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• What are good and bad jitter times for a LAN

  - by garyb32234234

  Ive just ran jperf (frontend to iperf) on our network between 2 workstations, its recorded jitter between 0.033ms and 0.048ms. Is this good or bad? Are there more variables that i would need to consider to make the decision? EDIT: TCP/IP Ethernet LAN 43 PCs 1 server, 100Mbits main switch, various small 8 port switches, test was done using UDP, Its a Windows Domain. I want to instal a few voip softphones on the workstations, see how many i can use that reliably work, im testing a few different workstations around the network to see where the best quality network paths are. Will also change some equipment if i identify bad connections.

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• High Jitter in NTP and poll value never goes above 128

  - by Aseem

  I have a lot of servers syncing to the same NTP servers (4). Not every server is in the same LAN. Some are 3 hops away from the NTP servers and some are 6 hops away. On couple of servers I see that the poll value never touches the 1024 mark and the jitter value is in double digits. Could it be due to the system hardware? These are windows servers (physical) and require as accurate time as possible. Please advice what I should do. Some of the stats that I collected manually from the bad box (which is 6 hops away from the ntp servers) C:\Program Files (x86)\NTP>ntpq -p -n remote refid st t when poll reach delay offset jitter ============================================================================== +*.*.*.25 *.*.*.233 2 u 12 128 377 1.210 -12.579 14.913 +*.*.*.26 *.*.*.233 2 u 96 128 377 1.067 -2.235 9.885 **.*.*.27 *.*.*.233 2 u 24 128 377 1.038 -7.569 11.178 +*.*.*.28 *.*.*.233 2 u 49 128 377 1.288 -11.058 14.544 remote refid st t when poll reach delay offset jitter ============================================================================== +*.*.*.25 *.*.*.233 2 u 124 128 377 0.614 -6.212 5.329 +*.*.*.26 *.*.*.233 2 u 93 128 377 0.910 -9.431 3.111 +*.*.*.27 *.*.*.233 2 u 1 128 377 0.824 -7.428 3.129 **.*.*.28 *.*.*.233 2 u 84 128 377 1.503 -8.230 3.511 remote refid st t when poll reach delay offset jitter ============================================================================== **.*.*.25 *.*.*.233 2 u 117 128 377 1.235 -4.084 11.405 +*.*.*.26 *.*.*.233 2 u 96 128 377 1.335 -11.813 13.130 +*.*.*.27 *.*.*.233 2 u 130 128 377 1.549 -14.036 16.381 -*.*.*.28 *.*.*.233 2 u 79 128 377 1.258 13.395 22.203 remote refid st t when poll reach delay offset jitter ============================================================================== **.*.*.25 *.*.*.233 2 u 88 128 377 1.235 -4.084 14.068 +*.*.*.26 *.*.*.233 2 u 63 128 377 1.335 -11.813 17.086 +*.*.*.27 *.*.*.233 2 u 103 128 377 1.549 -14.036 20.691 -*.*.*.28 *.*.*.233 2 u 47 128 377 1.258 13.395 20.231 remote refid st t when poll reach delay offset jitter ============================================================================== +*.*.*.25 *.*.*.233 2 u 47 64 377 0.652 -15.805 14.077 **.*.*.26 *.*.*.233 2 u 11 64 377 1.013 -14.423 11.375 -*.*.*.27 *.*.*.233 2 u 63 64 377 0.765 -2.030 7.680 +*.*.*.28 *.*.*.233 2 u 4 64 377 1.191 -17.980 14.393 remote refid st t when poll reach delay offset jitter ============================================================================== -*.*.*.25 *.*.*.233 2 u 3 128 377 1.576 18.665 21.999 +*.*.*.26 *.*.*.233 2 u 73 128 377 0.637 -5.012 14.405 **.*.*.27 *.*.*.233 2 u 127 128 377 0.272 -8.237 14.438 +*.*.*.28 *.*.*.233 2 u 123 128 377 1.190 -14.383 18.875 C:\Program Files (x86)\NTP>ntpdc -c loopinfo offset: -0.016430 s frequency: 7.106 ppm poll adjust: 18 watchdog timer: 133 s offset: -0.016430 s frequency: 7.106 ppm poll adjust: 18 watchdog timer: 341 s offset: -0.000149 s frequency: 6.645 ppm poll adjust: 0 watchdog timer: 383 s offset: 0.015735 s frequency: 6.725 ppm poll adjust: 7 watchdog timer: 577 s offset: -0.010331 s frequency: 6.748 ppm poll adjust: 21 watchdog timer: 567 s offset: -0.009427 s frequency: 6.687 ppm poll adjust: 28 watchdog timer: 301 s offset: -0.007361 s frequency: 6.612 ppm poll adjust: 30 watchdog timer: 155 s offset: -0.008106 s frequency: 4.358 ppm poll adjust: 30 watchdog timer: 291 s NTP.conf # NTP configuration file # Use drift file driftfile "C:\Program Files (x86)\NTP\ntp.drift" # Logs statistics loopstats peerstats clockstats statsdir "C:\Program Files (x86)\NTP\logs\" # directory for statistics files filegen peerstats file peerstats type day enable filegen loopstats file loopstats type day enable filegen clockstats file clockstats type day enable logfile "C:\Program Files (x86)\NTP\logs\syslog.txt" # Use specific NTP servers server *.*.*.25 minpoll 4 maxpoll 7 iburst server *.*.*.26 minpoll 4 maxpoll 7 iburst server *.*.*.27 minpoll 4 maxpoll 7 iburst server *.*.*.28 minpoll 4 maxpoll 7 iburst

