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Look up in Wiktionary, the free dictionary. picture plane |

In painting, photography, graphical perspective and descriptive geometry, a **picture plane** is an image plane located between the "eye point" (or * oculus *) and the object being viewed and is usually coextensive to the material surface of the work. It is ordinarily a vertical plane perpendicular to the sightline to the object of interest.

In the technique of graphical perspective the picture plane has several features:

- Given are an eye point O (from
*oculus*), a horizontal plane of reference called the*ground plane*γ and a picture plane π... The line of intersection of π and γ is called the*ground line*and denoted*GR*. ... the orthogonal projection of O upon π is called the*principal vanishing point P*...The line through*P*parallel to the ground line is called the*horizon*HZ^{ [1] }

The horizon frequently features vanishing points of lines appearing parallel in the foreground.

The orientation of the picture plane is always perpendicular of the axis that comes straight out of your eyes. For example, if you are looking to a building that is in front of you and your eyesight is entirely horizontal then the picture plane is perpendicular to the ground and to the axis of your sight.

If you are looking up or down, then the picture plane remains perpendicular to your sight and it changes the 90 degrees angle compared to the ground. When this happens a third vanishing point will appear in most cases depending on what you are seeing (or drawing).

G. B. Halsted included the picture plane in his book *Synthetic Projective Geometry*: "To ‘project’ from a fixed point *M* (the ‘projection vertex’) a figure, the ‘original’, composed of points *B, C, D* etc. and straights *b, c, d* etc., is to construct the ‘projecting straights’ and the ‘projecting planes’ Thus is obtained a new figure composed of straights and planes, all on M, and called an ‘eject’ of the original."

"To ‘cut’ by a fixed plane μ (the picture-plane) a figure, the ‘subject’ made up of planes β, γ, δ, etc., and straights *b, c, d*, etc., is to construct the meets and passes Thus is obtained a new figure composed of straights and points, all on μ, and called a ‘cut’ of the subject. If the subject is an eject of an original, the cut of the subject is an ‘image’ of the original.^{ [2] }

A well-known phrase has accompanied many discussions of painting during the period of modernism.^{ [3] } Coined by the influential art critic Clement Greenberg in his essay called "Modernist Painting", the phrase *"integrity of the picture plane"* has come to denote how the flat surface of the physical painting functions in older as opposed to more recent works. That phrase is found in the following sentence in his essay:

*"The Old Masters had sensed that it was necessary to preserve what is called the integrity of the picture plane: that is, to signify the enduring presence of flatness underneath and above the most vivid illusion of three-dimensional space."*

Greenberg seems to be referring to the way painting relates to the picture plane in both the modern period and the "Old Master" period.^{ [4] }

The **horizon** is the apparent line that separates earth from sky, the line that divides all viewing directions based on whether it intersects the Earth's surface or not. The *true horizon* is actually a theoretical line, which can only be observed when it lies on the sea surface. At many locations, this line is obscured by land, trees, buildings, mountains, etc., and the resulting intersection of earth and sky is called the *visible horizon*. When looking at a sea from a shore, the part of the sea closest to the horizon is called the **offing**.

In geometry, a **geodesic** is commonly a curve representing in some sense the shortest path (arc) between two points in a surface, or more generally in a Riemannian manifold. The term also has meaning in any differentiable manifold with a connection. It is a generalization of the notion of a "straight line" to a more general setting.

An **ellipsoid** is a surface that may be obtained from a sphere by deforming it by means of directional scalings, or more generally, of an affine transformation.

In theoretical physics, a **chiral anomaly** is the anomalous nonconservation of a chiral current. In everyday terms, it is equivalent to a sealed box that contained equal numbers of left and right-handed bolts, but when opened was found to have more left than right, or vice versa.

A **3D projection** is a design technique used to display a three-dimensional (3D) object on a two-dimensional (2D) surface. These projections rely on visual perspective and aspect analysis to project a complex object for viewing capability on a simpler plane. This concept of extending 2D geometry to 3D was mastered by Heron of Alexandria in the first century. Heron could be called the father of 3D. 3D Projection is the basis of the concept for Computer Graphics simulating fluid flows to imitate realistic effects. Lucas Films 'ILM group is credited with introducing the concept.

In mathematics, the **linking number** is a numerical invariant that describes the linking of two closed curves in three-dimensional space. Intuitively, the linking number represents the number of times that each curve winds around the other. The linking number is always an integer, but may be positive or negative depending on the orientation of the two curves.

