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  • How to find siblings of a tree?

    - by smallB
    On my interview for an internship, I was asked following question: On a whiteboard write the simplest algorithm with use of recursion which would take a root of a so called binary tree (so called because it is not strictly speaking binary tree) and make every child in this tree connected with its sibling. So if I have: 1 / \ 2 3 / \ \ 4 5 6 / \ 7 8 then the sibling to 2 would be 3, to four five, to five six and to seven eight. I didn't do this, although I was heading in the right direction. Later (next day) at home I did it, but with the use of a debugger. It took me better part of two hours and 50 lines of code. I personally think that this was very difficult question, almost impossible to do correctly on a whiteboard. How would you solve it on a whiteboard? How to apprehend this question without using a debugger?

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  • How can Java be improved so that it no longer needs to perform type erasure? [closed]

    - by user63904
    The official Java tutorial on generics explains type erasure and why it was added to the compiler: When a generic type is instantiated, the compiler translates those types by a technique called type erasure — a process where the compiler removes all information related to type parameters and type arguments within a class or method. Type erasure enables Java applications that use generics to maintain binary compatibility with Java libraries and applications that were created before generics. This most likely was a pragmatic approach, or perhaps the least painful one. However, now that generics is widely supported across the industry, what can be done in order for us to not need type erasure? Is it feasible with out needing to break backwards compatibility, or if it is feasible, is it practical? Has the last the last statement in the quote above become self referential? That is: "type erasure enables Java applications that use generics to maintain binary compatibility with Java libraries and applications that were created with Java versions that perform type erasure."

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  • when i marked all check boxes in settings,update fails.

    - by user67966
    "W:Failed to fetch cdrom://Ubuntu 12.04 LTS Precise Pangolin - Release i386 (20120423)/dists/precise/main/binary-i386/Packages Please use apt-cdrom to make this CD-ROM recognized by APT. apt-get update cannot be used to add new CD-ROMs , W:Failed to fetch cdrom://Ubuntu 12.04 LTS Precise Pangolin - Release i386 (20120423)/dists/precise/restricted/binary-i386/Packages Please use apt-cdrom to make this CD-ROM recognized by APT. apt-get update cannot be used to add new CD-ROMs , E:Some index files failed to download. They have been ignored, or old ones used instead." the above information is a crash info.It happens when i manually update ubuntu.I have marked all check-boxes in settings which was by default not marked. What is the main reason for this problem?

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  • Gradient algororithm produces little white dots

    - by user146780
    I'm working on an algorithm to generate point to point linear gradients. I have a rough, proof of concept implementation done: GLuint OGLENGINEFUNCTIONS::CreateGradient( std::vector<ARGBCOLORF> &input,POINTFLOAT start, POINTFLOAT end, int width, int height,bool radial ) { std::vector<POINT> pol; std::vector<GLubyte> pdata(width * height * 4); std::vector<POINTFLOAT> linearpts; std::vector<float> lookup; float distance = GetDistance(start,end); RoundNumber(distance); POINTFLOAT temp; float incr = 1 / (distance + 1); for(int l = 0; l < 100; l ++) { POINTFLOAT outA; POINTFLOAT OutB; float dirlen; float perplen; POINTFLOAT dir; POINTFLOAT ndir; POINTFLOAT perp; POINTFLOAT nperp; POINTFLOAT perpoffset; POINTFLOAT diroffset; dir.x = end.x - start.x; dir.y = end.y - start.y; dirlen = sqrt((dir.x * dir.x) + (dir.y * dir.y)); ndir.x = static_cast<float>(dir.x * 1.0 / dirlen); ndir.y = static_cast<float>(dir.y * 1.0 / dirlen); perp.x = dir.y; perp.y = -dir.x; perplen = sqrt((perp.x * perp.x) + (perp.y * perp.y)); nperp.x = static_cast<float>(perp.x * 1.0 / perplen); nperp.y = static_cast<float>(perp.y * 1.0 / perplen); perpoffset.x = static_cast<float>(nperp.x * l * 0.5); perpoffset.y = static_cast<float>(nperp.y * l * 0.5); diroffset.x = static_cast<float>(ndir.x * 0 * 0.5); diroffset.y = static_cast<float>(ndir.y * 0 * 0.5); outA.x = end.x + perpoffset.x + diroffset.x; outA.y = end.y + perpoffset.y + diroffset.y; OutB.x = start.x + perpoffset.x - diroffset.x; OutB.y = start.y + perpoffset.y - diroffset.y; for (float i = 0; i < 1; i += incr) { temp = GetLinearBezier(i,outA,OutB); RoundNumber(temp.x); RoundNumber(temp.y); linearpts.push_back(temp); lookup.push_back(i); } for (unsigned int j = 0; j < linearpts.size(); j++) { if(linearpts[j].x < width && linearpts[j].x >= 0 && linearpts[j].y < height && linearpts[j].y >=0) { pdata[linearpts[j].x * 4 * width + linearpts[j].y * 4 + 0] = (GLubyte) j; pdata[linearpts[j].x * 4 * width + linearpts[j].y * 4 + 1] = (GLubyte) j; pdata[linearpts[j].x * 4 * width + linearpts[j].y * 4 + 2] = (GLubyte) j; pdata[linearpts[j].x * 4 * width + linearpts[j].y * 4 + 3] = (GLubyte) 255; } } lookup.clear(); linearpts.clear(); } return CreateTexture(pdata,width,height); } It works as I would expect most of the time, but at certain angles it produces little white dots. I can't figure out what does this. This is what it looks like at most angles (good) http://img9.imageshack.us/img9/5922/goodgradient.png But once in a while it looks like this (bad): http://img155.imageshack.us/img155/760/badgradient.png What could be causing the white dots? Is there maybe also a better way to generate my gradients if no solution is possible for this? Thanks

