bounding box Last edited 6 months ago2024-06-19 13:42:14 UTC

The axis-aligned bounding box (or just bounding box) of a brush entity is the cuboid that fits the entire brushwork of the entity (excluding origin and clip brushes).

In general, it is used by the game engine to determine if the entity should be rendered, by seeing if the entity's bounding box is within any of the visible areas (leafs) of the map.

Some entities that make use of their bounding box property include:

• A func_button, func_door, or similar entities, translates the volume of its bounding box when opening and closing (lip value is subtracted from this).
• A func_train positions itself along its path centered to the center of its bounding box.
• The travel height of a func_plat defaults to the height of the bounding box. The trigger field it creates also bases its horizontal dimensions to the bounding box.
• A func_pushable's collision is defined by the bounding box instead of its individual brushwork (though in majority of cases they coincide)

The BOUNDINGBOX tool texture allows you to set a custom bounding box for an entity. Some neat use cases:

• The glass part of a func_door that needs to move with its solid part can have the same lip value by having a BOUNDINGBOX brush the same width as the solid door.
• Or even completely ditching complicated lip math for complex func_door setups that travel farther than their physical width, and use BOUNDINGBOX as concrete, visual, geometric way to define movement distance.
• Precise positioning of a func_train without guesswork. Instead of placing path_corners right in the middle of the path you can, say, place them at the bottom of the entity. Use it just like an ORIGIN brush in other entities. (caveat: such func_trains might become invisible if the custom bounding box goes out of a visible leaf.)
• Make only part of a func_pushable solid. Same caveat as previous applies.

Related links

• Minimum bounding box on Wikipedia