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  • Algorithm to find average position

    - by Simran kaur
    In the given diagram, I have the extreme left and right points, that is -2 and 4 in this case. So, obviously, I can calculate the width which is 6 in this case. What we know: The number of partitions:3 in this case The partition number at at any point i.e which one is 1st,second or third partition (numbered starting from left) What I want: The position of the purple line drawn which is positio of average of a particular partition So, basically I just want a generalized formula to calculate position of the average at any point.

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  • 2D/Isometric map algorithm

    - by Icarus Cocksson
    First of all, I don't have much experience on game development but I do have experience on development. I do know how to make a map, but I don't know if my solution is a normal or a hacky solution. I don't want to waste my time coding things, and realise they're utterly crap and lose my motivation. Let's imagine the following map. (2D - top view - A square) X: 0 to 500 Y: 0 to 500 My character currently stands at X:250,Y:400, somewhere near center of 100px above bottom and I can control him with my keyboard buttons. LEFT button does X--, UP button does Y-- etc. This one is kid's play. I'm asking this because I know there are some engines that automate this task. For example, games like Diablo 3 uses an engine. You can pretty much drag drop a rock to map, and it is automatically being placed here - making player unable to pass through/detect the collision. But what the engine exactly does in the background? Generates a map like mine, places a rock at the center, and checks it like: unmovableObjects = array('50,50'); //we placed a rock at 50,50 location if(Map.hasUnmovableObject(CurrentPlayerX, CurrentPlayerY)) { //unable to move } else { //able to move } My question is: Is this how 2D/Isometric maps are being generated or there is a different and more complex logic behind them?

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  • Need ideas for an algorithm to draw irregular blotchy shapes

    - by Yttermayn
    I'm looking to draw irregular shapes on an x,y grid, and I'd like to come up with a simple, fast method if possible. My only idea so far is to draw a bunch of circles of random sizes very near each other, but at a random distance apart from a more or less central coordinate, then fill in any blank spaces. I realize this is a clunky, inelegant method, hopefully it will give you a rough idea of the kinds of rounded, random blotchy shapesI'm shooting for. Please suggest methods to accomplish this, I'm not so much interested in code. I can noodle that part out myself. Thanks!

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  • What's wrong with this turn to face algorithm?

    - by Chan
    I implement a torpedo object that chases a rotating planet. Specifically, it will turn toward the planet each update. Initially my implement was: void move() { vector3<float> to_target = target - get_position(); to_target.normalize(); position += (to_target * speed); } which works perfectly for torpedo that is a solid sphere. Now my torpedo is actually a model, which has a forward vector, so using this method looks odd because it doesn't actually turn toward but jump toward. So I revised it a bit to get, double get_rotation_angle(vector3<float> u, vector3<float> v) const { u.normalize(); v.normalize(); double cosine_theta = u.dot(v); // domain of arccosine is [-1, 1] if (cosine_theta > 1) { cosine_theta = 1; } if (cosine_theta < -1) { cosine_theta = -1; } return math3d::to_degree(acos(cosine_theta)); } vector3<float> get_rotation_axis(vector3<float> u, vector3<float> v) const { u.normalize(); v.normalize(); // fix linear case if (u == v || u == -v) { v[0] += 0.05; v[1] += 0.0; v[2] += 0.05; v.normalize(); } vector3<float> axis = u.cross(v); return axis.normal(); } void turn_to_face() { vector3<float> to_target = (target - position); vector3<float> axis = get_rotation_axis(get_forward(), to_target); double angle = get_rotation_angle(get_forward(), to_target); double distance = math3d::distance(position, target); gl_matrix_mode(GL_MODELVIEW); gl_push_matrix(); { gl_load_identity(); gl_translate_f(position.get_x(), position.get_y(), position.get_z()); gl_rotate_f(angle, axis.get_x(), axis.get_y(), axis.get_z()); gl_get_float_v(GL_MODELVIEW_MATRIX, OM); } gl_pop_matrix(); move(); } void move() { vector3<float> to_target = target - get_position(); to_target.normalize(); position += (get_forward() * speed); } The logic is simple, I find the rotation axis by cross product, the angle to rotate by dot product, then turn toward the target position each update. Unfortunately, it looks extremely odds since the rotation happens too fast that it always turns back and forth. The forward vector for torpedo is from the ModelView matrix, the third column A: MODELVIEW MATRIX -------------------------------------------------- R U A T -------------------------------------------------- 1 0 0 0 0 1 0 0 0 0 1 0 0 0 0 1 -------------------------------------------------- Any suggestion or idea would be greatly appreciated.

