Compositing with shadows

[danielarusso3d]

Hi everyone,
I have a little problem with the composition of a cocktail glass and its shadows in post-production. The customer asked me for an image saved with a shadow but transparently to manage the color as desired. The problem is that glass is naturally not easy to manage because it behaves in a certain way compared to the backdrop used during the rendering phase (in my case white). So I was wondering if there are correct settings to ensure that an infinite studio allows different background colors in post-production in objects made up of glass + liquids, or do they necessarily have to work on them?

Thanks in advance for your help!

[bnji]

Hello there,
From my POV, there are no "correct" settings but different approaches to accomplish the desired result.
You can always use a neutral-gray backdrop (infinite background) and combine it with the use of the Corona Shadow Catcher material.
I hope this helps.
If you need further assistance, please elaborate a little bit more on what is your approach to this and what is the expected result (provide as much info and references as possible to understand better the issue).
Kind regards.

[MircoTosti Studio]

Bnji this system does not work if transparent materials such as glass are used together with liquids.. example of a bottle of wine or a bottle of rum etc.
The problem is how to create a transparent background of PNG image to put on top of any product background like Bottles etc

[danielarusso3d]

Hi Benjamin,
Thank you for your answer! Yes, I used an infinite white background with the shadow catcher but as Mirco says it doesn't work with glass bottles. :(

[bnji]

Hi there,
All I'm saying that you can have different approaches to get the desired result, but it won't be a 1-click solution.
If you render out several passes and composite them together in your preferred image editing software, you may get closer to the desired result, all depends on your compositing skills.
Try out the attached PSD file and play around with it, it is a quick and a basic approach to this. Simply turn on the Hue and saturation adjustment layers and use the same color for both.
Of course, this can be perfected; again, it all depends on compositing skills, but you can get all rendering info (layers/passes) from Corona.
I hope this helps.
Cheers everyone!

[danielarusso3d]

Thanks Bnji, so it's pretty much what I imagined.Thank you! :)

[BigAl3D]

The client is asking for something nearly impossible in the fact that placing that bottle on a sandy and very bumpy beach will not magically distort your shadow to follow the contours. That is an artistic adjustment by the artist at the compositing stage. Make sure to also have a mask pass for just the bottle/object so you can add a shadow separately or distort the rendered shadow to match better.

Refraction might also be an issue. I don't remember if Corona can export a pass that retains 3D distortion data so the new background can be automatically distorted by the glass and/or liquid. If it can, I'd love to know how.

Also, a Shadow Catcher bug that I had reported long ago, was the intensity of the shadow setting didn't do anything at least on Mac C4D. Not sure if that bug is still there.

[bnji]

Hi there,
Indeed, having a more complex background image will complicate the entire process in order to get a more accurate result.
In cases like that, it will be easier to use the final background image in the 3D scene project.
Kind regards.