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  • Parsing string logic issue c#

    - by N0xus
    This is a follow on from this question My program is taking in a string that is comprised of two parts: a distance value and an id number respectively. I've split these up and stored them in local variables inside my program. All of the id numbers are stored in a dictionary and are used check the incoming distance value. Though I should note that each string that gets sent into my program from the device is passed along on a single string. The next time my program receives that a signal from a device, it overrides the previous data that was there before. Should the id key coming into my program match one inside my dictionary, then a variable held next to my dictionaries key, should be updated. However, when I run my program, I don't get 6 different values, I only get the same value and they all update at the same time. This is all the code I have written trying to do this: Dictionary<string, string> myDictonary = new Dictionary<string, string>(); string Value1 = ""; string Value2 = ""; string Value3 = ""; string Value4 = ""; string Value5 = ""; string Value6 = ""; void Start() { myDictonary.Add("11111111", Value1); myDictonary.Add("22222222", Value2); myDictonary.Add("33333333", Value3); myDictonary.Add("44444444", Value4); myDictonary.Add("55555555", Value5); myDictonary.Add("66666666", Value6); } private void AppendString(string message) { testMessage = message; string[] messages = message.Split(','); foreach(string w in messages) { if(!message.StartsWith(" ")) outputContent.text += w + "\n"; } messageCount = "RSSI number " + messages[0]; uuidString = "UUID number " + messages[1]; if(myDictonary.ContainsKey(messages[1])) { Value1 = messageCount; Value2 = messageCount; Value3 = messageCount; Value4 = messageCount; Value5 = messageCount; Value6 = messageCount; } } How can I get it so that when programs recives the first key, for example 1111111, it only updates Value1? The information that comes through can be dynamic, so I'd like to avoid harding as much information as I possibly can.

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  • Ray-triangle intersetion

    - by gamemaker
    Hello! How can I test intersesion ray and triangle, and if it exist how to get distance from ray origin to intersection point?? What optimization I can use, if in my program I've got to check 1 ray to ~10000 triangles ??

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  • Approaches for Content-based Item Recommendations

    - by PartlyCloudy
    Hello, I'm currently developing an application where I want to group similar items. Items (like videos) can be created by users and also their attributes can be altered or extended later (like new tags). Instead of relying on users' preferences as most collaborative filtering mechanisms do, I want to compare item similarity based on the items' attributes (like similar length, similar colors, similar set of tags, etc.). The computation is necessary for two main purposes: Suggesting x similar items for a given item and for clustering into groups of similar items. My application so far is follows an asynchronous design and I want to decouple this clustering component as far as possible. The creation of new items or the addition of new attributes for an existing item will be advertised by publishing events the component can then consume. Computations can be provided best-effort and "snapshotted", which means that I'm okay with the best result possible at a given point in time, although result quality will eventually increase. So I am now searching for appropriate algorithms to compute both similar items and clusters. At important constraint is scalability. Initially the application has to handle a few thousand items, but later million items might be possible as well. Of course, computations will then be executed on additional nodes, but the algorithm itself should scale. It would also be nice if the algorithm supports some kind of incremental mode on partial changes of the data. My initial thought of comparing each item with each other and storing the numerical similarity sounds a little bit crude. Also, it requires n*(n-1)/2 entries for storing all similarities and any change or new item will eventually cause n similarity computations. Thanks in advance! UPDATE tl;dr To clarify what I want, here is my targeted scenario: User generate entries (think of documents) User edit entry meta data (think of tags) And here is what my system should provide: List of similar entries to a given item as recommendation Clusters of similar entries Both calculations should be based on: The meta data/attributes of entries (i.e. usage of similar tags) Thus, the distance of two entries using appropriate metrics NOT based on user votings, preferences or actions (unlike collaborative filtering). Although users may create entries and change attributes, the computation should only take into account the items and their attributes, and not the users associated with (just like a system where only items and no users exist). Ideally, the algorithm should support: permanent changes of attributes of an entry incrementally compute similar entries/clusters on changes scale something better than a simple distance table, if possible (because of the O(n²) space complexity)

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  • How can I correctly display my AVL Tree in LaTex? A solo left-child hangs straight down....

