All we see is a reflection of light.
Depth, detail, angle, is all a function of light being blocked by physical dimension.
Yet, in painting, it's so hard for me to trust shadows. Something about taking black onto my brush and applying it to the white surface screams of ruining the painting and starting again.
Of course, someone once told me, you shouldn't aspire to create any form of art unless you're willing to start over....and over....and over.
I took the painting where it's at now and imported it to Photoshop so I could play with the shadows and then decide where I want to go.