WAL

This page documents information about an engine not developed by Valve. This information is documented here because it has technical and/or historical relevance to Valve's engines.

WAL is a texture file format used by Quake II to store brush textures. It is a modified version of Quake I's miptex format, containing four mipmaps, two strings (used for animation), as well as three metadata values. The first two metadata values are bitfields, 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 contents flags used by Quake II would serve the basis for those used by Source.

Technical

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The header of a WAL file can be represented by the following C struct (from qcommon/qfiles.h in the Quake II source code release):

#define	MIPLEVELS	4
typedef struct miptex_s
{
	char		name[32];			// 31 chars plus null terminator
	unsigned	width, height;
	unsigned	offsets[MIPLEVELS];		// four mip maps stored
	char		animname[32];			// next frame in animation chain
	int			flags;
	int			contents;
	int			value;
} miptex_t;

Note:Both unsigned and int are 32-bits.

It is then followed by raw 8-bit image data for each mipmap, at the offsets relative to the start of the file.

Texture flags

GoldSrc

Quake II

Source Engine

edit

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 or similar result in Source 1.

Surface flags

Surface flags on different faces of a brush generally do not need to match. If two or more conflicting flags are assigned, then the flag with the lowest bit value will take priority.

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.
0x00000004	SURF_SKY	%Compile2DSky 1	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	$alpha "0.33"	Render the face as translucent, at 33% or 66% opacity, respectively. Most source ports, including the remaster, will render any texels using palette index 255 (or true color images with an alpha of less than 127) as fully transparent. While these flags can technically be combined, the behavior for such is not standardized. Some engines (such as Yamagi) will prioritize one or the other, others (such as Q2EX) will render the face at 50% opacity, and a small few will instead render the face with binary transparency.
0x00000020	SURF_TRANS66	$alpha "0.66"
0x00000040	SURF_FLOWING	TextureScroll material proxy	Texture scrolls from top to bottom. Note that this is different from scroll textures in GoldSrc, which scroll from left to right (and require a func_conveyor, which this does not).
0x00000080	SURF_NODRAW	%CompileNoDraw 1	Do not render this face in-game.
0x00000100	SURF_HINT	%CompileHint 1	Used on hint brushes.
0x00000200	SURF_SKIP	%CompileSkip 1	Completely ignore. Causes unexpected results when applied to anything other than hint brushes; use SURF_NODRAW for other brushes.
0x02000000	SURF_ALPHATEST	$alphatest 1	(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	$basetexturetransform "center .5 .5 scale 0.5 0.5 rotate 0 translate 0 0"	(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. If two or more conflicting flags are assigned, then the flag with the lowest bit value will take priority.

Bit	Flag name	VMT equivalent	Description
0x00000000	N/A	N/A	No contents, sometimes known as "CONTENTS_EMPTY". This cannot be assigned to a texture or surface via normal means, as brush faces with the contents field set to zero in the WAL and MAP file will be treated as solid.
0x00000001	CONTENTS_SOLID	N/A	Default contents. Generally no need to set manually.
0x00000002	CONTENTS_WINDOW	N/A	Prevents the renderer from drawing the backfaces of a brush.
0x00000004	CONTENTS_AUX	N/A	No effect (unused). Some compilers, such as ericw-tools, treat it as an alias for a combination of CONTENTS_MIST and CONTENTS_WINDOW.
0x00000008	CONTENTS_LAVA	%CompileWater 1, along with a trigger_hurt brush	Makes brush swimmable. CONTENTS_LAVA and CONTENTS_SLIME also deal periodic damage to the anyone or anything in them, with lava dealing more damage than slime.
0x00000010	CONTENTS_SLIME	%CompileSlime 1, along with a trigger_hurt brush
0x00000020	CONTENTS_WATER	%CompileWater 1
0x00000040	CONTENTS_MIST	%CompileNonSolid 1 $nocull 1	Disables collision, and sometimes disables backface culling.
0x00004000	CONTENTS_PROJECTILECLIP	N/A	(not in Vanilla) Blocks moving entities using CONTENTS_PROJECTILE. No effect on hitscan weapons.
0x00008000	CONTENTS_AREAPORTAL	N/A	Used on areaportals.
0x00010000	CONTENTS_PLAYERCLIP	%PlayerClip 1	Blocks player and bot movement.
0x00020000	CONTENTS_MONSTERCLIP	%CompileNPCClip 1	Blocks monster (NPC) movement.
0x00040000	CONTENTS_CURRENT_0	N/A	Pushes stuff inside it in the specified direction. These flags can be stacked to go in diagonal directions. Effectively acts like trigger_push. ZHLT and derivatives have tool textures that serve a similar purpose.
0x00080000	CONTENTS_CURRENT_90	N/A
0x00100000	CONTENTS_CURRENT_180	N/A
0x00200000	CONTENTS_CURRENT_270	N/A
0x00400000	CONTENTS_CURRENT_UP	N/A
0x00800000	CONTENTS_CURRENT_DOWN	N/A
0x1000000	CONTENTS_ORIGIN	%CompileOrigin 1	Sets the origin of brush entities.
0x2000000	CONTENTS_MONSTER	N/A	Internal flag, do not set.
0x4000000	CONTENTS_DEADMONSTER	N/A	Internal flag, do not set.
0x8000000	CONTENTS_DETAIL	%CompileDetail 1	Brush does not chop structural brushes, and does not affect VIS. It may, however, still affect visibility.
0x10000000	CONTENTS_TRANSLUCENT	N/A	Marks brush as able to be seen through. Automatically set by SURF_TRANS33 and SURF_TRANS66, and in some compilers, SURF_ALPHATEST.
0x20000000	CONTENTS_LADDER	%CompileLadder 1	Makes climbable.
0x40000000	CONTENTS_PLAYER	N/A	(not in Vanilla) Internal flag, do not set.
0x10000000	CONTENTS_PROJECTILE	N/A	(not in Vanilla) Internal flag, do not set.

Variants

• Daikatana WALs are mostly identical to Quake 2 WALs, but have 8 mipmaps instead of 4. This makes them more suitable for hardware renderers than Quake 2's format.
• SWL files are used by SiN.^[Elaborate?]
• M8 is a variation of Quake 2 WALs that stores its own palette. Like WAD3, this adds 768 bytes to the file size.
• M32 is a variation of Quake 2 WALs that stores its mipmaps in an uncompressed 32-bit RGBA format, best suited for textures with translucency.
• WAL_JSON is a JSON file used by ericw-tools which can store the metadata found in a WAL, allowing compiling maps with textures that use other texture formats (TGA, PNG, or JPG) without also creating an associated WAL file. It also adds a color value to override the color of texlights.

External links

• Surface and content flags documentation from the "Rust" tutorials