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  • Street-Fighting Mathematics

    Sanjoy Mahajan's new book lays out practical tools for educated guessing and down-and-dirty problem-solving Problem solving - Math - Recreations - Competitions - Methods and Theories

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  • Trac problem: AttributeError: Cannot find an implementation of the "IRequestHandler" interface named "WikiModule"

    - by Janosch
    This problem already has been described mutliple times in different mailing lists, but no solution has yet been published. My original setup is as follows (but in the mean time i have a simpler one on Windows 7): Ubuntu server with apache 2.2 and python 2.7 virutal python environment created with virtualenv installed babel, genshi and trac in this order using pip in the virtual environment Trac seems to run fine with tracd, but when visiting it through apache, i get the following error in an official trac error page: AttributeError: Cannot find an implementation of the "IRequestHandler" interface named "WikiModule" The stacktrace looks like this: Traceback (most recent call last): File "/srv/trac/python-environment/lib/python2.5/site-packages/Trac-0.13dev_r10668-py2.5.egg/trac/web/main.py",line 473, in _dispatch_request dispatcher.dispatch(req) File "/srv/trac/python-environment/lib/python2.5/site-packages/Trac-0.13dev_r10668-py2.5.egg/trac/web/main.py", line 154, in dispatch chosen_handler = self.default_handler File "/srv/trac/python-environment/lib/python2.5/site-packages/Trac-0.13dev_r10668-py2.5.egg/trac/config.py", line 691, in __get__ self.section, self.name)) AttributeError: Cannot find an implementation of the "IRequestHandler" interface named "WikiModule". Please update the option trac.default_handler in trac.ini. I already tried a lot to get down to the root of the problem, for me it looks as if all nativ trac components refuse to load. When one explicitely imports these components in the wsgi handler, some of them start to work somehow. Since i suspected the virtual environment, i dropped it, and manually copied all dependencies (babel, genshi, trac, ..) to one directory, and added this directory to system.path in the wsgi handler. I get exactly the same error. Since this setup is now independend from the environment, one can easily try it out on any other machine (windows or linux) running apache 2 and python 2.7. On my Windwos 7 machine, i got exactly the same problem. I zipped together the whole bundle, one can download it from http://www.xterity.de/tmp/trac-installation.zip . In the apache configuration (Windows 7 machine) i use the following settings: Alias /trac/chrome/common "D:/workspace/trac-installation/trac-resources/common" Alias /trac/chrome/site "D:/workspace/trac-installation/trac-resources/site" WSGIScriptAlias /trac "D:/workspace/trac-installation/apache/handler.wsgi" <Directory "D:/workspace/trac-installation/trac-resources"> Order allow,deny Allow from all </Directory> <Directory "D:/workspace/trac-installation"> Order allow,deny Allow from all </Directory> <Location "/trac"> Order allow,deny Allow from all </Location> And my handler.wsgi looks like this: import os import sys sys.path.append('D:/workspace/trac-installation/dependencies/') os.environ['TRAC_ENV'] = 'D:/workspace/trac-installation/trac-environments/Esp004' os.environ['PYTHON_EGG_CACHE'] = 'D:/workspace/trac-installation/eggs' import trac.web.main application = trac.web.main.dispatch_request Has anybody got an idea what could be the problem, or how to find out where it comes from?

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  • java.util.ConcurrentModificationException when serializing non thread-safe maps

    - by [email protected]
    We have got some questions related to exceptions thrown during a map serialization like the following one (in this example, for a LRUMap): java.util.ConcurrentModificationExceptionat org.apache.commons.collections.SequencedHashMap$OrderedIterator.next(Unknown Source)at org.apache.commons.collections.LRUMap.writeExternal(Unknown Source)at java.io.ObjectOutputStream.writeExternalData(ObjectOutputStream.java(Compiled Code))at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java(Compiled Code))at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java(Compiled Code))at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java(Inlined CompiledCode))at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java(Compiled Code))at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java(Compiled Code))at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java(Compiled Code))at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java(Inlined CompiledCode))at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java(Compiled Code))at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java(Compiled Code))at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java(Compiled Code))at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java(Inlined CompiledCode))at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java(Compiled Code))at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java(Compiled Code))at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java(Compiled Code))at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java(Compiled Code))at com.tangosol.util.ExternalizableHelper.writeSerializable(ExternalizableHelper.java(InlinedCompiled Code))at com.tangosol.util.ExternalizableHelper.writeObjectInternal(ExternalizableHelper.java(Compiled Code))at com.tangosol.util.ExternalizableHelper.serializeInternal(ExternalizableHelper.java(Compiled Code))at com.tangosol.util.ExternalizableHelper.toBinary(ExternalizableHelper.java(InlinedCompiled Code))at com.tangosol.util.ExternalizableHelper.toBinary(ExternalizableHelper.java(InlinedCompiled Code))at com.tangosol.coherence.servlet.TraditionalHttpSessionModel$OptimizedHolder.serializeValue(TraditionalHttpSessionModel.java(Inlined Compiled Code))at com.tangosol.coherence.servlet.TraditionalHttpSessionModel$OptimizedHolder.getBinary(TraditionalHttpSessionModel.java(Compiled Code)) This is caused because LRUMap is not thread safe, so if another thread is modifying the content of that same map while serialization is in progress, then the ConcurrentModificationException will be thrown. Also, the map must be synchronized. Other structures like java.util.HashMap are not thread safe too. To avoid this kind of problems, it is recommended to use a thread-safe and synchronized map such as java.util.Map, java.util.Hashtable or com.tangosol.util.SafeHashMap. You may also need to use the synchronizedMap(Map) method from Class java.util.Collections.  

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  • Will taking two years off for school destroy my 4 year old development career?

    - by rsteckly
    Hi, I know some people have asked about getting back into programming after a break and this is a potential duplicate. I just am in a position where I can go back to school in Stat/Applied Math. But I'm very worried about the impact it will have on my career and ability to find a job afterwards. I have 3 years experience in .NET on top of a couple of years in PHP. Right now, I'm a senior software engineer. Do you think taking two years off to do math is going to dramatically hurt my marketability?