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  • How to cross-compile programs for the Raspberry Pi with gcc?

    - by InkBlend
    I am fond of using gcc to compile small little C and C++ programs on my main computer. However, I also have a Raspberry Pi, and, being a 700-MHz single-core computer, I would prefer to not have to do my development work on it every time I want to create a binary for it. How (for I know that there's a way) do I cross-compile my program for the Raspberry Pi using my x86 laptop? And is there a way that I may compile C(++) programs on the Pi but produce an x86 binary? If it's any help, "The SoC is a Broadcom BCM2835. This contains an ARM1176JZFS, with floating point..." (according to the official Raspberry Pi FAQ).

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  • Do Nvidia's drivers work in 12.10?

    - by Pratyush Nalam
    I recently upgraded to 12.10 and was just checking for proprietary drivers to be installed. I found this in software sources When I enabled Nvidia binary Xorg driver, unity disappears along with the launcher and everything. I just have the wallpaper. I did manage to open the terminal and open software sources and select the nouveau display driver which fixed it. Question is how to enable NVIDIA binary Xorg driver and have everything working? Hardware: Apple MacBook Pro 9,1 Mid 2012 15 inch non-retina. NVIDIA GeForce GT650M EDIT: I tried the solution here. And now, when I boot into Ubuntu, I get a blinking cursor. That's all! No tty1, nothing. help !!

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  • Is a yobibit really a meaningful unit? [closed]

    - by Joe
    Wikipedia helpfully explains: The yobibit is a multiple of the bit, a unit of digital information storage, prefixed by the standards-based multiplier yobi (symbol Yi), a binary prefix meaning 2^80. The unit symbol of the yobibit is Yibit or Yib.1[2] 1 yobibit = 2^80 bits = 1208925819614629174706176 bits = 1024 zebibits[3] The zebi and yobi prefixes were originally not part of the system of binary prefixes, but were added by the International Electrotechnical Commission in August 2005.[4] Now, what in the world actually takes up 1,208,925,819,614,629,174,706,176 bits? The information content of the known universe? I guess this is forward thinking -- maybe astrophyics or nanotech, or even DNA analysis really will require these orders of magnitude. How far off do you think all this is? Are these really meaningful units?

