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Computer Graphics: Programming, Problem Solving, and Visual Communication. Steve Cunningham California State University Stanislaus and Grinnell College PowerPoint Instructor’s Resource. Dynamics and Animation. Using motion effectively in your work. An Animation Is….
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Computer Graphics:Programming, Problem Solving, and Visual Communication Steve Cunningham California State University Stanislaus and Grinnell College PowerPoint Instructor’s Resource
Dynamics and Animation Using motion effectively in your work
An Animation Is… • A sequence of individual images that are presented over time • The images can either be • computed separately and assembled into the sequence later, or • computed in sequence and displayed as they are computed (real-time animation) • The choice depends mostly on how complex the images are and whether you want to save the sequence for re-display
An Example • Particle systems example: four frames showing progress • This sequence shows how particles move
Procedural Animation • Motion is built into the model so that objects are in different places with each display • Can be based on a meaningful parameter (such as time) or • Can just use frame-to-frame increments
Procedural Animation (2) • Changes can be built into the model through the scene graph • Any component of the scene graph can use a parameter or can be changed with each display • Transformations (e.g. rotation or translation) • Geometry (e.g. number of objects or the particular shapes used) • Appearance (e.g. color, texture, alpha) • View (e.g. eyepoint, view direction)
Procedural Animation (3) • Interpolations give us an important kind of procedural animation • Points can be moved along spline curves using a parameter t that is the spline curve parameter • These points can be eyepoints, geometry points, or can even be interpreted as directions or any other 3D value
Texture interpolation From the left-hand texture to the right-hand one Geometry interpolation From the left-hand geometry to the right-hand one Interpolation Examples
Interpolation Examples (2) • Eyepoint animation: along a spline curve with control points shown in red
Problems with Animation • Frame rates -- making the animation look smooth • Real-time animation speed can depend on the speed of the computer • If your user has a newer computer, the animation may seem too fast • Some images are so complex that real-time animation cannot be done in acceptable time
Problems with Animation (2) • Temporal aliasing -- sampling at discrete points in time • Common example is the moving spokes problem; a single frame is shown
Showing traces Accumulation buffer Showing Motion in Static Frame
Non-Real Time Animation • Computing frames individually and showing only finished frames avoids some of the problems with real-time animation • Frames can be assembled with many kinds of movie-making tools • Movie-showing software takes care of frame rates for you • Extra work is involved in assembling the movie, however, and you cannot experiment with the animation
Non-Real Time Animation (2) • There are other considerations if you want your animation to play on TV • For “normal” [non-HD] TV there are real issues with image size and the YIQ color system that will be used to transmit the picture • Look carefully at color choices and color bleeding problems