View source for Prop physics

{{CD|CPhysicsProp|file1=props.cpp}}
{{this is a|point entity|name=prop_physics}} It is used to add rigid, [[VPhysics]]-simulated [[model]]s to the world.

The only value required for prop_physics to work is a path to a model. As long as that model is [[prop_data|physics-enabled]], the correct data will be loaded from it when the map starts. It is possible to change any embedded physics data with the "Override Parameters" keyvalue.

Physics objects like <code>prop_physics</code> can be [[Parent|parented]], though it is not in the default [[FGD]] and may not function correctly. It is recommended to instead use dynamic physics constraints. See [[Physics Entity Overview]] for more information.
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{{tip|Multiplayer maps should use {{ent|prop_physics_multiplayer}}, which works better with the collision prediction code.<br>Do not use {{ent|prop_physics_respawnable}}; it will crash the server if destroyed by a trigger_hurt.}}
{{tip|To create a jointed physics object, use {{ent|prop_ragdoll}}.}}

{{altnames|name1=physics_prop|misc=The classname is always changed to {{ent|prop_physics}} on spawn.}}

== Consistency ==
{{todo|Move this section to its own article.}}

Consistency becomes a large problem when dealing with the many prop models that the Source engine provides. From a player's perspective, object interactivity should remain consistent across all the levels of your game / mod, as players will often have a hard time solving puzzles or making quick decisions if the prop's behaviour is different in only one specific instance. To enforce this, the game-related data of props is stored within the model itself.

For example, imagine you have a crate that is immovable for the entirety of your game and the player has gotten used to that crate being static. However, in one specific instance, this crate is not moveable and required to be moved to proceed. This can cause lots of irritation and confusion, and therefore is why consistency is necessary. Oftentimes, developers will use different skins or models to convey differences in behaviour and keep consistency.

Models that are meant to be physically simulated (chairs, tables, wooden planks, etc) will remove themselves if they are placed as {{ent|prop_static}} or {{ent|prop_dynamic}} entities (You can still use these as static props using the entity {{ent|prop_dynamic_override}}). Other game-related data, such as mass, "health", gib amount & models, and so on are all stored inside the prop model as well.

The method by which they are stored, and guidelines for how to set it up, can be found in the [[Prop Data]] section of the model's QC file.

== Keyvalues ==
{{KV Targetname}}
{{minititle|BasePropPhysics}}
{{KV|Physics Impact Damage Scale|intn=physdamagescale|float|Multiplies damage received from physics impacts. 0 means the feature is disabled for backwards compatibility.|nofgd={{{nofgd|}}}}}
{{KV|Impact damage type|intn=Damagetype|bool|If true (1), damage type is sharp and the object can slice others.|nofgd={{{nofgd|}}}}}
{{KV|Damaging it Doesn't Push It|intn=nodamageforces|bool|Whether damaging the entity applies force to it.|nofgd={{{nofgd|}}}}}
{{KV|Scale Factor For Inertia|intn=inertiascale|float|Scales the angular mass of an object. Used to hack angular damage and collision response. {{confirm|Doesn't actually affect ''inertia''?}}|nofgd={{{nofgd|}}}}}
{{KV|Mass Scale|intn=massscale|float|Multiplier for the object's mass.|nofgd={{{nofgd|}}}}}
{{KV|Override Parameters|intn=overridescript|string|A list of physics keyvalues that are usually [[prop_data|embedded in the model]]. Format is <code>key,value,key,value,…</code>.|nofgd={{{nofgd|}}}}}
{{KV|Health Level to Override Motion|intn=damagetoenablemotion|int|If specified, this object will start with motion disabled. Once its health has dropped below this specified amount, it will enable motion.|nofgd={{{nofgd|}}}}}
{{KV|Physics Impact Force to Override Motion|intn=forcetoenablemotion|float|If specified, this object will start motion disabled. Any impact that imparts a force greater than this value will enable motion.|nofgd={{{nofgd|}}}}}
{{KV BreakableProp}}
{{KV GMOD|nofgd={{{nofgd|}}}}}
{{KV Studiomodel|noscroll=1|no sequence=1}}

