Additional translation of the camera. The camera movement applied here is always scaled by the calculated orthographic projection width and height.
By default this equals (0,0) which means that TCastleCamera.Position determines what is visible in the left-bottom corner of the viewport. This matches the typical 2D drawing coordinates used throughout our engine. In other words, if the camera is at position (0,0,whatever), then the (0,0) position in 2D is in the left-bottom corner of the TCastleViewport.
You can change it e.g. to (0.5,0.5) to move the camera to the middle of the viewport. In effect, if the camera is at position (0,0,whatever), then the (0,0) position is in the center of the TCastleViewport.
Both values of
Origin make sense, it depends on the game type and how you prefer to think in 2D coordinates. And how do you want the result to behave when aspect ratio changes:
With (0.5,0.5), things will stay "glued" to the center.
With (0,0), things will stay "glued" to the left-bottom corner.