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  • Failed to download repository information

    - by Bob Van Elst
    When i clicked check this error message came up. But it does not come up when update manager strarts automatically. When you open update manager this error comes up. Any ideas on how to fix it? Details: *W:GPG error: (http://ppa.launchpad.net precise Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY FC8CA6FE7B1FEC7C, W:Failed to fetch (http://ppa.launchpad.net/jonabeck/ppa/ubuntu/dists/precise/main/binary-amd64/Packages 404 Not Found , W:Failed to fetch (http://ppa.launchpad.net/jonabeck/ppa/ubuntu/dists/precise/main/binary-i386/Packages 404 Not Found , W:Failed to fetch (http://ppa.launchpad.net/jonabeck/ppa/ubuntu/dists/precide/main/source/Sources 404 Not Found , E:Some index files failed to download. They have been ignored, or old ones used instead.*

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  • 11.10 - Update Manager Not working

    - by Mattlinux1
    W:Failed to fetch cdrom://Ubuntu 11.10 Oneiric Ocelot - Release i386 (20111012)/dists/oneiric/main/binary-i386/Packages Please use apt-cdrom to make this CD-ROM recognized by APT. apt-get update cannot be used to add new CD-ROMs , W:Failed to fetch cdrom://Ubuntu 11.10 Oneiric Ocelot - Release i386 (20111012)/dists/oneiric/restricted/binary-i386/Packages Please use apt-cdrom to make this CD-ROM recognized by APT. apt-get update cannot be used to add new CD-ROMs , E:Some index files failed to download. They have been ignored, or old ones used instead. This happens when i hit the check button? and the updates were working before.

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  • Will there ever be a version of Java which does not perform Type Erasure

    - by user63904
    Type erasure enables Java applications that use generics to maintain binary compatibility with Java libraries and applications that were created before generics Generics were introduced in Java 1.5, so presumably the statement "applications that were created before generics" is referring to Java 1.4? Given that Java 1.4 entered its End Of Life around 2006 and was officially End Of Life'd around 2008. Why is type erasure still being performed in Java 7, etc... Has the statement now become self referential i.e. Type erasure enables Java applications that use generics to maintain binary compatibility with Java libraries and applications that were created with Java versions that perform Type Erasure. Meaning therefore that there will never be a version of Java that doesn't perform Type Erasure.

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  • Getting a 404 when using the Nexus 7 installer PPA, how do I fix this? [duplicate]

    - by Vitaliy
    This question already has an answer here: How can I fix a 404 Error when using a PPA? 2 answers ubuntu 13.10 sudo add-apt-repository ppa:ubuntu-nexus7/ubuntu-nexus7-installer OK sudo apt-get update: W: ?? ??????? ???????? http://ppa.launchpad.net/ubuntu-nexus7/ubuntu-nexus7-installer/ubuntu/dists/saucy/main/binary-amd64/Packages 404 Not Found W: ?? ??????? ???????? http://ppa.launchpad.net/ubuntu-nexus7/ubuntu-nexus7-installer/ubuntu/dists/saucy/main/binary-i386/Packages 404 Not Found Thanks for the answer

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  • Update information outdated, "Failed to fetch cdrom"

    - by user285603
    I have a warning triangle on the top of my screen. When I click on it, it says that my update information is outdated. When I type sudo apt-get update && sudo apt-get upgrade into a terminal, I get this message: W: Failed to fetch cdrom://Ubuntu 14.04 LTS _Trusty Tahr_ - Release i386 (20140417)/dists/trusty/main/binary-i386/Packages Please use apt-cdrom to make this CD-ROM recognized by APT. apt-get update cannot be used to add new CD-ROMs W: Failed to fetch cdrom://Ubuntu 14.04 LTS _Trusty Tahr_ - Release i386 (20140417)/dists/trusty/restricted/binary-i386/Packages Please use apt-cdrom to make this CD-ROM recognized by APT. apt-get update cannot be used to add new CD-ROMs E: Some index files failed to download. They have been ignored, or old ones used instead. Any ideas?

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  • Ubuntu 14.04 compiz thumbnails preview flicker

    - by HockeyBum
    Ubuntu 14.04.1 x64 (upgraded from 12.04) with Unity desktop Dell Latitude with NVIDIA GF119M (NVS 4200M) - Optimus is DISABLED Using NVIDIA legacy binary driver 304.117 When I set the CCSM option to allow thumbnail previews, the thumbnail 'flickers' for about 1 second before the actual thumbnail image is displayed. I don't think I had this enabled under 12.04 so not sure if it's version-specific. Should I be using a different driver (there are newer ones - Ubu shows NVIDIA binary driver 331.38 and the non-proprietary nouveau, plus NVIDIA has newer ones at the site)? TIA!

