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1. Geometry
a. the complete boundary of a solid figure
b. a continuous two-dimensional configuration
a. the uppermost level of the land or sea
b. (as modifier): surface transportation



a fundamental geometric concept with different meanings in different branches of geometry.

(1) A high-school geometry course considers planes, polyhedrons, and some curved surfaces. Each of the curved surfaces is defined in a special way— most often as a set of points that satisfy certain conditions. For example, the surface of a sphere is the set of points at a specified distance from a given point. The concept of a surface is merely exemplified rather than defined. Thus, a surface is said to be the boundary of a solid or the trace of a moving curve.

(2) The mathematically rigorous definition of a surface is based on the concepts of topology. The principal concept here is that of a simple surface, which may be represented as a part of a plane that is subject to continuous deformation— that is, to continuous extension, compression, or bending. More precisely, a simple surface is the image of the interior of a square under a homeomorphic, that is, a one-to-one and bicontinuous, mapping. This definition can be expressed analytically as follows. Introduce Cartesian coordinates u, v in the plane and x, y, z in space. Let S be the (open) square whose points have coordinates satisfying the inequalities 0 < u < 1 and 0 < v < 1. A simple surface is the homeomorphic image in space of the square Sʹ. The surface is given by means of formulas x = Φ (u, v), y = ψ(u, v), z = x(u, v), which are called its parametric equations. For different points (u, v) and (u ʹ, vʹ) the corresponding points (x, y, z) and (xʹ, yʹ, zʹ) must be different, and the functions Φ(u, v), ψ(u, v), and x(u, v) must be continuous. The hemisphere is an example of a simple surface. The sphere, however, is not a simple surface. Further generalization of the concept of a surface is consequently necessary. If a neighborhood of each point of a surface is a simple surface, the surface is said to be regular. From the standpoint of topological structure, surfaces as twodimensional manifolds are divided into several types, such as closed and open surfaces and orientable and nonorientable surfaces.

The surfaces investigated in differential geometry usually obey conditions associated with the possibility of using the methods of the differential calculus. These are usually smoothness conditions, such as the existence of a tangent plane or of curvature at each point of the surface. These requirements mean that the functions Φ(u, v), ψ(u, v), and x (u, v) are assumed to be once, twice, three times, or, in some problems, infinitely differentiable or even analytic. Moreover, it is required that at each point at least one of the determinants

be nonzero.

In analytic and algebraic geometry, a surface is defined as a set of points whose coordinates satisfy an equation of the form

(*) Φ(x, y, z) = 0

Thus, a given surface may or may not have a graphic geometric image. In this case, in order to preserve generality, we speak of imaginary surfaces. For example, the equation

X2 + y2 + z2 + 1 = 0

defines an imaginary sphere, although real space contains no point with coordinates satisfying this equation. If the function Φ(x, y, z) is continuous at some point and has at this point continuous partial derivatives ∂Φ/ ∂x, ∂Φ/ ∂y, ∂Φ/∂z, at least one of which does not vanish, then in the neighborhood of this point the surface defined by equation (*) will be a regular surface.


The outer part (skin with a thickness of zero) of a body; can apply to structures, to micrometer-sized particles, or to extended-surface zeolites.
A subset of three-space consisting of those points whose cartesian coordinates x, y, and z satisfy equations of the form x = ƒ(u, v), y = g (u, v), z = h (u, v), where ƒ, g, and h are differentiable real-valued functions of two parameters u and v which take real values and vary freely in some domain.


(1) (Surface) Microsoft's hardware brand. See Surface versions.

(2) In CAD, the external geometry of an object. Surfaces are generally required for NC (numerical control) modeling rather than wireframe or solids.
References in periodicals archive ?
The analysis of three-dimensional facial surfaces via Differential Geometry is adopted to extract landmarks.
Positioning of the crowns with the flattened facial surface parallel to the vertical stem of the surveyor with pink wax number 7 (Figure 2).
We extensively examined the prior literature on 3D lace recognition, which can be categorized into methods using point cloud representations, depth images, facial surface features or spherical representations [2].
The real challenge, until today, has been the ability to easily obtain accurate 3-D images of the facial surface, accurately measure these images, and assess the changes that occur after treatment.
Using only the chosen colours--quite a discipline in itself--Cazalet often employed quite strong geometrical shapes to highlight the facial surfaces and features, making a reference to theatrical make-up and the emphasis this can give to both facial and inner characteristics.
The color was recorded using the Vita Classical shade guide, and the shade A2 and A3 was considered as the initial color the tooth preparation involved a minimal chamfer in the facial surfaces.
According to the study, by the way, you want to brush&nbsp;in a circular motion, use a 45-degree angle while brushing facial surfaces of teeth and position your arm correctly (theses were some of the criteria for the "tooth-brushing skill" metric).
These 3D data sets showed individual brain regions, as well as accurate and detailed facial surfaces, from which Hammond and research assistant and co-author Michael Suttie performed shape analyses.
Gingivitis image analysis utilizes a high-resolution camera for image capture and focuses on the facial surfaces of the 12 anterior teeth.
We can best understand Tommo's anxiety about having his face tattooed, Otter suggests, if we set it in the context of the invidiously comparative mappings of facial surfaces in the linked disciplines of phrenology and racial ethnology.