# OpenGL Advise on animating a model

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If you want to animate a character you surely should use bones.

Given a model and a set of bones you first transform the bones into 4x4 matrices. To create the proper hierarchy you multiply each bone by it's parents inverse matrices. Then calculate the position of the vertices relative to the bones (by applying the matrix's inverse to the vertices). Usually each vertex is assined to one bone (one matrix).
Then, for each frame, you determine the current time of the animation. If the time e.g. is 3.4 you will have to create a new set of matrices by using 0.4 of animation-frame 4 and (1-0.4) of frame 3. You then apply this set to the vertices and you will get an animation with interpolation.

I think there are better ways to implement this, quaternions should do better interpolation, and maybe are faster, but this is the way I did it some time ago.
Unfortunatly it does not seem that I used any docs for this, so there is nothing I can recommend.

The other thing you mentioned, storing vertex positions for every frame, might be an option where bones cannot be used. It could be usefull for facial animation, as it would need far to many bones to animate it. Also Vertex Keys (?) give you more freedom in designing your model. I didn't program this, so I cannot recommend any sides for this either.

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Real Soon Now - Skeletal animation tutorial

That should be a good place to start ;)
It's a little complicated at the beginning and it's not especific to 3ds max model format but a bit of work should put things in place.

Then you should take a look at 'SLERP interpolation' for the frames in-between (just google for it or search the forums)

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Thanks, ill take a look at that.

Looks likes bones are the way to go.

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