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Search found 562 results on 23 pages for 'discrete mathematics'.

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• Equation / formula to determine an objects position on an ellipitcal path

  - by David Murphy

  I'm making a space game, as such I need objects to follow an elliptical path (orbit). I've worked out how to calculate all the important aspects of my orbits, the only remaining thing is how to have an object follow it. My Orbit class contains the major, minor (and by extension semi-major,semi-minor) lengths. The focii radius, area and circumference even. What is the equation to determine an objects x/y position (only need 2D) on an ellipse with a certain speed after a period of time. Basically, every frame I want to update the position based on the amount of elapsed time. I would like to have the speed along the path speed up and slow down according to the distance from the object it's orbiting, but not sure how to factor this in to the above given that at any point in time the speed has changed from it's previous speed. EDIT I can't answer my own question. But I found the question and answer is already on stackexchange: Kepler orbit : get position on the orbit over time

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• Predicted target location

  - by user3256944

  I'm having an issue with calculating the predicted linear angle a projectile needs to move in to intersect a moving enemy ship for my 2D game. I've tried following the document here, but what I've have come up with is simply awful. protected Vector2 GetPredictedPosition(float angleToEnemy, ShipCompartment origin, ShipCompartment target) { // Below obviously won't compile (document wants a Vector, not sure how to get that from a single float?) Vector2 velocity = target.Thrust - 25f; // Closing velocity (25 is example projectile velocity) Vector2 distance = target.Position - origin.Position; // Range to close double time = distance.Length() / velocity.Length(); // Time // Garbage code, doesn't compile, this method is incorrect return target.Position + (target.Thrust * time); } I would be grateful if the community can help point out how this is done correctly.

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• Help with timebased scoring algorithm

  - by Dave

  Im trying to devise an appropriate scoring system for my game. The game in essense has a finite number of tasks to complete (say 20) and the quicker you complete these task, the more points you get. I had devised a basic way of doing this using bands of time multiplied by a score for that band multiplied by the number of tasks solved within that time band i.e. (Time Band) = (Points) 1-5 sec = 15, 5-10 secs = 10, 10-20 secs = 5, 20-30 secs = 3, 40 secs onwards = 1, So for example if I did 3 tasks in the 1-5sec band i'd get 15*3=45points, if i found 10 in the 20-30sec band i'd get 3*10=30 points. Im sure there is a more mathematical way of doing this using powers of some kind but I just can't think how and hoping someone has already done something smilar.. Many thanks in advance

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• Implementing Camera Zoom in a 2D Engine

  - by Luke

  I'm currently trying to implement camera scaling/zoom in my 2D Engine. Normally I calculate the Sprite's drawing size and position similar to this pseudo code: render() { var x = sprite.x; var y = sprite.y; var sizeX = sprite.width * sprite.scaleX; // width of the sprite on the screen var sizeY = sprite.height * sprite.scaleY; // height of the sprite on the screen } To implement the scaling i changed the code to this: class Camera { var scaleX; var scaleY; var zoom; var finalScaleX; // = scaleX * zoom var finalScaleY; // = scaleY * zoom } render() { var x = sprite.x * Camera.finalScaleX; var y = sprite.y * Camera.finalScaleY; var sizeX = sprite.width * sprite.scaleX * Camera.finalScaleX; var sizeY = sprite.height * sprite.scaleY * Camera.finalScaleY; } The problem is that when the zoom is smaller than 1.0 all sprites are moved toward the top-left corner of the screen. This is expected when looking at the code but i want the camera to zoom on the center of the screen. Any tips on how to do that are welcome. :)

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• Using Bullet physics engine to find the moment of object contact before penetration

