Wiki: Brush Entity

Brush entities are one of the two types of entity. A brush entity is comprised of one or more brushes, and thus are entities that either define an area or make up some part of the level geometry. This includes doors, elevators, trains, buttons and more, as well as areas that trigger some element of game logic, such as causing damage to the player or activating other entities when the player enters them.

Brush entities have a few properties of interest that are only defined geometrically (not through entity keyvalues):

The origin defines the center of rotation of some entities. Also the center of targeting entities like env_beam, and entity effects. Defaulting to the world origin (0 0 0), it can be configured by including the origin brush.
BOUNDINGBOX
The bounding box describes a cuboid that contains all solid geometry of the entity. It is the center of movement for func_trains, and also the total volume entities like func_button or func_door translates to when opening (the lip is subtracted from this). Likewise can be customized with the BOUNDINGBOX brush.
Clip hulls, which defines collision. If removed via zhlt_noclip keyvalue, players will not collide with it in any way, and this effect is not limited to func_illusionary. Brush triggers without clip hulls will not work for the respective hulls that are missing. Conversely, clip hulls can be added [back] with CLIP brushes or its respective hull-specific variants. zhlt_noclip + CLIP brushes is a useful strategy to simplify clipnodes on otherwise very detailed brushwork.

Some other properties applicable to brush entities in common (via various means):

Render FX/Mode/Amount - Sets how entities would render in game. Not applicable to triggers.
Entity Effects (effects) - Another, seldom-documented effect property that mostly emits light or other effects from the entity's origin.
Contents (skin) - Describes the content of the volume inside the entity. Mostly only relevant to func_water, but can theoretically apply such properties to any brush entity.

Compiler keyvalues with no effect on entity's function:

Light Origin Target (light_origin) - Make entity receive lighting from the position of the targeted entity. An origin brush is needed.
Minimum light level (_minlight)
ZHLT Lightflags (zhlt_lightflags)
zhlt_usemodel - Reuse the same brush model (and its hulls) as the targeted entity. This saves 1 brush model slot (of 512) for every use. Be aware that shared brush models share lighting and decals.

💡 If you want, you can edit your FGDs to expose the common properties above to all brush entities. One easy way is to extend the ZHLT BaseClass since most brush entities inherit it in most FGDs.

Advanced property: `model`

In the .map file format, everything is fundamentally part of an entity. Brush entities are entities that have brushes. World brushes are actually brushwork for the worldspawn entity.

During compilation, the brushwork of entities are compiled into brush models (there can be 512 of these) and divorced from the resulting entity lump which now holds pure entity data. In return, the entities get assigned a model keyvalue which points to the index into the BSP file's brush model list. Multiple entities sharing this value will share the same brush model and this can be set up with the zhlt_usemodel keyvalue. It can even point to an external BSP file e.g. models/healthbox.bsp or an actual model e.g. models/prop/door.mdl (note: models use different kind of collision and thus absent if used like this). There doesn't seem to be a way to explicitly set model value in the editor short of redefining the FGDs, and such edits are usually done with post-compile tools like bspguy.

kimilil

Commented 6 months ago2024-04-18 14:33:31 UTC Comment #106136

My FGD's ZHLT BaseClass is like this:

fgd
@BaseClass = ZHLT
[
    zhlt_lightflags(choices) : "ZHLT Lightflags" : 0 =
    [
        0 : "Default"
        1 : "Embedded Fix"
        2 : "Opaque (blocks light)"
        3 : "Opaque + Embedded fix"
        6 : "Opaque + Concave Fix"
    ]
    light_origin(string) : "Light Origin Target"
    zhlt_hull1(target_destination) : "info_hullshape (standing)"
    zhlt_hull2(target_destination) : "info_hullshape (big monsters)"
    zhlt_hull3(target_destination) : "info_hullshape (crouching)"
    zhlt_usemodel(target_destination) : "ZHLT Template Model Target"
    zhlt_copylight(target_destination) : "ZHLT Copy Lighting From Target"
    zhlt_noclip(choices) : "ZHLT No-clipping" : "" =
    [
        "" : "Default clipping"
        1 : "No clip"
    ]
    zhlt_invisible(choices) : "ZHLT Invisibility" : "" =
    [
        "" : "Default (visible)"
        1 : "Invisible"
    ]
    zhlt_customshadow(string) : "ZHLT custom shadow (Alpha/RGB)" : : "Float value that specifies opacity of this brush entity. 0.0 (opaque) -> 1.0 (no shadow). Enter three values for RGB."
    zhlt_embedlightmap(choices) : "ZHLT embed lightmap" : "" =
    [
        "" : "No"
        1 : "Yes"
    ]
    zhlt_embedlightmapresolution(choices) : "ZHLT embed lightmap resolution" : "" =
    [
        "" : "[UNSET]"
        1  : "1 "
        2  : "2 "
        4  : "4 "
        8  : "8 "
        16 : "16"
        32 : "32"
        64 : "64"
    ]
    skin(choices) : "Contents" : "" =
    [
        ""  : "[UNSET]"
        -1  : "Empty"
        -2  : "Solid"
        -3  : "Water"
        -4  : "Slime"
        -5  : "Lava"
//        -6  : "Sky"
        -15 : "Translucent"
        -16 : "Ladder"
        -17 : "Fly field"
        -18 : "Gravity fly field"
        -19 : "Fog"
    ]
]

Brush Entity Last edited 8 months ago2024-02-20 00:34:15 UTC

Advanced property: `model`

1 Comment

Brush Entity Last edited 8 months ago2024-02-20 00:34:15 UTC

Advanced property: model

1 Comment

Advanced property: `model`