View source for BSP flags (Quake and GoldSrc)

{{goldsrc topicon}}{{quake topicon}}
{{tabsBar|main=BSP flags}}
{{todo|Better page name; these aren't actually flags, except for the surface flags.}}
== Surface flags ==
Despite having a 32-bit integer available to be used, most flags go unused. Vanilla Quake engines and GoldSrc only use TEX_SPECIAL.
{| class="wikitable"
|-
! Bit !! Flag name !! Dev comment !! Notes
|-
| 0x00000001 || TEX_SPECIAL || sky or slime, no lightmap or 256 subdivision || Surface does not have a lightmap.
Used by {{quake}} [[QBSP]] to tell [[LIGHT (Quake compiler)|LIGHT]] to not generate lightmaps for sky and liquid surfaces, which are not subdivided to account for maximum lightmap size (15x15 luxels, or 240x240 texels). [[ericw-tools]] additionally uses this on surfaces textured with {{code|TRIGGER}}.

{{goldsrc}} [[QCSG]] and [[HLCSG]] set this flag on sky surfaces and surfaces textured with {{code|AAATRIGGER}}.
{{bug|[[QCSG]] and [[HLCSG]] still use {{code|<nowiki>*</nowiki>}} to declare liquids as not lightmapped, even though they are prefixed with {{code|!}} instead. Therefore, [[QRAD]] and [[HLRAD]] will always lightmap all liquid surfaces, unless they are flagged in some other manner, such as using {{newbspguy|4.1}}.}}
|-
| 0x00000002 || TEX_MISSING || johnfitz -- this texinfo does not have a texture || Used by fitzquake and derivatives to indicate a missing texture
|-
| 0x00000800 || ??? || N/A || Used by VERTEXNORMALS [[BSPX]] lump to indicate a face that should have smooth shading based upon its vertex normals. 
|-
| 0x00004000 || TEX_SHOULDHIDE || this flag is temporary; it might be set after CSG, but will be dropped after BSP || Used by [[VHLT]]; set if {{code|zhlt_hidden}} is set. Tells HLBSP to not add the face to any visleaves, and will result in HLRAD not reflecting light off of the face.

Texture names with the suffix {{code|_HIDDEN}} will yield the same result, without using this surface flag.
|-
|}

== Contents types ==
Contents are stored as a signed 32-bit integer, and are always negative.  
Some entities, such as {{ent|func_illusionary|eng=goldsrc}} and {{ent|func_water|eng=goldsrc}}, allow using the {{code|skin}} KV to override the contents of the entity.
{{clarify|Contents are stored in visleaves somehow, not directly in clipnodes.}}
{| class="wikitable"
|-
! Value !! Internal name !! Dev comment !! Notes
|-
| -1 || CONTENTS_EMPTY ||  || Non-solid, and doesn't affect VIS.
|-
| -2 || CONTENTS_SOLID ||  || Default.
|-
| -3 || CONTENTS_WATER ||  || A liquid, usually water. Textures with the {{code|!}} prefix are usually water when part of worldspawn, unless they are slime, lava, or a current.
|-
| -4 || CONTENTS_SLIME ||  || Like water, deals damage to the player and some monsters when touched.
|-
| -5 || CONTENTS_LAVA ||  || Like slime, but deals double the damage.
|-
| -6 || CONTENTS_SKY ||  || 
|-
| -7 || CONTENTS_ORIGIN || removed at csg time || Replaces an entity's {{code|origin}} KV, then is removed by CSG (does not exist in compiled BSP).
In GoldSrc, if a brush has this contents at runtime, it will be treated like water (and is referred to in FGDs as "volumetric light"). 
|-
| -8 || CONTENTS_CLIP || changed to contents_solid || 
|-
| -9 || CONTENTS_CURRENT_0 ||
| rowspan=6 | Acts like water combined with a {{ent|trigger_push (GoldSrc)|alt=trigger_push}} with a speed of 2048 in the given direction.<br>
In Quake, this is treated as regular water, being commented out with an {{code|<nowiki>#ifdef QUAKE2</nowiki>}}.
|-
| -10 || CONTENTS_CURRENT_90 ||  
|-
| -11 || CONTENTS_CURRENT_180 || 
|-
| -12 || CONTENTS_CURRENT_270 ||  
|-
| -13 || CONTENTS_CURRENT_UP ||  
|-
| -14 || CONTENTS_CURRENT_DOWN || 
|-
| -15 || CONTENTS_TRANSLUCENT {{quake|not}} ||  || Like water, but never solid. Despite this, it still affects VIS.
|-
| -16 || CONTENTS_LADDER {{quake|not}} ||  || Climbable. Usually set via the game code for the func_ladder entity.
|-
| -17 || CONTENTS_FLYFIELD {{quake|not}} ||  || Zero gravity
|-
| -18 || CONTENTS_GRAVITY_FLYFIELD {{quake|not}} ||  || 
|-
| -19 || CONTENTS_FOG {{quake|not}} ||  || 
|-
|}

== Ambient Types ==
Ambients are stored as an array of 4 unsigned bytes, indicating volume. Only Quake uses them, and it only uses AMBIENT_SKY and AMBIENT_WATER, which are hardcoded in the engine to play specific sounds when a visleaf containing the given ambient type is in the current PVS.

{{confirm|Probably only affected by world brushes, so probably not cast by func_water.}}

{| class="wikitable"
|-
! Index !! Name !! Notes
|-
| 0 || AMBIENT_WATER || Normally cast by any liquid ({{code|<nowiki>*</nowiki>}} prefix in {{quake}}; {{code|!}} prefix in {{goldsrc}}), unless they are slime or lava.
|-
| 1 || AMBIENT_SKY || Normally cast by sky brushes ({{code|sky}} prefix)
|-
| 2 || AMBIENT_SLIME || Normally cast by slime brushes ({{code|<nowiki>*slime</nowiki>}} prefix in {{quake}}; {{code|!slime}} prefix in {{goldsrc}})
|-
| 3 || AMBIENT_LAVA || Normally cast by lava brushes ({{code|<nowiki>*lava</nowiki>}} prefix in {{quake}}; {{code|!lava}} prefix in {{goldsrc}})
|}

== See also ==
* [[Texture prefixes]]