RVK,NLA,Actions,IPOS
what are the differences, and in wich context should we use them?
Just to have an idea of how and when peoples use those as I find myself hard do decide wich one to use 
thx
RVK’s deform a mesh. You usually use RVK’s when you want to blend several deformations to create a total deformation. eg. one RVK to move the corner of a mouth down, another to scrunch brows, etc. You can then blend the RVK’s into a multitude of expressions.
With respect to RVK’s you use IPO’s to control how much influence each RVK has at a particular frame. The action editor with respect to RVK’s can be thought of as just another representation of the IPO curves. You can’t use the NLA editor with RVK’s but rather you copy the IPO keys where you want them to occour.
So to answer your question, you don’t choose between them. You use IPO’s to control RVK’s. The action editor is another representation of the IPO window and just gives you a different way of adjusting IPO’s while using RVK’s.
If I were you the first thing I would learn is basic keyframing and IPO curves. There is a video tute here:
www.ibiblio.org/bvidtute/
Its imperitive that you understand IPO curves first. They can be used to control so many things. Windows such as the Action editor and NLA editor are just more convenient representations of IPO’s tailored for a particular purpose. After you understand IPO curves most tutorials you find on diifferent animation techniques will be easy to understand.
GreyBeard
Well I have done a caracter and animated it but I found strange that I could only use actions on bones and make it play in the game engine but when I used first IPO’s and the IPO actuator, nothing was playing for the bones.
Anyway, now I got it
So I can create RVKs for the face (could work also with bones) and Bones actions for the gestures