Just tested seems to working!
I'll merge this now, just have couple of cosmetic suggestions.
Maybe worth to create 'Enable' checkbox for sequence rendering, and get rid of 'Start Sequence' button. So if it's checked Start/Refresh button will run a sequence instead of IPR.
Rename 'start', 'end', 'step' to 'Start frame', 'End frame', 'By frame' to match other ui naming convention.
'Reset' button should reset the frame range to scene default. You can extend getSceneOption() to get frame ranges.
Add - AiFrameSequence object for stepping through a list of frames Add - qt_sleep function Add - sleep_until function Add - sequenceGroupBox to ui