Perspective effects are created by a perspective projection transformation
Orthographic projection : projects rectilinear box onto display
Objects will not appear to change size with distance
Perspective projection : projects frustum (truncated pyramid) onto display
Near objects appear larger, distant objects appear smaller
Conceptually, a pin-hole camera, located at origin, looking down -Z axis
Camera has a field-of-view - angle representing (horizontal) extent of region viewed
Small angle = narrow field-of-view = telephoto lens
Large angle = wide field-of-view = wide-angle lens