| 释义 |
projective space Real (or complex) n-dimensional projective space can be considered as Rn (or ℂn) together with points at infinity (specifically, a hyperplane at infinity). In terms of homogeneous coordinates, points [1:x1:…:xn] can be identified with Rn and the hyperplane has equation x0 = 0. From the point of view of affine geometry, these points at infinity will remain at infinity; from the projective view, the points at infinity are no different from other points, and the hyperplane at infinity need not be invariant under a projective transformation. Topologically, the real projective line is the circle, and the complex projective line is the Riemann sphere.
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