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Post production
show user profile  mike_renouf
Hi all,

I've never had any real tuition on post production techniques, and I'm just delving into this subject to try and improve my renders.

Question is - if I output a png file from the framebuffer after applying exponential colour mapping, does this have 16bit colour depth or is it only 8bit?

I have found that my preferred method of working is to try and get as much set up correctly in max as is possible, and to do the minimum amount of postwork. Also, I hate long render times. For these reasons I'm veering towards using exponential colour mapping in vray. My understanding is that this gives a "what you see is what you get" output, but with shorter render times than the full linear 32bit output.

Would be great to hear any corrections or feedback on this!

I came across this great video with some post processing guidelines, though the guy does skip through things a bit fast and without much explanation:

read 553 times
12/11/2014 2:14:56 PM (last edit: 12/11/2014 2:14:56 PM)
show user profile  reeves1984
Technically, colour mapping (tone mapping) only applys a 'look' in the framebuffer. When you export that as an image, you then have the choice of burning that in or not.
Explained here:

I don't know if saving as a png saves as 8/16 bit, when you have the save as browser open isn't there a setup button to let you choose?
I never save from the framebuffer, always from the output path in the render options (for consistancy when doing animation or stills) so thats where the format and bit depth is chosen.

Compositing (which would be what we refer to it as, even if not combining elements) is very practical because of the different type of control and speed you get, I would do it on ALL 3d renders and could not recommend it highly enough.

Sure make everything as close as you can in 3D, but many tasks are so much quicker and easier to deal with in 2D/comp thats where they should be done.

Simon Reeves - VFX Artist & Blog
twitter <-- I work here

read 525 times
12/11/2014 3:51:01 PM (last edit: 12/11/2014 3:51:01 PM)
show user profile  9krausec
Here's a thought about post production that doesn't answer any of your questions. :D

I figure this. To do minimal post work and be able to pull more out of your renders (at a very basic, nonspecific level... for stills) is pick some basic render elements (AO, MaterialID, Normals) and then have those turned on for all your production renders.

Get your render as an OpenEXR (it is so amazing to have all passes stored in one file). Then open in PS. All layer elements open together and also have the same names all the time (alpha is always "[A]" RGB is always "RGB" ect...). You'll need ProEXR plugin to open it this way in PS.

Then create actions that process your renders in a way that gives you slider options for exposure of certain materials you use frequently or a blanket curves control to pull contrast out.

Then if you reuse materials (with same material IDs) and generally find yourself rendering out your scene using the same workflow. You can just open exr, click a button, create a comp and modify any adjustment layers to fit the scene.

That's what I'm shifting towards for product renders. Love it. Consistent and it kills on manual work. You can make this as complex or simple as you want. At the end it's RENDER>PS>ACTIONS>LIGHT MODIFICATION>MONEY. All about getting a system down.

- Portfolio-

read 524 times
12/11/2014 3:51:12 PM (last edit: 12/11/2014 3:51:12 PM)
show user profile  mike_renouf
Wow. Thanks for the detailed replies gents. I've got a lot to learn on this aspect.

Reeves - I like your idea of saving from the output path. Once or twice I had losses of renders when my pc decided to reboot over night and I hadn't set it up to save automatically - I'd just intended to save what was in the buffer when coming back to my machine in the morning. Your method would have saved that misfortune.

Krausec - ProEXR sounds cool. I'll check it out. You kinda lost me on the last part about reusing materials, but I'll have a re-read..

Can you recommend any video tutorials - free or paid, either is fine. If I need to invest a few quid to learn this stuff then I'll fork out.

read 512 times
12/11/2014 4:38:55 PM (last edit: 12/11/2014 4:38:55 PM)
show user profile  9krausec
I meant like reusing materials so you have the same materialIDs. Should of been more specific. So then you can make masked adjustment layers in PS automatic like by using the color range select function.

So then if you have material like chrome. That may change dramatically in differing environments. And you want to add a curves adjust just to the chrome on ALL of your renders. Keep the material ID the same color and then color select all of that color range from the MaterialID layer.

If that makes any more sense, lol.

