"Chambers" <ben### [at] pacificwebguycom> wrote:
> Would it be faster if different threads rarely accessed the same locked
> data?  We could split the sample tree into several smaller trees
> (sub-trees, if you will) based on scene geography (grouping close
> samples in the same tree).  Then, when performing sampling, a thread
> would be most likely to only need access to a few of the sub-trees
> (those nearest), and rarely the sub-trees further away.  If you only
> have a few threads, then the chances of multiple threads needing the
> same sub-tree at the same time are minimized.  Having more threads would
> add more overhead, of course, because thread collision is more likely.

Doesn't work I guess. Think of an ordinary room: For most samples, you will need
samples from all across the room, not just a particular corner.

There may be scenes where your idea might speed up things, but in general
radiosity interaction between different parts of the scene can be expected to
be quite high.

The approach of subdividing an image, and feeding each part to a separate task,
works with regular raytracing only because even if parts of the scene interact
through reflection, there is no data cache being built and re-used - because
the chances of two mirrors showing exactly the same points are minimal (let
alone that even then the incident angles would be different) and so caching
wouldn't be worth the pain anyway.

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