As a continuation of experiments with linear work flow and now EXR rendering output I have put together a more extended version as there are a lot of settings to get right.
I have collected the settings below without much explanation as there are plenty of explanations on the web that will do a better job than I. The purpose of this is to get you up to speed quickly with both with settings we’ve found work fairly well.
Bear in mind your renders may appear less contrasty than usual due to the more efficient spread of light within the scene. Don’t worry about this as it will give you increased flexibility in post-production (Photoshop, Fusion, Shake, After Effects etc) to adjust with S curves or contrast adjustment.
SETUP OF LINEAR WORK FLOW
Firstly calibrate your screen with Gamma 2.2 and 6500K.
In 3DSmax click on Customize> Preferences and click on the Gamma and LUT tab. Change the following to 2.2:
Then under render scene dialog under the vray tab>colour mapping change the following:
LINEAR PREVIEW AND EXR
You must then use the built in vray frame buffer rather than the standard render window to view the results otherwise you will not see the product of using linear work flow.
Again go to the render scenes dialog box and open the frame buffer tab. Tick use built in frame buffer and render to raw image file.
If you browse it will automatically put in a vrimg extension; change this manually to exr, otherwise you have to batch process them; which is silly when you can change it here.
Any render elements you have selected will now be contained within this EXR file, you do not need to output seperate render channels (except if you want tga copies).
So from now on you do not need to use the standard “save as” under the common tab, just work through the vray frame buffer tab to save files.
Please watch out however that if you send off a network render or continue after doing test renders you must uncheck the “render to vray raw…” otherwise it will overwrite this without giving you any warning.
VIEWING EXR FORMAT
If you output exr files with multiple render elements such as lighting shadow, GI zdepth etc you will be able to open them in programs like Shake and Fusion just fine. They are also 32bit images so will contain huge range that allows you to adjust exposure etc on the fly. Incredibly flexible!
Photoshop and After Effects however you will need ProEXR (www.fnordware.com/ProEXR/). The standard openEXR format in Photoshop will not bring the passes in correctly so will have to rename this to .BACKUP or something Photoshop will not understand so the proEXR plugin is used instead. See image below:
The location and extensions are shown below: There are also a number of shortcuts that will arrange the layers differently and cut alpha channels in certain ways as found in the ProEXR manual (www.fnordware.com/ProEXR/ProEXR_Manual.pdf)
October 5th, 2009 at 7:01 am
Hello James . nice tutorial. thanks for sharing.
personally i was looking for an answer about how to avoid image clamping when i output EXR using standard scanline renderer. If you have a solution that you can share i will really appreciate it.
thanks!
October 21st, 2009 at 8:15 am
Why would you want to clamp to 1.0? Doesn’t that defeat the purpose of using a float format like EXR?
October 25th, 2009 at 9:26 am
Yes if you use clamp output, you will break your linear workflow. You could save in tga and it would do the same. If you want to be linear you need to uncheck clamping. You should also put gamma to 1.0 and in place of it use srgb in the vray frame buffer. That way the image would be linear, only the display of the image would be adjusted temporarily in the frame buffer in order to better view it for adjustment.
October 25th, 2009 at 9:50 am
Yeah I think you’re right on this Strob. The VRay buffer can automatically adjust for that gamma output of 1 and adjust it so it’s like you’re using 2.2 if set to sRGB at the bottom of the window.
The method I went over “bakes” the gamma at 2.2 so when you open it in Photoshop or Fusion/ Shake etc it will look right. If you want truly linear though, the gamma of 1 should be carried through to the post stage and corrected there… if I understand that correctly. But you need time to comp it properly if you do that, and we found it was just being forgotten in the madness at the end of a project, so just baked it in in the end. ;-)
I checked the VRay manual in respect to clamping the output, and it just refers to ranges that exceed pure white, or (255, 255, 255). So if you don’t check this you might find you get un-antialiased highlights and pure white boxes of pixels. Not desirable on any render. This is why it’s best to check this; or so I understand.
October 25th, 2009 at 10:07 am
Hi bill.
The purpose of using 32bit EXR or 16bit tiff type format is to provide more range within the render from pure black to pure white, or 0, 0, 0 to 255, 255, 255. Within an 8 bit render you have around 16.7 million colours, or 255 x 255 x 255. Which is usually more than enough.
But say you have a gradient of a sky as a reflection which is quite bright and subtle, and has a range from blue-almost white to just white. Within this gradient you have limited colours from the 16.7 million, so if you start pushing it with curves in post (Photoshop/ Fusion etc) then it will start to band, or you’ll see the colours segment quite clearly (try it in Photoshop with a normal 8 bit jpeg on a sunset).
