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  2. Projective geometry - Wikipedia

    en.wikipedia.org/wiki/Projective_geometry

    The only projective geometry of dimension 0 is a single point. A projective geometry of dimension 1 consists of a single line containing at least 3 points. The geometric construction of arithmetic operations cannot be performed in either of these cases. For dimension 2, there is a rich structure in virtue of the absence of Desargues' Theorem.

  3. Desargues's theorem - Wikipedia

    en.wikipedia.org/wiki/Desargues's_theorem

    In projective geometry, Desargues's theorem, named after Girard Desargues, states: Two triangles are in perspective axially if and only if they are in perspective centrally. Denote the three vertices of one triangle by a, b and c, and those of the other by A, B and C. Axial perspectivity means that lines ab and AB meet in a point, lines ac and ...

  4. Duality (projective geometry) - Wikipedia

    en.wikipedia.org/wiki/Duality_(projective_geometry)

    In projective geometry, duality or plane duality is a formalization of the striking symmetry of the roles played by points and lines in the definitions and theorems of projective planes. There are two approaches to the subject of duality, one through language (§ Principle of duality) and the other a more functional approach through special ...

  5. Real projective plane - Wikipedia

    en.wikipedia.org/wiki/Real_projective_plane

    In mathematics, the real projective plane, denoted ⁠ ⁠ or ⁠ ⁠, is a two-dimensional projective space, similar to the familiar Euclidean plane in many respects but without the concepts of distance, circles, angle measure, or parallelism. It is the setting for planar projective geometry, in which the relationships between objects are not ...

  6. Projective plane - Wikipedia

    en.wikipedia.org/wiki/Projective_plane

    The projective plane over K, denoted PG(2, K) or KP 2, has a set of points consisting of all the 1-dimensional subspaces in K 3. A subset L of the points of PG(2, K) is a line in PG(2, K) if there exists a 2-dimensional subspace of K 3 whose set of 1-dimensional subspaces is exactly L.

  7. Homogeneous coordinates - Wikipedia

    en.wikipedia.org/wiki/Homogeneous_coordinates

    Rational Bézier curve – polynomial curve defined in homogeneous coordinates (blue) and its projection on plane – rational curve (red) In mathematics, homogeneous coordinates or projective coordinates, introduced by August Ferdinand Möbius in his 1827 work Der barycentrische Calcul, [1] [2] [3] are a system of coordinates used in projective geometry, just as Cartesian coordinates are used ...

  8. Projective space - Wikipedia

    en.wikipedia.org/wiki/Projective_space

    Projective space. In graphical perspective, parallel (horizontal) lines in the plane intersect at a vanishing point (on the horizon). In mathematics, the concept of a projective space originated from the visual effect of perspective, where parallel lines seem to meet at infinity. A projective space may thus be viewed as the extension of a ...

  9. Oriented projective geometry - Wikipedia

    en.wikipedia.org/wiki/Oriented_projective_geometry

    Oriented projective geometry is an oriented version of real projective geometry. Whereas the real projective plane describes the set of all unoriented lines through the origin in R3, the oriented projective plane describes lines with a given orientation. There are applications in computer graphics and computer vision where it is necessary to ...