BSP flags (Source)

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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.

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. Confirm:Can the value field be set in a VMF, or does it require regressing to MAP instead?
0x0002	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
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	Confirm:This was for Quake I-style water/slime/lava in ; does this still work?
0x0010	SURF_TRANS	(None)	Surface is translucent, either via $translucent or $alpha. Confirm:Might also apply to $alphatest.
0x0020	SURF_NOPORTAL	the surface can not have a portal placed on it	Set via %NoPortal
0x0040	SURF_TRIGGER	FIXME: This is an xbox hack to work around elimination of trigger surfaces, which breaks occluders	Set via %CompileTrigger Confirm:Might also do something if VRAD is run with -nodrawtriggers.
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 . Confirm:Might be set automatically on UnlitGeneric materials.
0x0800	SURF_BUMPLIGHT	calculate three lightmaps for the surface for bumpmapping	Implied by $bumpmap. This is probably why ssbumps are cheaper to render than regular normal maps.
0x1000	SURF_NOSHADOWS	Don't receive shadows	Confirm:Might be dictated by 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?]

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	Official description	Notes
0x00000000	CONTENTS_EMPTY	No contents
0x00000001	CONTENTS_SOLID	an eye is never valid in a solid
0x00000002	CONTENTS_WINDOW	translucent, but not watery (glass)
0x00000004	CONTENTS_AUX	(none)
0x00000008	CONTENTS_GRATE	alpha-tested "grate" textures. Bullets/sight pass through, but solids don't
0x00000010	CONTENTS_SLIME	(none)
0x00000020	CONTENTS_WATER	(none)
0x00000040	CONTENTS_BLOCKLOS	block AI line of sight
0x00000080	CONTENTS_OPAQUE	things that cannot be seen through (may be non-solid though)
0x00000100	CONTENTS_TESTFOGVOLUME	(none)
0x00000200	CONTENTS_UNUSED	(none)
0x00000400	CONTENTS_UNUSED6	Unused NOTE: If it's visible, grab from the top + update LAST_VISIBLE_CONTENTS if not visible, then grab from the bottom.
0x00000800	CONTENTS_TEAM1	per team contents used to differentiate collisions between players and objects on different teams
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)
0x00010000	CONTENTS_PLAYERCLIP	(none)
0x00020000	CONTENTS_MONSTERCLIP	(none)
0x00040000	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	CONTENTS_CURRENT_90
0x00100000	CONTENTS_CURRENT_180
0x00200000	CONTENTS_CURRENT_270
0x00400000	CONTENTS_CURRENT_UP
0x00800000	CONTENTS_CURRENT_DOWN
0x01000000	CONTENTS_ORIGIN	removed before bsping an entity
0x02000000	CONTENTS_MONSTER	should never be on a brush, only in game
0x04000000	CONTENTS_DEBRIS	(none)
0x08000000	CONTENTS_DETAIL	brushes to be added after vis leafs	Automatically given to any brushes in a func_detail.
0x10000000	CONTENTS_TRANSLUCENT	auto set if any surface has trans	Used for alpha sorting on worldspawn brushes.
0x20000000	CONTENTS_LADDER	(none)
0x40000000	CONTENTS_HITBOX	use accurate hitboxes on trace
0x80000000	N/A	(none)	Unused