DirectGlide

A from-scratch Glide 2.x → Direct3D 11 wrapper, written to run King's Quest 8: Mask of Eternity in Glide mode on modern Windows.

DirectGlide ships as a drop-in glide2x.dll — you replace the game's existing Glide library (nGlide, dgVoodoo, etc.) with this one and the game boots into a native D3D11 rendering path.

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⚠️ Important — this is NOT a complete fix for KQ8

DirectGlide only replaces the Glide rendering library. To actually run KQ8 on modern Windows you also need the kq8fix shim applied to the base game. kq8fix handles the game-engine-side compatibility problems (CPU speed detection, DirectDraw fallbacks, window creation, etc.) that DirectGlide doesn't touch.

Setup order:

1. Install KQ8 (GoG / original disc / etc.)
2. Apply kq8fix to the base game
3. Drop DirectGlide's glide2x.dll into the game folder (replacing any existing glide2x.dll)
4. Make sure Options.cs has assignGModeName Glide so the game picks the Glide renderer

Without kq8fix, the game will likely not launch or will crash before reaching the 3D pipeline — regardless of what Glide wrapper you use.

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Why this exists

KQ8's bundled nGlide 1.04 crashes in Windows' Application Compatibility layer (AcGenral.DLL) when rendering on modern Windows. dgVoodoo had similar issues in testing. This wrapper was written specifically to bypass those compatibility shims by implementing Glide directly against D3D11 with no legacy code paths in between.

The bonus: because we're implementing Glide from scratch, we get to add niceties that nGlide/dgVoodoo/real Voodoo hardware couldn't provide.

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Features

Rendering

• 2× SSAA — scene renders at 1280×960 internally, box-filter downsampled to 640×480 before final upscale. Fixes tri-diagonal seams the original hardware had.
• 8× anisotropic filtering with Lanczos-2 CPU-generated mipmaps — sharp detail at oblique angles without shimmer.
• Sharp-bilinear upscale from 640×480 to native resolution — retains pixel-perfect retro feel while filling modern displays.
• Clamped-exponential fog — pre-populated exp fog table for KQ8's grFogMode(GR_FOG_WITH_TABLE) calls with grFogTable never invoked by the game (relied on hardware defaults on Voodoo).
• Full combiner support — color / alpha / texture combiners with factor variants implemented in a single uber-shader.
• W-buffer depth for correct sorting in the game's native mode.

Integration

• Fullscreen with aspect-preserved letterbox — 640×480 render target, upscaled to fit your monitor with black bars where needed.
• Mouse coordinate translation via both WndProc subclassing and IAT patching of GetCursorPos/SetCursorPos/ClipCursor in the game EXE.
• HUD persistence hack — KQ8 draws some static overlays (XP bar, decorative icons) only on first appearance; DirectGlide detects HUD bar extents from the leftmost pixel column and preserves those rows across frames, while dynamic elements (cursor, dialogue) still wipe cleanly.
• Fullscreen intro/outro FMV — WndProc subclass on the MCIWnd child window plus IAT-patches on msvfw32's imports of StretchDIBits/SetDIBitsToDevice/StretchBlt intercept the video playback thread's draws and redirect them to an aspect-preserved letterboxed fullscreen rect. MCIWnd's own PUT_DEST/SETZOOM messages are ignored on modern Windows, so we hook the underlying gdi calls instead.
• Save-file thumbnails — grLfbLock(READ_ONLY) populates the returned buffer with a GPU-readback of the current gameTex so KQ8 can capture a real thumbnail of the current 3D scene when saving. grLfbWriteRegion blits saved thumbnails back for the save/load screen. Pre-fix, both paths silently returned the wrapper's canary buffer → every thumbnail slot was colorful static.
• NVIDIA GPU selection — enumerates DXGI adapters and picks the discrete GPU over integrated when available.

