OK, I report a bug everyone probably already knows about but nobody bothered to complain … yet.
I also have not found it in the issue tracker.
The bug is very simple:
It is possible for vegetration to spawn under a bridge. That alone would not be a problem. But if the vegetation is high enough, it crosses the bridge, so that you have awkward cases where trees go simply through the bridge. It looks ugly. But what it much worse, it obscures the view and makes driving on an affected bridge painful. It gets even more annoying in pipes IMO.
It looks like this:
For tracks with many trees and bridges, this can be really an issue, to the point where the trees are totally blocking the view and you are almost blindly driving. The car usually does not collide with the tree when driving on a bridge. That’s at least something!
I think a simple fix might be to project the road down onto the floor and simply not spawn any vegetation on that pseudo-road, like it is done for the ordinary road already.
This would fix the bug. But it could be better IMO. And frankly, it would just replace one uglyness with another uglyness. The problem with this fix would be obviously that for very high bridges, you would get an awkward scenery on the ground, basically you can directly see the road’s projection because no tree whatsoever spawns there. Basically a “ghost road”.
A more sophisticasted fix might also take the tree height into account. So trees may spawn under a bridge, but only if the tree height is smaller than the bridge itself; probably the bridge height minus a little “buffer distance”, to be precise. This avoids those awkward-looking sceneries when the bridge is very high, like in Twister.
It could get a bit tricky for tilted roads however.
But I guess that would just mean that one has to subtract another number from the bridge height, namely half of the track width I guess. Why? That’s for the case when the road roll is exactly 90°; and the road always rolls around its center. And for 90°, half of the track width faces downwards.
So, the formula for the maximum tree (vegetation) height M under some point under a bridge might be:
M = h - 0.5*w - t
M: maximum vegetation height for that point
h: height of road at that point
w: width of road at that point
t: a small extra buffer (a constant)
This formula should always give a height so that only vegetation that comes only close to the bridge at most, but never touches or even crosses it is allowed under a bridge.
OK, with the second part of this post, this post has more become like a feature request than a pure bug report, I admit.
But the problem is still real.