix only. output.normal = mul(input.normal, (float3x3)worldMatrix); // Normalize the normal vector. output.normal = normalize(output.normal); return output; } Pixel Shader: Texture2D shaderTexture; SamplerState SampleType; cbuffer LightBuffer { float4 ambientColor; float4 diffuseColor; float3 lightDirection; float padding; }; struct PixelInputType { float4 position : SV_POSITION; float2 tex : TEXCOORD0; float3 normal : NORMAL; }; float4 LightPixelShader(PixelInputType input) : SV_TARGET { float4 textureColor; float3 lightDir; float lightIntensity; float4 color; // Sample the pixel color from the texture using the sampler at this texture coordinate location. textureColor = shaderTexture.Sample(SampleType, input.tex); // Set the default output color to the ambient light value for all pixels. color = ambientColor; // Invert the light direction for calculations. lightDir = -lightDirection; // Calculate the amount of light on this pixel. lightIntensity = saturate(dot(input.normal, lightDir)); if(lightIntensity > 0.0f) { // Determine the final diffuse color based on the diffuse color and the amount of light intensity. color += (diffuseColor * lightIntensity); } // Saturate the final light color. color = saturate(color); // Multiply the texture pixel and the final diffuse color to get the final pixel color result. color = color * textureColor; return color; }

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• Computing a normal matrix in conjunction with gluLookAt

  - by Chris Smith

  I have a hand-rolled camera class that converts yaw, pitch, and roll angles into a forward, side, and up vector suitable for calling gluLookAt. Using this camera class I can modify the model-view matrix to move about the 3D world just fine. However, I am having trouble when using this camera class (and associated model-view matrix) when trying to perform directional lighting in my vertex shader. The problem is that the light direction, (0, 1, 0) for example, is relative to where the 'camera is looking' and not the actual world coordinates. (Or is this eye coordinates vs. model coordinates?) I would like the light direction to be unaffected by the camera's viewing direction. For example, when the camera is looking down the Z axis the ground is lit correctly. However, if I point the camera straight at the ground, then it goes dark. This is (I think) because the light direction is parallel with the camera's 'up' vector which is perpendicular with the ground's normal vector. I tried computing the normal matrix without taking the camera's model view into account, but then none of my objects were rotated correctly. Sorry if this sounds vague. I suspect there is a straight forward answer, but I'm not 100% clear on how the normal matrix should be used for transforming vertex normals in my vertex shader. For reference, here is pseudo code for my rendering loop: pMatrix = new Matrix(); pMatrix = makePerspective(...) mvMatrix = new Matrix() camera.apply(mvMatrix); // Calls gluLookAt // Move the object into position. mvMatrix.translatev(position); mvMatrix.rotatef(rotation.x, 1, 0, 0); mvMatrix.rotatef(rotation.y, 0, 1, 0); mvMatrix.rotatef(rotation.z, 0, 0, 1); var nMatrix = new Matrix(); nMatrix.set(mvMatrix.get().getInverse().getTranspose()); // Set vertex shader uniforms. gl.uniformMatrix4fv(shaderProgram.pMatrixUniform, false, new Float32Array(pMatrix.getFlattened())); gl.uniformMatrix4fv(shaderProgram.mvMatrixUniform, false, new Float32Array(mvMatrix.getFlattened())); gl.uniformMatrix4fv(shaderProgram.nMatrixUniform, false, new Float32Array(nMatrix.getFlattened())); // ... gl.drawElements(gl.TRIANGLES, this.vertexIndexBuffer.numItems, gl.UNSIGNED_SHORT, 0); And the corresponding vertex shader: // Attributes attribute vec3 aVertexPosition; attribute vec4 aVertexColor; attribute vec3 aVertexNormal; // Uniforms uniform mat4 uMVMatrix; uniform mat4 uNMatrix; uniform mat4 uPMatrix; // Varyings varying vec4 vColor; // Constants const vec3 LIGHT_DIRECTION = vec3(0, 1, 0); // Opposite direction of photons. const vec4 AMBIENT_COLOR = vec4 (0.2, 0.2, 0.2, 1.0); float ComputeLighting() { vec4 transformedNormal = vec4(aVertexNormal.xyz, 1.0); transformedNormal = uNMatrix * transformedNormal; float base = dot(normalize(transformedNormal.xyz), normalize(LIGHT_DIRECTION)); return max(base, 0.0); } void main(void) { gl_Position = uPMatrix * uMVMatrix * vec4(aVertexPosition, 1.0); float lightWeight = ComputeLighting(); vColor = vec4(aVertexColor.xyz * lightWeight, 1.0) + AMBIENT_COLOR; } Note that I am using WebGL, so if the anser is use glFixThisProblem(...) any pointers on how to re-implement that on WebGL if missing would be appreciated.