A 16 or 32bit image gives even more colours than the 16.7million in an 8 bit, and means you can push those subtle gradients a lot further in post without destroying the image and getting banding. Hence why compositors love these EXR’s… apparent from their size of course which slows down work flow.
Clamping output just stops values extending beyond full white (255, 255, 255), so doesn’t really affect the range as above. If VRay is extended beyond this it tends to display as square pure white pixels as it can’t anti-alias this range beyond white. The VRay manual has a good explanation of this which I should put here actually; when work stops consuming all my time! ;-)
I hope that helps and clarifies.
February 3rd, 2010 at 9:57 pm
Hello James
Ive stumbled across your blog many many times while trying to learn 3d techniques; thanks for being such a valuable resource.
I have been trying to migrate over to the EXR format and am getting it pretty ok except when using the Vray render element VrayBackground– problem is it doesnt show anything in the exr file. It is there, but there is no sky. am I doing something wrong or misunderstanding what the VrayBackground element is supposed to be used? I shows up when the image is saved as tiff, etc., If i could get some help figuring this out i would be in heaven.
February 20th, 2010 at 7:49 am
Ha ha nevermind. i figured it out. you need to press Alt upon opening of the file to trigger the option to break out the alpha.
March 14th, 2010 at 11:47 pm
Thanks for sharing this nice info, you say it’s a MUST to use physical camera, how is this? the lwf doesn’t work with normal 3ds max cameras?
The settings of camera are missed? i read ” physical camera (settings below)”…
Regards,
March 15th, 2010 at 10:00 am
Hi Pep,
Actually you don’t really have to use a VRay physical camera. We have found though that the light bounce is slightly more reliable when running your sun at 1.0 multiplier. Apart from that lwf should run independent of that.
I will edit that particular section out above as not to confuse.
For more info on VRay camera settings look here… http://www.jamesshaw.co.nz/blog/?p=156
Cheers.
March 18th, 2010 at 3:37 pm
Interesting, thank you very much for the reply. I’ll check the other post.
Best regards.
May 21st, 2010 at 2:40 am
Thanks for this. very informative. My question comes in how you then do post work with these layered exr inside your post app. I try to work with as high a depth image as possible yet the company work for we restrict our depth to 8bit so currently render out multiple tifs through the G Buffer. How do you then work with these 32bit or 16bit half float exrs inside photoshop, when so many filters and adjustment layers are disabled. Or do you simply always work within composting software that allows complete manipulation?
May 21st, 2010 at 11:56 am
Hi Myles,
CS5 is supposed to come out with better support for 16 and 32 bit images. In the meantime 32 bit image support is very poor with a simple exposure control and that’s it, and 16 bit does do away with a number of controls within Photoshop. However 16 bit is still usable with this functionality, and allows you to push images much much more, essentially equivalent of working with a RAW image our of a camera (although this is actually 14 bit).
True 32 bit support is in the league of composting software such as Nuke and Fusion etc. But this truly floating bit range isn’t entirely necessary especially in our line of work. You would have to be pretty high end to need this range and afford the resources to run these huge files efficiently.
So in short use 16 bit instead, and outputting to different tga or tiff channel files is probably a better option than lumping them into an EXR file. EXR files are only really useful with hundreds of frames, where pulling in one node in Nuke is more convenient than multiple individual passes. Because of the lack of linking passes in Photoshop, the time saving is limited.
May 24th, 2010 at 12:34 am
Thanks James,
Great info. We’re getting cs5 shorltly so we’ll see how that plays out. Your right for our line 16bit is definately enough. Keep the tuts coming along.
July 28th, 2010 at 10:37 am
hi i ve been working with gamma 2.2 settings and openexr format, in color mapping i put gamma = 1.0 so i get a gamma 2.2 in the openexr output file, BUT the problem is that when gamma is NOT added from the beginning in the colormapping rollout i get alot of noise. the problem is that adjusting gamma to a value of 2.2 outside the colormaping rollout will cause issues. is there a way to add a gamma2.2 in color mapping and get the same output in openexr, btw i tried changing the gamma value back to 1 in photoshop by adding a value of 0.45 in exposure control, but for a strange reason my composting technique ended up looking very strange…. i think the solution would be for exr format to use the gamma 2.2 added in color mapping and not add a gamma 2.2 to a gamma 1.0 rendered image. anyone has a solution? plz it would be a great help if u do
July 28th, 2010 at 10:50 am
Hi Visual3D,
Yeah we had the same problem in the office, but have solved it now with the following.
