prop_physics

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prop_physics is a point entity available in all Source games. It is used to add rigid, VPhysics-simulated models to the world.

The only value required for prop_physics to work is a path to a model. As long as that model is 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.

Tip:Multiplayer maps should use prop_physics_multiplayer or prop_physics_respawnable. To create a jointed physics object, use prop_ragdoll.
Note:prop_physics can be parented if the 'parentname' value is manually added with smartedit turned off. Parenting prop_physics can be unpleasant and buggy in some situations.

Consistency

To do: 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. (Why? Shouldn't the level designer have control over this, dependent on the context of the prop's use?) To enforce this, the game-related data of props is stored within the model itself.

Models that are meant to be physically simulated (chairs, tables, wooden planks, etc) will remove themselves if they are placed as prop_static or prop_dynamic entities. 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.

See also

Keyvalues

BasePropPhysics:

Physics Impact Damage Scale (physdamagescale) <float>
Multiplies damage received from physics impacts. 0 means the feature is disabled for backwards compatibility.
Impact damage type (Damagetype) <boolean>
If true (1), damage type is sharp and the object can slice others.
Damaging it Doesn't Push It (nodamageforces) <boolean>
Whether damaging the entity applies force to it.
Scale Factor For Inertia (inertiascale) <float>
Scales the angular mass of an object. Used to hack angular damage and collision response.
Confirm:Doesn't actually affect inertia?
Mass Scale (massscale) <float>
Multiplier for the object's mass.
Override Parameters (overridescript) <string>
A list of physics keyvalues that are usually embedded in the model. Format is key,value,key,value,....
Health Level to Override Motion (damagetoenablemotion) <integer>
If specified, this object will start with motion disabled. Once its health has dropped below this specified amount, it will enable motion.
Physics Impact Force to Override Motion (forcetoenablemotion) <float>
If specified, this object will start motion disabled. Any impact that imparts a force greater than this value will enable motion.

DXLevelChoice:

Minimum DX Level (mindxlevel) <choices>
The entity will not exist if the engine is running outside the given range of DirectX Versions. Replaced by SystemLevelChoice from <Left 4 Dead> Left 4 Dead onwards.
Warning: If these are used, the object may break when the user switches their DirectX settings.
Maximum DX Level (maxdxlevel) <choices>

SystemLevelChoice:

Minimum CPU Level (mincpulevel) <choices> (New with Left 4 Dead)
A user with a CPU level lower than this will not see this object rendered in-game. CPU levels are determined by the Effect detail setting.
Maximum CPU Level (maxcpulevel) <choices> (New with Left 4 Dead)
  • 0: Default
  • 1: Low
  • 2: Medium
  • 3: High
Minimum GPU Level (mingpulevel) <choices> (New with Left 4 Dead)
A user with a GPU level lower than this will not see this object rendered in-game. GPU levels are determined by the Shader detail setting.
Maximum GPU Level (maxgpulevel) <choices> (New with Left 4 Dead)
  • 0: Default
  • 1: Very low
  • 2: Low
  • 3: Medium
  • 4: High

GMODSandbox:

Allow Physics Gun (gmod_allowphysgun) <boolean> (Only in Garry's Mod)
If set, players cannot use Physics Gun on this entity.
Sandbox Tool Whitelist (gmod_allowtools) <string> (Only in Garry's Mod)
If set, only given tools can be used on this entity. You need to supply the tool class names, the names of the .lua files of those tools. This also includes the context menu properties!

RenderFields:

Render Mode (rendermode) <choices>
Set a non-standard rendering mode on this entity.
Render FX / Transparency (0 - 255) (renderamt) <integer>
Transparency amount, requires a Render Mode other than Normal. 0 is invisible, 255 is fully visible.
Render Color (R G B) (rendercolor) <color255>
Color tint.
Disable Receiving Shadows (disablereceiveshadows) <boolean>
Prevent the entity from receiving shadows on itself.

RenderFXChoices:

Render FX (renderfx) <choices>
Preset pattern of appearance effects.
To do: 18-21, 25

Flags

BasePropPhysics:

  • 1: Start Asleep.
  • 2: Don't take physics damage.
  • 4: Debris - Don't collide with the player or other debris.
  • 8: Motion Disabled.
  • 64: Enable motion when grabbed by gravity gun.
  • 128: Not affected by rotor wash.
  • 256: Generate output on +use.
  • 512: Prevent pickup.
  • 1024: Prevent motion enable on player bump.
  • 4096: Debris with trigger interaction.
  • 8192: Force server-side (Multiplayer only; see sv_pushaway_clientside_size)
  • 1048576: Gravity gun can ALWAYS pick up. No matter what.

BreakableProp:

  • 16: Break on Touch
  • 32: Break on Pressure

Inputs

Ignite
Ignite, burst into flames.
IgniteLifetime  <float>
Ignite with the given lifetime. To do: Before the flames extinguish, or before health reaches zero?
IgniteNumHitboxFires  <integer>
Ignite with the given number of hitbox fires.
IgniteHitboxFireScale  <float>
Ignite with the given hitbox fire scale.

BasePropPhysics:

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.
Wake
If the object was told to sleep, tell it to start moving again.
DisableMotion
Tell the object to stop moving completely. No physics forces will re-enable motion, not even Wake.
EnableMotion
If the object's motion has been disabled entirely, tell it to resume movement as usual. This will also Wake the object, if it is Sleeping.
DisableFloating
If the object would normally float when in water, tell it to not float. There seems to be no way to re-enable floating behavior, but programming a method to do this should be fairly simple (CALLBACK_DO_FLUID_SIMULATION).

RenderFields:

Alpha  <integer>
Sets the entity's transparency to a number from 0 (invisible) to 255 (fully visible). Requires the entity to have its Render Mode (rendermode) set to a number other than 0.
Color  <color255>
Sets an RGB color for the entity.

Outputs

BasePropPhysics:

OnMotionEnabled
Fired when motion has been enabled on the prop, either via the Health Level to Override Motion keyvalue or from the EnableMotion input.
OnAwakened
Fired when the prop has woken (force has been applied to it while it was asleep, or the Wake input has been called).
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.
OnPlayerUse
Fired when the player has +used the prop.
Note:This output (but not any of the other pickup-related ones) will fire only if the Generate output on +USE spawnflag is set.
OnPhysGunDrop
Fired when the player has dropped the prop (from either +use or the gravity gun). !activator is the player.
OnPlayerPickup
Fired when the player has picked the prop up with +use or the gravity gun (in Half-Life 2).
OnPhysGunOnlyPickup
Fired when the player has picked the prop up with the gravity gun specifically.

physics_prop

physics_prop is the predecessor name to prop_physics. It was used in early Half-Life 2 Beta maps, before being replaced by prop_physics later in development. This classname links to the same entity and the classname is also replaced with prop_physics after spawning.