All;
Playing with the photoworks studio, I have always had the same issue complained about here by others:
The floor when set to an offset of 0, is not touching the parts.
Playing with this further, I found that it has to do with the for lack of a better term, "bounding box" of the parts in the scene. Unfortunately, when you use the default studios, it constantly readjusts your floor offset to 0, so you can't workaround the studios with using a negative floor offset from what I can tell. So, that forces us to go back to using the standard rendering procedure.
Here's what I mean in regard to the bounding box issue:
If I lay a cylindrical object on the top plane of the assemly I intend to render, and give it a floor offset of 0, and the cylinder is perhaps mated tangent, and is free to rotate and translate, if it is oriented such that the corner of the bounding box protrudes through the intended floor, it sets the floor to that lowest point, making things look like they are floating.
This is all pretty unscientific, and not always a "feature" that I can turn off and on at will, but it does behave this way most of the time.
Just some thoughts for discussion...
--cutthroat