    - by cb
    The below code almost works perfectly, however the child of 9, 7, hangs straight down instead of as a left-child. How can I correct this? \usepackage{tikz} \usepackage{xytree} \begin{tikzpicture}[level/.style={sibling distance=60mm/#1}] \node [circle,draw] {4} child { node [circle,draw] {2} child {node [circle,draw] {1} } child { node [circle,draw]{3} } } child {node [circle,draw] {6} child {node [circle,draw] {5} } child {node [circle,draw] {9} child {node [circle, draw] {7}} } }; \end{tikzpicture}} Thanks, CB

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  • Syntax error while copying an multidimensional array to another in C

    - by mantuko
    We are programming a ST269 microcontroller which has two IR distance sensors. To calibrate these sensors we made one table for each sensor with the distance we measured and the corresponding value we get from the ADC. Now we want to use one function to approximate the values in between. So we defined two two-dimensional arrays (one for each sensor) as global variables. In our function we then want to copy the one array we want to work with to a working array and approximate our values. So here's the code: ... unsigned int ir_werte_re[][] = { {8,553}, ... {83,133} }; unsigned int ir_werte_li[][] = { {8,566}, ... {83,147} }; ... unsigned int geradenaproximation(unsigned int messwert, unsigned int seite) { unsigned int working_array[16][16]; unsigned int i = 0; if (seite == 0) { for (i = 0; i < sizeof(working_array); i++) { working_array[i][0] = ir_werte_li[i][0]; i++; } } else { for (i = 0; i < sizeof(working_array); i++) { working_array[i][0] = ir_werte_re[i][0]; i++; } } i = 0; unsigned int y1 = 0; unsigned int x1 = 0; ... } This code is in a file called sensor.c. We didn't write anything about our global arrays in the sensor.h should we? The sensor.h of course is included in our main.c and there the function is called. We also tried to copy the arrays via memcpy(working_array, ir_werte_li, sizeof(working_array)); And in every way we do this we get a syntax error near unsigned in the line where we're declaring unsigned int y1 = 0; and I'm pretty sure that there is no syntax error in this line : ) The last time I spend coding in C is a few years away so I'm not sure if the way we try to do this is good. Perhaps we can solve this by using a pointer instead of really copying the array or something. So please help me out I'll appreciate your bits on this.

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  • Nested WHILE loops not acting as expected - Javascript / Google Apps Script

    - by dthor
    I've got a function that isn't acting as intended. Before I continue, I'd like preface this with the fact that I normally program in Mathematica and have been tasked with porting over a Mathematica function (that I wrote) to JavaScript so that it can be used in a Google Docs spreadsheet. I have about 3 hours of JavaScript experience... The entire (small) project is calculating the Gross Die per Wafer, given a wafer and die size (among other inputs). The part that isn't working is where I check to see if any corner of the die is outside of the effective radius, Reff. The function takes a list of X and Y coordinates which, when combined, create the individual XY coord of the center of the die. That is then put into a separate function "maxDistance" that calculates the distance of each of the 4 corners and returns the max. This max value is checked against Reff. If the max is inside the radius, 1 is added to the die count. // Take a list of X and Y values and calculate the Gross Die per Wafer function CoordsToGDW(Reff,xSize,ySize,xCoords,yCoords) { // Initialize Variables var count = 0; // Nested loops create all the x,y coords of the die centers for (var i = 0; i < xCoords.length; i++) { for (var j = 0; j < yCoords.length, j++) { // Add 1 to the die count if the distance is within the effective radius if (maxDistance(xCoords[i],yCoords[j],xSize,ySize) <= Reff) {count = count + 1} } } return count; } Here are some examples of what I'm getting: xArray={-52.25, -42.75, -33.25, -23.75, -14.25, -4.75, 4.75, 14.25, 23.75, 33.25, 42.75, 52.25, 61.75} yArray={-52.5, -45.5, -38.5, -31.5, -24.5, -17.5, -10.5, -3.5, 3.5, 10.5, 17.5, 24.5, 31.5, 38.5, 45.5, 52.5, 59.5} CoordsToGDW(45,9.5,7.0,xArray,yArray) returns: 49 (should be 72) xArray={-36, -28, -20, -12, -4, 4, 12, 20, 28, 36, 44} yArray={-39, -33, -27, -21, -15, -9, -3, 3, 9, 15, 21, 27, 33, 39, 45} CoordsToGDW(32.5,8,6,xArray,yArray) returns: 39 (should be 48) I know that maxDistance() is returning the correct values. So, where's my simple mistake? Also, please forgive me writing some things in Mathematica notation... Edit #1: A little bit of formatting. Edit #2: Per showi, I've changed WHILE loops to FOR loops and replaced <= with <. Still not the right answer. It did clean things up a bit though... Edit #3: What I'm essentially trying to do is take [a,b] and [a,b,c] and return [[a,a],[a,b],[a,c],[b,a],[b,b],[b,c]]