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  • Why Skype doesn't work in Quantal

    - by Lionthinker
    Since updating to Quantal Skype doesn't work and I get this error when updating: W:GPG error: http://ppa.launchpad.net quantal Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY F6A071ABEE5D5BA2 W:Failed to fetch http://archive.canonical.com/commercial-ppa-uploaders/skype/ubuntu/dists/quantal/main/source/Sources 404 Not Found [IP: 91.189.92.191 80] W:Failed to fetch http://archive.canonical.com/commercial-ppa-uploaders/skype/ubuntu/dists/quantal/main/binary-amd64/Packages 404 Not Found [IP: 91.189.92.191 80] W:Failed to fetch http://archive.canonical.com/commercial-ppa-uploaders/skype/ubuntu/dists/quantal/main/binary-i386/Packages 404 Not Found [IP: 91.189.92.191 80] E:Some index files failed to download. They have been ignored, or old ones used instead.

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  • Changing Wallpaper on 12.04 Login Screen

    - by userIsAMonkey
    I'm using this link but seems to be not working on 12.04, here's the Terminal message below: Are there other softwares/tips for changing the login screen? I'm also using link but seems outdated. Failed to fetch http://ppa.launchpad.net/claudiocn/slm/ubuntu/dists/precise/main/source/Sources 404 Not Found W: Failed to fetch http://ppa.launchpad.net/claudiocn/slm/ubuntu/dists/precise/main/binary-amd64/Packages 404 Not Found W: Failed to fetch http://ppa.launchpad.net/claudiocn/slm/ubuntu/dists/precise/main/binary-i386/Packages 404 Not Found E: Some index files failed to download. They have been ignored, or old ones used instead. law@ubuntu:~$ sudo apt-get install simple-lightdm-manager Reading package lists... Done Building dependency tree Reading state information... Done E: Unable to locate package simple-lightdm-manager

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  • BigInteger Library

    A .NET 2.0 library for the 64 bit optimized handling of very large integers, up to 10240 binary digits or approximately (safe to use) 3000 decimal digits

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  • When must arbitrary precision arithmetic functions be used in PHP?

    - by Tjorriemorrie
    My colleague uses the Binary Calculator functions in bandwidth calculations; as much as terrabytes, and with percentage splitting on allocation. His usage of these functions appears correct in order not to lose a byte; although he seems to be using them now for everything. The manual only says: For arbitrary precision mathematics PHP offers the Binary Calculator which supports numbers of any size and precision, represented as strings. How much is any size? Is it really necessary? How big is the default float in PHP? Are there any good advice regarding this or things to keep in mind?

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  • NVIDIA GFORCE 610M drivers

    - by thefinn93
    I'm attempting to install drivers for my GFORCE 610M and none of the solutions seems to work. Generally people recommend using the jockey-gtk program, which doesn't detect the card and states that there's no propitiatory drivers to install. I tried download the official binary from the NVIDIA site, but that told me that I had to remove the Nouveau kernal driver, so I did that, following the instructions on the wiki (apt-get remove --purge xorg-something or other) and ignoring the "DON'T DO THIS" warning, after that didn't do anything i installed various packages (nvidia-common, nvidia-settings, etc) and eventually got the nvidia-settings program (and a very low screen resolution). Unfortunately when I open nvidia-settings it tells me to run nvidia-xconfig as root (i've done this several times, but to no avail) and doesn't let me configure anything. At this point I tried re-running the binary installer i downloaded from nvidia's site, and it said it worked but it didn't change a thing. So I'm out of ideas, what've you got?

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  • What is a byte stream actually?

    - by user2720323
    Can anyone explain me what byte stream actually contains? Does it contain bytes (hex data) or binary data or english letters only? I am also confused about the term Raw Data. If someone asked me to "reverse the 4 byte data", then what should I assume the data is hex code or binary code? Can anyone please clarify this for me. I have read so many articles and in java and c. They used to talk these words frequently but never understood them clearly.

