B268a cloth - pre roll not working?


I have a simple plane with cloth simulation added to it, preset type silk, I positioned this plane 1 BU above the ground.
The ground is a plane4 as well with collision activated.
I want the cloth simulation start 40 frames earlier to settle down the cloth.
So I set the ‘pre roll’ value to 40. But if I hit ALT-A the cloth simulation is not working anymore the plane behaves like if there was no cloth simulation at all.
If I set ‘pre roll’ to 0 again, the cloth simulation is working again, but the I must wait until 40 frames are over.

Is this a bug or a feature?

So what I need is to start the cloth simulation at frame -40 so the plane does not move anymore at frame 1. And from frame 1 the cloth I want to move or whatever. How can I do that?


Have you tried enabling ‘Allow Negative Frames’ in User Preferences / Editing and then Bake the cloth sim.

Hi Richard,

thanks, I set now ‘Allow negative Frames’, but the ‘Pre roll’ options does not allow negative values. :frowning:
And if I enter positive values, as I said in my 1st post, the whole cloth simulation seems to be switched off.

Still need help, thanks!

Also ran into this some time ago. I thought it was broken and after your report I almost filed a bug report. But after some fiddling around I got it to work.

Here are the steps:

  • Make sure Allow Negative Frames is turned on as Richard mentioned.
  • If you already have cloth on an object, first remove it and then add it again. This is to make sure everything from the simulation is gone from memory or cache (if I first played back my simulation and after that tried to bake with pre roll, it didn’t work).
  • Set the pre roll to the amount of frames you want.
  • Set the cache start frame to the negative number of the Pre roll (so if you have set Pre roll to 50, set the start frame of the cache to -50).
  • Set the current frame to a frame before the start of the cache (so in my example to -51 or lower)
  • Then bake the simulation.

Hopefully this works for you too. But as it seems the cloth sim could definitely use some improvement in this area.