Prop tractor beam
Excursion funnels are a puzzle element of Portal 2 that work like a tractor beams. Objects (like turrets and cubes) and players that touch blue funnels slowly drift away from their emitters, unaffected by gravity. Players can remove objects and themselves from the funnel but can not move against the flow.
Some funnels are connected to buttons. When activated, these funnels reverse direction and turn orange, drawing things towards their emitter instead of pushing things away.
Like bridges, walls, and lasers, funnels can be extended through portals.
Creation
Each funnel consists of a prop_tractor_beam and a player clip in front. Funnels often have a light in front of them for a soft blue glow (with an approximate brightness of 50 120 250 50) but not when the beam is reversible because it conflicts with the orange colour of the funnel.
Changing Direction
To alter the direction of an excursion funnel, set the LinearForce keyvalue of its prop_tractor_beam to a negative number. Two standard values used in Portal 2 for forwards and backwards flow are 250 and -250, respectively. The input SetLinearForce can be used to change the value of LinearForce in-game (for instace, to reverse the flow when a button is pressed).
See also
External links
- Example map using this tutorial. VMF included.