# Rocking horse

Hi all,

I have modeled a rocking horse. How can I make it move easily ?
This is not just a rotation. It is a mix between rotation and translation.
But it is hard to synchronise both types of movement.
Is there a may to do it easily ?
I have the same question to make a ball roll on the floor. It’s not easy to synchronise translations and rotations movements. Especialy when the ball follows a track wich is not a straight line.

Best animations

Nicolas

for the ball on a path you could probably use the NLA walkcycle features…
[so, you’d have a bone which deforms the ball, and you’d put the armature on the path and use the NLA window and stuff to make it rotate right]

unfortunately this isn’t covered by many tutorials

http://www.blender.org/modules/documentation/htmlI/x7612.html

for the chair, the same ought to be possible [and you’d use a time ipo to move back/forth on the path], but there is probably another way which isn’t as weird

it looks like you can get reasonable results for a rocking chair by animating its location and using a lock[ed] track constraint tracking towards an empty directly under that object, locked around the axis which it rotates…

It seems I’ll have to continue learning Blender. I’m new to Blender and I admit I don’t have enough knowledge to understand what you explained in your answer.
I’ll read it again when I have finished Blender book.
Thanks again.

Nicolas

Nico04,

It is a mix between rotation and translation.
But it is hard to synchronise both types of movement.
is correct. But it can be easily visualized geometrically. I’ll try to put an image in here that may help you see the geometry involved.

Its the radius of your rocker arcs that’s the key. You must move the center of this arc (or the whole rocking horse, in your case) the same distance as this arc radius for every 90 deg. of rotation.

Another way to look at it is, you always want to keep the centerpoint of the rocker arc directly above where it contacts the “floor”.

Probably, you don’t want it to rock as much as the illustration shows, so start by dividing it by half. In the example, if you move the rocking horse 1 inch, and rotate it 45 deg. then you’ll have the same effect. If this is too much, try 3rds (or 30 deg. & .6666 of an inch.)

Simply match the keyframes for your translation and rotation keys. You’ll also want to match the interpolation type and amount of your IPO curves.

Hope this helps more than confuses.

You are right. With a bit of geometry I can easily find the amount of translation for an angle of rotation.
But it is still a manual synchronisation of the two types of movement.