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  • Linear Search in Python? [closed]

    - by POTUS
    def find_interval(mesh,x): '''This function finds the interval containing x according to the following rules, mesh is an ordered list with n numbers return 0 if x < mesh[0] return n if mesh[n-1] < x return k if mesh[k-1] <= x < mesh[k] return n-1 if mesh[n-2] <= x <= mesh[n-1] This function does a Linear search. 08/29/2012 ''' for n in range(len(mesh)): for k in range(len(mesh)): if x == mesh[n]: print "Found x at index:" return n elif x<mesh[n]: return 0 elif mesh[n-1]<x: return n elif mesh[n-2]<=x<=mesh[n-1]: return n-1 elif mesh[k-1]<=x<mesh[k]: return k mesh = [0, 0.1, 0.25, 0.5, 0.6, 0.75, 0.9, 1] print mesh print find_interval(mesh, -1) print find_interval(mesh, 0) print find_interval(mesh, 0.1) print find_interval(mesh, 0.8) print find_interval(mesh, 0.9) print find_interval(mesh, 1) print find_interval(mesh, 1.01) Output: [0, 0.100000000000000, 0.250000000000000, 0.500000000000000, 0.600000000000000, 0.750000000000000, 0.900000000000000, 1] 0 Found x at index: 0 2 6 -1 -1 0 I don't think the output is correct. Can anyone help me fix it? Thanks.

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  • Constructive criticsm on my linear sampling Gaussian blur

    - by Aequitas
    I've been attempting to implement a gaussian blur utilising linear sampling, I've come across a few articles presented on the web and a question posed here which dealt with the topic. I've now attempted to implement my own Gaussian function and pixel shader drawing reference from these articles. This is how I'm currently calculating my weights and offsets: int support = int(sigma * 3.0) weights.push_back(exp(-(0*0)/(2*sigma*sigma))/(sqrt(2*pi)*sigma)); total += weights.back(); offsets.push_back(0); for (int i = 1; i <= support; i++) { float w1 = exp(-(i*i)/(2*sigma*sigma))/(sqrt(2*pi)*sigma); float w2 = exp(-((i+1)*(i+1))/(2*sigma*sigma))/(sqrt(2*pi)*sigma); weights.push_back(w1 + w2); total += 2.0f * weights[i]; offsets.push_back(w1 / weights[i]); } for (int i = 0; i < support; i++) { weights[i] /= total; } Here is an example of my vertical pixel shader: vec3 acc = texture2D(tex_object, v_tex_coord.st).rgb*weights[0]; vec2 pixel_size = vec2(1.0 / tex_size.x, 1.0 / tex_size.y); for (int i = 1; i < NUM_SAMPLES; i++) { acc += texture2D(tex_object, (v_tex_coord.st+(vec2(0.0, offsets[i])*pixel_size))).rgb*weights[i]; acc += texture2D(tex_object, (v_tex_coord.st-(vec2(0.0, offsets[i])*pixel_size))).rgb*weights[i]; } gl_FragColor = vec4(acc, 1.0); Am I taking the correct route with this? Any criticism or potential tips to improving my method would be much appreciated.

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  • Bounding volume hierarchy - linked nodes (linear model)

    - by teodron
    The scenario A chain of points: (Pi)i=0,N where Pi is linked to its direct neighbours (Pi-1 and Pi+1). The goal: perform efficient collision detection between any two, non-adjacent links: (PiPi+1) vs. (PjPj+1). The question: it's highly recommended in all works treating this subject of collision detection to use a broad phase and to implement it via a bounding volume hierarchy. For a chain made out of Pi nodes, it can look like this: I imagine the big blue sphere to contain all links, the green half of them, the reds a quarter and so on (the picture is not accurate, but it's there to help understand the question). What I do not understand is: How can such a hierarchy speed up computations between segments collision pairs if one has to update it for a deformable linear object such as a chain/wire/etc. each frame? More clearly, what is the actual principle of collision detection broad phases in this particular case/ how can it work when the actual computation of bounding spheres is in itself a time consuming task and has to be done (since the geometry changes) in each frame update? I think I am missing a key point - if we look at the picture where the chain is in a spiral pose, we see that most spheres are already contained within half of others or do intersect them.. it's odd if this is the way it should work.

