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• Convert vector interpolation to quaternion interpolation? (Catmull-Rom)

  - by edA-qa mort-ora-y

  I have some existing code which does catmull-rom interpolation on two vectors (facing and up). I'm converting this to use quaternions instead (to replace the two vectors). Is there a general way to convert the vector based interpolation to a quaternion one? The approach I'm using now is to exact the axis and angle from the quanternion. I then interpolate each of those independently and convert back to a quaternion. Is there a more direct method?

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• Interpolation using a sprite's previous frame and current frame

  - by user22241

  Overview I'm currently using a method which has been pointed out to me is extrapolation rather than interolation. As a result, I'm also now looking into the possibility of using another method which is based on a sprite's position at it's last (rendered) frame and it's current one. Assuming an interpolation value of 0.5 this is, (visually), how I understand it should affect my sprite's position.... This is how I'm obtaining an inerpolation value: public void onDrawFrame(GL10 gl) { // Set/re-set loop back to 0 to start counting again loops=0; while(System.currentTimeMillis() > nextGameTick && loops < maxFrameskip) { SceneManager.getInstance().getCurrentScene().updateLogic(); nextGameTick += skipTicks; timeCorrection += (1000d / ticksPerSecond) % 1; nextGameTick += timeCorrection; timeCorrection %= 1; loops++; tics++; } interpolation = (float)(System.currentTimeMillis() + skipTicks - nextGameTick) / (float)skipTicks; render(interpolation); } I am then applying it like so (in my rendering call): render(float interpolation) { spriteScreenX = (spriteScreenX - spritePreviousX) * interpolation + spritePreviousX; spritePreviousX = spriteScreenX; // update and store this for next time } Results This unfortunately does nothing to smooth the movement of my sprite. It's pretty much the same as without the interpolation code. I can't get my head around how this is supposed to work and I honestly can't find any decent resources which explain this in any detail. My understanding of extrapolation is that when we arrive at the rendering call, we calculate the time between the last update call and the render call, and then adjust the sprite's position to reflect this time (moving the sprite forward) - And yet, this (Interpolation) is moving the sprite back, so how can this produce smooth results? Any advise on this would be very much appreciated. Edit I've implemented the code from OriginalDaemon's answer like so: @Override public void onDrawFrame(GL10 gl) { newTime = System.currentTimeMillis()*0.001; frameTime = newTime - currentTime; if ( frameTime > (dt*25)) frameTime = (dt*25); currentTime = newTime; accumulator += frameTime; while ( accumulator >= dt ) { SceneManager.getInstance().getCurrentScene().updateLogic(); previousState = currentState; t += dt; accumulator -= dt; } interpolation = (float) (accumulator / dt); render(); } Interpolation values are now being produced between 0 and 1 as expected (similar to how they were in my original loop) - however, the results are the same as my original loop (my original loop allowed frames to skip if they took too long to draw which I think this loop is also doing). I appear to have made a mistake in my previous logging, it is logging as I would expect it to (interpolated position does appear to be inbetween the previous and current positions) - however, the sprites are most definitely choppy when the render() skipping happens.

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• Handling early/late/dropped packets for interpolation in a 3D multiplayer game

  - by Ben Cracknell

  I'm working on a multiplayer game that for the purposes of this question, is most similar to Team Fortress. Each network data packet will contain the 3D position of the target moving object. (this object could be another player) The packets are sent on a fixed interval, and linear interpolation will be used to smooth the transition between packets. Under normal circumstances, interpolation will occur between the second-to-last packet, and the last packet received. The linear interpolation algorithm is the same as this post: Interpolating positions in a multiplayer game I have the same issue as in that post, but the answers don't seem like they will work in my situation. Consider the following scenario: Normal packet timing, everything is okay The next expected packet is late. That's okay, we'll just extrapolate based on previous positions The late packet eventually arrives with corrections to our extrapolation. Now what do we do with its information? The answers on the above post suggest we should just interpolate to this new packet's position, but that would not work at all. If we have already extrapolated past that point in time, moving back would cause rubber-banding. The issue is similar in the case of an early or dropped packet. So I believe what I am looking for is some way to smoothly deal with new information in an ongoing interpolation/extrapolation process. Since I might be moving on to quadratic or even cubic interpolation, it would be great if the same solutiuon could be applied to those as well.