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  • Installing Glassfish 3.1 on Ubuntu 10.10 Server

    - by andand
    I've used the directions here to successfully install Glassfish 3.0.1 on an virtualized (VirtualBox and VMWare) Ubuntu 10.10 Server instance without any real difficulty not resolved by more closely following the directions. However when I try applying them to Glassfish 3.1, I seem to keep getting stuck at section 6. "Security configuration before first startup". In particular, there are some differences I noted: 1) There are two keys in the default keystore. The 's1as' key is still there, but another named 'glassfish-instance' is also there. When I saw this, I deleted and recreated them both along with a 'myAlias' key which I was going to use where needed. 2) When turning the security on it seems like part of the server thinks it's on, but others don't. For instances: $ /home/glassfish/bin/asadmin set server-config.network-config.protocols.protocol.admin-listener.security-enabled=true server-config.network-config.protocols.protocol.admin-listener.security-enabled=true Command set executed successfully. $ /home/glassfish/bin/asadmin get server-config.network-config.protocols.protocol.admin-listener.security-enabled server-config.network-config.protocols.protocol.admin-listener.security-enabled=true Command get executed successfully. $ /home/glassfish/bin/asadmin --secure list-jvm-options It appears that server [localhost:4848] does not accept secure connections. Retry with --secure=false. javax.net.ssl.SSLHandshakeException: Remote host closed connection during handshake Command list-jvm-options failed. $ /home/glassfish/bin/asadmin --secure=false list-jvm-options -XX:MaxPermSize=192m -client -Djavax.management.builder.initial=com.sun.enterprise.v3.admin.AppServerMBeanServerBuilder -XX: UnlockDiagnosticVMOptions -Djava.endorsed.dirs=${com.sun.aas.installRoot}/modules/endorsed${path.separator}${com.sun.aas.installRoot}/lib/endorsed -Djava.security.policy=${com.sun.aas.instanceRoot}/config/server.policy -Djava.security.auth.login.config=${com.sun.aas.instanceRoot}/config/login.conf -Dcom.sun.enterprise.security.httpsOutboundKeyAlias=s1as -Xmx512m -Djavax.net.ssl.keyStore=${com.sun.aas.instanceRoot}/config/keystore.jks -Djavax.net.ssl.trustStore=${com.sun.aas.instanceRoot}/config/cacerts.jks -Djava.ext.dirs=${com.sun.aas.javaRoot}/lib/ext${path.separator}${com.sun.aas.javaRoot}/jre/lib/ext${path.separator}${com.sun.aas.in stanceRoot}/lib/ext -Djdbc.drivers=org.apache.derby.jdbc.ClientDriver -DANTLR_USE_DIRECT_CLASS_LOADING=true -Dcom.sun.enterprise.config.config_environment_factory_class=com.sun.enterprise.config.serverbeans.AppserverConfigEnvironmentFactory -Dorg.glassfish.additionalOSGiBundlesToStart=org.apache.felix.shell,org.apache.felix.gogo.runtime,org.apache.felix.gogo.shell,org.apache.felix.gogo.command -Dosgi.shell.telnet.port=6666 -Dosgi.shell.telnet.maxconn=1 -Dosgi.shell.telnet.ip=127.0.0.1 -Dgosh.args=--nointeractive -Dfelix.fileinstall.dir=${com.sun.aas.installRoot}/modules/autostart/ -Dfelix.fileinstall.poll=5000 -Dfelix.fileinstall.log.level=2 -Dfelix.fileinstall.bundles.new.start=true -Dfelix.fileinstall.bundles.startTransient=true -Dfelix.fileinstall.disableConfigSave=false -XX:NewRatio=2 Command list-jvm-options executed successfully. Also the admin console responds only to http (not https) requests. Thoughts?

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  • Can I use a genetic algorithm for balancing character builds?

    - by Renan Malke Stigliani
    I'm starting to build a online PVP (duel like, one-on-one) game, where there is leveling, skill points, special attacks and all the common stuff. Since I have never done anything like this, I'm still thinking about the math behind the levels/skills/specials balance. So I thought a good way of testing the best builds/combos, would be to implement a Genetic Algorithm. It'd be like this: Generate a big group of random characters Make them fight, level them up accordingly to their victories(more XP)/losses(less XP) Mate the winners, crossing their builds, to try and make even better characters Add some more random chars, emulating new players Repeat the process for some time, or util I find some chars who can beat everyone's butt I could then play with the math and try to find better balances to make sure that the top x% of chars would be a mix of various build types. So, is it a good idea, or is there some other, easier method to do the balancing?

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  • Apache2 return 404 for proxy requests before reaching WSGI

    - by Alejandro Mezcua
    I have a Django app running under Apache2 and mod_wsgi and, unfortunately, lots of requests trying to use the server as a proxy. The server is responding OK with 404 errors but the errors are generated by the Django (WSGI) app, which causes a high CPU usage. If I turn off the app and let Apache handle the response directly (send a 404), the CPU usage drops to almost 0 (mod_proxy is not enabled). Is there a way to configure Apache to respond directly to this kind of requests with an error before the request hits the WSGI app? I have seen that maybe mod_security would be an option, but I'd like to know if I can do it without it. EDIT. I'll explain it a bit more. In the logs I have lots of connections trying to use the server as a web proxy (e.g. connections like GET http://zzz.zzz/ HTTP/1.1 where zzz.zzz is an external domain, not mine). This requests are passed on to mod_wsgi which then return a 404 (as per my Django app). If I disable the app, as mod_proxy is disabled, Apache returns the error directly. What I'd finally like to do is prevent Apache from passing the request to the WSGI for invalid domains, that is, if the request is a proxy request, directly return the error and not execute the WSGI app. EDIT2. Here is the apache2 config, using VirtualHosts files in sites-enabled (i have removed email addresses and changed IPs to xxx, change the server alias to sample.sample.xxx). What I'd like is for Apache to reject any request that doesn't go to sample.sample.xxx with and error, that is, accept only relative requests to the server or fully qualified only to the actual ServerAlias. default: <VirtualHost *:80> ServerAdmin [email protected] ServerName X.X.X.X ServerAlias X.X.X.X DocumentRoot /var/www/default <Directory /> Options FollowSymLinks AllowOverride None </Directory> <Directory /var/www/> Options FollowSymLinks AllowOverride None Order allow,deny allow from all </Directory> ErrorDocument 404 "404" ErrorDocument 403 "403" ErrorDocument 500 "500" ErrorLog ${APACHE_LOG_DIR}/error.log LogLevel warn CustomLog ${APACHE_LOG_DIR}/access.log combined </VirtualHost> actual host: <VirtualHost *:80> ErrorDocument 404 "404" ErrorDocument 403 "403" ErrorDocument 500 "500" WSGIScriptAlias / /var/www/sample.sample.xxx/django.wsgi ServerAdmin [email protected] ServerAlias sample.sample.xxx ServerName sample.sample.xxx CustomLog /var/www/sample.sample.xxx/log/sample.sample.xxx-access.log combined Alias /robots.txt /var/www/sample.sample.xxx/static/robots.txt Alias /favicon.ico /var/www/sample.sample.xxx/static/favicon.ico AliasMatch ^/([^/]*\.css) /var/www/sample.sample.xxx/static/$1 Alias /static/ /var/www/sample.sample.xxx/static/ Alias /media/ /var/www/sample.sample.xxx/media/ <Directory /var/www/sample.sample.xxx/static/> Order deny,allow Allow from all </Directory> <Directory /var/www/sample.sample.xxx/media/> Order deny,allow Allow from all </Directory> </VirtualHost>