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  • Algorithm for querying linearly through a non-linear list of questions

    - by JoshLeaves
    For a multiplayers trivia game, I need to supply my users with a new quizz in a desired subject (Science, Maths, Litt. and such) at the start of every game. I've generated about 5K quizzes for each subject and filled my database with them. So my 'Quizzes' database looks like this: |ID |Subject |Question +-----+------------+---------------------------------- | 23 |Science | What's water? | 42 |Maths | What's 2+2? | 99 |Litt. | Who wrote "Pride and Prejudice"? | 123 |Litt. | Who wrote "On The Road"? | 146 |Maths | What's 2*2? | 599 |Science | You know what's cool? |1042 |Maths | What's the Fibonacci Sequence? |1056 |Maths | What's 42? And so on... (Much more detailed/complex but I'll keep the exemple simple) As you can see, due to technical constraints (MongoDB), my IDs are not linear but I can use them as an increasing suite. So far, my algorithm to ensure two users get a new quizz when they play together is the following: // Take the last played quizzes by P1 and P2 var q_one = player_one.getLastPlayedQuizz('Maths'); var q_two = player_two.getLastPlayedQuizz('Maths'); // If both of them never played in the subject, return first quizz in the list if ((q_one == NULL) && (q_two == NULL)) return QuizzDB.findOne({subject: 'Maths'}); // If one of them never played, play the next quizz for the other player // This quizz is found by asking for the first quizz in the desired subject where // the ID is greater than the last played quizz's ID (if the last played quizz ID // is 42, this will return 146 following the above example database) if (q_one == NULL) return QuizzDB.findOne({subject: 'Maths', ID > q_two}); if (q_two == NULL) return QuizzDB.findOne({subject: 'Maths', ID > q_one}); // And if both of them have a lastPlayedQuizz, we return the next quizz for the // player whose lastPlayedQuizz got the higher ID if (q_one > q_two) return QuizzDB.findOne({subject: 'Maths', ID > q_one}); else return QuizzDB.findOne({subject: 'Maths', ID > q_two}); Now here comes the real problem: Once I get to the end of my database (let's say, P1's last played quizz in 'Maths' is 1056, P2's is 146 and P3 is 1042), following my algorithm, P1's ID is the highest so I ask for the next question in 'Maths' where ID is superior to 1056. There is nothing, so I roll back to the beginning of my quizz list (with a random skipper to avoid having the first question always show up). P1 and P2's last played will then be 42 and they will start fresh from the beginning of the list. However, if P1 (42) plays against P3 (1042), the resulting ID will be 1056...which P1 already played two games ago. Basically, players who just "rolled back" to the beginning of the list will be brought back to the end of the list by players who still haven't rolled back. The rollback WILL happen in the end, but it'll take time and there'll be a "bottleneck" at the beginning and at the end. Thus my question: What would be the best algorith to avoid this bottleneck and ensure players don't get stuck endlessly on the same quizzes? Also bear in mind that I've got some technical constraints: I can't get a random question in a subject (ie: no "QuizzDB.findOne({subject: 'Maths'}).skip(random());"). It's cool to skip on one to twenty records, but the MongoDB documentation warns against skipping too many documents. I would like to avoid building an array of every quizz played by each player and find the next non-played in the database with a $nin. Thanks for your help

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  • How can I split Excel data from one row into multiple rows

