<Dd> x ′ = f x / z = f d − bz / az </Dd> <Dd> y ′ = f y / z = f c / z </Dd> <P> This is the parametric representation of the image L ′ of the line L with z as the parameter . When z → − ∞ it stops at the point (x ′, y ′) = (− fb / a, 0) on the x ′ axis of the image plane . This is the vanishing point corresponding to all parallel lines with slope − b / a in the plane π . All vanishing points associated with different lines with different slopes belonging to plane π will lie on the x ′ axis, which in this case is the horizon line . </P> <P> 2 . Let A, B, and C be three mutually orthogonal straight lines in space and v ≡ (x, y, f), v ≡ (x, y, f), v ≡ (x, y, f) be the three corresponding vanishing points respectively . If we know the coordinates of one of these points, say v, and the direction of a straight line on the image plane, which passes through a second point, say v, we can compute the coordinates of both v and v </P>

Where is the vanishing point in the image above