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  • Algorithm to calculate trajectories from vector field

    - by cheeesus
    I have a two-dimensional vector field, i.e., for each point (x, y) I have a vector (u, v), whereas u and v are functions of x and y. This vector field canonically defines a set of trajectories, i.e. a set of paths a particle would take if it follows along the vector field. In the following image, the vector field is depicted in red, and there are four trajectories which are partly visible, depicted in dark red: I need an algorithm which efficiently calculates some trajectories for a given vector field. The trajectories must satisfy some kind of minimum denseness in the plane (for every point in the plane we must have a 'nearby' trajectory), or some other condition to get a reasonable set of trajectories. I could not find anything useful on Google on this, and Stackexchange doesn't seem to handle the topic either. Before I start devising such an algorithm by myself: Are there any known algorithms for this problem? What is their name, for which keywords do I have to search?

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  • Render 3d object to 2d surface (embedded system)

    - by Martin Berger
    i am working on an embedded system of a sort, and in some free time i would like to test its drawing capabilities. System in question is ARM Cortex M3 microcontroller attached to EasyMX Stellaris board. And i have a small 320x240 TFT screen :) Now, i have some free time each day and i want to create rotating cube. Micro C PRO for ARM doesnt have 3d drawing capabilities, which means it must be done in software. From the book Introduction to 3D Game Programming with DirectX 10 i know matrix algebra for transformations but that is cool when you have DirectX to set camera right. I gues i could make 2d object to rotate, but how would i go with 3d one? Any ideas and examples are welcome. Although i would prefer advices. I'd like to understand this.

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  • Error running phusion passenger in standalone mode

    - by msidell
    I'm trying to run standalone phusion passenger so that I can run different ruby rvm configurations on the same host. I already have ruby and passenger running fine on this host. I am following the instructions here. When I run standalone passenger the first time, it appears to successfully install nginx. But then when it tries to run, I get this error: [root@clark directra]# passenger start -a 127.0.0.1 -p 3001 -d --user dweb *** ERROR *** Could not start Passenger Nginx core: nginx: [alert] could not open error log file: open() "/tmp/passenger-standalone.16757/logs/error.log" failed (2: No such file or directory) nginx: [alert] Unable to start the Phusion Passenger watchdog (/var/lib/passenger-standalone/3.0.11-x86-ruby1.9.3-linux-gcc4.1.2-1002/support/ agents/PassengerWatchdog): Permission denied (13) (13: Permission denied) Stopping web server... done FWIW, /tmp is writeable. Any idea what's wrong?

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  • How should I sort images in an isometric game so that they appear in the correct order?

    - by Andrew
    Hi! This seems like a rather simple problem but I am having a lot of difficulty with it. What should I do to properly sort images in an isometric game? In a normal 2d top-down game one could use the screen y axis to sort the images. In this example the trees are properly sorted but the isometric walls are not. Example image: sorted by screen y Wall2 is one pixel below wall1 therefore it is drawn after wall1. If I sort by the isometric y axis the walls appear in the correct order but the trees do not. Example image: sorted by isometric y

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  • What's the normal way machine-learning algorithms are integrated into normal programs?

    - by Benjamin Pollack
    I'm currently taking a machine learning course for fun, and the course heavily focuses on Matlab/Octave to write the code. One thing mentioned in the course is that, while Matlab/Octave are great for prototyping, they're very rarely used for production algorithms. Instead, those algorithms are typically rewritten in C++/Python/etc., using appropriate libraries, before reaching customers. Fair enough; I get that. But here's my question: is that done for cultural reasons, for technical reasons, or because there is really no language that provides Matlab/Octave-like fluidity, but in a compiled form that can be linked from C/C++/$MainstreamLanguage? The game industry uses Lua for game logic because it's easy to embed, and vastly superior for expressing things like AI. Likewise, there are Prolog variants for rules-heavy applications, Scheme variants for compilers, and so on. If there's a matrix equivalent language, what is it? If there isn't, why is this field different?

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  • Interpolation between two 3D points?

