人机接口与图形学(双语)11-Animation.ppt

Animation Gaoqi He Department of CS E, East China University of Science Technology Our Approach to Animation We create animated behavior just like movie projectors display a sequence of still images in rapid succession creates the illusion of continuous motion typically want 30 frames/sec, and definitely higher than 10 Given some parameterized geometric model for every frame, we calculate the correct parameter values and we draw the scene in its current state just need to figure out how to specify/control these parameters Some Overall Goals in Animation Realistic motion a special case of the overall photorealism motive Flexibility Expressiveness want to support the widest possible range of animation system that can only produce a single walking motion is boring Ease of control something impossible to control does us little good Traditional (Manual) Animation Every frame created individually by a human that’s 24 frames/second at traditional movie speeds roughly 130,000 frames for a 1.5 hour movie Traditional (Manual) Animation Over time, a general process evolved to support efficiency start with set of drawings outlining clip — storyboard senior artists sketch important frames — key frames typically occur when motion changes lower-paid artists draw the rest of the frames — in-betweens all line drawings are painted on cells generally composed in layers, hence the use of acetate background changes infrequently, so can be reused photograph finished cell-stack onto film Computer Assisted Cell Animation Cel animation has been in use for a long time (e.g., at Disney) but we can use computers to help expedite the process draw sketches with digital systems use digital paint programs for coloring can even try to automatically generate in-betweens Computer Assisted Cell Animation Computer-assisted systems are now quite common Disney makes heavy of digital drawing, painting, compositing 2-D in-betweening is hard to get right morphing a 2-D sketch doesn’t give the impression