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Actually quite an easy problem, but I seem to be unable to find any solution for it.

I want to move objects along curves while moving the camera on another curve pointing at the objects; for this, I'm using a "follow path" constraint (with another "track to" constraint for the camera for the rotation) while animating the offset. Obviously, the rotation, location and speed of the objects/camera don't match up perfectly right from the start, so I'd like to manipulate the curves they're moving along on the go, or work on segments, perfecting them, then extrude the curve and move on. However, the "follow path" constraint seems to only feature a sort of "0-100%" offset, so whenever I manipulate the curve, objects move along with it, basically making it impossible to work properly. Is there any possibility to make the "follow path" constraint use a sort of "distance" offset, where extruding the curve won't affect previous segments of the curve (making the object keep its position) - like, an actual constant offset? It would be really painful/impossible having to have a perfect curve first in order to then line up camera/objects.

I appreciate any advise on how to achieve this kind of "live-tweaking" offset function.

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  • $\begingroup$ In a situation like this, I'd recommend not using a follow path constraint. Instead, you can vertex parent your camera to a vertex with a curve modifier. Then to animate the camera, you move your vertex object. That makes it easier to control distance along the curve (and to match up with rendering objects that use a curve modifier.) $\endgroup$
    – Nathan
    Sep 12 '19 at 20:59
  • $\begingroup$ Thank you for your recommendation, I just gave it a try. It seems to be a bit unhandy compared to the controls of the follow path constraint, but it gets the job done. If you'd use the content of your comment as an answer, I could mark the question as answered. $\endgroup$ Sep 13 '19 at 23:42
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Coming to this a few years later, took me a while to figure this out, and I didn't do it exactly as Nathan indicated, but close enough, and I thought I'd explain a bit more.

The idea here is that you're going to get a mesh object (like a UV Sphere) to follow the path using the Curves modifier, like in this video: https://www.youtube.com/watch?v=oHkzyH9dpv4

You need to make sure that the mesh object uses the Curves modifier properly, it had to use the Z axis as the "deform axis"

enter image description here

After that, you can use the Z location attribute to move it along a the curve enter image description here

Notice that under the Transform properties, only the Z value changes, so it works really similar to the "Follow Path" offset and can be animated and keyframed.

Next, you vertex parent your camera to the UV Sphere (I didn't do it perfectly because I'm new to using parenting properly) but it works pretty fantastically and allows me to get all the shots I want!

Now when I extrude more camera path curve, or adjust the points, the UV Sphere (and attached camera) stays right where I want it to.

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