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Thread: Please help! Large IGUS track animation problem.

  1. #1
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    Please help! Large IGUS track animation problem.

    I am trying to animate an IGUS track (Moving track that carries cables while a application head moves back and forth) I set it all up in bones and for the most part things are fine, but I am having trouble when the track should lay back down. The track should keep a tight 180 degree turn on both peel up and lay down but I can't seem to get away with it. I tried applying gravity and it was a no go. Any thoughts out there?Click image for larger version. 

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  2. #2
    Is there video reference how this should move?
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  3. #3
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    Looks like a good reference video:

    https://www.youtube.com/watch?v=Lp7boEt9WXY

    mTp

  4. #4
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    This looks like a good application for a Spline control. Sample scene attached.

    Click image for larger version. 

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    IGUS_Track_Instances_1.mov

    The Spline was made by creating a Capsule in Modeler down the Z-axis, removing one of the rounded caps, selecting the points (in order) along the bottom edge, around the curved cap at the end and back to the edge of the removed cap and pressing CTRL-P to create a curve in Layer 2. The Traveler Box and hinge was modeled in Layer 1, putting the top center of the box at the pivot point (which will be used by the Spline). F7 was used to give the layers good names.

    Sending this to Layout, select Layer 2 (the Spline) and use Setup=>CurveToSpline to create the Spline control. Use Object Properties=>Instancer tab to add an Instancer. Double-click on the Instancer to add an Object, specifically the Traveler Box, change its visibility to Textured, and its instancer Type to Spline.

    Set the "Distribute" flag, and scroll up the number of instances until it fills the Spline well and the boxes are close enough that they share hinges. You'll notice if you look carefully that they offset a little on the curve, but except for a closeup it isn't evident. You then control where the boxes are on the track by using the Offset box in the Instancer. If it needs to be perfect, I'd put the hinge in a separate layer and also make it distributed along the Spline so each hinge instance is exactly between the boxes.

    You'll notice that when you change the Offset, the boxes correctly follow the Spline, but the first box doesn't stay in the same place as it would on a real IGUS track (where the cables enter the track). To fix this, you add a Null (I called it SplineBase), parent the Spline to that Null, and move the SplineBase null the negative amount that you give the Offset.

    To make it easy to animate, you can add another Null (I called it ControllerNull), and then use the Channel Follower modifier in the Offset=>Envelope Modifiers tab on the Z channel and specify the channel you want to use to control the track. I used the ControllerNull's Z position.

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    We want the SplineBase Null to move in the *opposite* direction as the Offset, so Channel Follower won't work. I used an Expression in the SplineBase Null's Z-position Envelope's Envelope tab:

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    So, when you move the ControllerNull along the Z axis, it both offset's the instances and moves the spline so the first instance stays in the same place. As a final control, I went into the ControllerNull's Motion Options=>Controllers and Limits=>Position tab and set the minimum and maximum Z position so the track can't be moved too far in either direction.

    What fun!
    mTp
    Attached Files Attached Files

  5. #5
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    Thank you for asking, here is the video of the machine in operation.



    Thank you for any ideas!

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    Monroe -

    Nailed it. That is what the machine does, my animation is less functional.

  7. #7
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    bullet dynamics seem to work pretty well for this sort of thing.
    bonechain.lws
    This took a few minutes to set up, and seems like it could be tweaked to provide the right sort of motion.
    I am sure a spline control rig would work pretty well too if you want slightly more "perfect" movement.

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    Monroe,

    That is it! I will apply your solution and move forward. For some reason I couldn't convince myself that spline control was an option but now that I see how you supported it with other operations, it makes sense. Thank you mTp!

  9. #9
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    Ah, OK. It looks like the IGUS track you're simulating may be made of rubber, which simplifies things. You can use the same concepts from my previous post (we cross posted), but go ahead and model the whole track with your Bone chain. Create the Spline Control using the same method as above, but rather than using an Instancer on the Spline, simply go into Scene Editor, select the first Bone, right-click and use Select all children (recursively) to select the Bone chain, get into the Motion modifiers and set their Spline Control to the Spline created above.

    You then move the rubber IGUS track along the spline using the first bone in the chain's Z position. You still need to move the Spline (via a parent object) to keep the cable feed location the same as I described above.

    mTp

  10. #10
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    ah yes there it is. I spent too long letting my post sit before posting and it was rendered obsolete!

  11. #11
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    Here you go, a sample scene in case you run into troubles implementing it in your scenario. Note that the bones created by CurveToSpline (called node(n)) can be keyframed, so to get the slight gravity dip and probably a little wobble from the track that's unsupported in the air except by its connection to the application head, its own structure and the curve, you can raise / lower or make other changes to the node(n) bones as appropriate.

    Have fun!

    mTp
    Attached Files Attached Files

  12. #12
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    mTp,

    Most fun! Thanks again. I spent the weekend working with your scenes. Very useful, very inspiring. Thanks a million!

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