Please do not forget to add a link to a playground to get a faster answer:
How to cast the ray from camera in ar by taking screenx and screeny ,
when i move an object or scale it is not sitting on the floor, want to check.
Here is the link
Could you create a repro in the playground instead ?
screen x and y are the pointer position, you should use the camera location as your source position.
Please read the instructions on the post, a playground is greatly recommended 