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  • what practical proofs are there about the Turing completeness of neural nets? what nns can execute c

    - by Albert
    I'm interested in the computational power of neural nets. It is generally accepted that recurrent neural nets are Turing complete. Now I was searching for some papers which proofs this. What I found so far: Turing computability with neural nets, Hava T. Siegelmann and Eduardo D. Sontag, 1991 I think this is only interesting from a theoretical point of view because it needs to have the neuron activity of infinite exactness (to encode the state somehow as a rational number). S. Franklin and M. Garzon, Neural computability This needs an unbounded number of neurons and also doesn't really seem to be that much practical. (Note that another question of mine tries to point out this kind of problem between such theoretical results and the practice.) I'm searching mostly for some neural net which really can execute some code which I can also simulate and test in practice. Of course, in practice, they would have some kind of limited memory. Does anyone know something like this?

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  • What is the optimal number of threads for performing IO operations in java?

    - by marc
    In Goetz's "Java Concurrency in Practice", in a footnote on page 101, he writes "For computational problems like this that do not I/O and access no shared data, Ncpu or Ncpu+1 threads yield optimal throughput; more threads do not help, and may in fact degrade performance..." My question is, when performing I/O operations such as file writing, file reading, file deleting, etc, are there guidelines for the number of threads to use to achieve maximum performance? I understand this will be just a guide number, since disk speeds and a host of other factors play into this. Still, I'm wondering: can 20 threads write 1000 separate files to disk faster than 4 threads can on a 4-cpu machine?

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  • How long can a hash left out in the open be considered safe?

    - by Xeoncross
    If I were to leave a SHA2 family hash out on my website - how long would it be considered safe? How long would I have before I could be sure that someone would find a collision for it and know what was hashed? I know that the amount of time would be based on the computational power of the one seeking to break it. It would also depend on the string length, but I'm curious just how secure hashes are. Since many of us run web-servers we constantly have to be prepared for the day when someone might make it all the way to the database which stores the user hashes. So, move the server security out of the way and then what do you have? This is a slightly theoretical area for many of the people I have talked with, so I would love to actually have some more information about average expectations for cracking.

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  • Why are C, C++, and LISP so prevalent in embedded devices and robots?

    - by David
    It seems that the software language skills most sought for embedded devices and robots are C, C++, and LISP. Why haven't more recent languages made inroads into these applications? For example, Erlang would seem particularly well-suited to robotic applications, since it makes concurrent programming easier and allows hot swapping of code. Python would seem to be useful, if for no other reason than its support of multiple programming paradigms. I'm even surprised that Java hasn't made a foray into general robotic programming. I'm sure one argument would be, "Some newer languages are interpreted, not compiled" - implying that compiled languages are quicker and use fewer computational resources. Is this still the case, in a time when we can put a Java Virtual Machine on a cell phone or a SunSpot? (and isn't LISP interpreted anyway?)

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  • C++ Virtual keyword as away to avoid including code units.

    - by user394663
    Currently we have a body of code that allows service plugins which offer forms of communication to the core e.g tcp/ip, udp/ip, usb, etc... These service plugins feedback notifier class instances to the core for further processing. In the current implementation a service project (which is a separate dynamically linked library brought in at runtime by the core via dlopen and friends) will compile against the notifier.cpp file that resides in the core source code (a separate project). This gives access to the notifiers method implementations. This works perfectly no complaints. Two alternative options: 1. put the notifier method implementations in the header file. 2. declare the notifier methods virtual and delay binding until runtime. Avoiding the issues of computational overhead what are the impacts of option 2? Are there any other options available to us? Thanks

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  • What technologies to use for a particle system with enormous calculation demand?

    - by Amir Rezaei
    I have a particle system with X particles. Each particle tests for collision with other particles. This gives X*X = X^2 collision tests per frame. For 60f/s, this corresponds to 60*X^2 collision detection per second. What is the best technological approach for these intensive calculations? Should I use F#, C, C++ or C#, or something else? The following are constraints The code is written in C# with the latest XNA Multi-threaded may be considered No special algorithm that tests the collision with the nearest neighbors or that reduces the problem The last constraint may be strange, so let me explain. Regardless constraint 3, given a problem with enormous computational requirement what would be the best approach to solve the problem. An algorithm reduces the problem; still the same algorithm may behave different depending on technology. Consider pros and cons of CLR vs native C.

