feTurbulence {gridSVG} | R Documentation |
Create an image using the Perlin turbulence function.
Description
This filter primitive creates an image using the Perlin turbulence
function. It allows the synthesis of artificial textures like clouds
or marble.
Usage
feTurbulence(baseFrequency = 0, numOctaves = 1,
seed = 1, stitchTiles = FALSE,
type = c("turbulence", "fractalNoise"), ...)
Arguments
baseFrequency |
The base frequency (frequencies) parameter(s) for the noise
function. If a two element numeric vector is provided, the first
number represents a base frequency in the X direction and the second
value represents a base frequency in the Y direction. If one number
is provided, then that value is used for both X and Y.
|
numOctaves |
The numOctaves parameter for the noise function.
|
seed |
The starting number for the pseudo random number generator.
|
stitchTiles |
If stitchTiles is FALSE , no attempt it made to
achieve smooth transitions at the border of tiles which contain a
turbulence function. Sometimes the result will show clear
discontinuities at the tile borders.
If stitchTiles is TRUE , then the user agent will
automatically adjust baseFrequency -x and
baseFrequency -y values such that the feTurbulence 's
width and height (i.e., the width and height of the current
subregion) contains an integral number of the Perlin tile width and
height for the first octave. The baseFrequency will be
adjusted up or down depending on which way has the smallest relative
(not absolute) change as follows: Given the frequency, calculate
lowFreq = \lfloor width * frequency \rfloor / width and hiFreq = \lceil
width*frequency \rceil
/width . If
frequency/lowFreq < hiFreq/frequency then use lowFreq , else use
hiFreq . While generating turbulence values, generate lattice
vectors as normal for Perlin Noise, except for those lattice points
that lie on the right or bottom edges of the active area (the size
of the resulting tile). In those cases, copy the lattice vector from
the opposite edge of the active area.
|
type |
Indicates whether the filter primitive should perform a noise or
turbulence function.
|
... |
Further arguments to be passed onto fe .
|
Details
For more information about this primitive, consult the reference to
the SVG specification.
Value
An fe.turbulence
object.
Author(s)
Simon Potter
References
http://www.w3.org/TR/SVG/filters.html#feTurbulenceElement
See Also
filterEffect
, fe
.
[Package
gridSVG version 1.7-4
Index]