On Mon, 08 Mar 2004 18:30:01 +0100, Marton Fabo <mor### [at] eikbmehu>
wrote:

>So, if I break up an animation into frames and submit each one 
>separately to a rendering farm basically results in the same as if it 
>were submitted in one job. If that's the case, the answer is satisfying (:

Well, *almost*. You have to make sure that no frames depend on
anything from previous frames.

The most common case is with things that require a lot of parsing;
there the usual practice is to save the intermediate result (as valid
for the current frame) to a file, then in the next frame read that
file and avoid calculating everything again. Examples where this
approach is used are mostly physics simulations - particle systems,
kinematic or dynamic simulations (billiards, cloth...), planetary
systems, flocking algorithms etc.

It is also not uncommon to have some frame parse heavily and generate
for example a height field, some numerical data, a texture, or even a
whole .inc file, which are then reused as-is in further frames. An
example of this would be an animation where the camera flies over a
forest or grass field or such.

The last thing I can think of is more of a speculation than a real
application and concerns radiosity. POV-Ray uses a pretty intelligent
Monte-Carlo sampling algorithm for gathering radiosity samples which
means that only those parts of the image visible from the camera will
be sampled, thus saving a lot of unnecessary calculations. In
addition, POV-Ray allows to save and load radiosity data so that most
of the preliminary calculations are avoided. In effect this means that
if you want to render a fly-by or fly-through animation with
radiosity, you can save the radiosity data after each frame and load
it in the next frame. POV-Ray will then only perform the heavy
radiosity calculations where needed, i.e. in parts which were
previously outside the camera field of vision. Since in most such
animations the camera field of vision changes insignificantly from
frame to frame, this could lead to a significant speed-up of radiosity
calculations. Mind you, I haven't tried this but it sounds like a good
idea :)

Anyway, to get back to your original question, if you want to spread
an animation across multiple CPUs, then you will have to make sure
that you don't use the above techniques.


Peter Popov ICQ : 15002700
Personal e-mail : pet### [at] vipbg
TAG      e-mail : pet### [at] tagpovrayorg

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