I knocking these into shape some more, so they can be usable units that I can stand looking at for long periods. I have most of the boxcar pack sorted, and these are the main hold-up at the moment.
After a bit more research I've managed to make them both more accurate
and more compact. The latter will be handy for in-game behaviour, even though the difference is not a huge amount, since these units really are pushing the limits.
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As part of this I've replaced the PopTop truck skinning with a proper Barber S2. The end (70 ton) trucks have 33" wheels and a 68" wheelbase, and the middle (125 ton) truck have 38" wheels and a 72" wheelbase, which is what articulated well cars use IRL. Not that you'll notice most of the time, but it was just as easy as making them all the same and I like throwing in details like this.
I'm setting the skin up so that it will be possible to do a range of container combinations without major changes. Obviously it will only be 40 ft, or 2 x 20 ft, on the bottom. The top ones will be able to be meshed and skinned at either 40, 45, 48 or 53 ft. Due to space limitations on the texture there will only be options for two different-coloured containers. IOW, I'll be able to have a blue one up top and a white one down the bottom, or the other way around, in either well car, but won't be able to have a blue one and a white one and a red one and a green one all in a double-car unit. That just won't fit on the texture at a decent resolution, so it aint happening.
Edit: Basic trial of the skinning concept. Seems to work ok. Taking this one as an example, you could have all blue ones, or all grey ones, or three blue and one grey, or the other way around, or any combination of pairs that you like, all on the same skin and all usable in 40 ft top or bottom, and 45, 48 or 53 on top. This should be enough variety to keep us amused.
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The only caveats are:
1/if you want to use 45 or 48 on top, the texture has to be specifically set up for them. A 40 just crops the ends off anything longer, since the central 40 feet are the same anyway, but the ends have to be set for any longer containers. This texture is set up with two 53's - one blue and one grey. Having a 45 and 53 up top would be possible, but if you wanted them the same colour that would mean all containers would have to be the same colour, because there are only two to play with on the texture and you'd be using both to get the different ends of each longer container.
2/ Obviously any generic cars will all have the same colour scheme regardless of what cargo they carry. Getting different ones for different cargoes is easy enough if anyone ever wants to do it, but since it's more work for me and more code for the game to run I won't bother for now.