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  • Inspire Geek Love with These Hilarious Geek Valentines

    - by Eric Z Goodnight
    Want to send some Geek Love to that special someone? Why not do it with these elementary school throwback valentines, and win their heart this upcoming Valentine’s day—the geek way! Read on to see the simple method to make your own custom Valentines, as well as download a set of eleven ready-made ones any geek guy or gal should be delighted get. It’s amore! How to Make Custom Valentines A size we’ve used for all of our Valentines is a 3” x 4” at 150 dpi. This is fairly low resolution for print, but makes a great graphic to email. With your new image open, Navigate to Edit > Fill and fill your background layer with a rich, red color (or whatever appeals to you.) By setting “Use” to “Foreground color as shown above, you’ll paint whatever foreground color you have in your color picker. Press to select the text tool. Set a few text objects, using whatever fonts appeal to you. Pixel fonts, like this one, are freely downloadable, and we’ve already shared a great list of Valentines fonts. Copy an image from the internet if you’re confident your sweetie won’t mind a bit of fair use of copyrighted imagery. If they do mind, find yourself some great Creative Commons images. to do a free transform on your image, sizing it to whatever dimensions work best for your design. Right click your newly added image layer in your panel and Choose “Blending Effects” to pick a Layer Style. “Stroke” with this setting adds a black line around your image. Also turning on “Outer Glow” with this setting puts a dark black shadow around the top and bottom (and sides, although they are hidden). Add some more text. Double entendre is recommended. Click and hold down on the “Rectangle Tool” to get the “Custom Shape Tool.” The custom shape tool has useful vector shapes built into it. Find the “Shape” dropdown in the menu to find the heart image. Click and drag to create a vector heart shape in your image. Your layers panel is where you can change the color, if it happens to use the wrong one at first. Click the color swatch in your panel, highlighted in blue above. will transform your vector heart. You can also use it to rotate, if you like. Add some details, like this Power or Standby symbol, which can be found in symbol fonts, taken from images online, or drawn by hand. Your Valentine is now ready to be saved as a JPG or PNG and sent to the object of your affection! Keep reading to see a list of 11 downloadable How-To Geek Valentines, including this one and the three from the header image. Download The HTG Set of Valentines Download the HTG Geek Valentines (ZIP) Download the HTG Geek Valentines (ZIP) When he’s not wooing ladies with Valentines cards, you can email the author at [email protected] with your Photoshop and Graphics questions. Your questions may be featured in a future How-To Geek article! Latest Features How-To Geek ETC Inspire Geek Love with These Hilarious Geek Valentines How to Integrate Dropbox with Pages, Keynote, and Numbers on iPad RGB? CMYK? Alpha? What Are Image Channels and What Do They Mean? How to Recover that Photo, Picture or File You Deleted Accidentally How To Colorize Black and White Vintage Photographs in Photoshop How To Get SSH Command-Line Access to Windows 7 Using Cygwin How to Kid Proof Your Computer’s Power and Reset Buttons Microsoft’s Windows Media Player Extension Adds H.264 Support Back to Google Chrome Android Notifier Pushes Android Notices to Your Desktop Dead Space 2 Theme for Chrome and Iron Carl Sagan and Halo Reach Mashup – We Humans are Capable of Greatness [Video] Battle the Necromorphs Once Again on Your Desktop with the Dead Space 2 Theme for Windows 7

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  • Skewed: a rotating camera in a simple CPU-based voxel raycaster/raytracer

