Swing the doors open

sermuns commented

2026-10-20 23:40:45 +00:00

Owner

Doors are missing from the campus in a way that is easy to miss, because the
bake does draw them: MazeMap's interior walls carry door ribbons, and the
collider deliberately ignores them — ARCHITECTURE.md says interior walls have
"door ribbons never" blocking on their own floors. So a door is drawn on the
wall and there is no opening in it.

The building shell is different: an OSM entrance=* or door=* snapped to a
building edge becomes a gap in the collision wall, and that gap is the
only door in the campus today. There is no door that opens, no door that
swings, and no way for a player to hold one.

A hinge is a revolute joint with a motor, and a motor is two lines of Rapier:
set_motor_position(axis, target, stiffness, damping) and
set_motor_max_force(axis, max_force). The door is then a rigid body with a
handle you can push.

What it buys

Doors that open. Press E on a door and it swings. Walk into one and it
swings out of the way, if it is a door and not a wall.
A door held open. One player holds a door for another. This is the
multiplayer payoff, and it is the same kind of moment as the bus ride: a
small physical thing that two people share.
Doors that are closed because something is behind them. A swinging door
that knocks a player over is a physics engine being used for a joke.

Where it fits

The door ribbons are already baked — they are part of the interior wall data —
so this is not a bake change for the geometry. It is a bake change for the
collider, because a door with a gap is a different collider from a wall, and
the collision layer the physics engine needs has to be able to say "this
segment is a door, and the door has a hinge at this end".

The door body is a SceneSpec object slot like a vehicle: it moves, and it is
not part of the static campus.

The authority question

A door is shared, so it cannot be client-authoritative: two clients would
each swing their own door and the two would not agree. It is server-authoritative
like the vehicles, which means a door's angle is a number on the wire at 20 Hz.
That is the same shape as VehiclePose — an id, a position, an angle — so the
protocol already has a precedent for it.

The cost is a busier SceneSpec: the campus currently has a few hundred
moving objects at most, and every door on campus becomes one.

Related

#110 the physics engine itself is the blocker.
The interior wall collision is the same code, and it is where the door gaps
are punched.
The walking character controller is what makes the door matter, since today
a door is a wall you walk through.

Doors are missing from the campus in a way that is easy to miss, because the bake does draw them: MazeMap's interior walls carry door ribbons, and the collider deliberately ignores them — ARCHITECTURE.md says interior walls have "door ribbons never" blocking on their own floors. So a door is drawn on the wall and there is no opening in it. The building shell is different: an OSM `entrance=*` or `door=*` snapped to a building edge becomes a **gap** in the collision wall, and that gap is the only door in the campus today. There is no door that opens, no door that swings, and no way for a player to hold one. A hinge is a revolute joint with a motor, and a motor is two lines of Rapier: `set_motor_position(axis, target, stiffness, damping)` and `set_motor_max_force(axis, max_force)`. The door is then a rigid body with a handle you can push. **What it buys** - **Doors that open.** Press `E` on a door and it swings. Walk into one and it swings out of the way, if it is a door and not a wall. - **A door held open.** One player holds a door for another. This is the multiplayer payoff, and it is the same kind of moment as the bus ride: a small physical thing that two people share. - **Doors that are closed because something is behind them.** A swinging door that knocks a player over is a physics engine being used for a joke. **Where it fits** The door ribbons are already baked — they are part of the interior wall data — so this is not a bake change for the geometry. It is a bake change for the *collider*, because a door with a gap is a different collider from a wall, and the collision layer the physics engine needs has to be able to say "this segment is a door, and the door has a hinge at this end". The door body is a `SceneSpec` object slot like a vehicle: it moves, and it is not part of the static campus. **The authority question** A door is shared, so it cannot be client-authoritative: two clients would each swing their own door and the two would not agree. It is server-authoritative like the vehicles, which means a door's angle is a number on the wire at 20 Hz. That is the same shape as `VehiclePose` — an id, a position, an angle — so the protocol already has a precedent for it. The cost is a busier `SceneSpec`: the campus currently has a few hundred moving objects at most, and every door on campus becomes one. **Related** - #110 the physics engine itself is the blocker. - The interior wall collision is the same code, and it is where the door gaps are punched. - The walking character controller is what makes the door matter, since today a door is a wall you walk through.

sermuns added this to the Buildings & landmarks milestone

2026-10-20 23:40:45 +00:00

sermuns added the

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feature request

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2026-10-20 23:40:45 +00:00

sermuns referenced this issue

2026-10-20 23:41:18 +00:00

Add a physics engine (rapier3d) #110

sermuns added the

blocked