"boltcapt" <bol### [at] aolcom> wrote:

the blank 9th line should read:

performance is even more interesting: total speedups range from 17x to 63x,

I have no idea why it was deleted

> I have been a POV-Ray fan for a long time. I know there have been several
> approaches to distributed rendering over the years, but after retiring I was
> looking for a project and decided to create my own distributed client-server
> rendering system, using POV-Ray 3.7.0.10 as the base.
>
> So far the results have been encouraging. With 8 clients, measured speedup for
> still-image rendering ranges from 88.4% to 98.2% scaling efficiency, depending
> on image size and complexity (larger, more complex images scale best). Animation
>
> depending on scene characteristics. These gains come not only from distributing
> work across clients, but also from parser and caching optimizations that
> eliminate a significant amount of repeated work.
>
> Here is a summary of the project.
>
> For hardware, I wanted to see what could be accomplished with a cluster of
> Raspberry Pi 5 Compute Modules. To that end I built two self-contained four-node
> Pi clusters. I'm happy to share hardware details if anyone is interested, but
> the hardware is not really the focus of this post.
>
> The more interesting work was creating the client-server software environment.
> Starting with POV-Ray 3.7.0.10, I modified the renderer to operate as a
> non-terminating client and optimized it for distributed operation. The server
> assigns work and collects results. Work distribution itself is straightforward:
> still images are divided into row ranges, while animations are distributed one
> frame per client.
>
> The key client-side modifications are aimed at avoiding unnecessary repeated
> work. Each client maintains a single persistent POV-Ray session across multiple
> tasks and renders. Parsed scene information is cached so that repeated renders
> of the same scene do not require reparsing. In addition, I modified the parser
> to support a static keyword, allowing large clock-independent structures to be
> cached and reused between animation frames. Similar concepts have been explored
> before, but the persistent-session architecture makes this particularly
> effective.
>
> I also added a feature that I personally felt was missing from POV-Ray: the
> ability to call precompiled native functions directly from the Scene Description
> Language. To support this, I developed a plugin system and extended the parser
> with five new function types: userfun(), uservectfun(), usercolorfun(),
> useruv(), and userfracfun(), returning scalar, vector, color, UV, and 4D values
> respectively.
> For example:
> uservectfun("curl_field", x, y, z)
> where curl_field is a function exported by a dynamically loaded plugin.
>
> The server side includes a number of supporting capabilities, including
> heartbeat monitoring, failed-task reassignment, thermal management, archive
> reuse, and delta synchronization of include files.
>
> I'd be interested in hearing whether others have experimented with similar
> persistent-session approaches, parser extensions, or SDL plugin mechanisms.

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