How to make a figure with shadows?

Good evening!
The task is to mark up the item WH in the picture circled in red. This is the bootstrap, under the logo selected 3 columns, corresponding to the triangle should only be in these three columns, at the same time, the parent unit must be a shadow across the entire width. Picture overlay does not work, because the shadow images overlap css shadow parent unit, tried to make a triangle using SVG, but the same problem. Can someone implement this?
Thank you!
5a31580574b30538603286.jpeg
June 10th 19 at 15:29
2 answers
June 10th 19 at 15:31
I would do something like this:
https://codepen.io/elijah_tr/pen/MrYXpw
(Not ie and not edge)
June 10th 19 at 15:33
https://codepen.io/anon/pen/rpejQW
The meaning should be clear

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