Darkness in transparent surface ?

[zeealpal]

Not sure if you've tried already, but does the caustic cache yield any decent results? If the camera is the only thing moving, then it wouldn't need to be recalculated between frames.

[zooropa]

Yes the table is still and I am moving the camera for different frames. I need to explore that feature, I am new with lux.

[FarbigeWelt]

You image looks like like you are looking pretty diagonally, so a number around 100 doesn't seem unrealistic.

Very well explained, CodeHD. Your sketch and words help much to understand why rendered glass seems looking wrong or vice a versa we often do not perfectly know how glasses / transparent material look in reality.

I like to add what I learned about glasses in LuxCoreRender over the past months.
->) If you need material Glass colored clearly you must define an internal Volume Clear and define its Absorption Color and Depth (the depth at which the volume gets its defined absorption color).
->) Usually, I define colors with saturation ~0.9 and value 1.0. Then I define depth depending on object’s depth (metric size).
For slightly colored objects I define absorption depth e.g. 25 times of object‘s depth,
for dark colored e.g. 1/10 or less.

Have all much fun with splendid LuxCoreRender!