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  • FAQ: GridView Calculation with JavaScript - Displaying Quantity Total

    - by Vincent Maverick Durano
    Previously we've talked about how calculate the sub-totals and grand total in GridView here, how to format the numbers into a currency format and how to validate the quantity to just accept whole numbers using JavaScript here. One of the users in the forum (http://forums.asp.net) is asking if how to modify the script to display the quantity total in the footer. In this post I'm going to show you how to it. Basically we just need to modify the javascript CalculateTotals function and add the codes there for calculating the quantity total and display it in the footer. Here are the code blocks below:   <html xmlns="http://www.w3.org/1999/xhtml" > <head runat="server"> <title></title> <script type="text/javascript"> function CalculateTotals() { var gv = document.getElementById("<%= GridView1.ClientID %>"); var tb = gv.getElementsByTagName("input"); var lb = gv.getElementsByTagName("span"); var sub = 0; var total = 0; var indexQ = 1; var indexP = 0; var price = 0; var qty = 0; var totalQty = 0; for (var i = 0; i < tb.length; i++) { if (tb[i].type == "text") { ValidateNumber(tb[i]); price = lb[indexP].innerHTML.replace("$", "").replace(",", ""); sub = parseFloat(price) * parseFloat(tb[i].value); if (isNaN(sub)) { lb[i + indexQ].innerHTML = "0.00"; sub = 0; } else { lb[i + indexQ].innerHTML = FormatToMoney(sub, "$", ",", "."); ; } indexQ++; indexP = indexP + 2; if (isNaN(tb[i].value) || tb[i].value == "") { qty = 0; } else { qty = tb[i].value; } totalQty += parseInt(qty); total += parseFloat(sub); } } lb[lb.length - 2].innerHTML = totalQty; lb[lb.length - 1].innerHTML = FormatToMoney(total, "$", ",", "."); } function ValidateNumber(o) { if (o.value.length > 0) { o.value = o.value.replace(/[^\d]+/g, ''); //Allow only whole numbers } } function isThousands(position) { if (Math.floor(position / 3) * 3 == position) return true; return false; }; function FormatToMoney(theNumber, theCurrency, theThousands, theDecimal) { var theDecimalDigits = Math.round((theNumber * 100) - (Math.floor(theNumber) * 100)); theDecimalDigits = "" + (theDecimalDigits + "0").substring(0, 2); theNumber = "" + Math.floor(theNumber); var theOutput = theCurrency; for (x = 0; x < theNumber.length; x++) { theOutput += theNumber.substring(x, x + 1); if (isThousands(theNumber.length - x - 1) && (theNumber.length - x - 1 != 0)) { theOutput += theThousands; }; }; theOutput += theDecimal + theDecimalDigits; return theOutput; } </script> </head> <body> <form id="form1" runat="server"> <asp:gridview ID="GridView1" runat="server" ShowFooter="true" AutoGenerateColumns="false"> <Columns> <asp:BoundField DataField="RowNumber" HeaderText="Row Number" /> <asp:BoundField DataField="Description" HeaderText="Item Description" /> <asp:TemplateField HeaderText="Item Price"> <ItemTemplate> <asp:Label ID="LBLPrice" runat="server" Text='<%# Eval("Price","{0:C}") %>'></asp:Label> </ItemTemplate> <FooterTemplate> <b>Total Qty:</b> </FooterTemplate> </asp:TemplateField> <asp:TemplateField HeaderText="Quantity"> <ItemTemplate> <asp:TextBox ID="TXTQty" runat="server" onkeyup="CalculateTotals();"></asp:TextBox> </ItemTemplate> <FooterTemplate> <asp:Label ID="LBLQtyTotal" runat="server" Font-Bold="true" ForeColor="Blue" Text="0" ></asp:Label>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <b>Total Amount:</b> </FooterTemplate> </asp:TemplateField> <asp:TemplateField HeaderText="Sub-Total"> <ItemTemplate> <asp:Label ID="LBLSubTotal" runat="server" ForeColor="Green" Text="0.00"></asp:Label> </ItemTemplate> <FooterTemplate> <asp:Label ID="LBLTotal" runat="server" ForeColor="Green" Font-Bold="true" Text="0.00"></asp:Label> </FooterTemplate> </asp:TemplateField> </Columns> </asp:gridview> </form> </body> </html>   Here's the output below when you run it on the page: I hope someone find this post useful! Technorati Tags: ASP.NET,C#,JavaScript,GridView

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  • Android Can't get two virtual joysticks to move independently and at the same time

