XPMP2 can add contrails to planes. This is achieved by instantiating
one additional object per contrail at the same position as the actual plane.
This object Resources/Contrail/Contrail.obj has no tris,
but only holds a reference to a particle system file, Contrail.pss.
The contrail is then created through X-Plane’s
particle system.
If you don’t want contrails at all, you need to return 0 for the two config items
XPMP_CFG_ITM_CONTR_MIN_ALT and XPMP_CFG_ITM_CONTR_MAX_ALT.
In that case you don’t even need to provide the Resources/Contrail folder
with your deployment.
If you want to make use of contrails, you need to ship the
Resources/Contrail folder with all its 3 files with your plugin.
By default, ie. without any provision in code, a single contrail will be generated for jet aircraft flying in an altitude between 25,000 and 45,000 ft.
XPMP2 asks for four contrail-related configuration items, with which you can fine-tune how XPMP2 automatically generates contrails. This should be sufficient for most usages, even complex plugins like LiveTraffic only provide pass-through configuration options for these four parameters, but no self-development implementation.
| Config item | Default | Description |
|---|---|---|
XPMP_CFG_ITM_CONTR_MIN_ALT |
25000 | Minimum altitude in feet for automatic contrail generation |
XPMP_CFG_ITM_CONTR_MAX_ALT |
45000 | Maximum altitude in feet for automatic contrail generation; set both min and max altitude to 0 to switch off automatic contrails |
XPMP_CFG_ITM_CONTR_LIFE |
25 | Default maximum lifetime of contrail puffs in seconds, determines contrail length |
XPMP_CFG_ITM_CONTR_MULTI |
0 | Boolean: Shall multiple contrails be auto-created (one per engine), or just one? |
Keep in mind that contrails, using the particle system, may have the potential to affect performance. That’s why by default just a single contrail is generated.
If you need more control and want to direct yourself when how many contrails
are shown, you should switch off the auto-generation by returning 0 to
both XPMP_CFG_ITM_CONTR_MIN_ALT and XPMP_CFG_ITM_CONTR_MAX_ALT,
and then call either of the following two member functions of XPMP2::Aircraft:
ContrailTrigger() tells XPMP2 to check the plane’s engine type,
and if it is jet then a contrail (or even multiple, depending on
config XPMP_CFG_ITM_CONTR_MULTI) are created. This is the function
internally used by the auto-generation mechanism once a plane is in the
right altitude.ContrailRequest (unsigned num, unsigned dist_m = 0, unsigned lifeTime = 0)
allows even more control by specifying the number of contrails, its spacing,
and the life time.Last but not least, there’s ContrailRemove() to remove contrails.