Variables
In order for the expression to refer to a pixel in the
original image, a few variables are set:
- xy (xy:2)
- The cartesian coordinates of the pixel.
- x (nil:1)
- The first component of the cartesian coordinates of the pixel.
- y (nil:1)
- The second component of the cartesian coordinates of the pixel.
- ra (ra:2)
- The polar coordinates of the pixel.
- r (nil:1)
- The first component of the polar coordinates of the pixel
(0 <= r < 2*pi).
- a (nil:1)
- The second component of the polar coordinates of the pixel
(the distance from the center).
To make it easier to write expressions which depend on the
image size, a few additional variables are set:
- WH (xy:2)
- The size of the image.
- W (nil:1)
- The width of the image.
- H (nil:1)
- The height of the image.
- R (nil:1)
- The biggest possible value for r for the image.
- XY (xy:2)
- The biggest possible value (in both components) for
xy.
- X (nil:1)
- The biggest possible value for x for the image.
- Y (nil:1)
- The biggest possible value for y for the image.
For the purpose of animations two additional variable are set:
- t (nil:1)
- The time which is 0 <= t < 1. If animation
is disabled, the value of t can be chosen in the
Settings tab. If you want to make animations loop, set the
'Periodic' check-box in the Settings tab and make sure that the
images at t == 0 and t == 1 are the same.
- frame (nil:1)
- The number of the current frame, beginning with 0
for the first frame.