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  • Looking for algorithms regarding scaling and moving

    - by user1806687
    I've been bashing my head for the past couple of weeks trying to find algorithms that would help me accomplish, on first look very easy task. So, I got this one object currently made out of 5 cuboids (2 sides, 1 top, 1 bottom, 1 back), this is just for an example, later on there will be whole range of different set ups. I have included three pictures of this object(as said this is just for an example). Now, the thing is when the user scales the whole object this is what should happen: X scale: top and bottom cuboids should get scaled by a scale factor, sides should get moved so they are positioned just like they were before(in this case at both ends of top and bottom cuboids), back should get scaled so it fits like before(if I simply scale it by a scale factor it will leave gaps on each side). Y scale: sides should get scaled by a scale factor, top and bottom cuboid should get moved, and back should also get scaled. Z scale: sides, top and bottom cuboids should get scaled, back should get moved. Here is an image of the example object (a thick walled box, with one face missing, where each wall is made by a cuboid): Front of the object: Hope you can help,

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  • Developing a search algorithm

    - by Richart Bremer
    I want to create a basic search engine, and I want you to give me some ideas how to filter out the best results for my visitors. I have three fields regarding a product the user can search in: Title Category Description I came up with these ideas and I ask you to either competently criticize them or add to them. If the search term occurs in all three fields it should be among the first results. If it is in two of the fields it is below the results of 1. Combine the amount of occurences and output a value in per cent. For instance if in all fields together the term clock appeared 50 times and in all fields together there are 200 words, then the per cent value is 50/200*100 = 25%. Another product entry amounts to say 20% so product one having 25% is listed before product two having 20%.

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  • How do you blend multiple colors in HSV (polar) color-space?

    - by Toxikman
    In RGB color space, you can do a weighted multiple-color blend by just doing: Start with R = G = B = 0. Then we perform a blend at index i using a set of colors C, and a set of normalized weights w like so: R += w[i] * C[i].r G += w[i] * C[i].g B += w[i] * C[i].b But I'd like to interpolate the colors in the HSV color-space instead, so that saturation and brightness are uniform across the interpolation. I know I can blend saturation and brightness in the same way as above, but the HUE component is an angle around a continuous circle, since HSV is essentially a polar coordinate system. Blending only two HSV colors makes sense to me, you just find the shortest arc around the circle and interpolate between the two hues. But when you attempt to blend more than 2 colors, it becomes a bit of a puzzle. You have to handle anomalous cases, like 4 equally-weighted colors with a hue at 0, 90, 180, and 270 degrees. They basically cancel each other out, so any hue will do. Any ideas would be greatly appreciated.

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  • Moving two objects proportionally

    - by SSL
    I'm trying to move two objects away from each other at a proportional distance, but on different scales. I'm not quite sure how to do this. Object A can go from position 0.1 to 1. Object B has no limits. If object B is decreasing, then Object A should be decreasing at rate R. Likewise, if Object B is increasing, then Object A increases at rate R. How can I tie these two Object positions together so that in an update loop, they automatically update their positions? I tried using: ObjA.Pos += 0.001f * ObjB.VelocityY; //0.001f is the rate This works but there's an error each time it runs. ObjA starts off at its max position 1 but then the next time it will stop at 0.97, 0.94, 0.91 etc.. This is due to the 0.001f rate I put in. Is there a way to control the rate, yet not end up with the rounding error?

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  • Algorithm to generate N random numbers between A and B which sum up to X

    - by Shaamaan
    This problem seemed like something which should be solvable with but a few lines of code. Unfortunately, once I actually started to write the thing, I've realized it's not as simple as it sounds. What I need is a set of X random numbers, each of which is between A and B and they all add up to X. The exact variables for the problem I'm facing seem to be even simpler: I need 5 numbers, between -1 and 1 (note: these are decimal numbers), which add up to 1. My initial "few lines of code, should be easy" approach was to randomize 4 numbers between -1 and 1 (which is simple enough), and then make the last one 1-(sum of previous numbers). This quickly proved wrong, as the last number could just as well be larger than 1 or smaller than -1. What would be the best way to approach this problem? PS. Just for reference: I'm using C#, but I don't think it matters. I'm actually having trouble creating a good enough solution for the problem in my head.

