Isn’t it possible to use both conditions and probability for transition regions? Right now my transition regions always apply, even though I have set probability to 1%.
It is possible to use a probability trigger condition in conjunction with a transition region, but it doesn’t produce the results you’re looking for.
As the reply you got on facebook suggests, the trigger conditions of a transition region without quantization are checked every frame. As a result, nearly any probability trigger condition will be met almost immediately. If you add a tempo marker to your event and add a quantization interval to the transition region, you’ll find the probability trigger condition is checked once each time the playback position reaches one of the transition region’s quantization points.
It sounds like you want a probability trigger condition that is checked exactly once each time all the other trigger conditions of a transition region are met. Unfortunately, at the time of writing (March of 2019), no such feature exists in FMOD Studio. I have added this idea to our feature/improvement tracker, so it will be discussed and potentially scheduled for development at our next roadmap meeting.