CameraUtilsGetPerspectiveScreenSize Method

public static Vector2 GetPerspectiveScreenSize(
	Vector2 worldSize,
	float lookDirectionDistance,
	float fieldOfView,
	Vector2 viewSize
)

Parameters

worldSize  Vector2

size in 3D space as Vector2

lookDirectionDistance  Single

distance from camera in the camera's look direction (see remarks for more info)

fieldOfView  Single

camera's field of view

viewSize  Vector2

SceneView's size as Vector2

Return Value

GetPerspectiveScreenSize calculates a size on screen (in same units as viewSize - without DPI scale) of a size in 3D space (worldSize) that is at lookDirectionDistance and shown with perspective camera with fieldOfView and in SceneView with viewSize.

To get the most accurate results the lookDirectionDistance must not be the direct distance from the camera but the distance in the camera's look direction. The lookDirectionDistance can be calculated with the following code:

var targetPosition = new Vector3(x,y,z);
var cameraPosition = Camera1.GetCameraPosition();

var distanceVector = targetPosition - cameraPosition;

var lookDirection = Vector3.Normalize(Camera1.GetLookDirection());

// To get look direction distance we project the distanceVector to the look direction vector
var lookDirectionDistance = Vector3.Dot(distanceVector, lookDirection);

var screenSize = GetPerspectiveScreenSize(worldSize, lookDirectionDistance, Camera1.FieldOfView, viewSize)

Reference