I have a pbr shader that samples from a cube map if the metalness is > 0.
Now, in my engine, the user may choose to use a regular 2D background (for 2D side scrollers and such).
If the user does so, I would like to send this 2D background as sampler2D to the shader and somehow fake at least some sort of poor reflections in order for the metalness to actually make the object look metal-ish.
Do you guys know how I could achieve that?
Thanks for any hints!!