2 OpenEXR questions

[q_vazk]

Can I add one more, please?
Why is it that everytime I renderout to .exr My environment (Physical sun/sky) is
missing?

Thanks :)

Regarding Q2: I think you can do it by simply disableing the Mia_exposure shader and
just render out...

[avinashlobo]

Hey, good question. I never noticed it before. Yeah, the environment is missing even if you disable the Alpha on the EXR. This can be Question 3.

Coming back to Question 2, does it mean that if you output 32-bit HDR info, the mia_exposure_simple is pretty not required?

Tying it in with question 1, considering that Gamma 2.2 is visually preferred, does an OpenEXR workflow mean that you're limited to 1.0 Gamma?

Thanks again. If anyone could clear this up, it'd be really helpful.

Cheers!

[djx]

re Q2: The mia_exposure is not needed if you are rendering to a HDR format like exr, since the mia_exposure is there to reduce the exposure to a low dynamic range, which explains the compressed highlights.

re Q1: I'm prepared to be corrected here, but I would use gamma 1.0 when rendering HDR. You can make gamma and exposure adjustments in post.

-- David

[q_vazk]

If you would render out 'uncompressed' 'unclamped' 32bit images what would you use to
tonemap them? Can it be done in Photoshop?

[Visor66]

yes, import the 32bit into photoshop, then you have to change it to at least 16 bit to work with it in photoshop (CS2) and then you get the tonemapping options for your image!

[q_vazk]

I'm sorry... I'm a total noob. What tools would you use to clam down a 32bit image?
Is there a tutorial that deals with this type of workflow anywhere on the net?

Thank you for your care.

[Visor66]

well, you import your 32 bit image into photoshop. Then go change the image mode (image ->mode ->16 or 8 bit) and then a window will pop up that will let you make the tonemapping adjustements...Again thats cs2. Dont know if something has changed for cs3. Thats it.

Helped?

[F3LIC3]

Here (http://mymentalray.com/mymr_tutorials/tutorials_custom_tutorials/Jeff_Exposure_Control.htm) is also a small tutorial from Jeff Patton to adjust your exposure in photoshop.

The first part is for 3ds max but you should be able to do in maya and the photoshop part is the same anyway.

[sixbysixx]

well, you import your 32 bit image into photoshop. Then go change the image mode (image ->mode ->16 or 8 bit) and then a window will pop up that will let you make the tonemapping adjustements...Again thats cs2. Dont know if something has changed for cs3. Thats it.


Helped?

No, that works pretty much the same in CS3, BUT:
DO NOT USE THE TONEMAPPING FROM THE CONVERT TO 8 OR 16 BIT DIALOG BOX!!!
Because this only affects Luminance values. It matches the effect you would get from 32bit preview options - I have no idea why they did it like this - I'd call it a bug.
Instead go to Image/Adjustments/Exposure, or, if you are in CS3 Extended, create an Exposure adjustment layer.

[Visor66]

No, that works pretty much the same in CS3, BUT:
DO NOT USE THE TONEMAPPING FROM THE CONVERT TO 8 OR 16 BIT DIALOG BOX!!!
Because this only affects Luminance values. It matches the effect you would get from 32bit preview options - I have no idea why they did it like this - I'd call it a bug.
Instead go to Image/Adjustments/Exposure, or, if you are in CS3 Extended, create an Exposure adjustment layer.

ah ok, thanks for the heads up! Will try it next time!

[jasonhuang1115]

Hey, avinashlobo,

I got a question for you. I have been trying to get multi-channel OpenEXR from Maya and only successfully got it when using puppet's p_shader. Without using p_shader, I knew I can render out 32 bit EXR image using Mental Ray, but whenever I load the render into Nuke, it's not like multi-channel or even not more than RGBA - 4 channels. So, I am wondering how did you render the multi-channel EXR from Maya? Thanks. :)

[QUOTE=avinashlobo]Question 1
Hello everyone. I've been fiddling with getting a multi-channel OpenEXR render going and have a question regarding using it in conjuction with mia_exposure_simple.

[living3d]

I'm sorry but i have an issue in the very beginning...I followed the manual description:

Disable the mia_exposure_simple shader.
Render the image to a file in some form of HDR capable format (like .exr, .hdr or similar), for example preview.exr.
Enable mia_exposure_simple shader again.
Set the preview parameter to the file saved above, e.g. preview.exr.
Enable the use_preview parameter.
Disable any photon mapping or final gathering.
Re-render. The renderering will be near instant, because no actual rendering occurs at all; the image is read from preview.exr and immediately tone mapped to screen.
Tweak parameters and re-render again, until satisfied.
Re-enable any photons or final gathering.
Turn off use_preview.
Voila - the tone mapper is now tuned.

...but when i re-rendered i had this result.

Can you explain please how to get tonemapper working and what i did wrong. Thank you

[djx]

When you create the preview image you need to set the framebuffer to 32bit float and batch render it to HDR or EXR format (or command line). Dont just render the initial preview image to the render-view window and save it, or it will be saved as a normal 8bit LDR image and that wont be any use.

