Bridge types & station designs

[Purno]

I'm not sure if it's agreed upon, but I always imagine that route building system someone prototyped a while ago, where you can enter a couple of points and let the game draw the curve in for you (or maybe it didn't do that, can't quite remember). Curvy bridges are then just built around that track.

You mean using splines, like Trainz/TRS?

[XeryusTC]

Take a look here, a spline is basicly a line that follows the best route between a set of points.

[Steve]

I'm not sure exactly what the maths behind it would be, but after setting the points it would make a curve that kinda went around obstacles. That seems like too much work now that I think of it though.. Probably best to make a normal curve and let the user alter it to avoid stuff and reduce cost.
Either way I imagine the track is stored as lots of individual pieces, rather than the 2 pieces (plus anchors for the spline) and working it out every time.

[aarona]

I'm not sure exactly what the maths behind it would be, but after setting the points it would make a curve that kinda went around obstacles. That seems like too much work now that I think of it though..

XeryusTC's explanation wasn't perhaps the best.

Now let me completly confuse you guys...
Lets say you want to make the track go around the corner, then you chose two points (which are only a tile or so away).

If the track were to intersect an object, then we would reject the planners planned track (Error: Object in the way).

<maths>
The curve is simply the one which is C1-continuous (C0 and C1, that is, position and tangential component) and which satisfies the condition that a vehicle would take the least amount of time to pass over this track (cornering speed-restrictions in place, ie to prevent 90 turns).
It turns out there is a solution to this problem, albiet perhaps non-trivial (in the sense that it would be computationally expensive) with hills!

For those playing along at home: For two perpendicular lines the optimal connection solution is a cycloid.
</maths>

Probably best to make a normal curve and let the user alter it to avoid stuff and reduce cost.
Either way I imagine the track is stored as lots of individual pieces, rather than the 2 pieces (plus anchors for the spline) and it works it every time.

Thats the way I had it in mind.
This is a raster solution.
XeryusTC's solution is vector based.

[XeryusTC]

It will probably be best to go for the Theme Park World solution: you place a few dots (or pylons), the game makes a cubic spline through it and the user can alter the heights of the pylons and their rotation. This makes a very powerfull but easy to learn system to make bridges.

Note: maybe we shouldn't use the dots as places for pylons as bridges do have different intervals.
Note2: a cubic spline is a curve that goes through every point in a way as smooth as possible http://www-math.bgsu.edu/~zirbel/la/spline_data.gif

[Steve]

This post gives an in-depth explanation of the system I imagine, with the entire thread being quite interesting.

http://tt-forums.net/viewtopic.php?p=233497#233497

Locked until the DD discussion arrives at this issue.