  - by MooMoo

  I would like to use Bullet Physics engine to simulate the objects in 3D world. One of the objects in the world will move using the position from 3D mouse control. I will call it "Mouse Object" and any object in the world as "Object A" I define the time before "mouse object" and "Object A" collide as t-1 The time "mouse object" penetrate "Object A" as t Now there is a problem about rendering the scene because when I move the mouse very fast, "Mouse object" will reside in "Object A" before "Object A" start to move. I would like the "Mouse Object" to stop right away attach to the "Object A". Also If the "Object A" move, the "Mouse object" should move following (attach) the "Object A" without stop at the first collision take place. This is what i did I find the position of the "Mouse Object" at time t-1 and time t. I will name it as pos(t-1) and pos(t) The contact time will be sometime between t-1 to t, which the time of contact I name it as t_contact, therefore the contact position (without penetration) between "Mouse object" and "Object A" will be pos(t_contact) then I create multiple "Mouse object"s using this equation pos[n] = pos(t-1) * C * ( pos(t) - pos(t-1) ) where 0 <= C <= 1 if I choose C = 0.1, 0.2, 0.3,0.4..... 1.0, I will get pos[n] for 10 values Then I test collision for all of these 10 "Mouse Objects" and choose the one that seperate between "no collision" and "collision". I feel this method is super non-efficient. I am not sure the way other people find the time-of-contact or the position-of-contact when "Object A" can move.

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• Rotate 2d sprite towards pointer

  - by Phil

  I'm using Crafty.js and am trying to point a sprite towards the mouse pointer. I have a function for getting the degree between two points and I'm pretty sure it works mathematically (I have it under unit tests). At least it responds that the degree between { 0,0} and {1,1} is 45, which seems right. However, when I set the sprite rotation to the returned degree, it's just wrong all the time. If I manually set it to 90, 45, etc, it gets the right direction.. I have a jsfiddle that shows what I've done so far. Any ideas?

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• 2d array permutation proof [migrated]

  - by FGM

  I want to know if it's possible to get any possible combination of a 4x4 integer array given three rules: you may shift any column up or down you may shift any row left or right you may shift the entire array left, right, up, or down That is, you can transform: [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] into any possible combination of a 4x4 array of the same 16 values, given those three rules. Basically, I just want to know if there are impossible combinations.

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• Transforms in Box2D

  - by user1264811

  I'm attempting to implement a camera in my game. I had it working for regular objects, but I began using Box2D and obviously things changed a bit. I have a Body object that I want to draw at the center of the screen. Basically what I'm doing is subtracting the viewportX and viewportY to the Body. I use this code that currently is not working as it should: public void paint(Graphics2D g, int viewportX, int viewportY) { Transform xf = new Transform(); // m_body is the Body object xf.set(m_body.getTransform()); // Here what I attemp to do is take the transform and alter it // by the viewportX and Y, which is something like **-240, -150**. // Why is it negative? Because an object has coordinates 500, 300 would be displayed // at 160, 150 when the subtraction is done. // With the DrawUtils.toScale(), it's just how I convert the units from JBox2D units // to my units. Vec2 v = Transform.mulTrans(xf, new Vec2(DrawUtils.toScale(-viewportX), DrawUtils.toScale(-viewportY))); // Set the new transform to the new vector. Keep the old angle. xf.set(v, xf.q.getAngle()); g.setColor(Color.white); // I know for a fact that the following method works 100%. It correctly displays // my object, just that it doesn't follow it. for (Fixture f = m_body.getFixtureList(); f != null; f = f.getNext()) DrawUtils.drawShape(f, xf); } Hopefully I didn't over comment this and you understand my problem. I don't want to alter the actual physics position of the object, I just want to display it in the center.

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• How do I convert screen coordinates to between -1 and 1?

  - by bbdude95

  I'm writing a function that allows me to click on my tiles. The origin for my tiles is the center, however, the mouse's origin is the top left. I need a way to transform my mouse coordinates into my tile coordinates. Here is what I already have (but is not working): void mouseClick(int button, int state, int x, int y) { x -= 400; y -= 300; float xx = x / 100; // This gets me close but the number is still high. float yy = y / 100; // It needs to be between -1 and 1 }

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• Is it possible to install a discrete mobility card on a laptop without a graphics card already?

