Receipe: Tunnel

  • Here it is explained step by step how a tunnel entrance is built and besides general things about tunnel construction are explained.

    1 Starting situation

    We have here the end of a cut section at the (absolute) height of -6m, which is realized with layout elements and polygons at level 0. In particular, note the transparent polygon that roughly defines the mouth of the tunnel. Later, after completion of the tunnel, the shape can still be changed at any time to obtain the exact transition. The tunnel mouth can then, of course, be neatly shaped and decorated with the usual elements

    It should be noted, however, that the tracks laid so far (on level 0) will not be built right up to the tunnel mouth, but will initially end at a certain distance beforehand!

    The length of this track is half the length of the longest connected vehicle! If you want to be absolutely sure and design your track for all compatible vehicles, use (if possible without problems) half the length of the longest train.

    The distance between the track centers is 4m (Berlin post-war large profile).

    2 Dimensions

    Please be sure to observe the building conventions regarding dimensions at the very bottom of this article!

    3 Layer -1

    3.1 Layout element

    The first step is the construction of the underground layout elements. The first layout element is placed on level -1. When the train is on this, then natural light can continue to fall into the tunnel and the above-ground landscape is still visible. To do this, we change to level -1 using the "Underground level" control at the bottom left. It takes a while for the level change to be complete.

    Only the grid is displayed and darkened accordingly:

    Unlike the simulator, the MapEditor also hides the layer (0) immediately above the selected layer (-1) by default. This allows you to work on layer -1 in peace without layer 0 interfering.

    But we want to create the transition to layer 0, so we want to make it visible. We do this by checking the "Show next higher layer" box at the bottom left. Again, it takes a moment for the layer change to complete:

    We now see here on the one hand the terrain with the polygons of layer 0 (light graph paper). In addition, we see the terrain of layer -1 (dark graph paper, which covers the tracks, etc.). Now it is important to know that the terrains of the lower layer are not visible in the simulator! Only the polygons and terrain splines are visible, i.e. the tracks will be visible normally. As soon as you switch back to level 0 or remove the said hook, the tracks will be visible again.

    By the way, the dark terrain (level -1) is 5m lower than the light one (level 0), that of -2 is another 5m, and so on. These are arbitrarily chosen values, so that the respective terrains are not at the same height. The height is irrelevant anyway, because in tunnels, alignment elements are always used anyway.

    The first tunnel section is the one from which you can still/already see the outside world and into which sunlight falls.

    Next, we place a polygon directly on the routing element. The polygon does not have to match the routing element exactly. It is only important that the correct number is always visible at the bottom left during construction.

    Next, we place the tracks for level -1. ATTENTION: Level 1 also includes those tracks that are located before the tunnel mouth on the last meters!

    Also before placing the tracks, check again at the bottom left if the set level is correct!

    By the way, the parallel function can also be used if the reference line used as a basis lies on another plane.

    With level 0 set, the whole thing will look like this:

    You can see here very well which polygons and tracks are on which level: Light = level 0, Dark = level -1. If we then go "deeper" to the other tunnel levels, it will no longer be so easy to recognize. But then, in contrast to the tunnel mouth, the transition is also completely uncritical.

    Do not forget to set the -1 level before continuing!

    3.2 Building tunnels

    So, now we build walls and ceiling on level -1, now with the hook "Show next higher level" switched off. The supplied objects refer to the tunnel floor, i.e. the alignment element, which is 0.25m below the top of the rails when using the standard tracks. Accordingly, we work with relative height (:heightrelabs: switched on) and Z = 0.

    It should be noted in passing that the walls supplied for the Berlin large profile are 1.65m from the center of the track.

    The elements "Tunnel_Wall_Podest", "Tunnel_Ceiling_70_40" (ceiling with 7m width and 4m height above alignment element) and "Tunnel_Columns_High" were used here.

    It may also be possible to work with good lighting underground. To do this, simply uncheck the "Ambient shadows visible" box at the bottom left:

    3.3 Placing scenery objects precisely

    Of course, we can already attach a few lights (type "Tunnel_Lgt_1"); these must be attached with a relative height of 3.844m, provided they are placed between the supplied pillars of type "Tunnel_Columns_High". For precise mounting, the pillars have auxiliary polygons on the top so that you can spot them even in the 2D view:

    The procedure is now the following:

    • Select 2D view
    • Enter height of Z = 3.844
    • switch on :heightrelabs: , switch off :snapZ:
    • select the lamp in the scenery object mode
    • "New object"
    • Place the lamp as desired, if possible...
    • ...while holding down [Ctrl] to point to reference lines, tracks or routing elements.
    • If it turns out later that lamps are at the wrong height, select all affected lamps together ([Shift]+key), enter Z=3.844 again and press [Enter].