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  • getting html tags from xml and echoing in php?

    - by Whitney Sarah Rogers
    I am trying to echo a result from xml into my html code form expedia. But I ran into a problem. There text is a little messed up: <areaInformation> Distances are calculated in a straight line from the property&apos;s location to the point of interest or attraction, and may not reflect actual travel distance. &lt;br /&gt;&lt;br /&gt; Distances are displayed to the nearest 0.1 mile and kilometre. &lt;p&gt;La Isla Shopping Mall - 0.5 km / 0.3 mi &lt;br /&gt;Yamil Lu&apos;um - 0.5 km / 0.3 mi &lt;br /&gt;Acuario Interactivo - 0.6 km / 0.3 mi &lt;br /&gt;Luxury Avenue - 1.5 km / 0.9 mi &lt;br /&gt;Cancun Golf Club at Pok Ta Pok - 2.2 km / 1.3 mi &lt;br /&gt;Nautilus Diving and Training Center - 2.6 km / 1.6 mi &lt;br /&gt;Cancun Convention Center - 2.8 km / 1.7 mi &lt;br /&gt;Plaza Caracol - 2.8 km / 1.8 mi &lt;br /&gt;Playa Tortuga - 3.1 km / 1.9 mi &lt;br /&gt;Aquaworld - 3.6 km / 2.2 mi &lt;br /&gt;Playa Langosta - 4.1 km / 2.6 mi &lt;br /&gt;Museo de Arte Popular Mexicano - 4.6 km / 2.9 mi &lt;br /&gt;Playa Linda - 5 km / 3.1 mi &lt;br /&gt;Playa Delfines - 6.1 km / 3.8 mi &lt;br /&gt;El Rey Ruins - 6.2 km / 3.8 mi &lt;br /&gt;&lt;/p&gt;&lt;p&gt;The preferred airport for ME Cancun - Complete ME All Inclusive is Cancun, Quintana Roo (CUN-Cancun Intl.) - 14.3 km / 8.9 mi. &lt;/p&gt; </areaInformation> And I echo it in php: <div id="hotelInfo"><?php echo $areaInfo ?></div> And of course I get this in the browser window: Distances are calculated in a straight line from the property's location to the point of interest or attraction, and may not reflect actual travel distance. <br /><br /> Distances are displayed to the nearest 0.1 mile and kilometre. <p>La Isla Shopping Mall - 0.5 km / 0.3 mi <br />Yamil Lu'um - 0.5 km / 0.3 mi <br />Acuario Interac etc. How can I fix this??? Any help would be greatly apreciated! Thanks!

