i understand you are rotating around on all 3 axis, where as my program is straight foward the whole way, however, it is the same theory of drawing a 3d theme, just your algorithms for calculating the corner positions changes, even in mine the lines are not straight (as illustrated), they angle the way they need to as they progress along the object.. although come to think of it, im not sure if textured lines will rotate the image for you.. will just use the next pixel along if the line moves across that way...

But i say don't give up on GDI+ go all the way.