  - by JXPheonix

  To be specific: Can I: Install a discrete graphics card on a laptop that does not come with a discrete graphics card? Teach windows 8 to use the discrete card over the integrated graphics? To me this is the only downside of my laptop and I would not mind getting any graphics card as long as it is better than the integrated laptop card (an Intel 3000) The laptop if you need more information is an Asus U46E-BAL6.

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• Optimizing mathematics on arrays of floats in Ada 95 with GNATC

  - by mat_geek

  Consider the bellow code. This code is supposed to be processing data at a fixed rate, in one second batches, It is part of an overal system and can't take up too much time. When running over 100 lots of 1 seconds worth of data the program takes 35 seconds; or 35%. How do I improce the code to get the processing time down to a minimum? The code will be running on an Intel Pentium-M which is a P3 with SSE2. package FF is new Ada.Numerics.Generic_Elementary_Functions(Float); N : constant Integer := 820; type A is array(1 .. N) of Float; type A3 is array(1 .. 3) of A; procedure F(state : in out A3; result : out A3; l : in A; r : in A) is s : Float; t : Float; begin for i in 1 .. N loop t := l(i) + r(i); t := t / 2.0; state(1)(i) := t; state(2)(i) := t * 0.25 + state(2)(i) * 0.75; state(3)(i) := t * 1.0 /64.0 + state(2)(i) * 63.0 /64.0; for r in 1 .. 3 loop s := state(r)(i); t := FF."**"(s, 6.0) + 14.0; if t > MAX then t := MAX; elsif t < MIN then t := MIN; end if; result(r)(i) := FF.Log(t, 2.0); end loop; end loop; end;

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• Using OpenGL Mathematics (GLM) in an Objective-C program

  - by user1621592

  i am trying to use GLM to load a .obj object in my Objective-C Program (Xcode 4.4 Mac Os X). I have added the glm folder to my project. i try to import it using #import "glm/glm.hpp", but the program doesn't build. some of the errors are the following: (this errors are produced in the GLM files) namespace glm{ //Unknown type name 'namespace' namespace detail { ..... it doesn't find the cstdlib, cmath, and other libraries.... This happens because my program is in Objective-c and the GLM doesn't work with this language??? How can i resolve this problem??? Thanks for your help.

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• Optimizing mathematics on arrays of floats in Ada 95 with GNAT

  - by mat_geek

  Consider the bellow code. This code is supposed to be processing data at a fixed rate, in one second batches, It is part of an overal system and can't take up too much time. When running over 100 lots of 1 seconds worth of data the program takes 35 seconds (or 35%), executing this function in a loop. The test loop is timed specifically with Ada.RealTime. The data is pregenerated so the majority of the execution time is definatetly in this loop. How do I improce the code to get the processing time down to a minimum? The code will be running on an Intel Pentium-M which is a P3 with SSE2. package FF is new Ada.Numerics.Generic_Elementary_Functions(Float); N : constant Integer := 820; type A is array(1 .. N) of Float; type A3 is array(1 .. 3) of A; procedure F(state : in out A3; result : out A3; l : in A; r : in A) is s : Float; t : Float; begin for i in 1 .. N loop t := l(i) + r(i); t := t / 2.0; state(1)(i) := t; state(2)(i) := t * 0.25 + state(2)(i) * 0.75; state(3)(i) := t * 1.0 /64.0 + state(2)(i) * 63.0 /64.0; for r in 1 .. 3 loop s := state(r)(i); t := FF."**"(s, 6.0) + 14.0; if t > MAX then t := MAX; elsif t < MIN then t := MIN; end if; result(r)(i) := FF.Log(t, 2.0); end loop; end loop; end; psuedocode for testing create two arrays of 80 random A3 arrays, called ls and rs; init the state and result A3 array record the realtime time now, called last for i in 1 .. 100 loop for j in 1 .. 80 loop F(state, result, ls(j), rs(j)); end loop; end loop; record the realtime time now, called curr output the duration between curr and last

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• Tangent of a parametric discrete curve

  - by gregseth

  I have a parametric curve, say two vectors of doubles where the parameter is the index, and I have to calculate the angle of the tangent to this curve at any given point (index). Any suggestion or link about how to do that? Thanks.