    - by Lenny
    Good afternoon, Is there a way to split data from one row and store to separate rows? I have a large file that contains scheduling information and I'm trying to develop a list that comprises each combination of course, day, term and period per line. For example I have a file similiar to this: Crs:Sn Title Tchr TchrName Room Days Terms Periods 7014:01 English I 678 JUNG 300 M,T,W,R,F 3,4 2,3 1034:02 English II 123 MOORE 352 M,T,W,R,F 3 4 7144:02 Algebra 238 VYSOTSKY 352 M,T,W,R,F 3,4 3,4 0180:06 Pub Speaking 23 ROSEN 228 M,T,W,R,F 3,4 5 7200:03 PE I 244 HARILAOU GYM 4 M,T,W,R,F 1,2,3 3 2101:01 Physics/Lab 441 JONES 348 M,T,W,R,F 1,2,3,4 2,3 Should extract to this in an excel file: Crs:Sn Title Tchr# Tchr Room Days Terms Period 7014:01 English I 678 JUNG 300 M 3 2 7014:01 English I 678 JUNG 300 T 3 2 7014:01 English I 678 JUNG 300 W 3 2 7014:01 English I 678 JUNG 300 R 3 2 7014:01 English I 678 JUNG 300 F 3 2 7014:01 English I 678 JUNG 300 M 4 2 7014:01 English I 678 JUNG 300 T 4 2 7014:01 English I 678 JUNG 300 W 4 2 7014:01 English I 678 JUNG 300 R 4 2 7014:01 English I 678 JUNG 300 F 4 2 7014:01 English I 678 JUNG 300 M 3 3 7014:01 English I 678 JUNG 300 T 3 3 7014:01 English I 678 JUNG 300 W 3 3 7014:01 English I 678 JUNG 300 R 3 3 7014:01 English I 678 JUNG 300 F 3 3 7014:01 English I 678 JUNG 300 M 4 3 7014:01 English I 678 JUNG 300 T 4 3 7014:01 English I 678 JUNG 300 W 4 3 7014:01 English I 678 JUNG 300 R 4 3 7014:01 English I 678 JUNG 300 F 4 3 1034:02 English II 123 MOORE 352 M 3 4 1034:02 English II 123 MOORE 352 T 3 4 1034:02 English II 123 MOORE 352 W 3 4 1034:02 English II 123 MOORE 352 R 3 4 1034:02 English II 123 MOORE 352 F 3 4 7144:02 Algebra 238 VYSOTSKY 352 M 3 3 7144:02 Algebra 238 VYSOTSKY 352 T 3 3 7144:02 Algebra 238 VYSOTSKY 352 W 3 3 7144:02 Algebra 238 VYSOTSKY 352 R 3 3 7144:02 Algebra 238 VYSOTSKY 352 F 3 3 7144:02 Algebra 238 VYSOTSKY 352 M 4 3 7144:02 Algebra 238 VYSOTSKY 352 T 4 3 7144:02 Algebra 238 VYSOTSKY 352 W 4 3 7144:02 Algebra 238 VYSOTSKY 352 R 4 3 7144:02 Algebra 238 VYSOTSKY 352 F 4 3 7144:02 Algebra 238 VYSOTSKY 352 M 3 4 7144:02 Algebra 238 VYSOTSKY 352 T 3 4 7144:02 Algebra 238 VYSOTSKY 352 W 3 4 7144:02 Algebra 238 VYSOTSKY 352 R 3 4 7144:02 Algebra 238 VYSOTSKY 352 F 3 4 7144:02 Algebra 238 VYSOTSKY 352 M 4 4 7144:02 Algebra 238 VYSOTSKY 352 T 4 4 7144:02 Algebra 238 VYSOTSKY 352 W 4 4 7144:02 Algebra 238 VYSOTSKY 352 R 4 4 7144:02 Algebra 238 VYSOTSKY 352 F 4 4 0180:06 Pub Speaking 23 ROSEN 228 M 3 5 0180:06 Pub Speaking 23 ROSEN 228 T 3 5 0180:06 Pub Speaking 23 ROSEN 228 W 3 5 0180:06 Pub Speaking 23 ROSEN 