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I´m trying to rotate an array of objects along a curve, using a empty object in the middle that can be rotated. Using a curve-modifier I'm able to rotate the objects as the green arrows show. But I would like to just rotate the empty (red arrow) to get the same result or maybe I should use a bone?

Pulling the empty sideways rotates the objects

Is there a way to still be able to rotate the objects after pressing apply on the curve-modifier?

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  • $\begingroup$ As far as I can tell, once you apply the curve modifier, you're stuck with solid mesh, curved around as applied. You can however apply the array modifier. So long as the curve is still active as a mod'r, the plates can be rotated around it. See the ans I've placed below to achieve independent rotation around the curve without forward motion and similarly, steerage and motion of the assembly without rotation around the curve. $\endgroup$ – Edgel3D Sep 5 '18 at 0:42
  • $\begingroup$ Adding to the above - it is possible after applying both modifiers to animate the meshed plates around the curve by cycling about 5 animated steps "captured" before applying the curve, then switching each frozen model in and out, much like a movie film. It works quite well but is not for the faint hearted. I have a blend file where I had to do this in the past. You can have that if you wish. The explanation would be packed with it and trust me, would take some reading! There a two methods, the second somewhat easier but texturing a curved singular 'belt' with a video of rotating plates. $\endgroup$ – Edgel3D Sep 5 '18 at 0:59
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If you want to use the empty as a kind of control object, you could parent the object(s) being deformed to the empty using Ctrl-P and the objects would move around the curve when the empty was moved.

enter image description here

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  • $\begingroup$ Thank you, but is there a way to rotate the empty instead to do the same thing? In other words: having the empty in the same spot all the time but still be able to rotate the objects. $\endgroup$ – Astolbon Sep 2 '18 at 12:21
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Objective - Rotate meshed Caterpillar Tracks around it's curve without forward motion -

Add an empty at the same origin point as the curve and parent both the curve and the plates to this.

The empty can be dragged around without the plates rotating. To rotate the plates at will, drag their origin point in the said axis. (x?)

By keyframing both, independent rotation, location, and steerage of the track assembly is possible.

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That's easily possible with drivers:

enter image description here

My scene is a former cube with an Array Modifier for the treads and a Curve Modifier on top of it.

The Empty and the treads are parented to the curve. If I move the treads in x, they go around the curve. The treads have a single purple driver added by right clicking the x location.

enter image description here

That driver shows up in the Graph Editor >> Drivers >> N >> Drivers if the treads are selected. Pretty deeply hidden actually.

I created a variable called gumball. Of course you can pick a more confusing name if you like. The object is the Empty, the value we borrow is the Z-rotation in my case. Test which axis will do the trick for you. I use local space and have everything parented to the curve, so I can rotate the rig without distorting anything.

If you get a little warning sign, you might need to enable python in the file tab of the User Preferences.

In the Expr. field above, just use the name from the variable and stuff should move around when you rotate the Empty.

If you want to synchronize it:

-gumball switches direction

The multiplier changes speed. My curve has a diameter of 2.849 * pi resulting in a circumference of 8.95 Blender Units.

One rotation of the Empty in radians is 2 * pi = 6.283

8.950 / 6.283 means I have to multiply with 1.4245 in order for the rotation to match.

If you have a different curve (my circle is just laziness), just pick the diameter that suits you. Either one of the wheels or the height of the curve.

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