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  • Algorithm to shift the car

    - by Simran kaur
    I have a track that can be divided into n number of tracks and a car as GamObject. The track has transforms such that some part of the track's width lies in negative x axis and other in positive. Requirement: One move should cross one track. On every move(left or right), I want the car to reach exact centre of the next track on either sides i.e left or right. My code: Problem: : Because of negative values , somewhere I am missing out something that is making car move not in desirable positions and that's because of negative values only. variable tracks is the number of tracks the whole track is divided in. variable dist is the total width of the complete track. On left movement: if (Input.GetKeyDown (KeyCode.LeftArrow)) { if (this.transform.position.x < r.renderer.bounds.min.x + box.size.x) { this.transform.position = new Vector3 (r.renderer.bounds.min.x + Mathf.FloorToInt(box.size.x), this.transform.position.y, this.transform.position.z); } else { int tracknumber = Mathf.RoundToInt(dist - transform.position.x)/tracks; float averagedistance = (tracknumber*(dist/tracks) + (tracknumber-1)*(dist/tracks))/2; if(transform.position.x > averagedistoftracks) { amountofmovement = amountofmovement + (transform.position.x - averagedistance); } else { amountofmovement = amountofmovement - (averagedistance - transform.position.x); } this.transform.position = new Vector3 (this.transform.position.x - amountofmovement, this.transform.position.y, this.transform.position.z); } }

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  • Pixel alignment algorithm

    - by user42325
    I have a set of square blocks, I want to draw them in a window. I am sure the coordinates calculation is correct. But on the screen, some squares' edge overlap with other, some are not. I remember the problem is caused by accuracy of pixels. I remember there's a specific topic related to this kind of problem in 2D image rendering. But I don't remember what exactly it is, and how to solve it. Look at this screenshot. Each block should have a fixed width margin. But in the image, the vertical white line have different width.Though, the horizontal lines looks fine.

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  • Switch from Microsofts STL to STLport

    - by Laserallan
    Hi! I'm using quite much STL in performance critical C++ code under windows. One possible "cheap" way to get some extra performance would be to change to a faster STL library. According to this post STLport is faster and uses less memory, however it's a few years old. Has anyone made this change recently and what were your results?

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  • Version of STL optimized for compile time?

    - by anon
    Hi! I'm looking for a variant of the STL (it's okay if it doesn't have all the functionality) that's optimized for short compile times -- I get bothered by long compile times that delay my compile-debug-edit cycle. I'm mainly interested in the containers of the STL: vector/map, and not so much the algorithms. Thanks!

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  • Can I disable min, max in STL?

    - by P-P
    Hi, I use one library which is very important and untouchable. The problem is that library declare min, max function, so when I include STL header in project, they conflict. I want to disable min, max function in STL (like #define NOMNMAX) if I could. If I can't, what would be solution? Thanks, in advance.

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  • printing stl containers with gdb 7.0

    - by Andrei
    I have installed GDB 7.0 and python per the following instructions. In the same manual, there is a mention of this file stl-views-1.0.3.gdb. What confuses me, is where should it be placed in order to enable pretty printing of stl containers. Would someone also explain to me all of this work? Thanks

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  • stl priority queue based on lower value first

    - by russell
    I have a problem with stl priority queue.I want to have the priority queue in the increasing order,which is decreasing by default.Is there any way to do this in priority queue. And what is the complexity of building stl priority queue.If i use quick sort in an array which takes O(nlgn) is its complexity is similar to using priority queue??? Plz someone ans.Advanced thanx.

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  • why no += operator for vectors in stl

    - by Akshay Bhat
    I am curious? What high fundu logic goes behind not implementing: result+=vector1; where both result and vector1 are stl vectors. Note: i know how to implement that bit, but i need to know what logic, the sages who designed STL were using when they chose not to implement this feature?

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  • STL container to pop() by priority?

    - by Pirate for Profit
    I'm writing a thread-pool for Qt as QRunnable doesn't handle event loops in new threads. Not too familiar with STL, what would be the best way to pop() something by priority? Priority should probably be a property of MyRunnable imo, but I can always give that info to an STL container when adding the runnable to the queue.

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  • Efficient algorithm for creating an ideal distribution of groups into containers?

    - by Inshim
    I have groups of students that need to be allocated into classrooms of a fixed capacity (say, 100 chairs in each). Each group must only be allocated to a single classroom, even if it is larger than the capacity (ie there can be an overflow, with students standing up) I need an algorithm to make the allocations with minimum overflows and under-capacity classrooms. A naive algorithm to do this allocation is horrendously slow when having ~200 groups, with a distribution of about half of them being under 20% of the classroom size. Any ideas where I can find at least some good starting point for making this algorithm lightning fast? Thanks!

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  • How much of STL is too much?

