Func areaportal

(An unrelated entity, sometimes referred to as a "world portal")

It creates an. When the portal is open, it de-renders objects in the area across from the viewer which aren't visible through the opening. When the portal is closed it cannot be seen through at all.

These are not really brush entities. They are brush entities from a mapper/Hammer perspective, but by the time they reach the game, the brush is gone and this is, in effect, a point entity.

The entity's brush must be textured with  (seen on the left) for it to function. Areaportals should completely cover the entrance they're meant to work on. Areaportals must not be able to draw a line through visleaves from one side of themselves to another. If there are multiple openings to an area, there needs to be an areaportal over each one, otherwise the engine cannot define the boundaries between areas. If an areaportal can draw a line to itself, it's considered a and generates a pointfile just like a normal one.