I stumbled over this old set of Regina shot through a fringe curtain one sunny day in a previous studio. It’s simply sunlæight streaming through a window, striking a voluptuous model and creating this wood-grain or topographical map effect.
One of the interesting things about hard light is that you can play games with exposure, like here, rendering the entire image low-key.
That is, if you use a modern digital camera with enough range to capture the deep shadows and retain some detail there that can be exploited when developing.
You can see more details about the setup in the BTS movies.
1/640 sec ƒ7.1