Object's coordinates are not influenced by constraint's influence?

Question

I'm trying to make a camera follow a path, starting from frame 150 and lasting 100 frames. So, I've keyed the influence parameter from 0 to 1 in the starting frame and then again from 1 to 0 on the last frame.

On frame 150, the camera is automatically aligned to the path, but its location is 0,0; only its rotation has been updated. This should't be too much of a hassle, except that it makes nearly impossible to animate a smooth transition from the previous frames onto the beginning of the path. The camera insists on returning to world origin as it is there it will start its path.

This is probably due to the constraint's influence acting upon the camera but not updating its coordinates.

What should I do if I just want the camera to, sort of, snap onto the path as it reaches it?

Answer 1

Object drived by another is always represent by it's relative coordinates. If you parent a cube to an empty and you will move with empty, cube will have also zero in coordinates.

And I don't think there is a problem to animate Camera on top of the Constraint. But if you animated influence to zero on frame 149 and one to frame 150 somthere is not to much room for transition. Sorry if I understood you wrong.

Answer 2

Substitute the cube used here for an empty and parent your camera to that. The 'empty' will also become the path object that will follow the path.

(Blend file is below)

The path constraint will move the cube to it's start at frame 1 to 150 when the path's evaluation slot is set to zero between these frames. This allows you to animate the cube beforehand without fiddling with the follow-path- constraint's influence slider. It just has to be at the path's starting location and aligned by frame 150.

The graph editor's handles can adjust the animated approach speed and path starting speed, so they match for a seamless transition when that's required.

Note that the cube should be set up to follow the path from frame 150 BEFORE doing anything else because even when not moving the cube, that constraint will still be active.

So at frame 150, once the path is working ok with the cube, keyframe the cube's location and rotation.

Once that's done you can go back to frame 1 (or whatever) and keyframe it at a different location.

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If the cube also has to leave the path after it's done it's circuit, then you're probably better off using parents (Child-of constraints) instead of animating it directly. One before and one after the path frames.

This link will explain how - How to sequence paths?