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  • LWJGL Determining whether or not a polygon is on-screen.

    - by Brandon oubiub
    Not sure whether this is an LWJGL or math question. I want to check whether a shape is on-screen, so that I don't have to render it if it isn't. First of all, is there any simple way to do this that I am overlooking? Like some method or something that I haven't found? I'm going to assume there isn't. I tried using my trigonometry skills, but it is hard to do this because of how glRotate also distorts the image a little for perspective and realism. Or, is there any way to easily determine if a ray starting from the camera, and going outward in a straight line intersects a shape? (I can probably do it with my math skillz, but is there an easier way?) By the way, I can easily determine the angle at which the camera is facing around the x and y axis. EDIT: Or, possibly, I could get the angles of a vector from the camera to the object, and compare those angles to my camera angles. But I have a feeling that the distorts from glRotate and glTranslate would be an issue. I'll try it though.

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  • Polygon is rotating too fast

    - by Manderin87
    I am going to be using a polygon collision detection method to test when objects collide. I am attempting to rotate a polygon to match the sprites rotation. However, the polygon is rotating too fast, much faster than the sprite is. I feel its a timing issue, but the sprite rotates like it is supposed to. Can anyone look at my code and tell me what could be causing this issue? public void rotate(float x0, float y0, double angle) { for(Point point : mPoints) { float x = (float) (x0 + (point.x - x0) * Math.cos(Utilities.toRadians(angle)) - (point.y - y0) * Math.sin(Utilities.toRadians(angle))); float y = (float) (y0 + (point.x - x0) * Math.sin(Utilities.toRadians(angle)) + (point.y - y0) * Math.cos(Utilities.toRadians(angle))); point.x = x; point.y = y; } } This algorithm works when done singly, but once I plug it into the update method the rotation is too fast. The Points used are: P1 608, 368 P2 640, 464 P3 672, 400 Origin x0 is: 640 400 The angle goes from 0 to 360 as the sprite rotates. When the codes executes the triangle looks like a star because its moving so fast. The rotation is done in the sprites update method. The rotation method just increases the sprites degree by .5 when it executes. public void update() { if(isActive()) { rotate(); mBounding.rotate(mPosition.x, mPosition.y, mDegree); } }

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  • 2D Polygon Triangulation

    - by BleedObsidian
    I am creating a game engine using the JBox2D physics engine. It only allows you to create polygon fixtures up to 8 vertices, To create a body with more than 8 vertices, you need to create multiple fixtures for the body. My question is, How can I split the polygons a user creates into smaller polygons for JBox2D? Also, what topology should I use when splitting the polygons and why? (If JBox2D can have up to 8 vertices, why not split polygons into 8 per polygon)

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  • Voronoi regions of a (convex) polygon.

    - by Xavura
    I'm looking to add circle-polygon collisions to my Separating Axis Theorem collision detection. The metanet software tutorial (http://www.metanetsoftware.com/technique/tutorialA.html#section3) on SAT, which I discovered in the answer to a question I found when searching, talks about voronoi regions. I'm having trouble finding material on how I would calculate these regions for an arbitrary convex polygon and aleo how I would determine if a point is in one + which. The tutorial does contain source code but it's a .fla and I don't have Flash unfortunately.

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  • Who does non-decimal bignums with floating radix point?

    - by boost
    Nice as the Tcl libraries math::bignum and math::bigfloat are, the middle ground between the two needs to be addressed. Namely, bignums which are in different radices and have a radix point. At present math::bignum only handles integers (afaict) and math::bigfloat won't let you specify different radices to math::bigfloat::fromstr (ditto). Does anyone know of a library, for any of the major scripting languages (e.g. Tcl, Perl, Python, Ruby, Lua) or less major ones (newLISP for example), which implements bignums in different radices with handling for radix point?