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  • Interactive Charts for web application

    - by user227290
    We are working on a web based application (implemented in JAVA) on commodity prices and one part of it is interactive charting. I provide a simplified example here. We have a table in Mysql database where we have information on commodity prices in US states and counties. One aspect of the application is to create interactive plots based on user choice. For example, if the user needs to see the price density in Oregon and Linn county then she chooses it from the menu in a webpage and it is rendered on fly with accompanying quantile information in a table. As the user changes state and county these plots and table change on fly.For our computational need we are using R (and use rjava to integrate it to our web application) and I know that if interactivity is not an issue this is a piece of cake in ggplot2, but I am not aware of any interactive version of R graphics framework (like lattice, ggplot2). We are exploring google visualization API but I am not sure we can have the statistical power we need in some of the plots.Please help.

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  • Mapping a Vertex Buffer in DirectX11

    - by judeclarke
    I have a VertexBuffer that I am remapping on a per frame base for a bunch of quads that are constantly updated, sharing the same material\index buffer but have different width/heights. However, currently right now there is a really bad flicker on this geometry. Although it is flickering, the flicker looks correct. I know it is the vertex buffer mapping because if I recreate the entire VB then it will render fine. However, as an optimization I figured I would just remap it. Does anyone know what the problem is? The length (width, size) of the vertex buffer is always the same. One might think it is double buffering, however, it would not be double buffering because it only happens when I map/unmap the buffer, so that leads me to believe that I am setting some parameters wrong on the creation or mapping. I am using DirectX11, my initialization and remap code are: Initialization code D3D11_BUFFER_DESC bd; ZeroMemory( &bd, sizeof(bd) ); bd.Usage = D3D11_USAGE_DYNAMIC; bd.ByteWidth = vertCount * vertexTypeWidth; bd.BindFlags = D3D11_BIND_VERTEX_BUFFER; //bd.CPUAccessFlags = 0; bd.CPUAccessFlags = D3D11_CPU_ACCESS_WRITE; D3D11_SUBRESOURCE_DATA InitData; ZeroMemory( &InitData, sizeof(InitData) ); InitData.pSysMem = vertices; mVertexType = vertexType; HRESULT hResult = device->CreateBuffer( &bd, &InitData, &m_pVertexBuffer ); // This will be S_OK if(hResult != S_OK) return false; Remap code D3D11_MAPPED_SUBRESOURCE resource; HRESULT hResult = deviceContext->Map(m_pVertexBuffer, 0, D3D11_MAP_WRITE_DISCARD, 0, &resource); // This will be S_OK if(hResult != S_OK) return false; resource.pData = vertices; deviceContext->Unmap(m_pVertexBuffer, 0);

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  • How do I create a popup banner before login with Lightdm?

    - by Rich Loring
    When Ubuntu was using gnome I was able to create a popup banner like the banner below before the login screen using zenity in the /etc/gdm/Init/Default. The line of code would be like this: if [ -f "/usr/bin/zenity" ]; then /usr/bin/zenity --info --text="`cat /etc/issue`" --no-wrap; else xmessage -file /etc/issue -button ok -geometry 540X480; fi How can I accomplish this with Unity? NOTICE TO USERS This is a Federal computer system (and/or it is directly connected to a BNL local network system) and is the property of the United States Government. It is for authorized use only. Users (authorized or unauthorized) have no explicit or implicit expectation of privacy. Any or all uses of this system and all files on this system may be intercepted, monitored, recorded, copied, audited, inspected, and disclosed to authorized site, Department of Energy, and law enforcement personnel, as well as authorized officials of other agencies, both domestic and foreign. By using this system, the user consents to such interception, monitoring, recording, copying, auditing, inspection, and disclosure at the discretion of authorized site or Department of Energy personnel. Unauthorized or improper use of this system may result in administrative disciplinary action and civil and criminal penalties. By continuing to use this system you indicate your awareness of and consent to these terms and conditions of use. LOG OFF IMMEDIATELY if you do not agree to the conditions stated in this warning.

