[Sidefx-houdini-list] Caching fluid sims

jlait at sidefx.com jlait at sidefx.com
Wed Feb 11 16:16:05 EST 2009

On Tue, Feb 10, 2009 at 01:26:25PM -0500, craigleehoffman at aol.com wrote:
> I am caching out a fluid sim by appending a File SOP to the bottom
> of the AutoDopNetwork (as is done in the tutorials), setting it to
> "Write", and then setting it to "Read" when it is done.? But when I
> change frames and expect a fairly quick update due to the "Read"
> File SOP being activated, I get a lengthy wait with things like "DOP
> Pre-Simulation Step" and "DOP Network Cook" over and over in the
> lower left-hand corner of the interface like it is re-calculating,
> and I end up cancelling because it is taking too long.
> Any ideas what I am doing wrong?? The fluid sim data is out there on
> disk just fine and took over an hour to calculate and write out, so
> I assume it is good.

    By default DOPs will reload in all the frames up to the current
frame.  Loading 100 frames from disk can easily be as slow as the
original sim.   One work around in 9.5 is to turn on the Timeless
option on the Dop Network, this will then only cook the current frame
letting you jump around the playbar only paying the load time once.

    Still, loading a .sim can be slower than loading the corresponding
volumes because it loads all the fields while with volumes you can
extract just the subset you need.  The recommended output from a fluid
sim is thus usually a .bgeo.gz sequence.
        - Jeff Lait

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