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  • Calculate random points (pixel) within a circle (image)

    - by DMills
    I have an image that contains a circles at a specific location, and of a specific diameter. What I need to do is to be able to calculate random points within the circle, and then manipulate said the pixels they correlate to. I have the following code already: private Point CalculatePoint() { var angle = _random.NextDouble() * ( Math.PI * 2 ); var x = _originX + ( _radius * Math.Cos( angle ) ); var y = _originY + ( _radius * Math.Sin( angle ) ); return new Point( ( int )x, ( int )y ); } And that works fine for finding all the points at the circumference of the circle, but I need all points from anywhere in the circle. If this doesn't make sense let me know and I will do my best to clarify.

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  • How Does Search Engine Optimization Algorithm Work?

    According to the basic understanding of Search Engine Optimization, it is the procedure of designing a web site or web page in a way that it becomes compatible with search engines as a search result and is relevant for the visitors or readers as well. The design and content has to be optimized because the parameters that make a web-page or web site friendly for search engine and for viewers may be different. Therefore, an optimized solution has to be obtained for best results.

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  • Showing range on hexagonal grid

    - by user23673
    Here is the situation. I have hexagonal board,and a unit on it,with speed or move value 4.Diffrent terrain has a diffrent cost.When i click on the unit,game should show me a move range. My solution was to check each hex in range of 4,with A* pathfinding,and if path cost was less than 4 then this hex was in range.Finally game nicely show me range of that unit. My question is: Is there other solution to search for range on hex grids or square grid,because even if i am really proud of what i did in my solution,i think,it is a little to exaggerated?:)) What make me ask this question?I noticed that when unit speed is 4 or 6 or even 8,time to computing range for my computer was really good,but when speed was 10 and more i noticed that i needed to wait few second to compute.Well in real games i rather dont see something like this and my A* pathfinding is rather well optimized,so im thinking that my solution is wrong. Thanks for any replies.

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  • How do I have an arrow follow different height parabolas depending on how long the player holds down a key?

    - by Moondustt
    i'm trying to throw an arrow in my game, but i'm having a hard time trying to realize how to make a good parabola. What I need: The more you hold "enter" stronger the arrow goes. The arrow angle will be always the same, 45 degrees. This is what I have already have: private float velocityHeld = 1f; protected override void Update(GameTime gameTime) { private void GetKeyboardEvent() { if (Keyboard.GetState().IsKeyDown(Keys.Enter) && !released) { timeHeld += velocityHeld; holding = true; } else { if (holding) { released = true; holding = false; lastTimeHeld = timeHeld; } } } if (released && timeHeld > 0) { float alpha = MathHelper.ToRadians(45f); double vy = timeHeld * Math.Sin(alpha); double vx = timeHeld * Math.Cos(alpha); ShadowPosition.Y -= (int)vy; ShadowPosition.X += (int)vx; timeHeld -= velocityHeld; } else { released = false; } } My question is, what do I need to do to make the arrow to go bottom as it loses velocity (timeHeld) to make a perfect parabola?

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  • Surprising results with .NET multi-theading algorithm

    - by Myles J
    Hi, I've recently wrote a C# console time tabling algorithm that is based on a combination of a genetic algorithm with a few brute force routines thrown in. The initial results were promising but I figured I could improve the performance by splitting the brute force routines up to run in parallel on multi processor architectures. To do this I used the well documented Producer/Consumer model (as documented in this fantastic article http://www.albahari.com/threading/part2.aspx#_ProducerConsumerQWaitHandle). I changed my code to create one thread per logical processor during the brute force routines. The performance gains on my work station were very pleasing. I am running Windows XP on the following hardware: Intel Core 2 Quad CPU 2.33 GHz 3.49 GB RAM Initial tests indicated average performance gains of approx 40% when using 4 threads. The next step was to deploy the new multi-threading version of the algorithm to our higher spec UAT server. Here is the spec of our UAT server: Windows 2003 Server R2 Enterprise x64 8 cpu (Quad-Core) AMD Opteron 2.70 GHz 255 GB RAM After running the first round of tests we were all extremely surprised to find that the algorithm actually runs slower on the high spec W2003 server than on my local XP work station! In fact the tests seem to indicate that it doesn't matter how many threads are generated (tests were ran with the app spawning between 2 to 32 threads). The algorithm always runs significantly slower on the UAT W2003 server? How could this be? Surely the app should run faster on a 8 cpu (Quad-Core) than my 2 Quad work station? Why are we seeing no performance gains with the multi-threading on the W2003 server whilst the XP workstation tests show gains of up to 40%? Any help or pointers would be appreciated. Regards Myles