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  • ASP.NET Asynchronous Pages and when to use them

    - by rajbk
    There have been several articles posted about using  asynchronous pages in ASP.NET but none of them go into detail as to when you should use them. I finally found a great post by Thomas Marquardt that explains the process in depth. He addresses a key misconception also: So, in your ASP.NET application, when should you perform work asynchronously instead of synchronously? Well, only 1 thread per CPU can execute at a time.  Did you catch that?  A lot of people seem to miss this point...only one thread executes at a time on a CPU. When you have more than this, you pay an expensive penalty--a context switch. However, if a thread is blocked waiting on work...then it makes sense to switch to another thread, one that can execute now.  It also makes sense to switch threads if you want work to be done in parallel as opposed to in series, but up until a certain point it actually makes much more sense to execute work in series, again, because of the expensive context switch. Pop quiz: If you have a thread that is doing a lot of computational work and using the CPU heavily, and this takes a while, should you switch to another thread? No! The current thread is efficiently using the CPU, so switching will only incur the cost of a context switch. Ok, well, what if you have a thread that makes an HTTP or SOAP request to another server and takes a long time, should you switch threads? Yes! You can perform the HTTP or SOAP request asynchronously, so that once the "send" has occurred, you can unwind the current thread and not use any threads until there is an I/O completion for the "receive". Between the "send" and the "receive", the remote server is busy, so locally you don't need to be blocking on a thread, but instead make use of the asynchronous APIs provided in .NET Framework so that you can unwind and be notified upon completion. Again, it only makes sense to switch threads if the benefit from doing so out weights the cost of the switch. Read more about it in these posts: Performing Asynchronous Work, or Tasks, in ASP.NET Applications http://blogs.msdn.com/tmarq/archive/2010/04/14/performing-asynchronous-work-or-tasks-in-asp-net-applications.aspx ASP.NET Thread Usage on IIS 7.0 and 6.0 http://blogs.msdn.com/tmarq/archive/2007/07/21/asp-net-thread-usage-on-iis-7-0-and-6-0.aspx   PS: I generally do not write posts that simply link to other posts but think it is warranted in this case.

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  • A* navigational mesh path finding

    - by theguywholikeslinux
    So I've been making this top down 2D java game in this framework called Greenfoot [1] and I've been working on the AI for the guys you are gonna fight. I want them to be able to move around the world realistically so I soon realized, amongst a couple of other things, I would need some kind of pathfinding. I have made two A* prototypes. One is grid based and then I made one that works with waypoints so now I need to work out a way to get from a 2d "map" of the obstacles/buildings to a graph of nodes that I can make a path from. The actual pathfinding seems fine, just my open and closed lists could use a more efficient data structure, but I'll get to that if and when I need to. I intend to use a navigational mesh for all the reasons out lined in this post on ai-blog.net [2]. However, the problem I have faced is that what A* thinks is the shortest path from the polygon centres/edges is not necessarily the shortest path if you travel through any part of the node. To get a better idea you can see the question I asked on stackoverflow [3]. I got a good answer concerning a visibility graph. I have since purchased the book (Computational Geometry: Algorithms and Applications [4]) and read further into the topic, however I am still in favour of a navigational mesh (See "Managing Complexity" [5] from Amit’s Notes about Path-Finding [6]). (As a side note, maybe I could possibly use Theta* to convert multiple waypoints into one straight line if the first and last are not obscured. Or each time I move back check to the waypoint before last to see if I can go straight from that to this) So basically what I want is a navigational mesh where once I have put it through a funnel algorithm (e.g. this one from Digesting Duck [7]) I will get the true shortest path, rather than get one that is the shortest path following node to node only, but not the actual shortest given that you can go through some polygons and skip nodes/edges. Oh and I also want to know how you suggest storing the information concerning the polygons. For the waypoint prototype example I made I just had each node as an object and stored a list of all the other nodes you could travel to from that node, I'm guessing that won't work with polygons? and how to I tell if a polygon is open/traversable or if it is a solid object? How do I store which nodes make up the polygon? Finally, for the record: I do want to programme this by myself from scratch even though there are already other solutions available and I don't intend to be (re) using this code in anything other than this game so it does not matter that it will inevitably be poor quality. http://greenfoot.org http://www.ai-blog.net/archives/000152.html http://stackoverflow.com/q/7585515/ http://www.cs.uu.nl/geobook/ http://theory.stanford.edu/~amitp/GameProgramming/MapRepresentations.html http://theory.stanford.edu/~amitp/GameProgramming/ http://digestingduck.blogspot.com/2010/03/simple-stupid-funnel-algorithm.html

