BSP flags (Source)

public/bspflags.h defines bitfields used to tell the game engine and compiler how a brush face should be drawn in-game (surface flags), and what should be inside the brush (contents flags). They are descended from the method used by Quake II.

These are normally defined via Material map compile flags, but they can also be applied directly into a VMF's brush face, using "contents" "####" for contents flags and "flags" "####" for surface flags (wherein #### is the bitfield represented in base 10 form). Some values are also defined via other means, such as func_detail for CONTENTS_DETAIL.

Important:

Hammer 4.x strips these values! Put applicable geometry in an instance to avoid issues.

Confirm:

Hammer++ might keep the values.

Some of the contents flags are also used for MDL models, and are set using the $contents QC command.

List of flags

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.

Unlike Quake II, surface flags are stored as a 16-bit value instead of a 32-bit value. This is because most information about how to draw the surface can be determined instead at runtime via the VMT.

Bit	Flag name	Dev comment	Description
0x0001	SURF_LIGHT	value will hold the light strength	Normally set on any surface that matches a RAD file entry; not actually written to the BSP, unlike Quake II. Confirm:Can the value field be set in a VMF, or does it require regressing to MAP instead?
0x0002 (removed since )	SURF_SLICK	effects game physics^[sic]	Deprecated:Legacy Quake II flag; deprecated in favor of surface properties.
0x0002 (in all games since )	SURF_SKY2D	don't draw, indicates we should skylight + draw 2d sky but not draw the 3D skybox	Shows only the 2D skybox. Set via $Compile2DSky Confirm:`%Compile2DSky` assigns both SURF_SKY2D and SURF_SKY; what happens if a face only has SURF_SKY2D?
0x0004	SURF_SKY	don't draw, but add to skybox	Shows both the 2D and 3D skybox. Set via $CompileSky
0x0008	SURF_WARP	turbulent water warp	Tells VVIS and the engine renderer that the surface is water. Set via `%CompileWater`, but not `%CompileSlime`. Confirm:Why does VVIS read this?
0x0010	SURF_TRANS	(None)	Surface is translucent, either via `$translucent` or `$alpha`. Confirm:Might also apply to `$alphatest`.
0x0020 (removed since )	SURF_WET	the surface is wet	Deprecated:Legacy Quake II flag; deprecated in favor of surface properties.
0x0020 (in all games since )	SURF_NOPORTAL	the surface can not have a portal placed on it	Set via %NoPortal
0x0040 (removed since )	SURF_FLOWING	scroll towards angle	Deprecated:Legacy Quake II flag; deprecated in favor of material proxies.
0x0040 (in all games since )	SURF_TRIGGER	FIXME: This is an xbox hack to work around elimination of trigger surfaces, which breaks occluders	Set via %CompileTrigger. Doesn't do anything in the PC versions.
0x0080	SURF_NODRAW	don't bother referencing the texture	Set via %CompileNoDraw
0x0100	SURF_HINT	make a primary bsp splitter	Set via %CompileHint
0x0200	SURF_SKIP	completely ignore, allowing non-closed brushes	Set via %CompileSkip. Should never be used on anything except a hint brush.
0x0400	SURF_NOLIGHT	Don't calculate light	Face is unlit. Set via %CompileNoLight if using or newer or . Set automatically on UnlitGeneric materials.
0x0800	SURF_BUMPLIGHT	calculate three lightmaps for the surface for bumpmapping	Implied by $bumpmap and/or $normalmap. Actually calculates four lightmap, with the fourth being used when bumpmapping is disabled.
0x1000	SURF_NOSHADOWS	Don't receive shadows	Using or VBSP, set via `%CompileNoShadows`. Confirm:How is it used in vanilla compilers? It seems to be unrelated to `info_no_dynamic_shadow`.
0x2000	SURF_NODECALS	Don't receive decals	Set via $nodecal. Can also set via %nopaint in Portal 2.
0x4000	SURF_NOCHOP	Don't subdivide patches on this surface	Set via %CompileNoChop. Has the side effect of affecting triangulation, as well.
0x8000	SURF_HITBOX	surface is part of a hitbox	^[Why?]

Code:0x0020 can reliably be used as a custom surface flag on mods not using portals.

Contents flags

Contents 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.

In addition to brushes, some of these flags can also be set on MDLs using $contents parameter.

