1. FPS & Time-based Animation
Reference
Fall 2013 revised

2. Frame Rate (畫面更新率)
FPS
frames per second: many how frames got displayed in a second
1/(time required for single-frame display)
For a sufficiently smooth animation, fps > 20
To measure the time a display routine takes
Use QueryPerformanceCounter (next pages)
To periodically display FPS, use glutTimerFunc()
Fall 2013 revised

3. Time a function For low-precision timing,
int glutGet (GLUT_ELAPSED_TIME)
is sufficieint [in msec]
Fall 2013 revised

4. Example
Fall 2013 revised

5. Frame-based vs. Time-based
Use these updates per frame:
Simple, but runs differently on different machines
Time-based animation
Specify linear (or angular) velocity
Motion is the same on every machine
Important for animations, games, …
Fall 2013 revised

6. Time-based Animation
Assume the angular velocity of the object is 1RPM (round-per-minute) … like the “second” hand (秒針)
Make sure the object rotates in the same speed on different machines
Angular displacement between frames
Elapsed time between display
Fall 2013 revised