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  • Finding good heuristic for A* search

    - by Martin
    I'm trying to find the optimal solution for a little puzzle game called Twiddle (an applet with the game can be found here). The game has a 3x3 matrix with the number from 1 to 9. The goal is to bring the numbers in the correct order using the minimum amount of moves. In each move you can rotate a 2x2 square either clockwise or counterclockwise. I.e. if you have this state 6 3 9 8 7 5 1 2 4 and you rotate the upper left 2x2 square clockwise you get 8 6 9 7 3 5 1 2 4 I'm using a A* search to find the optimal solution. My f() is simply the number of rotations need. My heuristic function already leads to the optimal solution but I don't think it's the best one you can find. My current heuristic takes each corner, looks at the number at the corner and calculates the manhatten distance to the position this number will have in the solved state (which gives me the number of rotation needed to bring the number to this postion) and sums all these values. I.e. You take the above example: 6 3 9 8 7 5 1 2 4 and this end state 1 2 3 4 5 6 7 8 9 then the heuristic does the following 6 is currently at index 0 and should by at index 5: 3 rotations needed 9 is currently at index 2 and should by at index 8: 2 rotations needed 1 is currently at index 6 and should by at index 0: 2 rotations needed 4 is currently at index 8 and should by at index 3: 3 rotations needed h = 3 + 2 + 2 + 3 = 10 But there is the problem, that you rotate 4 elements at once. So there a rare cases where you can do two (ore more) of theses estimated rotations in one move. This means theses heuristic overestimates the distance to the solution. My current workaround is, to simply excluded one of the corners from the calculation which solves this problem at least for my test-cases. I've done no research if really solves the problem or if this heuristic still overestimates in same edge-cases. So my question is: What is the best heuristic you can come up with? (Disclaimer: This is for a university project, so this is a bit of homework. But I'm free to use any resource if can come up with, so it's okay to ask you guys. Also I will credit Stackoverflow for helping me ;) )

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  • JavaFX2: Drag Event start and end coordinates

    - by user
    I have one node(ImageView) that displays an image and another node(rectangle) that resides on top of it. The behavior I need is that when the mouse is dragged(press-drag-release gesture) over the rectangle, both the nodes should move coherently. My thought process goes in the following direction: • Move both the nodes by the same distance in the direction of the drag. For this option(maybe there are more options) I need the distance between the start and end of the mouse drags. I tried capturing the start and end coordinates of the drag but have been unsuccessful. I think I am getting lost in which handlers to implement. The code I have is below: import javafx.event.EventHandler; import javafx.geometry.Rectangle2D; import javafx.scene.image.ImageView; import javafx.scene.input.MouseEvent; public class MyView { double mouseDragStartX; double mouseDragEndX; double mouseDragStartY; double mouseDragEndY; ImageView imageView; public MyView() { imageView = new ImageView("C:\\temp\\test.png"); } private void setRectangleEvents(final MyObject myObject) { myObject.getRectangle().setOnMousePressed(new EventHandler<MouseEvent>() { @Override public void handle(MouseEvent mouseEvent) { mouseDragStartX = mouseEvent.getX(); mouseDragStartY = mouseEvent.getY(); mouseEvent.consume(); } }); myObject.getRectangle().setOnMouseReleased(new EventHandler<MouseEvent>() { public void handle(MouseEvent mouseEvent) { mouseDragEndX = mouseEvent.getX(); mouseDragEndY = mouseEvent.getY(); myObjectDraggedHandler(); } }); } private void myObjectDraggedHandler() { Rectangle2D viewport = this.imageView.getViewport(); double newX = this.imageView.getImage().getWidth() + (mouseDragEndX - mouseDragStartX); double newY = this.imageView.getImage().getHeight() + (mouseDragEndY - mouseDragStartY); this.imageView.setViewport(new Rectangle2D(newX, newY, viewport.getWidth(), viewport .getHeight())); } } P.S: This code is just for indicating what I am trying to implement and will not compile correctly. Or maybe my question should just have been: How to capture the length or span of a mouse drag?

