[Inkscape-user] Tiled Clones Trace Question

Hi,

I'm playing around with the Trace option for tiled clones and I'm having a problem.

I'm creating an 8x8 grid of tiled rectangles overtop of a bitmap (I tried this with a gradient filled rectangle underneath as well). Using the trace tab, i can get the clones to be output based on presence, opacity, and size, but I can't seem to get them to be created based on the underlying object's color as is described here: http://tavmjong.free.fr/INKSCAPE/MANUAL/html/Tiles-Trace.html

I've made sure the base object has an unset fill (which the tooltip and article recommend) but I still can't recreate the example in Tavmjong's guide.

Any clues as to what I'm doing wrong?

RQ