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• Multiplayer Network Game - Interpolation and Frame Rate

  - by J.C.

  Consider the following scenario: Let's say, for sake of example and simplicity, that you have an authoritative game server that sends state to its clients every 45ms. The clients are interpolating state with an interpolation delay of 100 ms. Finally, the clients are rendering a new frame every 15ms. When state is updated on the client, the client time is set from the incoming state update. Each time a frame renders, we take the render time (client time - interpolation delay) and identify a previous and target state to interpolate from. To calculate the interpolation amount/factor, we take the difference of the render time and previous state time and divide by the difference of the target state and previous state times: var factor = ((renderTime - previousStateTime) / (targetStateTime - previousStateTime)) Problem: In the example above, we are effectively displaying the same interpolated state for 3 frames before we collected the next server update and a new client (render) time is set. The rendering is mostly smooth, but there is a dash of jaggedness to it. Question: Given the example above, I'd like to think that the interpolation amount/factor should increase with each frame render to smooth out the movement. Should this be considered and, if so, what is the best way to achieve this given the information from above?

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• Fixed timestep and interpolation question

  - by Eric

  I'm following Glenn Fiedlers excellent Fix Your Timestep! tutorial to step my 2D game. The problem I'm facing is in the interpolation phase in the end. My game has a Tween-function which lets me tween properties of my game entites. Properties such as scale, shear, position, color, rotation etc. Im curious of how I'd interpolate these values, since there's a lot of them. My first thought is to keep a previous value of every property (colorPrev, scalePrev etc.), and interpolate between those. Is this the correct method? To interpolate my characters I use their velocity; renderPostion = position + (velocity * interpolation), but I cannot apply that to color for example. So what is the desired method to interpolate various properties or a entity? Is there any rule of thumb to use?

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• Depth interpolation for z-buffer, with scanline

  - by Twodordan

  I have to write my own software 3d rasterizer, and so far I am able to project my 3d model made of triangles into 2d space: I rotate, translate and project my points to get a 2d space representation of each triangle. Then, I take the 3 triangle points and I implement the scanline algorithm (using linear interpolation) to find all points[x][y] along the edges(left and right) of the triangles, so that I can scan the triangle horizontally, row by row, and fill it with pixels. This works. Except I have to also implement z-buffering. This means that knowing the rotated&translated z coordinates of the 3 vertices of the triangle, I must interpolate the z coordinate for all other points I find with my scanline algorithm. The concept seems clear enough, I first find Za and Zb with these calculations: var Z_Slope = (bottom_point_z - top_point_z) / (bottom_point_y - top_point_y); var Za = top_point_z + ((current_point_y - top_point_y) * Z_Slope); Then for each Zp I do the same interpolation horizontally: var Z_Slope = (right_z - left_z) / (right_x - left_x); var Zp = left_z + ((current_point_x - left_x) * Z_Slope); And of course I add to the zBuffer, if current z is closer to the viewer than the previous value at that index. (my coordinate system is x: left - right; y: top - bottom; z: your face - computer screen;) The problem is, it goes haywire. The project is here and if you select the "Z-Buffered" radio button, you'll see the results... (note that the rest of the options before "Z-Buffered" use the Painter's algorithm to correctly order the triangles. I also use the painter's algorithm -only- to draw the wireframe in "Z-Buffered" mode for debugging purposes) PS: I've read here that you must turn the z's into their reciprocals (meaning z = 1/z) before you interpolate. I tried that, and it appears that there's no change. What am I missing? (could anyone clarify, precisely where you must turn z into 1/z and where to turn it back?)

