is not very clearly worded on which space what coordinates are in,
and when you should try to convert them. A short page describing
coordinate systems in QC and/or Core Image, and what functions
convert between which spaces, would really help, and if I get to
understand it sufficiently, I'll try to write such a page on the wiki.
CI coordinate system is only used with CI filters / kernels as they
work with images, not the 3D space: it uses pixels with the (0,0) is
at the bottom-left corner
Using Image Dimensions, Rendering Destination Dimensions and Math,
you can convert from one to the other if necessary: check this
composition for example:
/Developer/Examples/Quartz Composer/Interface Builder Compositions/
Mouse Tracking.qtz
