Update visualisation documentation

Move deprecated Unreal Engine version from FRAME-Wiki

Author: Maarrk

docs/nodes/visualisation.md

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+# Visualisation
+
+Developed using [Godot Engine](https://godotengine.org/) and configured to display cockpit [instruments](./instruments.md) with [lidia](https://pypi.org/project/lidia) Python package.
+
+The environment features all obstacles suggested by ADS-33, but the vertical repositioning is modified to provide a reference similar to hover board at 15 and 40 feet above ground.
+
+[Screenshot showing the environment](./visualisation_environment.png)
+
+## Installation
+
+Download the release from [Releases page of this documentation](https://github.com/marsh-sim/marsh-sim.github.io/releases)
+
+Alternatively see [development section below](#development) for instructions how to run the project using Godot Editor.
+
+## Usage
+
+The application will attempt to start in VR, but if it fails it will display the default pilot viewpoint looking forward.
+In that mode, mouse movement can be used to rotate the camera, like in first-person video games.
+
+[Screenshot of pilot's point of view](./visualisation_pov.png)
+
+### Parameters
+
+These can be modified over MAVLink, for example using MARSH Manager.
+
+Example changes to `NAV_OFS_` parameters to start in given positions:
+
+- Sidestep, vertical repositioning: all default
+- Accelerate/decelerate: `HDG` = -90
+- Hover maneuver: `X` = 50, `Y` = 50
+- Start of slalom: `HDG` = -90, `X` = -100, `Y` = 300
+
+#### NAV_OFS_HDG
+
+Displayed heading relative to default position, in degrees.
+
+#### NAV_OFS_X
+
+Starting position offset, forward in default orientation, in meters.
+
+#### NAV_OFS_X
+
+Starting position offset, right in default orientation, in meters.
+
+#### LOCAL_FRAME_LAT
+
+Latitude of local coordinate frame origin when using messages with global position, in degrees.
+
+#### LOCAL_FRAME_LON
+
+Longitude of local coordinate frame origin when using messages with global position, in degrees.
+
+## Roadmap
+
+- Try to have some acceptable setup for Varjo even without the tracker
+- Rework the fly area
+  - Make it bigger
+  - Keep it square to avoid assymetric geometry
+  - Don't use the flat plane, just flatten the terrain
+  - Make the terrain mostly green, but add some small patches of different color
+- Fix z-figthing when looking at the runway from afar
+- Reduce pixel artifacts
+  - Adjust antialiasing
+  - Ensure there are mipmaps and they're used
+
+## Development
+
+The source code is hosted using internal Git service of Politecnico di Milano at [DAER/FRAME-Sim/MARSH/visualisation-marsh](https://gitlab.polimi.it/DAER/frame-sim/marsh/visualisation-marsh).
+There is a public mirror using [Forgejo](https://forgejo.org/) at `git(dot)lukasiewicz(dot)tech/DAER/visualisation-marsh` *not a link to avoid automated crawlers*.
+
+The asset files like textures and models are very big, so the project also uses [Git Large File Storage](https://git-lfs.com/).
+Once installed, it should work correctly with usual `git` commands but you may need to run this if you install it after cloning the repository:
+
+```sh
+git lfs pull
+```
+
+This repository uses [Git Submodules](https://git-scm.com/book/en/v2/Git-Tools-Submodules), to get all the code you need to run either:
+
+```sh
+git clone --recurse-submodules <address of this repository>
+# Or at any later point
+git submodule update --init --recursive
+```
+
+Using Godot v4.4.
+Install SCons with `pipx install scons`.
+You will need a C++ compiler, you might have one already on Linux, see below for Windows, otherwise in [Godot documentation](https://docs.godotengine.org/en/stable/contributing/development/compiling/index.html).
+
+For updating MAVLink generator, you additionally need `pip install future`.
+It is recommended to install any packages in a [virtual environment](https://docs.python.org/3/library/venv.html), for example:
+
+```sh
+python3 -m venv venv
+source venv/bin/activate
+pip install future
+```
+
+Some files are generated, run the following commands on first setup and when dependencies change:
+
+```sh
+godot --dump-extension-api  # after updating Godot
+python update_mavlink.py    # after updating MAVLink dialect
+python update_addons.py     # after changing any addon submodules
+scons compile_commands      # after modifying SConstruct
+cd project/addons/gdcef; python build.py
+```
+
+### Windows setup
+
+The most convenient way of getting a C++ compiler is via the LLVM-MinGW project (by the way, it optimizes the binary more).
+Download the `llvm-mingw-...-msvcrt-x86_64.zip` from the [Releases page](https://github.com/mstorsjo/llvm-mingw/releases).
+Unzip the archive to some location you like, and add its `bin` folder to `Path` using the "Edit environment variables for your account" program.
+
+### Build
+
+To build the GDExtension binary run SCons in the repository root, the default arguments have been added to the file.
+
+```sh
+scons
+```
+
+When building for Windows with MinGW-LLVM, you need to [select this compiler](https://docs.godotengine.org/en/stable/contributing/development/compiling/compiling_for_windows.html#selecting-a-compiler):
+
+```powershell
+scons platform=windows use_mingw=yes use_llvm=yes
+```
+
+## Deprecated UE5
+
+This visualisation is made in Unreal Engine 5. The scenery features all recommended ground references from the ADS-33E standard, and the visual helicopter model is the [Eurocopter MH-65 Dolphin](https://en.wikipedia.org/wiki/Eurocopter_MH-65_Dolphin). The instruments shown inside the cockpit are rendered by `lidia` package described above, so it must be running locally with the standard port to display them.
+
+Controls:
+- Use the mouse to look around
+- Move the viewpoint with `W` forward, `S` backward, `E` up, and `C` down
+- Cycle the fog intensity with `F`
+- Exit with `Alt+F4` :smiling_imp:
+
+To start the simulation in different locations of the scenery or different headings, edit the parameters using MARSH Manager window. You can also remotely change the fog intensity this way.
+
+If VR hardware is connected, the visualisation will start in the VR mode, otherwise it will run same as a regular fullscreen game.
+
+![Environment screenshot](./visualisation_ue5.png)
+
+Unfortunately, source code for Unreal Engine projects is quite incompatible with Git, so the Subversion repository was hosted privately.
+
+### Reasons for deprecation
+
+- Very lengthy installation process, and difficult with the network configuration at the laboratory
+- Little to no support for editing projects on Linux
+- Licensing of used assets forbids distribution in editable form.
+- Had unresolved performance problems when using VR headset with platform tracker
+- Had visual artifacts when using with Varjo headset, that we didn't manage to resolve. While Godot is less visually appealing at the start, it's a much simpler system.