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• GLSL custom interpolation filter

  - by Cyan

  I'm currently building a fragment shader which is using several textures to render the final pixel color. The textures are not really textures, they are in fact "input data" to be used in the formula to generate the final color. The problem I've got is that the texture are getting bi-linear-filtered, and therefore the input data as well. This results in many unwanted side-effects, especially when final rendered texture is "zoomed" compared to original resolution. Removing the side effect is a complex task, and only result in "average" rendering. I was thinking : well, all my problems seems to come from the "default" bi-linear filtering on these input data. I can't move to GL_NEAREST either, since it would create "blocky" rendering. So i guess the better way to proceed is to be fully in charge of the interpolation. For this to work, i would need the input data at their "natural" resolution (so that means 4 samples), and a relative position between the sampled points. Is that possible, and if yes, how ? [EDIT] Since i started this question, i found this internet entry, which seems to (mostly) answer my needs. http://www.gamerendering.com/2008/10/05/bilinear-interpolation/ One aspect of the solution worry me though : the dimensions of the texture must be provided in an argument. It seems there is no way to "find this information transparently". Adding an argument into the rendering pipeline is unwelcomed though, since it's not under my responsibility, and translates into adding complexity for others.

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• UV texture mapping with perspective correct interpolation

  - by Twodordan

  I am working on a software rasterizer for educational purposes and I am having issues with the texturing. The problem is, only one face of the cube gets correctly textured. The rest are stretched edges: You can see the running program online here. I have used cartesian coordinates, and all I do is interpolate the uv values along the scanlines. The general formula I use for interpolating the uv coordinates is pretty much the one I use for the z-buffering interpolation and looks like this (in this case for horizontal scanlines): u_Slope = (right.u - left.u) / (triangleRight_x - triangleLeft_x); v_Slope = (right.v - left.v) / (triangleRight_x - triangleLeft_x); //[...] new_u = left.u + ((currentX_onScanLine - triangleLeft_x) * u_Slope); new_v = left.v + ((currentX_onScanLine - triangleLeft_x) * v_Slope); Then, when I add each point to the pixel buffer, I restore z and uv: z = (1/z); uv.u = Math.round(uv.u * z *100);//*100 because my texture is 100x100px uv.v = Math.round(uv.v * z *100); Then I turn the u v indexes into one index in order to fetch the correct pixel from the image data (which is a 1 dimensional px array): var index = texture.width * uv.u + uv.v; //and the rest is unimportant imagedata[index].RGBA bla bla The interpolation formula is correct considering the consistency of the texture (including the straight stripes). However, I seem to get quite a lot of 0 values for either u or v. Which is probably why I only get one face right. Furthermore, why is the texture flipped horizontally? (the "1" is flipped) I must get some sleep now, but before I get into further dissecting of every single value to see what goes wrong, Can someone more experienced guess why might this be happening, just by looking at the cube? "I have no idea what I'm doing" (it's my first time implementing a rasterizer). Did I miss an important stage? Thanks for any insight. PS: My UV values are as follows: { u:0, v:0 }, { u:0, v:0.5 }, { u:0.5, v:0.5 }, { u:0.5, v:0 }, { u:0, v:0 }, { u:0, v:0.5 }, { u:0.5, v:0.5 }, { u:0.5, v:0 }

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• HLSL 5 interpolation issues

  - by metredigm

  I'm having issues with the depth components of my shadowmapping shaders. The shadow map rendering shader is fine, and works very well. The world rendering shader is more problematic. The only value which seems to definitely be off is the pixel's position from the light's perspective, which I pass in parallel to the position. struct Pixel { float4 position : SV_Position; float4 light_pos : TEXCOORD2; float3 normal : NORMAL; float2 texcoord : TEXCOORD; }; The reason that I used the semantic 'TEXCOORD2' on the light's pixel position is because I believe that the problem lies with Direct3D's interpolation of values between shaders, and I started trying random semantics and also forcing linear and noperspective interpolations. In the world rendering shader, I observed in the pixel shader that the Z value of light_pos was always extremely close to, but less than the W value. This resulted in a depth result of 0.999 or similar for every pixel. Here is the vertex shader code : struct Vertex { float3 position : POSITION; float3 normal : NORMAL; float2 texcoord : TEXCOORD; }; struct Pixel { float4 position : SV_Position; float4 light_pos : TEXCOORD2; float3 normal : NORMAL; float2 texcoord : TEXCOORD; }; cbuffer Camera : register (b0) { matrix world; matrix view; matrix projection; }; cbuffer Light : register (b1) { matrix light_world; matrix light_view; matrix light_projection; }; Pixel RenderVertexShader(Vertex input) { Pixel output; output.position = mul(float4(input.position, 1.0f), world); output.position = mul(output.position, view); output.position = mul(output.position, projection); output.world_pos = mul(float4(input.position, 1.0f), world); output.world_pos = mul(output.world_pos, light_view); output.world_pos = mul(output.world_pos, light_projection); output.texcoord = input.texcoord; output.normal = input.normal; return output; } I suspect interpolation to be the culprit, as I used the camera matrices in place of the light matrices in the vertex shader, and had the same problem. The problem is evident as both of the same vectors were passed to a pixel from the VS, but only one of them showed a change in the PS. I have already thoroughly debugged the matrices' validity, the cbuffers' validity, and the multiplicative validity. I'm very stumped and have been trying to solve this for quite some time. Misc info : The light projection matrix and the camera projection matrix are the same, generated from D3DXMatrixPerspectiveFovLH(), with an FOV of 60.0f * 3.141f / 180.0f, a near clipping plane of 0.1f, and a far clipping plane of 1000.0f. Any ideas on what is happening? (This is a repost from my question on Stack Overflow)

