enum ViewportMapping {
SoCamera::CROP_VIEWPORT_FILL_FRAME Crops the viewport within the current window, so that the aspect ratio matches that of the camera. As the window size changes, the aspect ratio remains unchanged. The cropped region
is drawn as a filled gray area.
SoCamera::CROP_VIEWPORT_LINE_FRAME Crops the viewport, but draws a thin frame around the viewport
SoCamera::CROP_VIEWPORT_NO_FRAME Crops the viewport, but gives no visual feedback as to the viewport dimensions within the window
SoCamera::ADJUST_CAMERA Adjusts the camera aspect ratio and height to make it fit within the given window. (The camera's fields are not affected, just the values sent to the graphics library.)
SoCamera::LEAVE_ALONE Do nothing. Camera image may become stretched out of proportion
}