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  • Algorithm to merge adjacent rectangles into polygon

    - by Glitch
    I guess that my problem is related to "convex hull", but no the same. All shapes in the drawing are rectangles with same width and height. Many are adjacent to each other. I want to combine those adjacent rectangles into polygons. Unlike "convex hull", the resuled polygons could be "hollow" inside. Is there any open source algorithm available?

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  • Linear-time algorithms for sorting vertices in polygon contours

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

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  • Fiber Channel Loop vs Point to Point

    - by RandomInsano
    So, I'm playing with a couple of QLogic QLA2340s connected directly together. I've got options here to either have them act as a loop, or in point to point mode. What's the difference if I'm only going to have two machines connected together? Is point-to-point more efficient? The firmware has an option to prefer loop, then fall back to p2p. Anyone have any idea if there are performance benefits or drawbacks? It's pretty hard to find that information.

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  • How to use WPA2 client mode in the Linux-based Cisco WAP4410N access point

    - by joechip
    I have a Cisco WAP4410N access point that I want to use as a client to connect to a WPA2 wireless network (for WLAN service monitoring purposes). Supposedly this access point supports a "Wireless Client/Repeater" mode that allows to do this. The Repeater function is optional (I have that box unchecked so that nobody can connect to this access point wirelessly). I have verified through SSH that the access point gets configured as a client and not as a Master. But it never associates to the SSID I ask it to. This is what iwconfig shows: ath04 IEEE 802.11ng ESSID:"myownssid" Mode:Managed Channel:0 Access Point: Not-Associated Bit Rate:0 kb/s Tx-Power:14 dBm Sensitivity=1/3 Retry:off RTS thr:off Fragment thr:off Encryption key:off Power Management:off Link Quality=0/94 Signal level=161/162 Noise level=161/161 Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0 Tx excessive retries:0 Invalid misc:0 Missed beacon:0 Although I've never done this from the command line, I suppose I could use wpa_supplicant or wpa_client to associate it, but I don't know how to do that without editing configuration files and the filesystem is readonly. Besides, I would have to run those commands manually after every reboot. I'd like to know how to do this the Cisco way, if possible. If not, any trick to make this work would be useful. Edit: This is with the latest firmware, 2.0.4.2. And I found that not all of the filesystem is readonly, since /var and /tmp are mounted with type ramfs.

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  • AndEngine Physics Editor loading level

