TYPE: COP
TITLE: Velocity Blur COP

This operation blurs an image by using pixel velocity to produce a motion blur
effect. The velocity is read from the velocity plane. Velocity planes can be 
output by surface shaders which export the geometry's velocity attribute.

This operation is implemented in VEX. Right click on the dialog '?' help for 
more help on VEX. 

Parameters
    Quality           - Affects the smoothness of the blur. Higher qualities
                        take more samples per pixel to blur.
    Velocity Scale    - Uniformly scales velocity to change the amount of blur.
    Per Pixel Velocity - If on, the velocity plane is used to determine the blur
                         on a per-pixel basis. If off, a global velocity vector
                         is used.
    Velocity Plane    - The name of the velocity plane.
    Accurate Velocity Lookups - If on, the velocity is "followed" by sampling
				the velocity at each point, resulting
				potentially curved blur streaks. If off, only
				the initial velocity is used and the blur
				streaks are straight.
    Velocity Vector   - If Per Pixel Velocity if off, this is the global 
                        velocity vector that is used to produce a streaking 
                        blur.
    Start Blur Scale  - The start blur factor. The first blurred pixel is
                        multiplied by this value.
    End Blur Scale    - The end blur factor. The last blurred pixel is
                        multiplied by this value.
    Blur Dropoff      - The interpolation function for pixel samples in
                        between the start and end pixels.
    Filtering         - The pixel sampling filter.
	None          - Quick, low quality filter.
	Bilinear      - Medium quality filter.
	Full Filtered - Slow, high quality filter.

    Correct for Image Aspect - If on, the blur is adjusted so it appears
			       circular if the image aspect ratio isn't square.
    Outside Bounds    - Specifies the sampling method for pixels outside the
                        image.

Mask & Plane Scope, Frame Scope page:
    Overview - See extra help (Middle click on the dialog '?' help).

Local Variables:
    L   - Sequence length
    S   - Start of sequence
    E   - End of sequence
    IL  - Input sequence length
    SR  - Sequence frame rate
    NP  - Number of planes in sequence
    W,H - Width and height of image
    I   - Image index (0 at start frame)
    IT  - Image time (0 at start frame)
    AI  - Current plane array index
    PI  - Current plane index
    PC  - Num of channels in current plane
