Perspective mapping takes the world space coordinates and divides the X and Y coordinates by the Z coordinate (Figure 1). This is a useful way to model a projector (i.e., by using a texture with this projection as the distribution, with black border mode). You can also use it for camera mapping.
The same change as the other projections applies here: 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.
Figure 1: The Perspective projection node orienting a Checks texture
This projection takes the world space coordinates and divides the X and Y coordinates by the Z coordinate. This is useful if you want to model a projector (i.e., use a texture with this projection as the distribution, with black border mode). It is also useful for camera mapping. The image is mapped to (-1, -1) – (1, 1), so by default, an offset is not necessary to use this mapping for projectors or camera mapping.
Figure 2: Perspective projection applied to a box, cylinder, and sphere