    - by Khawar Raza
    I have created a .pes file using PhysicsEditor and imported as xml and have added to my project. When I parsed it and created bodies, it is showing strange behavior. The mapping of bodies that I created in PhysicsEditor is totally different what I see in my application means the shapes I draw in PhysicsEditor are rendering differently in my app. Here is my xml and code to parse and add bodies to scene. PhysicsEditor XML file: <?xml version="1.0" encoding="UTF-8"?> <!-- created with http://www.physicseditor.de --> <bodydef version="1.0"> <bodies numBodies="1"> <body name="car_path" dynamic="false" numFixtures="1"> <fixture density="2" friction="1" restitution="0" filter_categoryBits="1" filter_groupIndex="0" filter_maskBits="65535" isSensor="false" type="POLYGON" numPolygons="20" > <polygon numVertexes="6"> <vertex x="277.0000" y="152.0000" /> <vertex x="356.0000" y="172.0000" /> <vertex x="413.0000" y="194.0000" /> <vertex x="476.0000" y="223.0000" /> <vertex x="173.0000" y="232.0000" /> <vertex x="174.0000" y="148.0000" /> </polygon> <polygon numVertexes="4"> <vertex x="1556.0000" y="221.0000" /> <vertex x="1142.0000" y="94.0000" /> <vertex x="1255.0000" y="-15.0000" /> <vertex x="1554.0000" y="-14.0000" /> </polygon> <polygon numVertexes="3"> <vertex x="-192.0000" y="177.0000" /> <vertex x="-888.0000" y="139.0000" /> <vertex x="-549.0000" y="-125.0000" /> </polygon> <polygon numVertexes="6"> <vertex x="1762.0000" y="24.0000" /> <vertex x="1862.0000" y="27.0000" /> <vertex x="1927.0000" y="68.0000" /> <vertex x="2078.0000" y="222.0000" /> <vertex x="1643.0000" y="212.0000" /> <vertex x="1642.0000" y="38.0000" /> </polygon> <polygon numVertexes="3"> <vertex x="-1150.0000" y="146.0000" /> <vertex x="-1776.0000" y="140.0000" /> <vertex x="-1476.0000" y="-25.0000" /> </polygon> <polygon numVertexes="4"> <vertex x="-2799.0000" y="103.0000" /> <vertex x="-2684.0000" y="223.0000" /> <vertex x="-3112.0000" y="256.0000" /> <vertex x="-3108.0000" y="98.0000" /> </polygon> <polygon numVertexes="3"> <vertex x="3112.0000" y="255.0000" /> <vertex x="2422.0000" y="222.0000" /> <vertex x="3120.0000" y="-71.0000" /> </polygon> <polygon numVertexes="4"> <vertex x="1142.0000" y="94.0000" /> <vertex x="1556.0000" y="221.0000" /> <vertex x="709.0000" y="226.0000" /> <vertex x="911.0000" y="93.0000" /> </polygon> <polygon numVertexes="6"> <vertex x="-2111.0000" y="89.0000" /> <vertex x="-2067.0000" y="94.0000" /> <vertex x="-2002.0000" y="139.0000" /> <vertex x="-2344.0000" y="223.0000" /> <vertex x="-2196.0000" y="112.0000" /> <vertex x="-2153.0000" y="91.0000" /> </polygon> <polygon numVertexes="4"> <vertex x="105.0000" y="233.0000" /> <vertex x="-94.0000" y="178.0000" /> <vertex x="69.0000" y="106.0000" /> <vertex x="91.0000" y="104.0000" /> </polygon> <polygon numVertexes="3"> <vertex x="-2002.0000" y="139.0000" /> <vertex x="-2067.0000" y="94.0000" /> <vertex x="-2032.0000" y="110.0000" /> </polygon> <polygon numVertexes="4"> <vertex x="-1150.0000" y="146.0000" /> <vertex x="105.0000" y="233.0000" /> <vertex x="-2344.0000" y="223.0000" /> <vertex x="-2002.0000" y="139.0000" /> </polygon> <polygon numVertexes="3"> <vertex x="413.0000" y="194.0000" /> <vertex x="356.0000" y="172.0000" /> <vertex x="376.0000" y="176.0000" /> </polygon> <polygon numVertexes="3"> <vertex x="105.0000" y="233.0000" /> <vertex x="-192.0000" y="177.0000" /> <vertex x="-94.0000" y="178.0000" /> </polygon> <polygon numVertexes="4"> <vertex x="105.0000" y="233.0000" /> <vertex x="-1150.0000" y="146.0000" /> <vertex x="-888.0000" y="139.0000" /> <vertex x="-192.0000" y="177.0000" /> </polygon> <polygon