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  • 3DS Max 2012 OBJ file import missing polygons

    - by Vit
    I started learning OpenGL. I got to a point I want to import some "real" objects. After "Googling" I decided I will go with OBJ file for start, since it is simple to understand, and there are plenty of tutorials on how to read them properly. I have from university access to 3DS Max 2012. So I tried to create very simple model (just deformated cube) and exporting it using OBJ file, just to vertices and triangles for the moment, without textures, so I can examine its structure by myself. But if I imported it right back to 3DS from OBJ file, now it renders somewhat strange, like its smoothen, and with lightsource, even I have none in scene. But the geometry, its wireframe is intact. So I thought maybe it is problem of exporting only vertices and triangles so I downloaded Enterprise-D model from internet, exported with everything on (normals, textures everything), and again imported it. Now, some polygons are missing. So, I want to ask, am I doing something terribly wrong, or is there some incompatibility issue between .max and .obj file ? Even it is only simple textured model without any lightsources, animation etc.? Thanks. Edit: I tried objects with MeshLab, the first, deformated cube was absolutelly OK. But still bothers me that 3DS Max doesen´t render it properly. In Enterprise-D model, there are polygons missing even in MeshLab. I uploaded rar archive with .max model of Enterprise, same .obj model exported from 3DS, and obj model of deformated cube. Download here (2.5 MB, filesonic).

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  • Bone creation in XNA Content Pipeline

    - by cod3monk3y
    I'm trying to manually create a ModelContent instance that includes custom Bone data in a custom ContentProcessor in the XNA Content Pipeline. I can't seem to create or assign manually created bone data due to either private constructors or read-only collections (at every turn). The code I have right now that creates a single triangle ModelContent that I'd like to create a bone for is: MeshContent mc = new MeshContent(); mc.Positions.Add(new Vector3(-10, 0, 0)); mc.Positions.Add(new Vector3(0, 10, 0)); mc.Positions.Add(new Vector3(10, 0, 0)); GeometryContent gc = new GeometryContent(); gc.Indices.AddRange(new int[] { 0, 1, 2 }); gc.Vertices.AddRange(new int[] { 0, 1, 2 }); mc.Geometry.Add(gc); // Create normals MeshHelper.CalculateNormals(mc, true); // finally, convert it to a model ModelContent model = context.Convert<MeshContent, ModelContent>(mc, "ModelProcessor"); The documentation on XNA is amazingly sparse. I've been referencing the class diagrams created by DigitalRune and Sean Hargreaves blog, but I haven't found anything on creating bone content. Once the ModelContent is created, it's not possible to add bones because the Bones collection is read-only. And it seems the only way to create the ModelContent instance is to call the standard ModelProcessor via ContentProcessorContext.Convert. So it's a bit of a catch-22. The BoneContent class has a constructor but no methods except those inherited from NodeContent... though now (true to form) maybe I've realized the solution by asking the question. Should I create a root NodeContent with two children: one MeshContent and one BoneContent as the root of my skeleton; then pass the root NodeContent to ContentProcessorContext.Convert? Off to try that now...

