# linear vertex animation and maintaining relative distance?

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hello everyone, i'm attempting to do linear vertex animation, but i've come to the realization that direct linear animation means not maintaining proper relation between each vertex, the test example below clearly demonstrates the problem:

In short, is their a particular term i should be looking up for what i want to accomplish?

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To clarify, are you moving each vertex in a straight line to it's destination as a way of animating a rotation? Depending upon your end goal, skeletal animation with vertex skinning is popular. It enforces relationships between various things, e.g. certain lengths that must be fixed, and interpolates other vertices based upon how strongly they are associated to one or more bones.

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To clarify, are you moving each vertex in a straight line to it's destination as a way of animating a rotation? Depending upon your end goal, skeletal animation with vertex skinning is popular. It enforces relationships between various things, e.g. certain lengths that must be fixed, and interpolates other vertices based upon how strongly they are associated to one or more bones.

ah, yes, i'm doing straight line linear interpretation. I have done skeletal animation before, and i would absolutely love to in here as well, unfortunately, it's not an option, as were only able to work with .obj files, so no way to get skeletal animation from them, we are essentially loading a series of .obj's at specefic frames, and animating them.

I was hoping their might be a moderate solution to this problem, other than providing more keyframes, but i find it doubtful since my google results don't seem to turn up anything particularly useful.

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The first 'solution' that comes to mind is to record the length of each edge on your key-frames, and then after generating an interpolated frame, iterate each edge and apply a length constraint to it with the interpolated key-framed lengths in order to restore them to their intended sizes.

If you're unfamiliar with length-constraints, in advanced character physics there's an example of using them to maintain a collection of points in the shape of a ragdoll.

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