    - by Cole
    @Override public boolean onTouch(View v, MotionEvent event) { // TODO Auto-generated method stub float r = 70; float centerLx = (float) (screenWidth*.3425); float centerLy = (float) (screenHeight*.4958); float centerRx = (float) (screenWidth*.6538); float centerRy = (float) (screenHeight*.4917); float dx = 0; float dy = 0; float theta; float c; int action = event.getAction(); int actionCode = action & MotionEvent.ACTION_MASK; int pid = (action & MotionEvent.ACTION_POINTER_INDEX_MASK) >> MotionEvent.ACTION_POINTER_INDEX_SHIFT; int fingerid = event.getPointerId(pid); int x = (int) event.getX(pid); int y = (int) event.getY(pid); c = FloatMath.sqrt(dx*dx + dy*dy); theta = (float) Math.atan(Math.abs(dy/dx)); switch (actionCode) { case MotionEvent.ACTION_DOWN: case MotionEvent.ACTION_POINTER_DOWN: //if touching down on left stick, set leftstick ID to this fingerid. if(x < screenWidth/2 && c<r*.8) { lsId = fingerid; dx = x-centerLx; dy = y-centerLy; touchingLs = true; } else if(x > screenWidth/2 && c<r*.8) { rsId = fingerid; dx = x-centerRx; dy = y-centerRy; touchingRs = true; } break; case MotionEvent.ACTION_MOVE: if (touchingLs && fingerid == lsId) { dx = x - centerLx; dy = y - centerLy; }else if (touchingRs && fingerid == rsId) { dx = x - centerRx; dy = y - centerRy; } c = FloatMath.sqrt(dx*dx + dy*dy); theta = (float) Math.atan(Math.abs(dy/dx)); //if touching outside left radius and moving left stick if(c >= r && touchingLs && fingerid == lsId) { if(dx>0 && dy<0) { //top right quadrant lsX = r * FloatMath.cos(theta); lsY = -(r * FloatMath.sin(theta)); Log.i("message", "top right"); } if(dx<0 && dy<0) { //top left quadrant lsX = -(r * FloatMath.cos(theta)); lsY = -(r * FloatMath.sin(theta)); Log.i("message", "top left"); } if(dx<0 && dy>0) { //bottom left quadrant lsX = -(r * FloatMath.cos(theta)); lsY = r * FloatMath.sin(theta); Log.i("message", "bottom left"); } else if(dx > 0 && dy > 0){ //bottom right quadrant lsX = r * FloatMath.cos(theta); lsY = r * FloatMath.sin(theta); Log.i("message", "bottom right"); } } if(c >= r && touchingRs && fingerid == rsId) { if(dx>0 && dy<0) { //top right quadrant rsX = r * FloatMath.cos(theta); rsY = -(r * FloatMath.sin(theta)); Log.i("message", "top right"); } if(dx<0 && dy<0) { //top left quadrant rsX = -(r * FloatMath.cos(theta)); rsY = -(r * FloatMath.sin(theta)); Log.i("message", "top left"); } if(dx<0 && dy>0) { //bottom left quadrant rsX = -(r * FloatMath.cos(theta)); rsY = r * FloatMath.sin(theta); Log.i("message", "bottom left"); } else if(dx > 0 && dy > 0) { rsX = r * FloatMath.cos(theta); rsY = r * FloatMath.sin(theta); Log.i("message", "bottom right"); } } else { if(c < r && touchingLs && fingerid == lsId) { lsX = dx; lsY = dy; } if(c < r && touchingRs && fingerid == rsId){ rsX = dx; rsY = dy; } } break; case MotionEvent.ACTION_UP: case MotionEvent.ACTION_POINTER_UP: if (fingerid == lsId) { lsId = -1; lsX = 0; lsY = 0; touchingLs = false; } else if (fingerid == rsId) { rsId = -1; rsX = 0; rsY = 0; touchingRs = false; } break; } return true; } There's a left joystick and a right joystick. Right now only one will move at a time. If someone could set me on the right track I would be incredibly grateful cause I've been having nightmares about this problem.

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  • Security risks posed by specifying technologies used

    - by SabreWolfy
    I am developing online tools for non-commercial use, which are hosted on dedicated hardware. I would like to include logos indicating the technologies I used (Apache or Python for example), at the bottom of the page. What are the security risks/implications, if any, of "advertizing" this information? It is better not to reveal that the web server is Apache, and that I used Pyhton and jQuery, for example?

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  • Parabolic throw with set Height and range (libgdx)

    - by Tauboga
    Currently i'm working on a minigame for android where you have a rotating ball in the center of the display which jumps when touched in the direction of his current angle. I'm simply using a gravity vector and a velocity vector in this way: positionBall = positionBall.add(velocity); velocity = velocity.add(gravity); and velocity.x = (float) Math.cos(angle) * 12; /* 12 to amplify the velocity */ velocity.y = (float) Math.sin(angle) * 15; /* 15 to amplify the velocity */ That works fine. Here comes the problem: I want to make the jump look the same on all possible resolutions. The velocity needs to be scaled in a way that when the ball is thrown straight upwards it will touch the upper display border. When thrown directly left or right the range shall be exactly long enough to touch the left/right display border. Which formula(s) do I need to use and how to implement them correctly? Thanks in advance!

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  • Tomcat can't talk to MySql after outage

    - by gav
    I missed a payment for my server and hey suspended my account for a day or so. When they brought the server back up all my data was in tact but for some reason Tomcat can't make a JDBC connection to my MySql server. They both run on the same machine and hence I have a bind address of 127.0.0.1. It's strange because I have reset the machine of my own accord before without issue but clearly something has been reset in the downtime. I followed this guide (Just the bits which don't concern S3, I am not on Amazon infrastructure) originally and everything worked as expected. I'm very new to being a SysAdmin and I'm not sure what to try, how would you go about diagnosing this issue? The stack trace I get is as follows; INFO: Deploying web application archive myapp-1.1.war 2010-05-26 22:07:22,221 [main] ERROR context.ContextLoader - Context initialization failed org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'messageSource': Initialization of bean failed; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'transactionManager': Cannot resolve reference to bean 'sessionFactory' while setting bean property 'sessionFactory'; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'sessionFactory': Cannot resolve reference to bean 'hibernateProperties' while setting bean property 'hibernateProperties'; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'hibernateProperties': Cannot resolve reference to bean 'dialectDetector' while setting bean property 'properties' with key [hibernate.dialect]; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'dialectDetector': Invocation of init method failed; nested exception is org.springframework.jdbc.support.MetaDataAccessException: Could not get Connection for extracting meta data; nested exception is org.springframework.jdbc.CannotGetJdbcConnectionException: Could not get JDBC Connection; nested exception is org.apache.commons.dbcp.SQLNestedException: Cannot create PoolableConnectionFactory (Communications link failure The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:519) at org.codehaus.groovy.grails.commons.spring.ReloadAwareAutowireCapableBeanFactory.doCreateBean(ReloadAwareAutowireCapableBeanFactory.java:129) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:450) at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:290) at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222) at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:287) at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:193) at org.springframework.context.support.AbstractApplicationContext.initMessageSource(AbstractApplicationContext.java:714) at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:404) at org.codehaus.groovy.grails.commons.spring.GrailsWebApplicationContext.refresh(GrailsWebApplicationContext.java:153) ... I get this error for a number of 'beans'. If I type mysql at my command prompt then I can easily login with the same credentials as my grails app which uses GORM and Hibernate to persist objects to the DB. I might not have given enough info to start with but I'm really interested to learn and will certainly provide it if asked, I just really don't know where to start on this one. Thanks, Gav

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  • (Libgdx) Move Vector2 along angle?

