Collision¶

Every Gameplay pack brush entity and every model entity collides without you setting anything. Doors, buttons, lifts, trains and triggers get a convex hull per brush, and prop_model, prop_physics, npc_walker and scatter props get a shape built from their model. You only touch the keys below when the default does not fit.

The keys¶

Select the entity and find these rows in the Inspector. Hover a row to read what each choice does.

The Inspector of a func_door with the collision menu open on default, none, box, convex hull, convex decomposition and trimesh, the collision_layer and collision_mask rows below it

Key	Default	What it does
`collision`	default	The shape: default, none, box, convex hull, convex decomposition or trimesh
`collision_layer`	empty	The physics layers the body is on, as layer numbers such as `1, 3`. `none` puts it on no layer
`collision_mask`	empty	The physics layers the body detects, in the same form. `none` detects nothing

An empty layer or mask keeps the default: the entity definition's layer and mask for brush entities, with triggers taking Trigger Collision Mask from the map settings, and the project settings below for model entities.

Picking a shape¶

Shape	Brush entities	Models
default	The class shape, a convex hull per brush	The project setting, a convex hull per mesh unless changed. `prop_physics` uses a box from `size`
none	No collision	No collision
box	One box around all brushes	One box around the model, the cheapest shape
convex hull	A hull per brush	A hull per mesh, fine for boxy models
convex decomposition	Same as convex hull, a brush is convex already	Several hulls that follow a concave model like an arch, slower to build
trimesh	Every face, for static bodies only	Every triangle, exact but the most expensive

Trimesh only works on static bodies. Doors, buttons, lifts and trains are animatable bodies, which count as static, so they can use it. Triggers, prop_physics and npc_walker build convex hulls instead, and a trigger set to trimesh reports a warning when the map builds.

A prop_model whose model already holds a collision body keeps that body and builds no shape of its own.

Project defaults¶

Model entities whose keys are empty follow three settings in Godot's Project Settings, under Trenchdot > Collision. They appear once the TrenchDot plugin is enabled.

Setting	Default	What it does
Model Shape	convex	The shape default stands for on `prop_model` and `npc_walker`
Model Layer	1	The layer model bodies are on
Model Mask	1	The layers model bodies detect

Scatter sets pick their shape in the scatter set's own Collision row, see Scatter.

Your own brush entities¶

A brush entity you define yourself collides as the body its Node Class names. With Node Class left empty it takes the body its script extends, and with no script, or a script extending Node3D, it becomes a StaticBody3D. Only a script extending some other node, such as a Marker3D, leaves it without collision, and the build warns about it. See Custom entities in GDScript.

The editor viewport does not draw collision shapes. Godot's Debug > Visible Collision Shapes shows them while the game runs, in the live session and in a full build alike. Brush entities and prop_model save their shapes in the built scene, prop_physics and npc_walker build theirs each time the scene loads, the way they load their model. A prop_model or npc_walker whose model scene already holds a physics body keeps that body and builds no shapes of its own.