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  • Describe relative angles between points (like driving directions)

    - by aan234g
    I have a list of points with x, y coordinates. I know how to get the distance between points with sqrt(pow($x2 - $x1, 2) + pow($y2 - $y1, 2)) and the angle between points with atan2(y1 - y2, x1 - x2). How can I calculate the relative angle between the points (left, right, straight)? So, if I'm at point 1, what is the relative direction to point 2, then 2 to 3, 3 to 4, etc... Thanks for any help!

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  • mySQL query not returning correct results!

    - by Pete Herbert Penito
    Hi! This query that I have is returning therapists whose 'therapistTable.activated' is equal to false as well as those set to true! so it's basically selecting all of the db, any advice would be appreciated! ` $query = "SELECT therapistTable.* FROM therapistTable WHERE therapistTable.activated = 'true' ORDER BY therapistTable.distance "; `

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  • how to calculate geometric values in C#

    - by user321182
    i want design a dll for geometric points i have x value and y value from that i have to enter more x value and y value and two x points and two y points means.i have to find the distance...this is one dll then second class library we have to get the points from first class library and calculate slope angel

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  • Qt - controlling drag behaviour

    - by bullettime
    Suppose I want my draggable widget to move differently than just staying under my cursor while being dragged. For instance, having the widget move only in one axis, or have the widget move double the distance between the cursor and the drag starting point. Which method should I override to define this kind of behaviour?

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  • SQL SERVER Spatial Data

    - by Sam
    Hi All, I am struggeling finding an effectient way to find a distance between a Point that interetcts a polygon and the border of that polygon. I was able to use the STDistance comparing the point to every point that made up the polygon but that is taking a lot of time. Using SPatial indexed wasnt much helpful because the STDistance is not part of any constraint and even when I did put the constraint, the index didnt help much. I appreciate any feedback. Thanks.

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  • iPhone development

    - by sid
    Hi All, I am new to iPhone development. I want to make a simple iPhone application which when launched computes the distance travelled by the user,calories burnt,postion of the user,movement.Can anybody provide me the details or approach to follow to develop this application.

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  • SQL Server 2008 R2 Reporting Services - The Word is But a Stage (T-SQL Tuesday #006)