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• Issue with multiplayer interpolation

  - by Ben Cracknell

  In a fast-paced multiplayer game I'm working on, there is an issue with the interpolation algorithm. You can see it clearly in the image below. Cyan: Local position when a packet is received Red: Position received from packet (goal) Blue: Line from local position to goal when packet is received Black: Local position every frame As you can see, the local position seems to oscillate around the goals instead of moving between them smoothly. Here is the code: // local transform position when the last packet arrived. Will lerp from here to the goal private Vector3 positionAtLastPacket; // location received from last packet private Vector3 goal; // time since the last packet arrived private float currentTime; // estimated time to reach goal (also the expected time of the next packet) private float timeToReachGoal; private void PacketReceived(Vector3 position, float timeBetweenPackets) { positionAtLastPacket = transform.position; goal = position; timeToReachGoal = timeBetweenPackets; currentTime = 0; Debug.DrawRay(transform.position, Vector3.up, Color.cyan, 5); // current local position Debug.DrawLine(transform.position, goal, Color.blue, 5); // path to goal Debug.DrawRay(goal, Vector3.up, Color.red, 5); // received goal position } private void FrameUpdate() { currentTime += Time.deltaTime; float delta = currentTime/timeToReachGoal; transform.position = FreeLerp(positionAtLastPacket, goal, currentTime / timeToReachGoal); // current local position Debug.DrawRay(transform.position, Vector3.up * 0.5f, Color.black, 5); } /// <summary> /// Lerp without being locked to 0-1 /// </summary> Vector3 FreeLerp(Vector3 from, Vector3 to, float t) { return from + (to - from) * t; } Any idea about what's going on?

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• Frame Interpolation issues for skeletal animation

  - by sebby_man

  I'm trying to animate in-between keyframes for skeletal animation but having some issues. Each joint is represented by a quaternion and there is no translation component. When I try to slerp between the orientations at the two key frames, I got a very wacky animation. I know my skinning equation is right because the animation is perfectly fine when the animation is directly on a keyframe rather than in-between two. I'm using glm's built in mix function to do the slerp, so I don't think there are any problems with the actual slerp implementation. There's really one thing left that could be wrong here. I must not be in the correct space to do slerp. Right now the orientations are in joint local space. Do I have to be in world space? In some other space along the way? I have the bind pose matrix and world-space transformation matrix at my disposal if those are needed.

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• Interpolation gives the appearance of collisions

  - by Akroy

  I'm implementing a simple 2D platformer with a constant speed update of the game logic, but with the rendering done as fast as the machine can handle. I interpolate positions between actual game updates by just using the position and velocity of objects at the last update. This makes things look really smooth in general, but when something hits a wall/floor, it appears to go through the wall for a moment before being positioned correctly. This is because the interpolator is not taking walls into account, so it guesses the position into walls until the actual game update fixes it. Are there any particularly elegant solutions for this? Simply increasing the update rate seems like a band-aid solution, and I'm trying to avoid increasing the system reqs. I could also check for collisions in the actual interpolator, but that seems like heavy overhead, and then I'm no longer dividing the drawing and the game updating.