    - by voxelizr
    TL;DR -- in my first simple software voxel raycaster, I cannot get camera rotations to work, seemingly correct matrices notwithstanding. The result is skewed: like a flat rendering, correctly rotated, however distorted and without depth. (While axis-aligned ie. unrotated, depth and parallax are as expected.) I'm trying to write a simple voxel raycaster as a learning exercise. This is purely CPU based for now until I figure out how things work exactly -- fow now, OpenGL is just (ab)used to blit the generated bitmap to the screen as often as possible. Now I have gotten to the point where a perspective-projection camera can move through the world and I can render (mostly, minus some artifacts that need investigation) perspective-correct 3-dimensional views of the "world", which is basically empty but contains a voxel cube of the Stanford Bunny. So I have a camera that I can move up and down, strafe left and right and "walk forward/backward" -- all axis-aligned so far, no camera rotations. Herein lies my problem. Screenshot #1: correct depth when the camera is still strictly axis-aligned, ie. un-rotated. Now I have for a few days been trying to get rotation to work. The basic logic and theory behind matrices and 3D rotations, in theory, is very clear to me. Yet I have only ever achieved a "2.5 rendering" when the camera rotates... fish-eyey, bit like in Google Streetview: even though I have a volumetric world representation, it seems --no matter what I try-- like I would first create a rendering from the "front view", then rotate that flat rendering according to camera rotation. Needless to say, I'm by now aware that rotating rays is not particularly necessary and error-prone. Still, in my most recent setup, with the most simplified raycast ray-position-and-direction algorithm possible, my rotation still produces the same fish-eyey flat-render-rotated style looks: Screenshot #2: camera "rotated to the right by 39 degrees" -- note how the blue-shaded left-hand side of the cube from screen #2 is not visible in this rotation, yet by now "it really should"! Now of course I'm aware of this: in a simple axis-aligned-no-rotation-setup like I had in the beginning, the ray simply traverses in small steps the positive z-direction, diverging to the left or right and top or bottom only depending on pixel position and projection matrix. As I "rotate the camera to the right or left" -- ie I rotate it around the Y-axis -- those very steps should be simply transformed by the proper rotation matrix, right? So for forward-traversal the Z-step gets a bit smaller the more the cam rotates, offset by an "increase" in the X-step. Yet for the pixel-position-based horizontal+vertical-divergence, increasing fractions of the x-step need to be "added" to the z-step. Somehow, none of my many matrices that I experimented with, nor my experiments with matrix-less hardcoded verbose sin/cos calculations really get this part right. Here's my basic per-ray pre-traversal algorithm -- syntax in Go, but take it as pseudocode: fx and fy: pixel positions x and y rayPos: vec3 for the ray starting position in world-space (calculated as below) rayDir: vec3 for the xyz-steps to be added to rayPos in each step during ray traversal rayStep: a temporary vec3 camPos: vec3 for the camera position in world space camRad: vec3 for camera rotation in radians pmat: typical perspective projection matrix The algorithm / pseudocode: // 1: rayPos is for now "this pixel, as a vector on the view plane in 3d, at The Origin" rayPos.X, rayPos.Y, rayPos.Z = ((fx / width) - 0.5), ((fy / height) - 0.5), 0 // 2: rotate around Y axis depending on cam rotation. No prob since view plane still at Origin 0,0,0 rayPos.MultMat(num.NewDmat4RotationY(camRad.Y)) // 3: a temp vec3. planeDist is -0.15 or some such -- fov-based dist of view plane from eye and also the non-normalized, "in axis-aligned world" traversal step size "forward into the screen" rayStep.X, rayStep.Y, rayStep.Z = 0, 0, planeDist // 4: rotate this too -- 0,zstep should become some meaningful xzstep,xzstep rayStep.MultMat(num.NewDmat4RotationY(CamRad.Y)) // set up direction vector from still-origin-based-ray-position-off-rotated-view-plane plus rotated-zstep-vector rayDir.X, rayDir.Y, rayDir.Z = -rayPos.X - me.rayStep.X, -rayPos.Y, rayPos.Z + rayStep.Z // perspective projection rayDir.Normalize() rayDir.MultMat(pmat) // before traversal, the ray starting position has to be transformed from origin-relative to campos-relative rayPos.Add(camPos) I'm skipping the traversal and sampling parts -- as per screens #1 through #3, those are "basically mostly correct" (though not pretty) -- when axis-aligned / unrotated.

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  • How do I get FEATURE_LEVEL_9_3 to work with shaders in Direct3D11?

