Hi Todd,
Sorry for the confusion on keyframing the Pre-roll. I was thinking about 2 different ideas and ended up combining them.
There are two ways to get the Flag to go from a still image to a waving flag. The first way is to change the Pre-roll value to 0. This will keep the Flag as a still image, then start waving as soon as it hits time 0.
The second approach is to keyframe the Wind Speed and Gravity. For example, if you want the Flag to start as a still image and start waving at 3 seconds, then change the Wind Speed and Gravity to 0 and set a keyframe at 3 seconds. This will keep the Flag as a still image from 0 – 3 seconds. Then, you can set another keyframe at 4 seconds, and change the Wind Speed back to 11, and the Gravity back to 9.8. You can adjust the keyframe from 4 seconds to customize how fast the Flag changes from a still image to a waving Flag.
Hope this helps.
Best,
Edward