Sprite Sheet Is Necessary
Recently, I tried to play animation using a series of images. It's five characters on the screen and each one is in "380x1300" resolution. Each animation of default state lasts for 4 seconds and 120 frames in total.
Things all look normal inside Unity Editor on my Macbook Pro. However, every time I build to the iPad, the animation flickers. Not untill I consulted with other developers, I started to know it's the cause of too many read-write times (I/O overhead). The solution to this situation is to lower the times through packing frames into a Sprite Sheet.
What I didn't notice in the beginning is that the recommanded maximum size of imported image for mobile games should be under 2048 (ref). When I packed all 120 frames together into a "7600x7800" sprite sheet, I found out that Unity compressed the sprites making the quality unacceptable. In the end, to fit into 2048 length I can only split it into 24 sprite sheet with 5 frames in each. Even though 24 is still a big number, I/O times reduces to 1/5 times. The last but not the least, the animation stops to flicker.
To compose sprites, I highly recommand the following online tool, which really saves my time.