== Flags ==
{{minititle|BasePropPhysics}}
{{fl|1|[[Physics optimization|Start Asleep]]}}
{{fl|2|Don't take physics damage}}
{{fl|4|[[Physics optimization|Debris]]|Don't collide with the player or other debris.}}
{{fl|8|[[Physics optimization|Motion Disabled]]|Starts with motion disabled until sent EnableMotion.}}
{{fl|64|Enable motion when grabbed by gravity gun}}
{{fl|128|Not affected by [[rotor wash]]}}
{{fl|256|Generate output on {{cmd|+use}}|Whether to generate <code>OnPlayerUse</code> output}}
{{fl|512|Prevent pickup}}
{{fl|1024|Prevent motion enable on player bump.}}
{{fl|2048|Has Attached Ragdolls|Set by the game when ragdolls are attached, detaches them when prop moves|nofgd=1}}
:{{Note|Used solely by props with the "impale" [[Prop interactions|prop interaction]] (PROPINTER_PHYSGUN_FIRST_IMPALE), such as the harpoons in {{hl2|1.bold}} (not to be confused with the [[weapon_crossbow|crossbow]] bolts, which use a different method for pinning ragdolls). It is best not to assign this spawnflag manually.}}
{{fl|4096|Debris with [[trigger]] interaction.}}
:{{Note|Does not enable Debris behavior on its own. Needs to be used together with the Debris spawnflag ''or'' with the <code>PROPINTER_PHYSGUN_CREATE_FLARE</code> prop interaction.}}
{{fl|8192|Force server-side|Multiplayer only; see {{ent|sv_pushaway_clientside_size}}.}}
:{{bug|In {{l4ds}} when breakable prop has Force server-side flag set then nav areas under it will be marked MOB_ONLY|tested=l4d2}}
{{fl|16384|Radius Pickup|Makes objects easier to grab|nofgd=1}}
{{fl|1048576|Gravity gun can ALWAYS pick up. No matter what.}}
{{fl|2097152|No Collisions|Disable collisions on spawn|nofgd=1}}
{{fl|4194304|Gib|If debris, remove when stuck in a collision|nofgd=1}}
{{fl|4194304|Attempt to override gib with the character gib system|only=BMS}}
{{fl|8388608|[[Npc_zombie|Zombies]] can't swat|Zombies will ignore this prop when looking for an object to swat at the enemy.|only=Mapbase}}
{{Fl BreakableProp}}

== Inputs ==
{{minititle|BasePropPhysics}}
{{IO|Sleep|Tell the prop to quit moving. Any physics forces (excluding gravity and water buoyancy) will cause the object to resume moving as usual. Sleeping also occurs automatically when the object has no physics forces to keep it awake, and when it is no longer moving a noticeable amount.|nofgd={{{nofgd|}}}}}
{{IO|Wake|If the object was told to sleep, tell it to start moving again.|nofgd={{{nofgd|}}}}}
{{IO|DisableMotion|Tell the object to stop moving completely. No physics forces will re-enable motion, not even <code>Wake</code>.|nofgd={{{nofgd|}}}}}
{{IO|EnableMotion|If the object's motion has been disabled entirely, tell it to resume movement as usual. This will also <code>Wake</code> the object, if it is <code>Sleep</code>ing.|nofgd={{{nofgd|}}}}}
{{IO|DisableFloating|If the object would normally float when in water, tell it not to float. There seems to be no way to re-enable floating behavior, but programming a method to do this should be fairly simple (<code>CALLBACK_DO_FLUID_SIMULATION</code>).|nofgd={{{nofgd|}}}}}
{{I BreakableProp}}

== Outputs ==
{{IO|OnMotionEnabled|Fired when motion has been enabled on the prop, either via the '''Health Level to Override Motion''' keyvalue or from the <code>EnableMotion</code> input.}}
{{IO|OnAwakened|Fired when the prop has woken (force has been applied to it while it was asleep, or the <code>Wake</code> input has been called).}}
{{IO|OnOutOfWorld|Fired whenever the object is detected to be outside the world. Specifically, it checks if the object is outside of the world's [[bounding box]] or if the object is traveling at over 2000 units per second in any cardinal direction.}}
{{IO|OnPlayerUse|Fired when the player has {{ent|+use}}d the prop.
{{bug*|tested={{css}}|{{ent|!activator}}, as well as {{ent|!caller}} are the physics prop itself!}}
{{note|This output (but not any of the other pickup-related ones) will fire only if the ''Generate output on +USE'' spawnflag is set.}}}}
{{IO|OnPhysGunDrop|Fired when the player has dropped the prop (from either <code>+use</code> or the gravity gun). {{ent|!activator}} is the player.}}
{{IO|OnPlayerPickup|Fired when the player has picked the prop up with <code>+use</code> or the gravity gun (in ''Half-Life 2'').}}
{{IO|OnPhysGunOnlyPickup|Fired when the player has picked the prop up with the gravity gun specifically.|since={{hl2}}}}
{{IO|OnHitByTank|since=l4d2|Fired when the prop has been punched by a Tank boss infected.}}
{{O BreakableProp}}

== See also ==
* {{ent|prop_data}}
* [[Prop Types Overview]]
** {{ent|prop_physics_multiplayer}}
** {{ent|prop_physics_respawnable}}
** {{ent|prop_physics_override}}
** {{ent|prop_sphere}}
** {{ent|prop_dynamic}}
** {{ent|prop_static}}
** {{ent|prop_ragdoll}}

[[Category:Physics]]
[[Category:Prop entities|physics]]