Todo: Third-party titles

Bit	Flag name	Official description	Notes
0x00000000	CONTENTS_EMPTY	No contents	Technically not a flag, but rather the lack of any flags. This cannot be manually assigned to a surface, as brush faces with the contents field set to zero in the VMF (or MAP) file will be treated as solid^{[citation needed]}. Instead, use %CompileNonSolid, a func_illusionary, or a non-solid func_brush.
0x00000001	CONTENTS_SOLID	an eye is never valid in a solid	Default contents
0x00000002	CONTENTS_WINDOW	translucent, but not watery (glass)	Affects VIS testing.
0x00000004	CONTENTS_AUX	(none)	Unused.
0x00000008	CONTENTS_GRATE	alpha-tested "grate" textures. Bullets/sight pass through, but solids don't	Equivalent to a combination of two brushes: one %CompileNonSolid, and the other %CompileClip. Set via `%CompilePassBullets` or `$contents "grate"`.
0x00000010	CONTENTS_SLIME	(none)	Set via %CompileSlime. Unlike Quake II, slime does not do damage; a separate trigger_hurt should be used for this.
0x00000020	CONTENTS_WATER	(none)	Set via %CompileWater.
0x00000040 (removed since )	CONTENTS_MIST	(none)	Unknown purpose; only set by %CompilePlayerControlClip.
0x00000040 (in all games since )	CONTENTS_BLOCKLOS	block AI line of sight	Only visible to NPCs and bots. Transparent to players.
0x00000080	CONTENTS_OPAQUE	things that cannot be seen through (may be non-solid though)	Any player-visible brush that isn't translucent or transparent is opaque.
0x00000100	CONTENTS_TESTFOGVOLUME	(none)
0x00000200	CONTENTS_UNUSED	(none)
0x00000400 (removed since )	CONTENTS_UNUSED6	Unused NOTE: If it's visible, grab from the top + update LAST_VISIBLE_CONTENTS if not visible, then grab from the bottom.
0x00000400 (in all games since )	CONTENTS_BLOCKLIGHT		Not actually unused; comment is vestigial. Confirm:Is this in Left 4 Dead engine branch as well? Confirm:Can this block dynamic lights, unlike toolsblocklight?
0x00000800	CONTENTS_TEAM1	per team contents used to differentiate collisions between players and objects on different teams	Typically to set barriers that prevent one team from entering another team's spawn zone. Used in multiple games, including , but only able to be set via %CompileTeam in and newer.
0x00001000	CONTENTS_TEAM2
0x00002000	CONTENTS_IGNORE_NODRAW_OPAQUE	ignore CONTENTS_OPAQUE on surfaces that have SURF_NODRAW
0x00004000	CONTENTS_MOVEABLE	hits entities which are MOVETYPE_PUSH (doors, plats, etc.)
-----------------	-----------------	remaining contents are non-visible, and don't eat brushes	-----------------
0x00008000	CONTENTS_AREAPORTAL	(none)	Is an areaportal.
0x00010000	CONTENTS_PLAYERCLIP	(none)	Solid to players, including bots.
0x00020000	CONTENTS_MONSTERCLIP	(none)	Solid to monsters, better known in Source as NPCs. Also solid to bots in CSGO, even though they are players.
0x00040000 (removed since )	CONTENTS_CURRENT_0	currents can be added to any other contents, and may be mixed	Effectively identical to a trigger_push traveling the same direction. Mix these to go in diagonals.
0x00080000 (removed since )	CONTENTS_CURRENT_90
0x00100000 (removed since )	CONTENTS_CURRENT_180
0x00200000 (removed since )	CONTENTS_CURRENT_270
0x00400000 (removed since )	CONTENTS_CURRENT_UP
0x00800000 (removed since )	CONTENTS_CURRENT_DOWN
0x00040000 (in all games since )	CONTENTS_BRUSH_PAINT	N/A (source code not public)
0x00080000 (in all games since )	CONTENTS_GRENADECLIP	N/A (source code not public)
0x00100000 (in all games since )	CONTENTS_DRONECLIP	N/A (source code not public)
0x01000000	CONTENTS_ORIGIN	removed before bsping an entity	Coordinates of enter of the brush is written to the `origin` KV, to dictate the pivot point of certain entities.^{[ Deprecated]}
0x02000000	CONTENTS_MONSTER	should never be on a brush, only in game	Is a monster, better known in Source as an NPC.
0x04000000	CONTENTS_DEBRIS	(none)	Solid to point traces (ex hitscan weapons) and non-debris physics objects^[confirm]. Non-solid to QPhysics entities, such as players.
0x08000000	CONTENTS_DETAIL	brushes to be added after vis leafs	World brushes with these contents don't affect VIS. Brushes with these contents can be toggled with `r_drawfuncdetail`. Automatically given to any brushes in a func_detail. This flag is stripped from brushes which are part of a brush entity.
0x10000000	CONTENTS_TRANSLUCENT	auto set if any surface has trans	Used for alpha sorting on (non-detail) worldspawn brushes.
0x20000000	CONTENTS_LADDER	(none)	Is a ladder.
0x40000000	CONTENTS_HITBOX	use accurate hitboxes on trace
0x80000000	N/A	N/A (not defined)	Unused