I've only used mesh animation in DirectX9 but I havent really understood who do animation works... So, Ive heard about keyframe animation, bones animation and animation blending... Can someone explain me this concepts and how are they integrated in 3d file formats like collada?

There are several jobs:

* Modelers
* Animators
* Texture artists
* Scripting


Modelers build the 3D mesh. The mesh includes information about how the model should move. These are called "bones". Bones connect to each other in "joints". The process of adding this to the model is called "rigging" or "skinning". The modelers build a model that can be moved in a realistic manner.

Animators are given the models and create animations. Animations are usually very short. An animation is made up of key frames. They start in some pose at frame 0. The animator moves the arms and legs to a new position and saves it as frame 20. When the animation is played, the model moves smoothly over those 20 frames from the first position to the second. There may be an animation of starting to walk, another animation of taking a step, and a third animation to stop walking.

Collada includes several sections. Some of those sections are <geometry> that stores the model, <controller> that stores the bones, joints, and skinning formulas, and <animation> that stores short animations.


You need scripts that tell you how exactly how the animations fit together. For example, you might have a script with
* Start walk
* Walk animation
* * Loop until done
* Stop walk
For variety you will have several walk animations to pick from.


Once the artists have built it, you need to get it in game.

You will need code that plays the animation. Usually you want an engine that does this for you. It involves a lot of math, and is easy to get wrong. After loading the models, animations, and scripts, you tell the engine that you want a specific model to play an animation. Your scripts tell you when to change animations.

With all that in place, the code gets to move the model around. When it starts moving it notifies the script system, which begins the walking animation, then the script automatically moves into the walk animation. When you are ready to stop moving you notify the script system, which begins the stop walk animation.


Animation blending means playing back more than one animation at once. You might want the head to move as your character is running, but you also want to look at something as you run by. Maybe you want to have then run animation and also swing a sword.


It is a lot of work but the effect is compelling. It is something that gamers demand to see, but they don't realize the work involved.

Thanks for both of you. =]