228 R 3 5 0180:06 Pub Speaking 23 ROSEN 228 F 3 5 0180:06 Pub Speaking 23 ROSEN 228 M 4 5 0180:06 Pub Speaking 23 ROSEN 228 T 4 5 0180:06 Pub Speaking 23 ROSEN 228 W 4 5 0180:06 Pub Speaking 23 ROSEN 228 R 4 5 0180:06 Pub Speaking 23 ROSEN 228 F 4 5 7200:03 PE I 244 HARILAOU GYM 4 M 1 3 7200:03 PE I 244 HARILAOU GYM 4 M 2 3 7200:03 PE I 244 HARILAOU GYM 4 M 3 3 7200:03 PE I 244 HARILAOU GYM 4 T 1 3 7200:03 PE I 244 HARILAOU GYM 4 T 2 3 7200:03 PE I 244 HARILAOU GYM 4 T 3 3 7200:03 PE I 244 HARILAOU GYM 4 W 1 3 7200:03 PE I 244 HARILAOU GYM 4 W 2 3 7200:03 PE I 244 HARILAOU GYM 4 W 3 3 7200:03 PE I 244 HARILAOU GYM 4 R 1 3 7200:03 PE I 244 HARILAOU GYM 4 R 2 3 7200:03 PE I 244 HARILAOU GYM 4 R 3 3 7200:03 PE I 244 HARILAOU GYM 4 F 1 3 7200:03 PE I 244 HARILAOU GYM 4 F 2 3 7200:03 PE I 244 HARILAOU GYM 4 F 3 3 2101:01 Physics/Lab 441 JONES 348 M 1 2 2101:01 Physics/Lab 441 JONES 348 M 2 2 2101:01 Physics/Lab 441 JONES 348 M 3 2 2101:01 Physics/Lab 441 JONES 348 M 4 2 2101:01 Physics/Lab 441 JONES 348 T 1 2 2101:01 Physics/Lab 441 JONES 348 T 2 2 2101:01 Physics/Lab 441 JONES 348 T 3 2 2101:01 Physics/Lab 441 JONES 348 T 4 2 2101:01 Physics/Lab 441 JONES 348 W 1 2 2101:01 Physics/Lab 441 JONES 348 W 2 2 2101:01 Physics/Lab 441 JONES 348 W 3 2 2101:01 Physics/Lab 441 JONES 348 W 4 2 2101:01 Physics/Lab 441 JONES 348 R 1 2 2101:01 Physics/Lab 441 JONES 348 R 2 2 2101:01 Physics/Lab 441 JONES 348 R 3 2 2101:01 Physics/Lab 441 JONES 348 R 4 2 2101:01 Physics/Lab 441 JONES 348 F 1 2 2101:01 Physics/Lab 441 JONES 348 F 2 2 2101:01 Physics/Lab 441 JONES 348 F 3 2 2101:01 Physics/Lab 441 JONES 348 F 4 2 2101:01 Physics/Lab 441 JONES 348 M 1 3 2101:01 Physics/Lab 441 JONES 348 M 2 3 2101:01 Physics/Lab 441 JONES 348 M 3 3 2101:01 Physics/Lab 441 JONES 348 M 4 3 2101:01 Physics/Lab 441 JONES 348 T 1 3 2101:01 Physics/Lab 441 JONES 348 T 2 3 2101:01 Physics/Lab 441 JONES 348 T 3 3 2101:01 Physics/Lab 441 JONES 348 T 4 3 2101:01 Physics/Lab 441 JONES 348 W 1 3 2101:01 Physics/Lab 441 JONES 348 W 2 3 2101:01 Physics/Lab 441 JONES 348 W 3 3 2101:01 Physics/Lab 441 JONES 348 W 4 3 2101:01 Physics/Lab 441 JONES 348 R 1 3 2101:01 Physics/Lab 441 JONES 348 R 2 3 2101:01 Physics/Lab 441 JONES 348 R 3 3 2101:01 Physics/Lab 441 JONES 348 R 4 3 2101:01 Physics/Lab 441 JONES 348 F 1 3 2101:01 Physics/Lab 441 JONES 348 F 2 3 2101:01 Physics/Lab 441 JONES 348 F 3 3 2101:01 Physics/Lab 441 JONES 348 F 4 3 I'm trying to avoid going line by line separating the data. I'm not well versed on the VBA functionality of Excel, but would like to get started using it. Any help would be greatly appreciated.

