Donn wrote:
Nicu, I have not followed any of those links, but this thought jumps to mind: on a layer called "plines" use the line tool and draw all the perspective lines you could need - mark a vanishing point (or 2) anywhere, even off the canvas, and then just draw lines from the points out across the page.
When you have a nice structure of guides (not guides, but normal lines) then make a new layer and use the plines layer below as a trace/sketch guide. Hide/Show plines as you need.
Indeed, this is how would one make *from scratch* a perspective drawing, is not easy but is doable. But the original poster asked for something else: an automatic way to make the transformation with Inkscape from a flat drawing to a perspective one. Kind of like the perspective tool in GIMP. Unfortunately, we don't have this feature (yet), I just linked to other requests for the same thing to show there is interest.