Michaeltvs asked how I approach modelling - Do I use a lot of separate shapes, or do I start with one segmented box and twist/taper it into he shape I want?
3D Modelling is one of those things where there are often many ways to do a particular task. Ive been away from this project (and 3D modelling) for a few weeks (unfortunately other things often creep into my life) so my memory of exactly how I do it, may not be perfect. To see my personal approach to modelling, it may be better to browse through older posts.
I tend to start with a primitive shape that matches best to the piece Im trying to build - a plane or box for floors, cylinder for poles etc, and then adjust it to the size/shape I need. As for aligning it. I find the best way to get it exactly where you want it is to go around all of the vertices, and just move them to where they should be, one by one. For example, if one part ends at 6.350m from the origin on a particular axis, the adjoining vertices should be located at the same position - not at 6.355, or some other random point that the whole object "seems" to align at visually, then just weld the aligned vertices together.
As far as alignment goes. as I have said before, there is a mathematical harmony at work. If you use reasonable assumptions and then think like a construction engineer, things just seem to fit together. I have had a few alignment problems at times. Sometimes its as if things move slightly after I have placed them. I put this down to the precision of Gmax/Max not being what I expect it to be. I find I check things periodically when precision counts, and if its not right, I can spend hours tweaking it until it is!
Its hard to explain, but, its its pretty much just math, and having a good idea in your head of the 3D relationships between the parts, and then a lot of tweaking verticies!
To answer the specific question better, each piece is many distinct shapes all joined together. The stairwells for example... They're linked into a single object now, but they started as lots of seperate boxes, with chamfers added, faces removed, and then moved into position and welded together.
The interior and exterior started as boxes but now resemble a collection of planes more than anything else, since the boxes have been joined together and all the backfacing faces have been removed.
Thats not to say that everything needs to be welded into a single object. Its better to keep parts as separate as possible for as long as possible, so that they can be reused or modified, if needed. Of course, theres little point in reusing a box, but a set of stairs, or a chair, can be reused easily, without having to build a new piece. You can "save selected" parts to disk, and build up a parts library, that can be imported into any model! More advanced modellers may even reuse a part by referrence, allowing any changes made to the original piece to be automatically applied to each of the copies! This saves a lot of time with things like seating, where there may be hundreds of copies of the original object!
Once the model is complete, *then* you can save out a "final" copy, which can be joined together to form a single object ready for importing into Trainz!
The Tangara is broken up into several distinct objects. The main ones are the exterior, interior, stairs and upper deck, lower seats, upper seats, and other various small objects such as the drivers console, drivers chair etc. Naturally the doors, bogies and pantograph are separate pieces, as these will need to be exported separately to become attachments.
