Quote: --- Original message by: SlappyThePirate
No, that's not what an overlay is. Replacements are hard to explain...
I suggest search.

Quote: --- Original message by: The Cereal Killer
For a dropship coming down, use .JMW (world-relative animation).

Quote:
OK, just for the record, i'll set things straight with animation types:
First, lets run down on a little thing called frame info. You may have noticed these dx, dy, d-whatever things in the animation tag. 'd', for those of you who are familiar with calculus, means the derivative of--or the rate of change in--something, which is precisely what frame info is. It tells the game, frame by frame, how much an objects transformation is changing. dx, for instance, is the change in movement in the x direction. Similarly: dy for the y axis, and dz for the z axis. There is another called dyaw, which is the change in yaw rotation (or z rotation). Frame info provides additional data to an animation that may be useful for the engine to apply to various situations. For example dx frame info in a running animation may tell how fast a biped is moving (which is what the game uses to determine how fast an AI runs).

JMM is a base animation with no frame info data. This is ideal for FP animations as it does not cause tool to store redundant data (ie: JMA stores dx,dy frame info data, which is used for bipeds).
JMA, as mentioned previously, is a base animation with dx,dy frame info. It is ideal for running/walking animations in bipeds, as it tracks x (forward/backward) and y (left/right) movement data.
JMT is a base animation with dx,dy,dyaw frame info. This is used in turning animations for bipeds, where frame data is needed to track yaw (z axis) rotation. Much like how dx,dy frame info allows the game to determine how fast an AI moves, dyaw allows the game to determine how much the biped turns, along with the dx,dy frame info that JMA provides (hence dx,dy,dyaw).
JMZ is a base animation with dx,dy,dz,dyaw frame info, it provides everything a JMT animation does, but with the addition of dz frame info, which obviously is movement on the z axis.
JMO is an overlay animation. Aptly named, these animations 'overlay' themselves onto base animations or otherwise. Rather than animating the object with absolute transformations, they use relative transformations to modify an animation already playing. An example of an overlay animation is the first person moving animation. Rather than wasting time animating 'moving' variants of the reload, ready, fire, idle, etc. animations, a simple moving overlay animation is used to simulate the "sway" of the gun, regardless of what animation is playing.
JMR is a replacement animation. These animations are more like base animations than anything, but with a few differences. In a base animation, even if some nodes are left unanimated (still throughout the entire animation), in the final product ingame, they will appear as "still" throughout the entire animation. Replacement animations, on the other hand, ignore unanimated nodes. This is useful in many cases, for example: If a reload animation for a biped (tp, not fp) was made to be a base animation, many variants of it would have to be made: reloading while still, reloading while moving forward/backward/left/right, reloading while crouching, the list goes on... With a replacement animation, one can just animate the upper body movement (spine, arms and what have you) and leave the lower body still. This allows the game to play the base animation of running, crouching etc for the lower body and play the reload animation on the upper body. Much more efficient.
JMW is a world relative animation. This is useful for cinematic animations (read: NOT recorded animations, thats a whole other subject). World relative animations are played relative to... well... the world (ie: the origin [0,0,0] point of the level). This allows the animator to animate, say, a pelican directly on the level geometry and have it work flawlessly ingame.