To give an overview of current development progress:

* Some differences to 3.6 have been identified and reverted.

* Potential multithreading issues in the radiosity code have been examined; the
beta.29 code was found to be technically thread-safe regarding access to the
radiosity data cache.

The locking concept has been refined to improve performance.

The known issues regarding exact reproducability of output have not been
addressed yet (except that a basic idea exists). Currently, exact
reproducability of output of radiosity scenes can only be guaranteed for
single-threaded operation, and provided that the same version is used.

* Output and performance of the current development version have been compared
to 3.6 with satisfactory results.

The following scenes were used as benchmark samples:

- All scenes in ../scenes/radiosity/
- All scenes in ../scenes/advanced/ using radiosity
- Two self-made scenes

Resolution was set to the highest recommended values from the respective scene
files. Animations were not tested.

Generally, all scenes now render virtually identical to the 3.6 output (showing
only random jitter effects), except for the following:

- ../scenes/radiosity/cornell.pov: The top-rear corners of the room render
slightly darker, while the top-front-right edge of the cube renders slightly
brighter; these may still be just statistical differences though

- ../scenes/advanced/balcony/: Some artifact-ish speckles in the roof seen in
the 3.6 shot are eliminated; the floor renders significantly brighter
especially in the shadows; the table cloth renders significantly darker in the
shadows (almost black); however, the complexity of the scene currently prevents
a thorough analysis of the reasons.

- ../scenes/advanced/blocks/: The scenes render brighter due to different gamma
handling.

- ../scenes/advanced/object_pattern.pov: This scene shows a significant
brightness gain in darker areas, and some "artifacts" in the same areas; closer
inspection shows that the "artifacts" are actually reflections of shadows, and
that the brightening is due to the non-shadowed areas being reflected. So we
actually have an improvement in quality, but it also hints at some yet
undiscovered difference to 3.6 code.

- The self-made scenes showed significant differences not yet analyzed. One of
the scenes indicates a higher robustness against undesired "light leaks", but
the reason for this is not explained yet, and in any way indicates unidentified
differences to 3.6 code.


Runtime behaviour was compared on an AMD Phenom X4 9650 2.3GHz QuadCore with 6
GB of RAM running a 64-bit Linux. MegaPOV 1.2.1 was used instead of POV 3.6 due
to availability of a better-optimized version.

Pure computing power requirements ("CPU time") varied within ca. +/-20% of that
of MegaPOV. Comparison of CPU time with "Wall clock" time showed typical "dead"
time of 1-2% when running 4 threads for larger scenes, going as high as 5% for
one of the self-made scenes. Smaller scenes, running just a few seconds,
typically showed a significantly higher "dead" time, maybe due a
disproportionate effect of I/O delays during scene parsing.

Post a reply to this message