Converting Quake II WAL Textures to PNG: id Tech 2 Mipmapped Raster Decoding

Released in December 1997, id Software's Quake II set new benchmarks for 3D game engines. Powered by the id Tech 2 engine, Quake II powered legendary titles including Heretic II, SiN, Kingpin: Life of Crime, Daikatana, and Anachronox.

At the core of the id Tech 2 rendering pipeline was the WAL texture format. Unlike standard image files of the era, a WAL file encapsulated four pre-generated mipmap levels along with surface animation and lighting metadata. Because modern game development engines (Unreal, Unity, Godot, Blender) cannot read .wal files directly, converting them into standard 32-bit RGBA PNG files is essential for modding, level design, and retro game preservation.

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1. The 100-Byte WAL Header Architecture

Every Quake II WAL texture begins with a strict 100-byte binary header:

| Offset | Size | Type | Description | |---|---|---|---| | 0x00 | 32 B | ASCII | Null-terminated texture path (e.g. e1u1/metal1) | | 0x20 | 4 B | uint32 LE | Texture width in pixels (power of two) | | 0x24 | 4 B | uint32 LE | Texture height in pixels (power of two) | | 0x28 | 16 B | uint32[4] | Offsets to mipmap levels 0, 1, 2, and 3 | | 0x38 | 32 B | ASCII | Next texture name in animation sequence (animname) | | 0x58 | 4 B | uint32 LE | Surface flags (e.g. sky, warp, flowing water) | | 0x5C | 4 B | uint32 LE | Content flags (e.g. solid, window, lava, slime) | | 0x60 | 4 B | uint32 LE | Surface light emission value |

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2. Four-Level Pre-Baked Mipmaps

To avoid mipmap generation latency during runtime level loading, id Tech 2 stored pre-downsampled textures directly in the file:

• Mipmap 0: Full resolution base texture ($W \times H$).
• Mipmap 1: Half resolution ($W/2 \times H/2$).
• Mipmap 2: Quarter resolution ($W/4 \times H/4$).
• Mipmap 3: Eighth resolution ($W/8 \times H/8$).

convrtr allows you to choose which mipmap level to export or defaults to the highest-fidelity Level 0 base texture.

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3. The Quake II 256-Color Palette

WAL textures store raw 8-bit color index bytes that reference the global Quake II colormap.pcx palette. convrtr bundles the canonical 256-color Quake II colormap, mapping each index byte into full 32-bit RGBA pixels before encoding into standard transparent PNG format.

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4. 100% Client-Side In-Browser Conversion

All binary header parsing, mipmap extraction, palette lookup, and PNG encoding execute strictly in your browser using pure TypeScript. No game assets or texture files ever leave your machine.