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vbk!!!
07-23-2003, 10:02 AM
i discover a the plug openexr on flay.com
Can someone explain the difference between exr and hdri
or a link with an explanation.

nuclearchutney
07-23-2003, 11:40 AM
Originally posted by vbk!!!
i discover a the plug openexr on flay.com
Can someone explain the difference between exr and hdri
or a link with an explanation.

HDRi is a 32 bit per channel format developed by Paul Debevec. Go to http://www.debevec.org for more info on the format.

EXR is 16 bit per channel "Half" format.
Excerpt from ILM's OpenEXR Site:
ILM decided to develop a new HDR file format with 16-bit floating-point color component values. Since the IEEE-754 floating-point specification does not define a 16-bit format, ILM created the "half" format. Half values have 1 sign bit, 5 exponent bits, and 10 mantissa bits. For linear images, this format provides 1024 (210) values per color component per f-stop, and 30 f-stops (25 - 2), with an additional 10 f-stops with reduced precision at the low end (denormals).

The half format supports denormalized numbers, positive and negative infinities, and NaNs. It is identical to the half data type in NVIDIA's Cg graphics language, allowing a developer to process values from an OpenEXR image directly on current NVIDIA GPUs such as the GeForce FX family.

In addition to the half data type, OpenEXR supports 16-bit unsigned integer and 32-bit floating-point data types. OpenEXR images can have an arbitrary number of channels, each with a different data type.

The current release of OpenEXR supports several lossless compression methods, some of which can achieve compression ratios of about 2:1 for images with film grain. OpenEXR is extensible, so developers can easily add new compression methods (lossless or lossy).

OpenEXR images can be annotated with an arbitrary number of attributes, e.g., with color balance information from a camera.


The EXR format supports the half function in nVidia's CG language and thus is supported natively on their new GeForce FX and Quadro FX 3D graphics card solutions.

does this help?

vbk!!!
07-23-2003, 11:46 AM
ok

i understand better what is exr now

thanks.

nuclearchutney
07-23-2003, 12:00 PM
Originally posted by vbk!!!
ok

i understand better what is exr now

thanks.

no problem :)

http://www.debevec.org/HDRShop/main-pages/intro.html
and
http://www.openexr.com
are the two best places to find out more about what exactly is an HDR or an OpenEXR Image

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