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

Interpolation Examples

• 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 (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 Motion in Static Frame

• Showing traces • Accumulation buffer

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