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  • Tunning scrolling in urxvt

    - by Ivan Petrushev
    Hello, I'm using rxvt-unicode version 9.06 at Ubuntu 9.10. I was used to aterm, where you can use SHIFT + up/down arrow to scroll the printed output with a line up or down. You can also use SHIFT + pgup/pgdown to scroll one screen up or down. In urxvt I can use the pgup/pgdown combination as well, but can't use the up/down arrow combination. It is very useful to be able to scroll by single lines. Do you have any idea how to enable the up/down arrow scrolling? This is my ~/.inputrc: set show-all-if-ambiguous on And this is my ~/.Xdefaults: URxvt*geometry:80x35 URxvt*transparent:true URxvt*shading:40 URxvt*saveLines:12000 URxvt*foreground:White URxvt*background:Blue URxvt*font: -*-terminus-*-*-*-*-14-*-*-*-*-*-*-* URxvt*color4:RoyalBlue URxvt*color12:RoyalBlue URxvt*scrollBar:true URxvt*scrollBar_right:false URxvt*scrollstyle:rxvt

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  • Bash script not adding variables to session

    - by travega
    I have a bash script that I have added as a startup application. It does a bunch of exports and alias assignment. #! /bin/bash alias devhm='cd ${DEV_HOME}; ll'; alias wlhm='cd ${WL_HOME}; ll'; alias dirch='watch --interval=1 "ls -la"'; alias vols='watch --interval=1 "df -h"'; alias svn-update='svn update --depth infinity ./*'; alias mci="~/mci.sh"; alias vncserver="vncserver -geometry 1680x1050"; alias ..="cd .."; alias hist="history | grep "; export PROXY_HOST=proxy.my.setup; export PROXY_PORT=3128; export LD_LIBRARY_PATH=$LD_LIBRARY_PATH/usr/lib/oracle/12.1/client64/lib; export ORACLE_HOME=/usr/lib/oracle/12.1/client64; export TNS_ADMIN=${ORACLE_HOME}/network/admin; echo "DONE!"; But none of these values are available in my terminal sessions anymore. Even when I run the script straight into the terminal like so: ./setup.sh I see the "DONE!" prompt printed but no aliases or env variables are set. If I copy and paste the contents of the file into the terminal the aliases and env variables are set. I have tried adding a line to execute the script from .bashrc also but still no aliases or env variables set. Any ideas what might be going on here? Also could anyone suggest a better way to have these env variables/aliases added to every terminal session?

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  • Partitions on Linux and their CHS dependance

    - by FractalizeR
    Hello. Recently I came into a problem with partitioning WD20EARS disk (with 4k sectors). I needed partitions to be aligned correctly so I just used parted in "unit s" mode and started all partitions at mod8 sector (drive itself reports, that sector is 512b) and ended all of them at mod8-1 sector. But then I thought, that may be I should take into account also the cylinder boundaries (I've seen some posts on the net where fdisk complains about partitions not to start/end on cylinder boundary). And then... I thought, that if drive lies about it's sector size, may be it's lying about the whole geometry? Should I care about partitions to be aligned against cylinder boundaries? If so, how do I find these boundaries? I guess each drive model can contain different sectors per track/cylinder... Or sector alignment is all I should take care of?

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  • Computing pixel's screen position in a vertex shader: right or wrong?

    - by cubrman
    I am building a deferred rendering engine and I have a question. The article I took the sample code from suggested computing screen position of the pixel as follows: VertexShaderFunction() { ... output.Position = mul(worldViewProj, input.Position); output.ScreenPosition = output.Position; } PixelShaderFunction() { input.ScreenPosition.xy /= input.ScreenPosition.w; float2 TexCoord = 0.5f * (float2(input.ScreenPosition.x,-input.ScreenPosition.y) + 1); ... } The question is what if I compute the position in the vertex shader (which should optimize the performance as VSF is launched significantly less number of times than PSF) would I get the per-vertex lighting insted. Here is how I want to do this: VertexShaderFunction() { ... output.Position = mul(worldViewProj, input.Position); output.ScreenPosition.xy = output.Position / output.Position.w; } PixelShaderFunction() { float2 TexCoord = 0.5f * (float2(input.ScreenPosition.x,-input.ScreenPosition.y) + 1); ... } What exactly happens with the data I pass from VS to PS? How exactly is it interpolated? Will it give me the right per-pixel result in this case? I tried launching the game both ways and saw no visual difference. Is my assumption right? Thanks. P.S. I am optimizing the point light shader, so I actually pass a sphere geometry into the VS.