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• Cocos2d: Changing b2Body x val every frame causes jitter

  - by Joey Green

  So, I have a jumping mechanism similar to what you would see in doodle jump where character jumps and you use the accelerometer to make character change direction left or right. I have a player object with position and a box2d b2Body with position. I'm changing the player X position via the accelerometer and the Y position according to box2d. pseudocode for this is like so -----accelerometer acceleration------ player.position = new X -----world update--------- physicsWorld-step() //this will get me the new Y according to the physics similation //so we keep the bodys Y value but change x to new X according to accelerometer data playerPhysicsBody.position = new pos(player.position.x, keepYval) player.position = playerPhysicsBody.position Now this is simplifying my code, but I'm doing the position conversion back and forth via mult or divide by PTM_. Well, I'm getting a weird jitter effect after I get big jump in acceleration data. So, my questions are: 1) Is this the right approach to have the accelerometer control the x pos and box2d control the y pos and just sync everthing up every frame? 2) Is there some issue with updating a b2body x position every frame? 3) Any idea what might be creating this jitter effect? I've collecting some data while running the game. Pre-body is before I set the x value on the b2Body in my update method after I world-step(). Post of course is afterwards. As you can see there is definitively a pattern. 012-06-19 08:14:13.118 Game[1073:707] pre-body pos 5.518720~24.362963 2012-06-19 08:14:13.120 Game[1073:707] post-body pos 5.060156~24.362963 2012-06-19 08:14:13.131 Game[1073:707] player velocity x: -31.833529 2012-06-19 08:14:13.133 Game[1073:707] delta 0.016669 2012-06-19 08:14:13.135 Game[1073:707] pre-body pos 5.060156~24.689455 2012-06-19 08:14:13.137 Game[1073:707] post-body pos 5.502138~24.689455 2012-06-19 08:14:13.148 Game[1073:707] player velocity x: -31.833529 2012-06-19 08:14:13.150 Game[1073:707] delta 0.016667 2012-06-19 08:14:13.151 Game[1073:707] pre-body pos 5.502138~25.006948 2012-06-19 08:14:13.153 Game[1073:707] post-body pos 5.043575~25.006948 2012-06-19 08:14:13.165 Game[1073:707] player velocity x: -31.833529 2012-06-19 08:14:13.167 Game[1073:707] delta 0.016644 2012-06-19 08:14:13.169 Game[1073:707] pre-body pos 5.043575~25.315441 2012-06-19 08:14:13.170 Game[1073:707] post-body pos 5.485580~25.315441 2012-06-19 08:14:13.180 Game[1073:707] player velocity x: -31.833529 2012-06-19 08:14:13.182 Game[1073:707] delta 0.016895 2012-06-19 08:14:13.185 Game[1073:707] pre-body pos 5.485580~25.614935 2012-06-19 08:14:13.188 Game[1073:707] post-body pos 5.026768~25.614935 2012-06-19 08:14:13.198 Game[1073:707] player velocity x: -31.833529 2012-06-19 08:14:13.199 Game[1073:707] delta 0.016454 2012-06-19 08:14:13.207 Game[1073:707] pre-body pos 5.026768~25.905428 2012-06-19 08:14:13.211 Game[1073:707] post-body pos 5.469213~25.905428 2012-06-19 08:14:13.217 Game[1073:707] acceleration x -0.137421 2012-06-19 08:14:13.223 Game[1073:707] player velocity x: -65.022644 2012-06-19 08:14:13.229 Game[1073:707] delta 0.016603

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• How to eliminate screen jitter in Flash game?

  - by Huang F. Lei

  We made a flash game with a big screen size(1000x600), and the terrain graphic will jitter while the screen scrolling(that's, camera moving with player) continuously. What's the root cause? Or if you know how to eliminate this problem, please tell me. Any help is appreciated. UPDATE: The map's size is more bigger than screen, e.g 6000x1200. And the map has more than one layer, generally it has 3 layers. Terrain is composed by tiles. And FPS is 24. If the FPS is set to 60, things will be better. But any way, it should work well at 24 FPS. I'm not sure if it is a natural problem of flash player, because some times a terrain object(e.g a house) look like a little bit distorted.

