Hi, sorry for the late answer. I am indeed using Python, but I must have not been clear enough in my question: I'm trying to get a stream to cast a ray in the direction the vessel is currently moving from the current lower bounding vector. I can set up a stream for the vessel.bounding_box attribute, and I can set up a stream to cast a ray in the right direction from a fixed point, but I can't find a way to access the first element of vessel.bounding_box with a server-side expression so I can use it as an argument to pass to the raycast_distance function inside a stream. If I use vessel.bounding_box[0] in the stream definition, it just uses the value of the lower bounding vector at initialization and doesn't change when the vessel moves. Is this possible and, if so, how would you go about doing it? Hoping this is somewhat comprehensible, thank you in advance.