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  • Tkinter on Ubuntu 14.04 seems not to work

    - by empedokles
    I receive following Traceback: Traceback (most recent call last): File "tkinter_basic_frame.py", line 4, in <module> from Tkinter import Tk, Frame, BOTH File "/usr/lib/python2.7/lib-tk/Tkinter.py", line 42, in raise ImportError, str(msg) + ', please install the python-tk package' ImportError: No module named _tkinter, please install the python-tk package This is the demoscript I'm trying to run: #!/usr/bin/python # -*- coding: utf-8 -*- from Tkinter import Tk, Frame, BOTH class Example(Frame): def __init__(self, parent): Frame.__init__(self, parent, background="white") self.parent = parent self.initUI() def initUI(self): self.parent.title("Simple") self.pack(fill=BOTH, expand=1) def main(): root = Tk() root.geometry("250x150+300+300") app = Example(root) root.mainloop() if __name__ == '__main__': main() From my knowledge Tkinter should be included in Python 2.7. Why do I receive the traceback? Doesn't ubuntu contain the standard-python-distribution? This is solved. I had to install it manually in synaptic (got the hint in the meantime from another forum), see here: Wikipedia says: "Tkinter is a Python binding to the Tk GUI toolkit. It is the standard Python interface to the Tk GUI toolkit1 and is Python's de facto standard GUI,2 and is included with the standard Windows and Mac OS X install of Python." - Not good, that it isn't included in Ubuntu as well. Tkinter on Wikipedia

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  • Is commented out code really always bad?

    - by nikie
    Practically every text on code quality I've read agrees that commented out code is a bad thing. The usual example is that someone changed a line of code and left the old line there as a comment, apparently to confuse people who read the code later on. Of course, that's a bad thing. But I often find myself leaving commented out code in another situation: I write a computational-geometry or image processing algorithm. To understand this kind of code, and to find potential bugs in it, it's often very helpful to display intermediate results (e.g. draw a set of points to the screen or save a bitmap file). Looking at these values in the debugger usually means looking at a wall of numbers (coordinates, raw pixel values). Not very helpful. Writing a debugger visualizer every time would be overkill. I don't want to leave the visualization code in the final product (it hurts performance, and usually just confuses the end user), but I don't want to loose it, either. In C++, I can use #ifdef to conditionally compile that code, but I don't see much differnce between this: /* // Debug Visualization: draw set of found interest points for (int i=0; i<count; i++) DrawBox(pts[i].X, pts[i].Y, 5,5); */ and this: #ifdef DEBUG_VISUALIZATION_DRAW_INTEREST_POINTS for (int i=0; i<count; i++) DrawBox(pts[i].X, pts[i].Y, 5,5); #endif So, most of the time, I just leave the visualization code commented out, with a comment saying what is being visualized. When I read the code a year later, I'm usually happy I can just uncomment the visualization code and literally "see what's going on". Should I feel bad about that? Why? Is there a superior solution? Update: S. Lott asks in a comment Are you somehow "over-generalizing" all commented code to include debugging as well as senseless, obsolete code? Why are you making that overly-generalized conclusion? I recently read Robert Glass' "Clean Code", which says: Few practices are as odious as commenting-out code. Don't do this!. I've looked at the paragraph in the book again (p. 68), there's no qualification, no distinction made between different reasons for commenting out code. So I wondered if this rule is over-generalizing (or if I misunderstood the book) or if what I do is bad practice, for some reason I didn't know.

