When using func_tracktrain on path_tracks it’s often handy to have an alternative path.

Imagine a train that is on a track, the player has to stop the train and push a button, then once back on the train it follows another set of tracks.

In this project I’ve used a Roller_Spikes.mdl parented to a func_tracktrain.
The Roller will follow a triangular path on the left side of the screen for 3 loops.
It will then switch to a triangle on the right side for three loops.
This will continue indefinitely.

This is down with 5 path_track entities with one of them acting as a track switch.

I’m using a math_counter to change the track but the very same effect can be achieved with triggers, buttons, etc.

Note: Please refer to my series of tutorials on HL2 Trains for specific information about properties for tracks and trains.

I’ve given each of the path_track entities a name that reflects their roll.
This helps as you are working on your map.

The two path_tracks on the left are named path_a1 and path_a2.
The two path_tracks on the right are named path_b1 and path_b2.
And the path_track in the center is named switch01.



The path_track switch01 is shared to create two triangular paths for the train.

Note: Your paths do not need to be triangular; they can be whatever you desire.

When the map loads the train will be moving from the start.
Each time it passes switch01 I’m adding a value to a math_counter.
When the math_counter gets to 3 it will switch the track.

These are the properties.

Class: math_counter
Name: math01
Initial value: 0
Min legal value: 0
Max legal value: 3

Outputs:
OnHitMax, switch01, ToggleAlternatePath
OnHitMax, math01, Subtract, 3, 0.50

Class: path_track
Name: switch01
Next stop target: path_a1
Branch Path: path_b1

Output: OnPass, math01, Add, 1

As you can see when the train gets to path_track switch01 an output will add the value 1 to the math_counter.

When the math_counter gets to 3 it will fire an Output to ToggleAlternatePath which will instantly change the train to the alternate path.

In this project I’ve added the Roller and a few sounds just for effect.



There’s a lot more you can do, I hope I’ve stimulated your imagination.
  The example used in this tutorial.