- Portfolio-

read 507 times
12/11/2014 4:59:21 PM (last edit: 12/11/2014 4:59:21 PM)
show user profile  reeves1984
also dont forget nuke has a free non commercial version

and fusion

much nicer than using potato shop

Simon Reeves - VFX Artist & Blog
twitter <-- I work here

read 491 times
12/11/2014 6:34:54 PM (last edit: 12/11/2014 6:34:54 PM)
show user profile  9krausec
^I need to get fusion. Would rather go with Nuke Free, but I'd be using it for commercial purposes. Pooo.

- Portfolio-

read 487 times
12/11/2014 6:47:58 PM (last edit: 12/11/2014 6:47:58 PM)
show user profile  mike_renouf
Looking back at your first response Reeves, I think I might have become confused or not explained well enough. Maybe I'm tripping over the whole LWF vs gamma 2.2 workflow.
What I meant is I've been playing with both options and rendering using a gamma 2.2 output in the vray framebuffer, sub pixel mapping turned on. This gives a quicker render I think but without full 32bit colour depth.
As far I understand..
These renders don't have much contrast in so need a bit of balancing in post.

I had no idea I could try out something as cool as nuke for free. I'll investigate further. It's very strange though, the version of max I use came with Autodesk's Composite, but it seems no one ever talks about it

read 475 times
12/11/2014 7:55:49 PM (last edit: 12/11/2014 7:55:49 PM)
show user profile  mike_renouf
Clayton, thanks for explaining more. I think I remember seeing a Wireframe Color pass or Gbuffer that can be set up to do what you described. I've just never taken the time to really explore that. I'll have a stab.

read 472 times
12/11/2014 8:01:44 PM (last edit: 12/11/2014 8:01:44 PM)
show user profile  Garp
If I remember correctly (someone correct me if I'm wrong), the renderer always outputs 32-bit values. It's the file format you save to that keeps it or brings it down.
The .vrimage format - straight render output - is (used to be?) 32-bit. It's been a while, so things might have changed.

As for comp, since I'm lazy, I always go for the same routine. What I want out of the renderer is not a pretty picture but a bunch of elements that are clean and correct. All in linear color space. Then comp is easy and gives maximum freedom.

read 471 times
12/11/2014 8:06:44 PM (last edit: 12/11/2014 8:06:44 PM)
show user profile  mike_renouf
Right... I was hoping that I wouldn't get confused over the gamma issue in this thread but I think I've failed there.

I'll have to go off and read everything again :o)

I think you're right about the buffer always saving 32bit Garp. I think where I've saved time by using an alternative to full LWF is by using tonemapping to create clamped values instead of superbright whites etc, as those take a while for the antialiasing to resolve.

anyway... all that aside, its good to hear people's differing methods and some thoughts on post processing.

read 460 times
12/11/2014 8:43:11 PM (last edit: 12/11/2014 8:48:21 PM)
show user profile  9krausec
I know that I try to run LWF (as I understand it) and exporting as 32 bit EXR usually always needs a contrast bump in post. Mr.Bolts explained to me awhile back that adding a Exposure adjustment layer, putting the gamma to ~.9 and adjusting the actual exposure helps make things pop some more.

Need to usually add an S-Curve in PS too for added contrast. Also I may be doing things completely ass backwards! Glad I could help a little bit!

Edit: I would like to hear what other folks have to say in regards to lack of contrast when exporting 32 bit from a LWF type setup.... I just make the contrast bump in post, how many other big sluggers here do that too?

- Portfolio-

read 455 times
12/11/2014 8:50:33 PM (last edit: 12/11/2014 9:04:06 PM)
show user profile  BishBashRoss
In VRay the frame buffer is 32 bit unless you use the clamp output options. That's how I understand it.

My workflow is linear - EXR - Photoshop.

read 425 times
12/11/2014 10:29:57 PM (last edit: 12/11/2014 10:29:57 PM)
show user profile  ijzerman
I sometimes render a vray extratex in the render elements with a dirtmap so i can apply some extra contrast without fidling with the image too much. I multiply it over the original.

Pushing buttons since "86
read 406 times
12/12/2014 9:50:05 AM (last edit: 12/12/2014 9:50:05 AM)
show user profile  BishBashRoss
I've started to experiment with a new technique for managing my files in Photoshop. By loading up all the 32bit files in there own smart object you can retain the dynamic range and compositing options while working in 16 or 8 bit in the main file. Downside is you can end up with huge files but it's great to have everything organised together like that.

read 396 times
12/12/2014 12:12:13 PM (last edit: 12/12/2014 12:12:13 PM)
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