numVertexes="3"> <vertex x="3112.0000" y="255.0000" /> <vertex x="-3112.0000" y="256.0000" /> <vertex x="-2684.0000" y="223.0000" /> </polygon> <polygon numVertexes="3"> <vertex x="3112.0000" y="255.0000" /> <vertex x="1556.0000" y="221.0000" /> <vertex x="1643.0000" y="212.0000" /> </polygon> <polygon numVertexes="3"> <vertex x="709.0000" y="226.0000" /> <vertex x="173.0000" y="232.0000" /> <vertex x="476.0000" y="223.0000" /> </polygon> <polygon numVertexes="3"> <vertex x="3112.0000" y="255.0000" /> <vertex x="2078.0000" y="222.0000" /> <vertex x="2422.0000" y="222.0000" /> </polygon> <polygon numVertexes="3"> <vertex x="3112.0000" y="255.0000" /> <vertex x="105.0000" y="233.0000" /> <vertex x="173.0000" y="232.0000" /> </polygon> </fixture> </body> </bodies> <metadata> <format>1</format> <ptm_ratio></ptm_ratio> </metadata> </bodydef> And here is my code: private void loadLevel() { // TODO Auto-generated method stub AssetManager assetManager = getAssets(); try { InputStream stream = assetManager.open("tmx/path1.xml"); if(stream != null) { try { DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance(); dbf.setValidating(false); dbf.setIgnoringComments(false); dbf.setIgnoringElementContentWhitespace(true); dbf.setNamespaceAware(true); DocumentBuilder db = null; db = dbf.newDocumentBuilder(); Document document = db.parse(stream); Element root = document.getDocumentElement(); NodeList bodiesNodeList = root.getElementsByTagName("bodies"); for(int i = 0; i < bodiesNodeList.getLength(); i++) { BodyDef bodyDef = new BodyDef(); bodyDef.type = BodyType.StaticBody; bodyDef.fixedRotation = true; Element bodiesElement = (Element)bodiesNodeList.item(i); NodeList bodyList = bodiesElement.getElementsByTagName("body"); for(int j = 0; j < bodyList.getLength(); j++) { Element bodyElement = (Element)bodyList.item(j); Body body = mPhysicsWorld.createBody(bodyDef); NodeList fixtureList = bodyElement.getElementsByTagName("fixture"); for(int k = 0; k < fixtureList.getLength(); k++) { Element fixtureElement = (Element)fixtureList.item(k); FixtureDef fixtureDef = new FixtureDef(); if(fixtureElement != null) { String density = fixtureElement.getAttribute("density"); String friction = fixtureElement.getAttribute("friction"); String restitution = fixtureElement.getAttribute("restitution"); fixtureDef = PhysicsFactory.createFixtureDef(Float.parseFloat(density), Float.parseFloat(friction), Float.parseFloat(restitution)); } NodeList polygonList = fixtureElement.getElementsByTagName("polygon"); if(polygonList != null && polygonList.getLength() > 0) { for(int m = 0; m < polygonList.getLength(); m++) { PolygonShape polyShape = new PolygonShape(); Element polygonElement = (Element)polygonList.item(m); NodeList vertexList = polygonElement.getElementsByTagName("vertex"); if(vertexList != null && vertexList.getLength() > 0) { Vector2 [] vectors = new Vector2[vertexList.getLength()]; for(int n = 0; n < vertexList.getLength(); n++) { Element vertexElement = (Element)vertexList.item(n); if(vertexElement != null) { float x = Float.parseFloat(vertexElement.getAttribute("x")); float y = Float.parseFloat(vertexElement.getAttribute("y")); vectors[n] = new Vector2(x/PIXEL_TO_METER_RATIO_DEFAULT, y/PIXEL_TO_METER_RATIO_DEFAULT); } } polyShape.set(vectors); fixtureDef.shape = polyShape; } body.createFixture(fixtureDef); } } } mScene.attachChild(bgSprite); mPhysicsWorld.registerPhysicsConnector(new PhysicsConnector(bgSprite, body, false, false)); } } } catch(Exception e) { e.printStackTrace(); } } } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } Any idea where I am going wrong?

