BVH Frame Rate

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BVH animations for Second Life can have any frame rate you desire. It's important to understand that the FPS (frames per second) of a BVH file only indicates how often a motion is sampled, not the number of images that will be shown when they are played.

The advantage of using a low frame rate is smaller animation files, which means they transfer to other viewers faster. You need not worry that the animation will appear choppy. The viewer will smoothly interpolate between the keyframes on computers with a display FPS higher than the FPS of your animation.

The advantage of using a high frame rate is more detail can be recorded. Second Life lossily compresses animations by dropping keyframes that did not change much from the previous retained keyframe. That means this advantage will only apply to animations with lots of rapid, significant, movement. It won't help preserve subtle movements.

It's usually best to start with a low frame rate and work your way up if you find too much detail is being lost.

The following is a table of interesting frame rates.

Frame Rate Advantages
12 factors: 2, 3, 4, and 6; factor of: 60
15 factors: 3 and 5; factor of: 30, 45, and 60
45 maximum physics frame rate

A frame rate with many factors is desirable. It is also desirable that the frame rate be a factor of numbers you often need to divide. In our case, those numbers would be 30 which is the length limit in seconds on animations for Second Life, 45 which is the maximum useful frame rate, and 60 because there are 60 seconds in a minute and 60 minutes in a hour. This makes it easy to place keyframes such that the time is evenly divided, which is something animators often need to do.

There's no point in using a frame rate above 45 FPS. Nothing else in the simulator will be moving faster than 45 FPS. The lossy compression is almost certain to remove any additional keyframes above this rate of sampling.