    - by gemurdock
    I have seen several answers on here about moving along angle, but I can't seem to get this to work properly for me and I am new to LibGDX... just trying to learn. These are my Vector2's that I am using for this function. public Vector2 position = new Vector2(); public Vector2 velocity = new Vector2(); public Vector2 movement = new Vector2(); public Vector2 direction = new Vector2(); Here is the function that I use to move the position vector along an angle. setLocation() just sets the new location of the image. public void move(float delta, float degrees) { position.set(image.getX() + image.getWidth() / 2, image.getY() + image.getHeight() / 2); direction.set((float) Math.cos(degrees), (float) Math.sin(degrees)).nor(); velocity.set(direction).scl(speed); movement.set(velocity).scl(delta); position.add(movement); setLocation(position.x, position.y); // Sets location of image } I get a lot of different angles with this, just not the correct angles. How should I change this function to move a Vector2 along an angle using the Vector2 class from com.badlogic.gdx.math.Vector2 within the LibGDX library? I found this answer, but not sure how to implement it. Update: I figured out part of the issue. Should convert degrees to radians. However, the angle of 0 degrees is towards the right. Is there any way to fix this? As I shouldn't have to add 90 to degrees in order to have correct heading. New code is below public void move(float delta, float degrees) { degrees += 90; // Set degrees to correct heading, shouldn't have to do this position.set(image.getX() + image.getWidth() / 2, image.getY() + image.getHeight() / 2); direction.set(MathUtils.cos(degrees * MathUtils.degreesToRadians), MathUtils.sin(degrees * MathUtils.degreesToRadians)).nor(); velocity.set(direction).scl(speed); movement.set(velocity).scl(delta); position.add(movement); setLocation(position.x, position.y); }

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  • Installing Phusion Passenger 4.0.20 on Ubuntu 13.10

    - by tempestfire2002
    So I'm trying to install Passenger on the newest version of KUbuntu (13.10). I installed Apache2 using the apache2-mpm-worker package using the Muon Package Manager. And these are the commands I ran. rvmsudo gem install passenger rvmsudo passenger-install-apache2-module But I keep getting the following errors: [Fri Oct 18 15:52:13.227790 2013] [core:warn] [pid 13095] AH00111: Config variable ${APACHE_LOCK_DIR} is not defined [Fri Oct 18 15:52:13.227933 2013] [core:warn] [pid 13095] AH00111: Config variable ${APACHE_PID_FILE} is not defined [Fri Oct 18 15:52:13.227969 2013] [core:warn] [pid 13095] AH00111: Config variable ${APACHE_RUN_USER} is not defined [Fri Oct 18 15:52:13.227991 2013] [core:warn] [pid 13095] AH00111: Config variable ${APACHE_RUN_GROUP} is not defined [Fri Oct 18 15:52:13.228026 2013] [core:warn] [pid 13095] AH00111: Config variable ${APACHE_LOG_DIR} is not defined [Fri Oct 18 15:52:13.231737 2013] [core:warn] [pid 13095:tid 3074562624] AH00111: Config variable ${APACHE_RUN_DIR} is not defined [Fri Oct 18 15:52:13.232760 2013] [core:warn] [pid 13095:tid 3074562624] AH00111: Config variable ${APACHE_LOG_DIR} is not defined [Fri Oct 18 15:52:13.233043 2013] [core:warn] [pid 13095:tid 3074562624] AH00111: Config variable ${APACHE_LOG_DIR} is not defined [Fri Oct 18 15:52:13.233078 2013] [core:warn] [pid 13095:tid 3074562624] AH00111: Config variable ${APACHE_LOG_DIR} is not defined AH00526: Syntax error on line 74 of /etc/apache2/apache2.conf: Invalid Mutex directory in argument file:${APACHE_LOCK_DIR} -------------------------------------------- WARNING: Apache doesn't seem to be compiled with the 'prefork', 'worker' or 'event' MPM Phusion Passenger has only been tested on Apache with the 'prefork', the 'worker' and the 'event' MPM. Your Apache installation is compiled with the '' MPM. We recommend you to abort this installer and to recompile Apache with either the 'prefork', the 'worker' or the 'event' MPM. Press Ctrl-C to abort this installer (recommended). Press Enter if you want to continue with installation anyway. The result of my running apache2ctl -V is: Server version: Apache/2.4.6 (Ubuntu) Server built: Aug 9 2013 14:31:04 Server's Module Magic Number: 20120211:23 Server loaded: APR 1.4.8, APR-UTIL 1.5.2 Compiled using: APR 1.4.8, APR-UTIL 1.5.2 Architecture: 32-bit Server MPM: worker threaded: yes (fixed thread count) forked: yes (variable process count) Server compiled with.... -D APR_HAS_SENDFILE -D APR_HAS_MMAP -D APR_HAVE_IPV6 (IPv4-mapped addresses enabled) -D APR_USE_SYSVSEM_SERIALIZE -D APR_USE_PTHREAD_SERIALIZE -D SINGLE_LISTEN_UNSERIALIZED_ACCEPT -D APR_HAS_OTHER_CHILD -D AP_HAVE_RELIABLE_PIPED_LOGS -D DYNAMIC_MODULE_LIMIT=256 -D HTTPD_ROOT="/etc/apache2" -D SUEXEC_BIN="/usr/lib/apache2/suexec" -D DEFAULT_PIDLOG="/var/run/apache2.pid" -D DEFAULT_SCOREBOARD="logs/apache_runtime_status" -D DEFAULT_ERRORLOG="logs/error_log" -D AP_TYPES_CONFIG_FILE="mime.types" -D SERVER_CONFIG_FILE="apache2.conf" As can be seen, the server is compiled with the worker MPM, so why is passenger complaining? And how do I solve the above errors (warnings, really, but to be safe, I'd like to not have any warnings)? Thanks.

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  • How do I compile a Wikipedia lens and install?