Performance

• Chained-hash texture cache with LRU eviction — no memory thrash even in texture-heavy scenes.
• State object caching — cached blend/depth/raster states avoid redundant D3D11 state object creation.
• Palette hash caching for deferred palettized texture decoding (OpenGlide-style).

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Building

Requires Visual Studio 2022 (or newer) with the x86 C++ toolchain and Windows 10 SDK.

build.bat

Output: build\glide2x.dll.

To enable debug logging (writes DirectGlide.log next to the game's EXE), edit src/log.c and change DG_LOG_ENABLED to 1, then rebuild.

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Installing

1. Locate your KQ8 install folder (typically C:\Games\KQ8 or C:\Program Files (x86)\GOG Galaxy\Games\Kings Quest 8\).

2. Back up the existing glide2x.dll.

3. Copy build\glide2x.dll into the game folder.

4. Launch KQ8. If it crashes in AcGenral.DLL, launch via a .bat that sets __COMPAT_LAYER=! to bypass compat shims:

   @echo off
   set __COMPAT_LAYER=!
   start Mask.exe

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Known Limitations

• KQ8 specific. DirectGlide implements the subset of Glide 2.x that KQ8 actually uses (106 functions; 150 exports for binary compat). Other Glide games may work but aren't tested or targeted — features KQ8 doesn't call (multi-TMU, LFB read-back, etc.) are stubs.
• Fog defaults tuned for KQ8. KQ8 never calls grFogTable, so we pre-populate a fog table tuned for its specific W range (near=16000, far=20000). Other games that do call grFogTable will use their own tables correctly, but if they also don't call it the defaults may look wrong.
• HUD-detection hack relies on a KQ8 convention. We probe the leftmost pixel column to detect HUD bar extents. If another game renders non-HUD content that extends to x=0, the persistence logic could misclassify it.
• No AA draw variants / line drawing. grDrawLine, grDrawPoint and grAA* are routed through the triangle path.
• Intro/outro FMV codec. KQ8's intro and ending movies are Indeo 5 encoded AVIs (W32opn_1.dll, W32ndg_1.dll, W32mdl_1.dll) — Windows 10/11 has dropped the Indeo codec. Users can re-encode to Cinepak with ffmpeg:

  ffmpeg -i W32opn_1.bak.dll -c:v cinepak -q:v 5 -c:a pcm_s16le -f avi W32opn_1.dll
  

  The "Replay Intro" menu option also requires two clicks on modern Windows (first click puts the game into a fullscreen / mode-switch state, second click plays the video) — that's a KQ8 engine quirk, not a DirectGlide issue. Once the video does play, DirectGlide handles the fullscreen stretch.
• Pitch-black shadow decals. KQ8 draws shadow polygons via blend (ZERO, SRC_COLOR) with a near-black source texture. Because our alpha-combiner pipeline emits low alpha for pixels that should be fully opaque, we currently map GR_BLEND_SRC_ALPHA to D3D11_BLEND_ONE as a workaround that keeps regular geometry looking right. The side-effect is that legitimate multiplicative shadow decals render as pure-black rectangles instead of subtle darkening. A proper fix requires auditing the alpha combiner to match the Glide 2.x spec — see mapBlend() in src/d3d11_backend.c.

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Credits

• OpenGlide (https://github.com/voyageur/openglide) — reference for the tableIndexToW[] lookup table and guFogGenerateExp/Linear formulas. DirectGlide's fog code structure mirrors OpenGlide's.
• 3dfx Interactive / Glide SDK 2.2 — API specification.
• Sierra On-Line — King's Quest VIII: Mask of Eternity (1998).

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Legal

King's Quest, Mask of Eternity, and related trademarks are the property of their respective owners. DirectGlide is an independent interoperability library and is not affiliated with, endorsed by, or sponsored by Sierra, Activision, or any other rights-holder. It implements the published Glide 2.x API specification and contains no code from any Glide SDK implementation.

DirectGlide is released into the public domain under the Unlicense — see LICENSE. Use it however you want, no warranty provided.