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  • How does java.util.Collections.contains() perform faster than a linear search?

    - by The111
    I've been fooling around with a bunch of different ways of searching collections, collections of collections, etc. Doing lots of stupid little tests to verify my understanding. Here is one which boggles me (source code further below). In short, I am generating N random integers and adding them to a list. The list is NOT sorted. I then use Collections.contains() to look for a value in the list. I intentionally look for a value that I know won't be there, because I want to ensure that the entire list space is probed. I time this search. I then do another linear search manually, iterating through each element of the list and checking if it matches my target. I also time this search. On average, the second search takes 33% longer than the first one. By my logic, the first search must also be linear, because the list is unsorted. The only possibility I could think of (which I immediately discard) is that Java is making a sorted copy of my list just for the search, but (1) I did not authorize that usage of memory space and (2) I would think that would result in MUCH more significant time savings with such a large N. So if both searches are linear, they should both take the same amount of time. Somehow the Collections class has optimized this search, but I can't figure out how. So... what am I missing? import java.util.*; public class ListSearch { public static void main(String[] args) { int N = 10000000; // number of ints to add to the list int high = 100; // upper limit for random int generation List<Integer> ints; int target = -1; // target will not be found, forces search of entire list space long start; long end; ints = new ArrayList<Integer>(); start = System.currentTimeMillis(); System.out.print("Generating new list... "); for (int i = 0; i < N; i++) { ints.add(((int) (Math.random() * high)) + 1); } end = System.currentTimeMillis(); System.out.println("took " + (end-start) + "ms."); start = System.currentTimeMillis(); System.out.print("Searching list for target (method 1)... "); if (ints.contains(target)) { // nothing } end = System.currentTimeMillis(); System.out.println(" Took " + (end-start) + "ms."); System.out.println(); ints = new ArrayList<Integer>(); start = System.currentTimeMillis(); System.out.print("Generating new list... "); for (int i = 0; i < N; i++) { ints.add(((int) (Math.random() * high)) + 1); } end = System.currentTimeMillis(); System.out.println("took " + (end-start) + "ms."); start = System.currentTimeMillis(); System.out.print("Searching list for target (method 2)... "); for (Integer i : ints) { // nothing } end = System.currentTimeMillis(); System.out.println(" Took " + (end-start) + "ms."); } }

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  • 2D Car Simulation with Throttle Linear Physics

    - by James
    I'm trying to make a simulation game for an automatic cruise control system. The system simulates a car on varying inclinations and throttle speeds. I've coded up to the car physics but these do note make sense. The dynamics of the simulation are specified as follows: a = V' - V T = (k1)V + ?(k2) + ma V' = (1 - (k1 / m) V) + T - ( k2 / m) * ? Where T = throttle position k1 = viscous friction V = speed V' = next speed ? = angle of incline k2 = m g sin ? a = acceleration m = mass Notice that the angle of incline in the equation is not chopped up by sin or cos. Even the equation for acceleration isn't right. Can anyone correct them or am I misinterpreting the physics?

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  • Linear search vs Octree (Frustum cull)

    - by Dave
    I am wondering whether I should look into implementing an octree of some kind. I have a very simple game which consists of a 3d plane for the floor. There are multiple objects scattered around on the ground, each one has an aabb in world space. Currently I just do a loop through the list of all these objects and check if its bounding box intersects with the frustum, it works great but I am wondering if if it would be a good investment in an octree. I only have max 512 of these objects on the map and they all contain bounding boxes. I am not sure if an octree would make it faster since I have so little objects in the scene.