    - by user49523
    I read a tutorial about how to compile and install a Wikipedia lens, but it didn't work. The tutorial sounds easy - i just copied and pasted to the file that was suppose to edit. I have tried some times and here are 2 edits edit 1: import logging import optparse import gettext from gettext import gettext as _ gettext.textdomain('wikipedia') from singlet.lens import SingleScopeLens, IconViewCategory, ListViewCategory from wikipedia import wikipediaconfig import urllib2 import simplejson class WikipediaLens(SingleScopeLens): wiki = "http://en.wikipedia.org" def wikipedia_query(self,search): try: search = search.replace(" ", "|") url = ("%s/w/api.php?action=opensearch&limit=25&format=json&search=%s" % (self.wiki, search)) results = simplejson.loads(urllib2.urlopen(url).read()) print "Searching Wikipedia" return results[1] except (IOError, KeyError, urllib2.URLError, urllib2.HTTPError, simplejson.JSONDecodeError): print "Error : Unable to search Wikipedia" return [] class Meta: name = 'Wikipedia' description = 'Wikipedia Lens' search_hint = 'Search Wikipedia' icon = 'wikipedia.svg' search_on_blank=True # TODO: Add your categories articles_category = ListViewCategory("Articles", "dialog-information-symbolic") def search(self, search, results): for article in self.wikipedia_query(search): results.append("%s/wiki/%s" % (self.wiki, article), "http://upload.wikimedia.org/wikipedia/commons/6/63/Wikipedia-logo.png", self.articles_category, "text/html", article, "Wikipedia Article", "%s/wiki/%s" % (self.wiki, article)) pass edit 2: import urllib2 import simplejson import logging import optparse import gettext from gettext import gettext as _ gettext.textdomain('wikipediaa') from singlet.lens import SingleScopeLens, IconViewCategory, ListViewCategory from wikipediaa import wikipediaaconfig class WikipediaaLens(SingleScopeLens): wiki = "http://en.wikipedia.org" def wikipedia_query(self,search): try: search = search.replace(" ", "|") url = ("%s/w/api.php?action=opensearch&limit=25&format=json&search=%s" % (self.wiki, search)) results = simplejson.loads(urllib2.urlopen(url).read()) print "Searching Wikipedia" return results[1] except (IOError, KeyError, urllib2.URLError, urllib2.HTTPError, simplejson.JSONDecodeError): print "Error : Unable to search Wikipedia" return [] def search(self, search, results): for article in self.wikipedia_query(search): results.append("%s/wiki/%s" % (self.wiki, article), "http://upload.wikimedia.org/wikipedia/commons/6/63/Wikipedia-logo.png", self.articles_category, "text/html", article, "Wikipedia Article", "%s/wiki/%s" % (self.wiki, article)) pass class Meta: name = 'Wikipedia' description = 'Wikipedia Lens' search_hint = 'Search Wikipedia' icon = 'wikipedia.svg' search_on_blank=True # TODO: Add your categories articles_category = ListViewCategory("Articles", "dialog-information-symbolic") def search(self, search, results): # TODO: Add your search results results.append('https://wiki.ubuntu.com/Unity/Lenses/Singlet', 'ubuntu-logo', self.example_category, "text/html", 'Learn More', 'Find out how to write your Unity Lens', 'https://wiki.ubuntu.com/Unity/Lenses/Singlet') pass so .. what can i change in the edit ? (if anybody give me the entire edit file edited i will appreciate)

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  • Compute directional light frustum from view furstum points and light direction

    - by Fabian
    I'm working on a friends engine project and my task is to construct a new frustum from the light direction that overlaps the view frustum and possible shadow casters. The project already has a function that creates a frustum for this but its way to big and includes way to many casters (shadows) which can't be seen in the view frustum. Now the only parameter of this function are the normalized light direction vector and a view class which lets me extract the 8 view frustum points in world space. I don't have any additional infos about the scene. I have read some of the related Questions here but non seem to fit very well to my problem as they often just point to cascaded shadow maps. Sadly i can't use DX or openGl functions directly because this engine has a dedicated math library. From what i've read so far the steps are: Transform view frustum points into light space and find min/max x and y values (or sometimes minima and maxima of all three axis) and create a AABB using the min/max vectors. But what comes after this step? How do i transform this new AABB back to world space? What i've done so far: CVector3 Points[8], MinLight = CVector3(FLT_MAX), MaxLight = CVector3(FLT_MAX); for(int i = 0; i<8;++i){ Points[i] = Points[i] * WorldToShadowMapMatrix; MinLight = Math::Min(Points[i],MinLight); MaxLight = Math::Max(Points[i],MaxLight); } AABox box(MinLight,MaxLight); I don't think this is the right way to do it. The near plain probably has to extend into the direction of the light source to include potentional shadow casters. I've read the Microsoft article about cascaded shadow maps http://msdn.microsoft.com/en-us/library/windows/desktop/ee416307%28v=vs.85%29.aspx which also includes some sample code. But they seem to use the scenes AABB to determine the near and far plane which I can't since i cant access this information from the funtion I'm working in. Could you guys please link some example code which shows the calculation of such frustum? Thanks in advance! Additional questio: is there a way to construct a WorldToFrustum matrix that represents the above transformation?

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  • Should I be an algorithm developer, or java web frameworks type developer?

    - by Derek
    So - as I see it, there are really two kinds of developers. Those that do frameworks, web services, pretty-making front ends, etc etc. Then there are developers that write the algorithms that solve the problem. That is, unless the problem is "display this raw data in some meaningful way." In that case, the framework/web developer guy might be doing both jobs. So my basic problem is this. I have been an algorithms kind of software developer for a few years now. I double majored in Math and Computer science, and I have a master's in systems engineering. I have never done any web-dev work, with the exception of a couple minor jobs, and some hobby level stuff. I have been job interviewing lately, and this is what happens: Job is listed as "programmer- 5 years of experience with the following: C/C++, Java,Perl, Ruby, ant, blah blah blah" Recruiter calls me, says they want me to come in for interview In the interview, find out they have some webservices development, blah blah blah When asked in the interview, talk about my experience doing algorithms, optimization, blah blah..but very willing to learn new languages, frameworks, etc Get a call back saying "we didn't think you were a fit for the job you interviewed wtih, but our algorithm team got wind of you and wants to bring you on" This has happened to me a couple times now - see a vague-ish job description looking for a "programmer" Go in, find out they are doing some sort of web-based tool, maybe with some hardcore algorithms running in the background. interview with people for the web-based tool, but get an offer from the algorithms people. So the question is - which job is the better job? I basically just want to get a wide berth of experience at this level of my career, but are algorithm developers so much in demand? Even more so than all these supposed hot in demand web developer guys? Will I be ok in the long run if I go into the niche of math based algorithm development, and just little to no, or hobby level web-dev experience? I basically just don't want to pigeon hole myself this early. My salary is already starting to get pretty high - and I can see a company later on saying "we really need a web developer, but we'll hire this 50k/year college guy, instead of this 100k/year experience algorithm guy" Cliffs notes: I have been doing algorithm development. I consider myself to be a "good programmer." I would have no problem picking up web technologies and those sorts of frameworks. During job interviews, I keep getting "we think you've got a good skillset - talk to our algorithm team" instead of wanting me to learn new skills on the job to do their web services or whhatever other new technology they are doing. Edit: Whenever I am talking about algorithm development here - I am talking about the code that produces the answer. Typically I think of more math-based algorithms: solving a financial problem, solving a finite element method, image processing, etc

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  • How to configure apache2 to just save certain POST requests without even passing them to application?