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  • 2D SAT Collision Detection not working when using certain polygons (With example)

    - by sFuller
    My SAT algorithm falsely reports that collision is occurring when using certain polygons. I believe this happens when using a polygon that does not contain a right angle. Here is a simple diagram of what is going wrong: Here is the problematic code: std::vector<vec2> axesB = polygonB->GetAxes(); //loop over axes B for(int i = 0; i < axesB.size(); i++) { float minA,minB,maxA,maxB; polygonA->Project(axesB[i],&minA,&maxA); polygonB->Project(axesB[i],&minB,&maxB); float intervalDistance = polygonA->GetIntervalDistance(minA, maxA, minB, maxB); if(intervalDistance >= 0) return false; //Collision not occurring } This function retrieves axes from the polygon: std::vector<vec2> Polygon::GetAxes() { std::vector<vec2> axes; for(int i = 0; i < verts.size(); i++) { vec2 a = verts[i]; vec2 b = verts[(i+1)%verts.size()]; vec2 edge = b-a; axes.push_back(vec2(-edge.y,edge.x).GetNormailzed()); } return axes; } This function returns the normalized vector: vec2 vec2::GetNormailzed() { float mag = sqrt( x*x + y*y ); return *this/mag; } This function projects a polygon onto an axis: void Polygon::Project(vec2* axis, float* min, float* max) { float d = axis->DotProduct(&verts[0]); float _min = d; float _max = d; for(int i = 1; i < verts.size(); i++) { d = axis->DotProduct(&verts[i]); _min = std::min(_min,d); _max = std::max(_max,d); } *min = _min; *max = _max; } This function returns the dot product of the vector with another vector. float vec2::DotProduct(vec2* other) { return (x*other->x + y*other->y); } Could anyone give me a pointer in the right direction to what could be causing this bug? Edit: I forgot this function, which gives me the interval distance: float Polygon::GetIntervalDistance(float minA, float maxA, float minB, float maxB) { float intervalDistance; if (minA < minB) { intervalDistance = minB - maxA; } else { intervalDistance = minA - maxB; } return intervalDistance; //A positive value indicates this axis can be separated. } Edit 2: I have recreated the problem in HTML5/Javascript: Demo

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  • How to use Ralink RT2501/RT2573 as wifi access point in Debian Linux

    - by user60813
    Hi, I have a fit-PC server with Debian GNU/Linux (Lenny). I would like to use it as a wifi access point since my Linksys WRT54GS has become unstable. I have a USB Ralink wifi NIC. When I insert the card to USB I can see this with lsusb: Bus 001 Device 002: ID 148f:2573 Ralink Technology, Corp. RT2501/RT2573 Wireless Adapter I have tried following various HOWTOs on using wifi card as AP in Linux, however, it seems that the card cannot go into monitor mode. I believe this is because I must use a newer driver or upload non-free firmware or something like that. I have tried installed wicd, but it does not help. I bought this wifi adapter because I was told that it is one of the most common used Linux supported wifi cards that can be used as access point and a lot of other stuff. So my question is: How do I set up this USB wifi card as wireless access point in Debian Lenny?

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  • Can't find a wireless access point's IP address after changing router IP/LAN settings

    - by flagg19
    I have a modem/router, Netgear DG834, and a wireless access point (AP), Netgear WG602. The AP is directly connected to the router. My old working configuration was: Router IP address : 192.168.0.1 Access point IP address: 192.168.0.10 My new configuration is: Router IP address : 192.168.1.1 Access point IP address: ???.???.???.??? I changed my router's IP address/LAN settings to set up a VPN with another Netgear router that had the same LAN configuration. The wireless network is still up and perfectly working, but I can't find the AP's IP address. I've tried broadcast ping but the AP won't respond. I looked at the router "attached devices", but it's not there. I've played around with Nmap and arp request but the AP is totally invisible. I can fix it by resetting it to factory settings, but I'm very interested in learning more about this problem. I'm also interested in network security and this fact of having an invisible AP well, it's something I'd like to understand.

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  • Fixed point math in c#?

