The Motion Vector channel outputs a color channel that represents object movement in the scene. Red/Green values in the map indicate amount of motion in camera screen space. This channel can be used by certain post-production plug-ins to calculate a 2D motion blur which in many cases is sufficient for a motion blur effect.
Please note that using the motion vector channel in post-production has some limitations compared with Maxwell's true 3D motion blur, which are inherent to the a motion vector channel. Some of the limitations are:
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