    - by Darius Kucinskas
    I am using a lot of STL code with std::for_each, bind, and so on, but I noticed that sometimes STL usage is not good idea. For example if you have a std::vector and want to do one action on each item of the vector, your first idea is to use this: std::for_each(vec.begin(), vec.end(), Foo()) and it is elegant and ok, for a while. But then comes the first set of bug reports and you have to modify code. Now you should add parameter to call Foo(), so now it becomes: std::for_each(vec.begin(), vec.end(), std::bind2nd(Foo(), X)) but that is only temporary solution. Now the project is maturing and you understand business logic much better and you want to add new modifications to code. It is at this point that you realize that you should use old good: for(std::vector::iterator it = vec.begin(); it != vec.end(); ++it) Is this happening only to me? Do you recognise this kind of pattern in your code? Have you experience similar anti-patterns using STL?

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  • How do you use stl's functions like for_each?

    - by thomas-gies
    I started using stl containers because they came in very handy when I needed functionality of a list, set and map and had nothing else available in my programming environment. I did not care much about the ideas behind it. STL documentations were only interesting up to the point where it came to functions, etc. Then I skipped reading and just used the containers. But yesterday, still being relaxed from my holidays, I just gave it a try and wanted to go a bit more the stl way. So I used the transform function (can I have a little bit of applause for me, thank you). From an academic point of view it really looked interesting and it worked. But the thing that boroughs me is that if you intensify the use of those functions, you need 10ks of helper classes for mostly everything you want to do in your code. The hole logic of the program is sliced in tiny pieces. This slicing is not the result of god coding habits. It's just a technical need. Something, that makes my life probably harder not easier. And I learned the hard way, that you should always choose the simplest approach that solves the problem at hand. And I can't see what, for example, the for_each function is doing for me that justifies the use of a helper class over several simple lines of code that sit inside a normal loop so that everybody can see what is going on. I would like to know, what you are thinking about my concerns? Did you see it like I do when you started working this way and have changed your mind when you got used to it? Are there benefits that I overlooked? Or do you just ignore this stuff as I did (and will go an doing it, probably). Thanks. PS: I know that there is a real for_each loop in boost. But I ignore it here since it is just a convenient way for my usual loops with iterators I guess.

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  • Is the STL efficient enough for mobile devices?

    - by mx2
    When it comes to mobile game development on iOS and Android NDK, some developers write their own C++ containers, while others claim that STL is more than adequate for mobile game development (For example, the author of iPhone 3D Programming uses STL rather than Objective-C in his examples. His defense is that STL is no slower than Objective-C). Then there are also mobile developers who abandon C++ entirely and develop games entirely (or mostly) in the C language (C89/C90). What are the benefits and drawbacks of each approach?

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  • Using STL/Boost to initialize a hard-coded set<vector<int> >

    - by Hooked
    Like this question already asked, I'd like to initialize a container using STL where the elements are hard-coded in the cleanest manner possible. In this case, the elements are a doubly nested container: set<vector<int> > A; And I'd like (for example) to put the following values in: A = [[0,0,1],[0,1,0],[1,0,0],[0,0,0]]; C++0x fine, using g++ 4.4.1. STL is preferable as I don't use Boost for any other parts of the code (though I wouldn't mind an example with it!).

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  • STL operator= behavior change with Visual Studio 2010?