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• Matplotlib: plotting discrete values

  - by Arkapravo

  I am trying to plot the following ! from numpy import * from pylab import * import random for x in range(1,500): y = random.randint(1,25000) print(x,y) plot(x,y) show() However, I keep getting a blank graph (?). Just to make sure that the program logic is correct I added the code print(x,y), just the confirm that (x,y) pairs are being generated. (x,y) pairs are being generated, but there is no plot, I keep getting a blank graph. Any help ?

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• hi question about mathematics

  - by davit-datuashvili

  hi i have one question i know site mathoverflow.com and have posted question but unfortunately no one give me answer if i post here can anybody help me? it is not homework because i know somebody will say it is homework what u have tried but this is not so i dont know how solve please if it is possible i will post here ok?

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• The mathematics of Schellings segregation model

  - by Bruce

  For those who don't know the model. You can read this pdf. I want to find what is the probability that 2 nodes are each others neighbors when the algorithm converges (i.e. when all nodes are happy). Here's the model in a gist. You have a grid (say 10x10). You have nodes of two kind (red and green) 45 each. So we have 10 empty spaces. We randomly place the nodes on the grid. Now we scan through this grid (Exact order does not matter according to Schelling). Each node wants a specific percentage of people of same kind in its Moore neighborhood (say b = 50% for each red and green). We calculate the happiness of each node (a = Number of neighbors of same kind/Number of neighbors of different kind). If a node is unhappy (a < b) it moves to an empty cell where it knows it will be happy. This movement can change the dynamics of old as well as new neighborhood. Algorithm converges when all nodes are happy. PS - I am looking for links for any mathematical analysis of the Schelling's model.

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• Discrete problem of probability theory [closed]

  - by calejero

  A jury consists of 12 persons each of which has, before the trial started, a probability of 0.4 to vote in favor of the defendant's innocence. During the trial, the lawyer has a probability of 0.6 to change the mind of each juror who was biased against the accused. How likely is the defendant to be acquitted if he needs 10 votes in favor?

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• Mathematics errors in basic C++ program

  - by H Bomb1013

  I am working with a basic C++ program to determine the area and perimeter of a rectangle. My program works fine for whole numbers but falls apart when I use any number with a decimal. I get the impression that I am leaving something out, but since I'm a complete beginner, I have no idea what. Below is the source: #include <iostream> using namespace std; int main() { // Declared variables int length; // declares variable for length int width; // declares variable for width int area; // declares variable for area int perimeter; // declares variable for perimeter // Statements cout << "Enter the length and the width of the rectangle: "; // states what information to enter cin >> length >> width; // user input of length and width cout << endl; // closes the input area = length * width; // calculates area of rectangle perimeter = 2 * (length + width); //calculates perimeter of rectangle cout << "The area of the rectangle = " << area << " square units." <<endl; // displays the calculation of the area cout << "The perimeter of the rectangle = " << perimeter << " units." << endl; // displays the calculation of the perimeter system ("pause"); // REMOVE BEFORE RELEASE - testing purposes only return 0; }

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• Are there any (somewhat) advanced mathematics Javascript libraries?

  - by pr1001

  Are there any libraries knocking around that provide any additional general purpose math functions for Javascript? Say things like sums over a range, derivatives, integrals, etc. I can imagine that many things aren't possible, so even libraries that do rough approximations would be interesting. Thanks!

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• Mathematics and Game Programming

  - by Xfcn

  I want to program graphical 2D games more complex than the basic 2D stuff I already know. I don't want to do 3D programming. Just more complex 2D stuff. I dropped high school before I could learn a lot of stuff so I walked away with enough algebra knowledge to balance my checkbook and do some light 2D Cartesian programming. Are there any good resources out there for a guy with a limited attention span (say 20 minutes apiece for a subject I'm keenly interested in) to learn, gradually, how to do something more useful with math in programming?

