Motion Models

Motion models are used to describe the overall movement of a scene between two frames. Using multiple calibrated cameras, we can calculate the 3D structure of the scene and can thus calculate 3D motion models (good for modelling complex movement and significant non-planar depth variation in the scene) which can then be used to perform 3D motion stabilization.

The heart is an object that is perpetually rotating,translating and deforming in 3D space and thus a completely accurate model of the heart’s model would need to be 3D also.

Each 2D model is parameterised and each parameter represents a degree of freedom. As you increase the number of degrees of freedom fewer restrictions govern the extent to which an original item can be warped. Following table shows, as the number of degrees of freedom increases, the number of feature characteristics retained decreases.

Relationship between each 2D motion model

Name # Degrees of Freedom Preserves
translation 2 orientation + …
translation 3 lengths + …
translation 4 angles + …
affine 6 parallelism + …
projective 8 straight lines

Overview of 2D Planar Transformations

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