-- David

[living3d]

Thank you! I just didn't use batch rendering :) . Do you use imf_disp to view images? Why in imf_disp utility .exr file treated as unrecognized format but can be displayed? Why fcheck can't read OpenEXR? I have this error:
// IMF error
tonemapping.exr : (10) broken pipe

[q_vazk]

Did anybody find out how to retain the environment when rendering to exr?

[avinashlobo]

Hey, avinashlobo,

I got a question for you. I have been trying to get multi-channel OpenEXR from Maya and only successfully got it when using puppet's p_shader. Without using p_shader, I knew I can render out 32 bit EXR image using Mental Ray, but whenever I load the render into Nuke, it's not like multi-channel or even not more than RGBA - 4 channels. So, I am wondering how did you render the multi-channel EXR from Maya? Thanks. :) Hi, sorry for the delayed response. I'm using mia_wrapper with ctrl_buffers to get a multi-channel EXR. I haven't tried Puppet's shaders. Also, I'm using After Effects CS3 with this plugin (http://www.fnordware.com/OpenEXR/) and not Nuke. I'm having a whole other issue there. The channels names show up fine in AE, but I can't get any of them to display anything. I know the data is in there, because I can see them with exrdisplay (http://www.fnordware.com/OpenEXR/OpenEXR_viewers_win.zip), but it just isn't showing up in AE. Hmmm... :shrug: I've not given it much time yet though, so hopefully after some more digging I'll find a solution. I'll give Puppet's shaders a go as well and see if those give me better results.

Good luck!

[jasonhuang1115]

Interesting! :bounce: They use the EXR image from Gnomon's Nuke DVD. That's where I notice how powerful the multi-channel EXR is in compositing and push me to find the way of rendering multi-channel EXR from Maya with Mental Ray. I did some research and found that, to date, it seems I can only use 3rd party shaders such as ctrl_buffer and p_shader to get that. I haven't tried ctrl_buffer because it seems not update to support Maya 8 and after. For p_shader, I got the multi-channel exactly as I want, especially viewing that without any problem in Nuke. But the only concern is it's a custom shader, I can't use that with other Maya or Mental Ray shader. Thanks for those link. Really useful. :thumbsup:

Hi, sorry for the delayed response. I'm using mia_wrapper with ctrl_buffers to get a multi-channel EXR. I haven't tried Puppet's shaders. Also, I'm using After Effects CS3 with this plugin (http://www.fnordware.com/OpenEXR/) and not Nuke. I'm having a whole other issue there. The channels names show up fine in AE, but I can't get any of them to display anything. I know the data is in there, because I can see them with exrdisplay (http://www.fnordware.com/OpenEXR/OpenEXR_viewers_win.zip), but it just isn't showing up in AE. Hmmm... :shrug: I've not given it much time yet though, so hopefully after some more digging I'll find a solution. I'll give Puppet's shaders a go as well and see if those give me better results.

Good luck!

[avinashlobo]

Yeah, it's unfortunate that there's no native support yet in Maya's UI. Till then, I'll continue using these fantastic 3rd party shaders.

Here's hoping Maya 9 will provide full in-built functionality for this. :thumbsup:

[Gal]

i've said this a few times before and i dont understand why people dont try it out.
GUYS load your 16/32 bit images in SHAKE! and use the lookuphsv node to tone map it..it's a curve tool! very powerful control unlike the linear bullshit you have in photoshop. so far it's the best tone mapping tool i've found.
here's a small pdf tutorial i did a long time ago: http://employeepages.scad.edu/~kwitte/documents/Info_Sheets2/Roiter_Tonemap3D_infosheet.pdf

[q_vazk]

Great!
Thanks a lot! Simple and straightforwar...

[MaNdRaK18]

...
GUYS load your 16/32 bit images in SHAKE! and use the lookuphsv node to tone map it...

Do You know what would be equivalent node in Fusion?
Does anyone knows?

[living3d]

Damned... :scream: I have a Windows platform computer with Shake 2.5 version (the oldest for XP). Unfortunely, it doesn't support OpenEXR. I use PS CS2 for tonemapping...but seems its not the best idea. Also, I have NUKE 3.2 on board which I have never tried before.
So maybe someone who is good in NUKE can explain how to use this undoubtedly great program as a tonemapper. Thanx. :)

[Gal]

cant help you there never had access to nuke but you dont have to render to openexr. you can render to 32bit tiffs and shake 2.5 does take those(i also dont run a mac/linux and stuck with the old pc version) hard drive space is cheap for the end user.

[living3d]

Thank you for a tip, I'll try this. As I had heard 32-bit floating-point TIFF is provides excessive dynamic range values for CG, that is why its much memory consuming than OpenEXR.

[Gal]

actually you have a point there, i havent yet but i was planning to test render different formats to see the impact on rendertime, i know just by using 32bit tiffs rendertime increases by quite a bit. what about 16bit tiffs? try that

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