# Shutter Animation - Solved

Hey, I am relatively new to Bongo, and i am trying to animate a shutter with several elements, following an curve. But there are 2 problems i can’t quite catch.

Picture 1)

Picture 2)

Picture 3)

As it can be seen in the attached pictures, the first element follows the path quite nicely until it reaches the horizontal part of the curve. There it instantly changes the orientation. I solved this once by turning the horizontal path before joining it to the curve, but i can not repeat this until now. The rotation of the last part of the curve still has influence how the element does change it’s orientation (left, right, up, down), but i can’t quite grasp how the orientation of the curve is connected to the function.

I did this animation with the “simple constraint” functions, with the “to path” for the following and “look along z up” for the orientation of the curve.

Picture 4)

When this is complete, i want the other elements hinge to the first element, and to the curve, so they follow the first element on a “rail”. Here i have no idea how to get this to work. All my attempts with IK-Chains and Joints just let the other elements follow the first element as a block, and not on the rail. Do you have any hints what i am missing?

Greetings,
Boreas

example.3dm (49.3 KB)

Here is the file, if you want to see it in 3d.

A file is always illuminating. Thanks for sending.

The To Path constraint forces the object along a curve without changing its orientation. The Look Along constraint does exactly the same but moreover alters the objects orientation keeping the constraint heading vector tangent to the curve. So there is no need to have both simultaneously.

The rotational behavior of the pivot – I agree - is somewhat unpredictable. When e.g. the path-curve is parallel to the YZ-plane (example 001.3dm (48.3 KB)) no spinning occurs. As far as I know this has to do with the way the tangency is calculated. I’ll have to consult the developers to know more details.

But all this is beside the point, because the rotation of the shutter elements is determined by their mutual connection rather than by tangency to the path-curve . Indeed for your shutter-model you’ll need IK, more particular a train-unit-system. A sample of such can be found in “Simple Roller Coaster” on Bongo’s website (http://bongo.rhino3d.com/page/additional-example-models).
In example IK.3dm (76.7 KB) the shutter-elements are hierarchically linked into a chain. Their pivots are positioned as required, made a hinge and simultaneously constrained to the path-curve. An additional point is used to drive the train, by applying a Simple ToPath constraint.The constraint parameter in keyframe 99 is modified to 0.845 the prevent the shutter to slide of the track.

If any more questions after examination: shoot!

Thanks for the quick respond.
I will ask the questions as soon as i have them.
Greetings,
Boreas.

Nearly forgot to answere here. Had a little trouble getting my constraints in the correct order, after i added multiple rails and hinges which were “out” of the Shutter, but at last it all worked out fine.

Thank you for the help.

Oh, and a little Off Topic Question: How do i animate a rotation of a body around a self set axis? Somehow the “Transform”->“Rotate3d” command does not work properly, it just let me rotate with the world axis. Maybe i miss something there, too.

Nice to hear you got the shutter-project working.

About the Rotation: in the Bongo Object Properties Panel there is an option “Rotate in world space”. When it is unchecked the object will rotate along the axis of its pivot (Object space) rather along the World axis.

Oh, that is simple. Thanks a lot.