In Corel Painter, you can interleave shapes with layers in the Layers panel, which can affect how your document is printed. Shapes are vector objects, as opposed to pixel-based objects, which makes them resolution-independent. Corel Painter attempts to preserve shapes as vector paths in order to print at the full native resolution of PostScript printers.
Any object in a lower position in the Layers list "touched" by a rasterized shape must also be rasterized to preserve the effect. For example, if you have a shape with transparency on top of a number of other shapes, all shapes below it must be rasterized to preserve the transparency on the canvas even if the overlap area is small. Similarly, if part of an image from a layer is placed over a shape, the shape must be rasterized to be correctly printed.
If you want to print shapes at the full resolution of your printer, ensure that the shapes are not transparent, that their composite method is set to Default, and that they are not under any other transparent layers or objects.