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This aerial shot of a nuclear explosion in Terminator shows
an explosion in a city at night.
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As the explosion occurs, everything
goes white. A little later in
the scene, the image fades
back to black and the viewer
begins to see detail of the city
again as rolling clouds from the
explosion move outward from
the blast site. With OpenEXR,
the detail is retained. |
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Without OpenEXR, the bright
light from the explosion washes
out the detail needed for later in
the process. |
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| OpenEXR, the same software used for making special
effects in the movies Terminator, The Hulk, Van
Helsing, Pirates of the Caribbean, Harry Potter, and Star
Wars, is available free from Industrial Light & Magic
(www.ilm.com), a Lucasfilm Ltd. Company. OpenEXR
(www.openexr.net) is open source, extended dynamic
range image file format.
“You can download the software from the web site
and use it free of charge,” says Florian Kainz, ILM’s
principle engineer and software developer. “You just
can’t claim that you wrote the code.”
OpenEXR is a 16- and 32-bit, floating-point file format
with much greater dynamic range than existing 8-
and 10-bit file formats. Though it does not require a
graphics card, it is fully compatible with the floatingpoint
pixel formats supported by the latest graphics
hardware. Its lossless data compression achieves compression
ratios of 2:1 for scanned film images.
“We initially developed it for our own purposes at
ILM,” recalls Florian. He explains that ILM needed the
high dynamic range for picture quality and the ability to
produce gradual differences in brightness. “We also
needed a file format that compressed well,” he says. “In
some compression schemes, the data in the image is not
well preserved,” says Florian. He notes that OpenEXR
stores data for high quality images without an excessive
file size.
OpenEXR features support for mipmaps, ripmaps,
and other tiled images; a new Pxr24 compressor contributed- |
contributed
by Pixar Animation Studios; support of high
dynamic range YCA (luminance/chroma/alpha) images
with subsampled chroma channels; abstracted file I/O
allowing it to be used with interfaces other than C++’s
iostreams; and new utilities for manipulating tiled
images files.
For documentation, links, and more information on
the free software, go to
www.openexr.net. Also visit
www.ilm.com.
OpenEXR has been adopted from organizations
in the effects industry as well as
the software, hardware, academic and
even gaming communities. Other potential
applications include digital cameras; digital
scanning of paintings and other museum
artifacts; and satellite images used
for geological, construction, military, and
agricultural applications. |
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