沿对角线测量的 Scene 视图大小。
Use with pivot, rotation, and CameraSettings.fieldOfView to calculate camera transformation.
The image above shows the math used to calculate the actual field of view. Here BC = size, and you need to find AB. ACB is a right angle, and BAC is half the field of view. That creates the expression: sin(BAC) = BC/AB, and so AB = BC/sin(BAC).