unity2d what the different between sprite sheet and sprite packer?

Question

What I mean different is inefficient when the game runs.

sprite sheet: put multiple files in one texture file, and import it to unity, I only import one texture.

sprite packer: import multiple files in unity, then use the sprite packer to pack it into one texture.

So what is the difference between them? which one is better for sprite animation?

thank you!

Answer 1

In terms of frame rate you will have little to no effect. However in terms of memory, you may see an effect because the sprite packer will be able to deal better with animations that have flexible size.

With sprite sheets, Im assuming you mean atlases that are made up of fixed sized cells. There is no problem with this approach, unless your animation varies dramatically in size, making it necessary to increase the overall cell size to cover the area of the largest animation frame. You would end up having huge amounts of 'empty' and thus wasted space. This is bad since on mobile memory will be your problem.

In general sprite sheets are ok for animations that fit into an efficient cell size, like animated characters:

With the unity sprite packer you wont have this problem, since it will 'pack' the wasted empty space together and create an optimal atlas, hence the name 'packer'.

You can see that in the documentation:

The explosion (or whatever it is) is clearly using optimal space. In a sprite sheet, you would be having to create cells the size of the largest explosion.

In terms of programming ease, using sprite packer you may have to add a bit of code to correct for the original sprite size, so the animation will run smoothly at the 'anchor point'. With sprite sheets, you avoid this by having the fixed cell size.