Select PlaneShift->Export Sprite.we have 2 ways to export our chars an old one and a new one the old one just takes a number of mseconds and use this info to switch from one frame to the other so it renders the first frame, then wait 100 msec, then second frame, then 100 msec...etcc the problem of that method is that the number of frames in the animation makes the difference on the speed of the char also if a char has short legs or long legs if doesn't make difference so we have the new method to fix that.
"vertex on foot" is one vertex that moves with the character. those vertexes will be used to calculate displacement from one frame to the other, so it can be one random vertex of the foot. We choosed the outermost one to the back of the foot. so you provide 2 vertexes, one for each feet and it calculates the real movement of the vertex the "displacement" of the vertex based on that it moves the char in game. first foot on air is "foot 1" "frame with foot 2 on the ground" is the first frame where the second foot touches the ground from that point on, the displacement is calculated on vertex 2 and not on vertex 1