Decoupling Cameras from the Player's Ship

[Web-eWorks]

As promised in #192, this issue tracks the work needed to detach the view controller from the Player and allow centering / orbiting arbitrary objects or indeed any point in space at all.

We have several use-cases for this but they ultimately boil down to two:

• An "editor camera" used to fly around the solar system and inspect / verify that procedural generation, AI behavior, and custom definitions are working as intended. This in particular will be extremely important in implementing terrain generation.
• A "screenshot camera" used to take screenshots of the player's location and surroundings from arbitrary angles and positions, or to follow other ships or objects.

This naturally requires that the camera is able to "fly" on its own, with systems such as terrain generation and model rendering reacting appropriately to the presence of the camera and not the ship. As far as I am aware, most rendering-related systems use the camera's position by default, so I anticipate very little clean-up beyond decoupling such systems from vestigial dependencies on the player object.

As part of this work, we would like to improve handling of the existing cameras:

• [ ] Sidereal and External cameras need a "spring" behavior that prevents them from clipping inside world and ship geometry. This spring should offset the camera to push it out of geometry it would otherwise be clipping into, but should not limit the camera's zoom.
  • [ ] Sidereal Camera
  • [x] External Camera
• [x] The External camera needs exponential zoom scaling; the further the distance from the orbit point, the more zoom should be applied given the same input.

We would ideally like to add support for several additional camera controllers, being specializations of the general-purpose External camera:

• [ ] Add Orbit camera, which updates the view orientation as the ship orbits around a body to keep the same orientation relative to the normal of the orbital position.
• [ ] Add Chase camera, a fixed-yaw camera which applies an offset to the camera position based upon acceleration and changes in ship velocity.
• [ ] Add Look At camera, a fixed camera which updates its orientation to track a specific target.

This is not going to be a small undertaking, but the groundwork for it has been laid in #4536. This work will involve further decoupling ship and view controller, allowing PiGui to control the transition between a ShipViewController and a non-Ship ViewController, updating WorldView to properly handle the disconnect between a ship and a ViewController, and passing the responsibility for which object to orbit / center on to the ViewController instead of the individual CameraControllers.

[Gliese852]

How do you look at making a camera relative to the global coordinate system when you are in space, as in eve online, for example, but switching on relative to the surface of the planet when you enter a rotating frame? (get close to surface)

[impaktor]

Someone somewhere once requested missile camera. Maybe that's implied in one of the above listed points.