What's new in 1.9
Ultra textures
Default Ultra Textures: the menus, the level select and its pictures of each level, the text and the HUD (including the ECTS HUD mod's icons), upscaled 4x from the game's own textures, for more readable, less blurry text. Turn on Ultra textures in Graphics settings or Display Options.
The GameCube high-resolution Ultra texture pack (GLOS69) replaces every texture. It is its author's work and is downloaded separately: put its GLOS69 folder next to twotowers_recomp.exe. The first time you press Play with the option on, the launcher prepares the pack (once; a few minutes, with a progress bar; about 1 GB). If you turn the option on in the game's own menus, the launcher opens and prepares it while you play, and the new pictures appear when it finishes. On Linux and macOS, TwoTowers.sh / TwoTowers.command do this (or run ./twotowers-setup ultra).
Graphics
Internal resolution up to 12x (7680 × 5760 at 4:3). A picture larger than the window is now averaged down to it properly. Before, high settings sharpened textures but left edges as jagged as at 1x; now they smooth edges too. At very wide aspect ratios the picture is held to the largest one a graphics card can draw (16384 wide).
MSAA anti-aliasing: MSAA 2x, 4x and 8x, and MSAA 4x / 8x with FXAA, in Display Options, the launcher and the ini (antialiasing=msaa4, ...). It works on Direct3D 11, Vulkan and OpenGL (Linux, macOS). At very high internal resolutions it uses fewer samples rather than run out of video memory.
Gameplay and effects
Up to 512 particle effects at once (the game had 64). Beams, the Uruk-hai's fire rock and the archers' fire pots now all show together. Before, your own effects put out the archers' fire, though it still caused player damage.
From 1.8.2 (test builds)
In widescreen, the in-engine cutscenes stay 4:3 unless Widescreen cutscenes is on (Display Options, launcher). Their skies and mountain cards were made for 4:3.
Menu buttons no longer press themselves (the title screen, hovering over Credits). Right click backs out of Options opened from the mission select. Right click on the character select unselects the hero.
The Uruk-hai's fire rock burns. The upgrade screen's level leaves follow the pointer. Mouse steering turns the hero where he stands, and the move keys go by his facing. Frodo's stones hurt the Watcher.
Tested
Windows, Linux and macOS builds compile.
Ultra textures on the real GLOS69 pack: the prepared set matches the hand-made one checked earlier (the same 2869 pictures, the same pairings). The launcher's --build-ultra, Linux's twotowers-setup ultra, and the game picking the pack up while running were also tested.
Under Wine (Direct3D 11) and on Linux (OpenGL): MSAA 4x / 8x in Orthanc and its scenes (edges smoothed, effects as before); 4x and 12x internal resolution (12x at 32:9 with 8x MSAA held to 16384 wide); 512 particle effects at once, and a level replayed.
Not tested: real graphics cards at 9x–12x or 8x MSAA (video memory and speed); MSAA through Vulkan (DXVK); the macOS build on a Mac.