## The AIM@SHAPE Glossary

### Alphabetical list of terms

- facial animation
- Methods for animating the face of a Virtual Human. Facial animation is usually performed with Skin Interpolation.
- fairing
- Before computers the smooth curves describing the hulls of ships were faired by using an elastic thin wood ruler, the spline. Today the word fairing relates to designing and editing smooth curves and surface within CAD-type systems.
- fea
- See Finite Element Analysis.
- feature
- Very general term indicating any characteristic of a phenomenon or of an object, for example a surface patch of certain curvature characteristics. In CAD, it refers to a set of geometric elements with a special meaning and controllable by means of a limited number of significant parameters. The meaning depends on the context: for example, it can be related to functionality, geometry, assembly and manufacturing.
- fe element
- Each parts in which the geometry is subdivided by a finite element mesh. For 2D analysis, or a 3D thin shell analysis, the elements are essentially 2D. For a 3D solid analysis, the elements have physical thickness in all three dimensions. (examples: solid linear brick , solid parabolic tetrahedral elements?).
- fem
- See Finite Element Method.
- fillet
- Surface joining and smoothing two other surfaces, defined as the envelop of spheres rolling along the intersection curve of these two surfaces.
- finite element analysis
- Analysis performed with FE methods.
- finite element method
- Numerical method able to solve a wide variety of mechanical problems (e.g. structural, mechanical, heat transfer, fluid dynamics) through the discretization of the model in the 3D space.
- flexion
- Rotation of the limb which is influenced by the joint and causes the motion of all limbs linked to this joint. This flexion is carried out relative to the joint point and a flexion axis has to be defined.
- focal surface
- The focal surface is formed by the centres of curvature of a given smooth surface. Thus, the focal surface consists of two sheets corresponding to the maximal and minimal principal curvatures.
- form feature
- In CAD, it is a geometric feature composed by parts of analytic surfaces (planes, cylinders and spheres).
- forward dynamics
- In forward dynamics, a skeletal motion is determined from input torques and forces.
- forward kinematics
- In forward kinematics, a skeletal posture is determined by assigning input joint angles individually for all the joints of a chain.
- fractal
- An object that exhibits self-similarity: the same form on all scales. A typical example is a snowflake. The boundary of the fractal object has a fractal (non-integer) dimension.
- free-form feature
- In CAD, it is a geometric feature composed by free-form surfaces.
- free-form surface
- Any 2 or 3 dimension shape that is not easily decomposable in regular, or analytic shapes.
- fusion
- The combination of data from different sources.

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