How to I turn a circle into a path so a 'planet' follows it?


I am new to Blender (version 2.62) and am after help with a problem I have gotten stuck on.

I am wanting to simulate a planet orbiting the Sun. To keep it simple, I am using a UV sphere as the ‘planet’ (with no detail added at this stage) and have placed a circle at the centre of the animation. I have been trying to work out how to turn the circle into a path so that I can make the UV sphere move around the circle/path so that it looks like it is a planet orbiting a star (which I will add later).

I have been looking on the web in the Blender 2.6 on-line manual and have found written instructions on how to turn a circle into a path there. However, regardless of if I am object mode or edit mode, I can’t find part of the panel the instructions refer to.

I would really appreciate some help with this.


Paul Floyd.

If I understand your question correctly, then I don’t think you need to setup a path. If you want to rotate one object around another (in a perfect circle), then you can simply put a constraint between the “Planet” and the “Sun” then rotate the Sun, which will move the Planet around with it. This will simulate a geostationary orbit.

If you don’t want the Sun object to rotate with the constraint (a non-geostationary orbit) then instead, put an empty inside the Sun, and put the constraint between the Planet and the empty, and rotate the empty. This method is commonly used to “spin” an object in front of the camera, or rather, spin a camera around an object, for exhibition purposes.

You need to add a Curve Circle. Press shift A, select Curve and then select circle. To get the planet to move around it; select the planet, add a Follow Path constraint and animate the Offset.

How do you animate it? I’ve tried to do the same thing, but Follow Path doesn’t work in any settings. The planet is thrown somewhere far away OR if it’s in the right place it doesn’t move, only a dotted blue line shooting from the planet is following the path.

When you place any object on a path you need to clear out the previous location by pressing ALT-G. Otherwise, the two locations (path start location and object location) will be added together and the object may jump out of frame. Pressing ALT-G will place the selected object at the start of the path. Then, in the Follow Path constraint activate Fixed Position checkbox and animate the Offset between 0.0 and 1.0 (Right-Click Insert Keyframe). This value range represents 0-100% of the length of the path. Set your f-curve channel to Cyclic in the graph editor to make the path loop.

I really don’t understand the logic in that, but it works now. Also needed to set the mode linear to avoid slowing down of planet at the start and end of the path. I don’t know why follow path doesn’t primarily do what it’s supposed and why you have to use fixed position, but then again this is Blender…

I don’t know why follow path doesn’t primarily do what it’s supposed and why you have to use fixed position,

Blender can not guess what you want to do. You can control multiple objects along a single path by animating the Evaluation Time of the path itself. In a multi-object scenario (say asteroids orbiting a Sun) it might make sense to control all the objects from a single keyframe rather than activating Fixed Position for every object and then animating the Offset for each participant.

but then again this is Blender…
More than one way to accomplish a goal.

The confusion comes from the fact that simply using follow path makes the object follow the path, but the object is anywhere else than exactly on the path. I don’t know what those “offsets” are supposed to be.