    - by meds
    I'm working with some splines which define a path a character follows (you can see a gameplay video here to get a better understanding of what's going on: http://www.youtube.com/watch?v=BndobjOiZ6g). Basically the characters 'forward' look direction is set to the 'forward' direction of the spline and when players tilt their phone left and right the character is strafed along its 'right' coordinate. The issue with this is (rather obviously) in performance, interpolating over a spline to find the nearest position and tangent relative to the player is an incredibly costly operation. To get by this I cache a finite number of positions in what I call 'SplineDetails', the class is as follows: public class SplineDetails { public SplineDetails() { Forward = Vector3.forward; Position = Vector3.one * float.MaxValue; Alpha = -1; } public float Alpha; // [0,1] measured along length of spline where 0 is the initial point and 1 is the end point of the spline public Vector3 Position; // the point of the spline at this alpha public Vector3 Forward; // the forward tangent of the spline at this alpha } I populate this with say 30 coordinates and I can give a rough estimate of a coordinate and 'forward' based on a position past in. It's not as accurate but it's much faster. But now I'd like to make the system work better by estimating positions and 'forward' directions by interpolating between two of the cached points though I'm stuck trying to figure out some logic. My first problem is, how can I determine between which two points the object is? Given each point can be placed at different intervals along the spline it could mean that two points in front or behind the object can be closer to the object. The other problem is to figure out the proportion between the two paths it's between, i.e. if there is a point a at coordinate (0,0,0) and point b at coordinate (1,0,0) if the object is at position (0.5,0,0) then the result it should give is '0.5' (as it is equal distance away from point a and point b). That's a simple example, but what if the object is at coordinate (0.5,3,0) for example?

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  • Position Reconstruction from Depth by inverting Perspective Projection

    - by user1294203
    I had some trouble reconstructing position from depth sampled from the depth buffer. I use the equivalent of gluPerspective in GLM. The code in GLM is: template GLM_FUNC_QUALIFIER detail::tmat4x4 perspective ( valType const & fovy, valType const & aspect, valType const & zNear, valType const & zFar ) { valType range = tan(radians(fovy / valType(2))) * zNear; valType left = -range * aspect; valType right = range * aspect; valType bottom = -range; valType top = range; detail::tmat4x4 Result(valType(0)); Result[0][0] = (valType(2) * zNear) / (right - left); Result[1][2] = (valType(2) * zNear) / (top - bottom); Result[2][3] = - (zFar + zNear) / (zFar - zNear); Result[2][4] = - valType(1); Result[3][5] = - (valType(2) * zFar * zNear) / (zFar - zNear); return Result; } There doesn't seem to be any errors in the code. So I tried to invert the projection, the formula for the z and w coordinates after projection are: and dividing z' with w' gives the post-projective depth (which lies in the depth buffer), so I need to solve for z, which finally gives: Now, the problem is I don't get the correct position (I have compared the one reconstructed with a rendered position). I then tried using the respective formula I get by doing the same for this Matrix. The corresponding formula is: For some reason, using the above formula gives me the correct position. I really don't understand why this is the case. Have I done something wrong? Could someone enlighten me please?

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  • Opengl-es picking object