    - by x4000
    Hi there, I was wondering if anyone here knows of any good resources for fixed point math in c#? I've seen things like this (http://2ddev.72dpiarmy.com/viewtopic.php?id=156) and this (http://stackoverflow.com/questions/79677/whats-the-best-way-to-do-fixed-point-math), and a number of discussions about whether decimal is really fixed point or actually floating point (update: responders have confirmed that it's definitely floating point), but I haven't seen a solid C# library for things like calculating cosine and sine. My needs are simple -- I need the basic operators, plus cosine, sine, arctan2, PI... I think that's about it. Maybe sqrt. I'm programming a 2D RTS game, which I have largely working, but the unit movement when using floating-point math (doubles) has very small inaccuracies over time (10-30 minutes) across multiple machines, leading to desyncs. This is presently only between a 32 bit OS and a 64 bit OS, all the 32 bit machines seem to stay in sync without issue, which is what makes me think this is a floating point issue. I was aware from this as a possible issue from the outset, and so have limited my use of non-integer position math as much as possible, but for smooth diagonal movement at varying speeds I'm calculating the angle between points in radians, then getting the x and y components of movement with sin and cos. That's the main issue. I'm also doing some calculations for line segment intersections, line-circle intersections, circle-rect intersections, etc, that also probably need to move from floating-point to fixed-point to avoid cross-machine issues. If there's something open source in Java or VB or another comparable language, I could probably convert the code for my uses. The main priority for me is accuracy, although I'd like as little speed loss over present performance as possible. This whole fixed point math thing is very new to me, and I'm surprised by how little practical information on it there is on google -- most stuff seems to be either theory or dense C++ header files. Anything you could do to point me in the right direction is much appreciated; if I can get this working, I plan to open-source the math functions I put together so that there will be a resource for other C# programmers out there. UPDATE: I could definitely make a cosine/sine lookup table work for my purposes, but I don't think that would work for arctan2, since I'd need to generate a table with about 64,000x64,000 entries (yikes). If you know any programmatic explanations of efficient ways to calculate things like arctan2, that would be awesome. My math background is all right, but the advanced formulas and traditional math notation are very difficult for me to translate into code.

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  • Letting the user draw a Polygon Body and Image

    - by Siddharth
    In my game, I want to provide the user with a drawing feature. By free hand drawing, the user creates a polygon shape. Then, in my game implementation, I have to create a body for the found vertices and generate an image based on that polygon shape. My problem is how to create an image that matches the user-provided vertices. I've heard that cocos2d has something called Image Masking. I don't understand how I could implement it in AndEngine. Could someone help?

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  • Application window as polygon texture?

    - by nekome
    Is there a way, or method, to have some application rendered as texture in 3D scene on some polygon, and also have full interactivity with it? I'm talking about Windows platform, and maybe OpenGL but I guess it doesn't matter is it OGL or DX. For example: I run Calculator using WINAPI functions (preferably hidden, not showing on desktop) and I want to render it inside 3D scene on some polygon but still be able to type or click buttons and have it respond. My idea to realize this is to have WINAPI take screenshot (or render it to memory if possible) of that Calculator and pass it to OpenGL as texture for each frame (I'm experimenting with SDL through pygame) and for mouse interactivity to use coordination translation and calculate where on application window it would act, and then use WINAPI functions such as SetCursorPos to set cursor ant others to simulate click or something else. I haven't found any tutorials with topic similar to this one. Am I on a right track? Is there better way to do this if possible at all?

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  • finding a point on an ellipse circumference which is inside a rectangle having center point, height

    - by Shlomi Assaf
    Hi all. I have a rectangle in .NET in which I draw an ellipse. I know the width, height and center point of that rectangle. Ofcourse the cetner point of the rectangle is also the center point of the ellipse. I know how to calculate a point on a circle, however I have no clue about an ellipse. I have those parameters and an angle, i need the point on the ellipse, can someone post the formula? I saw somewhere you need to calculate 2 points in which 2 raduises will go, the sum of the radiuses will be fixed and they will change in size accordingly. I dont know how to do that, I only have the rectange height, width and center point and ofcourse the angle I wish to find the point at. thanks for any help Shlomi

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  • Point line collision reaction

