Function gvr_sys::gvr_buffer_viewport_set_opacity

pub unsafe extern "C" fn gvr_buffer_viewport_set_opacity(
    viewport: *mut gvr_buffer_viewport, 
    opacity: f32
)

Sets the opacity to perform on the specified viewport.

@param viewport The buffer viewport. @param opacity Opacity that will be applied per viewport. It should be within [0,1], default to be 1.