I have a GLTF model that contains a number of meshes, the position of all meshes is zero, and I need to find the position of each mesh relative to the center of the screen.
Relative you mean in 2D or 3D?
No, I mean 3D
Are you casting a ray from the center of the screen/camera to determine a point in 3D space that is the “center of the screen”? Assuming you have this point as a world position
For each local mesh position, get its world position
Subtract this world position and get the length of the vector
That’s the relative length/distance from the “center of the screen”