    - by lacas
    I saw a lot of picking code opengl-es, but nothing worked. Can someone give me what am I missing? My code is (from tutorials/forums) Vec3 far = Camera.getPosition(); Vec3 near = Shared.opengl().getPickingRay(ev.getX(), ev.getY(), 0); Vec3 direction = far.sub(near); direction.normalize(); Log.e("direction", direction.x+" "+direction.y+" "+direction.z); Ray mouseRay = new Ray(near, direction); for (int n=0; n<ObjectFactory.objects.size(); n++) { if (ObjectFactory.objects.get(n)!=null) { IObject obj = ObjectFactory.objects.get(n); float discriminant, b; float radius=0.1f; b = -mouseRay.getOrigin().dot(mouseRay.getDirection()); discriminant = b * b - mouseRay.getOrigin().dot(mouseRay.getOrigin()) + radius*radius; discriminant = FloatMath.sqrt(discriminant); double x1 = b - discriminant; double x2 = b + discriminant; Log.e("asd", obj.getName() + " "+discriminant+" "+x1+" "+x2); } } my camera vectors: //cam Vec3 position =new Vec3(-obj.getPosX()+x, obj.getPosZ()-0.3f, obj.getPosY()+z); Vec3 direction =new Vec3(-obj.getPosX(), obj.getPosZ(), obj.getPosY()); Vec3 up =new Vec3(0.0f, -1.0f, 0.0f); Camera.set(position, direction, up); and my picking code: public Vec3 getPickingRay(float mouseX, float mouseY, float mouseZ) { int[] viewport = getViewport(); float[] modelview = getModelView(); float[] projection = getProjection(); float winX, winY; float[] position = new float[4]; winX = (float)mouseX; winY = (float)Shared.screen.width - (float)mouseY; GLU.gluUnProject(winX, winY, mouseZ, modelview, 0, projection, 0, viewport, 0, position, 0); return new Vec3(position[0], position[1], position[2]); } My camera moving all the time in 3d space. and my actors/modells moving too. my camera is following one actor/modell and the user can move the camera on a circle on this model. How can I change the above code to working?

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  • Optimized algorithm for line-sphere intersection in GLSL

    - by fernacolo
    Well, hello then! I need to find intersection between line and sphere in GLSL. Right now my solution is based on Paul Bourke's page and was ported to GLSL this way: // The line passes through p1 and p2: vec3 p1 = (...); vec3 p2 = (...); // Sphere center is p3, radius is r: vec3 p3 = (...); float r = ...; float x1 = p1.x; float y1 = p1.y; float z1 = p1.z; float x2 = p2.x; float y2 = p2.y; float z2 = p2.z; float x3 = p3.x; float y3 = p3.y; float z3 = p3.z; float dx = x2 - x1; float dy = y2 - y1; float dz = z2 - z1; float a = dx*dx + dy*dy + dz*dz; float b = 2.0 * (dx * (x1 - x3) + dy * (y1 - y3) + dz * (z1 - z3)); float c = x3*x3 + y3*y3 + z3*z3 + x1*x1 + y1*y1 + z1*z1 - 2.0 * (x3*x1 + y3*y1 + z3*z1) - r*r; float test = b*b - 4.0*a*c; if (test >= 0.0) { // Hit (according to Treebeard, "a fine hit"). float u = (-b - sqrt(test)) / (2.0 * a); vec3 hitp = p1 + u * (p2 - p1); // Now use hitp. } It works perfectly! But it seems slow... I'm new at GLSL. You can answer this questions in two ways: Tell me there is no solution, showing some proof or strong evidence. Tell me about GLSL features (vector APIs, primitive operations) that makes the above algorithm faster, showing some example. Thanks a lot!

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  • How to get a point to the left/right of a vector

    - by MulletDevil
    I have a position vector of a point in space and a quaternion for it's rotation. What i'm trying to calculate is a point too the left and a point to the right. I have the position and rotation(quaternion) of the red dot. What I want is to get the position of the green dots. I have a float value for the distance I want these points to be. With only the position and rotation is it possible to get a unit direction vector pointing left/right which I can multiply by my float value? Edit: I also know the original direction vector.

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  • How do I find the angle required to point to another object?

    - by Ginamin
    I am making an air combat game, where you can fly a ship in a 3D space. There is an opponent that flies around as well. When the opponent is not on screen, I want to display an arrow pointing in the direction the user should turn, as such: So, I took the camera location and the oppenent location and did this: double newDirection = atan2(activeCamera.location.y-ship_wrap.location.y, activeCamera.location.x-ship_wrap.location.x); After which, I get the position on the circumferance of a circle which surrounds my crosshairs, like such: trackingArrow.position = point((60*sin(angle)+240),60*cos(angle)+160); It all works fine, except it's the wrong angle! I assume my calculation for the new direction is incorrect. Can anyone help?