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  • ASP.NET 2.0 RijndaelManaged encryption algorithm vs. FIPS

    - by R Rush
    I'm running into an issue with an ASP.NET 2.0 application. Our network folks just upped our security, and now I get the floowing error whenever I try to access the app: "This implementation is not part of the Windows Platform FIPS validated cryptographic algorithms." I've done a little research, and it sounds like ASP.NET uses the RijndaelManaged AES encryption algorithm to encrypt the ViewState of pages... and RijndaelManaged is on the list of algorithms that aren't FIPS compliant. We're certainly not explicitly calling any encryption algorithm... much less anything on the non-compliant list. This ViewState business makes sense to me, I guess. The thing I can't muddle out, though, is what to do about it. I've found a KB article that suggests using a web.config setting to specify a different algorithm... but either that didn't stick, or that algorithm isn't up to snuff, either. So: 1) Is the RijndaelManaged / ViewState thing actually the problem? Or am I barking up the wrong tree? 2) How to I specify what algorithm to use instead of RijndaelManaged? I've got a list of algorithms that are and aren't compliant; I'm just not sure where to plug that information in. Thanks! Richard

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  • Most efficient method to query a Young Tableau

    - by Matthieu M.
    A Young Tableau is a 2D matrix A of dimensions M*N such that: i,j in [0,M)x[0,N): for each p in (i,M), A[i,j] <= A[p,j] for each q in (j,N), A[i,j] <= A[i,q] That is, it's sorted row-wise and column-wise. Since it may contain less than M*N numbers, the bottom-right values might be represented either as missing or using (in algorithm theory) infinity to denote their absence. Now the (elementary) question: how to check if a given number is contained in the Young Tableau ? Well, it's trivial to produce an algorithm in O(M*N) time of course, but what's interesting is that it is very easy to provide an algorithm in O(M+N) time: Bottom-Left search: Let x be the number we look for, initialize i,j as M-1, 0 (bottom left corner) If x == A[i,j], return true If x < A[i,j], then if i is 0, return false else decrement i and go to 2. Else, if j is N-1, return false else increment j This algorithm does not make more than M+N moves. The correctness is left as an exercise. It is possible though to obtain a better asymptotic runtime. Pivot Search: Let x be the number we look for, initialize i,j as floor(M/2), floor(N/2) If x == A[i,j], return true If x < A[i,j], search (recursively) in A[0:i-1, 0:j-1], A[i:M-1, 0:j-1] and A[0:i-1, j:N-1] Else search (recursively) in A[i+1:M-1, 0:j], A[i+1:M-1, j+1:N-1] and A[0:i, j+1:N-1] This algorithm proceed by discarding one of the 4 quadrants at each iteration and running recursively on the 3 left (divide and conquer), the master theorem yields a complexity of O((N+M)**(log 3 / log 4)) which is better asymptotically. However, this is only a big-O estimation... So, here are the questions: Do you know (or can think of) an algorithm with a better asymptotical runtime ? Like introsort prove, sometimes it's worth switching algorithms depending on the input size or input topology... do you think it would be possible here ? For 2., I am notably thinking that for small size inputs, the bottom-left search should be faster because of its O(1) space requirement / lower constant term.

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  • scrabble algorithm....