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• Interpolation of time series data in R

  - by Pierreten

  I'm not sure what i'm missing here, but i'm basically trying to compute interpolated values for a time series; when I directly plot the series, constraining the interpolation points with "interpolation.date.vector", the plot is correct: plot(date.vector,fact.vector,ylab='Quantity') lines(spline(date.vector,fact.vector,xout=interpolation.date.vector)) When I compute the interpolation, store it in an intermediate variable, and then plot the results; I get a radically incorrect result: intepolated.values <- spline(date.vector,fact.vector,xout=interpolation.date.vector) plot(intepolated.values$x,intepolated.values$y) lines(testinterp$x,testinterp$y) Doesn't the lines() function have to execute the spline() function to retrieve the interpolated points in the same way i'm doing it?

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• Rotation Interpolation

  - by Rob

  Hello, NB: I'll present this question in degrees purely for simplicity, radians, degrees, different zero-bearing, the problem is essentially the same. Does anyone have any ideas on the code behind rotational interpolation? Given a linear interpolation function: Lerp(from, to, amount), where amount is 0...1 which returns a value between from and to, by amount. How could I apply this same function to a rotational interpolation between 0 and 360 degrees? Given that degrees should not be returned outside 0 and 360. Given this unit circle for degrees: where from = 45 and to = 315, the algorithm should take the shortest path to the angle, i.e. it should go through zero, to 360 and then to 315 - and not all the way round 90, 180, 270 to 315. Is there a nice way to achieve this? Or is it going to just be a horrid mess of if() blocks? Am I missing some well understood standard way of doing this? Any help would be appreciated.

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• How does interpolation actually work to smooth out an object's movement?

  - by user22241

  I've asked a few similar questions over the past 8 months or so with no real joy, so I am going make the question more general. I have an Android game which is OpenGL ES 2.0. within it I have the following Game Loop: My loop works on a fixed time step principle (dt = 1 / ticksPerSecond) loops=0; while(System.currentTimeMillis() > nextGameTick && loops < maxFrameskip){ updateLogic(dt); nextGameTick+=skipTicks; timeCorrection += (1000d/ticksPerSecond) % 1; nextGameTick+=timeCorrection; timeCorrection %=1; loops++; } render(); My intergration works like this: sprite.posX+=sprite.xVel*dt; sprite.posXDrawAt=sprite.posX*width; Now, everything works pretty much as I would like. I can specify that I would like an object to move across a certain distance (screen width say) in 2.5 seconds and it will do just that. Also because of the frame skipping that I allow in my game loop, I can do this on pretty much any device and it will always take 2.5 seconds. Problem However, the problem is that when a render frame skips, the graphic stutter. It's extremely annoying. If I remove the ability to skip frames, then everything is smooth as you like, but will run at different speeds on different devices. So it's not an option. I'm still not sure why the frame skips, but I would like to point out that this is Nothing to do with poor performance, I've taken the code right back to 1 tiny sprite and no logic (apart from the logic required to move the sprite) and I still get skipped frames. And this is on a Google Nexus 10 tablet (and as mentioned above, I need frame skipping to keep the speed consistent across devices anyway). So, the only other option I have is to use interpolation (or extrapolation), I've read every article there is out there but none have really helped me to understand how it works and all of my attempted implementations have failed. Using one method I was able to get things moving smoothly but it was unworkable because it messed up my collision. I can foresee the same issue with any similar method because the interpolation is passed to (and acted upon within) the rendering method - at render time. So if Collision corrects position (character now standing right next to wall), then the renderer can alter it's position and draw it in the wall. So I'm really confused. People have said that you should never alter an object's position from within the rendering method, but all of the examples online show this. So I'm asking for a push in the right direction, please do not link to the popular game loop articles (deWitters, Fix your timestep, etc) as I've read these multiple times. I'm not asking anyone to write my code for me. Just explain please in simple terms how Interpolation actually works with some examples. I will then go and try to integrate any ideas into my code and will ask more specific questions if need-be further down the line. (I'm sure this is a problem many people struggle with).

