Definitions

boundary: The outline of an object.

concave: When a boundary curves inward anywhere along the perimeter.

convex: When a boundary curves outward along the perimeter.

cusp: A point on a boundary where a point reverses direction. (i.e. corner)

collinear: Points lying on the same continuous, linear line.

coincide: To occur at the same time. A point of intersection.

rigid: A movement where the translated image maintains size of the orginal object.

planar: Moving along a constant plane in 3dimensional space

lateral: A surface that is on a side of an object.

line: A continous collection of points extending in two opposite directions.

minima: A point of concavity along a boundary.

negative minima: Silhouettes of actual minima.

projections: A linear transformation.