Contact Shadows seen through transparency / top down view

[Luismi]

I've been struggling with this issue for a while now—maybe it's a lighting mistake on my part or a lack of understanding. Whenever I view a transparent object from the top, especially when it's touching the ground, the center appears black and the inside looks very dark. If I lift the object off the floor, its color and transparency return to normal. Blurring the HDRI helps a bit, but then I lose the shadows and caustics.

I'm using a corona sun + corona sky with HDRI

Is there a material-based solution for this, or is it purely a lighting issue on my end?

corona version 11

cinema 4d 2023.2.0

[maru]

I would say this is expected when using directional lighting. What you see is the shadow of the glass, pretty much like here: https://www.gettyimages.ie/detail/photo/plastic-bottle-royalty-free-image/840778522
Perhaps disabling caustics would help here? (trading off realism for better artistic control)

[davetwo]

you could also cheat the IOR of the water to a lower amount to make is less dominant.
In any case the ''air'' should not be at the top of the bottle if the bottle is lying down. Removing that may make the difference between filled and empty less obvious too