WAL
WAL is a texture file format used by 
Quake II to store brush textures. A single WAL file contains one miptex, as well as three metadata values. The first two metadata values are bitflags, indicating information about a brush's face (surface flags) and a brush's contents (content flags). The third metadata value is an integer value, traditionally used for determining the brightness of texlights (although some compilers use it for other purposes on non-emissive surfaces, such as for smoothing groups in Arghrad).
The surface flags and content flags found in WAL files would serve the basis for the material map compile flags used by 
Source 1.
Texture flags
These sections list and describe the various standard surface and content flags used in Quake II, as well as the equivalent VMT parameters to achieve the same result in Source 1.
Surface flags
Surface flags on different faces of a brush generally do not need to match.
| Bit | Flag name | VMT equivalent | Description |
|---|---|---|---|
| 0x00000001 | SURF_LIGHT | N/A | Treats this face as a texlight, with brightness dependent upon the surface value. |
| 0x00000002 | SURF_SLICK | N/A | Makes this face slippery to walk on. |
| 0x00000004 | SURF_SKY | Face is is not drawn, and the skybox is drawn behind all visible faces when this face is in the PVS. | |
| 0x00000008 | SURF_WARP | Potentially simulatable using material proxies | "Warp" the texture on this face, like water. |
| 0x00000010 | SURF_TRANS33 | Render the face as translucent, at 33% opacity.
Most source ports, including the remaster, will render any texels using palette index 255 (or true color images with a alpha of less than 127) as fully transparent. | |
| 0x00000020 | SURF_TRANS66 | Render the face as translucent, at 66% opacity.
Most source ports, including the remaster, will render any texels using palette index 255 (or for 32-bit textures, texels with an alpha of less than 127) as fully transparent. | |
| 0x00000040 | SURF_FLOWING | TextureScroll material proxy | Texture scrolls from top to bottom. Requires SURF_WARP. |
| 0x00000080 | SURF_NODRAW | Do not render this face in-game. | |
| 0x00000100 | SURF_HINT | Used on hint brushes. | |
| 0x00000200 | SURF_SKIP | Completely ignore. Causes unexpected results when applied to anything other than hint brushes. | |
| 0x02000000 | SURF_ALPHATEST | (not in Vanilla) Use binary transparency, using either palette index 255 of an 8-bit texture or the alpha channel of 32-bit texture as a transparency mask. | |
| 0x10000000 | SURF_N64_UV | (not in Vanilla) Halves texture sizes, without requiring setting texture scale in the editor to 2.0. | |
| 0x20000000 | SURF_N64_SCROLL_X | TextureScroll material proxy | (not in Vanilla) Scrolls the texture on the X axis. Slower than SURF_FLOWING. |
| 0x40000000 | SURF_N64_SCROLL_Y | TextureScroll material proxy | (not in Vanilla) Scrolls the texture on the Y axis. Slower than SURF_FLOWING. |
| 0x80000000 | SURF_N64_SCROLL_FLIP | TextureScroll material proxy | (not in Vanilla) Inverts the scroll direction. |
Content flags
Content flags on different faces of a brush almost always need to match. Mismatched contents will result in compiler errors, and leaves it up to the compiler to decide what contents a brush should have. The exception to this rule is the "current" flags.