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• Need to translate a Rotation Matrix to Rotation y, x, z OpenGL & Jitter for 3D Game

  - by MineMan287

  I am using the Jitter Physics engine which gives a rotation matrix: M11 M12 M13 M21 M22 M23 M21 M32 M33 And I need it so OpenGL can use it for rotation GL.Rotate(xr, 1, 0, 0) GL.Rotate(yr, 0, 1, 0) GL.Rotate(zr, 0, 0, 1) Initially I Tried xr = M11 yr = M22 zr = M33 [1 0 0] [0 1 0] [0 0 1] Which did not work, please help, I have been struggling on this for days :( Re-Edit The blocks are stored in text files with Euler angles so it needs to be converted or the rendering engine will simply fail. I am now using the matrix in the text files. Example Block 1,1,1 'Size 0,0,0 'Position 255,255,255 'Colour 0,0,0,0,0,0,0,0,0 'Rotation Matrix

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• AABB vs OBB Collision Resolution jitter on corners

  - by patt4179

  I've implemented a collision library for a character who is an AABB and am resolving collisions between AABB vs AABB and AABB vs OBB. I wanted slopes for certain sections, so I've toyed around with using several OBBs to make one, and it's working great except for one glaring issue; The collision resolution on the corner of an OBB makes the player's AABB jitter up and down constantly. I've tried a few things I've thought of, but I just can't wrap my head around what's going on exactly. Here's a video of what's happening as well as my code: Here's the function to get the collision resolution (I'm likely not doing this the right way, so this may be where the issue lies): public Vector2 GetCollisionResolveAmount(RectangleCollisionObject resolvedObject, OrientedRectangleCollisionObject b) { Vector2 overlap = Vector2.Zero; LineSegment edge = GetOrientedRectangleEdge(b, 0); if (!SeparatingAxisForRectangle(edge, resolvedObject)) { LineSegment rEdgeA = new LineSegment(), rEdgeB = new LineSegment(); Range axisRange = new Range(), rEdgeARange = new Range(), rEdgeBRange = new Range(), rProjection = new Range(); Vector2 n = edge.PointA - edge.PointB; rEdgeA.PointA = RectangleCorner(resolvedObject, 0); rEdgeA.PointB = RectangleCorner(resolvedObject, 1); rEdgeB.PointA = RectangleCorner(resolvedObject, 2); rEdgeB.PointB = RectangleCorner(resolvedObject, 3); rEdgeARange = ProjectLineSegment(rEdgeA, n); rEdgeBRange = ProjectLineSegment(rEdgeB, n); rProjection = GetRangeHull(rEdgeARange, rEdgeBRange); axisRange = ProjectLineSegment(edge, n); float axisMid = (axisRange.Maximum + axisRange.Minimum) / 2; float projectionMid = (rProjection.Maximum + rProjection.Minimum) / 2; if (projectionMid > axisMid) { overlap.X = axisRange.Maximum - rProjection.Minimum; } else { overlap.X = rProjection.Maximum - axisRange.Minimum; overlap.X = -overlap.X; } } edge = GetOrientedRectangleEdge(b, 1); if (!SeparatingAxisForRectangle(edge, resolvedObject)) { LineSegment rEdgeA = new LineSegment(), rEdgeB = new LineSegment(); Range axisRange = new Range(), rEdgeARange = new Range(), rEdgeBRange = new Range(), rProjection = new Range(); Vector2 n = edge.PointA - edge.PointB; rEdgeA.PointA = RectangleCorner(resolvedObject, 0); rEdgeA.PointB = RectangleCorner(resolvedObject, 1); rEdgeB.PointA = RectangleCorner(resolvedObject, 2); rEdgeB.PointB = RectangleCorner(resolvedObject, 3); rEdgeARange = ProjectLineSegment(rEdgeA, n); rEdgeBRange = ProjectLineSegment(rEdgeB, n); rProjection = GetRangeHull(rEdgeARange, rEdgeBRange); axisRange = ProjectLineSegment(edge, n); float axisMid = (axisRange.Maximum + axisRange.Minimum) / 2; float projectionMid = (rProjection.Maximum + rProjection.Minimum) / 2; if (projectionMid > axisMid) { overlap.Y = axisRange.Maximum - rProjection.Minimum; overlap.Y = -overlap.Y; } else { overlap.Y = rProjection.Maximum - axisRange.Minimum; } } return overlap; } And here is what I'm doing to resolve it right now: if (collisionDetection.OrientedRectangleAndRectangleCollide(obb, player.PlayerCollision)) { var resolveAmount = collisionDetection.GetCollisionResolveAmount(player.PlayerCollision, obb); if (Math.Abs(resolveAmount.Y) < Math.Abs(resolveAmount.X)) { var roundedAmount = (float)Math.Floor(resolveAmount.Y); player.PlayerCollision._position.Y -= roundedAmount; } else if (Math.Abs(resolveAmount.Y) <= 30.0f) //Catch cases where the player should be able to step over the top of something { var roundedAmount = (float)Math.Floor(resolveAmount.Y); player.PlayerCollision._position.Y -= roundedAmount; } else { var roundedAmount = (float)Math.Floor(resolveAmount.X); player.PlayerCollision._position.X -= roundedAmount; } } Can anyone see what might be the issue here, or has anyone experienced this before that knows a possible solution? I've tried for a few days to figure this out on my own, but I'm just stumped.

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• Bitmap rotation jitter around pivot

  - by Manderin87

  I am working on a asteriods clone and I have the ship graphic loaded as a 96x96 bitmap. When the player rotates the ship I rotate the bitmap by degree (float). rotation function: if(m_Matrix == null) { m_Matrix = new Matrix(); } else { m_Matrix.reset(); } m_Matrix.setRotate(degree, m_BaseImage.getWidth() / 2, m_BaseImage.getHeight() / 2); m_RotatedImage = Bitmap.createBitmap(m_BaseImage, 0, 0, m_BaseImage.getWidth(), m_BaseImage.getHeight(), m_Matrix, true); draw function: m_Paint.setAntiAlias(true); m_Paint.setFilterBitmap(true); m_Paint.setDither(true); canvas.drawBitmap(m_RotatedImage, (int) posX - m_RotatedImage.getWidth() / 2, (int) posY - m_RotatedImage.getHeight() / 2, m_Paint); When the bitmap is drawn, the bitmap jitters slightly around the pivot. Can anyone fix or tell me why the bitmap is jittering around the pivot? It needs to be smooth.

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• Monitoring bandwidth/latency/jitter between 2 sites?

  - by TheCleaner

  I have 2 sites connected via an MPLS network and I'd like to do the following: setup a host on each end that can "talk" back and forth between each other and somehow report/log what kind of throughput, jitter, latency, etc. they are experiencing between each other in 5 minute intervals. Something similar to Qcheck but that can be automated. Bottom line is I'm trying to determine if the WAN network is "stable" throughout the day or if something is wrong. We have video conferences between these sites and even at 1024kbps calls we are experiencing delays and jitter. I'm hoping to exonerate the network with some testing.

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• How does iperf calculate throughput and jitter?

  - by Someone

  I've read that iperf basically tries to send as much information down a connection as quickly as possible reporting on the throughput achieved. This tool is especially useful in determining the volume of data that links between two machines can supply. is it possible to gather the same results by sending regular data, as in not testing data? what I'm trying to do is this; sending data in the foreground while in the back ground gather statistics (throughput and jitter). so can anyone tell me how iperf calculates these two values ?

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• I'm looking for a monitor tool to test Jitter, ICMP, Traceroute and other network issues

  - by Elad Dotan

  I'm looking for a monitor tool to test Jitter, ICMP, Traceroute and other network issues. it could be an application I run from my company Network in NY and London or a SAAS service that have a service that can do it for me. I have a problem in my Data Center that I would like to fix. it happens in different times of the day. I want to run the monitor for few days and save the results so we can analyze them. any idea? Thanks!! Elad.

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• Fast jitter library

  - by bugspy.net

  Anything out there other than llvm ? libjit doesn't seem very active.. I need a really fast and stable jitter. Even at the expense of features.. (preferably under c++)

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• Calculating packet loss, jitter and delay.

  - by George

  I am streaming an rtsp video to Android. How could I calculate network metrics like packet loss, jitter or delay?

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• jitter if multiple outliers in ggplot2 boxplot