    - by teddy
    I'm making algorithm like crossword, but I dont know how to design the algorithm. For example: there are words like 'car', 'apple' in the dictionary. the word 'app' is given on the board. there are letters like 'l' 'e' 'c' 'r'....for making words. So the algorithm's task is to make correct words which are stored in dictionary. app - lapp - leapp - lecapp - .... - lappe - eappc - ... - appl - apple (correct answer) What is the best solution for this algorithm?

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  • Efficient way of calculating average difference of array elements from array average value

    - by Saysmaster
    Is there a way to calculate the average distance of array elements from array average value, by only "visiting" each array element once? (I search for an algorithm) Example: Array : [ 1 , 5 , 4 , 9 , 6 ] Average : ( 1 + 5 + 4 + 9 + 6 ) / 5 = 5 Distance Array : [|1-5|, |5-5|, |4-5|, |9-5|, |6-5|] = [4 , 0 , 1 , 4 , 1 ] Average Distance : ( 4 + 0 + 1 + 4 + 1 ) / 5 = 2 The simple algorithm needs 2 passes. 1st pass) Reads and accumulates values, then divides the result by array length to calculate average value of array elements. 2nd pass) Reads values, accumulates each one's distance from the previously calculated average value, and then divides the result by array length to find the average distance of the elements from the average value of the array. The two passes are identical. It is the classic algorithm of calculating the average of a set of values. The first one takes as input the elements of the array, the second one the distances of each element from the array's average value. Calculating the average can be modified to not accumulate the values, but caclulating the average "on the fly" as we sequentialy read the elements from the array. The formula is: Compute Running Average of Array's elements ------------------------------------------- RA[i] = E[i] {for i == 1} RA[i] = RA[i-1] - RA[i-1]/i + A[i]/i { for i > 1 } Where A[x] is the array's element at position x, RA[x] is the average of the array's elements between position 1 and x (running average). My question is: Is there a similar algorithm, to calculate "on the fly" (as we read the array's elements), the average distance of the elements from the array's mean value? The problem is that, as we read the array's elements, the final average value of the array is not known. Only the running average is known. So calculating differences from the running average will not yield the correct result. I suppose, if such algorithm exists, it probably should have the "ability" to compensate, in a way, on each new element read for the error calculated as far.

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  • Are mathematical Algorithms protected by copyright?

    - by analogy
    I wish to implement an algorithm which i read in a journal paper in my software (commercial). I want to know if this is allowed or not. The algorithm in question is described in http://arxiv.org/abs/0709.2938 It is a very simple algorithm and a number of implementations exist in python (http://igraph.sourceforge.net/) and java. One of them is in gpl another which i got from a different researcher and had no license attached. There are significant differences in two implementations, e.g. second one uses threads and multiple cores. It is possible to rewrite/ (not translate) the algorithm. So can I use it in my software or on a server for commercial purpose. Thanks UPDATE: I am completely aware of copyright on the text of paper, it was published in phys rev E. I am concerned with use of the algorithm, in commercial software. Also the publication means that unless the patent has been already filed. The method has been disclosed publicly hence barring patent in future. Also the GPL implementation is not by authors themselves but comes from a third party. Finally i am not using the GPL implementation but creating my own using C++.

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  • Packing differently sized chunks of data into multiple bins

    - by knizz
    EDIT: It seems like this problem is called "Cutting stock problem" I need an algorithm that gives me the (space-)optimal arrangement of chunks in bins. One way would be put the bigger chunks in first. But see how that algorithm fails in this example: Chunks Bins ----------------------------- AAA BBB CC DD ( ) ( ) Algorithm Result ----------------------------- biggest first (AAABBB ) (CC ) optimal (AAACCDD) (BBB) "Biggest first" can't fit in DD. Maybe it helps to build a table like this: Size 1: --- Size 2: CC, DD Size 3: AAA, BBB Size 4: CCDD Size 5: AAACC, AAADD, BBBCC, BBBDD Size 6: AAABBB Size 7: AAACCDD, BBBCCDD Size 8: AAABBBCC, AAABBBDD Size 10: AAABBBCCDD

