Warp wrote:
> 
>   One possibility would be to temporarily write the image in raw format
> onto a file and then read parts of that file on demand. This would just
> consume disk space instead of consuming RAM.

That would mean unnecessarily copying possibly lots of GB and in case of 
a compressed format also decompressing it - data that is possibly not 
needed at all since the render only uses a small part.

If such a patch is developed it would be good to have both the 
possibility to use large uncompressed files directly and alternatively 
to specify already existing tile images that can directly be used for 
the dynamic caching.  Often when dealing with large images you have them 
in form of tiles anyway to simplify handling and local modifications.

What would make sense for compressed formats is to temporarily store 
expired tiles to disk to avoid decompressing them again in case they are 
needed.

>   The difficulty in this is how to decide when to drop image parts from
> the cache. There's no universal way of knowing how much memory is
> available. One possibility would be for the user to specify manually
> some value.

That's what makes most sense i suppose (having the possibility to 
specify the tile size and the number of tiles to keep would allow 
detailed control over the performance).

Christoph

-- 
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http://www.imagico.de/ (Last updated 20 Aug. 2006)
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