Just a quick little update, I'm not quiet done but very close.
I've added sneak and climb as animations to the current git source here:
Still a bit experimental and I'm refining and finishing code commenting, but enough there to try it out pretty safely.
Sneak/Crouch/Duck - Will let you sneak through a 1.5 high space but only if your moving forward and facing forwards. I'm still working on refining that. Theres another glitch but I'll see if anyone can find it, lets just say you can sneak through low spaces faster if you find it :).
Climb - Nothing special here climb up and climb down. A little bit of work to do at the tops of ladders yet in regards to ending animations a bit sooner.
Flying - You can now "fall" if you fly up and then turn flying off, you should now fall.
Falling - I've set terminal velocity (TV) to roughly 100kp/h but this will still catch load edge at times and if you have any frame of reference you will notice the stop. Clouds being a good one. Once you have fallen through the chunks once I found catching the load edge was much rarer but can still happen at 100kp/h. I have done my best to add a slight delay so you dont drop out of fall animation into stand. But you may still get the odd flicker to stand depending on how long the chunks take to load.
Falling but Superman it - If you press shift while falling this will allow you to speed up beyond TV (basically pin drop). Fastest I got to was about 600Kp/h before load edge grabbed me, but have fun. If you move around while pressing shift down you will also take on the flying animation.
Dead people bounce - Hit the ground fast enough with some lucky timing and your dead body will bounce :).
Swimming - This takes some getting used to but just before your feet touch the sand/bottom press and hold shift, you'll go into a super low swim, keep shift held down and you'll be able to swim through 1x1 tunnels.
Think they are the main points, I wont do a release until I tidy up the code a little add that ladder climb top check and adjust the tunnel swim code so if you let go of shift you dont stand up - hint try that with crouch you wont stand.
The current git code may not play nice with other mods that adjust player speed but you may find all goes fine. But I will add support for a few of the monoidy type mods later.
Edit: Forgot to say any issues just let me know Ill try and fix them, I should probably caution Im starting to hit some limitations in what I can and can't detect the player is doing. Flying/Falling split was quiet tough as theres no feedback when flying is on vs off just if the Priv exists, Duck/Crouch has its own little special catches and allowing swimming through 1x1 holes hit the entity box's dont rotate issue.....anyways let me know if I can fix it I will :)