    - by smisner
    Host Michael Coles (blog|twitter) has selected LOB data as the topic for this month's T-SQL Tuesday, so I'll take this opportunity to post an overview of reporting with spatial data types. As part of my work with SQL Server 2008 R2 Reporting Services, I've been exploring the use of spatial data types in the new map data region. You can create a map using any of the following data sources: Map Gallery - a set of Shapefiles for the United States only that ships with Reporting Services ESRI Shapefile - a .shp file conforming to the Environmental Systems Research Institute, Inc. (ESRI) shapefile spatial data format SQL Server spatial data - a query that includes SQLGeography or SQLGeometry data types Rob Farley (blog|twitter) points out today in his T-SQL Tuesday post that using the SQL geography field is a preferable alternative to ESRI shapefiles for storing spatial data in SQL Server. So how do you get spatial data? If you don't already have a GIS application in-house, you can find a variety of sources. Here are a few to get you started: US Census Bureau Website, http://www.census.gov/geo/www/tiger/ Global Administrative Areas Spatial Database, http://biogeo.berkeley.edu/gadm/ Digital Chart of the World Data Server, http://www.maproom.psu.edu/dcw/ In a recent post by Pinal Dave (blog|twitter), you can find a link to free shapefiles for download and a tutorial for using Shape2SQL, a free tool to convert shapefiles into SQL Server data. In my post today, I'll show you how to use combine spatial data that describes boundaries with spatial data in AdventureWorks2008R2 that identifies stores locations to embed a map in a report. Preparing the spatial data First, I downloaded Shapefile data for the administrative boundaries in France and unzipped the data to a local folder. Then I used Shape2SQL to upload the data into a SQL Server database called Spatial. I'm not sure of the reason why, but I had to uncheck the option to create a spatial index to upload the data. Otherwise, the upload appeared to run successfully, but no table appeared in my database. The zip file that I downloaded contained three files, but I didn't know what was in them until I used Shape2SQL to upload the data into tables. Then I found that FRA_adm0 contains spatial data for the country of France, FRA_adm1 contains spatial data for each region, and FRA_adm2 contains spatial data for each department (a subdivision of region). Next I prepared my SQL query containing sales data for fictional stores selling Adventure Works products in France. The Person.Address table in the AdventureWorks2008R2 database (which you can download from Codeplex) contains a SpatialLocation column which I joined - along with several other tables - to the Sales.Customer and Sales.Store tables. I'll be able to superimpose this data on a map to see where these stores are located. I included the SQL script for this query (as well as the spatial data for France) in the downloadable project that I created for this post. Step 1: Using the Map Wizard to Create a Map of France You can build a map without using the wizard, but I find it's rather useful in this case. Whether you use Business Intelligence Development Studio (BIDS) or Report Builder 3.0, the map wizard is the same. I used BIDS so that I could create a project that includes all the files related to this post. To get started, I added an empty report template to the project and named it France Stores. Then I opened the Toolbox window and dragged the Map item to the report body which starts the wizard. Here are the steps to perform to create a map of France: On the Choose a source of spatial data page of the wizard, select SQL Server spatial query, and click Next. On the Choose a dataset with SQL Server spatial data page, select Add a new dataset with SQL Server spatial data. On the Choose a connection to a SQL Server spatial data source page, select New. In the Data Source Properties dialog box, on the General page, add a connecton string like this (changing your server name if necessary): Data Source=(local);Initial Catalog=Spatial Click OK and then click Next. On the Design a query page, add a query for the country shape, like this: select * from fra_adm1 Click Next. The map wizard reads the spatial data and renders it for you on the Choose spatial data and map view options page, as shown below. You have the option to add a Bing Maps layer which shows surrounding countries. Depending on the type of Bing Maps layer that you choose to add (from Road, Aerial, or Hybrid) and the zoom percentage you select, you can view city names and roads and various boundaries. To keep from cluttering my map, I'm going to omit the Bing Maps layer in this example, but I do recommend that you experiment with this feature. It's a nice integration feature. Use the + or - button to rexize the map as needed. (I used the + button to increase the size of the map until its edges were just inside the boundaries of the visible map area (which is called the viewport). You can eliminate the color scale and distance scale boxes that appear in the map area later. Select the Embed map data in this report for faster rendering. The spatial data won't be changing, so there's no need to leave it in the database. However, it does increase the size of the RDL. Click Next. On the Choose map visualization page, select Basic Map. We'll add data for visualization later. For now, we have just the outline of France to serve as the foundation layer for our map. Click Next, and then click Finish. Now click the color scale box in the lower left corner of the map, and press the Delete key to remove it. Then repeat to remove the distance scale box in the lower right corner of the map. Step 2: Add a Map Layer to an Existing Map The map data region allows you to add multiple layers. Each layer is associated with a different data set. Thus far, we have the spatial data that defines the regional boundaries in the first map layer. Now I'll add in another layer for the store locations by following these steps: If the Map Layers windows is not visible, click the report body, and then click twice anywhere on the map data region to display it. Click on the New Layer Wizard button in the Map layers window. And then we start over again with the process by choosing a spatial data source. Select SQL Server spatial query, and click Next. Select Add a new dataset with SQL Server spatial data, and click Next. Click New, add a connection string to the AdventureWorks2008R2 database, and click Next. Add a query with spatial data (like the one I included in the downloadable project), and click Next. The location data now appears as another layer on top of the regional map created earlier. Use the + button to resize the map again to fill as much of the viewport as possible without cutting off edges of the map. You might need to drag the map within the viewport to center it properly. Select Embed map data in this report, and click Next. On the Choose map visualization page, select Basic Marker Map, and click Next. On the Choose color theme and data visualization page, in the Marker drop-down list, change the marker to diamond. There's no particular reason for a diamond; I think it stands out a little better than a circle on this map. Clear the Single color map checkbox as another way to distinguish the markers from the map. You can of course create an analytical map instead, which would change the size and/or color of the markers according to criteria that you specify, such as sales volume of each store, but I'll save that exploration for another post on another day. Click Finish and then click Preview to see the rendered report. Et voilà...c'est fini. Yes, it's a very simple map at this point, but there are many other things you can do to enhance the map. I'll create a series of posts to explore the possibilities. Share this post: email it! | bookmark it! | digg it! | reddit! | kick it! | live it!

