I made a shader to create a gradient glass cup in cycle. However, I had some questions. I don’t know why the area the red arrow points out is different from other areas, which have clear reflection.
Is it my shader problem? or is it a problem of modeling?
It looks more like a modeling problem with that M shape.
There seems to be a problem with one of the two masks used.
I’m not doing the same thing, so I don’t know just by looking at the picture.
It looks like a smoothshading issue from the modeling. see if adding a couple control loops near the top of the cup helps.