multi plane exr rendering

[sl0throp]

I am trying to figure out the pipeline for rendering multi-plane exr's...I see in the matra Rop where to add in my planes and some pre defined variables...I also have enough familiarity with Vops that I can understand a shader breakdown but I have no idea how to pipe the information into something that will break the shaders down to their respective passes and pass that data to the mantra rop and into the correct channel. Like I would like to break cf down to all its components and be able to reconstruct in chops or nuke as well as rendering the data channels, p pz n etc.

Also in the gamma settings does a gamma setting of 1 insure a linear light workflow.

Any pointers in the right direction would be very helpful.

s

[digitallysane]

I am trying to figure out the pipeline for rendering multi-plane exr's...I see in the matra Rop where to add in my planes and some pre defined variables...I also have enough familiarity with Vops that I can understand a shader breakdown but I have no idea how to pipe the information into something that will break the shaders down to their respective passes and pass that data to the mantra rop and into the correct channel. Like I would like to break cf down to all its components and be able to reconstruct in chops or nuke as well as rendering the data channels, p pz n etc.

Also in the gamma settings does a gamma setting of 1 insure a linear light workflow.

Any pointers in the right direction would be very helpful.

s

Check the material pallette, there are lots of materials done in VOPs which output their components, so you can study how it's done.

Dragos

[sl0throp]

I see how it is done in vops np problem but how do I pass that parameter lets say specular component and pass it into its own plane so it renders in its own channel.

[digitallysane]

Check the attached image. It shows the VOP network of the Decal material from the material pallette.

You can see how export parameters are used to export various shading components and then the name of the exported parameter is used in the Mantra ROP to create a plane in the EXR.

Dragos

[sl0throp]

Hey thanks a lot that is all that I needed. Really helpful.

s

[kensonuken]

I this something like physically its one exr file but it has multiple Image channels as well? Just like what it is specified in the OpenEXR specification? ( it can store 32 image channels )...?

[ihab]

I this something like physically its one exr file but it has multiple Image channels as well? Just like what it is specified in the OpenEXR specification? ( it can store 32 image channels )...?

Yes that's exactly what happens when you output different Arbitrary Output Variables (AOVs) to the same exr image. you can specify the quantization of your exr file as 32bit Float. then you can out put your colors as vectors and your single channels (Pz, Alpha, Occlusion .. etc) as float. This will create an exr file with all the channels you need.

Cheers

[kensonuken]

well ihab thanks alot but I am using Nuke how do i extract those channels back?

[ihab]

well ihab thanks alot but I am using Nuke how do i extract those channels back?

Hey,

Actually i use shake so i might not be useful to you in that matter. But, i guess you can extract any channel from the exr image in nuke. In shake, you have a drop down menu that makes you load any channels in your R,G,B,A, or Z channel. It's a little limited than nuke as i heard.

Cheers

P.S. you can preview these channels in mplay. just look for a drop down menue in the upper left corner of the mplay window with "C" on it. mplay displays the color information by default (RGBA). simply select your channel name from this menu and it should be visible in mplay. If this pass contains multiple channels (i.e a vector or color pass) you can access individual components by choosing the RGB components.

Edited September 10, 2008 by ihab

[digitallysane]

well ihab thanks alot but I am using Nuke how do i extract those channels back?

By reading the Nuke manual, I suppose.

[kensonuken]

well my requirement doesnt end up there we are developing some viewer like framecycler which needs to read these image channels.. Ofcourse we can crack it how to do that by reading the exr specification. But It would be helpful if things are explained by somebody...

[symek]

well my requirement doesnt end up there we are developing some viewer like framecycler which needs to read these image channels.. Ofcourse we can crack it how to do that by reading the exr specification. But It would be helpful if things are explained by somebody...

There is really nothing to explain here. You need either an application that handles exr files (like Houdini) or freely available dev library, which you use to read and write OpenEXR files in your application and that's it. Search in internet for it (www.google.com or similar) and get started!

cheers!

sy.

[sl0throp]

Just as an FYI for the the Nuke guy...you can view the channels in the viewer just like you would RGBA but there will be additional ones and all the nodes have inputs for affecting only that channel. If you need to extract the data out of the stream, you can use a copy, or shuffle copy etc. Also check out the Nuke forum link below. Not all channels come in with values in range so sometimes you have to do something to the channel to be able to use it correctly most answers can be found there.

http://www.vfxtalk.com/forum/nuke-foundry-f60.html

s