Scripts for frame accurate stuff

[Achim]

Continuing from an old topic from the betaxx mailing list. Topic was “I need help fixing a problem” (from june 2007)

Basically this reply from Malcolm described the problem I was/am facing

Here’s another example. Say you are rendering a sphere located at (0,0,0), in a Render TOP. On frame 10 you have a logic CHOP that executes a script
that changes it’s position to (0,0,10). Now you may expect that the image you see in the Render TOP on frame 10 is the sphere located at (0,0,10). But the truth is it’s position could be either (0,0,0) or (0,0,10). If the Logic CHOP cooks before the Render TOP cooks, then the position will be (0,0,10). But if the Render TOP cooks before the Logic CHOP, the position will be (0,0,0), and it’s not until the Render TOP cooks again (on frame 11) that it’ll use this new position.

So the long and short of it is that you have no guarantee when a script is going to execute, and they shouldn’t be used for stuff that needs to be perfectly frame accurate. Even the a delayed run command will run on different frames different times depending on many factors.

We’re looking into a way to make this consistent.

So I’m still getting flickers in my render due to above behavior and as I can’t control everything through expressions, I somehow need to use scripts for “frame accurate” stuff. (For countless hours I tried introducing artificial dependencies, and what not, but can’t get rid of the flickering).

So I’m wondering if it would be possible to get a run command option which would force
the script to run
a: on the next frame (-f 1)
+
b: before everything else cooks on that frame?

Or something similar. Thanks
Achim

[malcolm]

The run command actually already has a -f option.

I just made it so delayed scripts have a high priority now so they will be one of the first things that run at the start of a new frame. Other things may cook before, but they are some *In nodes (Touch In set to global) and the Perform DAT, so that should still be fine.

You wont have any control over the order in which the scripts run though, but hopefully that won’t be an issue.

[Achim]

wow, thanks Malclom! Made my day. Finally no more flickering, I hope. I’ll let you now how it works when the next experimental build is released.
Hope it wasn’t too much work. Thanks again

[Achim]

it’s working great. Thanks again!