Hey, so one thing that I think would help everyone looking to develop a game reel is to give some basic frame lengths for game animation. For example, one thing I've seen is that your basic attack usually takes anywhere between 5-7f with antic included. If others can give basic frame ranges for an idle, heavy attack, 2 combo attack, 3 combo attack, etc. I noticed that many critiques when it comes to people doing game animations are that they don't work in the engine, due what gamers would consider 'lag' or unresponsiveness even though the animations are amazing. Many games I've noticed cheat this quick motion by overselling the settle animation during the end of the frames.
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Some focus a lot on you knowing body mechanics, interesting poses and character. Other look for someone that technically understands how game animation works and understand the timing of game animation. It might even depend on the type of game the studio is making. The sad thing about that is that it often game animations take away from your overall result and polish, to be more functional, which isn't always the most impressive. Nothing really limits you when animating yourself so you shouldn't handicap yourself too much. Setting a basic frame range for animation, should be a limit you set yourself according to what you want to showcase.
Game timing may also vary a lot. An enemy shouldn't always be responsive, but often telegraph their attacks well so they are readable and they can react.
A good Game Reel i think if you focus on game animation you should have a good amount of animations that are based on something that could be launched right into a game showing you understand it. It should also have more cinematic pieces that catches the viewers attention and tell a story. People remember storytelling, and flashy fun stuff more than regular moves, so taking away that element completely from a reel might hurt you aswell.
Now i don't really follow this as much as i want to but ideally i think it should end up that way.
What seems consistent is not absolute duration but arc sweep per frame, which is around 60~90 degrees per frame.
If you're aiming for specific studios, find their senior and lead's animation reels and study their style.