    - by Robert Grezan
    I'm running apache in front of glassfish server using BalancerMember. For performance reasons I would like that POST requests on certain endpoint are just saved to a file without passing them to application (and to return correct HTTP return code). How to configure apache to do that? EDIT: In other words, if a POST request is for path "http://example.com/upload" then the content of the post (body) should go into a file.

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  • How to make this game loop deterministic

    - by Lanaru
    I am using the following game loop for my pacman clone: long prevTime = System.currentTimeMillis(); while (running) { long curTime = System.currentTimeMillis(); float frameTime = (curTime - prevTime) / 1000f; prevTime = curTime; while (frameTime > 0.0f) { final float deltaTime = Math.min(frameTime, TIME_STEP); update(deltaTime); frameTime -= deltaTime; } repaint(); } The thing is, I don't always get the same ghost movement every time I run the game (their logic is deterministic), so it must be the game loop. I imagine it's due to the final float deltaTime = Math.min(frameTime, TIME_STEP); line. What's the best way of modifying this to perform the exact same way every time I run it? Also, any further improvements I can make?

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  • Dependency Checker/ Installer With Java/Ant

    - by jsn
    I need some kind of software to easily roll out code on new servers. I use Apache Ant for builds. However, say I want to set-up a new server fast and my Java program depends on GhostScript, if there any software that can automatically check the computer for it (and then maybe the PATH) and add it if is not there? I have already looked at Maven and Apache Ivy, however, I think these are only for .jar files (from what I saw). Thanks for any help.

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  • Trying to implement fling events on an object

    - by Adam Short
    I have a game object, well a bitmap, which I'd like to "fling". I'm struggling to get it to fling ontouchlistener due to it being a bitmap and not sure how to proceed and I'm struggling to find the resources to help. Here's my code so far: https://github.com/addrum/Shapes GameActivity class: package com.main.shapes; import android.app.Activity; import android.content.Context; import android.graphics.Bitmap; import android.graphics.BitmapFactory; import android.graphics.Canvas; import android.os.Bundle; import android.view.GestureDetector; import android.view.MotionEvent; import android.view.SurfaceHolder; import android.view.SurfaceView; import android.view.View.OnTouchListener; import android.view.Window; public class GameActivity extends Activity { private GestureDetector gestureDetector; View view; Bitmap ball; float x, y; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); //Remove title bar this.requestWindowFeature(Window.FEATURE_NO_TITLE); view = new View(this); ball = BitmapFactory.decodeResource(getResources(), R.drawable.ball); gestureDetector = new GestureDetector(this, new GestureListener()); x = 0; y = 0; setContentView(view); ball.setOnTouchListener(new OnTouchListener() { @Override public boolean onTouch(android.view.View v, MotionEvent event) { // TODO Auto-generated method stub return false; } }); } @Override protected void onPause() { super.onPause(); view.pause(); } @Override protected void onResume() { super.onResume(); view.resume(); } public class View extends SurfaceView implements Runnable { Thread thread = null; SurfaceHolder holder; boolean canRun = false; public View(Context context) { super(context); holder = getHolder(); } public void run() { while (canRun) { if (!holder.getSurface().isValid()) { continue; } Canvas c = holder.lockCanvas(); c.drawARGB(255, 255, 255, 255); c.drawBitmap(ball, x - (ball.getWidth() / 2), y - (ball.getHeight() / 2), null); holder.unlockCanvasAndPost(c); } } public void pause() { canRun = false; while (true) { try { thread.join(); } catch (InterruptedException e) { e.printStackTrace(); } break; } thread = null; } public void resume() { canRun = true; thread = new Thread(this); thread.start(); } } } GestureListener class: package com.main.shapes; import android.view.GestureDetector.SimpleOnGestureListener; import android.view.MotionEvent; public class GestureListener extends SimpleOnGestureListener { private static final int SWIPE_MIN_DISTANCE = 120; private static final int SWIPE_THRESHOLD_VELOCITY = 200; @Override public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) { if (e1.getX() - e2.getX() > SWIPE_MIN_DISTANCE && Math.abs(velocityX) > SWIPE_THRESHOLD_VELOCITY) { //From Right to Left return true; } else if (e2.getX() - e1.getX() > SWIPE_MIN_DISTANCE && Math.abs(velocityX) > SWIPE_THRESHOLD_VELOCITY) { //From Left to Right return true; } if (e1.getY() - e2.getY() > SWIPE_MIN_DISTANCE && Math.abs(velocityY) > SWIPE_THRESHOLD_VELOCITY) { //From Bottom to Top return true; } else if (e2.getY() - e1.getY() > SWIPE_MIN_DISTANCE && Math.abs(velocityY) > SWIPE_THRESHOLD_VELOCITY) { //From Top to Bottom return true; } return false; } @Override public boolean onDown(MotionEvent e) { //always return true since all gestures always begin with onDown and<br> //if this returns false, the framework won't try to pick up onFling for example. return true; } }

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  • Applications: The mathematics of movement, Part 1