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  • Firefox 4 crashing in VNC

    - by MacThePenguin
    On my desktop PC I've been using Kubuntu 10.04 for about a year. Recently I've updated Firefox to version 4 using aptitude and the mozilla-team/firefox-stable repository. Since then, I can't run it when I'm logged in through a VNC session. Firefox crashes immediately: when I try to run it from the console I get this error: ###!!! ABORT: X_ShmPutImage: BadShmSeg (invalid shared segment parameter); 3 requests ago: file /build/buildd/firefox-4.0.1+build1+nobinonly/build-tree/mozilla/toolkit/xre/nsX11ErrorHandler.cpp, line 203 ###!!! ABORT: X_ShmPutImage: BadShmSeg (invalid shared segment parameter); 3 requests ago: file /build/buildd/firefox-4.0.1+build1+nobinonly/build-tree/mozilla/toolkit/xre/nsX11ErrorHandler.cpp, line 203 Firefox works fine when I run it directly from the PC. Firefox 3.x worked fine also from a VNC session. I tried to turn off the hardware acceleration from the Firefox preferences, but that doesn't fix the problem. firefox --sync, firefox -safe-mode and firefox -ProfileManager also crash the same way. Any idea how to troubleshoot this? Thanks. Edit: additional info. I run vnc (RealVNC 4.1.1) from xinetd, this is the config I use: service Xvnc { type = UNLISTED disable = no socket_type = stream protocol = tcp wait = yes user = root server = /usr/bin/Xvnc4 server_args = -inetd :1 -desktop vnc5901 -query localhost -geometry 1160x675 -depth 16 -once -DisconnectClients=0 -NeverShared passwordFile=/path/to/vnc/password -render port = 5901 }

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  • How to fix bad Collada produced by FBX?

    - by David
    I tried to use the FBX SDK (2011.3.1) to load FBX files and save them as Collada files in order to be able to import FBX files in Panda3D. Unfortunately the resulting Collada files are not usable for several reasons, among them: There's a Maya specific extra technique diffuse <diffuse> <texture texture="Map__2-image" texcoord="CHANNEL0"> <extra> <technique profile="MAYA"> <wrapU sid="wrapU0">TRUE</wrapU> <wrapV sid="wrapV0">TRUE</wrapV> <blend_mode>ADD</blend_mode> </technique> </extra> </texture> </diffuse> It assigns a texcoord channel name that isn't referenced anywhere else in the file (in the previous code sample, no geometry uses "CHANNEL0"...) Every polygon is exported twice, a first time with a basic material (only diffuse color, specular color, etc.) and a second time with a textured material -- this doubles the number of polygons of each model without any valuable reason Anyway, the resulting Collada file cannot be opened correctly either with OpenCOLLADA or Panda3D's "dae2egg". Anyone has any experience on how to "fix" it and make it understandable by common and well-reputed Collada importers such as OpenCOLLADA?

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  • OpenGL camera moves faster than player

    - by opiop65
    I have a side scroller game made in OpenGL, and I'm trying to center the player in the viewport when he moves. I know how to do it: cameraX = Width / 2 / TileSize - playerPosX cameraY = Height / 2 / TileSize - playerPosY However, I have a problem. The player and "camera" move, but the player moves faster than the "camera" scrolls. So, the player can actually move out of the screen. Some code, this is how I translate the camera: public Camera(){ } public void update(Player p){ glTranslatef(-p.getPos().x - Main.WIDTH / 64 / 2, -p.getPos().y - Main.HEIGHT / 64 / 2, 1); } Here's how I move the player: public void update(){ if(Keyboard.isKeyDown(Keyboard.KEY_D)){ this.move(MOVESPEED, 0); } if(Keyboard.isKeyDown(Keyboard.KEY_A)){ this.move(-MOVESPEED, 0); } } The move method: public void move(float x, float y){ this.getPos().set(this.getPos().x + x, this.getPos().y + y); } And then after I move the player, I update the player's geometry, which shouldn't matter. What am I doing wrong here, this seems like such a simple problem, yet it doesn't work!

