Perfect circular path?


https://forum.reallusion.com/Topic350244.aspx
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By FLG4EVR - 9 Years Ago
Hi All,

Brand new to CTA3 here. I'll got a project where I need an object to move in a perfect circle (nothing fancy - path is only in the x-y plane). Imagine the center of my composition is the earth and I want to have the moon orbiting around the earth. Even if I create a transform path with the key frames connected with "curve" path, it doesn't make a perfect circle. It's as if I need to tweak the belzier curves of the keyframes, but I can't see that that is possible. Any tricks on how to make a prefect circular path for a prop?

Thanks,
Jeff
By kylelee - 9 Years Ago
Regarding circle path, you should adjust prop pivot to make it.
This is my Test Project.
You can refer to make it.
Download Link: https://www.dropbox.com/s/5id6riiopfkk98h/Test.ctProject?dl=0

https://forum.reallusion.com/uploads/images/dd75290b-1f20-494c-bbb1-563d.gif
By FLG4EVR - 9 Years Ago
Wow! That's awesome Kyle. I am looking at the file and trying to deconstruct how you did that. (I was trying to employ paths, but your solution looks a lot more elegant and concise). Thanks so much... and I may have to reply back if I can't figure it out how you did it!
By hyteckit - 9 Years Ago
I would love to know how this is done too.
By FLG4EVR - 9 Years Ago
Thanks again for the example Kyle. I've had a chance to take a long look at the file, but I think I'm stuck. Here are the salient points to my understanding/misunderstanding:
1. I can see in Composer Mode that you can reassign the Pivot point of rotation for a prop to one of 8 points along the bounds of the prop (corners or sides) or the center of the prop (default).
2. When I enter Composer Mode, the only prop displayed (or listed in the Scene Manager window) is the Sun. How do I visualize the Earth or Moon in the Composer Mode?
3. I am assuming that the Pivot point for the Earth is reassigned to the location of the center of the Sun. Given what I stated in List Item #1, how do you assign the Pivot point to a location far away from the bounds of the prop?
4. I further assume that the Pivot point for the Moon is reassigned to the center of the Earth. How do you assigned the Pivot point of a prop to the location of a "parent" prop?
5. Lastly, if I select the Sun in Stage Mode and step frame-by-frame through the animation the bounding selection square of the Sun enlarges and then shrinks back multiple times during the course of the animation. Is that important? (The same thing happens with the Earth and Moon selection squares when they are selected)

Thanks for your insight,
Jeff
By kylelee - 9 Years Ago
Let me explain,
There are three props in the scene.

https://forum.reallusion.com/uploads/images/1b805207-dcd8-4a34-bf9b-c862.png

Regarding the Sun prop, you can open the Timeline and open the prop Key Editor, I just set two keyframes with Transform rotate.

https://forum.reallusion.com/uploads/images/af0e2923-2e7b-4306-839c-c1d8.png

Regarding the Earth prop,  there is a multi-sprite prop, you can open the Sprite Editor in Composer Mode, you will see other sprites.
And I reset the object pivot, set the initial position y is -2000. When you back to Stage Mode you can see the prop position have reset.

 https://forum.reallusion.com/uploads/images/7e98d2f0-751c-4cfb-8148-6fdd.png

Back to Stage, you can open the Timeline and open the Prop Key Editor. I adjust the two tracks object Transform track and sub prop Transform track.
The object Transform track is adjusting the whole object.
The sub prop Transform track is adjusting the sprite.
Therefore, you can see the figure, I set the Transform track let Earth prop rotate base on object pivot and set sub prop Transform track let Earth prop rotate base no sub-object pivot.

https://forum.reallusion.com/uploads/images/9133314b-5f92-4c47-9b02-8d5f.png

https://forum.reallusion.com/uploads/images/5502b8d8-0e94-428b-9870-a3a7.png

Another Moon props let everyone to think about. If everyone was interested, I will share my step.

Hope this explanation has helped.
Thank you.

By FLG4EVR - 9 Years Ago
Wow! Truly ingenious. I read another post that you commented on about pivot points, and I'm guessing that the moon prop has to be set up in PSD to convey the parent/child nature of its pivot point. (?)

Thanks again for all your help.
Jeff