9.3
6 Immutable Scenes and Arbitrary-Time Sampling
Every scene operation returns a new value. A frame is calculated from the same Scene and requested time, not from the frame rendered before it. That makes scrubbing, parallel planning, and final rendering agree.
(scene-sample scene 0) (scene-sample scene 1/2) (scene-sample scene 3/2)
The frame grid used by an encoder is zero based. A duration of 2 at 30 FPS has 60 samples, at times 0 through 59/30.