How to model complex roads?

Cactus on Fire

What would be the best, non destructive way to model very complex roads and junctions with automatically placed street lamps and sidewalks like the attached image?

Klunk

think train set, ie a set of parts for junctions/merging roads connected together with lofted splines (the splines can be used to place street furniture too, where the parts set would have them built in). If you think of it as lanes it probably only really requires 1 merging part (on multi lanes only the inside lane isn't a continuous loft) or just a few variations depending on merging angle

icegodofhungary

It's all about the grid. You'll create a modular kit with pieces that have one of these properties:

1) Pieces that begin and end on major grid lines.

2) Pieces that begin on a major grid line but end at some arbitrary point to which you can use for vertex snapping instead of grid snapping.

3) Pieces that neither begin or end on the major grid line

3s will only align with 2s via vertex snapping. This will let you handle irregular curves and various transitions to angles. The ultimate goal is to break everything down into these three categories so you can always start and end on the grid. 2s and 3s are transition pieces. Here is a good tutorial that explains the grid and transitioning on/off of it using simple examples.

Even though that tutorial uses a lot of linear pieces that would make your highway look weird, the same principles apply. As Klunk said you can use lofts to create more sweeping and natural-looking curves. You can break those curves down into 2s and 3s so they will line up to the grid. You could also make the entire interchange one big piece in a highway kit. The ends of the junction would line up to major grid points (probably on the 100m scale) so that your highway pieces can snap to them.

The other option is, if this is for a game engine, use spline meshes. You'll model a section of the highway and feed that into your spline mesh tool which will extend the piece into one continuous spline curve. Something like this:

https://www.youtube.com/watch?v=bGekqhnqbog

You can obviously add multiple elements to it so that you get your road/bridge supports and lights. But this does require something other than just a modeling package. If you just want to attack it purely through modeling, then it's all about the grid.

Klunk

you could script it.....

about half way down, the y an x cylinders could be "modded" to be "roads" or the at least the junctions. The problem is how do you "describe" a road junction ?