Interesting idea. A glossy matcap could mask a hidden channel if the texture is crafted right, but you’d need to keep the rendering pipeline under tight control and avoid any side‑channel leaks. I’d approach it step by step, checking every frame buffer read and making sure no metadata betrays the steganography. It’s doable, but you’ll need a meticulous setup to keep it undetectable.

Sounds like a plan. Just remember to keep the specular spikes narrow and the bump map subtle—too much of a flash and you’ll get a glare, not a cloak. If you nail the balance, the surface will look just like any other shiny asset and the hidden channel will stay under the radar. Keep the layers tight, and you’ll keep the mystery intact.