Trying to draw a circle with an angle in a material for a cylinder

Hello everyone! I am developing a game about cutting Tatamis (procedural mesh with a cylinder shape) with a Katana. Therefore, I need a way to indicate the player where and with which angle should cut. For this Im trying to do it through material functions, so I can change the position and angle of the cut whenever I want.

I’m really new to the materials things, but I tried the following:

Which looks like this:

The problem that I am having is that when the texture starts tilling, the indicator is too sharp, and I am trying to achieve something more round.

I have also tried decals (this kinda of works) but It doest stick with the sliced part of the Tatami. Also affects the katana when is near.

Thanks in advance for any guidence about this!

Perhaps you could use a cube mask to change the material where it intersects a cube. This sort of idea:

Maybe I dont understand your answer, but I think It will have the same problem as the decal. After cutting the cylinder right in the middle of the box, the upper half should follow the top piece of the cylinder (which will have physics) and the bottom half should stay with the base of the cylinder.

Maybe you could apply the mask then bake the material onto the mesh before it gets cut