Do you Comp GBuffer channels for Arch Renderings?

[mfured20]

Hey guys -

 

I was thinking about trying to master comping various channels in post, a la Chris Nichols [ http://chaosgroup.com/forums/vbulletin/showthread.php?t=32485 , or for those without access, merging reflection, specular, refraction, gi, etc in post], but I am not really sure about what applications it would actually have in my work. I tend to do fairly straightforward interior scenes, not overly photorealistic, but decent enough in their own right [see attached]. I am not really worried about the time and money aspect of the learning process, but I doubt I would actually use it.

 

So my question is, do any of you guys go to this extreme? And what kind of work do you do with it?

[mfured20]

hm, i see.

 

i wont bother with it until i start doing ubersweet animations then.

[Nic H]

i use render elements alot, but also save out a 'full render' in case i cant be bothered doing all the layer compositing / modes. if you are doing this in photshop get ProEXR, its lets you ahve multi layered exrs in photoshop.

 

the other alternative is to use the passes and jsut screen / multiply them over your base render to improve reflections/isolate specular/and put in DOF, distance fog. Vray Exratex (with a vray dirt material) lets you do quick ambient occlusion / dirt passes as well.

[Spacelord]

Wow Go Nic, I never new about pro exr !!

I've been waiting for the next photoshop hoping they would have multi channel exr's.

[mfured20]

Hey Nic -

 

Thanks for the info... I downloaded the trial of ProEXR, and I am playing with it, but I think that I am doing something stupid. I can't seem to export my exrs in a multi-channeled way. I have tried saving all of the channels to the same file that I save the rgb image itself to... ha, I have tried so many variations that I'm not sure I can recount them all.

 

I guess my question is... How should I set up my output [save as] files? Or, if the way that I have sketched out in the attached images is correct, did I miss some button somewhere that I should tick off?

 

If you get a chance to holler back at me I would greatly appreciate it. Thanks!

[mfured20]

ah-HA! I have discovered a channels/attributes button in the .exr save dialogue, but when I open it up, hoping to find a link to Vray Render Elements I find nothing. Is there supposed to be something here, or does this have nothing to do with the way that VRay saves out its multilayered exr images?

[Nic H]

hey matt what you need to do is save it from the vray frame buffer dialogue.

where it says vrimg, you need to change it to .exr

 

Its a bit weird having to do that but it will give you your multilayered exr.

 

you dont need to save using the normal save dialogue either (unless you want a tga / tiff as well), as you might be inadvertantly savign over the exr from the vrimg dialogue.

 

hope that makes sense!

[mfured20]

Hm, my confusion remains.

 

I tried to save out from the VRB render window [the save icon in the top bar, between monochromatic button and the clear button], but it didn't change. I can add extra channels from it, sure, but not the ones that I want. When I go to add the extra channels, the Vray Render elements don't show up. Is there something else that I need to adjust to make them pop up?

 

Or, alternately, did you mean that I should go to the 'V-Ray:: Frame Buffer' dialogue within the Render Scene Dialogue? When I go into it, there is no option of .exr, only vrimg. But I don't think thats what you meant.

 

I appreciate you taking the time to reply to these questions; its always nice to have someone to ask about specific things, rather than broad overviews from publications. Thanks!

[Nic H]

yes sorry i mean you need to manually type in .exr instead of default vrimg in the save dialouge for vrimg.

 

its weird i know.

[mfured20]

ah HA! i will try it as soon as i get a free moment. Thanks!

[mfured20]

Hey, it worked! At least, it works for smaller renders. My 1000px renders work well, but when i try to save out 3000px renders I get this error message:

 

error:[VFBCore::SetRegion] Error writing render region to raw image file. [ExrFile::WTRegion] Error writing tile to .exr file

 

not really sure what this is about, but it seems to not like me much at this size. I will try another few tests to see what I can find out, but in the mean time, what is the max size renderings you do with this workflow?

[Nic H]

hmm thats funny. do you have plenty of RAM? We render up to 8k(w /8gb ram) with no problems saving straigh to exr.

 

there is a utility called vrimg2exr that might help you, it takes the vrimg and...turns it into an exr after the render, saving memory.

 

also try disabling 'render to memory frame buffer' in the Frame Buffer rollout

[mfured20]

I actually only have 4 gigs, but with the switch running. I have never had any issue before.

 

I already found the vrimg2exr deal, and while it is a lot easier than me trying to use the tool that comes with vray, I seem to be really stupid about using it too. I haven't gotten it to work successfully, altho I will admit that I didnt try very hard. [if anyone needs the app, the website is http://www.binka.biz/?Download ]

 

I searched the ChaosGroup forums and found a couple of people that had the same problem, and vlado had no idea what might cause it [besides maybe a networking issue].

 

oh, and clicking off the 'render to memory frame buffer' just causes max to crash when it hits the end of the rendering and tries to save.

 

I have no idea what is going on. Its definately not critical, and my real work seems to be waiting for me this morning, so I might have to revisit it at a later juncture.

 

Thanks for all the help, I really appreciate it.

[mfured20]

Just a followup if anyone else is having this problem:

 

"This is most likely due to saving the file over the network - e.g. I remember someone else on the forum found that his network cards had a power saving option that turned them off after a certain amount of inactivity as can happen with a long render. I have not yet gotten round to changing how the files are written; further on, I can only do that for .vrimg files, not .exr ones.

 

Best regards,

Vlado"

 

I think that I can support this conclusion; It only happens when I am working with DR files; files on a single computer don't have any issue saving to multilayered exr. This leads me to believe that there is an error communicating across the network, some info lost along the way. I have noticed that, to this juncture, the vrimg files always write [thanks vlado!], and the exr files often do not.

 

I have only found two other people that have had this issue, also indicating a problem with some individual's hardware as opposed to a software glitch.

 

Next step: attempting to see if one of my slaves is causing this problem through process of elimination; try each one with DR, to see if it crashes on all of them, or if it works with one or more of them. perhaps its my workstation, who knows?

[Nic H]

we have the problem with DR over network not saving multilayered exrs as well.

[Dave Oliver]

im not doin it right

 

i just saved the channels as jpegs. i already had to 2.2-gamma them in photoshop.

 

my main question, what does the 'plus' mean in his workflow diagram? after i multiplied the layers together i had to put each layer set on lighten to get any results.

 

other than the lack of background and specular (which doesnt make much difference), it still looks kind of off

 

[pg1]

hey dave 5264

the plus sign is for additive

Many programs have an additive blending mode (after fxs for one) but in photoshop they decided to called it linear dodge.

We output elements for a lot of our work these days but none more so than multimatte element

Tried proexr for a bit but found it to be very slow for after effects.