Unless your local cinema got a good deal on a projector from a 1980s theme park 3D movie, it’s definitely using circularly polarised filters. If you’ve tried tests like putting the lenses from two pairs of the glasses or one pair of the glasses and one pair of regular polaroid sunglasses next to each other and rotating them, that’ll still make them get brighter and dimmer like with linear polarised filters, as passing through the filter can change the polarisation to elliptical, and that means it’ll be affected by rotation when it gets to the second filter.
Unless your local cinema got a good deal on a projector from a 1980s theme park 3D movie, it’s definitely using circularly polarised filters. If you’ve tried tests like putting the lenses from two pairs of the glasses or one pair of the glasses and one pair of regular polaroid sunglasses next to each other and rotating them, that’ll still make them get brighter and dimmer like with linear polarised filters, as passing through the filter can change the polarisation to elliptical, and that means it’ll be affected by rotation when it gets to the second filter.