kernelUnitLength
The first number is the dx
value. The second number is the
dy
value. If the dy
value is not specified, it
defaults to the same value as dx
. Indicates the intended
distance in current filter units (i.e., units as determined by the
value of parent filter container's primitiveUnits
) for
dx
and dy
, respectively, in the surface normal
calculation formulas. By specifying value(s) for
kernelUnitLength
, the kernel becomes defined in a scalable,
abstract coordinate system. If kernelUnitLength
is not
specified, the dx
and dy
values should represent very
small deltas relative to a given (x,y) position, which might be
implemented in some cases as one pixel in the intermediate image
offscreen bitmap, which is a pixel-based coordinate system, and thus
potentially not scalable.