2011

this represents a huge discontinuity in its blur modulation and the
Z-discontinuity ends up as a discontinuity in the blurred image. To help
remove the resulting artifacts, the parameters (Min. Alpha and Max Radius)
under the Extend label can be set to generate the missing Z information.
To:Use:
Select at which alpha value to start generating the
missing modulation values. Anything opaque is un-
affected up to the Min. Alpha value.
Min Alpha
Increase the radius (in pixels) of the modulation
value generation. Increase this value until the arti-
Max Radius
facts are removed. Note that increasing the Max
Radius value beyond the point where the artifacts
are removed will result in slower processing.
Vectors Blur
Use the Vector Blur tool to specify the length and the width of the blur ellipses.
The blur ellipses are then oriented independently for each pixel in the direction
of the vectors of the Forward Vector input image and uniformly scaled by the
length of the vectors. You can also apply an extra constant rotation to all the
blur ellipses.
Using this definition of vector blurs you can blur only in the direction of the
vector field. To do this, set the amount of blur in the perpendicular vector
direction to zero. No matter how much it is scaled, it will always stay null.
Then, use the minimum blur radius control to clamp to a finite value to avoid
sampling aliasing.
NOTE If the ROD of the Forward Vectors image is smaller than the ROD of the
image produced by the Blur tool, the pixels lying at the edge of the Forward
Vectors image are repeated to cover the missing region.
The Vectors blur tool has the following parameters:
About Blurs | 395