Thanks for the tip, I didn't thought about this. 2012/10/12 Larry Gritz <[email protected]>
> 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 > [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] > > > > _______________________________________________ > Oiio-dev mailing list > [email protected] > http://lists.openimageio.org/listinfo.cgi/oiio-dev-openimageio.org > >
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