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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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  • 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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  • Quaternion based rotation and pivot position

    - by Michael IV
    I can't figure out how to perform matrix rotation using Quaternion while taking into account pivot position in OpenGL.What I am currently getting is rotation of the object around some point in the space and not a local pivot which is what I want. Here is the code [Using Java] Quaternion rotation method: public void rotateTo3(float xr, float yr, float zr) { _rotation.x = xr; _rotation.y = yr; _rotation.z = zr; Quaternion xrotQ = Glm.angleAxis((xr), Vec3.X_AXIS); Quaternion yrotQ = Glm.angleAxis((yr), Vec3.Y_AXIS); Quaternion zrotQ = Glm.angleAxis((zr), Vec3.Z_AXIS); xrotQ = Glm.normalize(xrotQ); yrotQ = Glm.normalize(yrotQ); zrotQ = Glm.normalize(zrotQ); Quaternion acumQuat; acumQuat = Quaternion.mul(xrotQ, yrotQ); acumQuat = Quaternion.mul(acumQuat, zrotQ); Mat4 rotMat = Glm.matCast(acumQuat); _model = new Mat4(1); scaleTo(_scaleX, _scaleY, _scaleZ); _model = Glm.translate(_model, new Vec3(_pivot.x, _pivot.y, 0)); _model =rotMat.mul(_model);//_model.mul(rotMat); //rotMat.mul(_model); _model = Glm.translate(_model, new Vec3(-_pivot.x, -_pivot.y, 0)); translateTo(_x, _y, _z); notifyTranformChange(); } Model matrix scale method: public void scaleTo(float x, float y, float z) { _model.set(0, x); _model.set(5, y); _model.set(10, z); _scaleX = x; _scaleY = y; _scaleZ = z; notifyTranformChange(); } Translate method: public void translateTo(float x, float y, float z) { _x = x - _pivot.x; _y = y - _pivot.y; _z = z; _position.x = _x; _position.y = _y; _position.z = _z; _model.set(12, _x); _model.set(13, _y); _model.set(14, _z); notifyTranformChange(); } But this method in which I don't use Quaternion works fine: public void rotate(Vec3 axis, float angleDegr) { _rotation.add(axis.scale(angleDegr)); // change to GLM: Mat4 backTr = new Mat4(1.0f); backTr = Glm.translate(backTr, new Vec3(_pivot.x, _pivot.y, 0)); backTr = Glm.rotate(backTr, angleDegr, axis); backTr = Glm.translate(backTr, new Vec3(-_pivot.x, -_pivot.y, 0)); _model =_model.mul(backTr);///backTr.mul(_model); notifyTranformChange(); }

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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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  • 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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  • Elliptical orbit modeling

    - by Nathon
    I'm playing with orbits in a simple 2-d game where a ship flies around in space and is attracted to massive things. The ship's velocity is stored in a vector and acceleration is applied to it every frame as appropriate given Newton's law of universal gravitation. The point masses don't move (there's only 1 right now) so I would expect an elliptical orbit. Instead, I see this: I've tried with nearly circular orbits, and I've tried making the masses vastly different (a factor of a million) but I always get this rotated orbit. Here's some (D) code, for context: void accelerate(Vector delta) { velocity = velocity + delta; // Velocity is a member of the ship class. } // This function is called every frame with the fixed mass. It's a // method of the ship's. void fall(Well well) { // f=(m1 * m2)/(r**2) // a=f/m // Ship mass is 1, so a = f. float mass = 1; Vector delta = well.position - loc; float rSquared = delta.magSquared; float force = well.mass/rSquared; accelerate(delta * force * mass); }

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  • Build a view frustum from angles

    - by MulletDevil
    I have 4 angles, left, right, top & bottom. These angles are in degrees. They define the angle between the forward vector and the corresponding side. I am trying to use these to calculate the required values for Perseective Off Centre function found here http://docs.unity3d.com/Documentation/ScriptReference/Camera-projectionMatrix.html I tried doing (near plane-far plane) * Tan(angle) But that didn't give the correct results.

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  • Getting isometric grid coordinates from standard X,Y coordinates

    - by RoryHarvey
    I'm currently trying to add sprites to an isometric Tiled TMX map using Objects in cocos2d. The problem is the X and Y metadata from TMX object are in standard 2d format (pixels x, pixels y), instead of isometric grid X and Y format. Usually you would just divide them by the tile size, but isometric needs some sort of transform. For example on a 64x32 isometric tilemap of size 40 tiles by 40 tiles an object at (20,21)'s coordinates come out as (640,584) So the question really is what formula gets (20,21) from (640,584)?

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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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  • 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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  • Projecting onto different size screens by cropping

    - by Jason
    Hi, I am building a phone application which will display a shape on screen. The shape should look the same on different screen sizes. I. Decided the best way to do this is to show more of the background on larger screen keeping the shapes proportion the same on all screens. My problem is I am not sure how to achieve this, I can query the screen size at runtime and calculate how different it is from the six is designed for but I am not sure what to do with this value. What kind of projection should I use for my orthographic matrix an hour will I display more on larger screens and not loose information on smaller screens? Thanks, Jason.