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  • State of the art Culling and Batching techniques in rendering

    - by Kristian Skarseth
    I'm currently working with upgrading and restructuring an OpenGL render engine. The engine is used for visualising large scenes of architectural data (buildings with interior), and the amount of objects can become rather large. As is the case with any building, there is a lot of occluded objects within walls, and you naturally only see the objects that are in the same room as you, or the exterior if you are on the outside. This leaves a large number of objects that should be occluded through occlusion culling and frustum culling. At the same time there is a lot of repetative geometry that can be batched in renderbatches, and also a lot of objects that can be rendered with instanced rendering. The way I see it, it can be difficult to combine renderbatching and culling in an optimal fashion. If you batch too many objects in the same VBO it's difficult to cull the objects on the CPU in order to skip rendering that batch. At the same time if you skip the culling on the cpu, a lot of objects will be processed by the GPU while they are not visible. If you skip batching copletely in order to more easily cull on the CPU, there will be an unwanted high amount of render calls. I have done some research into existing techniques and theories as to how these problems are solved in modern graphics, but I have not been able to find any concrete solution. An idea a colleague and me came up with was restricting batches to objects relatively close to eachother e.g all chairs in a room or within a radius of n meeters. This could be simplified and optimized through use of oct-trees. Does anyone have any pointers to techniques used for scene managment, culling, batching etc in state of the art modern graphics engines?

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  • Suitability of ground fog using layered alpha quads?

    - by Nick Wiggill
    A layered approach would use a series of massive alpha-textured quads arranged parallel to the ground, intersecting all intervening terrain geometry, to provide the illusion of ground fog quite effectively from high up, looking down, and somewhat less effectively when inside the fog and looking toward the horizon (see image below). Alternatively, a shader-heavy approach would instead calculate density as function of view distance into the ground fog substrate, and output the fragment value based on that. Without having to performance-test each approach myself, I would like first to hear others' experiences (not speculation!) on what sort of performance impact the layered alpha texture approach is likely to have. I ask specifically due to the oft-cited impacts of overdraw (not sure how fill-rate bound your average desktop system is). A list of games using this approach, particularly older games, would be immensely useful: if this was viable on pre DX9/OpenGL2 hardware, it is likely to work fine for me. One big question is in regards to this sort of effect: (Image credit goes to Lume of lume.com) Notice how the vertical fog gradation is continuous / smooth. OTOH, using textured quad layers, I can only assume that layers would be mighty obvious when walking through them -- the more sparse they were, the more obvious this would be. This is in contrast to where fog planes are aligned to face the player every frame, where this coarseness would be much less obvious.

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  • AutoVue 20.2 for Agile Released

    - by Kerrie Foy
    I saw an important post on the Oracle's AutoVue Enterprise Visualization Blog that I wanted to share with you all in the Agile community.  This was originally posted by Angus Graham here. AutoVue 20.2 for Agile Released Oracle’s AutoVue 20.2 for Agile PLM is now available on Oracle’s Software Delivery Cloud. This latest release allows Agile PLM customers to take advantage of new AutoVue 20.2 features in the following Agile PLM environments: 9.3.1.x; 9.3.0.  AutoVue 20.2 delivers improvements in the following areas. New Format Support: AutoVue 20.2 adds support for the latest versions of popular file formats including: ECAD: Cadence Concept HDL 16.5, Allegro Layout 16.5, Orcad Capture 16.5, Board Station ASCII Symbol Geometry, Cadence Cell Library MCAD: CATIA V5 R21, PTC Creo Parametric 1.0, Creo Element\Direct Modeling 17.10, 17.20, 17.25, 17.30, 18.00, SolidWorks 2012, SolidEdge ST3 & ST4, PLM XML 2D CAD: Creo Element/Direct Drafting 17.10 to 18.00 Office: MS Office 2010: Word, Excel, PowerPoint, Outlook Enhancements to AutoVue enterprise readiness: reliability and performance improvements, as well as security enhancements which adhere to Oracle’s Software Security Assurance standards Updated version of AutoVue Document Print Service offerings, which include the ability to select CAD layers for printing  For further details, check out the What’s New in AutoVue 20.2 datasheet

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