Sets the amount and direction for motion blur for this panel and all its children.
The top-level panel will get its own composition layer, which is slower, but required for correct visuals. The default is that all motion blur is disabled. For the effect to be enabled, all three properties (velocity, direction, and sample count) need valid values (positive value for velocity; sample count greater than 1; non-zero direction vector for direction).
Velocity controls the 'length of the tail', with larger values resulting in the blur extending for longer. Direction is a unit vector that controls the direction to blur in.
Sample count is a number between 2 and 8 that controls how many points will be sampled along the blur trail. Larger numbers result in smoother-looking blurs at the cost of performance in the shader.

Examples:
motion-blur: velocity( 2.0 ), direction( 0.0, -1.0 ), samples( 6 );