I can already tell you -- since you are starting with 8 bit data, you'll be better off with TIFF because it natively supports 8 bit channels. OpenEXR does not -- it will have to up-convert to 'half' (16 bit floating point), and furthermore, the ImageCache/TextureSystem internally converts half to float for storage in the in-memory cache.
On Oct 12, 2012, at 9:37 AM, Michel Lerenard wrote: > Thanks for these examples. That's exactly what I need. > > I'll run the same test and will compare EXR and Tiff to see if one format is > better than the other. > > On 10/11/2012 06:32 AM, Larry Gritz wrote: >> >> Even when using automip and autotile, you're going to get horrible >> performance if your texture cache size is not at least big enough to hold >> the image. >> >> For JPEG images, we're just calling the underlying libjpeg, we ask for >> scanlines in batches, but I can't swear to the efficiency of libjpeg, for >> all I know it tries to read the whole thing at once and buffer it. I can >> vouch more strongly for libtiff and OpenEXR. >> >> For film anyway, JPEG is considered a poor texture format because it doesn't >> support alpha channels, is only 8 bits, is lossy, and doesn't have any >> notion of MIP-mapping. So we figured it was so ill-suited to the task that >> the requirement was simply to make it work, not to make it very efficient >> for huge files. For that, we turn to TIFF and OpenEXR, which tend to >> satisfy the whole range of requirements of a good texture format. >> >> If you must use this JPEG file in its original form, assuming you have >> memory to burn, I would advise using a 2 GB cache. 256 or 512 MB is just >> too small, that will force it to constantly need to re-read sections of the >> image. >> >> You can convert it to a tiled format with >> >> iconvert world.topo.bathy.200411.3x21600x21600.C1.jpg --tile 64 64 tiled.tif >> >> Took me 48 seconds (including I/O), and the file is 415 MB (versus 43 MB for >> the original JPEG -- but that's because it's a lossy format) >> >> That will get it tiled, which should make a big difference. Additionally >> making into a full MIP-mapped, tiled texture, via >> >> maketx world.topo.bathy.200411.3x21600x21600.C1.jpg -o mipped.tx >> >> That took 3 minutes and needed several GB of RAM (it's a huge file!), and >> results in a 550 MB tiled MIP-mapped TIFF file, which should be extremely >> efficient to texture map. >> >> >> >> On Oct 10, 2012, at 7:33 AM, Lerenard Michel wrote: >> >>> Hi, >>> >>> Brecht: thanks for your answers, it does clear things a bit. >>> I've enabled automap and autotile options. It does solve the memory issue, >>> but i get horrible peformance instead: on small files it works with >>> overhead, on the huge one below it was so slow i had to stop the rendering >>> process.(using the default 256 cache value) >>> >>> Larry: the file i use to test is a huge JPEG, => >>> http://eoimages.gsfc.nasa.gov/images/imagerecords/73000/73884/world.topo.bathy.200411.3x21600x21600.C1.jpg >>> that can be found on this page: >>> http://visibleearth.nasa.gov/view.php?id=73884 >>> >>> >>> After thoses tests, i think i'm going to work with temp images in EXR, >>> converted from formats that does not support tiles: >>> the cache does work correctly in this case. (i checked with a 250Mo tiled >>> exr file) >>> I have not yet tested maketx, i don't know if it's a fast process, but it >>> seems to be a good candidate to do the work. >>> >>> >>> -------------- >>> Michel >>> [email protected] >>> _______________________________________________ >>> Oiio-dev mailing list >>> [email protected] >>> http://lists.openimageio.org/listinfo.cgi/oiio-dev-openimageio.org >> >> -- >> Larry Gritz >> [email protected] >> >> >> >> _______________________________________________ >> Oiio-dev mailing list >> [email protected] >> http://lists.openimageio.org/listinfo.cgi/oiio-dev-openimageio.org > > _______________________________________________ > Oiio-dev mailing list > [email protected] > http://lists.openimageio.org/listinfo.cgi/oiio-dev-openimageio.org -- Larry Gritz [email protected]
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