    - by user4523
    I am trying to program point line segment collision detection and reaction. I am doing this for fun and to learn. The point moves (it has a velocity, and can be controlled by the user), whilst the lines are strait and stationary. The lines are not axis aligned. Everything is in 2D. It is quite straight forward to work out if a collision has occurred. For each frame, the point moves from A to B. AB is a line, and if it crosses the line segment, a collision has occurred (or will occur) and I am able to work out the point of intersection (poi). The problem I am having is with the reaction. Ideally I would like the point to be prevented from moving across the line. In one frame, I can move the point back to the poi (or only alow it to move as far as the poi), and alter the velocity. The problem I am having with this approach (I think) is that, next frame the user may try to cross the line again. Although the point is on the poi, the point may not be exactly on the line. Since it is not axis aligned, I think there is always some subtle rounding issue (A float representation of a point on a line might be rounded to a point that is slightly on one side or the other). Because of this, next frame the path might not intersect the line (because it can start on the other side and move away from it) and the point is effectively allowed to cross the line. Firstly, does the analysis sound correct? Having accepted (maybe) that I cannot always exactly position the point on the line, I tried to move the point away from the line slightly (either along the normal to the line, or along the path vector). I then get a problem at edges. Attempting to fix one collision by moving the point away from the line (even slightly) can cause it to cross another line (one shape I am dealing with is a star, with sharp corners). This can mean that the solution to one collision inadvertently creates another collision, which is ignored. Again, does this sound correct? Anyway, whatever I try, I am having difficulty with edges, and the point is occasionally able to penetrate the polygons and cross lines, which is undesirable. Whilst I can find a lot of information about collision detection on the web (and on this site) I can find precious little information on collision reaction. Does any one know of any good point line collision reaction tutorials? Or is my approach too flawed/over complicated?

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  • Portable, battery-powered, wireless access point, ethernet adapter

    - by Jed
    I am in need of an adapter that will convert an ethernet port into a wireless access point. I have found a handful of devices, but I'm unable to find a device that is battery powered. Does a self-powered wireless access point even exist? The particular scenario that I will be using the device for is not your typical computer/PC scenario. For the curious, here's a bit of background on the problem I'm trying to solve: I make devices (controllers) that monitor water systems. Our controllers have a Webserver that serves out web pages so that users can configure the controller's settings. Typically, the user will use a cross-over cable to connect directly to the controller's ethernet port with their laptop to gain access to the controller's web pages. Now that tablets (devices that don't have an ethernet port - iPad, for example) are becoming more common, I need to find a device that will convert the controller's ethernet port into a wireless access point so that the user can connect to the controller's web pages via Wi-Fi or Bluetooth. It's worth noting that this wireless device that I'm looking for will NOT be permanently installed on the controller. It will be a portable device that the user will use on any of his controllers when he needs to make a connection to the controller. If you know of a device that will solve the scenario that I mention above, please share your info.

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  • Is a point inside or outside a polygon which is on the surface of a globe

    - by richard
    How do I determine if a point is inside or outside a polygon that lies on the the surface of the earth? The inside of the polygon can be determined via the right hand rule, ie. the inside of the polygon is on your right hand side when you walk around the polygon. The polygon may Circle either pole Cross the 180 longitude Cover more than 50% of the globe As the globe is a sphere the normal ray crossing algorithms do not work correctly.

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  • Why are floating point values so prolific?

