Broken tank tread Action in Chor

[A:M Dave]

Does someone have an idea regarding what is happening here? Here are the evidence and facts in the mystery...

 

Three attached files tell the story:

1. Really Broken.prj --- Look in Chor and you should see just the red plate go around and the others moving but v-e-r-y s-l-o-w-l-y.

 

2. Working Action.prj --- This Chor does what it should: all plates go around the path of the tread.

 

3. Good and Bad Action.wmv --- Knowing how demos go, here's a video showing what I got.

 

The catches:

The project with the broken Chor was working at one time (even after multiple opens and closes)

Both Chor's in both project files were built in an identical fashion.

Looking at the motion in the Action works in both files.

 

Any ideas anyone?

 

...or...

 

A more elegant (and robust) way to do this? Following are the things I've tried or thought of:

a) Single spline with many plates distributed around with Ease. Problem: Ease greater than 100% is not allowed.

 

Chaining all the plates to a lead plate (like a train engine with cars). The lead plate is Constrained to the spline. The others are "managed" into positions with kinematic links. Problem: OK in theory. Very messy in reality. Managing plates ends up being every frame keyframe ordeal and even then is problematic.

 

c) Thought about making it all round then using some sort of deformation. Problem: I don't want the plates to change shape (squash / stretch).

 

d) Animate an image over the top of a band. Problem: This would be cheating and the results would look too phony.

[attachmentid=12433][attachmentid=12434]

Good_and_Bad_Action.wmv

Broken_and_Working_Project_Files.zip

[luckbat]

A more elegant (and robust) way to do this?

Have you seen Dhartman's bicycle chain project? I believe he uses a repeating action with stride length...

[A:M Dave]

Thanks for the reference. I had not seen that yet.

 

Dhartman's approach is very similar to the one I was trying. I think he ran into the same problem I did trying to get the lead elements not to bunch up at the end of the path at 100% ease.

 

I used separate, connected spline loops. He used a slick trick of an open-ended double loop. My elements' ease goes 0% - 100%; his 0 - 50% (for the 1st element). (If I had a trick, it was getting the copies of a spline to shift their first control point to different nodes.)

 

I'm going to try his construction to see if that holds up.

 

What I don't understand is why my action is breaking down in the Chor. Either of these modeling approaches should work just as well.

 

Does my "broken action" work on anyone else's machine?

[A:M Dave]

I think I found the problem.

 

In Action, I only explicitly set the Ease on the first path thinking that once the length of the Action was established, other path constraints would "assume" the length by default.

 

Not so.

 

Once I explicitly set the others, they worked in the Chor also.

 

Now on to the next challenge, that of getting left and right turns to work well. I've got one scheme, but am going to try something else. I'll let you know how it works out.