I.e. in the assets/minecraft/blocks/textures folder there are 10 textures: destroy_stage_X.png with X being 0 through 9.
When you break a block ingame, these 10 textures are layered over the block you are mining, one at a time, according to the total amount of time you have mined (depending on blocktype and tool).
For blocks like dirt that's fine, but let's say I want to mine obsidian or something else that takes some time: how do I smooth out the animation? with the destroystages updating every second or so, that looks kinda ugly.
If I could add more destroystages, or make them animated, that would solve the problem – but I have no idea how (I can't just animate each using an .mcmeta file because the frametimes would be the same, regardless of the time it would take to break the specific block, resulting in a sometimes looping/cut off animation).
I know I've seen that this is possible somewhere, but that's been like 3 years and I can't find it any longer.
Best Answer
If you are trying to do this using a resource pack, it is just un-achievable because of the simple fact that there are only 9 destroy stages in the texture pack, and those nine ones are the ones that minecraft reads, any other added ones would not be read, and might crash the game, you could maybe do this using other addons or mods, but as of vanilla minecraft, you cannot.