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On 09/05/2017 01:06 PM, John Denker via cryptography wrote:<br>
<blockquote type="cite"
cite="mid:d123acd3-f31c-c658-575a-0ef727ce9453@av8n.com"> --
Sometimes you want something that is entirely deterministic and
predictable, just complicated-looking, e.g. sea grass.<br>
</blockquote>
<br>
And presumably the folks writing the rendering software <i>did</i>
know this. The older rendering software knew how to keep track of
its RNG state, so it could re-render frames without positions
changing. It is common to re-render 3D scenes and fragments of
scenes as components are added, tweaked, lighting changed,
eventually better quality output generated, etc. The sea grass that
Nemo is swimming through had better not jump from one rendering to
another. Someone was very aware of this.<br>
<br>
But it seems that wasn't explicit in the "source code" that they
preserved for Finding Nemo. And somehow programmers are better at
writing functions for importing data than they are for exporting
data...<br>
<br>
Similarly for any Monte Carlo simulation: frequently one wants to be
able to rerun different version of the code on previous "random"
data.<br>
<br>
-kb<br>
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