## The AIM@SHAPE Glossary

### Alphabetical list of terms

- image
- A 2- or larger dimensional array of measurements. In common usage, images refer to digital recordings of intensities obtained with a camera.
- image segmentation
- A division of an image into a collection of (usually non-overlapping) segments.
- implicit curve/surface
- The set of points P in space verifying an implicit equation (f(P) - constant = 0). f is called the "field function" (and sometimes the "implicit function", which is improper since this function is explicitly given by its parametric equation).
- implicitisation
- A process which consists in the conversion of a parameterised representation of an algebraic curve or surface into an implicit representation.
- implicit lod representation
- It refers to any implicit representation that provides different levels of detail for the implicit surface.
- impostor
- An impostor is an image that represents a part of a complex object, and it is usually generated by capturing a rendered image of this object from the predefined camera position. It is mapped on the polygon that is best suited for the specific camera position.
- indexed data structure
- A data structure for triangle and tetrahedral meshes. For each triangle (tetrahedron) in the mesh, the indices to its three (four) vertices are encoded.
- indexed data structure with adjacencies
- Extension of the indexed data structure for both triangle and tetrahedral meshes. It encodes, for each triangle (tetrahedron) t, also the indices to the three triangles (four tetrahedra) edge-adjacent (face-adjacent) to t.
- index of a critical point
- Number of negative eigenvalues of the Hessian matrix of a C2-differentiable function defined over a domain D in R2.
- individual descriptor
- Human like traits that can be used to describe virtual human characters; these traits can be personality models, emotion, mood, etc. These descriptors are considered to create behavioural animations.
- individuality
- See Individual Descriptor.
- industrial design
- The professional service of creating and developing concepts and specifications that optimise the function, value, and appearance of products and systems for the mutual benefit of both user and manufacturer.
- inflection point
- A point on a curve at which the curvature changes sign, passing from concave to convex or vice versa.
- influence area
- It usually refers to the area affected by applying a geometric operation to a surface (e.g. performing a modification).
- integral line
- An integral line of a function f is a maximal path which is everywhere tangent to the gradient vector field of f. An integral line is emanating from a critical point or from the boundary of D, and it reaches another critical point or the boundary of the domain D.
- inverse dynamics
- It consists in determining the forces and torques required to produce a prescribed motion.
- inverse kinematics
- In inverse kinematics, a skeletal posture is defined by specifying target location to end-effectors. The joint angles of the control skeleton are defined so that the end-effectors reach their targets as close as possible.
- irregular mesh
- A mesh which is not regular.
- irregular vertex
- See extraordinary vertex.
- iso-level
- isoline
- It is a surface curve along which some function defined over the surface has a constant value.
- iterative closest point (icp)
- Class of algorithms for alignment of meshes or point clouds. They are based on the assumption that closest points correspond to each other. Iteratively, for closest points the best transformation is computed and applied to the data set.

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