Open EXR Testing

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Old 07 July 2003   #1
Open EXR Testing

I was doing some tests using the Open EXR format by converting a sequence of Tiff files to EXR with compression. I was amazed to see that the compression took a 2.7MB frame down to 800k without any change in the frame. I zoomed in and did a direct A/B comparision and saw no change to the pixels. I can see why ILM is using this. I use Digital Fusion 4.02 and the frames were only 8-bit. My next tests will be with cineon files.

Any one else working with this format yet?
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3DDave
 
Old 07 July 2003   #2
I'm using our Max OpenEXR plugin for some outputs. Main advantage over HDR being the alpha channel and a comment channel.

Unfortunately max itself doesn't give the full fidelity possible with EXR, but 16bit (HALF) is generally good enough.

Can't wait for Cinepaint to have EXR on the Windows version as well, though.
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Old 07 July 2003   #3
Re: Open EXR Testing

Quote: Originally posted by 3DDave
I zoomed in and did a direct A/B comparision and saw no change to the pixels.

It's a lossless compression(like tif/tga/iff/etc...), so unless your changing the bit depth, there can't possibly be any information loss.

I'm waiting for shake and maya to support it. MR and Prman allready do though which is nice. So I really just need shake to support it.
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-deke
 
Old 07 July 2003   #4
I wonder if AE6 will support it? it sounds pretty cool.
 
Old 07 July 2003   #5
mental ray supports openexr?
which outputs does it include?
 
Old 07 July 2003   #6
Does OpenEXR support arbitrary channel data? Such as Z, UV coords, pixel vectors, etc?
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Fix it in pre.
 
Old 07 July 2003   #7
Here is the OpenEXR site

http://www.openexr.com
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3DDave
 
Old 07 July 2003   #8
Quote: Originally posted by dmeyer
Does OpenEXR support arbitrary channel data? Such as Z, UV coords, pixel vectors, etc?

It handles RGBAZ by default. It is a very flexible file format(and opensource), so if your a programmer any additional data can be added like pixel vectors, UV's, etc...
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-deke
 
Old 07 July 2003   #9
Actually, at this time it handles anything, but has set specifications for RGBa.

In work by ILM, they found that HALF wasn't good enough for z-buffers, and added full 32bit support.

However, z-buffers aren't specified in any way, whilst you'd need it specified to keep it compatible across applications.

For one, the channel name (by which channels are identified). I'd imagine "Z" would simply be picked, but one never knows.

Then there's the problem of some applications assuming Z as a pure distance from the camera to the shaded point, whereas others take the distance from the shaded point to a virtual plane parallel to the view plane.

I'd think the former is better as you can always work out the latter from that, but the other way around you would have to make more assumptions.

Well anyway.. so Z isn't quite defined yet
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Old 07 July 2003   #10
Re: Re: Open EXR Testing

Quote: Originally posted by beaker


I'm waiting for shake and maya to support it. MR and Prman allready do though which is nice. So I really just need shake to support it.


When both Shake and Maya have robust support, I'm switching.
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Fix it in pre.
 
Old 07 July 2003   #11
is it possible that openexr is not available for mr via the maya to mr bridge?
 
Old 01 January 2006   #12
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