Question about the sprite sheet animation implementation in Unity.

Unity Engine
1

Hi, guys:

Currently I’m digging into Unity’s animation system and having some questions about the sprite-sheet animation, hopefully I can get some ideas from you guys here:

  1. Basically the Animation view allows you to animate a property on an object, for example, I can animate the position of an object by adding keyframes.
  2. In Dope Sheet view, you would see keyframes of the position.
  3. In Curves view, you can edit the curve to determine how to interpolate the position between keyframes.

This is pretty clear to me.

And we can find a list of animatable properties in Unity’s animation manual:
2062146--134380--upload_2015-4-9_23-2-40.png

MY QUESTION COMES TO THE SPRITE SHEET ANIMATION:
We all know how to add sprite sheet animation to the time line, you basically drag and drop images to the timeline and you get keyframes:
2062146--134381--upload_2015-4-9_23-4-28.png

What is this animated property?
New Sprite: Sprite
This is the Sprite reference in the Sprite Renderer component, which is NOT in the animatable property list above.

If we switch to the Curves view, there is NO curve you can control:
2062146--134382--upload_2015-4-9_23-6-18.png
Which is reasonable, because the animated property is a Sprite reference, which is NOT a value!

How does Unity implement this? This is really confusing, you guys can go to Youtube and you guys can see that ppl use Blend Tree to blend sprite sheet, which makes no sense to me at all.

I’m a professional game developer, I’m trying to figure how the detail implementation/idea behind the sprite sheet animation system, any ideas would be appreciated!

Thanks a lot.

2

More updates on this, I realized that the curve for 2d animation system is called PPtr curve, is there any reason why they are not visible in the Curves View?

thanks!