This would lose the benefit of interpolating poses in real time, which spares memory, but would be simpler to use - get the X rotation of the player from his FPS view and use that angle to pick a pose to represent him as a 3rd person character, and layer this pose with running or jumping sequences etc. so that the 3rd person character can move around while aiming in that direction.
otherPlayer.SetPose( otherPlayer.aimPoses( Int( otherPlayer.eulerX + 90.0 ) ) )
You don't need to pre-calculate the interpolated poses in programming, if you're going in this direction. You only need a 180 frame animation sequence with aim-up in the first frame as a keyframe, and aim-down as the last frame as a keyframe. You can do this in 3ds Max or Blender, which will interpolate between the two poses for each of the 180 frames, and back in your game engine you pick the frame that represents the player rotation. Just make sure that the tangents for the keyframes are set to "LINEAR," so that each frame accounts for an equal amount of change.
- "Alpha" is a possible way to name the interpolation factor; this comes from graphics programming and alpha blending. I believe "s" and "t" are also used to name this parameter.
What you use to calculate this value depends on what you're going to do with the poses. To calculate a blend factor you can use the angle of the player, or the sine function of that angle plus some offset etc.https://en.wikipedia.org/wiki/Linear_interpolation#Programming_language_support
- I don't think there's any simpler way to do this. When you can set up poses for each critical point (down, middle and up), you can position every limb like they should be, and the software will interpolate between them and make it look natural.
Doing this in code requires much more time and effort, and may not look as natural.
In any case, your own experimentation will give you more answers than what most could say here.
- I believe that you can pre-calculate the interpolated poses from aiming up all the way to aiming down as a sequence of 180 frames (one frame for each degree of front rotation).