D2OpenGL

An OpenGL renderer for Diablo II: Lord of Destruction on Windows (1.14d, 1.13d, 1.13c, 1.10f).

Blizzard shipped an OpenGL renderer for Diablo II only on the Mac. The Windows game still has an -opengl switch and a slot for that renderer, but nothing behind them. D2OpenGL is the Mac renderer's code, recovered from the Mac 1.14d binary and rebuilt as a Windows DLL, with a new Windows (WGL) layer where the Mac code used Apple's APIs.

It is a restoration, not Blizzard's source code. It is not affiliated with or endorsed by Blizzard Entertainment. You need your own copy of the game.

Put D2OpenGL.dll from the releases in the game folder.

1.14d, 1.13d, 1.13c: start the game through the DLL:

C:\Windows\SysWOW64\rundll32.exe "C:\path\to\Diablo II\D2OpenGL.dll",Play

Add -w after Play for a window; other Diablo II options are passed on as well. On 32-bit Windows use C:\Windows\System32\rundll32.exe. Play starts Game.exe -opengl with the DLL loaded.

1.10f: the original Game.exe does not run on current Windows. With D2Loader, put D2OpenGL.dll in its plugin folder instead and start D2Loader with -opengl. Windows 10 and 11 show a compatibility warning for the 1.10 files; the game runs regardless.

No game file is modified on disk; the DLL re-enables the game's OpenGL path in memory, and only with -opengl. A log is written to D2OpenGL.log in the game folder. Other game versions are left alone.

Settings are read from D2OpenGL.ini next to D2OpenGL.dll; without the file the defaults apply.

[Display]
Scaling    = auto        ; auto, off, or a whole number
Fullscreen = exclusive   ; exclusive or borderless
Filter     = sharp       ; sharp, nearest or linear
Shader     = none        ; none or crt
RenderScale = 2          ; 1 to 4
Upscale    = mmpx        ; mmpx or none

[CRT]
Scanlines  = 0.30        ; 0 to 1
Mask       = 0.15
Glow       = 0.08

• Scaling: the game still runs at 640x480 or 800x600; the picture is scaled up to the window. auto windowed picks the largest whole multiple that fits the screen. off draws exactly as the Mac renderer does, with no scaling and a display mode switch in fullscreen.
• Fullscreen: exclusive switches the display to the game's resolution; borderless covers the monitor at the desktop resolution and fits the picture to it, keeping the aspect ratio (still has problems).
• Filter: sharp keeps pixels square and crisp at any size, nearest repeats pixels, linear blurs.
• Shader: crt imitates a late-1990s PC monitor (aperture grille, fine scanlines, a little glow).
• RenderScale: the picture is drawn at this multiple of the game's resolution before it is scaled to the window. 1 draws at the game's resolution. Ignored with Scaling = off.
• Upscale: with a render scale above 1, mmpx enlarges sprites (characters, monsters, items, the interface) with the MMPX pixel-art filter before they are coloured, so they keep the game's 256 colours and colour variants; none draws them with plain square pixels. Floors and walls are not enlarged. At RenderScale = 3 sprites are enlarged 2x and drawn at 3x.

• Diablo II 1.14d, 1.13d, 1.13c and 1.10f.
• So far tested on Windows 11 in a virtual machine (Parallels). 1.14d windowed and fullscreen; 1.13d and 1.13c in game, windowed; 1.10f to the main menu, windowed and fullscreen. Scaling and the CRT shader so far only on 1.14d.

With the mingw-w64 i686 toolchain (i686-w64-mingw32-gcc/g++) and Zig 0.16 (for the libd2 submodule):

git submodule update --init
make

The DLL is written to build/D2OpenGL.dll.

MIT for the code written for this project; the recovered renderer code is not licensed by it. See LICENSE.