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  • Integer Linear Programming Java: Multiple Open Source and Commercial tools are available. Which one

    - by Sandeep Jindal
    Hi, I need to use Integer Linear Programming API/Tool for my application. Though my application is in Java but I don’t mind calling an EXE (Tool) from Java providing input using file (MPS, etc). My search analysis is as follows: There are multiple Open Source and Commercial tools available to solve ILP Following I found and think are useful for my needs. 1. Gnu LP Kit(GLPK): I think this is the oldest and probably most stable and efficient 2. IP_Solve: Has good reviews about it. 3. JavaILP: Found this, but not much reviews about it 4. Apache Common-Math: Supports LP but not ILP, so ruled out. 5. Coin-OR Can you please suggest which one shall be the best in terms of stability, efficiency, acceptance, etc Regards Sandeep Jindal

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  • R: ggplot2, how to get the parameters from a plotted linear model smoother?

    - by John
    I have a data.frame with 3 time series in it, shown below. When I plot them with a smoother time series, I want to be able to get the parameters of the linear model that I plot, but I can't see how to do that? > data day od series_id 1 1 0.10 A1 2 3 1.00 A1 3 5 0.50 A1 4 7 0.70 A1 5 1 1.70 B1 6 3 1.60 B1 7 5 1.75 B1 8 7 1.70 B1 9 1 2.10 C1 10 3 2.30 C1 11 5 2.50 C1 12 7 2.70 C1 data = data.frame (day = c(1,3,5,7,1,3,5,7,1,3,5,7), od = c(0.1,1.0,0.5,0.7 ,1.7,1.6,1.75,1.7 ,2.1,2.3,2.5,2.7), series_id = c("A1", "A1", "A1","A1", "B1", "B1","B1", "B1", "C1","C1", "C1", "C1")) r <- ggplot(data = data, aes(x = day, y = od)) r + stat_smooth(aes(group = series_id, color = series_id),method="lm")

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  • Rewrite probabilities as boolean algebra

    - by Magsol
    I'm given three binary random variables: X, Y, and Z. I'm also given the following: P(Z | X) P(Z | Y) P(X) P(Y) I'm then supposed to determine whether or not it is possible to find P(Z | Y, X). I've tried rewriting the solution in the form of Bayes' Theorem and have gotten nowhere. Given that these are boolean random variables, is it possible to rewrite the system in terms of boolean algebra? I understand that the conditionals can be mapped to boolean implications (x -> y, or !x + y), but I'm unsure how this would translate in terms of the overall problem I'm trying to solve. (yes, this is a homework problem, but here I'm much more interested in how to formally solve this problem than what the solution is...I also figured this question would be entirely too simple for MathOverflow)

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  • Nested Linear layout only shows first view after being set from gone to visible in Android

    - by Adam
    Hi guys, I am developing an Android app but I'm still pretty new. I want to have a button, and when you push that button, a few TextViews and Buttons will appear. So I have a main linear layout, and then another linear layout nested inside containing the things I want hidden. I have the nested linear layout set to android:visibility="gone". The problem I am having is that it only shows the first item inside the hidden linear layout instead of all of them. The way I try to make it appear is vgAddView = (ViewGroup)findViewById(R.id.add_details); btnAche.setOnClickListener(new OnClickListener(){ public void onClick(View v){ vgAddView.setVisibility(0); } }); My XML file is this <?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="fill_parent" > <Button android:text="@string/but_stomach_ache" android:id="@+id/but_stomach_ache" android:layout_width="fill_parent" android:layout_height="wrap_content"> </Button> <Button android:text="@string/but_food" android:id="@+id/but_food" android:layout_width="fill_parent" android:layout_height="wrap_content"> </Button> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="fill_parent" android:id="@+id/add_details" android:visibility="gone"> <TextView android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="fill_parent" android:text="@string/when_happen"> </TextView> <Button android:text="@string/happen_now" android:id="@+id/happen_now" android:layout_width="fill_parent" android:layout_height="wrap_content"> </Button> </LinearLayout> </LinearLayout>

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  • Excel 2007: plot data points not on an axis/ force linear x-incrementation without altering integrity of non-linear data

    - by Ennapode
    In Excel, how does one go about plotting points that don't have an x component that is an x-axis label? For example, in my graph, the x-components are derived from the cosine function and aren't linear, but Excel is displaying them as if .0016 to .0062 to .0135 is an equal incrementation. How would I change this so that the x-axis has an even incrementation without altering the integrity of the points themselves? In other words, how do I plot a point with an x component independent from the x-axis label?