    - by TechTwaddle
    Before you continue reading this post, a suggestion; if you haven’t read “Programming Windows Phone 7 Series” by Charles Petzold, go read it. Now. If you find 150+ pages a little too long, at least go through Chapter 5, Principles of Movement, especially the section “A Brief Review of Vectors”. This post is largely inspired from this chapter. At this point I assume you know what vectors are, how they are represented using the pair (x, y), what a unit vector is, and given a vector how you would normalize the vector to get a unit vector. Our task in this post is simple, a marble is drawn at a point on the screen, the user clicks at a random point on the device, say (destX, destY), and our program makes the marble move towards that point and stop when it is reached. The tricky part of this task is the word “towards”, it adds a direction to our problem. Making a marble bounce around the screen is simple, all you have to do is keep incrementing the X and Y co-ordinates by a certain amount and handle the boundary conditions. Here, however, we need to find out exactly how to increment the X and Y values, so that the marble appears to move towards the point where the user clicked. And this is where vectors can be so helpful. The code I’ll show you here is not ideal, we’ll be working with C# on Windows Mobile 6.x, so there is no built-in vector class that I can use, though I could have written one and done all the math inside the class. I think it is trivial to the actual problem that we are trying to solve and can be done pretty easily once you know what’s going on behind the scenes. In other words, this is an excuse for me being lazy. The first approach, uses the function Atan2() to solve the “towards” part of the problem. Atan2() takes a point (x, y) as input, Atan2(y, x), note that y goes first, and then it returns an angle in radians. What angle you ask. Imagine a line from the origin (0, 0), to the point (x, y). The angle which Atan2 returns is the angle the positive X-axis makes with that line, measured clockwise. The figure below makes it clear, wiki has good details about Atan2(), give it a read. The pair (x, y) also denotes a vector. A vector whose magnitude is the length of that line, which is Sqrt(x*x + y*y), and a direction ?, as measured from positive X axis clockwise. If you’ve read that chapter from Charles Petzold’s book, this much should be clear. Now Sine and Cosine of the angle ? are special. Cosine(?) divides x by the vectors length (adjacent by hypotenuse), thus giving us a unit vector along the X direction. And Sine(?) divides y by the vectors length (opposite by hypotenuse), thus giving us a unit vector along the Y direction. Therefore the vector represented by the pair (cos(?), sin(?)), is the unit vector (or normalization) of the vector (x, y). This unit vector has a length of 1 (remember sin2(?) + cos2(?) = 1 ?), and a direction which is the same as vector (x, y). Now if I multiply this unit vector by some amount, then I will always get a point which is a certain distance away from the origin, but, more importantly, the point will always be on that line. For example, if I multiply the unit vector with the length of the line, I get the point (x, y). Thus, all we have to do to move the marble towards our destination point, is to multiply the unit vector by a certain amount each time and draw the marble, and the marble will magically move towards the click point. Now time for some code. The application, uses a timer based frame draw method to draw the marble on the screen. The timer is disabled initially and whenever the user clicks on the screen, the timer is enabled. The callback function for the timer follows the standard Update and Draw cycle. private double totLenToTravelSqrd = 0; private double startPosX = 0, startPosY = 0; private double destX = 0, destY = 0; private void Form1_MouseUp(object sender, MouseEventArgs e) {     destX = e.X;     destY = e.Y;     double x = marble1.x - destX;     double y = marble1.y - destY;     //calculate the total length to be travelled     totLenToTravelSqrd = x * x + y * y;     //store the start position of the marble     startPosX = marble1.x;     startPosY = marble1.y;     timer1.Enabled = true; } private void timer1_Tick(object sender, EventArgs e) {     UpdatePosition();     DrawMarble(); } Form1_MouseUp() method is called when ever the user touches and releases the screen. In this function we save the click point in destX and destY, this is the destination point for the marble and we also enable the timer. We store a few more values which we will use in the UpdatePosition() method to detect when the marble has reached the destination and stop the timer. So we store the start position of the marble and the square of the total length to be travelled. I’ll leave out the term ‘sqrd’ when speaking of lengths from now on. The time out interval of the timer is set to 40ms, thus giving us a frame rate of about ~25fps. In the timer callback, we update the marble position and draw the marble. We know what DrawMarble() does, so here, we’ll only look at how UpdatePosition() is implemented; private void UpdatePosition() {     //the vector (x, y)     double x = destX - marble1.x;     double y = destY - marble1.y;     double incrX=0, incrY=0;     double distanceSqrd=0;     double speed = 6;     //distance between destination and current position, before updating marble position     distanceSqrd = x * x + y * y;     double angle = Math.Atan2(y, x);     //Cos and Sin give us the unit vector, 6 is the value we use to magnify the unit vector along the same direction     incrX = speed * Math.Cos(angle);     incrY = speed * Math.Sin(angle);     marble1.x += incrX;     marble1.y += incrY;     //check for bounds     if ((int)marble1.x < MinX + marbleWidth / 2)     {         marble1.x = MinX + marbleWidth / 2;     }     else if ((int)marble1.x > (MaxX - marbleWidth / 2))     {         marble1.x = MaxX - marbleWidth / 2;     }     if ((int)marble1.y < MinY + marbleHeight / 2)     {         marble1.y = MinY + marbleHeight / 2;     }     else if ((int)marble1.y > (MaxY - marbleHeight / 2))     {         marble1.y = MaxY - marbleHeight / 2;     }     //distance between destination and current point, after updating marble position     x = destX - marble1.x;     y = destY - marble1.y;     double newDistanceSqrd = x * x + y * y;     //length from start point to current marble position     x = startPosX - (marble1.x);     y = startPosY - (marble1.y);     double lenTraveledSqrd = x * x + y * y;     //check for end conditions     if ((int)lenTraveledSqrd >= (int)totLenToTravelSqrd)     {         System.Console.WriteLine("Stopping because destination reached");         timer1.Enabled = false;     }     else if (Math.Abs((int)distanceSqrd - (int)newDistanceSqrd) < 4)     {         System.Console.WriteLine("Stopping because no change in Old and New position");         timer1.Enabled = false;     } } Ok, so in this function, first we subtract the current marble position from the destination point to give us a vector. The first three lines of the function construct this vector (x, y). The vector (x, y) has the same length as the line from (marble1.x, marble1.y) to (destX, destY) and is in the direction pointing from (marble1.x, marble1.y) to (destX, destY). Note that marble1.x and marble1.y denote the center point of the marble. Then we use Atan2() to get the angle which this vector makes with the positive X axis and use Cosine() and Sine() of that angle to get the unit vector along that same direction. We multiply this unit vector with 6, to get the values which the position of the marble should be incremented by. This variable, speed, can be experimented with and determines how fast the marble moves towards the destination. After this, we check for bounds to make sure that the marble stays within the screen limits and finally we check for the end condition and stop the timer. The end condition has two parts to it. The first case is the normal case, where the user clicks well inside the screen. Here, we stop when the total length travelled by the marble is greater than or equal to the total length to be travelled. Simple enough. The second case is when the user clicks on the very corners of the screen. Like I said before, the values marble1.x and marble1.y denote the center point of the marble. When the user clicks on the corner, the marble moves towards the point, and after some time tries to go outside of the screen, this is when the bounds checking comes into play and corrects the marble position so that the marble stays inside the screen. In this case the marble will never travel a distance of totLenToTravelSqrd, because of the correction is its position. So here we detect the end condition when there is not much change in marbles position. I use the value 4 in the second condition above. After experimenting with a few values, 4 seemed to work okay. There is a small thing missing in the code above. In the normal case, case 1, when the update method runs for the last time, marble position over shoots the destination point. This happens because the position is incremented in steps (which are not small enough), so in this case too, we should have corrected the marble position, so that the center point of the marble sits exactly on top of the destination point. I’ll add this later and update the post. This has been a pretty long post already, so I’ll leave you with a video of how this program looks while running. Notice in the video that the marble moves like a bot, without any grace what so ever. And that is because the speed of the marble is fixed at 6. In the next post we will see how to make the marble move a little more elegantly. And also, if Atan2(), Sine() and Cosine() are a little too much to digest, we’ll see how to achieve the same effect without using them, in the next to next post maybe. Ciao!

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