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Activity Forums Adobe After Effects Expressions Speed of objects

  • Posted by Faza Lutfi on April 9, 2005 at 9:24 pm

    Hi all..
    i have got two comps and in each there are two objects moving around..
    I am trying to make sure that the two objects have the same speed. They have to have exactly the same speed…
    I did go in to the distance speed graph in the timeline.. but this will not allow me to enter a speed when i try to change it it only changes in funny incriments so i am unable to get an exact value there…
    anyone… please help..

    Faza Lutfi replied 19 years, 1 month ago 5 Members · 10 Replies
  • 10 Replies
  • Chris Smith

    April 9, 2005 at 10:21 pm

    Not quite clear. Are the objects moving because they were shot that way or are they moving because they were keyframed? If Keyframed, just copy and paste the keyframes or copy and paste the null layer with the motion and reparent the new layer to it.

    Chris Smith

  • Faza Lutfi

    April 10, 2005 at 3:22 am

    thanks for the reply..

    These are objects created and keyframed…
    The thing is they dont travel in the same path… so i cant just copy the keyframes..
    any idea??

  • Eric Steinberg

    April 10, 2005 at 9:11 am

    Well, this might not be the most elegant way to do it, but it will work if I have understood correctly your specific situation:

    Copy your position keyframes from the first object.
    Create a new temporary layer and create a mask (just one maskpoint will do).
    Paste the position data in the mask shape property, and you’ll have a new mask which is shaped like your first objects motion path.
    Apply the stroke effect to this mask, and adjust the spacing of the stroke so you’ll have a row of dots. The smaller the dots, and the closer the dots are to each other, the more accurate your result will be, but you must be able to count the dots.
    Count the dots and write down the number. For simplicity, lets say you have 100 dots.
    Copy the position keyframes of your second object, and repeat the whole process, but instead of applying a new stroke effect, copy the previous stroke effect so your dot size and spacing will be identical.
    Count the dots in this second stroke, for simplicity lets say you now have 25 dots.
    Now you calculate the ratio of the length of the 2 paths, in this simplified example one is exactly 4 times as long as the other (100/25=4).
    Now go back to your animated objects and stretch your position keyframes in the timeline so that one needs 4 times as long to complete its motion as the other one. The speed should be the same now for the 2 objects. You can get rid of the temporary layers now.
    Basically you calculate the ratio between the 2 motion path lengths, and use that ratio to apply the time needed for the objects to complete their path.
    Hope this will work for your situation. Like I said, it’s not an elegant way to do it, but it’ll work! Maybe someone has an easier way..

    Kind regards,

  • Hans Van vliet

    April 10, 2005 at 12:15 pm

    I don’t know how your animating the 2 objects but I would create a null then link both of them to it, Then move the NULL for the Y movement (or the X) and then move the individual layers on the X (or Y). They would be moving at the same speed on one of the axis then you could move them around on the other to change the paths a little. Again, I don’t know what the effect looks like but that’s my best guess for something that has to move at the same speed but have a different path.

    The other thing is you can copy and paste the paths onto both objects. Select all the position keyframes of one of the objects. Make sure your on a keyframe (frame 1 should do) and then go up to the comp window and you’ll see the keyframes selected and there movment Dotted, then you just select one and drag and move … it would be like moving it around. Then you could make adjustments where you see fit to shake them up a little .. I don’t know what your trying to achieve so hope it works out ..

    Good luck.


  • Faza Lutfi

    April 10, 2005 at 1:56 pm

    HMMm this seems to be such long process.. i was thikning that there might be a simpley solution to just make two objects to move in the same speed.. maybe i am not explaing correctly…
    here is a link.. its a flash site so i have to give you the path.. go to the current work> then press the first button that appear (the guy sitting)… this is an installation that i am doing.. there are four videos that you see there.. each video will be back projected on to a cube and the viewer will be inside to view it.. the video that you see scrolling on the wall will move from one wall the other… now my problem is when it moves from one wall to the other (one screen to the other) it should have the same speed inorder for it to match perfectly or else one willl move too fast while the oter one is still on screen one…
    as of now there are almost at the right speed when projected but even a one second delay makes a little gap between one screen to the next.. i hope this makes it clear… i really need to get this done for my end of semester.. and i have done all the videos and only found this out when we did the test runs and have few days left before the show goes on on… i would really appreciate if someone could give me a simple soultion..

  • Paul Carlin

    April 11, 2005 at 12:32 am

    This is just another explanation of what Hans said…

    1) Copy all the keyframes into the second comp.
    2) Select ALL the keyframes by clicking the name of the property. For example, click the word “Position”
    3) Be sure you are positioned over ONE of the keyframes.
    3) Nudge the layer into position using the keyboard (arrows and Shift-arrows)

    This should change all the keyframes at once… keeping the speed of movement.

    And just for the fun of it, you can use expressions. I don’t think you have time for that one.

  • Hans Van vliet

    April 11, 2005 at 5:00 am


    I watched it all and I get what your trying to do now. 4 different projectors, and something scolling through them all. Seriously, this is what I would do. Make an animation that was four screens long instead of doing them as one screens. So your native res would have been 3072×576 (square pixles PAL) or if your working in NTSC 2880 x 540 (square pix). Then I would create a template (much like they use for cd layouts in graphic design .. showing you were each screen sits and so on). Then I would do all my animations working with the 4 screens – side by side. Now for the output. Start a new comp that would be .. 768×576 (Square PAL) or 720×540 (Square NTSC) and drop and drag the big 4 screen comp into that. And then duplicate it 3 times (making 4 projects). Name each one a different Screen number. Line them up for each comp and render them out. This way you can tweek your main 4 screen animation and all the cut up comps will update .. and so on.

    Um, if you need a template for this, let me know I can set it up for you I don’t mind at all.. Just let me know what format your working in .. NTSC (non-square) so on .. but give it a crack 1st 😀
    Thanks for the webpage that really helped what you were trying todo, hope this all makes sense. Hope it doesnt’ sound to harsh 😛 but have fun, hope it all works out.


  • Faza Lutfi

    April 11, 2005 at 7:08 am

    Thanks hunz..
    really appreciate your feedback.. and thanks to all for their comments..
    Hunz.. i will do that for my next project i just dont have time to redo work,., its really a lot of keyframming and its not just this video there are severl other videos that gets looped… so i cant change now.. but your solution is the best one so far.. thanks..
    what i will do is.. take them to fcp and than change speed until its near perfect ofcourse this will change the speed of the overlaid clips but thats my last solution in such tight times.. thank you u all..

    i just cant belive a soft like AE does not have a way to copy speed to objects and its adjust the key frames for you..

    thanks to all

  • Hans Van vliet

    April 11, 2005 at 8:51 am


    Sorry it’s not going to work out 🙁 that just sucks. As for the speed thing, AE does do things at a constant speed but you have too calculate it all. When you move something from Postion .. 0,0 to 100,0 over 100 frames it moves 1 px every frame so if you apply that to everything it’ll all move the same. It just involves alot of calculations.

    when I was walking home I remembered I forgot to tell you how to put this on a loop so on the 4 screen method I sent you, you can have the footage always moving around the cube. When you set it up again, just post here and I can walk you through it. sounds like a fun project, hope it all works out and sorry it’s been so difficult.


  • Faza Lutfi

    April 11, 2005 at 1:53 pm

    will do..
    and thank you.. really appreciate it

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