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prop_sphere is a point entity available in all Source games. It is not in any of Valve's FGDs, however.

It is essentially a prop_physics with a perfectly spherical VPhysics collision model. If you want to create an spherical entity, it is far more efficient to use prop_sphere than try to create a spherical collision mesh!

Tip:The only spherical model in Half-Life 2 is models\combine_helicopter\helicopter_bomb01.mdl.
Bug: The collision mesh will not be visible with the vcollide_wireframe 1 command.

Stock FGD

If you don't intend to make any changes to the entity's C++ code, use this:

@PointClass base(BasePropPhysics, RenderFields) studioprop() = prop_sphere : "Creates a perfect sphere."

Extending prop_sphere

Visit this snippet, on how you can improve the existing prop_sphere code.

Stock Keyvalues


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.


Minimum DX Level (mindxlevel)<choices>
Maximum DX Level (maxdxlevel)<choices>
The entity will not exist if the engine is running outside the given range of DirectX Versions. Only used by Orange Box and 2013 SDK games.
Warning: If these are used, the object may break when the user switches their DirectX settings.
  • Default (no bounding)
  • DX7
  • DX8
  • DX8.1
  • DX9 SM2
  • DX9 SM3


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.


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

Stock Flags


  • 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.


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

Stock Inputs


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.
If the object was told to sleep, tell it to start moving again.
Tell the object to stop moving completely. No physics forces will re-enable motion, not even Wake.
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.
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).


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.

Stock Outputs


Fired when motion has been enabled on the prop, either via the Health Level to Override Motion keyvalue or from the EnableMotion input.
Fired when the prop has woken (force has been applied to it while it was asleep, or the Wake input has been called).
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.
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.
Fired when the player has dropped the prop (from either +use or the gravity gun). !activator is the player.
Fired when the player has picked the prop up with +use or the gravity gun (in Half-Life 2).
Fired when the player has picked the prop up with the gravity gun specifically.