Transition from a Rigid Angular edges to smooth Surface

I’m trying to figure out the logic behind modeling something similar to the image attached, from a very angular rigid edges transitioning into a smooth cloth like surface. I’m not asking for a direct definition, just maybe an explanation of logic at where to begin ? any ideas or methods welcomed!

WhatsApp Image 2020-01-31 at 5.34.21 PM WhatsApp Image 2020-01-31 at 5.33.31 PM