Absolute conic: The conic that in a Euclidean coordinate system has equations T=X²+Y²+Z²=0, in homogeneous coordinates. Thus it lies at the plane at infinity.

Absolute quadric: The set of planes tangent to the absolute conic. The homogeneous coordinates of these planes have equation U²+V²+W²=0.

Autocalibration: Literally, obtainment of the extrinsic parameters (positions and orientation) and intrinsic parameters (pixel shape, focal length, principal point) of a set of cameras on the exclusive basis of images taken with them. Equally often it has this more specific meaning.

Homography:  A geometric transformation  that,  in homogenous coordinates, is given  by the multiplication of the coordinate vector of each point by a regular matrix.

Homogeneous coordinates: The homogeneous coordinates of a spatial point of affine coordinates (X,Y,Z) are (X,Y,Z,1) or any non-null proportional vector. In homogeneous coordinates we also have points at infinity, corresponding to the set of lines parallel to a given line. If these lines have direction vector (A,B,C), the associated point has homogeneous coordinates (A,B,C,0). Euclidean homogeneous coordinates are those that result from a Euclidean reference.

Horopter curve: The set of 3D points that project onto two points of identical coordinates in two cameras. It is a cubic curve that intersects the plane at infinity at two points of the absolute conic plus a third point which is the pole with respect to the absolute conic of the line given by the other two.

Absolute line quadric: The set of lines that intersect the absolute conic. In (suitable) Euclidean Plücker coordinates it is given by the equation A1²+A2²+A3²=0.

Plane at infinity: The set of points that, in Euclidean homogeneous coordinates, have equation T=0.

Plücker coordinates: Lines in space (projective 3-space P³) form a 4-dimensional space and can be represented in algebraic geometry by six homogeneous coordinates satisfying a quadratic constraint (i.e., by points in P⁵ that lie on Klein's quadric).

Projective reconstruction: A 3D reconstruction that differs from the original one by a spatial homography.