Computer Animation. Computer Animation. Principles of Traditional Animation. Outline. Principles of Traditional Animation

Transcription

1 Computer Animation What is animation? Make objects change over time according to scripted actions Computer Animation What is simulation? Predict how objects change over time according to physical laws Adam Finkelstein Princeton University COS 426, Spring 2005 University of Illinois Outline Principles of animation Articulated figures Keyframe animation Angel Plate 1 Squash and stretch Slow In and out Anticipation Exaggeration Follow through and overlapping action Timing Staging Straight ahead action and pose-to-pose action Arcs Secondary action Appeal Squash and stretch Slow In and out Anticipation Exaggeration Follow through and overlapping action Timing Staging Straight ahead action and pose-to-pose action Arcs Secondary action Appeal Squash and stretch

2 Squash and stretch Slow In and out Anticipation Exaggeration Follow through and overlapping action Timing Staging Straight ahead action and pose-to-pose action Arcs Secondary action Appeal Slow In and Out Watt Figure 13.5 Squash and stretch Slow In and out Anticipation Exaggeration Follow through and overlapping action Timing Staging Straight ahead action and pose-to-pose action Arcs Secondary action Appeal Anticipation (and squash & stretch) Squash and stretch Slow In and out Anticipation Exaggeration Follow through and overlapping action Timing Staging Straight ahead action and pose-to-pose action Arcs Secondary action Appeal Example: Roadrunner Warner Brothers

3 Computer Animation Example: Luxo Jr. Animation pipeline 3D modeling Motion specification Motion simulation Shading, lighting, & rendering Postprocessing Outline Principles of animation Character poses described by set of rigid bodies connected by joints Articulated figures Keyframe animation Base Arm Hand Scene Graph Angel Plate 1 Well-suited for humanoid characters Joints provide handles for moving articulated figure Root Chest Neck Head LCollar LCollar LShld LShld Angel Figures 8.8 & 8.9 LHip RHip LKnee RKnee LAnkle RAnkle LElbow LElbow LWrist LWrist Rose et al. `96 Mike Marr, COS 426, Princeton University, 1995

4 Example: Robot Inbetweening Compute joint angles between keyframes Mihai Parparita, COS 426, Princeton University, 2003 Outline Principles of animation Define character poses at specific time steps called keyframes Articulated figures Keyframe animation Angel Plate 1 Interpolate variables describing keyframes to determine poses for character in between Inbetweening: Linear interpolation - usually not enough continuity Linear interpolation H&B Figure 16.16

5 Inbetweening: Inbetweening: Spline interpolation - maybe good enough Cubic spline interpolation - maybe good enough» May not follow physical laws H&B Figure Inbetweening: Inbetweening: Cubic spline interpolation - maybe good enough» May not follow physical laws Inverse kinematics or dynamics Example: Walk Cycle Rose et al. `96 Example: Walk Cycle Articulated figure: Hip joint orientation:

6 Example: Walk Cycle Knee joint orientation: Example: Walk Cycle Ankle joint orientation: Example: Red s Dream Challenges of Animation Temporal aliasing Motion blur () Temporal Aliasing Artifacts due to limited temporal resolution Strobing Flickering Temporal Aliasing Artifacts due to limited temporal resolution Strobing Flickering

7 Temporal Aliasing Artifacts due to limited temporal resolution Strobing Flickering Temporal Aliasing Artifacts due to limited temporal resolution Strobing Flickering Motion Blur Composite weighted images of adjacent frames Remove parts of signal under-sampled in time Summary Animation requires... Modeling Scripting Inbetweening Lighting, shading Rendering Image processing Example: Robot Example: Ice Skating Mihai Parparita, COS 426, Princeton University, 2003 (Mao Chen, Zaijin Guan, Zhiyan Liu, Xiaohu Qie, CS426, Fall98, Princeton University)