  - by Andreas

  I am trying to find a suitable display to illustrate various properties within and across school classes. For each class there is only 15-30 data points (pupils). Right now i am leaning towards a whisker-less boxplot, showing only 1.,2. and 3. quartile + datapoints more then e.g. 1 population SD +/- the sample median. This I can do. However - I need to show this graph to some teachers, in order to gauge what they like most. I'd like to compare my graph with a normal boxplot. But the normal boxplot looks the same if there is only one outlier, or e.g. 5 outliers at the same value. In this case this would be a deal-breaker. e.g. test <-structure(list(value = c(3, 5, 3, 3, 6, 4, 5, 4, 6, 4, 6, 4, 4, 6, 5, 3, 3, 4, 4, 4, 3, 4, 4, 4, 3, 4, 5, 6, 6, 4, 3, 5, 4, 6, 5, 6, 4, 5, 5, 3, 4, 4, 6, 4, 4, 5, 5, 3, 4, 5, 8, 8, 8, 8, 9, 6, 6, 7, 6, 9), places = structure(c(1L, 2L, 1L, 1L, 1L, 2L, 1L, 2L, 1L, 2L, 1L, 2L, 2L, 2L, 2L, 2L, 1L, 1L, 2L, 2L, 2L, 1L, 2L, 1L, 1L, 1L, 1L, 2L, 1L, 2L, 1L, 2L, 2L, 2L, 1L, 2L, 1L, 2L, 2L, 1L, 1L, 2L, 2L, 1L, 1L, 1L, 1L, 2L, 1L, 1L, 2L, 2L, 2L, 1L, 1L, 2L, 2L, 1L, 2L, 1L), .Label = c("a", "b"), class = "factor")), .Names = c("value", "places"), row.names = c(NA, -60L), class = "data.frame") ggplot(test, aes(x=places,y=value))+geom_boxplot() Here there are two outliers at ("a",9) - but only one "dot" shown. So my question: How to jitter the outliers. And - what kind of display would you suggest for this kind of data?

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• How to read the statistics in Media Player Classic?

  - by netvope

  I understand that the two numbers under bitrate are the average bitrate and the current bitrate of the stream. But what are the two numbers under buffers? I suppose the second one is the amount of data loaded in memory, but what is the first number? The amount of data decoded? Also, why are there a jitter and a sync offset? (For your reference, here stream 0-6 are video, audio track 1, audio track 2, subtitle track 1 and subtitle track 2.)

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• Jitter during wall collisions with Bullet Physics: contact/penetration tolerance?

  - by Niriel

  I use the bullet physics engine through Panda3d. My scene is still very simple, think 'Wolfenstein3d': tile-based, walls are solid cubes. I expect walls to block the player, and I expect the player to slide along the walls in case of non-normal incidence. What I get is what I expect, with one difference: there is some jitter. If I try to force myself into the wall, then I see the frames blinking quickly between two positions. These differ by about 0.04 units of distance, which corresponds to 4 cm in my game. I noticed a 4 cm elsewhere: the bottom of my player capsule is 4 cm below ground, when at rest. Does that mean that there is somewhere in the Bullet engine a default 0.04-units-long tolerance to differentiate contact from collision? If so, what should I do ? Should I change the scale of my game so that these 0.04 units correspond to 0.4 cm, making the jitter ten times smaller? Or can I ask bullet to change its tolerance to a smaller value? Edit This is the jitter I get: 6.155 - 6.118 = 0.036 LPoint3f(0, 6.11694, 0.835) LPoint3f(0, 6.15499, 0.835) LPoint3f(0, 6.11802, 0.835) LPoint3f(0, 6.15545, 0.835) LPoint3f(0, 6.11817, 0.835) LPoint3f(0, 6.15726, 0.835) LPoint3f(0, 6.11876, 0.835) LPoint3f(0, 6.15911, 0.835) LPoint3f(0, 6.11937, 0.835) I found a setMargin method. I set it to 5 mm both on the BoxShape for the walls and on the Capsule shape for the player. It still jitters by about 35 mm as illustrated by this log (11.117 - 11.082 = 0.035): LPoint3f(0, 11.0821, 0.905) LPoint3f(0, 11.1169, 0.905) LPoint3f(0, 11.082, 0.905) LPoint3f(0, 11.117, 0.905) LPoint3f(0, 11.082, 0.905) LPoint3f(0, 11.117, 0.905) LPoint3f(0, 11.0821, 0.905) LPoint3f(0, 11.1175, 0.905) LPoint3f(0, 11.0822, 0.905) LPoint3f(0, 11.1178, 0.905) LPoint3f(0, 11.0823, 0.905) LPoint3f(0, 11.1183, 0.905) The margin on the capsule did change my penetration with the floor though, I'm a bit higher (0.905 instead of 0.835). However, it did not change anything when colliding with the walls. How can I make the collisions against the walls less jittery? Edit, the day after: After more investigation, it appears that dynamic objects behave well. My problem comes from the btKinematicCharacterController that I use for moving my character; that stuff is totally bugged, according to the whole Internet :/.

