I have been trying to figure out how this works for about a month now..
I tried asking everyone everywhere..also stackoverflow..now you guys are my last resort..can someone please help me decipher how is the following thing done?
https://bombayshirts.com/custom/...#

That's probably a 3D model rendered with WebGL.

They use multiple models, one for the cuffs, one for the advanced stuff, other for the collar and then a main one for the rest of the shirt.

Then the texture is generated using the selected fabric as a base, adding the plackets and the monogram in the cuffs.

If you want to get started with 3d graphics for websites, I suggest you take a look at three.js