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• Akima interpolation of an array of doubles

  - by David Rutten

  Assuming I have an array of doubles, what's a good algorithm to sample this series using Akima interpolation? I'm too stupid to translate that mathematical description into code. // values is an array of doubles // idx is the index of the left-hand value for the current interpolation // t is the normalized parameter between values[idx] and values[idx+1] // Don't worry about array bounds, I'll handle that separately. public double InterpolateAkima(double[] values, int idx, double t) { ...? }

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• C# vector class - Interpolation design decision

  - by Benjamin

  Currently I'm working on a vector class in C# and now I'm coming to the point, where I've to figure out, how i want to implement the functions for interpolation between two vectors. At first I came up with implementing the functions directly into the vector class... public class Vector3D { public static Vector3D LinearInterpolate(Vector3D vector1, Vector3D vector2, double factor) { ... } public Vector3D LinearInterpolate(Vector3D other, double factor { ... } } (I always offer both: a static method with two vectors as parameters and one non-static, with only one vector as parameter) ...but then I got the idea to use extension methods (defined in a seperate class called "Interpolation" for example), since interpolation isn't really a thing only available for vectors. So this could be another solution: public class Vector3D { ... } public static class Interpolation { public static Vector3D LinearInterpolate(this Vector3D vector, Vector3D other, double factor) { ... } } So here an example how you'd use the different possibilities: { var vec1 = new Vector3D(5, 3, 1); var vec2 = new Vector3D(4, 2, 0); Vector3D vec3; vec3 = vec1.LinearInterpolate(vec2, 0.5); //1 vec3 = Vector3D.LinearInterpolate(vec1, vec2, 0.5); //2 //or with extension-methods vec3 = vec1.LinearInterpolate(vec2, 0.5); //3 (same as 1) vec3 = Interpolation.LinearInterpolation(vec1, vec2, 0.5); //4 } So I really don't know which design is better. Also I don't know if there's an ultimate rule for things like this or if it's just about what someone personally prefers. But I really would like to hear your opinions, what's better (and if possible why ).

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• Interpolation and Morphing of an image in labview and/or openCV

  - by Marc

  I am working on an image manipulation problem. I have an overhead projector that projects onto a screen, and I have a camera that takes pictures of that. I can establish a 1:1 correspondence between a subset of projector coordinates and a subset of camera pixels by projecting dots on the screen and finding the centers of mass of the resulting regions on the camera. I thus have a map proj_x, proj_y <-- cam_x, cam_y for scattered point pairs My original plan was to regularize this map using the Mathscript function griddata. This would work fine in MATLAB, as follows [pgridx, pgridy] = meshgrid(allprojxpts, allprojypts) fitcx = griddata (proj_x, proj_y, cam_x, pgridx, pgridy); fitcy = griddata (proj_x, proj_y, cam_y, pgridx, pgridy); and the reverse for the camera to projector mapping Unfortunately, this code causes Labview to run out of memory on the meshgrid step (the camera is 5 megapixels, which apparently is too much for labview to handle) I then started looking through openCV, and found the cvRemap function. Unfortunately, this function takes as its starting point a regularized pixel-pixel map like the one I was trying to generate above. However, it made me hope that functions for creating such a map might be available in openCV. I couldn't find it in the openCV 1.0 API (I am stuck with 1.0 for legacy reasons), but I was hoping it's there or that someone has an easy trick. So my question is one of the following 1) How can I interpolate from scattered points to a grid in openCV; (i.e., given z = f(x,y) for scattered values of x and y, how to fill an image with f(im_x, im_y) ? 2) How can I perform an image transform that maps image 1 to image 2, given that I know a scattered mapping of points in coordinate system 1 to coordinate system 2. This could be implemented either in Labview or OpenCV. Note: I am tagging this post delaunay, because that's one method of doing a scattered interpolation, but the better tag would be "scattered interpolation"

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• 1D Function into 2D Function Interpolation

  - by Drazick

  Hello. I have a 1D function which I want to interpolate into 2D function. I know the function should have "Polar Symmetry". Hence I use the following code (Matlab Syntax): Assuming the 1D function is LSF of the length 15. [x, y] = meshgrid([-7:7]); r = sqrt(x.^2 + y.^2); PSF = interp1([-7:7], LSF, r(:)); % Sometimes using 'spline' option, same results. PSF = reshape(PSF, [7, 7]); I have few problems: 1. Got some overshoot at the edges (As there some Extrapolation). 2. Can't enforce some assumptions (Monotonic, Non Negative). Is there a better Interpolation method for those circumstances? I couldn't find "Lanczos" based interpolation I can use the same way as interp1 (For a certain vector of points, in "imresize" you can only set the length). Is there such function anywhere? Has anyone encountered a function which allows enforcing some assumptions (Monotonically Decreasing, Non Negative, etc..). Thanks.

