I wantt to use the ray-casting to get the cursor position on a plane to make a ball roll to the position. But I found that ray-casting could not identity the correct position. So I added an ImmediateGeometry node to draw the rays in the world to check what happened. Here is what I found:
The origin of camera is infront of my view port and the rays are obviously not correct for usage because their origins are even infront of my cursor! I don't know why it happens, and here is my code:
if event is InputEventMouseButton and event.button_index == BUTTON_LEFT and event.is_pressed():
It's very strange, I also tried to move and create some other rays from another origin. In short, whereever I am I can always rotate my camera and see the origin of my camera. It is like you can rotate your eyes 180 degrees to see your brain. And because of this, what is shown in the viewport is not coincide the real camera position.