Best way to accurately capture a complex shadow pass?

[thebeals]

I have been using the object properties flag and/or material wrapper to be able to extract shadow information to composite over a plate, but I've noticed in a recent project that it is not giving me the same result as the beauty render gives me. My assumption is it is doing this because it's not capturing everything.

What is the correct way to capture this complex shadow information to be able to composite over a different plate? Will I need to render the diffuse/gi/refl from the BG and then mask it somehow with a shadow mask and then multiply the result over the plate? Would that work, I feel like that might not be the right solution? What am I missing?

Below is the example of the difference I am seeing. Thanks for the help!

[dorkabilly]

Have you tried splitting your shadow out to its own render layer. There you could control the layer with an override of the geo's visibility to get a clean shadow.

[thebeals]

Hey, thanks for the response! I am able to do that, but I'm still not able to get the shadow to look the same as in the beauty pass. Any other thoughts?

[ricoholmes]

looking at your shot- it looks like a familiar problem from some time back (where the shadow is becoming brighter again where not at the edge). If I remember right, it can be cured by making sure shadow color wasn't pure black. (?) I haven't seen that problem for probably the last year or so, so assumed it was adressed.

[thebeals]

Wow, Ricoholmes, I think you are on to something!! I did what you suggested and changed the shadow color on the lights to a very small amount from 0 to .005 and got drastically different results. They results are much closer to the raw beauty-not identical yet, but much closer. I am still missing some of the blue bleed that comes from the transparent blue bubble things, and a little of the softness on the edges.

Here is the new result. Does anyone have an idea why this bug happens and if Chaos is aware of it? Also, any ideas on how to push it the rest of the way to get a perfect 1 to 1? I'm honestly quite happy and can fudge the color difference, but it would be nice to know how to get a perfect result.




Thanks Richoholmes!!

[vlado]

It really depends on what you are doing with the shadow pass after the render?

Best regards,
Vlado

[thebeals]

Hey Vlado! Awesome to hear from you!

For this specific example, I simply want to put the shadow over a different background that what it was rendered in (nothing crazy different though). For now, I have just been trying to put the shadow on top of the same value of background that it is rendered on. The background in render has a value of around 1.2 near the shadow so I brought the shadow layer into Photoshop, created a background layer behind it and filled it with a white value of 1.2 in order to try and match the look of what I get in the render.

If I can get the shadow in the beauty to match the shadow composited over the same value background in photoshop or Nuke, I will be super happy. Any ideas? Thank you!

[thebeals]

Bump

Any other thoughts on how to do this? Bumping the shadow so it is not pure black got me much closer, but not perfect. Is this a bug, if so does it need to reported? Is there a better way to accurately capture the shadow? Thank you!