You must put 2.2 gamma under colour mapping, and this will bake 2.2 into the render in preparation for Photoshop. And in Nuke etc make sure you work in a “none” environment rather than “sRGB” or “Linear” etc. Otherwise you’ll double gamma your images.
This affects the way Max actually thinks about lights etc while compiling the output. Rather than a long winded explanation I’ll just say it doesn’t work so well carrying 1.0 gamma into PShop etc; it will give you a lot of noise. Best to do this step out of the render window.
The other thing are you using the VRay buffer window? You must use this. And MAKE SURE that the little sRBG button isn’t checked at the bottom. This puts a correction of 2.2 gamma on the render, which you’ve essentially already done in the colour mapping.
Let me know if this works for you and let me know if it doesn’t! We’ve tested it on a multitude of jobs and only work in linear now with EXR’s and it works sweet with the above setup.
July 28th, 2010 at 11:58 pm
ok i dont know how to work in a “none” environment in photoshop. ok i ll explain my workflow: i use linear color mapping in vray and put gamma value of 2.2. i render elements like diffuse, gi, reflection..etc etc, i use vray frame buffer and check render to vray raw image file, and change extension to .exr, since i use gamma 2.2 i dont need to put srgb on frame buffer. that way i ll have an exr image with all the render elements as layers ready for compositing. so i assume it s photoshop that s adding another gamma correction to my exr image? so if u can explain to me how to work in a “none” environment in photoshop?…
July 29th, 2010 at 8:53 am
Hi visual3D,
Sorry the “none” refers to Nuke, if you were to do comping in there. Photoshop doesn’t give you a choice, it just works in a fixed gamma space of 2.2 or sRGB. Let me check some more things…
Where are you saving out of? Are you saving out the exr through the frame buffer tab? Like “save RGB”? If you save out of the normal “save as” dialog, it’ll double gamma it.
The other thing I can think off is are you saving all these passes in one exr file? If so PShop doesn’t like that. It’s best to go through the 2nd save as in the VRay frame buffer tab (where “save RGB” and “save alpha” is) and render out separate exr files for each pass.
And the last thing I can think of is are you outputting 32bit exr’s (full-float)? If you are PShop doesn’t support this and will use it’s completely useless exr 32 bit importer, which will wash it all over the place (I have heard rumours CS5 now supports, but am dubious). When compressing (under options when saving the exr) chose 16bit (half-float), which PShop can handle just fine.
I hope that helps, let me know if any of these options solve the problem and we’ll go from there!
July 29th, 2010 at 11:03 pm
hello,
i do exactly that way, but when i open EXR in PhotoshopCS5 – all the channels are overbrighted and i need to correct exposure 0.45 to each of them, which is not very comfortable each time. actually in Adobe Bridge EXR thumbnail displays in correct gamma – so is there PhotoshopCS5 problem?
July 30th, 2010 at 2:01 am
thanks for ur help James, well first about CS5 it has no special control over exr files, i m still using proexr in CS3, yes i save all the passes in one exr file, actually vray does but of course not from the vray frame buffer, anyway i got tired of trying stuff in photoshop, i found the fastest way is to disable color mapping correction in render elements, so whn i open the exr file in CS3 the RGB image layer looks gamma corrected twice but thats ok cz i dont need it, i simply need to composite my elements layers, and they look fine. gamma is correct. the good part is that after blending they look ok, lets say 98% like the original image which is very fair and a good start for comping…and most importantly no noise in reflections layer which i find strange lol “since they r gamma corrected in ps” but who cares as long as they dont have noise and they do the job. It s frustrating how adobe still have issues with exr files, i m giving up on photoshop, me getting fusion or nuke soon they r way more compatible…
August 14th, 2010 at 12:30 am
As far as i know, with these steps, saving in HDRI (.exr..) we are applying twice the gamma correction so we would fix this in PS with Exposure > gamma correction > 0.4545 (inverse gamma).
Another option would be to check “Don’t affect colors” so that the correction would be applied once (always supposing we are with HDRI)
Correct me if i am wrong please
Regards,
August 14th, 2010 at 12:36 am
Another issue that is not easy to read about is the one talking about the correction of simple Vray materials, this is, flat colors, as i read here_ http://www.scriptspot.com/3ds-max/plugins/autogamma those materials are not affected by our settings above, so is we use them have to apply individually the gamma 2.2, using for example de color c. plugin…
p.d.: sorry for the second post