Apple Shake 4 - Manual (Page 808)

808 Chapter 27 Warping and Morphing Images
Parameters
This node displays the following controls in the Parameters tab:
overSampling
The actual number of samples per pixel equals this number squared. For better
antialiasing, increase the number in the value field.
xExpr, yExpr
The expression for where the pixel information is pulled. Expressions of x and y return
the same image. Expressions of x+5, y+5 pull the color from the pixel five units up and
to the right of the current pixel. You can access the values of the warping image (the
second one) with r, g, b, a, and z.
Here are some example expressions:
“x*r”
“x+((r-.5)*30*r)”
“x+cos(y/140)*70*g”
“x+r*r*cos(x*y/100)*100”
xDelta, yDelta
Sets the maximum distance that any pixel is expected to move, but doesn’t actually
move it. Any given pixel in a displaced image may be affected by any pixel within the
Delta distance. This means it must consider a much greater amount of pixels that may
possibly affect the currently rendered pixel. This is bad. However, if you set a Delta
value that is too small, you get errors if your expression tells the pixel to move beyond
that limit. Therefore, you’ll want to do some testing to balance between speed with
errors, or accuracy with drastically slower renders. Our advice: Start small and increase
the size until the errors disappear.
IDisplace
The IDisplace node is a hard-wired version of DisplaceX intended to warp an image
based on the intensity of a second image. The formula used is x-(a*xScale) and y-
(a*yScale).