dat how u do dat? we need to find theta how we do that? and how do we inverse it to find the other angle to do reflect. in simple words

I need a way to find the angle at which the camera is looking at the mirror and inverse the CFrame of the viewport (mirror) camera to make it look at the object like real mirrors do so.
Cam to Mirror angle = 45 degree
Mirro to Object angle = -45 degree

Get it??? no? please dont say no thats the best I can explain!

hmm nope as thats for non-euclidiean things aka portal 2 like games I want mirrors the basic idea is I need a way to find the angle between 2 rays
aka the ray â€śYOUâ€ť and â€śPERPENDICULAR RAY TO EXPLAINâ€ť in the imagine in my original post.

In regular reflection, the angle of incidence (where the wave first approaches the glass) is equal in magnitude to the angle of reflection (where the wave first leaves the glass).

When you make a ray (or at least using the old Ray method instead of the new one) it returned a angle, and you can just make a ray from the camera to whatever is in front of it

Is the angle at which the wave first approaches the plane.

Youâ€™ve already stated that this is 45 degrees.

Practically, I would calculate the distance the player is from the plane and construct a triangle.

You can then use the sine law to calculate the angle of incidence, given the perpendicular angle of the triangle with the two sides distancing the player from the plane.

They should just make a mirror tool in studio that just works as a normal mirror i tried many ways to make one and it either was really low quality or lag was to much i also tried to do pixel by pixel but that also was ridiculous

Hey, I just want to point out the fact @anon_j1124 is giving you help for free wasting his time in the progress. Try to be less rude because he has no reason to help you.