    - by Dominic
    Currently I'm going through some tutorials and learning DX11 on a DX10 machine (though I just ordered a new DX11 compatible computer) by means of setting the D3D_FEATURE_LEVEL_ setting to 10_0 and switching the vertex and pixel shader versions in D3DX11CompileFromFile to "vs_4_0" and "ps_4_0" respectively. This works fine as I'm not using any DX11-only features yet. I'd like to make it compatible with DX9.0c, which naively I thought I could do by changing the feature level setting to 9_3 or something and taking the vertex/pixel shader versions down to 3 or 2. However, no matter what I change the vertex/pixel shader versions to, it always fails when I try to call D3DX11CompileFromFile to compile the vertex/pixel shader files when I have D3D_FEATURE_LEVEL_9_3 enabled. Maybe this is due to the the vertex/pixel shader files themselves being incompatible for the lower vertex/pixel shader versions, but I'm not expert enough to say. My shader files are listed below: Vertex shader: cbuffer MatrixBuffer { matrix worldMatrix; matrix viewMatrix; matrix projectionMatrix; }; struct VertexInputType { float4 position : POSITION; float2 tex : TEXCOORD0; float3 normal : NORMAL; }; struct PixelInputType { float4 position : SV_POSITION; float2 tex : TEXCOORD0; float3 normal : NORMAL; }; PixelInputType LightVertexShader(VertexInputType input) { PixelInputType output; // Change the position vector to be 4 units for proper matrix calculations. input.position.w = 1.0f; // Calculate the position of the vertex against the world, view, and projection matrices. output.position = mul(input.position, worldMatrix); output.position = mul(output.position, viewMatrix); output.position = mul(output.position, projectionMatrix); // Store the texture coordinates for the pixel shader. output.tex = input.tex; // Calculate the normal vector against the world matrix only. output.normal = mul(input.normal, (float3x3)worldMatrix); // Normalize the normal vector. output.normal = normalize(output.normal); return output; } Pixel Shader: Texture2D shaderTexture; SamplerState SampleType; cbuffer LightBuffer { float4 ambientColor; float4 diffuseColor; float3 lightDirection; float padding; }; struct PixelInputType { float4 position : SV_POSITION; float2 tex : TEXCOORD0; float3 normal : NORMAL; }; float4 LightPixelShader(PixelInputType input) : SV_TARGET { float4 textureColor; float3 lightDir; float lightIntensity; float4 color; // Sample the pixel color from the texture using the sampler at this texture coordinate location. textureColor = shaderTexture.Sample(SampleType, input.tex); // Set the default output color to the ambient light value for all pixels. color = ambientColor; // Invert the light direction for calculations. lightDir = -lightDirection; // Calculate the amount of light on this pixel. lightIntensity = saturate(dot(input.normal, lightDir)); if(lightIntensity > 0.0f) { // Determine the final diffuse color based on the diffuse color and the amount of light intensity. color += (diffuseColor * lightIntensity); } // Saturate the final light color. color = saturate(color); // Multiply the texture pixel and the final diffuse color to get the final pixel color result. color = color * textureColor; return color; }

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  • Computing a normal matrix in conjunction with gluLookAt