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  • Pixelated PDF in Apple Preview slideshow mode, but not in regular window

    - by Zack
    I have a PDF which is a presentation exported from OpenOffice. Two of the slides in this presentation have embedded .eps graphs. When I run the presentation using Preview's slideshow mode, the graphs are severely aliased and the axes are illegible. But when I just view the PDF in regular windowed mode, the graphs are properly antialiased and legible. Is there any way to get Preview to do the same display that it does in windowed mode, but in fullscreen (no window title, no menu bar)? (I don't want to just run the presentation from OpenOffice, because OpenOffice shows the same horrible aliasing effects plus it takes about 30 seconds to show the slide. I don't have, and don't want, Acrobat or MS Office. However, please do feel free to suggest other programs for doing PDF-based slideshows.)

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  • Projected trajectory of a vehicle?

    - by mac
    In the game I am developing, I have to calculate if my vehicle (1) which in the example is travelling north with a speed V, can reach its target (2). The example depict the problem from atop: There are actually two possible scenarios: V is constant (resulting in trajectory 4, an arc of a circle) or the vehicle has the capacity to accelerate/decelerate (trajectory 3, an arc of a spiral). I would like to know if there is a straightforward way to verify if the vehicle is able to reach its target (as opposed to overshooting it). I'm particularly interested in trajectory #3, as I the only thing I could think of is integrating the position of the vehicle over time. EDIT: of course the vehicle has always the capacity to steer, but the steer radius vary with its speed (think to a maximum lateral g-force). EDIT2: also notice that (as most of the vehicles in real life) there is a minimum steering radius for the in-game ones too).

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  • Rotating a child shape relative to its parent's orientation

    - by user1423893
    When rotating a shape using a quaternion value I also wish rotate its child shape. The parent and child shapes both start with different orientations but their relative orientations should always be the same. How can I use the difference between the previous and current quaternions of the parent shape in order to transform the child segment and rotate it relative to its parent shape? public Quaternion Orientation { get { return entity.Orientation; } set { Quaternion previousValue = entity.Orientation; entity.Orientation = value; // Use the difference between the quaternion values to update child orientation } }

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  • 1 to 1 Comparison and Ranking System

    - by David
    I'm looking to create a comparison and ranking system which allows users to view 2 items, click on the one that they feel is the better one and then get presented with 2 more random items and continue to do this until they decide to stop. In the background, I want the system to use these wins and loses to rank each item in an overall ranking table so I can then see what is #1 and what isn't. I haven't got a clue where to begin with the formula, but I image I need to log wins and loses. Any help/direction appreciated!

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  • Initial direction of intersection between two moving vehicles?

    - by Larolaro
    I'm working with a bit of projectile prediction for my AI and I'm looking for some ideas, any input? If a blue vehicle is moving in a direction at a constant speed of X m/s and a stationary orange vehicle has a rocket that travels Y m/s, which initial direction would the orange vehicle have to fire the rocket for it to hit the blue vehicle at the earliest time in the future? Thanks for reading!

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  • Confusion about Rotation matrices from Euler Angles

    - by xEnOn
    I am trying to learn more about Euler Angles so as to help myself in understanding how I can control my camera better in the game. I came across the following formula that converts Euler Angles to rotation matrices: In the equation, I could see that the first matrix from the left is the rotation matrix about x-axis, the second is about y-axis and the third is about z-axis. From my understanding about ordinary matrix transformations, the later transformation is always applied to the right hand side. And if I'm right about this, then the above equation should have a rotation order starting from rotating about z-axis, y-axis, then finally x-axis. But, from the symbols it seems that the rotation order start rotating about x-axis, then y-axis, then finally z-axis. What should the actual order of the rotation be? Also, I am confuse about if the input vector, in this case, would be a row vector on the left, or a column vector on the right?

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  • How to balance this Pokémon simulator metagame by feedback?

    - by Dokkat
    This is a Pokémon simulator where you build a team of 6 pokémon and battle with someone. Unfortunately, some Pokémon are stronger than others and only a few of the hundredth species are practical. I'm trying to create a metagame where all of them are competitive. For this, I am tagging a Pokémon with a parameter (level) that changes it's strength and scales up/down depending on the it's performance. That is, if the system detects Mewtwo is overperforming, it should decrease it's level tag until Mewtwo is balanced. The question is: how can I identify if a Pokémon is causing an unbalance? The data I have is the historic of the battles (player 1, player 2, pokémon list, winner). The most basic solution I can think of is victory/loss counting.