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  • Sliding collision response

    - by dbostream
    I have been reading plenty of tutorials about sliding collision responses yet I am not able to implement it properly in my project. What I want to do is make a puck slide along the rounded corner boards of a hockey rink. In my latest attempt the puck does slide along the boards but there are some strange velocity behaviors. First of all the puck slows down a lot pretty much right away and then it slides for awhile and stops before exiting the corner. Even if I double the speed I get a similar behavior and the puck does not make it out of the corner. I used some ideas from this document http://www.peroxide.dk/papers/collision/collision.pdf. This is what I have: Update method called from the game loop when it is time to update the puck (I removed some irrelevant parts). I use two states (current, previous) which are used to interpolate the position during rendering. public override void Update(double fixedTimeStep) { /* Acceleration is set to 0 for now. */ Acceleration.Zero(); PreviousState = CurrentState; _collisionRecursionDepth = 0; CurrentState.Position = SlidingCollision(CurrentState.Position, CurrentState.Velocity * fixedTimeStep + 0.5 * Acceleration * fixedTimeStep * fixedTimeStep); /* Should not this be affected by a sliding collision? and not only the position. */ CurrentState.Velocity = CurrentState.Velocity + Acceleration * fixedTimeStep; Heading = Vector2.NormalizeRet(CurrentState.Velocity); } private Vector2 SlidingCollision(Vector2 position, Vector2 velocity) { if(_collisionRecursionDepth > 5) return position; bool collisionFound = false; Vector2 futurePosition = position + velocity; Vector2 intersectionPoint = new Vector2(); Vector2 intersectionPointNormal = new Vector2(); /* I did not include the collision detection code, if a collision is detected the intersection point and normal in that point is returned. */ if(!collisionFound) return futurePosition; /* If no collision was detected it is safe to move to the future position. */ /* It is not exactly the intersection point, but slightly before. */ Vector2 newPosition = intersectionPoint; /* oldVelocity is set to the distance from the newPosition(intersection point) to the position it had moved to had it not collided. */ Vector2 oldVelocity = futurePosition - newPosition; /* Project the distance left to move along the intersection normal. */ Vector2 newVelocity = oldVelocity - intersectionPointNormal * oldVelocity.DotProduct(intersectionPointNormal); if(newVelocity.LengthSq() < 0.001) return newPosition; /* If almost no speed, no need to continue. */ _collisionRecursionDepth++; return SlidingCollision(newPosition, newVelocity); } What am I doing wrong with the velocity? I have been staring at this for very long so I have gone blind. I have tried different values of recursion depth but it does not seem to make it better. Let me know if you need more information. I appreciate any help. EDIT: A combination of Patrick Hughes' and teodron's answers solved the velocity problem (I think), thanks a lot! This is the new code: I decided to use a separate recursion method now too since I don't want to recalculate the acceleration in each recursion. public override void Update(double fixedTimeStep) { Acceleration.Zero();// = CalculateAcceleration(fixedTimeStep); PreviousState = new MovingEntityState(CurrentState.Position, CurrentState.Velocity); CurrentState = SlidingCollision(CurrentState, fixedTimeStep); Heading = Vector2.NormalizeRet(CurrentState.Velocity); } private MovingEntityState SlidingCollision(MovingEntityState state, double timeStep) { bool collisionFound = false; /* Calculate the next position given no detected collision. */ Vector2 futurePosition = state.Position + state.Velocity * timeStep; Vector2 intersectionPoint = new Vector2(); Vector2 intersectionPointNormal = new Vector2(); /* I did not include the collision detection code, if a collision is detected the intersection point and normal in that