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• How to match end-of-line multiple times in a regex without interpolation

  - by harschware

  Hi, if I have a input with new lines in it like: [INFO] xyz [INFO] How can I pull out the xyz part. I tried a pattern like /^\[INFO\]$(.*?)$\[INFO\]/ms, but perl gives me: Use of uninitialized value $\ in regexp compilation at scripts\t.pl line 6. I've been trying things to get interpolation to stop like using qr// but alas, no love.

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• Interpolation of scattered data: What could I do?

  - by Simon

  Hi! I need your help. I'm working on a 3D chart in Java using Java 3D. It should be able to display a bunch of measured values. As measured, the data I get is scattered. This means I will have to interpolate the missing points in order to get my surface plotted nicely. I didn't study all that 3D-Geometry stuff yet and I don't know where to start. My idea is to triangulate the points to a surface and then, based on the triangulation, interpolate the missing points. (see this to have a rough idea of what I want to achieve) Does someone have experiences with the interpolation of scattered data? Is my approach the right one? If yes, what kind of data structures and algorithms will I need in order to triangulate my points cloud?

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• OpenGL Colour Interpolation

  - by Will-of-fortune

  I'm currently working on an little project in C++ and OpenGL and am trying to implement a colour selection tool similar to that in photoshop, as below. However I am having trouble with interpolation of the large square. Working on my desktop computer with a 8800 GTS the result was similar but the blending wasn't as smooth. This is the code I am using: GLfloat swatch[] = { 0,0,0, 1,1,1, mR,mG,mB, 0,0,0 }; GLint swatchVert[] = { 400,700, 400,500, 600,500, 600,700 }; glVertexPointer(2, GL_INT, 0, swatchVert); glColorPointer(3, GL_FLOAT, 0, swatch); glDrawArrays(GL_QUADS, 0, 4); Moving onto my laptop with Intel Graphics HD 3000, this result was even worse with no change in code. I thought it was OpenGL splitting the quad into two triangles, so I tried rendering using triangles and interpolating the colour in the middle of the square myself but it still doesnt quite match the result I was hoping for. Any help would be appreciated. Thanks.

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• Simplest Algorithm for 2D Interpolation

  - by Gayan

  I have two shapes which are cross sections of a channel. I want to calculate the cross section of an intermediate point between the two defined points. What's the simplest algorithm to use in this situation? P.S. I came across several algorithms like natural neighbor and poisson which seemed complex. I'm looking for a simple solution which could be implemented quickly

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• Algorithm for 2D Interpolation

  - by Gayan

  I have two shapes which are cross sections of a channel. I want to calculate the cross section of an intermediate point between the two defined points. What's the simplest algorithm to use in this situation? P.S. I came across several algorithms like natural neighbor and poisson which seemed complex. I'm looking for a simple solution which could be implemented quickly EDIT: I removed the word "Simplest" from the title since it might be misleading

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• Double interpolation of regular expressions in Perl

  - by tomdee

  I have a Perl program that stores regular expressions in configuration files. They are in the form: regex = ^/d+$ Elsewhere, the regex gets parsed from the file and stored in a variable - $regex. I then use the variable when checking the regex, e.g. $lValid = ($valuetocheck =~ /$regex/); I want to be able to include perl variables in the config file, e.g. regex = ^\d+$stored_regex$ But I can't work out how to do it. When regular expressions are parsed by Perl they get interpreted twice. First the variables are expanded, and then the the regular expression itself is parsed. What I need is a three stage process: First interpolate $regex, then interpolate the variables it contains and then parse the resulting regular expression. Both the first two interpolations need to be "regular expression aware". e.g. they should know that the string contain $ as an anchor etc... Any ideas?

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