    - by Chris Smith
    I have a hand-rolled camera class that converts yaw, pitch, and roll angles into a forward, side, and up vector suitable for calling gluLookAt. Using this camera class I can modify the model-view matrix to move about the 3D world just fine. However, I am having trouble when using this camera class (and associated model-view matrix) when trying to perform directional lighting in my vertex shader. The problem is that the light direction, (0, 1, 0) for example, is relative to where the 'camera is looking' and not the actual world coordinates. (Or is this eye coordinates vs. model coordinates?) I would like the light direction to be unaffected by the camera's viewing direction. For example, when the camera is looking down the Z axis the ground is lit correctly. However, if I point the camera straight at the ground, then it goes dark. This is (I think) because the light direction is parallel with the camera's 'up' vector which is perpendicular with the ground's normal vector. I tried computing the normal matrix without taking the camera's model view into account, but then none of my objects were rotated correctly. Sorry if this sounds vague. I suspect there is a straight forward answer, but I'm not 100% clear on how the normal matrix should be used for transforming vertex normals in my vertex shader. For reference, here is pseudo code for my rendering loop: pMatrix = new Matrix(); pMatrix = makePerspective(...) mvMatrix = new Matrix() camera.apply(mvMatrix); // Calls gluLookAt // Move the object into position. mvMatrix.translatev(position); mvMatrix.rotatef(rotation.x, 1, 0, 0); mvMatrix.rotatef(rotation.y, 0, 1, 0); mvMatrix.rotatef(rotation.z, 0, 0, 1); var nMatrix = new Matrix(); nMatrix.set(mvMatrix.get().getInverse().getTranspose()); // Set vertex shader uniforms. gl.uniformMatrix4fv(shaderProgram.pMatrixUniform, false, new Float32Array(pMatrix.getFlattened())); gl.uniformMatrix4fv(shaderProgram.mvMatrixUniform, false, new Float32Array(mvMatrix.getFlattened())); gl.uniformMatrix4fv(shaderProgram.nMatrixUniform, false, new Float32Array(nMatrix.getFlattened())); // ... gl.drawElements(gl.TRIANGLES, this.vertexIndexBuffer.numItems, gl.UNSIGNED_SHORT, 0); And the corresponding vertex shader: // Attributes attribute vec3 aVertexPosition; attribute vec4 aVertexColor; attribute vec3 aVertexNormal; // Uniforms uniform mat4 uMVMatrix; uniform mat4 uNMatrix; uniform mat4 uPMatrix; // Varyings varying vec4 vColor; // Constants const vec3 LIGHT_DIRECTION = vec3(0, 1, 0); // Opposite direction of photons. const vec4 AMBIENT_COLOR = vec4 (0.2, 0.2, 0.2, 1.0); float ComputeLighting() { vec4 transformedNormal = vec4(aVertexNormal.xyz, 1.0); transformedNormal = uNMatrix * transformedNormal; float base = dot(normalize(transformedNormal.xyz), normalize(LIGHT_DIRECTION)); return max(base, 0.0); } void main(void) { gl_Position = uPMatrix * uMVMatrix * vec4(aVertexPosition, 1.0); float lightWeight = ComputeLighting(); vColor = vec4(aVertexColor.xyz * lightWeight, 1.0) + AMBIENT_COLOR; } Note that I am using WebGL, so if the anser is use glFixThisProblem(...) any pointers on how to re-implement that on WebGL if missing would be appreciated.

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  • Improving the running time of Breadth First Search and Adjacency List creation

    - by user45957
    We are given an array of integers where all elements are between 0-9. have to start from the 1st position and reach end in minimum no of moves such that we can from an index i move 1 position back and forward i.e i-1 and i+1 and jump to any index having the same value as index i. Time Limit : 1 second Max input size : 100000 I have tried to solve this problem use a single source shortest path approach using Breadth First Search and though BFS itself is O(V+E) and runs in time the adjacency list creation takes O(n2) time and therefore overall complexity becomes O(n2). is there any way i can decrease the time complexity of adjacency list creation? or is there a better and more efficient way of solving the problem? int main(){ vector<int> v; string str; vector<int> sets[10]; cin>>str; int in; for(int i=0;i<str.length();i++){ in=str[i]-'0'; v.push_back(in); sets[in].push_back(i); } int n=v.size(); if(n==1){ cout<<"0\n"; return 0; } if(v[0]==v[n-1]){ cout<<"1\n"; return 0; } vector<int> adj[100001]; for(int i=0;i<10;i++){ for(int j=0;j<sets[i].size();j++){ if(sets[i][j]>0) adj[sets[i][j]].push_back(sets[i][j]-1); if(sets[i][j]<n-1) adj[sets[i][j]].push_back(sets[i][j]+1); for(int k=j+1;k<sets[i].size();k++){ if(abs(sets[i][j]-sets[i][k])!=1){ adj[sets[i][j]].push_back(sets[i][k]); adj[sets[i][k]].push_back(sets[i][j]); } } } } queue<int> q; q.push(0); int dist[100001]; bool visited[100001]={false}; dist[0]=0; visited[0]=true; int c=0; while(!q.empty()){ int dq=q.front(); q.pop(); c++; for(int i=0;i<adj[dq].size();i++){ if(visited[adj[dq][i]]==false){ dist[adj[dq][i]]=dist[dq]+1; visited[adj[dq][i]]=true; q.push(adj[dq][i]); } } } cout<<dist[n-1]<<"\n"; return 0; }

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