Prop tractor beam
Excursion funnels are a puzzle element of Portal 2 that work like tractor beams. Objects (like turrets and cubes) and players that touch blue funnels slowly drift away from their emitters, unaffected by gravity. Players can move and grab objects out of them, but can not move against them.
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, with a player clip in front as well as a light for a soft blue glow (with an approximate brightness of 50 120 250 50).
Changing Direction
To alter the direction of an excursion funnel, invert the LinearForce keyvalue of its prop_tractor_beam. The input SetLinearForce can be used.
Example
Example map (includes both vmf and bsp)