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# Actor/Collision

UT2003 :: Object >> Actor (Property Group: Collision)

Properties that control how an actor blocks other actors. For the UT version, see Actor (UT)/Collision.

The difference between Blocking and Colliding is that Colliding actors only get a Touch() event when another object collides with it; Blocking actors also prevent the other object from moving to that location. Actors can be made to do none, either, or both.

bool bAutoAlignToTerrain
  Auto-align to terrain in the editor
bool bBlockActors
  Blocks other nonplayer actors.
bool bBlockKarma
  Block actors being simulated with Karma.
bool bBlockNonZeroExtentTraces
  Blocks actors with CollisionRadius and CollisionHeight greater zero. Also traces that use the Extent parameter will hit this actor.
bool bBlockPlayers
  Blocks other player actors.
bool bBlockZeroExtentTraces
  Blocks actors with CollisionRadius and CollisionHeight set to zero. Also traces that don't use the Extent parameter will hit this actor.
bool bCollideActors
  Collides with other actors.
bool bCollideWorld
  Collides with the world.
bool PathColliding
  Nytro: I think this means that bot paths wont't be affected by its collision. I'll test that soon.
bool bProjTarget
  Projectiles should potentially target this actor.
bool bUseCylinderCollision
  use a collision cylinder, set the size with the next two properties
float CollisionHeight
  Half-height of the collision cylinder
float CollisionRadius
  Radius of the collision cylinder
ESurfaceTypes SurfaceType

## Practical

So, the above is great, but what do I need to set to get ...

- a Static mesh that doesn't block players
- one that has no collision overhead

Tarquin: Dumb question, but if you set bUseCylinderCollision to false, what determines where the actor collides?

MythOpus: I believe Karma makes collisions on it's own using the polygons in the model but if that is turned of (I forget what property) then I don't think an actor will collide with it.

## Related topics

- OCD – Technical lowdown of object collision detection.
- Collision
- Actor Overview – More on working with Actors, adding actors to a map and setting properties.

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