Linear Motion

Linear motion includes motion along a world straight line with no restrictions on the velocity, acceleration, etc. In this case, the trajectories of the points will be straight lines. Constraints that hold for matching lines in multiple views can be used on each moving point independently. For example, the trifocal tensor can relate lines in three views. If a world line is imaged as $l^1$, $l^2$, and $l^3$ in three views, they are related by a trilinear constraint [6,7,12].

$$l^1 = (l^2)^{\sc T}{\cal T} l^3$$ (14)

where $\cal T$ is a suitable tensor.