A **vanishing point** is a point on the image plane of a perspective drawing where the two-dimensional perspective projections of mutually parallel lines in three-dimensional space appear to converge. When the set of parallel lines is perpendicular to a picture plane, the construction is known as one-point perspective, and their vanishing point corresponds to the oculus, or "eye point", from which the image should be viewed for correct perspective geometry. Traditional linear drawings use objects with one to three sets of parallels, defining one to three vanishing points.

**Directional statistics** is the subdiscipline of statistics that deals with directions, axes or rotations in **R**^{n}. More generally, directional statistics deals with observations on compact Riemannian manifolds.

In mathematics, the **Poincaré metric**, named after Henri Poincaré, is the metric tensor describing a two-dimensional surface of constant negative curvature. It is the natural metric commonly used in a variety of calculations in hyperbolic geometry or Riemann surfaces.

In quantum field theory, a **fermionic field** is a quantum field whose quanta are fermions; that is, they obey Fermi–Dirac statistics. Fermionic fields obey canonical anticommutation relations rather than the canonical commutation relations of bosonic fields.

In physics, **Fujikawa's method** is a way of deriving the chiral anomaly in quantum field theory. It uses the correspondence between functional determinants and the partition function, effectively making use of the Atiyah–Singer index theorem.

In geometry, a **pencil** is a family of geometric objects with a common property, for example the set of lines that pass through a given point in a plane, or the set of circles that pass through two given points in a plane.

**Plasma parameters** define various characteristics of a plasma, an electrically conductive collection of charged particles that responds *collectively* to electromagnetic forces. Plasma typically takes the form of neutral gas-like clouds or charged ion beams, but may also include dust and grains. The behaviour of such particle systems can be studied statistically.

The **Newman–Penrose** (**NP**) **formalism** is a set of notation developed by Ezra T. Newman and Roger Penrose for general relativity (GR). Their notation is an effort to treat general relativity in terms of spinor notation, which introduces complex forms of the usual variables used in GR. The NP formalism is itself a special case of the tetrad formalism, where the tensors of the theory are projected onto a complete vector basis at each point in spacetime. Usually this vector basis is chosen to reflect some symmetry of the spacetime, leading to simplified expressions for physical observables. In the case of the NP formalism, the vector basis chosen is a null tetrad: a set of four null vectors—two real, and a complex-conjugate pair. The two real members asymptotically point radially inward and radially outward, and the formalism is well adapted to treatment of the propagation of radiation in curved spacetime. The Weyl scalars, derived from the Weyl tensor, are often used. In particular, it can be shown that one of these scalars— in the appropriate frame—encodes the outgoing gravitational radiation of an asymptotically flat system.

In mathematics, the **Schur orthogonality relations**, which were proven by Issai Schur through Schur's lemma, express a central fact about representations of finite groups. They admit a generalization to the case of compact groups in general, and in particular compact Lie groups, such as the rotation group SO(3).

In probability theory and directional statistics, a **wrapped normal distribution** is a wrapped probability distribution that results from the "wrapping" of the normal distribution around the unit circle. It finds application in the theory of Brownian motion and is a solution to the heat equation for periodic boundary conditions. It is closely approximated by the von Mises distribution, which, due to its mathematical simplicity and tractability, is the most commonly used distribution in directional statistics.

In probability theory, the family of **complex normal distributions** characterizes complex random variables whose real and imaginary parts are jointly normal. The complex normal family has three parameters: *location* parameter *μ*, *covariance* matrix , and the *relation* matrix . The **standard complex normal** is the univariate distribution with , , and .

In probability theory and directional statistics, a **wrapped Cauchy distribution** is a wrapped probability distribution that results from the "wrapping" of the Cauchy distribution around the unit circle. The Cauchy distribution is sometimes known as a Lorentzian distribution, and the wrapped Cauchy distribution may sometimes be referred to as a wrapped Lorentzian distribution.

In mathematics, the **Beltrami equation**, named after Eugenio Beltrami, is the partial differential equation

In complex analysis, the **Schwarz triangle function** or **Schwarz s-function** is a function that conformally maps the upper half plane to a triangle in the upper half plane having lines or circular arcs for edges. Let *πα*, *πβ*, and *πγ* be the interior angles at the vertices of the triangle. If any of *α, β*, and *γ* are greater than zero, then the Schwarz triangle function can be given in terms of hypergeometric functions as:

- ↑ Kirsti Andersen (2007)
*Geometry of an Art*, p. xxix, Springer, ISBN 0-387-25961-9 - ↑ G. B. Halsted (1906)
*Synthetic Projective Geometry*, page 10*This article incorporates text from this source, which is in the public domain.* - ↑ The case against wall fodder, by Alec Clayton
- ↑ Clement Greenberg, "Modernist Painting"

- James C. Morehead Jr. (1911) Perspective and Projective Geometries: A Comparison from Rice University.

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