1. Software Engineering and Game Development
Lecture Skeletal animation
Software Engineering and Game Development
Elias Holmlid

2. Today’s plan First, going to finish off what we did yesterday
Then... animation
Keyframed animation
Skeletal animation
Elias Holmlid

3. Key framed animation
Also called per-vertex animation or morph-target animation
Define a few frames, then fill in the blanks (tweening)
Elias Holmlid

4. Key framed animation on meshes
Static mesh model for each frame
Only the key frames are exported
Good for facial animation
Used in Quake II and Quake III for example
Elias Holmlid

5. Skeletal animation A hierarchical set of bones
Possible to blend different animations together (smooth run->idle for example)
Elias Holmlid

6. Skeletal animation
Each frame, we can represent the transform for each bone as a matrix
This is called a matrix palette, i.e. an array of matrices
Elias Holmlid

7. Skeletal animation Vertex blending
Each vertex in the mesh can be influenced by several bones
Final position of vertices calculated as a weighted average of the influencing bones
Thus, smooth transitions can be achieved at joints
Usually, four bones / vertex is enough
Each vertex contains blend indices and blend weights.
Elias Holmlid

8. Skeletal animation
Only bones...
Elias Holmlid

9. Skeletal animation
Skinned bones...
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10. Inverse kinematics
Find out how to rotate bones in order to end up at a desired position
Elias Holmlid

11. Ragdoll physics Often used in death animations
Place constraints on how the skeleton’s bones can move in relation to each other
Then use physical simulation on bones
Elias Holmlid

12. Ragdoll Physics http://www.youtube.com/watch?v=gbuA-HEbROk
Elias Holmlid

13. Skeletal animation in XNA
.X and .FBX formats support skeletal animation
.FBX concatenates all tracks into a single timeline
.X supports more than one track
I’ve had most luck using the kW X-port plugin for 3D-studio (
Elias Holmlid

14. Skeletal animation in XNA
Content pipeline needs to be extended
Elias Holmlid

15. What has to be implemented?
Animated Model Processor
ContentTypeWriter
ContentTypeReader
Classes for storing the data during runtime
Compiled as a library
Keyframe (stores a keyframe for one bone)
AnimationData (stores one animation)
AnimatedModelData (stores skeleton+all animations)
Skinned Effect
Elias Holmlid