Octane Displacement with Alpha
If you have problems/errors with your opacity channel in combination with displacement in c4d octane, it could be that you are using the exact same texture which results in some kind of fade out effect. You have to modfiy the opacity image in a way that your black and white colors are a little bit offset from your displacement, so they don´t interfere. Just make the black a little smaller oder bigger and you will see the effect.
Displacement are grey values and opacity is green (for a better representation)