Week 10 Maya Lighting, Arnold AOVs and Nuke Compositing

For week 10, the team divided into two segments. Matthew, Sorcha and Andrew focused on the animatic while Kerry and I focused on trying to recreate the house scene exterior. I blocked out the scene trying to match the scale and perspective/focal length and composition of the concept and then shared the project with Kerry. Kerry focused on modeling the house and bridge while I focused on modeling the trees and testing the lighting, rendering and compositing.

 

I was having trouble getting the Z depth pass from Arnold to work in Nuke so this first render test was created by rendering the geometry in separate render layers in depth and then manually adding the atmospheric depth on each layer in After Effects. This resulted in a lot of control over the layers but created more work in setting up different render layers. I think that ideally we’d want a lot of control but not as many separate layers.

 

 

AOVs and Nuke

I was loosing hope in using the Z depth pass. I had got it working before by grading the Z pass in Nuke so that it was visible in the viewport but hadn’t tried it in a long time so was missing a step. Alec as usual was lots of help!:) He went through an Arnold to Nuke workflow with Kerry and I and showed that the Z pass could be read by a zDefocus node in Nuke for simulating depth of field. Alec also showed us the benefit of having separate AOVs that could be edited in Nuke.

Andrew shared this video from Arvid Schneider’s YouTube that goes through the same process of rendering multiple Arnold AOVs into one merged EXR file and then extracting and recombining these in Nuke with shuffle nodes. This video also shows how to use the Z pass to create atmospheric perspective (finally!). The Z pass needs to first be extracted from the merged EXR and then the depth channel 0 to 1 space needs to be normalised by grading the white and black points with values from the clipping plane (if I understand that?). Schneider also shows a useful way of creating a custom AOV for material IDs using the aiWriteColor utility.

Arvid Schneider MtoA 120 | AOVs for Comp | using Arnold with Maya 2017

 

 

It took me a while to understand the different steps in this workflow. This page has useful information on the different sets of passes/AOVs that can be used to compose the beauty pass.

https://support.solidangle.com/display/A5AFMUG/AOVs

Nuke swapping channels

http://help.thefoundry.co.uk/nuke/11.0/Default.html#comp_environment/channels/swapping_channels.html

I got the composite working for a simple scene with spheres. Alec showed us a possible method of creating light bloom by rendering a rim light in Maya with the indirect light turned off and then blurring this in Nuke to get a soft light halo effect. I added a separate render layer for the rim light’s direct light as I can’t yet figure out how to render different lights into their own AOVs with attribute overrides. Creating light bloom needs to be further looked into. Alec had advised to work towards making rendering and compositing templates that could be used as a base across scenes.

 

Alec suggested pushing the atmospheric fog and cinematic composition even more, as in the last image. I also made the mistake of making the depth of field too strong so that it looked like miniature photography. Sorcha pointed out that dof should be used for objects close to the camera. I had a feeling that this was the case but I haven’t experimented much before with where the blurring starts and stops with objects of different scales.

We haven’t started experimenting with any textures or shading yet. The light in the window is just a temporary Photoshop layer. Alec suggested creating light scattering with either environment fog or faked god rays wrapped around geometry with an alpha channel. The grass at the moment is also just simple Maya Paint Effects so this might change with the texturing process. The rain and fog are Photoshop overlays so will have to be looked into further also.

 

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