I am making a steam in Houdini with watching a tutorial.
https://www.youtube.com/watch?v=ZJT7pMCaXCs [www.youtube.com]
In this tutorial, the steam starts to create in the first frame, so actual steam is visible in the shot after 5-10 frames.
But, I want to have big amount of the steam in the first frame. How do I set the start frame of steam creation before frame 0?

Create a pre-roll by setting the Start Frame of your Dop network to a negative frame, or cache more frames at the end and use a Time Shift sop, adding an offset to its Time parameter expression ($F + 50, for instance, to move forward by 50 frames).

thank you! I didn't know I can set negative frame.