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Starting simulation before frames begin


chazfest

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Howdy,

I've built a basic water fountain and am fairly happy with it now, so am beginning the process of inserting it into a live action plate using a matchmoved camera that I've brought across from Nuke.

Only problem is, I really want the fountain to have some water in it's base from frame one, so I'm wondering if I could force the simulation to begin before the frames commence, ie. minus numbers? I know I can delay the start of simulations by altering the 'Creation Frame' parameter, so wondered if this same parameter could be manipulated for the opposite effect. I've tried simply typing '-150', but this doesn't seem to work.

I did initially add a layer of water at the base, but as soon as the particles from the fluid emitter hit it, everything went pretty crazy! lol. Splashes uncontrollably erupting all over the place, I monkeyed around with the surface tension, bounce and friction of both the fluid emitter and the fluid resting in the base, but it always seemed really messy.

So I'm wondering if I could instead force the simulation to take place at, say, frame -150 or something similar?

I hope this makes sense.

Thanks in advance.

Chaz

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I would offset the plates and camera by 150 frames so your shot starts at frame 150. Personly I dont like working with negative frame numbers.

If you really have to start at frame 1, you can sim some frames and create a initial state(which could be good anyway).

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Why not generate a start .sim file to get your simulation rolling from frame 1?

Here's one setup where you can create and manage a sim file output and read in to start with a baked preroll of a dop sim.

Move the display flag to the Gravity and play to frame 100. Write out the file from the first File DOP. Move the display flag down to the Switch DOP that has a simple if() condition to switch the file out after frame 1 to get your baked-in preroll.

flip_preroll_frame100.hip

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