"Lloyd" <nomail@nomail> wrote:
> Hello,
>
> I am interested in using POV-Ray in a distributed computing environment, in
> which I may have many compute nodes available for rendering.  One requirement
> for this project is that an image rendered in a single pass should match exactly
> an image that is rendered in pieces with Partial Output and then properly
> reassembled.
>
> I have been trying to verify this behavior on a fairly large file with many
> thousands of elements (frames of this video: https://youtu.be/Pa149iuBPGw , a
> spinning glassy earth globe with thousands of spherical markers), by rendering
> one frame in a Single-Pass, and again in 4 Quadrants and then merging
> (Merged-Quadrant).  I was surprised to see small differences distributed
> throughout the image.  I thought it might be my particular file, which has many
> glassy elements with reflection and refraction.  But then I tried the same test
> on some standard images from the POV-Ray distribution.  There were no problems
> with biscuit.pov.  But I found a lot of problems with benchmark.pov.

Your problems are a user error: Using features with randomized or
order-dependent features cannot work the way you expect. Disable such features
and the problem goes away.

Thorsten

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