Callback: Build probability

Build Probability (162)

This callback allows the game to ask for the chances of an action happening on build. (Currently the only action is reversing rail vehicles.)

Return a value between 0...100 (decimal) to indicate the probability of an action happening.

Returning 0 means the action will never happen. Returning 50 means the action will have a 50:50 chance of happening. Returning 100 means the action will always happen.

Variable 10	Meaning
0	Probability of reversing rail vehicle, i.e. facing forward or backward, when purchased*.
..	Reserved.

• The same random-reverse behaviour can be implemented without the callback, by randomly switching to reversed sprites in the vehicle's varaction 2 chain, but this is inefficient as it typically causes sprites to be duplicated in the grf.

This callback is available from 14  OpenTTD 14 and above.