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  • How to implement a simple bullet trajectory

    - by AirieFenix
    I searched and searched and although it's a fair simple question, I don't find the proper answer but general ideas (which I already have). I have a top-down game and I want to implement a gun which shoots bullets that follow a simple path (no physics nor change of trajectory, just go from A to B thing). a: vector of the position of the gun/player. b: vector of the mouse position (cross-hair). w: the vector of the bullet's trajectory. So, w=b-a. And the position of the bullet = [x=x0+speed*time*normalized w.x , y=y0+speed*time * normalized w.y]. I have the constructor: public Shot(int shipX, int shipY, int mouseX, int mouseY) { //I get mouse with Gdx.input.getX()/getY() ... this.shotTime = TimeUtils.millis(); this.posX = shipX; this.posY = shipY; //I used aVector = aVector.nor() here before but for some reason didn't work float tmp = (float) (Math.pow(mouseX-shipX, 2) + Math.pow(mouseY-shipY, 2)); tmp = (float) Math.sqrt(Math.abs(tmp)); this.vecX = (mouseX-shipX)/tmp; this.vecY = (mouseY-shipY)/tmp; } And here I update the position and draw the shot: public void drawShot(SpriteBatch batch) { this.lifeTime = TimeUtils.millis() - this.shotTime; //position = positionBefore + v*t this.posX = this.posX + this.vecX*this.lifeTime*speed*Gdx.graphics.getDeltaTime(); this.posY = this.posY + this.vecY*this.lifeTime*speed*Gdx.graphics.getDeltaTime(); ... } Now, the behavior of the bullet seems very awkward, not going exactly where my mouse is (it's like the mouse is 30px off) and with a random speed. I know I probably need to open the old algebra book from college but I'd like somebody says if I'm in the right direction (or points me to it); if it's a calculation problem, a code problem or both. Also, is it possible that Gdx.input.getX() gives me non-precise position? Because when I draw the cross-hair it also draws off the cursor position. Sorry for the long post and sorry if it's a very basic question. Thanks!

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  • Best way to implement a simple bullet trajectory

    - by AirieFenix
    I searched and searched and although it's a fair simple question, I don't find the proper answer but general ideas (which I already have). I have a top-down game and I want to implement a gun which shoots bullets that follow a simple path (no physics nor change of trajectory, just go from A to B thing). a: vector of the position of the gun/player. b: vector of the mouse position (cross-hair). w: the vector of the bullet's trajectory. So, w=b-a. And the position of the bullet = [x=x0+speed*time*normalized w.x , y=y0+speed*time * normalized w.y]. I have the constructor: public Shot(int shipX, int shipY, int mouseX, int mouseY) { //I get mouse with Gdx.input.getX()/getY() ... this.shotTime = TimeUtils.millis(); this.posX = shipX; this.posY = shipY; //I used aVector = aVector.nor() here before but for some reason didn't work float tmp = (float) (Math.pow(mouseX-shipX, 2) + Math.pow(mouseY-shipY, 2)); tmp = (float) Math.sqrt(Math.abs(tmp)); this.vecX = (mouseX-shipX)/tmp; this.vecY = (mouseY-shipY)/tmp; } And here I update the position and draw the shot: public void drawShot(SpriteBatch batch) { this.lifeTime = TimeUtils.millis() - this.shotTime; //position = positionBefore + v*t this.posX = this.posX + this.vecX*this.lifeTime*speed*Gdx.graphics.getDeltaTime(); this.posY = this.posY + this.vecY*this.lifeTime*speed*Gdx.graphics.getDeltaTime(); ... } Now, the behavior of the bullet seems very awkward, not going exactly where my mouse is (it's like the mouse is 30px off) and with a random speed. I know I probably need to open the old algebra book from college but I'd like somebody says if I'm in the right direction (or points me to it); if it's a calculation problem, a code problem or both. Also, is it possible that Gdx.input.getX() gives me non-precise position? Because when I draw the cross-hair it also draws off the cursor position. Sorry for the long post and sorry if it's a very basic question. Thanks!

