Chaos Corona Forum
Chaos Corona for 3ds Max => [Max] Bug Reporting => [Max] Resolved Bugs => Topic started by: alexyork on 2017-07-17, 11:32:13
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Hi guys,
Have you changed anything in recent versions that has reversed behavior when using tone mapping controls such as contrast etc. and then you can't reduce exposure of an EXR to recover detail? I've just noticed this in a big batch of renders this morning. I remember this was the old behavior, which you then fixed somehow, but it seems it's back again? As soon as I reduce exp in Photoshop it just goes grey as if it's a regular 8-bit image instead of a half-float EXR.
Cheers,
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The change kind of like that, that I recall, was that using a LUT would lose the HDR, but that was fixed - all still seems ok here still with a few quick tests, I tried with tone mapping on and off, and LUTs applied and not applied, and the EXRs (saved directly from the VFB, not from the CIE, haven't tested that yet) were still responding as 16 bit half floats EXRs with the full range when an Exposure adjustment layer was used in Photoshop (loading via the EXR-IO plugin).
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The change kind of like that, that I recall, was that using a LUT would lose the HDR, but that was fixed - all still seems ok here still with a few quick tests, I tried with tone mapping on and off, and LUTs applied and not applied, and the EXRs (saved directly from the VFB, not from the CIE, haven't tested that yet) were still responding as 16 bit half floats EXRs with the full range when an Exposure adjustment layer was used in Photoshop (loading via the EXR-IO plugin).
Weird. I've just saved a 16-bit half float EXR from VFB with tone mapping controls turned on on my cameramod and range is lost. When I disable that tone mapping and re-save the range is returned to normal.
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Not sure on that unfortunately - most of the tone mapping does make things nonlinear of course. However the EXR still preserves detail in my quick tests compared to, say, a PNG. Couple of images where I used aggressive VFB changes (yes it looks horrible, just wanted to be extreme :) ), showing the unedited image, then the Exposure adjustments in Photoshop for the EXR vs the PNG, and the EXR shows the cloud details are still there, while the PNG just has that flat grey response.
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Not sure on that unfortunately - most of the tone mapping does make things nonlinear of course. However the EXR still preserves detail in my quick tests compared to, say, a PNG. Couple of images where I used aggressive VFB changes (yes it looks horrible, just wanted to be extreme :) ), showing the unedited image, then the Exposure adjustments in Photoshop for the EXR vs the PNG, and the EXR shows the cloud details are still there, while the PNG just has that flat grey response.
Are you testing on a daily? We're on 1.6.1 here.
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This one was 1.6.1 too, I rolled back from any dailies. Thoughts, could you send the .conf file for the VFB post and I can try applying the same settings to my images by loading that up? Any idea if this is happening on every scene btw, or just one specific one? Also, any lightmix involved, I was just testing Beauty pass here, just trying to think of what might be different!
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This one was 1.6.1 too, I rolled back from any dailies. Thoughts, could you send the .conf file for the VFB post and I can try applying the same settings to my images by loading that up? Any idea if this is happening on every scene btw, or just one specific one? Also, any lightmix involved, I was just testing Beauty pass here, just trying to think of what might be different!
Hey Tom. I'll try to look into this more. No Lightmix involved, and the tone mapping controls are all set by a cameramod, not in the VFB. I'll see if I can narrow down somehow.
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no postproc changes were made after 1.6 AFAIK
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I just checked this with 1.6 hf1 and everything seems to work fine.
Alex, how exactly did you save your output, and how are you loading your hdri (if you are using one)?
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Hey Marcin,
All is fine, confirmed. Turns out that the scene I was testing this on was a weird one where lowering the exp of the render would result in a flat grey tone to a surface just by bad luck/coincidence of the design... lol.. sorry about that!
Feel free to nuke this thread!
Cheers,
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I still think it´s a kind of bug. I had/have such a scene as well (scratching my head which one....) which acted like Alex describes. Older scene, Corona 1.5 maybe. However, resetting Corona settings solved it.
Good Luck
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Maybe you had highlight clamping enabled in the system tab? I can imagine that would result in such behavior.
Let's move this to resolved bugs, and we'll return to it if it ever happens again, and if it's reproducible.
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Right chaps... I'm afraid this bug is back, we're pretty sure. We have two scenes, neither using Highlight Clamping - as soon as you push Contrast above 0 and save as a half-float EXR it loses the ability to underexpose properly in post. It still over-exposes properly (or at least it looks to be), in photoshop, but when you drop the Exposure it just turns to grey mush.
This is in 1.6 hotfix 2. Oh and by the way, we've tested this on both a standard beauty pass and in lightmix - same result in both.
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Alex, is this if saving from CIE only or does it happen with MaxVFB, too? CIE in 1.6.1 saves EXRs differently than before. I haven't figured out what exactly happens but using CIE from recent dailies works fine.
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Hey.
This is being saved from Corona Frame Buffer (via Deadline).
Cheers,
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hi, can you show the difference? And do you mean contrast different from 1? 1 is the "no op" value
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hi, can you show the difference? And do you mean contrast different from 1? 1 is the "no op" value
Yeh sorry mean't 1.0. Erm, I'd have to produce a test scene to illustrate. I'll see when I can get round to it, but it should be reproducable by producing a render that is a bit overexposed so you can't see any texture detail in a wall (for example), then trying to reduce exp in post. With Contrast = 1.0 the texture becomes revealed and clear as you drop the exposure. With Contrast /= 1.0 then it just crushes to grey.
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I tried it with some artificial test scenes and I could not reproduce it...
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I tried it with some artificial test scenes and I could not reproduce it...
Half float EXR?
I'll see if we can nail it down somehow for you soon. Endless deadlines at the moment.