2D Animation

• Sprite animation
• Sprite-like animation in pseudo-3D game
  • Doom
• Sprite-like animation in modern game
  • 2D character
  • Game effect
• Live2D

3D Animation

• DOF: degrees of freedom
  • 6 DoFs per rigid objects
• Rigid Hierarchical Animation
• Per-vertex Animation
  • Most flexible (3 DoFs per vertex)
  • Mostly implemented by Vertex Animation Texture (VAT)
  • suitable for complex morphing
  • Need massive data
  • Cloth/Fluid Vertex Animation
• Morph Target Animation
  • A variation on Per-vertex Animation
  • Use key frames with Lerp instead of sequence frames
  • Suitable for facial expression
• 3D Skinned Animation
  • Advantages
    • Need less data than per-vertex animation
    • Mesh can be animated in a natural way (like human skin)
  • Animation is continuous and smmoth at joints
• Physics-based Animation
  • Ragdoll (in GTA5)
  • Cloth and fluid simulation
  • Inverse Kinematics (IK)

Skinned Animation Implementation

• Different Spaces
  • Local Space
  • Model Space
  • World Space
• Humanoid Skeleton in Real Game
  • Normally 50-100 joints
  • May more than 300+ joints including facial joints and gameplay joints (weapon joint & mount joint, need to attach weapon to mount point)
• Root joint
  • The center of feet
  • Convenient to touch the ground
• Pelvis joint
  • The first child joint of the root joint
  • Human upper and lower body separation

Math of 3D Rotation

• 3D Orientation Math
  • Euler Angle: Yaw, Pitch, Roll angle
  • Order Dependency
  • 3D-Rotation combined by x, y, z sequentially: R = RxRyRz
• Problems of Euler Angle
  • Gimbal Lock (because of the loss of one DoF)
  • Hard to interpolate (singularity problem)
  • Difficult for rotation combination
  • Hard to rotate by certain axis
• Quaternion
  • q = a + bi + cj + dk

Animation Compression

Animation DCC