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  • I am looking to create realistic car movement using vectors

    - by bobthemac
    I have goggled how to do this and found this http://www.helixsoft.nl/articles/circle/sincos.htm I have had a go at it but most of the functions that were showed didn't work I just got errors because they didn't exist. I have looked at the cos and sin functions but don't understand how to use them or how to get the car movement working correctly using vectors. I have no code because I am not sure what to do sorry. Any help is appreciated. EDIT: I have restrictions that I must use the TL engine for my game, I am not allowed to add any sort of physics engine. It must be programmed in c++. Here is a sample of what i got from trying to follow what was done in the link I provided. if(myEngine->KeyHeld(Key_W)) { length += carSpeedIncrement; } if(myEngine->KeyHeld(Key_S)) { length -= carSpeedIncrement; } if(myEngine->KeyHeld(Key_A)) { angle -= carSpeedIncrement; } if(myEngine->KeyHeld(Key_D)) { angle += carSpeedIncrement; } carVolocityX = cos(angle); carVolocityZ = cos(angle); car->MoveX(carVolocityX * frameTime); car->MoveZ(carVolocityZ * frameTime);

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  • How should I sort images in an isometric game so that they appear in the correct order?

    - by Andrew
    This seems like a rather simple problem but I am having a lot of difficulty with it. What should I do to properly sort images in an isometric game? In a normal 2d top-down game one could use the screen y axis to sort the images. In this example the trees are properly sorted but the isometric walls are not. Example image: sorted by screen y Wall2 is one pixel below wall1 therefore it is drawn after wall1. If I sort by the isometric y axis the walls appear in the correct order but the trees do not. Example image: sorted by isometric y

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  • Run chromium-browser on Linux with fullscreen and application modes ON

    - by LukaszBachman
    Some time ago chromium-browser was supporting a so called "kiosk mode", which could start chromium in fullscreen and removed unnecessary titlebar and some other UI components. Right now it looks like it's no longer supported. After few updates the same script that I was using for launching kiosk mode is not behaving the same. I checked some sites and learned that recently they introduced a so called "application mode" (--app=http://mysite.com). All cool and neat, but application mode does no longer enforce fullscreen. How could I force chromium-browser to behave exactly as in previous kiosk mode?

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  • AABB - AABB Collision, which face do I hit?

    - by PeeS
    To allow my objects to slide when they collide, I need to : Know which face of the AABB they collide with. Calculate the normal to that face. Return the normal and calculate the impulse that to apply to the player's velocity. Question How can I calculate which face of the AABB I collided with, knowing that I have two AABB's colliding? One is the player and the other is a world object. Here's what that looks like (problem collision circled in white): Thank you for your help.

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  • Is acousting fingerprinting too broad for one audio file only?

    - by IBG
    So we were looking for some topics related to audio analysis and found acoustic fingerprinting. As it is, it seems like the most famous application for it is for identification of music. Enter our manager, who requested us to research and possible find an algorithm or existing code that we can use for this very simple approach (like it's easy, source codes don't show up like mushrooms): Always-on app for listening Compare the audio patterns to a single audio file (assume sound is a simple beep) If beep is detected, send notification to server With a flow this simple, do you think acousting fingerprinting is a broad approach to use? Should we stop and take another approach? Where to best start? We haven't started anything yet (on the development side) on this regard, so I want to get other opinion if this is pursuit is worth it or moot.

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  • Run non-interactive script in single user mode

    - by Jed Daniels
    Is it possible to run a "startup" script when booting into single user mode? I need to be able to boot into single user mode, run my script, then reboot into multiuser mode without any human interaction. I've done a bunch of research and can't find anything that is clear on the topic, although of course I could replace something else that does run with a wrapper that also launches my script, but I'd prefer to do it in some official way. Ideally, the solution will work in FreeBSD 6 and up, but I'm willing to accept only new versions if it just doesn't exist in the older revs.

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