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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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  • D3DXMatrixDecompose gives different quaternion than D3DXQuaternionRotationMatrix

    - by Fraser
    In trying to solve this problem, I tracked down the problem to the conversion of the rotation matrix to quaternion. In particular, consider the following matrix: -0.02099178 0.9997436 -0.008475631 0 0.995325 0.02009799 -0.09446743 0 0.09427284 0.01041905 0.9954919 0 0 0 0 1 SlimDX.Quaternion.RotationMatrix (which calls D3DXQuaternionRotationMatrix gives a different answer than SlimDX.Matrix.Decompose (which uses D3DXMatrixDecompose). The answers they give (after being normalized) are: X Y Z W Quaternion.RotationMatrix -0.05244324 0.05137424 0.002209336 0.9972991 Matrix.Decompose 0.6989997 0.7135442 -0.03674842 -0.03006023 Which are totally different (note the signs of X, Z, and W are different). Note that these aren't q/-q (two quaternions that represent the same rotation); they face completely different directions. I've noticed that with matrices for rotations very close to that one (successive frames in the animation) that the Matrix.Decompose version gives a solution that flips around wildly and occasionally goes into the desired position, while the Quaternion.RotationMatrix version gives solutions that are stable but go in the wrong direction. This is only for the right arm in my animation -- for the left arm, both functions give the correct solution, which is the same quaternion within error tolerances. This makes me think that there's some sort of numeric instability or weird stuff with signs going on. I tried implementing this and then this, but both gave me a completely incorrect solution (even for the matricies where the SlimDX ones were working correctly) -- maybe the rows and columns are flipped?

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  • How to check if a server runs in pressing mode

    - by Ice
    Hi there, Layout: i have at customer side a server (win2003 R2 SP2 standard edition 32-bit) with a sql-server 2005 and some databases. This system starts with the /3GB-Switch. The system reports 3.25 GB RAM and taskmanager reports the process of sqlserver.exe with 2758255 K as the process with the highest consumption. The OS separates RAM for applications and for itself, normaly 50:50. But here we have the /3GB-Switch aktivated and i think the part for the applications is more than 50% of RAM. Knowledge (or better not knowledge): Somebody told me that if the OS runs out of memory within his part of RAM, the server runs into pressing mode. Questions: What is this pressing mode? Is pressing mode possible at all in this szenario? What should be done to get more performance out of this sql-server, beside optimizing the database and all this stuff.

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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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  • 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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  • 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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  • Virtualbox fullscreen mode problem

    - by AtharvaI
    hi all I have a slightly weird issue with virtualbox. My host OS is Win7 (64-bit) and guest OS is Ubuntu 10.10(64-bit). When I switch to fullscreen mode in virtualbox, ubuntu display resizes to fit my screen size. however, after that the display is not updated. So if i click a menu or something I don't see it appear. but it seems to work in the background. if i click a menu in fullscreen mode, i don't see anything happen, but if then switch to windowed mode I see the menu already open. I have installed virtuabox guest additions. if any has a similar issue or has found a solution please let me know thanks.

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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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  • Estimate angle to launch missile, maths question

    - by Jonathan
    I've been working on this for an hour or two now and my maths really isn't my strong suit which is definitely not a good thing for a game programmer but that shouldn't stop me enjoying a hobby surely? After a few failed attempts I was hoping someone else out there could help so here's the situation. I'm trying to implement a bit of faked intelligence when the A.I fires it's missiles at a target in a 2D game world. By predicting the likely position the target will be in given it's current velocity and the time it will take the missile to reach it's target. I created an image to demonstrate my thinking: http://i.imgur.com/SFmU3.png which also contains the logic I use for accelerating the missile after launch. The ship that fires the missile can fire within a total of 40 degree angle, 20 either side of itself, but this could likely become variable. My current attempt was to break the space between the two lines into segments which match the targets width. Then calculate the time it would take the missile to get to that location using the formula. So for each iteration of this we total up the values and that tells us the distance travelled, ad it would then just need compared to distance to the segment. startVelocity * ((startVelocity * acceleration)^(currentframe-1) So for example. If we start at a velocity of 1f/frame with an acceleration of 0.1f the formula, at frame 4, would be 1 * (1.1^3) = 1.331 But I quickly realized I was getting lost when trying to put this into practice. Does this seem like a correct starting point or am I going completely the wrong way about it? Any pointers would help me greatly. Maths really isn't my strong suit so I get easily lost in these matters and don't even really know a good phrase to search for with this. So I guess in summary my question is more about the correct way to approach this problem and any additional code samples on top of that would be great but I'm not averse to working out the complete code from helpful pointers.

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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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  • 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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  • 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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  • 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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