CSCI480/582 Lecture 8 Chap.2.1 Principles of Key-framing Techniques Feb, 9, 2009

Outline Managing data with time dimension Key-framing in general Rigid Object Motion  Translation of object space coordinate Parametrization - Arc length Speed control Acceleration control - Ease-in/Ease-out

Managing data with time dimension Data in 3D scene  Vertex positions  Vertex Color/Material  Light source locations/parameters  Texture image/coordinate  Model transformations  Camera locations – view transformations Any data or OpenGL pipeline configurations can be changed along the time axis

Key-framing technique in general A certain time frames are picked out as key-frames Key-frames are defined manually which usually holds main sketches of the dynamics in the animation The rest frames in between adjacent key-frames are created automatically using interpolations

Key-framing examples Start FrameEnd FrameLinearly Interpolated Animation Start FrameEnd FrameLinearly Interpolated Animation Start FrameEnd FrameLinearly Interpolated Animation

Key-framing Applied to three typical motions Rigid-body motion  Vertex geometric properties does not change relative to the object coordinate space  Motion can be described as a function of ModelView matrix to time Object deformation  Vertex geometric properties change relative to the object coordinate space Non-geometric motion  From material, color, light property, texture

Rigid Body Motion Xw Zw Yw Object Space World Space Geometric transformations of the object coordinate system in the world space define rigid body motion Further decompose the object coordinate transformations into  Translation: a point moving in a 3D world space  Rotation: vector orientations in a 3D world space

Rigid Body Motion – Parametrization by Arc Length along a curve Arc length refers to the length of the curve from a point P(u1) to another point P(u2)‏ Speed control by  Arc-length relative to time Acceleration: Ease-in / Ease-out for natural motion 1D: 3D: