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I made the following animation, but the disks and the rectangle are shaking, breaking the smoothness of the motion. enter image description here

Here is a minimal example. If you look carefully you will see the disks are shaking.

tab = Table[ConstantArray[Cos[0.3* t], 3], {t, 2, 6, 0.02}];
l0 = 1;
show[x_] := 
 Block[{}, 
  Graphics[{Rectangle[{0, -.5}, {.5, .5}], 
    Rectangle[{5, -.5}, {5.5, .5}], 
    Table[Disk[{x[[i]] + i*l0, 0}, 0.2], {i, 3}]}, ImageSize -> 800]]
plots = Table[show[tab[[i]]], {i, 1, Length@tab, 1}];
Export["temp.gif", plots]

enter image description here

Please not the rectangles are still here, so I don't think it is a scaling issue. This is supported by the fact that specifying PlotRange does not change anything (ImagePadding -> None does not either).

 plots = Table[Show[show[tab[[i]]], PlotRange -> {{0, 5.5}, {-.5, .5}}, 
     PlotRangePadding -> None], {i, 1, Length@tab, 1}]

enter image description here

A comment suggested to change the frame rate; though less obvious, the shaking motion is still present:

  Export["temp.gif", plots, "DisplayDurations" -> 1/50.]

enter image description here

Please not the shaking is not introduced by Export, since it is also observed with ListAnimate@plots.

The question is, of course, how to prevent this shaking?

Interestingly, changing Disks to Point works, but I am looking for a more robust solution (in particular, Arrows also "shake" and can't be easily replaced...).

 show[x_] := Block[{}, Graphics[{Rectangle[{0, -.5}, {.5, .5}], 
   Rectangle[{5, -.5}, {5.5, .5}], PointSize[0.08], 
   Table[Point[{x[[i]] + i*l0, 0}], {i, 3}]}, ImageSize -> 800]]

The following animation is fine: there is no vertical jumps. enter image description here

Animations made with version: 11.0.0 for Linux x86 (64-bit) (July 28, 2016).

Using OSX and MMA 11.1, halirutan reduced the gap between the disks to better highlight the shaking motion:

enter image description here

Of course the motion should be smooth, but that's really not the case.

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    $\begingroup$ I guess problem will be solved by increasing the frame rate. Your animation is just 51 frame for ~5 sec of duration but normal video has 24 fps namely for smooth movements. $\endgroup$
    – Rom38
    Commented Apr 11, 2017 at 3:53
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    $\begingroup$ I don't see the problem on Win7 V11.1. Sometimes fixing PlotRange/ImagePadding and friends helps. $\endgroup$
    – Kuba
    Commented Apr 11, 2017 at 6:17
  • $\begingroup$ the jump at the end is of couse because you arent doing an exact full cycle. $\endgroup$
    – george2079
    Commented Apr 11, 2017 at 11:52
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    $\begingroup$ I'm on V11.0.0.0 on OSX and I do not see the vertical jumping. Sounds like it might be Linux specific. $\endgroup$
    – N.J.Evans
    Commented Apr 12, 2017 at 13:48
  • 1
    $\begingroup$ OSX and Mathematica 11.1 here. I change your animation a bit, putting the disks close together. It looks awful. $\endgroup$
    – halirutan
    Commented Apr 12, 2017 at 18:24

1 Answer 1

Reset to default
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One way to avoid rasterization rounding issues is to work directly with rasters and ImageCompose

r = 20
n = 5
dx = 50
wbar = 10
amp = 50
back = ImageCompose[
   Image[ConstantArray[
     1, {70, dx (n - 1) + 2 amp + 2 wbar  + 2 r + 1}]] ,
   ConstantArray[Image[ConstantArray[0, {50, wbar}]], 
    2] , {{wbar/2, 35} , {dx (n - 1) + 2 amp + (3/2) wbar  + 2 r + 1, 
     35}}];
frames = (ImageCompose[back, 
        ConstantArray[Image[1 - DiskMatrix[r]], n],
        Table[{# + r + 10 + dx i, 35}, {i, 0, 
          n - 1}]] &@ (amp (Sin[# +  Pi/2] + 1) )) & /@ 
   Range[ 0 , 2 Pi  , Pi/20];

Export["test.gif", frames]

enter image description here

enter image description here

combining with the spring graphics might be a challenge..

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