Hi Krzystof,
What do we do with it in 0.49? I would really like to see the coordinate system bug fixed in 0.49, even if it means rewriting the 3D box from scratch, or even disabling it. Fancy features aren't very useful if we don't get the basics right.
I agree with you there. I wrote the 3D box tool for GSoC '07 but there are a number of things that have bugged me about it ever since - some of them related to its internal structure and some to its user experience. One of the main difficulties is that Inkscape is essentially a 2D application, which makes it non-trivial to fit a 3D tool to it that behaves intuitively even though it cannot rely on 'true' 3D information internally. In the original project description advertised by the Inkscape devs before GSoC the tool was even envisaged to work on a purely 'geometrical' basis (i.e., by just relying on information about the location of the vanishing points and the corners of a box on canvas, much like a design draftsman would do when sketching things on a piece of paper). This works ok-ish for a single box but it can get you only so far and results in a really awkward internal structure. Realising this halfway throught GSoC, I essentially rewrote the whole tool from scratch with a much cleaner approach that uses 3D information. Still, due to lack of time and my relative inexperience with some of Inkscape's internals at the time it has not resulted in the powerful and easy-to-use tool that I originally had in mind. I have always planned to give it another rewrite but needed to think about some of the fundamental issues first. Unfortunately, some tragic personal events in my family and other things have kept me from being able to devote the necessary time to it during the past couple of years. But I'm still keen on working on it and should be able to do so soon-ish. To give you a rough idea of the timeframe: I probably can't devote much time to it this month and am away for most of September, but as of October I should be able to work on it regularly (not full-time but steadily).
I have a number of ideas in mind how to give the tool a considerable overhaul. Apart from some internal things I think that in particular the user interface should be polished and extended a lot. I would be more than happy to hear feedback from the community how it could be improved (which I'm sure it can in many ways). I think the time until October could be well used to come up with specific ideas for improvement. I'll try to collect some thoughts from my point of view soon and will send them around in a separate email asking for user feedback (since the tool has been in existence for quite a while people should be able to point out the shortcomings quite specifically).
Anyway, to get back to your original question: don't worry about the 3D box tool keeping you from eliminating the most annoying coordinate inversion bug. I still remember the countless times it drove me nuts during my own work (in particular for the 3D box tool) and would be more than happy to help in any way I can to fix it. So just let any bugs in the 3D box tool that result from fixing it flow my way and I'll work on them as soon as I can (as I said, October at the latest).
Cheers, Max