Dino Diner Volumetric Lighting

This week I have been looking into different render solutions for volumetric lighting in 3D.

I have been working with Arnold to create some basic lighting with a previs model for the cave created by another student.


It was only a quick render, whilst I felt this worked OK the volumetrics were quite noisy and added a lot to render time.
I am confident with adding them into 2D space with Nuke but had not added them to 3D successfully yet, so they work with a moving camera, so this is what I wanted to look into doing with Nuke.

I found a good toolset with the TX_3DRays gizmo from Nukepedia.
This allows quick creation of a light shaft which you can positing within 3D space, by reading in the geometry I could also use it as a holdout so the volumetrics sit properly within the scene.

Using two slightly different workflows I created the two images below, which have slightly different looks.


I prefer this first image as the result is more subtle, and it matches better with some real life reference images.


The effect here is much stronger, I used a different noise pattern to generate the volumetrics which has created something that seems more dense. This was rendered with a Depth to Points technique, which I go into more detail with here.

One problem with both is that I turned off the lighting from the original test image, so not only is there no volumetrics in render but no diffuse from those lights, so with my moving test I will include the extra diffuse and match the volumetrics shafts to where those lights are.

Here's the node tree for the top image.


The next step was to try this with a moving camera, to check that the way the volumetric was generated works by default from all angles or if it will need to be tweaked on a shot by shot basis.

I think the result is pretty promising. This time I tried to match closer to the original Arnold render I created which I think helped. I was able to export indicators for where the lights were from Maya into Nuke so lining the volumetric shafts up was easy, and the result is pretty close to what I had in Arnold.

 The main issue I ran into was in render times. Having 5 separate shafts really boosted the render and preview time in Nuke. Although 20 minutes to render the sequence from nuke is far better than any time added to the render of each frame.

 I will be testing the same scene in Renderman now it has been released and will have a look at the workflow for Volumetrics there, which works more similarly to what I have been doing in Nuke.

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