set first vertex Issue on open path

[JsMotion]

 Hi all, 

to animate a trim path the other way , i'm struggling to change the first vertex on a shape layer. when i do it keeps closing my shape, which i don't want to. Any idea how to avoid this?

I know i can just reverse the way of the path but it isnt what i want because i'm linkink my thrim path to a "Trace Path" Null .

Thanks for your help  

[David Arbor]

Setting a different point as your First Vertex will probably screw up your path even if it doesn't close. I just tested switching the First Vertex on a simple S Curve path from one end to another, and while my path didn't close, it was reshaped which is a problem in itself.

What about reversing the path direction and animating the Trace Path from 100% to 0%? That should give you the result your looking for while still allowing you to Loop the Tracer, if you have that box checked.

[Anna Lander]

sometimes when I work with quite a complex path, I create it in Illustrator and copy/paste it to the shape layer. Illustrator reverts the path direction with one click and moves the first vertex to the other end of the path.

[Rick Gerard · Accepted solution]

Shape layeer paths have diretion switches.

Changing the direction changes the way trim paths and copy to a motion path responds to an open path.

You can also change the direction of trim paths by setting changing the starting values for Start and End in Trim Paths. Set both to 100% then animate Start from 100% to zero and the line draws on from the First vertex. Set both Start and End to zero and animate End from Zero to 100% and the line draws on from the last vertex.

You should have no problems at all controlling the direction of trim paths. Setting the First Vertex is not only unnecessary, if you do so on an open path you created, the path will drastically change unless it only has two points and there are no bezier handles because AE records the order that the points were added to the path. It works the same way with open mask paths. Change the first vertex, and unless the path has only two points and no bezier handles, the shape of the path will change. 

[JsMotion]

Thanks for your help! Yes i ended up reversing the keys and linking it to the start function of the trim path , and works perfectlty  fine . Just wanted to know if in general it was possible but nevermind!