    4 Lower layers

    The construction of deeper levels is done in exactly the same way as for level -1:

    • Set visibility to -2 and turn on the checkmark for the visibility of the next higher level
    • create layout element
    • Place tracks and tunnel splines/objects

    But it is important:

    • In tunnels on level -1 - as said - sunlight can still shine, which is why shadows are still calculated there.
    • On level -2, the above-ground scenery is still loaded, but it is no longer visible in the simulator. Since reloading takes a long time, trains leaving the tunnel should also be "raised" to level -2 in good time beforehand. From this level on, (sun) shadows are no longer calculated and the number of light sources is increased to the night value.
    • If, on the other hand, the landscape can be completely unloaded, the web should run at level -3 or smaller.

    5 Sunlight/natural light in the tunnel

    As on all lower levels, also on level -1 there is basically darkness for the time being. Level 0 is - like all higher levels - basically "bright" (daylight).

    On layers 0 and -1, however, the brightness of the daylight can be influenced with the ambient segments ("Terrain" tab). These are constructed in exactly the same way as terrain segments, with the only difference that they do not influence the height, but they do influence the brightness on levels 0 and -1. It is important, however, that the construction of all ambient segments takes place in level 0!

    So far, the tunnel mouth currently looks like this:

    Now we create two Ambient segments (Terrain tab) - but they don't have to be precisely laid, on the contrary, it's even advantageous if they are a little bit off, so that you don't click on them automatically all the time. Note that the left segment has the full length of the longest vehicle (or the length of the longest platform):

    The effect is immediately visible - let's look at it again in 3D (I turned off the guides):

    You can see that soft shadowing is occurring, however there are still three errors that need to be corrected:

    1. The front part is not supposed to be dark at all; it is only on level -1 for the transition from "above" to "below".
    2. The rear part "shines" up through the ceiling
    3. the shadow is too narrow.

    All three things can be solved in the properties:

    1. At the very bottom are the specific properties: For the front segment, Start Brightness and End Brightness must be set to 1.0.
    2. For the rear segment, the check mark at "Surface level" must be removed
    3. The width can optionally be defined in the properties or by mouse in exactly the same way as for the routing elements.

    6 Done!

    Here is the end of the cookbook - we have constructed a standard tunnel mouth, as it probably fits in most cases. But you are welcome to experiment, we are curious about the screenshots! :-)

    7 Bridges

    Stop! There was something else...

    Purely by chance we have found the function with which a shadow can now be formed under bridges! Here may be tried around with pleasure! :-) So much only here: As soon as one is then on level 1 or higher, the shadow becomes then also ineffective.

    8 Tunnel construction conventions and dimensions

    Please be sure to follow the following convention to avoid chaos with future tunnel components!

    8.1 Vertical reference

    The reference elevation in tunnels is always the upper edge of the rail!

    Above ground there are usually two variants: Grooved rails are built at the height of the road surface, which is either at the level of the subgrades or lowered by the height of the curbstone (in the Basecontent -0.15). Or it is a ballast track, in which case it is not laid at the level of the terrain (the subgrades), but raised according to its height, in the case of the basecontent it is usually +0.25m.

    In underground structures, however, the subgrades are laid at the level of the rail top edge and the tracks are not laid at +0.25, but always at ±0m. Any floors/ballast areas must therefore be lowered accordingly, usually to -0.25m in the basecontent. It is important to note that when selecting the track type at the top of the MapEditor, the pre-selected height Z= is not retained but reset to 0!


    8.2 Dimensions of the Berlin tunnels

    If you want to use the supplied Berlin tunnel components and/or construct tunnels compatible with Berlin vehicles or your own vehicles, please note the following dimensions:

    Gp = Large profile

    Kp = Small profile

    New = New construction tunnel (post-war)

    Old = old tunnel (pre-war)

    Gp New Kp Old
    a Height of the tunnel ceiling above the top of the rail +4,00 (min. +3,75m) +3,4m
    b Height of ballast bedding, if the tracks are to be completely ballasted in -0,17m -0,17m
    c Depth of the tunnel floor if the track ballast bed is to be completely visible -0,25m -0,25m
    d Height of the lower edge of the support beam - +2,77m
    e Platform height +0,925m +0,8m
    m Distance of the outer wall reference point to the centre of the track 1,65m 1,5m
    n Distance from the centre of the track to the centre of the tunnel (in a normal tunnel without walkways or similar) 1,9m 1,62m
    n Distance of the track centre to the tunnel centre (with walkway, e.g. in turnarounds). [voraussichtlich 2,0m] 1,75m
    p Distance of the platform from the centre of the track 1,375m 1,2m