Perspective projection takes the world space coordinates and divides the X and Y coordinates by the Z coordinate. This can be useful for camera mapping, or creating projectors using an emission's distribution with a black border mode. The image is mapped to (-1, -1) - (1, 1), so by default, offsets are not needed to use this mapping for projectors or camera mapping.
Transform - The transformation applied to the projection. Accepts a Transform node.
Coordinate Space - The coordinate space used by the projection.