point is returned. */ /* If no collision was detected it is safe to move to the future position. */ if (!collisionFound) return new MovingEntityState(futurePosition, state.Velocity); /* Set new position to the intersection point (slightly before). */ Vector2 newPosition = intersectionPoint; /* Project the new velocity along the intersection normal. */ Vector2 newVelocity = state.Velocity - 1.90 * intersectionPointNormal * state.Velocity.DotProduct(intersectionPointNormal); /* Calculate the time of collision. */ double timeOfCollision = Math.Sqrt((newPosition - state.Position).LengthSq() / (futurePosition - state.Position).LengthSq()); /* Calculate new time step, remaining time of full step after the collision * current time step. */ double newTimeStep = timeStep * (1 - timeOfCollision); return SlidingCollision(new MovingEntityState(newPosition, newVelocity), newTimeStep); } Even though the code above seems to slide the puck correctly please have a look at it. I have a few questions, if I don't multiply by 1.90 in the newVelocity calculation it doesn't work (I get a stack overflow when the puck enters the corner because the timeStep decreases very slowly - a collision is found early in every recursion), why is that? what does 1.90 really do and why 1.90? Also I have a new problem, the puck does not move parallell to the short side after exiting the curve; to be more exact it moves outside the rink (I am not checking for any collisions with the short side at the moment). When I perform the collision detection I first check that the puck is in the correct quadrant. For example bottom-right corner is quadrant four i.e. circleCenter.X < puck.X && circleCenter.Y puck.Y is this a problem? or should the short side of the rink be the one to make the puck go parallell to it and not the last collision in the corner? EDIT2: This is the code I use for collision detection, maybe it has something to do with the fact that I can't make the puck slide (-1.0) but only reflect (-2.0): /* Point is the current position (not the predicted one) and quadrant is 4 for the bottom-right corner for example. */ if (GeometryHelper.PointInCircleQuadrant(circleCenter, circleRadius, state.Position, quadrant)) { /* The line is: from = state.Position, to = futurePosition. So a collision is detected when from is inside the circle and to is outside. */ if (GeometryHelper.LineCircleIntersection2d(state.Position, futurePosition, circleCenter, circleRadius, intersectionPoint, quadrant)) { collisionFound = true; /* Set the intersection point to slightly before the real intersection point (I read somewhere this was good to do because of floting point precision, not sure exactly how much though). */ intersectionPoint = intersectionPoint - Vector2.NormalizeRet(state.Velocity) * 0.001; /* Normal at the intersection point. */ intersectionPointNormal = Vector2.NormalizeRet(circleCenter - intersectionPoint) } } When I set the intersection point, if I for example use 0.1 instead of 0.001 the puck travels further before it gets stuck, but for all values I have tried (including 0 - the real intersection point) it gets stuck somewhere (but I necessarily not get a stack overflow). Can something in this part be the cause of my problem? I can see why I get the stack overflow when using -1.0 when calculating the new velocity vector; but not how to solve it. I traced the time steps used in the recursion (initial time step is always 1/60 ~ 0.01666): Recursion depth Time step next recursive call [Start recursion, time step ~ 0.016666] 0 0,000985806527246773 [No collision, stop recursion] [Start recursion, time step ~ 0.016666] 0 0,0149596704364629 1 0,0144883449376379 2 0,0143155612984837 3 0,014224925727213 4 0,0141673917461608 5 0,0141265435314026 6 0,0140953966184117 7 0,0140704653746625 ...and so on. As you can see the collision is detected early in every recursive call which means the next time step decreases very slowly thus the recursion depth gets very big - stack overflow.

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