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• Netgear CG3000D new Modem/Router - Random High Ping

  - by justin.chmura

  Cox just recently came out and looked at my internet and decided that the modem I had was causing high latency issue. The speed was fine but the ping would spike to around 100 and over when gaming or putting a load more than browsing on the line. After they replaced it, it seems like I get better latency, but when it spikes, I get upwards of over 300 ping with like 500 jitter. I figured I would hit the serverfault universe before sending another email to Cox. I opted not to do the Cox setup as it was an extra $20 which I thought would have just setup the wireless (which I can handle). Is it a setting or something that I missed that needs to be setup? The firmware for the CG3000D is awful and not fun to use. I did change some hidden settings on the RgServices.asp page (I'll attach a screenshot). I've also heard that the Router/Modem combos are awful and that I should go back and just ask for a modem stand-alone. Any input is helpful. All screenshots: http://imgur.com/a/JX6qu#0

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• How can I stop my Jitter physics meshes being offset?

  - by ben1066

  I'm developing a C# game engine and have hit a snag trying to add physics. I'm using XNA for graphics and Jitter for physics. I am trying to split the XNA model into it's meshes, then create a ConvexHull for each mesh. I then attempt to combine those into a CompoundObject, this however isn't working and depending upon the model the meshes are offset by different amounts. This is the code I'm currently using and it gives me: Any ideas?

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• NTP service, offset increasing after sync

  - by Ajay

  I have installed Ubuntu 12.10 version on my PC. I am running NTP service having NTP server as GPS. I found that when we start NTP service by ntp start command, PC is able to sync with GPS as i get '*' symbol before GPS IP when i run ntpq -p command. This remains good for some time and then the * symbol is removed which means that PC is not synchronized to that server. Now, by running command ntpq -p it shows that all parameter are OK but as '*' is removed, slowly offset goes on increasing. remote refid st t when poll reach delay offset jitter ============================================================================== *192.168.100.33 .GPS. 1 u 7 16 1 2.333 23.799 0.808 remote refid st t when poll reach delay offset jitter ============================================================================== *192.168.100.33 .GPS. 1 u 14 16 3 2.333 23.799 0.879 remote refid st t when poll reach delay offset jitter ============================================================================== *192.168.100.33 .GPS. 1 u 11 16 7 2.333 23.799 1.500 remote refid st t when poll reach delay offset jitter ============================================================================== *192.168.100.33 .GPS. 1 u 8 16 17 2.333 23.799 2.177 below are the last 4 ntp status when sync is lost with GPS ============================================================================== 192.168.100.33 .GPS. 1 u 1 16 377 2.404 1169.94 1.735 remote refid st t when poll reach delay offset jitter ============================================================================== 192.168.100.33 .GPS. 1 u - 16 377 2.513 1171.80 0.898 remote refid st t when poll reach delay offset jitter ============================================================================== 192.168.100.33 .GPS. 1 u 15 16 377 2.513 1171.80 0.898 Since, GPS is already available, PC never re-synchronize itself to GPS later ON. I have to restart the ntp service and then PC synchronizes to GPS and '*' symbol arrives.

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• Hashing 3D position into 2D position

  - by notabene

  I am doing volumetric raycasting and curently working on depth jitter. I have 3D position on ray and want to sample 2D noise texture to jitter the depth. Function for converting (or hashing) 3D position to 2D have to produce absolutely different numbers for a little changes (especialy because i am sampling in texture space so sample values differs very very little) and have to be "shader-wise" - so forget about branches, cycles etc. I'm looking forward for yours nice and fast solutions.

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• I need help with 2D collision response (of stacking rotating polygons, with friction and gravity, for a game)

  - by Register Sole

  Hi I am looking for suggestions on how to write a collision response for game programming purpose (so not a scientific simulation). I am dealing with 2D polygons that are rotating, and I want them to be able to stack. I also want friction and gravity. I have a detection mechanism that returns the separating axis, how long the polygons are overlapping, and up to 2 points of contact. For the response, I am currently using an impulse-based response, which main idea is: find the separating axis, length of overlap, and the point of contact (if there are two, pick a random point between to simulate averaged force. i believe there are better ways than this) separate the object (modifying their positions, taking into account of their masses. i do not separate them completely though, to keep track that they are colliding to reduce jitter) calculate normal force based on the coefficient of restitution as if there is no friction. calculate friction, as if there is no normal force. I also assume that the direction of the friction is the same throughout the collision. apply the two forces (which result in a rather inaccurate result, since each force is calculated as if the other is not present. for non-rotating bodies though, this method is exact) I am aware that this method requires the coefficient of friction to be sufficiently small due to the assumption that the direction of friction stays the same in a collision. Also, the result is visually satisfying if gravity is not present. However, when there is gravity, objects on ground jitter and drift (even with zero coefficient of restitution)! It also happens for stacking objects. Larger coefficient of restitution and gravity increase the jittering. I hope you can help me with this. Some things i would like to know more about is how to handle collision with two point of contacts (how to end up having an object sitting still on the ground?), how to reduce, and prevent if possible, jitter and drift (do people use the most accurate method possible, or is there a trick to overcome this?), and how to handle multiple objects collision (for example, in the case of stacking objects, how do I check collisions between all of them and keep them all stable at every frame so they don't jitter?). A total reformulation of my algorithm is also welcomed, as long as it works. Another thing to note is that I am not making a Physics game, so I only need a visually satisfying response (though a realistic response is preferable, if it is not performance-heavy). But surely jittering and drifting objects on flat ground are not at all acceptable. In addition, I am a Physics student, so feel free to talk about impulse and whatever needed. Finally, I'm sorry for the long post. I tried to be as concise as I can. Thank you for reading it! EDIT It seems what I didn't manage to come up all this time is to separate resting contact as a class of its own and how to solve them. Currently reading the paper suggested by Jedediah. More suggestions on the topic are welcome :) CASE CLOSED After reading various papers referenced in the paper, successfully implemented simultaneous impulse method (referring to the original paper by Erin Catto, [Catt05]). Thanks maaaan!! The paper is wonderful. The current system is visibly much better than the previous. Still haven't separated resting contact as a class of its own though, which brings me to my next question. Love you all! Haha (sorry, I'm just so happy thanks to you).

