Ok. Here is my RD nemisis. This applies to Carrara also.
Sounds simple, but it is not. Using the Freeform Modeler,
how can one animate a tube precisely through a seperate compound curved tube. This is a compound a snaking motion.
The fit must be precise. The length of the inner tube must essentially remain constant.
The turns must not get out of slither. Each section must take the place of the one that precedes it.

I have done alot of faking with passable, but not perfect results.

Typically I use a cylindrical freeform with as many sections
as there are curves. The problem is with getting the sections to advance sequentially and consistently through each curve .Ideas?

Could you use BoneBender, the bones plug-in for RDS ? It should help to make this kind of motion . litst

Good idea. I would like to look into it. Where does one find BoneBender?

I had this same problem last year. I ended up using a spline cylinder, not compounded, (though I guess I would have had the same results if it were,) and I frame-by-frame adjusted the models, looking at the scene preview as I went to make sure the alignment was correct. It was TOUGH, and the final result was... passable at best. If you would like to see my final render, it is @: http://www.bluetones-productions.com/gallery/MagnaTube.mpg Good luck with your project! I also included a frame from the animation showing where one tube (in black) is sliding inside the other (in white.)

Oops! the graphic didn't upload. Here it is again. (I hope.)

Thank you for the info. Unfortunately, your demo is giving me a "no url on this server" message for that mpg. I also, as a last resort had to try the frame by frame method, but, as I had to render out at a high frame rate, this proved impossible. My final method involved using individual cloaked sections for most of the curves. Still inadequate.

My piece was @ 29.97 for 28 seconds. How long is yours? ;> Seriously, it was a drag having to do it, but I couldn't find a way around it. I just checked on the link and it turns out that when I copied and pasted it, some little piece of software decided I didn't want the ".MPG" instead it put in ".mpg". Now wasn't THAT helpful?! Anyway, I changed the extention on the web-site, so try it again if you'd like.