Train Rig, path constraint indipendent to percentage

[Cab00sE]

Hi I am currently trying to rig a train and need help/suggestions. The ideal solution as far as I can see would be to use a path constraint where as the path is the track (the track is constructed out of a spline and a shape and a sweep so the path is already there). However I want the setup to be flexible so I can modify the path or track on the go, But here is the problem, each train car has 2 axles, one at each end of the train carriage. These axles must maintain the same distance apart at all times, the predefined length of the carriage. So here is the problem if I change the path shape the length of the path changes so the origanal percentage values used on the path constraint for the train carriage are no longer corect as the two points have become further apart or closer together depending on if the path has grown in length or shrucken.

Is there a way to have the points constrained to the path but also not move in world XYZ if the path needs to be updated??

[libertycityanimation]

If you use link the parent to the child, example the parent is the trains track and the child is the carriage(s) so if you use this method then your train should stay on the tracks as you move the line. But if you keep moving the line then the carriage(s) will keep coming off the track. So I would make the train tracks first then animate your train moving along tracks

LCA

[Cab00sE]

libertycityanimation that doesn't really address the problem, the points will move with the path anyway as they are constrained to the path via path constraint. What I need is a solution where i can re shape the path as need be but not have the points sliding around. Thanks anyway.

[libertycityanimation]

I don't have time really to tell you how to do that because I have work for clients to do

As i said above if you model the thing first use the parent to child association so the parent will link to the child when you animate the parent the child (children) will follow Your making it too hard for yourself if you take the simper root around you will find it a lot easier. i have made enough trains and tracks in the past 5 years with this method My train always stay on the tracks and i don't have any complants from my clients.

unless i can see the animation i cannot help you if you want to learn animation then i would go and watch one of the animation title that DT has........

[Littletoon-fr]

I had the same problem not long ago, and I found the solution thanks to IK solver. (2 bones on a spline constraint with ik solver) : ]