    - by Kibbee
    So, title says it all. Why are floating point values so prolific in computer programming. Due to problems like rounding errors, and not being able to even accurately represent numbers such as 0.1, I really can't see how they got as far as they did. I understand that the computation is faster with floating point numbers, however, I can think of only a few cases that they actually the right data type would be using. If you sat back and think about every time you used a floating point value, how many times did you say, well, some error would be ok, as long as the result was a few microseconds faster. It really makes me think because Jeff was talking about NP completeness, and how heuristics give an answer that is kind of right. And well, computers shouldn't do that. They should give you the answer that is correct. Yet we see floating point values used in many applications where they are completely not valid. What really bugs me, isn't that floating point exists, but that in many languages, there isn't even a viable alternative, non-floating point, decimal value. A lot of programmers when doing financial applications have to fall back to storing the number of cents in an integer field. Which brings with it all kinds of other problems. Why do floats continue to be so prolific, even though they can't represent the real answer, and we expect computers to be accurate? [EDIT] Just to clarify, I was talking about Base 2 floating points, and not base 10 floating points. .Net offers the Decimal data type, which is a base 10 floating point value which offers a much better representation of the numbers we deal with on a daily basis in most computer programs. I find it hard to believe that even modern languages like Java don't support base 10 floating point values, unless you want to move into the realm of things like BigDecimal, which isn't really the right answer either in a lot of situations.

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  • Wireless Access Point - Can't ping other machines on the wireless network

    - by Surfer513
    I have a wireless access point (Netgear), and I have it setup so that it has an IP address in the current subnet (let's say 192.168.2.0, subnet mask of 255.255.255.0). The machine that it is connected to via ethernet cable has an IP in the same subnet as the AP. The machines that are connected to the AP via the wireless connection also have an IP address in the same subnet as the rest of the network (192.168.2.0). All machines can ping the access point, but they cannot ping each other. I don't totally understand why, because there is connection and all of the machines are in the same subnet. I realize this is a layer 3 device, but is there an issue because of this AP's lack of gateway capabilities? (i.e. no routing table, etc.)

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  • Configuring a Genius GW-7200 Access Point

    - by alex
    I came across an access point we had a few years ago. I'm now trying to get it set up to work on our network. here are a couple of pictures: http://twitpic.com/194u06/full http://twitpic.com/194u0v/full I have plugged this into our network via the network port on the back. I set up a DHCP reservation, based on the MAC address on the back of the access point, however I cannot ping it, nor access the web interface. I've held down the reset button for 10 seconds, to see if that would do anything. Google doesn't come up with anything on the matter :-(

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  • 2D SAT Collision Detection not working when using certain polygons

    - by sFuller
    My SAT algorithm falsely reports that collision is occurring when using certain polygons. I believe this happens when using a polygon that does not contain a right angle. Here is a simple diagram of what is going wrong: Here is the problematic code: std::vector<vec2> axesB = polygonB->GetAxes(); //loop over axes B for(int i = 0; i < axesB.size(); i++) { float minA,minB,maxA,maxB; polygonA->Project(axesB[i],&minA,&maxA); polygonB->Project(axesB[i],&minB,&maxB); float intervalDistance = polygonA->GetIntervalDistance(minA, maxA, minB, maxB); if(intervalDistance >= 0) return false; //Collision not occurring } This function retrieves axes from the polygon: std::vector<vec2> Polygon::GetAxes() { std::vector<vec2> axes; for(int i = 0; i < verts.size(); i++) { vec2 a = verts[i]; vec2 b = verts[(i+1)%verts.size()]; vec2 edge = b-a; axes.push_back(vec2(-edge.y,edge.x).GetNormailzed()); } return axes; } This function returns the normalized vector: vec2 vec2::GetNormailzed() { float mag = sqrt( x*x + y*y ); return *this/mag; } This function projects a polygon onto an axis: void Polygon::Project(vec2* axis, float* min, float* max) { float d = axis->DotProduct(&verts[0]); float _min = d; float _max = d; for(int i = 1; i < verts.size(); i++) { d = axis->DotProduct(&verts[i]); _min = std::min(_min,d); _max = std::max(_max,d); } *min = _min; *max = _max; } This function returns the dot product of the vector with another vector. float vec2::DotProduct(vec2* other) { return (x*other->x + y*other->y); } Could anyone give me a pointer in the right direction to what could be causing this bug?

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