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  • Are mathamatical Algorithms protected by copyright

    - by analogy
    I wish to implement an algorithm which i read in a journal paper in my software (commercial). I want to know if this is allowed or not. The algorithm in question is described in http://arxiv.org/abs/0709.2938 It is a very simple algorithm and a number of implementations exist in python (http://igraph.sourceforge.net/) and java. One of them is in gpl another which i got from a different researcher and had no license attached. There are significant differences in two implementations, e.g. second one uses threads and multiple cores. It is possible to rewrite/ (not translate) the algorithm. So can I use it in my software or on a server for commercial purpose. Thanks

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  • Plotting an Arc in Discrete Steps

    - by phobos51594
    Good afternoon, Background My question relates to the plotting of an arbitrary arc in space using discrete steps. It is unique, however, in that I am not drawing to a canvas in the typical sense. The firmware I am designing is for a gcode interpreter for a CNC mill that will translate commands into stepper motor movements. Now, I have already found a similar question on this very site, but the methodology suggested (Bresenham's Algorithm) appears to be incompatable for moving an object in space, as it only relies on the calculation of one octant of a circle which is then mirrored about the remaining axes of symmetry. Furthermore, the prescribed method of calculation an arc between two arbitrary angles relies on trigonometry (I am implementing on a microcontroller and would like to avoid costly trig functions, if possible) and simply not taking the steps that are out of the range. Finally, the algorithm only is designed to work in one rotational direction (e.g. counterclockwise). Question So, on to the actual question: Does anyone know of a general-purpose algorithm that can be used to "draw" an arbitrary arc in discrete steps while still giving respect to angular direction (CW / CCW)? The final implementation will be done in C, but the language for the purpose of the question is irrelevant. Thank you in advance. References S.O post on drawing a simple circle using Bresenham's Algorithm: "Drawing" an arc in discrete x-y steps Wiki page describing Bresenham's Algorithm for a circle http://en.wikipedia.org/wiki/Midpoint_circle_algorithm Gcode instructions to be implemented (see. G2 and G3) http://linuxcnc.org/docs/html/gcode.html

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  • Books on string algorithms

    - by Max
    There have been numerous posts on string algorithms: http://stackoverflow.com/questions/246961/algorithm-to-find-similar-text, http://stackoverflow.com/questions/451884/similar-string-algorithm, http://stackoverflow.com/questions/613133/efficient-string-matching-algorithm However, no general literature was mentioned. Could anyone recommend a book(s) that would thoroughly explore various string algorithms? The topic which is of special interest is approximate string matching [things like google-offered corrected search string variants :) ]. Thanks a lot for advice.

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  • List modification in Python

    - by user2945143
    We are given an algorithm to modify a list of numbers from 1 to 28. There are 5 steps in the algorithm. We have written functions for each step (all correct). We need to write a function that combines all 5 steps. The algorithm modifies the list to get a value. Each time you get a new value, you use the list created by the algorithm from the previous step. This is what we have gotten so far for the code: get_card_at_top_index(insert_top_to_bottom(triple_cut((move_joker_2( move_joker_1(deck)))))) When we run the code to generate the get_card_at_top_index, the first answer is correct. However, the rest are not. Instead of using from the new list, python uses the value that it generated from the last step. What did we do wrong? UPDATE: The other 5 codes passed the tests, they are correct. Code 1 (List) = list1 Code 2 (list1) = list2 Code 3 (list2) = list3 Code 4 (list3) = list4 Code 5 (list4) = list5 we generate a number from 5. We need to run the algorithm again to generate 25 more numbers. We will use list 5 start from step 1

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  • How to find pythagorean triplets in an array faster than O(N^2)?

    - by SS
    Can someone suggest an algorithm that finds all Pythagorean triplets among numbers in a given array? If it's possible, please, suggest an algorithm faster than O(n2). Pythagorean triplet is a set {a,b,c} such that a2 = b2 + c2. Example: for array [9, 2, 3, 4, 8, 5, 6, 10] the output of the algorithm should be {3, 4, 5} and {6, 8, 10}.

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