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• Improving the running time of Breadth First Search and Adjacency List creation

  - by user45957

  We are given an array of integers where all elements are between 0-9. have to start from the 1st position and reach end in minimum no of moves such that we can from an index i move 1 position back and forward i.e i-1 and i+1 and jump to any index having the same value as index i. Time Limit : 1 second Max input size : 100000 I have tried to solve this problem use a single source shortest path approach using Breadth First Search and though BFS itself is O(V+E) and runs in time the adjacency list creation takes O(n2) time and therefore overall complexity becomes O(n2). is there any way i can decrease the time complexity of adjacency list creation? or is there a better and more efficient way of solving the problem? int main(){ vector<int> v; string str; vector<int> sets[10]; cin>>str; int in; for(int i=0;i<str.length();i++){ in=str[i]-'0'; v.push_back(in); sets[in].push_back(i); } int n=v.size(); if(n==1){ cout<<"0\n"; return 0; } if(v[0]==v[n-1]){ cout<<"1\n"; return 0; } vector<int> adj[100001]; for(int i=0;i<10;i++){ for(int j=0;j<sets[i].size();j++){ if(sets[i][j]>0) adj[sets[i][j]].push_back(sets[i][j]-1); if(sets[i][j]<n-1) adj[sets[i][j]].push_back(sets[i][j]+1); for(int k=j+1;k<sets[i].size();k++){ if(abs(sets[i][j]-sets[i][k])!=1){ adj[sets[i][j]].push_back(sets[i][k]); adj[sets[i][k]].push_back(sets[i][j]); } } } } queue<int> q; q.push(0); int dist[100001]; bool visited[100001]={false}; dist[0]=0; visited[0]=true; int c=0; while(!q.empty()){ int dq=q.front(); q.pop(); c++; for(int i=0;i<adj[dq].size();i++){ if(visited[adj[dq][i]]==false){ dist[adj[dq][i]]=dist[dq]+1; visited[adj[dq][i]]=true; q.push(adj[dq][i]); } } } cout<<dist[n-1]<<"\n"; return 0; }

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• Collision detection via adjacent tiles - sprite too big

  - by BlackMamba

  I have managed to create a collision detection system for my tile-based jump'n'run game (written in C++/SFML), where I check on each update what values the surrounding tiles of the player contain and then I let the player move accordingly (i. e. move left when there is an obstacle on the right side). This works fine when the player sprite is not too big: Given a tile size of 5x5 pixels, my solution worked quite fine with a spritesize of 3x4 and 5x5 pixels. My problem is that I actually need the player to be quite gigantic (34x70 pixels given the same tilesize). When I try this, there seems to be an invisible, notably smaller boundingbox where the player collides with obstacles, the player also seems to shake strongly. Here some images to explain what I mean: Works: http://tinypic.com/r/207lvfr/8 Doesn't work: http://tinypic.com/r/2yuk02q/8 Another example of non-functioning: http://tinypic.com/r/kexbwl/8 (the player isn't falling, he stays there in the corner) My code for getting the surrounding tiles looks like this (I removed some parts to make it better readable): std::vector<std::map<std::string, int> > Game::getSurroundingTiles(sf::Vector2f position) { // converting the pixel coordinates to tilemap coordinates sf::Vector2u pPos(static_cast<int>(position.x/tileSize.x), static_cast<int>(position.y/tileSize.y)); std::vector<std::map<std::string, int> > surroundingTiles; for(int i = 0; i < 9; ++i) { // calculating the relative position of the surrounding tile(s) int c = i % 3; int r = static_cast<int>(i/3); // we subtract 1 to place the player in the middle of the 3x3 grid sf::Vector2u tilePos(pPos.x + (c - 1), pPos.y + (r - 1)); // this tells us what kind of block this tile is int tGid = levelMap[tilePos.y][tilePos.x]; // converts the coords from tile to world coords sf::Vector2u tileRect(tilePos.x*5, tilePos.y*5); // storing all the information std::map<std::string, int> tileDict; tileDict.insert(std::make_pair("gid", tGid)); tileDict.insert(std::make_pair("x", tileRect.x)); tileDict.insert(std::make_pair("y", tileRect.y)); // adding the stored information to our vector surroundingTiles.push_back(tileDict); } // I organise the map so that it is arranged like the following: /* * 4 | 1 | 5 * -- -- -- * 2 | / | 3 * -- -- -- * 6 | 0 | 7 * */ return surroundingTiles; } I then check in a loop through the surrounding tiles, if there is a 1 as gid (indicates obstacle) and then check for intersections with that adjacent tile. The problem I just can't overcome is that I think that I need to store the values of all the adjacent tiles and then check for them. How? And may there be a better solution? Any help is appreciated. P.S.: My implementation derives from this blog entry, I mostly just translated it from Objective-C/Cocos2d.

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