How to convert measure in pixel to 3D space units ?

[wideeyenow_unity]

Found this post, not sure if it will help or not:

How can I know if a gameObject is 'seen' by a particular camera?

There's a whole slew of ways to achieve this, depending on the precise functionality you need. You can get events when an object is visible within a certain camera, and when it enters or leaves, using these functions: OnWillRenderObject, Renderer.isVisible, Renderer.OnBecameVisible, and OnBecameInvisible Or you can calculate whether an object's bounding box falls within the camera's view frustum, using these two functions: GeometryUtility.CalculateFrustumPlanes GeometryUtility.TestPlanesA…

But correct me if I’m wrong, you say you can measure how far the object is out of view? If so, just reference that offset, and move the camera until that offset is 0.