## The AIM@SHAPE Glossary

### Alphabetical list of terms

- cad
- See Computer Aided Design.
- calibration
- Measuring the parameters appearing in the equations ruling the acquisition process of an acquisition device.
- camera
- A lightproof box fitted with a lens though which the image of an object is recorded on a material sensitive to light.
- cas
- See Computer Aided Styling.
- case based reasoning (cbr)
- The process of solving new problems based on the solutions of similar past problems. CBR starts with a set of cases or training examples; it forms generalizations of these examples, albeit implicit ones, by identifying commonalities between a retrieved case and the target problem.
- catchment basin
- The catchment basin of a minimum m on a surface described by a C2-differentiable function defined over a domain D in R2 is the locus of the points in D which are closer to m than to any other minimum according to the topographic distance.
- catmull-clark scheme
- A subdivision scheme for quad meshes generalizing the bivariate cubic spline.
- cbr
- See Case Based Reasoning.
- center-line
- See center-line skeleton.
- center-line skeleton
- The concept of center-line is strictly related to that of skeleton. Complex objects can be seen as the arrangement of tubular-like components, and abstracted to a collection of center-lines which split and join, following the object topology, and which form, actually, a skeleton. A center-line should satisfy the following requirements: centricity, connectivity and singularity.
- cfd
- See Computational Fluid Dynamics.
- characteristic map
- An 1-1 local map between the subdivision surface around an extraordinary vertex and the tangent plane at that vertex. The existence of the characteristic map guarantees C1 continuity of the subdivision surface at that vertex.
- character line
- Basic drawing lines needed to define or characterize an object in the styling phase. They are used to give specific impression/feeling when looking at the object (e.g. the object appears sweet/aggressive), or to define a common peculiar aspect among set of products, as a signature of the designer (e.g. Pininfarina vs. Giugiaro) or the construction company (e.g. Alfa Romeo vs. Peugeot). Most of the character lines are virtual (i.e. only perceived) lines, such as light or curvature lines.
- clay modelling
- Modelling with clay to produce (scaled or full size) physical models of a product for evaluation purposes. Different material can be used to create the physical prototypes, but clay is especially used in the automotive industry.
- clustering
- A process of dividing elements in a dataset into subgroups, by determining which of these elements are similar.
- colour mapping
- A colour-coded map is an application which associates to a scalar function value a specific colour by using a colour table.
- compression
- Compression aims at storing a data set in a more compact way than the original data file. Two main approaches for data compression exist:
- Reversible compression, where different packing and re-indexing techniques are use to represent the data with the fewest possible number of bytes without loosing information.
- Non-reversible compression, techniques where information is lost and tolerances and other parameters describe which information is allowed to be lost.

Which compression techniques to use depend to a large extent of the later use of the information. Information that is only to be used for visual purposes often allow for high compression rates as the human eye most often do not detect small errors without a detailed scrutiny of the image. Information to be used in downstream computations can be degraded by compression, as compression algorithms tends to insert false structure in a data set, e.g., thinning a polyline description of a circle, will make the circle resemble a rough polygon. - computational fluid dynamics
- The numerical simulation of fluid flows, such as the flow of air around a moving car or plane.
- computational mechanics
- Field of mechanics solving specific problems by simulation through numerical methods implemented on digital computers.
- computer aided design (cad)
- 2D or 3D design software package or visualisation able to assist the product development process.
- computer aided styling (cas)
- 3D surface design and evaluation software suitable for an accurate definition of the shape and aesthetics of a product.
- computer tomography scan device
- From the Greek words "to cut or section" (tomos) and "to write" (graphein), it is a method of separating interference from the area of interest by imaging cut sections of the object. Its main application is medicine (see DICOM as standard output shape).
- conceptual design
- Starting phase of the product development in which designers clarify the requirements for a product and define its functions, structure, shape, materials, interfaces, behaviour and appearance.
- concurrent engineering
- Management/operational approach which aims at improving product design, production, operation, and maintenance by developing environments in which personnel from all disciplines (design, marketing, production engineering, process planning, and support) work together and share data throughout all phases of the product life cycle.
- conforming simplicial mesh
- A conforming simplicial mesh is a simplical mesh such that the intersection of any two simplices is either empty or is a simplex belonging to both simplices. A simplicial complex such that any k-simplex with k
- conformity set up
- Set of operators generating a conform model through healing treatments.
- connected component
- Part of an object such that the path between any two point in that part lies within the same part.
- constraint
- In geometric modelling, geometric condition that the model has to respect; for example, it can be a point, tangency or curvature constraint. More generally, any condition that a model has to respect according to some specific application purposes (from geometry, aesthetics, manufacturing, and so on).
- constructive solid geometry
- Geometric representation in which the model is defined as combinations of primitive sets by Boolean operators (union, intersection, subtraction).
- continuous levels-of-detail (lod) model
- Both progressive and variable-resolution LOD model are continuous models. Often, in the literature, the term continuous LOD models is used to indicate only variable- resolution LOD models.
- continuum mechanics
- Branch of computational mechanics studying bodies at the macroscopic level, using continuum models in which the microstructure is homogenized by phenomenological averages.
- contour
- One or a set of curves originated through intersection of a plane with the object.
- contour set
- Intersection curves between the surface and a family of parallel planes.
- contour tree
- The contour tree of a scalar field is the graph obtained by continuous contraction of each contour of (D, h) to a single point. It represents the relations between the connected components of the level sets of a scalar fields. Contour trees are special cases of the Reeb graphs.
- control point
- A point on a curve or surface that influence the shape in a region of the curve or surface. Control points are most frequently used for modelling of Bezier, B-spline and NURBS curves and surfaces, but the concept is not restricted to these. Sometimes control points are on the curve or surface they belong to, often control points are close to the curve or surface, but not close to the surface and influence the shape close to the point.
- control skeleton
- A connected set of segments, corresponding to limbs, and joints, corresponding to articulations.
- convolution surface
- It calculates the field value at P as the integral of the field contributions from each point of the skeleton. This results into smooth, bulge-free, surfaces for skeletons defined as graphs of branching curve and surfaces pieces.
- critical point
- A point p in R2 is a critical point of a C2-differentiable function defined over a domain D in R2 if and only if the gradient of f vanishes at p.
- critical point configuration graph (cpcg)
- It is defined for a Morse function f defined on the closure of a simply-connected open set in R2. It is a graph G in which the nodes represent the critical points of f and two nodes in G are connected by an arc in G if there exists an integral line that emanates from one critical point (node) and reaches the other.
- csg
- See Constructive Solid Geometry.
- ct scan device
- See Computer Tomography Scan Device.
- culling
- A concept from computer graphics used for the methods employed to sort not visible geometry sent to the graphics pipeline to avoid using computational resources on invisible parts of the objects displayed. Culling can both be performed on the CPU and by the graphics card.
- curvature
- Let C be a curve and let P be a point on C. Let N be the normal at P and let O be the point on N which is the limit of where the normal to C at P` intersects N as P` tends to P. O is the centre of curvature at P and PO is the radius of curvature at that point.
- curve-curve intersection
- Points of coincidence of two curves. The points lie on both curves, and thus, it is a way to compute points on a curve.
- curve-surface intersection
- Points of coincidence of a space curve and a surface. The points lie on both, the surface and the space curve, and thus, it is a way to compute points on a surface.

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