another thing that happens, is that when i start to imagine how something is going to go, but i am nowhere near my tools or materials, my imagination starts to feed me processes and techniques ("i'll do it this way, and then like this...")...i can practically feel my mind extending like a knife into my imaginary material and cutting it.
sculptors say they imagine their artifact in the block, and then chip away the parts that don't belong...this feels the same...