@ : Thanks for the help.
Although I think it is not gonna be solved with a simple shader. I need to find out the exact position of the point on the camera space. already Z will be given in cm away from the camera, but X and Y are in pixels and this is where coordination mapping solve the problem by using color data and turning X and Y to the cm ( camera space ) too.
By the way, even if you are going to use the shader then how are you going to access its data ( compiled and rendered one ) from C++ or blueprint ( ok blueprint is a bit too ambitious but c++ ) if you know a generic way please share it with me.