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• 1000 HZ linux kernel necessary if I have tickless and high resolution timer?

  - by Bob

  I am trying to improve performance on my server. I have a few processes that need low jitter (less than 10ms variance). I have a load average of 4 maximum on an i7-920 (4 physical cores, 8 with HT). There are about 10 processes ranging from 40% to 90% of a core user mode. System usage is 3% total. Total CPU usage is 80% max. Will setting the kernel from 100hz to 1000hz improve the jitter if tickless and high resolution timers are already set? This page seems to indicate it still does something. https://lkml.org/lkml/2009/4/28/401 How about changing from voluntary (PREEMPT_VOLUNTARY) to preemptible (PREEMPT)?

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• List<T>.AddRange is causing a brief Update/Draw delay

  - by Justin Skiles

  I have a list of entities which implement an ICollidable interface. This interface is used to resolve collisions between entities. My entities are thus: Players Enemies Projectiles Items Tiles On each game update (about 60 t/s), I am clearing the list and adding the current entities based on the game state. I am accomplishing this via: collidableEntities.Clear(); collidableEntities.AddRange(players); collidableEntities.AddRange(enemies); collidableEntities.AddRange(projectiles); collidableEntities.AddRange(items); collidableEntities.AddRange(camera.VisibleTiles); Everything works fine until I add the visible tiles to the list. The first ~1-2 seconds of running the game loop causes a visible hiccup that delays drawing (so I can see a jitter in the rendering). I can literally remove/add the line that adds the tiles and see the jitter occur and not occur, so I have narrowed it down to that line. My question is, why? The list of VisibleTiles is about 450-500 tiles, so it's really not that much data. Each tile contains a Texture2D (image) and a Vector2 (position) to determine what is rendered and where. I'm going to keep looking, but from the top of my head, I can't understand why only the first 1-2 seconds hiccups but is then smooth from there on out. Any advice is appreciated.

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• ntpd server always in 'INIT' mode

  - by Deepak

  I'm running ntpd server in my ubuntu (10.04) machine. But it is always stays in the 'INIT' state as shown below. lyra@ws07475:~$ ntpq -p remote refid st t when poll reach delay offset jitter ============================================================================== europium.canoni .INIT. 16 u - 1024 0 0.000 0.000 0.000 lyra@ws07475:~$ Of course, this means that it is not keeping time. How can I start 'ntpd' server properly ? Please help.

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• 3D Ball Physics Theory: collision response on ground and against walls?

