Yes, you’ll need 3D glasses for a projector, the same as you would in a movie theater. These glasses basically function to direct the alternating images on the screen to the correct eye, creating the 3D effect that you see.   3D glasses come in two forms: passive and active. Passive 3D glasses use polarized lenses to filter the projector’s light. They’re typically more affordable than active glasses, but can’t be used right out of the box with frame sequential 3D formats unless you have a polarizing module to convert the images. This is included with some projectors but often needs to be purchased separately, and can be pricey.   Active glasses have lenses that change opacity to filter images based on information received through an embedded sensor. They’re more expensive per pair but will work out of the box with all 3D formats, including frame sequential.