    - by augnob
    Hi, I am attempting to compile QtScriptGenerator (gitorious) with Visual Studio 2010 (C++) and have run into a compile error. In searching for a solution, I have seen occasional references to compile breakages introduced since VS2008 due to changes in VS2010's implementation of STL and/or c++0x conformance changes. Any ideas what is happening below, or how I could go about fixing it? If the offending code appeared to be QtScriptGenerator's, I think I would have an easier time fixing it.. but it appears to me that the offending code may be in VS2010's STL implementation and I may be required to create a workaround? PS. I am pretty unfamiliar with templates and STL. I have a background in embedded and console projects where such things have until recently often been avoided to reduce memory consumption and cross-compiler risks. C:\Program Files\Microsoft Visual Studio 10.0\VC\INCLUDE\xutility(275) : error C2679: binary '=' : no operator found which takes a right-hand operand of type 'rpp::pp_output_iterator<_Container>' (or there is no acceptable conversion) with [ _Container=std::string ] c:\qt\qtscriptgenerator\generator\parser\rpp\pp-iterator.h(75): could be 'rpp::pp_output_iterator<_Container> &rpp::pp_output_iterator<_Container>::operator =(const char &)' with [ _Container=std::string ] while trying to match the argument list '(rpp::pp_output_iterator<_Container>, rpp::pp_output_iterator<_Container>)' with [ _Container=std::string ] C:\Program Files\Microsoft Visual Studio 10.0\VC\INCLUDE\xutility(2176) : see reference to function template instantiation '_Iter &std::_Rechecked<_OutIt,_OutIt>(_Iter &,_UIter)' being compiled with [ _Iter=rpp::pp_output_iterator<std::string>, _OutIt=rpp::pp_output_iterator<std::string>, _UIter=rpp::pp_output_iterator<std::string> ] c:\qt\qtscriptgenerator\generator\parser\rpp\pp-internal.h(83) : see reference to function template instantiation '_OutIt std::copy<std::_String_iterator<_Elem,_Traits,_Alloc>,_OutputIterator>(_InIt,_InIt,_OutIt)' being compiled with [ _OutIt=rpp::pp_output_iterator<std::string>, _Elem=char, _Traits=std::char_traits<char>, _Alloc=std::allocator<char>, _OutputIterator=rpp::pp_output_iterator<std::string>, _InIt=std::_String_iterator<char,std::char_traits<char>,std::allocator<char>> ] c:\qt\qtscriptgenerator\generator\parser\rpp\pp-engine-bits.h(500) : see reference to function template instantiation 'void rpp::_PP_internal::output_line<_OutputIterator>(const std::string &,int,_OutputIterator)' being compiled with [ _OutputIterator=rpp::pp_output_iterator<std::string> ] C:\Program Files\Microsoft Visual Studio 10.0\VC\INCLUDE\xutility(275) : error C2582: 'operator =' function is unavailable in 'rpp::pp_output_iterator<_Container>' with [ _Container=std::string ] Here's some context.. pp-internal.h-- #ifndef PP_INTERNAL_H #define PP_INTERNAL_H #include <algorithm> #include <stdio.h> namespace rpp { namespace _PP_internal { .. 68 template <typename _OutputIterator> 69 void output_line(const std::string &__filename, int __line, _OutputIterator __result) 70 { 71 std::string __msg; 72 73 __msg += "# "; 74 75 char __line_descr[16]; 76 pp_snprintf (__line_descr, 16, "%d", __line); 77 __msg += __line_descr; 78 79 __msg += " \""; 80 81 if (__filename.empty ()) 82 __msg += "<internal>"; 83 else 84 __msg += __filename; 85 86 __msg += "\"\n"; 87 std::copy (__msg.begin (), __msg.end (), __result); 88 }

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  • STL find performs bettern than hand-crafter loop

    - by dusha
    Hello all, I have some question. Given the following C++ code fragment: #include <boost/progress.hpp> #include <vector> #include <algorithm> #include <numeric> #include <iostream> struct incrementor { incrementor() : curr_() {} unsigned int operator()() { return curr_++; } private: unsigned int curr_; }; template<class Vec> char const* value_found(Vec const& v, typename Vec::const_iterator i) { return i==v.end() ? "no" : "yes"; } template<class Vec> typename Vec::const_iterator find1(Vec const& v, typename Vec::value_type val) { return find(v.begin(), v.end(), val); } template<class Vec> typename Vec::const_iterator find2(Vec const& v, typename Vec::value_type val) { for(typename Vec::const_iterator i=v.begin(), end=v.end(); i<end; ++i) if(*i==val) return i; return v.end(); } int main() { using namespace std; typedef vector<unsigned int>::const_iterator iter; vector<unsigned int> vec; vec.reserve(10000000); boost::progress_timer pt; generate_n(back_inserter(vec), vec.capacity(), incrementor()); //added this line, to avoid any doubts, that compiler is able to // guess the data is sorted random_shuffle(vec.begin(), vec.end()); cout << "value generation required: " << pt.elapsed() << endl; double d; pt.restart(); iter found=find1(vec, vec.capacity()); d=pt.elapsed(); cout << "first search required: " << d << endl; cout << "first search found value: " << value_found(vec, found)<< endl; pt.restart(); found=find2(vec, vec.capacity()); d=pt.elapsed(); cout << "second search required: " << d << endl; cout << "second search found value: " << value_found(vec, found)<< endl; return 0; } On my machine (Intel i7, Windows Vista) STL find (call via find1) runs about 10 times faster than the hand-crafted loop (call via find2). I first thought that Visual C++ performs some kind of vectorization (may be I am mistaken here), but as far as I can see assembly does not look the way it uses vectorization. Why is STL loop faster? Hand-crafted loop is identical to the loop from the STL-find body. I was asked to post program's output. Without shuffle: value generation required: 0.078 first search required: 0.008 first search found value: no second search required: 0.098 second search found value: no With shuffle (caching effects): value generation required: 1.454 first search required: 0.009 first search found value: no second search required: 0.044 second search found value: no Many thanks, dusha. P.S. I return the iterator and write out the result (found or not), because I would like to prevent compiler optimization, that it thinks the loop is not required at all. The searched value is obviously not in the vector.

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