  - by David

  I'm really struggling to get a strong grasp on how I should be handling collision response in a game engine I'm building around a 3D ball physics concept. Think Monkey Ball as an example of the type of gameplay. I am currently using sphere-to-sphere broad phase, then AABB to OBB testing (the final test I am using right now is one that checks if one of the 8 OBB points crosses the planes of the object it is testing against). This seems to work pretty well, and I am getting back: Plane that object is colliding against (with a point on the plane, the plane's normal, and the exact point of intersection. I've tried what feels like dozens of different high-level strategies for handling these collisions, without any real success. I think my biggest problem is understanding how to handle collisions against walls in the x-y axes (left/right, front/back), which I want to have elasticity, and the ground (z-axis) where I want an elastic reaction if the ball drops down, but then for it to eventually normalize and be kept "on the ground" (not go into the ground, but also not continue bouncing). Without kluging something together, I'm positive there is a good way to handle this, my theories just aren't getting me all the way there. For physics modeling and movement, I am trying to use a Euler based setup with each object maintaining a position (and destination position prior to collision detection), a velocity (which is added onto the position to determine the destination position), and an acceleration (which I use to store any player input being put on the ball, as well as gravity in the z coord). Starting from when I detect a collision, what is a good way to approach the response to get the expected behavior in all cases? Thanks in advance to anyone taking the time to assist... I am grateful for any pointers, and happy to post any additional info or code if it is useful. UPDATE Based on Steve H's and eBusiness' responses below, I have adapted my collision response to what makes a lot more sense now. It was close to right before, but I didn't have all the right pieces together at the right time! I have one problem left to solve, and that is what is causing the floor collision to hit every frame. Here's the collision response code I have now for the ball, then I'll describe the last bit I'm still struggling to understand. // if we are moving in the direction of the plane (against the normal)... if (m_velocity.dot(intersection.plane.normal) <= 0.0f) { float dampeningForce = 1.8f; // eventually create this value based on mass and acceleration // Calculate the projection velocity PVRTVec3 actingVelocity = m_velocity.project(intersection.plane.normal); m_velocity -= actingVelocity * dampeningForce; } // Clamp z-velocity to zero if we are within a certain threshold // -- NOTE: this was an experimental idea I had to solve the "jitter" bug I'll describe below float diff = 0.2f - abs(m_velocity.z); if (diff > 0.0f && diff <= 0.2f) { m_velocity.z = 0.0f; } // Take this object to its new destination position based on... // -- our pre-collision position + vector to the collision point + our new velocity after collision * time // -- remaining after the collision to finish the movement m_destPosition = m_position + intersection.diff + (m_velocity * intersection.tRemaining * GAMESTATE->dt); The above snippet is run after a collision is detected on the ball (collider) with a collidee (floor in this case). With a dampening force of 1.8f, the ball's reflected "upward" velocity will eventually be overcome by gravity, so the ball will essentially be stuck on the floor. THIS is the problem I have now... the collision code is running every frame (since the ball's z-velocity is constantly pushing it a collision with the floor below it). The ball is not technically stuck, I can move it around still, but the movement is really goofy because the velocity and position keep getting affected adversely by the above snippet. I was experimenting with an idea to clamp the z-velocity to zero if it was "close to zero", but this didn't do what I think... probably because the very next frame the ball gets a new gravity acceleration applied to its velocity regardless (which I think is good, right?). Collisions with walls are as they used to be and work very well. It's just this last bit of "stickiness" to deal with. The camera is constantly jittering up and down by extremely small fractions too when the ball is "at rest". I'll keep playing with it... I like puzzles like this, especially when I think I'm close. Any final ideas on what I could be doing wrong here? UPDATE 2 Good news - I discovered I should be subtracting the intersection.diff from the m_position (position prior to collision). The intersection.diff is my calculation of the difference in the vector of position to destPosition from the intersection point to the position. In this case, adding it was causing my ball to always go "up" just a little bit, causing the jitter. By subtracting it, and moving that clamper for the velocity.z when close to zero to being above the dot product (and changing the test from <= 0 to < 0), I now have the following: // Clamp z-velocity to zero if we are within a certain threshold float diff = 0.2f - abs(m_velocity.z); if (diff > 0.0f && diff <= 0.2f) { m_velocity.z = 0.0f; } // if we are moving in the direction of the plane (against the normal)... float dotprod = m_velocity.dot(intersection.plane.normal); if (dotprod < 0.0f) { float dampeningForce = 1.8f; // eventually create this value based on mass and acceleration? // Calculate the projection velocity PVRTVec3 actingVelocity = m_velocity.project(intersection.plane.normal); m_velocity -= actingVelocity * dampeningForce; } // Take this object to its new destination position based on... // -- our pre-collision position + vector to the collision point + our new velocity after collision * time // -- remaining after the collision to finish the movement m_destPosition = m_position - intersection.diff + (m_velocity * intersection.tRemaining * GAMESTATE->dt); UpdateWorldMatrix(m_destWorldMatrix, m_destOBB, m_destPosition, false); This is MUCH better. No jitter, and the ball now "rests" at the floor, while still bouncing off the floor and walls. The ONLY thing left is that the ball is now virtually "stuck". He can move but at a much slower rate, likely because the else of my dot product test is only letting the ball move at a rate multiplied against the tRemaining... I think this is a better solution than I had previously, but still somehow not the right idea. BTW, I'm trying to journal my progress through this problem for anyone else with a similar situation - hopefully it will serve as some help, as many similar posts have for me over the years.

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• .NET processing unit [closed]

  - by configurator

  Do you think we'll ever see an IL (or other bytecode) processing unit? It sounds possible and would have a major benefit, because we wouldn't need the JITter. This isn't the same as compiling .NET directly to machine code, since the bytecode here is designed to be programmed and disassembled easily, unlike the bytecode used in x86 processors which is designed to work faster. What's stopping Intel (for example) from partnering with Microsoft and making such a .NET-optimised processor?

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