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  • -moz-linear-gradient

    - by bah
    Hi, Could someone explain to me what this portion of code means? repeat scroll 0 0 #F6F6F6; I have googled a lot and only found syntax to this part -moz-linear-gradient(center top , #FFFFFF, #EFEFEF) My code: background: -moz-linear-gradient(center top , #FFFFFF, #EFEFEF) repeat scroll 0 0 #F6F6F6; Thanks!

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  • Linear Performance Scalability with HP San Solutions

    - by Berzemus
    Hi all, I need a San Solution with linear scalability in size as well as in performance. From what I know, with a Modular Smart Array solution such as the P2000/MSA-class solutions from HP, even with a dual controller initial node, I can only increase the size of it, as added nodes come controller-less, so overall performance tends to decrease. On the other hand, the P4000 (lefthand) family of solutions has each of it's nodes have it's own controller, and so when a node is added, storage capacity as well as performance increase. Am I right in all that I say, and is the P4000 the only solution, or have I forgotten something ?

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  • How can calculus and linear algebra be useful to a system programmer?

    - by Victor
    I found a website saying that calculus and linear algebra are necessary for System Programming. System Programming, as far as I know, is about osdev, drivers, utilities and so on. I just can't figure out how calculus and linear algebra can be helpful on that. I know that calculus has several applications in science, but in this particular field of programming I just can't imagine how calculus can be so important. The information was on this site: http://www.wikihow.com/Become-a-Programmer Edit: Some answers here are explaining about algorithm complexity and optimization. When I made this question I was trying to be more specific about the area of System's Programming. Algorithm complexity and optimization can be applied to any area of programming not just System's Programming. That may be why I wasn't able to came up with such thinking at the time of the question.

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  • Linear-time algorithms for sorting vertices in polygon contours

    - by Cheery
    I figured out an algorithm that lets me turn my holed polygons into trapezoids in linear time if I have vertex indices sorted from lowest coordinate to highest. I get simple polygons as contours. They have certain order that might be exploited most of the time. So giving these conditions, is there a near-linear-time algorithm on sorting?

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  • Linear gradients library

    - by Lieven Cardoen
    Is there a place online where I can find like 16 linear gradients that match good with each other? I need them for a chart of mine and the ones generated (by Flex) aren't good enough. So, I'm kind off searching for a library of gradients (linear in my case).

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  • Mathematics for Computer Science Students

    - by Ender
    To cut a long story short, I am a CS student that has received no formal Post-16 Maths education for years. Right now even my Algebra is extremely rusty and I have a couple of months to shape up my skills. I've got a couple of video lectures in my bookmarks, consisting of: Pre-Calculus Algebra Calculus Probability Introduction to Statistics Differential Equations Linear Algebra My aim as of today is to be able to read the CLRS book Introduction to Algorithms and be able to follow the Mathematical notation in that, as well as being able to confidently read and back-up any arguments written in Mathematical notation. Aside from these video lectures, can anyone recommend any good books to help teach someone wishing to go from a low-foundation level to a more advanced level of Mathematics? Just as a note, I've taken a first-year module in Analytical Modelling, so I understand some of the basic concepts of Discrete Mathematics. EDIT: Just a note to those that are looking to learn Linear Algebra using the Video Lectures I have posted up. Peteris Krumins' Blog contains a run-through of these lecture notes as well as his own commentary and lecture notes, an invaluable resource for those looking to follow the lectures too.

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