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• How important is Discrete Mathematics for a Computer Scientist?

  - by mort

  As the title says, How important is Discrete Mathematics for a Computer Scientist? Background: I'm pursuing a Master's degree with a focus on fundamentals such as Algorithms, Complexity and Computability Theory and Programming Languages to get a good foundation for working in the field of Parallel Computing. Some more background: My university grants a lot of freedom in the choices of courses for my Master's degree. It's officially called "Software Engineering", but due to a the broad range of electives, a different focus is possible. Interestingly, none of the electives is a lecture in Math! I'm thinking about doing a course about Discrete Mathematics that would take half a semester to complete successfully, even if I can't use it for my degree. So with this question I'm trying to find out if the effort is justifiable.

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• Do any database "styles" use discrete files for their tables?

  - by Brad

  I've been talking to some people at work who believe some versions of a database store their data in discrete tables. That is to say you might open up a folder and see one file for each table in the database then several other supporting files. They do not have a lot of experience with databases but I have only been working with them for a little over a half year so I am not a canonical source of info either. I've been touting the benefits of SQL Server over Access (and before this, Access over Excel. Great strides have been made :) ). But, other people were of the impression that the/one of the the benefit(s) of using SQL Server over Access was that all the data was not consolidated down into one file. Yet, SQL Server packs everything into a single .mdf file (plus the log file). My question is, is there an RDBMS which holds it's data in multiple discrete files instead of one master file? And if the answer is yes, why do it one way over the other?

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• Is there really such a thing as "being good at math"?

  - by thezhaba

  Aside from gifted individuals able to perform complex calculations in their head, I'm wondering if proficiency in mathematics, namely calculus and algebra, has really got to do with one's natural inclination towards sciences, if you can put it that way. A number of students in my calculus course pick up material in seemingly no time whereas I, personally, have to spend time thinking about and understanding most concepts. Even then, if a question that requires a bit more 'imagination' comes up I don't always recognize the concepts behind it, as is the case with calculus proofs, for instance. Nevertheless, I refuse to believe that I'm simply not made for it. I do very well in programming and software engineering courses where a lot of students struggle. At first I could not grasp what they found to be so difficult, but eventually I realized that having previous programming experience is a great asset -- once I've seen and made practical use of the programming concepts learning about them in depth in an academic setting became much easier as I have then already seen their use "in the wild". I suppose I'm hoping that something similar happens with mathematics -- perhaps once the practical idea behind a concept (which authors of textbooks sure do a great job of concealing..) is evident, understanding the seemingly dry and symbolic ideas and proofs would be more obvious? I'm really not sure. All I'm sure of is I'd like to get better at calculus, but I don't yet understand why some of us pick it up easily while others have to spend considerable amounts of time on it and still not have complete understanding if an unusual problem is given.

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• why do we need advanced knowledge of mathematics & physics for programming?

  - by Sumeet

  Guys, I have been very good in mathematics and physics in my schools and colleges. Right now I am a programmer. Even in the colleges I have to engrossed my self into computers and programming things all the time. As I used to like it very much. But I have always felt the lack of advanced mathematics and physics in all the work I have done (Programs). Programming never asked me any advanced mathematics and physics knowledge in what I was very good. It always ask u some optimized loops, and different programming technologies which has never been covered in advanced mathematics and physics. Even at the time of selection in big College , such a kind of advanced knowledge is required. Time by time I got out of touch of all that facts and concepts (advanced mathematics and physics). And now after, 5 years in job I found it hard to resolve Differentiations and integrations from Trigonometry. Which sometimes make me feel like I have wasted time in those concepts because they are never used. (At that time I knew that I am going to be a programmer) If one need to be a programmer why do all this advanced knowledge is required. One can go with elementry knowledge a bit more. You never got to think like scientists and R&D person in your Schols and colleges for being a programmer? Just think and let me know your thoughts. I must be wrong somewhere in what I think , but not able to figure that out..? Regards Sumeet

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